Surface Mass Balance of the Columbia Glacier, Alaska, 1978 and 2010 Balance Years
O'Neel, Shad
2012-01-01
Although Columbia Glacier is one of the largest sources of glacier mass loss in Alaska, surface mass balance measurements are sparse, with only a single data set available from 1978. The dearth of surface mass-balance data prohibits partitioning of the total mass losses between dynamics and surface forcing; however, the accurate inclusion of calving glaciers into predictive models requires both dynamic and climatic forcing of total mass balance. During 2010, the U.S. Geological Survey collected surface balance data at several locations distributed over the surface of Columbia Glacier to estimate the glacier-wide annual balance for balance year 2010 using the 2007 area-altitude distribution. This report also summarizes data collected in 1978, calculates the 1978 annual surface balance, and uses these observations to constrain the 2010 values, particularly the shape of the balance profile. Both years exhibit balances indicative of near-equilibrium surface mass-balance conditions, and demonstrate the importance of dynamic processes during the rapid retreat.
Mass balance assessment using GPS
NASA Technical Reports Server (NTRS)
Hulbe, Christina L.
1993-01-01
Mass balance is an integral part of any comprehensive glaciological investigation. Unfortunately, it is hard to determine at remote locations where there is no fixed reference. The Global Positioning System (GPS) offers a solution. Simultaneous GPS observations at a known location and the remote field site, processed differentially, will accurately position the camp site. From there, a monument planted in the firn atop the ice can also be accurately positioned. Change in the monument's vertical position is a direct indicator of ice thickness change. Because the monument is not connected to the ice, its motion is due to both mass balance change and to the settling of firn as it densifies into ice. Observations of relative position change between the monument and anchors at various depths within the firn are used to remove the settling effect. An experiment to test this method has begun at Byrd Station on the West Antarctic Ice Sheet and the first epoch of observations was made. Analysis indicates that positioning errors will be very small. It appears likely that the largest errors involved with this technique will arise from ancillary data needed to determine firn settling.
Remote Sensing Estimates of Glacier Mass Balance Changes in the Himalayas of Nepal
NASA Astrophysics Data System (ADS)
Ambinakudige, S.; Joshi, K.
2011-12-01
Mass balance changes of glaciers are important indicators of climate change. There are only 30 'reference' glaciers in the world that have continuous mass balance data with world glacier monitoring service since 1976. Especially, Himalayan glaciers are conspicuously absent from global mass balance records. This shows the urgent need for mass balance data for glaciers throughout the world. In this study, we estimated mass balance of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. The SNP is one of the densest glaciated regions in the Himalayan range consisting approximately 296 glacial lakes. The region has experienced several glacial lake outburst floods (GLOFs) in recent years, causing extensive damage to local infrastructure and loss of human life. In general, mass balance is determined at seasonal or yearly intervals. Because of the rugged and difficult terrain of the Himalayan region, there are only a few field based measurements of mass balance available. Moreover, there are only few cases where the applications of remote sensing methods were used to calculate mass balance of the Himalayan glaciers due to the lack of accurate elevation data. Studies have shown that estimations of mass balance using remote sensing applications were within the range of field-based mass balance measurements from the same period. This study used ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area. 3N and 3B bands generate an along track stereo pair with a base-to-height (B/H) ratio of about 0.6. Accurate measurement of ground control points (GCPs), their numbers and distribution are important inputs in creating accurate DEMs. Because of the availability of topographic maps for this area, we were able to provide very accurate GCPs, in sufficient numbers and distribution. We created DEMs for the years 2002, 2003, 2004 and 2005 using ENVI DEM extraction tool. Bands
Energy balance and mass conservation in reduced order models of fluid flows
NASA Astrophysics Data System (ADS)
Mohebujjaman, Muhammad; Rebholz, Leo G.; Xie, Xuping; Iliescu, Traian
2017-10-01
In this paper, we investigate theoretically and computationally the conservation properties of reduced order models (ROMs) for fluid flows. Specifically, we investigate whether the ROMs satisfy the same (or similar) energy balance and mass conservation as those satisfied by the Navier-Stokes equations. All of our theoretical findings are illustrated and tested in numerical simulations of a 2D flow past a circular cylinder at a Reynolds number Re = 100. First, we investigate the ROM energy balance. We show that using the snapshot average for the centering trajectory (which is a popular treatment of nonhomogeneous boundary conditions in ROMs) yields an incorrect energy balance. Then, we propose a new approach, in which we replace the snapshot average with the Stokes extension. Theoretically, the Stokes extension produces an accurate energy balance. Numerically, the Stokes extension yields more accurate results than the standard snapshot average, especially for longer time intervals. Our second contribution centers around ROM mass conservation. We consider ROMs created using two types of finite elements: the standard Taylor-Hood (TH) element, which satisfies the mass conservation weakly, and the Scott-Vogelius (SV) element, which satisfies the mass conservation pointwise. Theoretically, the error estimates for the SV-ROM are sharper than those for the TH-ROM. Numerically, the SV-ROM yields significantly more accurate results, especially for coarser meshes and longer time intervals.
An Analysis of Mass Balance of Chilean Glaciers
NASA Astrophysics Data System (ADS)
Ambinakudige, S.; Tetteh, L.
2013-12-01
Glaciers in Chile range from very small glacierets found on the isolated volcanoes of northern Chile to the 13,000 sq.km Southern Patagonian Ice Field. Regular monitoring of these glaciers is very important as they are considered as sensitive indicators of climate change. Millions of people's lives are dependent on these glaciers for fresh water and irrigation purpose. In this study, mass balances of several Chilean glaciers were estimated using Aster satellite images between 2007 and 2012. Highly accurate DEMs were created with supplementary information from IceSat data. The result indicated a negative mass balance for many glaciers indicating the need for further monitoring of glaciers in the Andes.
NASA Astrophysics Data System (ADS)
Bonin, J. A.; Chambers, D. P.
2015-09-01
Mass change over Greenland can be caused by either changes in the glacial dynamic mass balance (DMB) or the surface mass balance (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire mass column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate cumulative SMB from DMB with GRACE, using a least squares inversion technique with knowledge of the location of the glaciers. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from DMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 10 at a resolution of 90 × 90 would provide the accuracy needed for the interannual cumulative SMB and DMB to be accurately separated.
NASA Astrophysics Data System (ADS)
Bonin, J. A.; Chambers, D. P.
2015-02-01
Mass change over Greenland can be caused by either changes in the glacial mass balance (GMB) or the precipitation-based surface mass balance (SMB). The GRACE satellite gravity mission cannot directly separate the two physical causes because it measures the sum of the entire mass column with limited spatial resolution. We demonstrate one theoretical way to indirectly separate SMB from GMB with GRACE, using a least squares inversion technique with knowledge of the location of the glacier. However, we find that the limited 60 × 60 spherical harmonic representation of current GRACE data does not provide sufficient resolution to adequately accomplish the task. We determine that at a maximum degree/order of 90 × 90 or above, a noise-free gravity measurement could theoretically separate the SMB from GMB signals. However, current GRACE satellite errors are too large at present to separate the signals. A noise reduction of a factor of 9 at a resolution of 90 × 90 would provide the accuracy needed for the interannual SMB and GMB to be accurately separated.
Invited article: Time accurate mass flow measurements of solid-fueled systems.
Olliges, Jordan D; Lilly, Taylor C; Joslyn, Thomas B; Ketsdever, Andrew D
2008-10-01
A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.
Invited Article: Time accurate mass flow measurements of solid-fueled systems
NASA Astrophysics Data System (ADS)
Olliges, Jordan D.; Lilly, Taylor C.; Joslyn, Thomas B.; Ketsdever, Andrew D.
2008-10-01
A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.
Greenland Ice Sheet Mass Balance
NASA Technical Reports Server (NTRS)
Reeh, N.
1984-01-01
Mass balance equation for glaciers; areal distribution and ice volumes; estimates of actual mass balance; loss by calving of icebergs; hydrological budget for Greenland; and temporal variations of Greenland mass balance are examined.
Antarctic mass balance changes from GRACE
NASA Astrophysics Data System (ADS)
Kallenberg, B.; Tregoning, P.
2012-04-01
The Antarctic ice sheet contains ~30 million km3 of ice and constitutes a significant component of the global water balance with enough freshwater to raise global sea level by ~60 m. Altimetry measurements and climate models suggest variable behaviour across the Antarctic ice sheet, with thickening occurring in a vast area of East Antarctica and substantial thinning in West Antarctica caused by increased temperature gradients in the surrounding ocean. However, the rate at which the polar ice cap is melting is still poorly constrained. To calculate the mass loss of an ice sheet it is necessary to separate present day mass balance changes from glacial isostatic adjustment (GIA), the response of the Earth's crust to mass loss, wherefore it is essential to undertake sufficient geological and geomorphological sampling. As there is only a limited possibility for this in Antarctica, all models (i.e. geological, hydrological as well as atmospheric) are very poorly constrained. Therefore, space-geodetic observations play an important role in detecting changes in mass and spatial variations in the Earth's gravity field. The Gravity Recovery And Climate Experiment (GRACE) observed spatial variations in the Earth's gravity field over the past ten years. The satellite detects mass variations in the Earth system including geophysical, hydrological and atmospheric shifts. GRACE itself is not able to separate the GIA from mass balance changes and, due to the insufficient geological and geomorphological database, it is not possible to model the GIA effect accurately for Antarctica. However, the results from GRACE can be compared with other scientific results, coming from other geodetic observations such as satellite altimetry and GPS or by the use of geological observations. In our contribution we compare the GRACE data with recorded precipitation patterns and mass anomalies over East Antarctica to separate the observed GRACE signal into its two components: GIA as a result of mass
Remote balance weighs accurately amid high radiation
NASA Technical Reports Server (NTRS)
Eggenberger, D. N.; Shuck, A. B.
1969-01-01
Commercial beam-type balance, modified and outfitted with electronic controls and digital readout, can be remotely controlled for use in high radiation environments. This allows accurate weighing of breeder-reactor fuel pieces when they are radioactively hot.
Miniature Piezoelectric Macro-Mass Balance
NASA Technical Reports Server (NTRS)
Sherrit, Stewart; Trebi-Ollennu, Ashitey; Bonitz, Robert G.; Bar-Cohen, Yoseph
2010-01-01
Mass balances usually use a strain gauge that requires an impedance measurement and is susceptible to noise and thermal drift. A piezoelectric balance can be used to measure mass directly by monitoring the voltage developed across the piezoelectric balance, which is linear with weight or it can be used in resonance to produce a frequency change proportional to the mass change (see figure). The piezoelectric actuator/balance is swept in frequency through its fundamental resonance. If a small mass is added to the balance, the resonance frequency shifts down in proportion to the mass. By monitoring the frequency shift, the mass can be determined. This design allows for two independent measurements of mass. Additionally, more than one sample can be verified because this invention allows for each sample to be transported away from the measuring device upon completion of the measurement, if required. A piezoelectric actuator, or many piezoelectric actuators, was placed between the collection plate of the sampling system and the support structure. As the sample mass is added to the plate, the piezoelectrics are stressed, causing them to produce a voltage that is proportional to the mass and acceleration. In addition, a change in mass delta m produces a change in the resonance frequency with delta f proportional to delta m. In a microgravity environment, the spacecraft could be accelerated to produce a force on the piezoelectric actuator that would produce a voltage proportional to the mass and acceleration. Alternatively, the acceleration could be used to force the mass on the plate, and the inertial effects of the mass on the plate would produce a shift in the resonance frequency with the change in frequency related to the mass change. Three prototypes of the mass balance mechanism were developed. These macro-mass balances each consist of a solid base and an APA 60 Cedrat flextensional piezoelectric actuator supporting a measuring plate. A similar structure with 3 APA
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass balance...
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Mass balance. 23.659 Section 23.659 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Surfaces § 23.659 Mass balance. The supporting structure and the attachment of concentrated mass balance...
Mass balance computation in SAGUARO
DOE Office of Scientific and Technical Information (OSTI.GOV)
Baker, B.L.; Eaton, R.R.
1986-12-01
This report describes the development of the mass balance subroutines used with the finite-element code, SAGUARO, which models fluid flow in partially saturated porous media. Derivation of the basic mass storage and mass flux equations is included. The results of the SAGUARO mass-balance subroutine, MASS, are shown to compare favorably with the linked results of FEMTRAN. Implementation of the MASS option in SAGUARO is described. Instructions for use of the MASS option are demonstrated with the three sample cases.
Mass balancing of hollow fan blades
NASA Technical Reports Server (NTRS)
Kielb, R. E.
1986-01-01
A typical section model is used to analytically investigate the effect of mass balancing as applied to hollow, supersonic fan blades. A procedure to determine the best configuration of an internal balancing mass to provide flutter alleviation is developed. This procedure is applied to a typical supersonic shroudless fan blade which is unstable in both the solid configuration and when it is hollow with no balancing mass. The addition of an optimized balancing mass is shown to stabilize the blade at the design condition.
Code of Federal Regulations, 2014 CFR
2014-01-01
... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor and blades must be mass balanced as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Mass balance. 29.659 Section 29.659...
Code of Federal Regulations, 2014 CFR
2014-01-01
... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors and blades must be mass balanced as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Mass balance. 27.659 Section 27.659...
Code of Federal Regulations, 2012 CFR
2012-01-01
... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor and blades must be mass balanced as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Mass balance. 29.659 Section 29.659...
Code of Federal Regulations, 2013 CFR
2013-01-01
... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors and blades must be mass balanced as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Mass balance. 27.659 Section 27.659...
Code of Federal Regulations, 2012 CFR
2012-01-01
... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors and blades must be mass balanced as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Mass balance. 27.659 Section 27.659...
Code of Federal Regulations, 2013 CFR
2013-01-01
... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor and blades must be mass balanced as necessary to— (1) Prevent excessive vibration; and (2) Prevent... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Mass balance. 29.659 Section 29.659...
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass balance...
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass balance...
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Mass balance. 27.659 Section 27.659... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.659 Mass balance. (a) The rotors... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass balance...
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Mass balance. 29.659 Section 29.659... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.659 Mass balance. (a) The rotor... flutter at any speed up to the maximum forward speed. (b) The structural integrity of the mass balance...
A new approach to enforce element-wise mass/species balance using the augmented Lagrangian method
NASA Astrophysics Data System (ADS)
Chang, J.; Nakshatrala, K.
2015-12-01
The least-squares finite element method (LSFEM) is one of many ways in which one can discretize and express a set of first ordered partial differential equations as a mixed formulation. However, the standard LSFEM is not locally conservative by design. The absence of this physical property can have serious implications in the numerical simulation of subsurface flow and transport. Two commonly employed ways to circumvent this issue is through the Lagrange multiplier method, which explicitly satisfies the element-wise divergence by introducing new unknowns, or through appending a penalty factor to the continuity constraint, which reduces the violation in the mass balance. However, these methodologies have some well-known drawbacks. Herein, we propose a new approach to improve the local balance of species/mass balance. The approach augments constraints to a least-square function by a novel mathematical construction of the local species/mass balance, which is different from the conventional ways. The resulting constrained optimization problem is solved using the augmented Lagrangian, which corrects the balance errors in an iterative fashion. The advantages of this methodology are that the problem size is not increased (thus preserving the symmetry and positive definite-ness) and that one need not provide an accurate guess for the initial penalty to reach a prescribed mass balance tolerance. We derive the least-squares weighting needed to ensure accurate solutions. We also demonstrate the robustness of the weighted LSFEM coupled with the augmented Lagrangian by solving large-scale heterogenous and variably saturated flow through porous media problems. The performance of the iterative solvers with respect to various user-defined augmented Lagrangian parameters will be documented.
Accurate mass measurement: terminology and treatment of data.
Brenton, A Gareth; Godfrey, A Ruth
2010-11-01
High-resolution mass spectrometry has become ever more accessible with improvements in instrumentation, such as modern FT-ICR and Orbitrap mass spectrometers. This has resulted in an increase in the number of articles submitted for publication quoting accurate mass data. There is a plethora of terms related to accurate mass analysis that are in current usage, many employed incorrectly or inconsistently. This article is based on a set of notes prepared by the authors for research students and staff in our laboratories as a guide to the correct terminology and basic statistical procedures to apply in relation to mass measurement, particularly for accurate mass measurement. It elaborates on the editorial by Gross in 1994 regarding the use of accurate masses for structure confirmation. We have presented and defined the main terms in use with reference to the International Union of Pure and Applied Chemistry (IUPAC) recommendations for nomenclature and symbolism for mass spectrometry. The correct use of statistics and treatment of data is illustrated as a guide to new and existing mass spectrometry users with a series of examples as well as statistical methods to compare different experimental methods and datasets. Copyright © 2010. Published by Elsevier Inc.
Influence of Persistent Wind Scour on the Surface Mass Balance of Antarctica
NASA Technical Reports Server (NTRS)
Das, Indrani; Bell, Robin E.; Scambos, Ted A.; Wolovick, Michael; Creyts, Timothy T.; Studinger, Michael; Fearson, Nicholas; Nicolas, Julien P.; Lenaerts, Jan T. M.; vandenBroeke, Michiel R.
2013-01-01
Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-core records. Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (< or = 200 sq km) with reduced surface accumulation. Estimates of Antarctic surface mass balance rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net mass input in wind-scour zones. Here we combine airborne radar observations of unconformable stratigraphic layers with lidar-derived surface roughness measurements to identify extensive wind-scour zones over Dome A, in the interior of East Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that approx. 2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow mass input is overestimated by 11-36.5 Gt /yr in present surface-mass-balance calculations.
Representativeness of regional and global mass-balance measurement networks (Invited)
NASA Astrophysics Data System (ADS)
Cogley, J. G.; Moholdt, G.; Gardner, A. S.
2013-12-01
We showed in a recent publication that regional estimates of glacier mass budgets, obtained by interpolation from in-situ measurements, were markedly more negative than corresponding estimates by satellite gravimetry (GRACE) and satellite altimetry (ICESat) during 2003-2009. Examining the ICESat data in more detail, we found that in-situ records tend to be located in areas where glaciers are thinning more rapidly than as observed in their regional surroundings. Because neither GRACE nor ICESat can provide information for times before 2002-2003, and may not operate without interruption in the future, we explore possible explanations of and remedies for the identified bias in the in-situ network. Sparse spatial sampling, coupled with previously undetected spatial variability of mass balance at scales between the 10-km in-situ scale and the 350-km gravimetric scale, appears to be the leading explanation. Satisfactory remedies are not obvious. Selecting glaciers for in-situ measurement that are more representative will yield only incremental improvements. There appears to be no alternative to mass-balance modelling as a versatile tool for estimation of regional mass balance. However the meteorological data for forcing the surface components of glacier models have coarser resolution than is desirable and are themselves uncertain, especially in the remote regions where much of the glacier ice is found. Measurements of frontal (dynamic) mass changes are still difficult, and modelling of these changes remains underdeveloped in spite of recent advances. Thus research on a broad scale is called for in order to meet the challenge of producing more accurate hindcasts and projections of glacier mass budgets with fine spatial and temporal resolution.
Surface melt dominates Alaska glacier mass balance
Larsen Chris F,; Burgess, E; Arendt, A.A.; O'Neel, Shad; Johnson, A.J.; Kienholz, C.
2015-01-01
Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial ice, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional mass balance assessments are challenging over large glacier populations due to remote and rugged geography, variable response of individual glaciers to climate change, and episodic calving losses from tidewater glaciers. In Alaska, we use airborne altimetry from 116 glaciers to estimate a regional mass balance of −75 ± 11 Gt yr−1 (1994–2013). Our glacier sample is spatially well distributed, yet pervasive variability in mass balances obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional mass balance by glacier type. We find that tidewater glaciers are losing mass at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional mass loss.
NASA Astrophysics Data System (ADS)
Pelto, M. S.
2017-12-01
Alpine glacier mass balance is the most accurate indicator of glacier response to climate and with retreat of alpine glaciers is one of the clearest signals of global climate change. Completion of long term, representative and homogenous mass balance field measurement of mass balance, compiled by WGMS, is a key climate data record. To ensure a monitoring program remains vital and funded local collaboration and connecting the research to local societal impacts is crucial. Working with local partners in collecting and providing the right data is critical whether their interest is in hydropower, irrigation, municipal supply, hazard reduction and/or aquatic ecosystems. The expansion of remote sensing and modeling capability provides both a challenge to continued relevance and an opportunity for field mass balance programs to expand relevance. In modelling studies of both glacier mass balance and glacier runoff transient balance data has equivalent value with annual balance data, for both calibration runs and as an input variable. This increases the utility of mid-season field observations. Remote sensing provides repeat imagery that often identifies the AAR and transient snowline of a glacier. For runoff assessment understanding the specific percent of glacier surface area that is glacier ice, older firn, and retained snowpack from the previous winter at frequent intervals during the melt season is vital since each region has a different melt factor. A denser field observation network combined with this imagery can provide additional point balance values of ablation that complement the mass balance record. Periodic measurement of mass balance at a denser network using GPR, LIDAR, TLS or probing is required to better understand long term point balance locations and is important at end of the melt season not just beginning, and has value mid-season for modelling. Applications of each of utility of field mass balance observations will be illustrated.
Lake Michigan Mass Balance Project (LMMBP) was initiated to directly support the development of a lakewide management plan (LaMP) for Lake Michigan. A mass balance modeling approach is proposed for the project to addrss the realtionship between sources of toxic chemicals and thei...
Comparison of geodetic and glaciological mass-balance techniques, Gulkana Glacier, Alaska, U.S.A
Cox, L.H.; March, R.S.
2004-01-01
The net mass balance on Gulkana Glacier, Alaska, U.S.A., has been measured since 1966 by the glaciological method, in which seasonal balances are measured at three index sites and extrapolated over large areas of the glacier. Systematic errors can accumulate linearly with time in this method. Therefore, the geodetic balance, in which errors are less time-dependent, was calculated for comparison with the glaciological method. Digital elevation models of the glacier in 1974, 1993 and 1999 were prepared using aerial photographs, and geodetic balances were computed, giving - 6.0??0.7 m w.e. from 1974 to 1993 and - 11.8??0.7 m w.e. from 1974 to 1999. These balances are compared with the glaciological balances over the same intervals, which were - 5.8??0.9 and -11.2??1.0 m w.e. respectively; both balances show that the thinning rate tripled in the 1990s. These cumulative balances differ by <6%. For this close agreement, the glaciologically measured mass balance of Gulkana Glacier must be largely free of systematic errors and be based on a time-variable area-altitude distribution, and the photography used in the geodetic method must have enough contrast to enable accurate photogrammetry.
NASA Astrophysics Data System (ADS)
Saslow, Wayne M.
2014-04-01
Three common approaches to F→=ma→ are: (1) as an exactly true definition of force F→ in terms of measured inertial mass m and measured acceleration a→; (2) as an exactly true axiom relating measured values of a→, F→ and m; and (3) as an imperfect but accurately true physical law relating measured a→ to measured F→, with m an experimentally determined, matter-dependent constant, in the spirit of the resistance R in Ohm's law. In the third case, the natural units are those of a→ and F→, where a→ is normally specified using distance and time as standard units, and F→ from a spring scale as a standard unit; thus mass units are derived from force, distance, and time units such as newtons, meters, and seconds. The present work develops the third approach when one includes a second physical law (again, imperfect but accurate)—that balance-scale weight W is proportional to m—and the fact that balance-scale measurements of relative weight are more accurate than those of absolute force. When distance and time also are more accurately measurable than absolute force, this second physical law permits a shift to standards of mass, distance, and time units, such as kilograms, meters, and seconds, with the unit of force—the newton—a derived unit. However, were force and distance more accurately measurable than time (e.g., time measured with an hourglass), this second physical law would permit a shift to standards of force, mass, and distance units such as newtons, kilograms, and meters, with the unit of time—the second—a derived unit. Therefore, the choice of the most accurate standard units depends both on what is most accurately measurable and on the accuracy of physical law.
Trends in ice sheet mass balance, 1992 to 2017
NASA Astrophysics Data System (ADS)
Shepherd, A.; Ivins, E. R.; Smith, B.; Velicogna, I.; Whitehouse, P. L.; Rignot, E. J.; van den Broeke, M. R.; Briggs, K.; Hogg, A.; Krinner, G.; Joughin, I. R.; Nowicki, S.; Payne, A. J.; Scambos, T.; Schlegel, N.; Moyano, G.; Konrad, H.
2017-12-01
The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a community effort, jointly supported by ESA and NASA, that aims to provide a consensus estimate of ice sheet mass balance from satellite gravimetry, altimetry and mass budget assessments, on an annual basis. The project has five experiment groups, one for each of the satellite techniques and two others to analyse surface mass balance (SMB) and glacial isostatic adjustment (GIA). The basic premise for the exercise is that individual ice sheet mass balance datasets are generated by project participants using common spatial and temporal domains to allow meaningful inter-comparison, and this controlled comparison in turn supports aggregation of the individual datasets over their full period. Participation is open to the full community, and the quality and consistency of submissions is regulated through a series of data standards and documentation requirements. The second phase of IMBIE commenced in 2015, with participant data submitted in 2016 and a combined estimate due for public release in 2017. Data from 48 participant groups were submitted to one of the three satellite mass balance technique groups or to the ancillary dataset groups. The individual mass balance estimates and ancillary datasets have been compared and combined within the respective groups. Following this, estimates of ice sheet mass balance derived from the individual techniques were then compared and combined. The result is single estimates of ice sheet mass balance for Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula. The participants, methodology and results of the exercise will be presented in this paper.
Microbalance accurately measures extremely small masses
NASA Technical Reports Server (NTRS)
Patashnick, H.
1970-01-01
Oscillating fiber microbalance has a vibrating quartz fiber as balance arm to hold the mass to be weighed. Increasing fiber weight decreases its resonant frequency. Scaler and timer measure magnitude of the shift. This instrument withstands considerable physical abuse and has calibration stability at normal room temperatures.
Dynamical adjustment of Scandinavian glacier mass-balance time series
NASA Astrophysics Data System (ADS)
Bonan, D.; Christian, J. E.; Christianson, K. A.
2017-12-01
Glacier mass wastage is often cited as one of the most visible manifestations of anthropogenic climate change. Annual glacier mass-balance is related to local climate and atmospheric circulation, as it is defined as the yearly sum of accumulation and ablation—processes that are strongly influenced by year-to-year fluctuations in precipitation and temperature. Glacier response to a climatic trend can, however, be masked by internal variability in atmospheric circulation, and by non-climatic factors (such as topographic control, wind deposition, and incident solar radiation). Thus, unambiguous attribution of a negative glacier mass-balance trend to anthropogenic forcing remains challenging. Maritime glacier mass-balance records may be especially difficult to interpret due to the high winter balances from decadal-scale climate oscillations and the relatively short time series. Here we examine the influence of climate and atmospheric circulation variability on 14 Norwegian glaciers that span 20° of latitude, from southern Norway to Svalbard. We use dynamical adjustment—a statistical method based on partial least squares regression—to identify the components of variability within the mass-balance records that are associated with the time-varying sea level pressure (SLP) and sea surface temperature (SST) fields. We find that 30-50% of the variance in the winter mass-balance records of the glaciers in southern Norway is explained by using sea level pressure as a predictor. The leading SLP predictor pattern mimics the spatial signature of the North Atlantic Oscillation (NAO), indicating that winter balance is strongly influenced by the NAO. Moreover, the adjusted mass-balance records indicate a geographic trend: the southern Norwegian glaciers have significant negative trends in the summer balance that remain negative after adjustment, while the more northern glaciers have negative winter balance trends that only become significant after adjustment. We look into
Meta-Analysis of Mass Balances Examining Chemical Fate during Wastewater Treatment
2008-01-01
Mass balances are an instructive means for investigating the fate of chemicals during wastewater treatment. In addition to the aqueous-phase removal efficiency (Φ), they can inform on chemical partitioning, transformation, and persistence, as well as on the chemical loading to streams and soils receiving, respectively, treated effluent and digested sewage sludge (biosolids). Release rates computed on a per-capita basis can serve to extrapolate findings to a larger scale. This review examines over a dozen mass balances conducted for various organic wastewater contaminants, including prescription drugs, estrogens, fragrances, antimicrobials, and surfactants of differing sorption potential (hydrophobicity), here expressed as the 1-octanol−water partition coefficient (KOW) and the organic carbon normalized sorption coefficient (KOC). Major challenges to mass balances are the collection of representative samples and accurate quantification of chemicals in sludge. A meta-analysis of peer-reviewed data identified sorption potential as the principal determinant governing chemical persistence in biosolids. Occurrence data for organic wastewater compounds detected in digested sludge followed a simple nonlinear model that required only KOW or KOC as the input and yielded a correlation coefficient of 0.9 in both instances. The model predicted persistence in biosolids for the majority (>50%) of the input load of organic wastewater compounds featuring a log10KOW value of greater than 5.2 (log10KOC > 4.4). In contrast, hydrophobicity had no or only limited value for estimating, respectively, Φ and the overall persistence of a chemical during conventional wastewater treatment. PMID:18800497
Micromechanical Oscillating Mass Balance
NASA Technical Reports Server (NTRS)
Altemir, David A. (Inventor)
1997-01-01
A micromechanical oscillating mass balance and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers. The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.
NASA Astrophysics Data System (ADS)
Cooper, Matthew; Martin, Randall V.; Padmanabhan, Akhila; Henze, Daven K.
2017-04-01
Satellite observations offer information applicable to top-down constraints on emission inventories through inverse modeling. Here we compare two methods of inverse modeling for emissions of nitrogen oxides (NOx) from nitrogen dioxide (NO2) columns using the GEOS-Chem chemical transport model and its adjoint. We treat the adjoint-based 4D-Var modeling approach for estimating top-down emissions as a benchmark against which to evaluate variations on the mass balance method. We use synthetic NO2 columns generated from known NOx emissions to serve as "truth." We find that error in mass balance inversions can be reduced by up to a factor of 2 with an iterative process that uses finite difference calculations of the local sensitivity of NO2 columns to a change in emissions. In a simplified experiment to recover local emission perturbations, horizontal smearing effects due to NOx transport are better resolved by the adjoint approach than by mass balance. For more complex emission changes, or at finer resolution, the iterative finite difference mass balance and adjoint methods produce similar global top-down inventories when inverting hourly synthetic observations, both reducing the a priori error by factors of 3-4. Inversions of simulated satellite observations from low Earth and geostationary orbits also indicate that both the mass balance and adjoint inversions produce similar results, reducing a priori error by a factor of 3. As the iterative finite difference mass balance method provides similar accuracy as the adjoint method, it offers the prospect of accurately estimating top-down NOx emissions using models that do not have an adjoint.
Do we need long term terrestrial glacier mass balance monitoring for the future?
NASA Astrophysics Data System (ADS)
Slupetzky, H.
2003-04-01
Beginning with the International Geophysical Year 1958 and followed by other initiatives for world wide glacier observations such as the International Hydrological Decade, a distinctive increase of glacier research such as mass balance measurements was initiated. Some of the long term observations are not interrupted since then. However, because of various problems more and more of the long term series had to be given up. Is it possible to fully switch to air- and spaceborne techniques for glacier monitoring? For the mass balance series (and others glaciological series) we have by far not reached the length of meteorological records. There is an increasing need of longlasting observations for modelling and validation of remote-sensing of snow and ice. On Stubacher Sonnblick Kees, a small slope glacier (1,5 km2), in the Eastern Alps, Hohe Tauern, Province of Salzburg, a mass balance program is carried out. The mass balance has been measured for 39 years, with some extrapolations back to 1959, providing a record of 44 years. The glacier lost 12 Mio.m3 from 1964 to 2002, but had a period of mass gain between 1965 and 1981 of 9,8 Mio m3; since 1982 20,5 Mio m3 were lost. On another small glacier in the same area, the Oedenwinkel Kees, the mass gain period and the reaction of the glacier has been surveyed annualy showing a "kinematic wave". Some comperative measurements have been done on the Cathedral Massif Glacier, B.C., Canada 1977 to 1979 and 1998 and by using data from Storglaciaeren, Sweden, to evaluate the AAR ratio to estimate the net mas balances. There are some substantial reasons to carry on with direct mass balance measurements and not to interrupt or even abandon long series. There has been a great effort to sustain long term series. There is a great demand for new international initiatives to ensure the continuation of the world wide terrestrial glacier monitoring net. On Stubacher Sonnblickkees, it can be expected that the glacier will disappear within
Asia High Mountain Glacier Mass Balance
NASA Astrophysics Data System (ADS)
Shum, C. K.; Su, X.; Shang, K.; Cogley, J. G.; Zhang, G.; Howat, I. M.; Braun, A.; Kuo, C. Y.
2015-12-01
The Asian High Mountain encompassing the Qinghai-Tibetan Plateau has the largest glaciated regions in the world outside of Greenland and Antarctica. The Tibetan Plateau is the source or headwater of many major river systems, which provide water resources to more than a billion people downstream. The impact of climate change on the Tibetan Plateau physical processes, including mountain glacier wastage, permafrost active layer thickening, the timing and the quantity of the perennial snowpack melt affecting upstream catchments, river runoffs, land-use, have significant effects on downstream water resources. Exact quantification of the Asian High Mountain glacier wastage or its mass balance on how much of the melt water contributes to early 21st century global sea-level rise, remain illusive or the published results are arguably controversial. The recent observed significant increase of freshwater storage within the Tibetan Plateaus remains a limitation to exactly quantify mountain glacier wastage. Here, we provide an updated estimate of Asia high mountain glacier mass balance using satellite geodetic observations during the last decade, accounting for the hydrologic and other processes, and validated against available in situ mass balance data.
Assessing streamflow sensitivity to variations in glacier mass balance
O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis
2014-01-01
The purpose of this paper is to evaluate relationships among seasonal and annual glacier mass balances, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier mass balance and streamflow datasets from the United States Geological Survey (USGS) Alaska Benchmark Glacier Program to compare and contrast glacier-streamflow interactions in a maritime climate (Wolverine Glacier) with those in a continental climate (Gulkana Glacier). Our overall goal is to improve our understanding of how glacier mass balance processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.
Evapotranspiration: Mass balance measurements compared with flux estimation methods
USDA-ARS?s Scientific Manuscript database
Evapotranspiration (ET) may be measured by mass balance methods and estimated by flux sensing methods. The mass balance methods are typically restricted in terms of the area that can be represented (e.g., surface area of weighing lysimeter (LYS) or equivalent representative area of neutron probe (NP...
Antarctic Ice Mass Balance from GRACE
NASA Astrophysics Data System (ADS)
Boening, C.; Firing, Y. L.; Wiese, D. N.; Watkins, M. M.; Schlegel, N.; Larour, E. Y.
2014-12-01
The Antarctic ice mass balance and rates of change of ice mass over the past decade are analyzed based on observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, in the form of JPL RL05M mascon solutions. Surface mass balance (SMB) fluxes from ERA-Interim and other atmospheric reanalyses successfully account for the seasonal GRACE-measured mass variability, and explain 70-80% of the continent-wide mass variance at interannual time scales. Trends in the residual (GRACE mass - SMB accumulation) mass time series in different Antarctic drainage basins are consistent with time-mean ice discharge rates based on radar-derived ice velocities and thicknesses. GRACE also resolves accelerations in regional ice mass change rates, including increasing rates of mass gain in East Antarctica and accelerating ice mass loss in West Antarctica. The observed East Antarctic mass gain is only partially explained by anomalously large SMB events in the second half of the record, potentially implying that ice discharge rates are also decreasing in this region. Most of the increasing mass loss rate in West Antarctica, meanwhile, is explained by decreasing SMB (principally precipitation) over this time period, part of the characteristic decadal variability in regional SMB. The residual acceleration of 2+/-1 Gt/yr, which is concentrated in the Amundsen Sea Embayment (ASE) basins, represents the contribution from increasing ice discharge rates. An Ice Sheet System Model (ISSM) run with constant ocean forcing and stationary grounding lines both underpredicts the largest trends in the ASE and produces negligible acceleration or interannual variability in discharge, highlighting the potential importance of ocean forcing for setting ice discharge rates at interannual to decadal time scales.
Considerations affecting the additional weight required in mass balance of ailerons
NASA Technical Reports Server (NTRS)
Diehl, W S
1937-01-01
This paper is essentially a consideration of mass balance of ailerons from a preliminary design standpoint, in which the extra weight of the mass counterbalance is the most important phase of the problem. Equations are developed for the required balance weight for a simple aileron and this weight is correlated with the mass-balance coefficient. It is concluded the location of the c.g. of the basic aileron is of paramount importance and that complete mass balance imposes no great weight penalty if the aileron is designed to have its c.g. inherently near to the hinge axis.
Mass-balance measurements in Alaska and suggestions for simplified observation programs
Trabant, D.C.; March, R.S.
1999-01-01
US Geological Survey glacier fieldwork in Alaska includes repetitious measurements, corrections for leaning or bending stakes, an ability to reliably measure seasonal snow as deep as 10 m, absolute identification of summer surfaces in the accumulation area, and annual evaluation of internal accumulation, internal ablation, and glacier-thickness changes. Prescribed field measurement and note-taking techniques help eliminate field errors and expedite the interpretative process. In the office, field notes are transferred to computerized spread-sheets for analysis, release on the World Wide Web, and archival storage. The spreadsheets have error traps to help eliminate note-taking and transcription errors. Rigorous error analysis ends when mass-balance measurements are extrapolated and integrated with area to determine glacier and basin mass balances. Unassessable errors in the glacier and basin mass-balance data reduce the value of the data set for correlations with climate change indices. The minimum glacier mass-balance program has at least three measurement sites on a glacier and the measurements must include the seasonal components of mass balance as well as the annual balance.
Remote Sensing of Cryosphere: Estimation of Mass Balance Change in Himalayan Glaciers
NASA Astrophysics Data System (ADS)
Ambinakudige, Shrinidhi; Joshi, Kabindra
2012-07-01
Glacial changes are an important indicator of climate change. Our understanding mass balance change in Himalayan glaciers is limited. This study estimates mass balance of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. Remote sensing technique to measure mass balance of glaciers is an important methodological advance in the highly rugged Himalayan terrain. This study uses ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area for the years 2002, 2003, 2004 and 2005. Glacier boundaries were delineated using combination of boundaries available in the Global land ice measurement (GLIMS) database and various band ratios derived from ASTER images. Elevation differences, glacial area, and ice densities were used to estimate the change in mass balance. The results indicated that the rate of glacier mass balance change was not uniform across glaciers. While there was a decrease in mass balance of some glaciers, some showed increase. This paper discusses how each glacier in the SNP area varied in its annual mass balance measurement during the study period.
Using an SLR inversion to measure the mass balance of Greenland before and during GRACE
NASA Astrophysics Data System (ADS)
Bonin, Jennifer
2016-04-01
The GRACE mission has done an admirable job of measuring large-scale mass changes over Greenland since its launch in 2002. However before that time, measurements of large-scale ice mass balance were few and far between, leading to a lack of baseline knowledge. High-quality Satellite Laser Ranging (SLR) data existed a decade earlier, but normally has too low a spatial resolution to be used for this purpose. I demonstrate that a least squares inversion technique can reconstitute the SLR data and use it to measure ice loss over Greenland. To do so, I first simulate the problem by degrading today's GRACE data to a level comparable with SLR, then demonstrating that the inversion can re-localize Greenland's contribution to the low-resolution signal, giving an accurate time series of mass change over all of Greenland which compares well with the full-resolution GRACE estimates. I then utilize that method on the actual SLR data, resulting in an independent 1994-2014 time series of mass change over Greenland. I find favorable agreement between the pure-SLR inverted results and the 2012 Ice-sheet Mass Balance Inter-comparison Exercise (IMBIE) results, which are largely based on the "input-output" modeling method before GRACE's launch.
NASA Astrophysics Data System (ADS)
Ivins, E. R.; Wahr, J. M.; Schrama, E. J.; Milne, G. A.; Barletta, V.; Horwath, M.; Whitehouse, P.
2012-12-01
In preparation for the Inter-govermental Panel on Climate Change: Assessment Report 5 (IPCC AR5), ESA and NASA have formed a committee of experts to perform a formal set of comparative experiments concerning space observations of ice sheet mass balance. This project began in August of 2011 and has now concluded with a report submitted for Science (Shepherd et al., 2012). The focus of the work conducted is to re-evaluate scientific reports on the mass balance of Greenland ice sheet (GIS) and Antarctic ice sheet (AIS). The most serious discrepancies have been reported for the AIS, amounting to as much as 0.9 mm/yr in discrepant sea level contribution. A direct method of determining the AIS is by space gravimetry. However, for this method to contribute to our understanding of sea level change, we require knowledge of present-day non-elastic vertical movements of bedrock in Antarctica. Quantifying the uncertainty and bias caused by lack of observational control on models of regional glacial isostatic adjustment (GIA), was a major focus for our experiments. This regional process is the most problematic error source for GRACE-determinations of ice mass balance in Antarctica. While GIA likely dominates some large vertical motions in Antarctica that are now observed with GPS (Thomas et al., 2011, GRL), interpretations still require models. The reported uncertainty for space gravimetric (GRACE) based sea level sourcing is roughly 0.20 to 0.35 mm/yr. The uncertainty is also part of the error budget for mass balances derived from altimetry measurements, though at a much lower level. Analysis of the GRACE time series using CSR RL04 (2003.0-2010.10) for AIS mass balance reveals a small trend of order +1 to -24 Gt/yr without a GIA correction. Three periods were selected over which to perform inter-comparisons (see Table). One class of GIA models, that relies primarily on far field sea level reconstructions (e.g. ICE-5G), provide a GIA correction that places AIS mass imbalance (
Myths and methodologies: Making sense of exercise mass and water balance.
Cheuvront, Samuel N; Montain, Scott J
2017-09-01
What is the topic of this review? There is a need to revisit the basic principles of exercise mass and water balance, the use of common equations and the practice of interpreting outcomes. What advances does it highlight? We propose use of the following equation as a way of simplifying exercise mass and water balance calculations in conditions where food is not consumed and waste is not excreted: ∆body mass - 0.20 g/kcal -1 = ∆body water. The relative efficacy of exercise drinking behaviours can be judged using the following equation: percentage dehydration = [(∆body mass - 0.20 g kcal -1 )/starting body mass] × 100. Changes in body mass occur because of flux in liquids, solids and gases. This knowledge is crucial for understanding metabolism, health and human water needs. In exercise science, corrections to observed changes in body mass to estimate water balance are inconsistently applied and often misinterpreted, particularly after prolonged exercise. Although acute body mass losses in response to exercise can represent a close surrogate for body water losses, the discordance between mass and water balance equivalence becomes increasingly inaccurate as more and more energy is expended. The purpose of this paper is briefly to clarify the roles that respiratory water loss, gas exchange and metabolic water production play in the correction of body mass changes for fluid balance determinations during prolonged exercise. Computations do not include waters of association with glycogen because any movement of water among body water compartments contributes nothing to water or mass flux from the body. Estimates of sweat loss from changes in body mass should adjust for non-sweat losses when possible. We propose use of the following equation as a way of simplifying the study of exercise mass and water balance: ∆body mass - 0.20 g kcal -1 = ∆body water. This equation directly controls for the influence of energy expenditure on body mass
Are nonsymmetric balanced configurations of four equal masses virtual or real?
NASA Astrophysics Data System (ADS)
Chenciner, Alain
2017-11-01
Balanced configurations of N point masses are the configurations which, in a Euclidean space of high enough dimension, i. e., up to 2( N - 1), admit a relative equilibrium motion under the Newtonian (or similar) attraction. Central configurations are balanced and it has been proved by Alain Albouy that central configurations of four equal masses necessarily possess a symmetry axis, from which followed a proof that the number of such configurations up to similarity is finite and explicitly describable. It is known that balanced configurations of three equal masses are exactly the isosceles triangles, but it is not known whether balanced configurations of four equal masses must have some symmetry. As balanced configurations come in families, it makes sense to look for possible branches of nonsymmetric balanced configurations bifurcating from the subset of symmetric ones. In the simpler case of a logarithmic potential, the subset of symmetric balanced configurations of four equal masses is easy to describe as well as the bifurcation locus, but there is a grain of salt: expressed in terms of the squared mutual distances, this locus lies almost completely outside the set of true configurations (i. e., generalizations of triangular inequalities are not satisfied) and hence could lead most of the time only to the bifurcation of a branch of virtual nonsymmetric balanced configurations. Nevertheless, a tiny piece of the bifurcation locus lies within the subset of real balanced configurations symmetric with respect to a line and hence has a chance to lead to the bifurcation of real nonsymmetric balanced configurations. This raises the question of the title, a question which, thanks to the explicit description given here, should be solvable by computer experts even in the Newtonian case. Another interesting question is about the possibility for a bifurcating branch of virtual nonsymmetric balanced configurations to come back to the domain of true configurations.
Re-assessment of the mass balance of the Abbot and Getz sectors of West Antarctica
NASA Astrophysics Data System (ADS)
Chuter, S.; Bamber, J. L.
2016-12-01
Large discrepancies exist in mass balance estimates for the Getz and Abbot drainage basins, primarily due to previous poor knowledge of ice thickness at the grounding line, poor coverage by previous altimetry missions and signal leakage issues for GRACE. Large errors arise when using ice thickness measurements derived from ERS-1 and/or ICESat altimetry data due to poor track spacing, `loss of lock' issues near the grounding line and the complex morphology of these shelves, requiring fine resolution to derive robust and accurate elevations close to the grounding line. However, the advent of CryoSat-2 with its unique orbit and SARIn mode of operation has overcome these issues and enabled the determination of ice shelf thickness at a much higher accuracy than possible from previous satellites, particularly within the grounding zone. Here we present a contemporary estimate of ice sheet mass balance for the both the Getz and Abbot drainage basins. This is achieved through the use of contemporary velocity data derived from Landsat feature tracking and the use of CryoSat-2 derived ice thickness measurements. Additionally, we use this new ice thickness dataset to reassess mass balance estimates from 2008/2009, where there were large disparities between results from radar altimetry and Input-Output methodologies over the Abbot region in particular. These contemporary results are compared with other present day estimates from gravimetry and altimetry elevation changes.
Modelled and observed mass balance of Rikha Samba Glacier, Nepal, Central Himalaya
NASA Astrophysics Data System (ADS)
Gurung, T. R.; Kayastha, R. B.; Fujita, K.; Sinisalo, A. K.; Stumm, D.; Joshi, S.; Litt, M.
2016-12-01
Glacier mass balance variability has an implication for the regional water resources and it helps to understand the response of glacier to climate change in the Himalayan region. Several mass balance studies have been started in the Himalayan region since 1970s, but they are characterized by frequent temporal gaps and a poor spatial representatively. This study aims at bridging the temporal gaps in a long term mass balance series of the Rikha Samba glacier (5383 - 6475 m a.s.l.), a benchmark glacier located in the Hidden Valley, Mustang, Nepal. The ERA Interim reanalysis data for the period 2011-2015 is calibrated with the observed meteorological variables from an AWS installed near the glacier terminus. We apply an energy mass balance model, validated with the available in-situ measurements for the years 1998 and 2011-2015. The results show that the glacier is shrinking at a moderate negative mass balance rate for the period 1995 to 2015 and the high altitude location of Rikha Samba also prevents a bigger mass loss compared to other small Himalayan glaciers. Precipitation from July to January and the mean air temperature from June to October are the most influential climatic parameters of the annual mass balance variability of Rikha Samba glacier.
NASA Astrophysics Data System (ADS)
Schäfer, Martina; Möller, Marco; Zwinger, Thomas; Moore, John
2016-04-01
Using a coupled simulation set-up between a by statistical climate data forced and to ice-cap resolution downscaled mass balance model and an ice-dynamic model, we study coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analysing the impacts of different imposed coupling intervals on mass-balance and sea-level rise (SLR) projections. Based on a method to estimate errors introduced by different coupling schemes, we find that neglecting the topographic feedback in the coupling leads to underestimations of 10-20% in SLR projections on century time-scales in our model compared to full coupling (i.e., exchange of properties using smallest occurring time-step). Using the same method it also is shown that parametrising mass-balance adjustment for changes in topography using lapse rates is a - in computational terms - cost-effective reasonably accurate alternative applied to an ice-cap like Vestfonna. We test the forcing imposed by different emission pathways (RCP 2.4, 4.5, 6.0 and 8.5). For most of them, over the time-period explored (2000-2100), fast-flowing outlet glaciers decrease in impacting SLR due to their deceleration and reduced mass flux as they thin and retreat from the coast, hence detaching from the ocean and thereby losing their major mass drainage mechanism, i.e., calving.
Overview of Ice-Sheet Mass Balance and Dynamics from ICESat Measurements
NASA Technical Reports Server (NTRS)
Zwally, H. Jay
2010-01-01
The primary purpose of the ICESat mission was to determine the present-day mass balance of the Greenland and Antarctic ice sheets, identify changes that may be occurring in the surface-mass flux and ice dynamics, and estimate their contributions to global sea-level rise. Although ICESat's three lasers were planned to make continuous measurements for 3 to 5 years, the mission was re-planned to operate in 33-day campaigns 2 to 3 times each year following failure of the first laser after 36 days. Seventeen campaigns were conducted with the last one in the Fall of 2009. Mass balance maps derived from measured ice-sheet elevation changes show that the mass loss from Greenland has increased significantly to about 170 Gt/yr for 2003 to 2007 from a state of near balance in the 1990's. Increased losses (189 Gt/yr) from melting and dynamic thinning are over seven times larger'than increased gains (25 gt/yr) from precipitation. Parts of the West Antarctic ice sheet and the Antarctic Peninsula are losing mass at an increasing rate, but other parts of West Antarctica and the East Antarctic ice sheet are gaining mass at an increasing rate. Increased losses of 35 Gt/yr in Pine Island, Thwaites-Smith, and Marie-Bryd.Coast are more than balanced by gains in base of Peninsula and ice stream C, D, & E systems. From the 1992-2002 to 2003-2007 period, the overall mass balance for Antarctica changed from a loss of about 60 Gt/yr to near balance or slightly positive.
Local topography increasingly influences the mass balance of a retreating cirque glacier
Florentine, Caitlyn; Harper, Joel T.; Fagre, Daniel B.; Moore, Johnnie; Peitzsch, Erich H.
2018-01-01
Local topographically driven processes – such as wind drifting, avalanching, and shading – are known to alter the relationship between the mass balance of small cirque glaciers and regional climate. Yet partitioning such local effects from regional climate influence has proven difficult, creating uncertainty in the climate representativeness of some glaciers. We address this problem for Sperry Glacier in Glacier National Park, USA, using field-measured surface mass balance, geodetic constraints on mass balance, and regional climate data recorded at a network of meteorological and snow stations. Geodetically derived mass changes during 1950–1960, 1960–2005, and 2005–2014 document average mass change rates during each period at −0.22 ± 0.12, −0.18 ± 0.05, and −0.10 ± 0.03 m w.e. yr−1, respectively. A correlation of field-measured mass balance and regional climate variables closely (i.e., within 0.08 m w.e. yr−1) predicts the geodetically measured mass loss from 2005 to 2014. However, this correlation overestimates glacier mass balance for 1950–1960 by +1.20 ± 0.95 m w.e. yr−1. Our analysis suggests that local effects, not represented in regional climate variables, have become a more dominant driver of the net mass balance as the glacier lost 0.50 km2 and retreated further into its cirque.
Recent Changes in Ices Mass Balance of the Amundsen Sea Sector
NASA Astrophysics Data System (ADS)
Sutterley, T. C.; Velicogna, I.; Rignot, E. J.; Mouginot, J.; Flament, T.; van den Broeke, M. R.; van Wessem, M.; Reijmer, C.
2014-12-01
The glaciers flowing into the Amundsen Sea Embayment (ASE) sector of West Antarctica were confirmed in the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) to be the dominant contributors to the current Antarctic ice mass loss, and recently recognized to be undergoing marine ice sheet instability. Here, we investigate their regional ice mass balance using a time series of satellite and airborne data combined with model output products from the Regional Atmospheric and Climate Model (RACMO). Our dataset includes laser altimetry from NASA's ICESat-1 satellite mission and from Operation IceBridge (OIB) airborne surveys, satellite radar altimetry data from ESA's Envisat mission, time-variable gravity data from NASA/DLR's GRACE mission, surface mass balance products from RACMO, ice velocity from a combination of international synthetic aperture radar satellites and ice thickness data from OIB. We find a record of ice mass balance for the ASE where all the analyzed techniques agree remarkably in magnitude and temporal variability. The mass loss of the region has been increasing continuously since 1992, with no indication of a slow down. The mass loss during the common period averaged 91 Gt/yr and accelerated 20 Gt/yr2. In 1992-2013, the ASE contributed 4.5 mm global sea level rise. Overall, our results demonstrate the synergy of multiple analysis techniques for examining Antarctic Ice Sheet mass balance at the regional scale. This work was performed at UCI and JPL under a contract with NASA.
50 years of mass balance observations at Vernagtferner, Eastern Alps
NASA Astrophysics Data System (ADS)
Braun, Ludwig; Mayer, Christoph
2016-04-01
The determination and monitoring of the seasonal and annual glacier mass balances of Vernagtferner, Austria, started in 1964 by the Commission of Glaciology, Bavarian Academy of Sciences. Detailed and continuous climate- and runoff measurements complement this mass balance series since 1974. Vernagtferner attracted the attention of scientists since the beginning of the 17th century due to its rapid advances and the resulting glacier lake outburst floods in the Ötztal valley. This is one reason for the first photogrammetric survey in 1889, which was followed by frequent topographic surveys, adding up to more than ten digital elevation models of the glacier until today. By including the known maximum glacier extent at the end of the Little Ice Age in 1845, the geodetic glacier volume balances cover a time span of almost 170 years. The 50 years of glacier mass balance and 40 years of water balance in the drainage basin are therefore embedded in a considerably longer period of glacier evolution, allowing an interpretation within an extended frame of climatology and ice dynamics. The direct mass balance observations cover not only the period of alpine-wide strong glacier mass loss since the beginning of the 1990s. The data also contain the last period of glacier advances between 1970 and 1990. The combination of the observed surface mass exchange and the determined periodic volumetric changes allows a detailed analysis of the dynamic reaction of the glacier over the period of half a century. The accompanying meteorological observations are the basis for relating these reactions to the climatic changes during this period. Vernagtferner is therefore one of the few glaciers in the world, where a very detailed glacier-climate reaction was observed for many decades and can be realistically reconstructed back to the end of the Little Ice Age.
Evaluation of a mass-balance approach to determine consumptive water use in northeastern Illinois
Mills, Patrick C.; Duncker, James J.; Over, Thomas M.; Marian Domanski,; ,; Engel, Frank
2014-01-01
Under ideal conditions, accurate quantification of consumptive use at the sewershed scale by the described mass-balance approach might be possible. Under most prevailing conditions, quantification likely would be more costly and time consuming than that of the present study, given the freely contributed technical support of the host community and relatively appropriate conditions of the study area. Essentials to quantification of consumptive use are a fully cooperative community, storm and sanitary sewers that are separate, and newer sewer infrastructure and (or) a robust program for limiting infiltration, exfiltration, and inflow.
Mass-balance modelling of Ak-Shyirak massif Glaciers, Inner Tian Shan
NASA Astrophysics Data System (ADS)
Rets, Ekaterina; Barandun, Martina; Belozerov, Egor; Petrakov, Dmitry; Shpuntova, Alena
2017-04-01
Tian Shan is a water tower of Central Asia. Rapid and accelerating glacier downwasting is typical for this region. Study sites - Sary-Tor glacier and Glacier No.354 are located in Ak-Shyirak massif, Naryn headwaters. Sary-Tor was chosen as representative for Ak-Shyirak (Ushnurtsev, 1991; Oledeneniye TianShanya, 1995) for direct mass-balance measurements in 1985-1991. Glacier No.354 was an object of direct mass-balance measurements for 2011-2016. An energy-balance distributed A-Melt model (Rets et al, 2010) was used to reconstruct mass-balance for the glaciers for 2003-2015. Verification of modelingresults showed a good reproduction of direct melting measurements data on ablation stakes and mass loss according to geodetic method. Modeling results for Glacier No. 354 were compared to different modeling approach: distributed accumulation and temperature-index melt (Kronenberg et al, 2016)
How many stakes are required to measure the mass balance of a glacier?
Fountain, A.G.; Vecchia, A.
1999-01-01
Glacier mass balance is estimated for South Cascade Glacier and Maclure Glacier using a one-dimensional regression of mass balance with altitude as an alternative to the traditional approach of contouring mass balance values. One attractive feature of regression is that it can be applied to sparse data sets where contouring is not possible and can provide an objective error of the resulting estimate. Regression methods yielded mass balance values equivalent to contouring methods. The effect of the number of mass balance measurements on the final value for the glacier showed that sample sizes as small as five stakes provided reasonable estimates, although the error estimates were greater than for larger sample sizes. Different spatial patterns of measurement locations showed no appreciable influence on the final value as long as different surface altitudes were intermittently sampled over the altitude range of the glacier. Two different regression equations were examined, a quadratic, and a piecewise linear spline, and comparison of results showed little sensitivity to the type of equation. These results point to the dominant effect of the gradient of mass balance with altitude of alpine glaciers compared to transverse variations. The number of mass balance measurements required to determine the glacier balance appears to be scale invariant for small glaciers and five to ten stakes are sufficient.
Glacier mass-balance fluctuations in the Pacific Northwest and Alaska, USA
Josberger, E.G.; Bidlake, W.R.; March, R.S.; Kennedy, B.W.
2007-01-01
The more than 40 year record of net and seasonal mass-balance records from measurements made by the United States Geological Survey on South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, shows annual and interannual fluctuations that reflect changes in the controlling climatic conditions at regional and global scales. As the mass-balance record grows in length, it is revealing significant changes in previously described glacier mass-balance behavior, and both inter-glacier and glacier-climate relationships. South Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime climate of the northeast Pacific Ocean. Their net balances have generally been controlled by winter accumulation, with fluctuations that are strongly related to the Pacific Decadal Oscillation (PDO). Recently, warm dry summers have begun to dominate the net balance of the two maritime glaciers, with a weakening of the correlation between the winter balance fluctuations and the PDO. Non-synchronous periods of positive and negative net balance for each glacier prior to 1989 were followed by a 1989-2004 period of synchronous and almost exclusively negative net balances that averaged -0.8 m for the three glaciers.
Using Terrain Analysis and Remote Sensing to Improve Snow Mass Balance and Runoff Prediction
NASA Astrophysics Data System (ADS)
Venteris, E. R.; Coleman, A. M.; Wigmosta, M. S.
2010-12-01
Approximately 70-80% of the water in the international Columbia River basin is sourced from snowmelt. The demand for this water has competing needs, as it is used for agricultural irrigation, municipal, hydro and nuclear power generation, and environmental in-stream flow requirements. Accurate forecasting of water supply is essential for planning current needs and prediction of future demands due to growth and climate change. A significant limitation on current forecasting is spatial and temporal uncertainty in snowpack characteristics, particularly snow water equivalent. Currently, point measurements of snow mass balance are provided by the NRCS SNOTEL network. Each site consists of a snow mass sensor and meteorology station that monitors snow water equivalent, snow depth, precipitation, and temperature. There are currently 152 sites in the mountains of Oregon and Washington. An important step in improving forecasts is determining how representative each SNOTEL site is of the total mass balance of the watershed through a full accounting of the spatiotemporal variability in snowpack processes. This variation is driven by the interaction between meteorological processes, land cover, and landform. Statistical and geostatistical spatial models relate the state of the snowpack (characterized through SNOTEL, snow course measurements, and multispectral remote sensing) to terrain attributes derived from digital elevation models (elevation, aspect, slope, compound topographic index, topographic shading, etc.) and land cover. Time steps representing the progression of the snow season for several meteorologically distinct water years are investigated to identify and quantify dominant physical processes. The spatially distributed snow balance data can be used directly as model inputs to improve short- and long-range hydrologic forecasts.
Fast and accurate mock catalogue generation for low-mass galaxies
NASA Astrophysics Data System (ADS)
Koda, Jun; Blake, Chris; Beutler, Florian; Kazin, Eyal; Marin, Felipe
2016-06-01
We present an accurate and fast framework for generating mock catalogues including low-mass haloes, based on an implementation of the COmoving Lagrangian Acceleration (COLA) technique. Multiple realisations of mock catalogues are crucial for analyses of large-scale structure, but conventional N-body simulations are too computationally expensive for the production of thousands of realizations. We show that COLA simulations can produce accurate mock catalogues with a moderate computation resource for low- to intermediate-mass galaxies in 1012 M⊙ haloes, both in real and redshift space. COLA simulations have accurate peculiar velocities, without systematic errors in the velocity power spectra for k ≤ 0.15 h Mpc-1, and with only 3-per cent error for k ≤ 0.2 h Mpc-1. We use COLA with 10 time steps and a Halo Occupation Distribution to produce 600 mock galaxy catalogues of the WiggleZ Dark Energy Survey. Our parallelized code for efficient generation of accurate halo catalogues is publicly available at github.com/junkoda/cola_halo.
A reconciled estimate of ice-sheet mass balance.
Shepherd, Andrew; Ivins, Erik R; A, Geruo; Barletta, Valentina R; Bentley, Mike J; Bettadpur, Srinivas; Briggs, Kate H; Bromwich, David H; Forsberg, René; Galin, Natalia; Horwath, Martin; Jacobs, Stan; Joughin, Ian; King, Matt A; Lenaerts, Jan T M; Li, Jilu; Ligtenberg, Stefan R M; Luckman, Adrian; Luthcke, Scott B; McMillan, Malcolm; Meister, Rakia; Milne, Glenn; Mouginot, Jeremie; Muir, Alan; Nicolas, Julien P; Paden, John; Payne, Antony J; Pritchard, Hamish; Rignot, Eric; Rott, Helmut; Sørensen, Louise Sandberg; Scambos, Ted A; Scheuchl, Bernd; Schrama, Ernst J O; Smith, Ben; Sundal, Aud V; van Angelen, Jan H; van de Berg, Willem J; van den Broeke, Michiel R; Vaughan, David G; Velicogna, Isabella; Wahr, John; Whitehouse, Pippa L; Wingham, Duncan J; Yi, Donghui; Young, Duncan; Zwally, H Jay
2012-11-30
We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods--especially in Greenland and West Antarctica--and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 ± 49, +14 ± 43, -65 ± 26, and -20 ± 14 gigatonnes year(-1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year(-1) to the rate of global sea-level rise.
NASA Astrophysics Data System (ADS)
Steffensen Schmidt, Louise; Aðalgeirsdóttir, Guðfinna; Guðmundsson, Sverrir; Langen, Peter L.; Pálsson, Finnur; Mottram, Ruth; Gascoin, Simon; Björnsson, Helgi
2017-04-01
The evolution of the surface mass balance of Vatnajökull ice cap, Iceland, from 1981 to the present day is estimated by using the Regional Climate Model HIRHAM5 to simulate the surface climate. A new albedo parametrization is used for the simulation, which describes the albedo with an exponential decay with time. In addition, it utilizes a new background map of the ice albedo created from MODIS data. The simulation is validated against observed daily values of weather parameters from five Automatic Weather Stations (AWSs) from 2001-2014, as well as mass balance measurements from 1995-2014. The modelled albedo is overestimated at the AWS sites in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and the model not accounting for dust and ash deposition during dust storms and volcanic eruptions. A comparison with the specific summer, winter, and annual mass balance for all Vatnajökull from 1995-2014 shows a good overall fit during the summer, with the model underestimating the balance by only 0.04 m w. eq. on average. The winter balance, on the other hand, is overestimated by 0.5 m w. eq. on average, mostly due to an overestimation of the precipitation at the highest areas of the ice cap. A simple correction of the accumulation at these points reduced the error to 0.15 m w. eq. The model captures the evolution of the specific mass balance well, for example it captures an observed shift in the balance in the mid-1990s, which gives us confidence in the results for the entire model run. Our results show the importance of bare ice albedo for modelled mass balance and that processes not currently accounted for in RCMs, such as dust storms, are an important source of uncertainty in estimates of the snow melt rate.
Results of the Lake Michigan Mass Balance Project: Atrazine Modeling Report
This report covers an overview of chemical properties, measurements in air and water, model construct and assumptions, and results of mathematical mass balance modeling of the herbicide atrazine in the Lake Michigan basin. Within the context of the mass balance, an overview of a...
NASA Astrophysics Data System (ADS)
Young, Emma V.
for when processing gravity measurements to derive the residual gravity signal of the glacier mass balance. Accurate measurements of elevation changes, seasonal snow depth, and the VGG should be performed in future gravity surveys of glaciers.
Estimates of Ice Sheet Mass Balance from Satellite Altimetry: Past and Future
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Zukor, Dorothy J. (Technical Monitor)
2001-01-01
A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the 20% uncertainty in current mass balance corresponds to 1.6 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. A principal purpose of obtaining ice sheet elevation changes from satellite altimetry has been estimation of the current ice sheet mass balance. Limited information on ice sheet elevation change and their implications about mass balance have been reported by several investigators from radar altimetry (Seasat, Geosat, ERS-1&2). Analysis of ERS-1&2 data over Greenland for 7 years from 1992 to 1999 shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. Observed seasonal and interannual variations in ice surface elevation are larger than previously expected because of seasonal and interannUal variations in precipitation, melting, and firn compaction. In the accumulation zone, the variations in firn compaction are modeled as a function of temperature leaving variations in precipitation and the mass balance trend. Significant interannual variations in elevation in some locations, in particular the difference in trends from 1992 to 1995 compared to 1995 to 1999, can be explained by changes in precipitation over Greenland. Over the 7 years, trends in elevation are mostly positive at higher elevations and negative at lower elevations. In addition, trends for the winter seasons (from a trend analysis through the average winter elevations) are more positive than the corresponding trends for the summer. At lower elevations, the 7-year trends in some locations are strongly negative for summer and near zero or slightly positive for winter. These
Forecasting Glacier Evolution and Hindcasting Paleoclimates In Light of Mass Balance Nonlinearities
NASA Astrophysics Data System (ADS)
Malone, A.; Doughty, A. M.; MacAyeal, D. R.
2016-12-01
Glaciers are commonly used barometers of present and past climate change, with their variations often being linked to shifts in the mean climate. Climate variability within a unchanging mean state, however, can produce short term mass balance and glacier length anomalies, complicating this linkage. Also, the mass balance response to this variability can be nonlinear, possibly impacting the longer term state of the glacier. We propose a conceptual model to understand these nonlinearities and quantify their impacts on the longer term mass balance and glacier length. The relationship between mass balance and elevation, i.e. the vertical balance profile (VBP), illuminates these nonlinearities (Figure A). The VBP, given here for a wet tropical glacier, is piecewise, which can lead to different mass balance responses to climate anomalies of similar magnitude but opposite sign. We simulate the mass balance response to climate variability by vertically (temperature anomalies) and horizontally (precipitation anomalies) transposing the VBP for the mean climate (Figure A). The resulting anomalous VBP is the superposition of the two translations. We drive a 1-D flowline model with 10,000 years of anomalous VBPs. The aggregate VBP for the mean climate including variability differs from the VBP for the mean climate excluding variability, having a higher equilibrium line altitude (ELA) and a negative mass balance (Figure B). Accordingly, the glacier retreats, and the equilibrium glacier length for the aggregate VBP is the same as the mean length from the 10,000 year flowline simulation (Figure C). The magnitude of the VBP shift and glacier retreat increases with greater temperature variability and larger discontinuities in the VBP slope. These results highlight the importance of both the climate mean and variability in determining the longer term state of the glacier. Thus, forecasting glacier evolution or hindcasting past climates should also include representation of climate
The Ice Sheet Mass Balance Inter-comparison Exercise
NASA Astrophysics Data System (ADS)
Shepherd, A.; Ivins, E. R.
2015-12-01
Fluctuations in the mass of ice stored in Antarctica and Greenland are of considerable societal importance. The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a joint-initiative of ESA and NASA aimed at producing a single estimate of the global sea level contribution to polar ice sheet losses. Within IMBIE, estimates of ice sheet mass balance are developed from a variety of satellite geodetic techniques using a common spatial and temporal reference frame and a common appreciation of the contributions due to external signals. The project brings together the laboratories and space agencies that have been instrumental in developing independent estimates of ice sheet mass balance to date. In its first phase, IMBIE involved 27 science teams, and delivered a first community assessment of ice sheet mass imbalance to replace 40 individual estimates. The project established that (i) there is good agreement between the three main satellite-based techniques for estimating ice sheet mass balance, (ii) combining satellite data sets leads to significant improvement in certainty, (iii) the polar ice sheets contributed 11 ± 4 mm to global sea levels between 1992 and 2012, and (iv) that combined ice losses from Antarctica and Greenland have increased over time, rising from 10% of the global trend in the early 1990's to 30% in the late 2000's. Demand for an updated assessment has grown, and there are now new satellite missions, new geophysical corrections, new techniques, and new teams producing data. The period of overlap between independent satellite techniques has increased from 5 to 12 years, and the full period of satellite data over which an assessment can be performed has increased from 19 to 40 years. It is also clear that multiple satellite techniques are required to confidently separate mass changes associated with snowfall and ice dynamical imbalance - information that is of critical importance for climate modelling. This presentation outlines the approach
NASA Astrophysics Data System (ADS)
Buri, Pascal; Miles, Evan; Ragettli, Silvan; Brun, Fanny; Steiner, Jakob; Pellicciotti, Francesca
2016-04-01
Supraglacial cliffs are a surface feature typical of debris-covered glaciers, affecting surface evolution, glacier downwasting and mass balance by providing a direct ice-atmosphere interface. As a result, melt rates can be very high and ice cliffs may account for a significant portion of the total glacier mass loss. However, their contribution to glacier mass balance has rarely been quantified through physically-based models. Most cliff energy balance models are point scale models which calculate energy fluxes at individual cliff locations. Results from the only grid based model to date accurately reflect energy fluxes and cliff melt, but modelled backwasting patterns are in some cases unrealistic, as the distribution of melt rates would lead to progressive shallowing and disappearance of cliffs. Based on a unique multitemporal dataset of cliff topography and backwasting obtained from high-resolution terrestrial and aerial Structure-from-Motion analysis on Lirung Glacier in Nepal, it is apparent that cliffs exhibit a range of behaviours but most do not rapidly disappear. The patterns of evolution cannot be explained satisfactorily by atmospheric melt alone, and are moderated by the presence of supraglacial ponds at the base of cliffs and by cliff reburial with debris. Here, we document the distinct patterns of evolution including disappearance, growth and stability. We then use these observations to improve the grid-based energy balance model, implementing periodic updates of the cliff geometry resulting from modelled melt perpendicular to the ice surface. Based on a slope threshold, pixels can be reburied by debris or become debris-free. The effect of ponds are taken into account through enhanced melt rates in horizontal direction on pixels selected based on an algorithm considering distance to the water surface, slope and lake level. We use the dynamic model to first study the evolution of selected cliffs for which accurate, high resolution DEMs are available
Reassessment of the mass balance of the Abbot and Getz sectors of West Antarctica
NASA Astrophysics Data System (ADS)
Chuter, Stephen; Martín-Español, Alba; Wouters, Bert; Bamber, Jonathan
2017-04-01
Large discrepancies exist in mass balance estimates for the Getz and Abbot drainage basins, primarily due to previous poor knowledge of ice thickness at the grounding line, poor coverage by previous altimetry missions and signal leakage issues for GRACE. This is particularly the case for the Abbot region, where previously there have been contrasting positive ice sheet basin elevation rates from altimetry and negative mass budget estimates. Large errors arise when using ice thickness measurements derived from ERS-1 and/or ICESat altimetry data due to poor track spacing, 'loss of lock' issues near the grounding line and the complex morphology of these shelves, requiring fine resolution to derive robust and accurate elevations close to the grounding line. This was exemplified with the manual adjustments of up to 100 m required at the grounding line during the creation of Bedmap2. However, the advent of CryoSat-2 with its unique orbit and SARIn mode of operation has overcome these issues and enabled the determination of ice shelf thickness at a much higher accuracy than possible from previous satellites, particularly within the grounding zone. We present a reassessment of mass balance estimates for the 2007-2009 epoch using improved CryoSat-2 ice thicknesses. We find that CryoSat-2 ice thickness estimates are systematically thinner by 30% and 16.5% for the Abbot and Getz sectors respectively. Our new mass balance estimate of 8 ± 6 Gt yr-1for the Abbot region resolves the previous discrepancy with altimetry. Over the Getz region, the new mass balance estimate of 7.56 ± 16.6 Gt yr-1is in better agreement with other geodetic techniques. We also find there has been an increase in grounding line velocity of up to 20% since the 2007-2009 epoch, coupled with mean ice sheet thinning rates of -0.67 ± 0.13 m yr-1 derived from CryoSat-2 in fast flow regions. This is in addition to mean snowfall trends of -0.33 m yr-1w.e. since 2006. This suggests the onset of a dynamic
A Reconciled Estimate of Ice-Sheet Mass Balance
NASA Technical Reports Server (NTRS)
Shepherd, Andrew; Ivins, Erik R.; Geruo, A.; Barletta, Valentia R.; Bentley, Mike J.; Bettadpur, Srinivas; Briggs, Kate H.; Bromwich, David H.; Forsberg, Rene; Galin, Natalia;
2012-01-01
We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods-especially in Greenland and West Antarctica-and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 plus or minus 49, +14 plus or minus 43, -65 plus or minus 26, and -20 plus or minus 14 gigatonnes year(sup -1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 plus or minus 0.20 millimeter year(sup -1) to the rate of global sea-level rise.
Enforcing elemental mass and energy balances for reduced order models
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ma, J.; Agarwal, K.; Sharma, P.
2012-01-01
Development of economically feasible gasification and carbon capture, utilization and storage (CCUS) technologies requires a variety of software tools to optimize the designs of not only the key devices involved (e., g., gasifier, CO{sub 2} adsorber) but also the entire power generation system. High-fidelity models such as Computational Fluid Dynamics (CFD) models are capable of accurately simulating the detailed flow dynamics, heat transfer, and chemistry inside the key devices. However, the integration of CFD models within steady-state process simulators, and subsequent optimization of the integrated system, still presents significant challenges due to the scale differences in both time and length,more » as well the high computational cost. A reduced order model (ROM) generated from a high-fidelity model can serve as a bridge between the models of different scales. While high-fidelity models are built upon the principles of mass, momentum, and energy conservations, ROMs are usually developed based on regression-type equations and hence their predictions may violate the mass and energy conservation laws. A high-fidelity model may also have the mass and energy balance problem if it is not tightly converged. Conservations of mass and energy are important when a ROM is integrated to a flowsheet for the process simulation of the entire chemical or power generation system, especially when recycle streams are connected to the modeled device. As a part of the Carbon Capture Simulation Initiative (CCSI) project supported by the U.S. Department of Energy, we developed a software framework for generating ROMs from CFD simulations and integrating them with Process Modeling Environments (PMEs) for system-wide optimization. This paper presents a method to correct the results of a high-fidelity model or a ROM such that the elemental mass and energy are conserved perfectly. Correction factors for the flow rates of individual species in the product streams are solved using a
Mass balance approaches to understanding evolution of dripwater chemistry
NASA Astrophysics Data System (ADS)
Fairchild, I. J.; Baker, A.; Andersen, M. S.; Treble, P. C.
2015-12-01
Forward and inverse modelling of dripwater chemistry is a fast-developing area in speleothem science. Such approaches can incorporate theoretical, parameterized or observed relationships between forcing factors and water composition, but at the heart is mass balance: a fundamental principle that provides important constraints. Mass balance has been used in speleothem studies to trace the evolution of dissolved inorganic carbon and carbon isotopes from soil to cave, and to characterize the existence and quantification of prior calcite precipitation (PCP) based on ratios of Mg and Sr to Ca. PCP effects can dominate slow drips, whereas fast drips are more likely to show a residual variability linked to soil-biomass processes. A possible configuration of a more complete mass balance model is illustrated in the figure. Even in humid temperate climates, evapotranspiration can be 50% of total atmospheric precipitation leading to substantially raised salt contents and there can be significant exchange with biomass. In more arid settings, at least seasonal soil storage of salts is likely. Golgotha Cave in SW Australia is in a Mediterranean climate with a strong summer soil moisture deficit. The land surface is forested leading to large ion fluxes related to vegetation. There are also periodic disturbances related to fire. Mass balance approaches have been applied to an 8-year monitoring record. Inter-annual trends of elements coprecipitated in speleothems from fast drips are predicted to be dominated by biomass effects.
Improving Estimates of Greenland Ice Sheet Surface Mass Balance with Satellite Observations
NASA Astrophysics Data System (ADS)
Briggs, K.
2016-12-01
Mass losses from the Greenland Ice Sheet have been accelerating over recent years (e.g. McMillan et al., 2016; Velicogna et al., 2014). This acceleration has predominantly been linked to increasing rates of negative surface mass balance, and in particular, increasing ice surface melt rates (e.g. McMillan et al., 2016; Velicogna et al., 2014). At the ice sheet scale, SMB is assessed using SMB model outputs, which in addition to enabling understanding of the origin of mass balance signals, are required as ancillary data in mass balance assessments from altimetry and the mass budget method. Due to the importance of SMB for mass balance over Greenland and the sensitivity of mass balance assessments to SMB model outputs, high accuracy of these models is crucial. A critical limiting factor in SMB modeling is however, a lack of in-situ data that is required for model constraint and evaluation. Such data is limited in time and space due to inherent logistical and financial constraints. Remote sensing datasets, being spatially extensive and relatively densely sampled in both space and time, do not suffer such constraints. Here, we show satellite observations of Greenland SMB. McMillan, M., Leeson, A., Shepherd, A., Briggs, K., Armitage, T. W.K., Hogg, A., Kuipers Munneke, P., van den Broeke, M., Noël, B., van de Berg, W., Ligtenberg, S., Horwath, M., Groh, A. , Muir, A. and Gilbert, L. 2016. A high resolution record of Greenland Mass Balance. Geophysical Research Letters. 43, doi:10.1002/2016GL069666 Velicogna, I., Sutterley, T. C. and van den Broeke, M. R. 2014. Regional acceleration in ice mass loss from Greenland and Antarctica using GRACE time-variable gravity data. Geophysical Research Letters. 41, 8130-8137, doi:10.1002/2014GL061052
Calibrating a surface mass-balance model for Austfonna ice cap, Svalbard
NASA Astrophysics Data System (ADS)
Schuler, Thomas Vikhamar; Loe, Even; Taurisano, Andrea; Eiken, Trond; Hagen, Jon Ove; Kohler, Jack
2007-10-01
Austfonna (8120 km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (-318 mm w.e.).
Geodetic reanalysis of annual glaciological mass balances (2001-2011) of Hintereisferner, Austria
NASA Astrophysics Data System (ADS)
Klug, Christoph; Bollmann, Erik; Galos, Stephan Peter; Nicholson, Lindsey; Prinz, Rainer; Rieg, Lorenzo; Sailer, Rudolf; Stötter, Johann; Kaser, Georg
2018-03-01
This study presents a reanalysis of the glaciologically obtained annual glacier mass balances at Hintereisferner, Ötztal Alps, Austria, for the period 2001-2011. The reanalysis is accomplished through a comparison with geodetically derived mass changes, using annual high-resolution airborne laser scanning (ALS). The grid-based adjustments for the method-inherent differences are discussed along with associated uncertainties and discrepancies of the two methods of mass balance measurements. A statistical comparison of the two datasets shows no significant difference for seven annual, as well as the cumulative, mass changes over the 10-year record. Yet, the statistical view hides significant differences in the mass balance years 2002/03 (glaciological minus geodetic records = +0.92 m w.e.), 2005/06 (+0.60 m w.e.), and 2006/07 (-0.45 m w.e.). We conclude that exceptional meteorological conditions can render the usual glaciological observational network inadequate. Furthermore, we consider that ALS data reliably reproduce the annual mass balance and can be seen as validation or calibration tools for the glaciological method.
Ice-sheet mass balance and climate change.
Hanna, Edward; Navarro, Francisco J; Pattyn, Frank; Domingues, Catia M; Fettweis, Xavier; Ivins, Erik R; Nicholls, Robert J; Ritz, Catherine; Smith, Ben; Tulaczyk, Slawek; Whitehouse, Pippa L; Zwally, H Jay
2013-06-06
Since the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, new observations of ice-sheet mass balance and improved computer simulations of ice-sheet response to continuing climate change have been published. Whereas Greenland is losing ice mass at an increasing pace, current Antarctic ice loss is likely to be less than some recently published estimates. It remains unclear whether East Antarctica has been gaining or losing ice mass over the past 20 years, and uncertainties in ice-mass change for West Antarctica and the Antarctic Peninsula remain large. We discuss the past six years of progress and examine the key problems that remain.
Li, Ming; Josephs, Ralf D; Daireaux, Adeline; Choteau, Tiphaine; Westwood, Steven; Wielgosz, Robert I; Li, Hongmei
2018-06-04
Peptides are an increasingly important group of biomarkers and pharmaceuticals. The accurate purity characterization of peptide calibrators is critical for the development of reference measurement systems for laboratory medicine and quality control of pharmaceuticals. The peptides used for these purposes are increasingly produced through peptide synthesis. Various approaches (for example mass balance, amino acid analysis, qNMR, and nitrogen determination) can be applied to accurately value assign the purity of peptide calibrators. However, all purity assessment approaches require a correction for structurally related peptide impurities in order to avoid biases. Liquid chromatography coupled to high resolution mass spectrometry (LC-hrMS) has become the key technique for the identification and accurate quantification of structurally related peptide impurities in intact peptide calibrator materials. In this study, LC-hrMS-based methods were developed and validated in-house for the identification and quantification of structurally related peptide impurities in a synthetic human C-peptide (hCP) material, which served as a study material for an international comparison looking at the competencies of laboratories to perform peptide purity mass fraction assignments. More than 65 impurities were identified, confirmed, and accurately quantified by using LC-hrMS. The total mass fraction of all structurally related peptide impurities in the hCP study material was estimated to be 83.3 mg/g with an associated expanded uncertainty of 3.0 mg/g (k = 2). The calibration hierarchy concept used for the quantification of individual impurities is described in detail. Graphical abstract ᅟ.
NASA Astrophysics Data System (ADS)
Lehoczky, Annamária; Kern, Zoltán; Pongrácz, Rita
2014-05-01
Glacio-climatological studies recognise glacier mass balance changes as high-confident climate indicators. The climatic sensitivity of a glacier does not simply depend on regional climate variability but also influenced via large- and mesoscale atmospheric circulation patterns. This study focuses on recent changes in the mass balance using records from three border regions of Europe, and investigates the relationships between the seasonal mass balance components, regional climatic conditions, and distant atmospheric forcing. Since glaciers in different macro-climatological conditions (i.e., mid-latitudes or high-latitudes, dry-continental or maritime regions) may present strongly diverse mass balance characteristics, the three analysed regions were selected from different glacierised macroregions (using the database of the World Glacier Monitoring Service). These regions belong to the Caucasus Mountains (Central Europe macroregion), the Polar Ural (Northern Asia macroregion), and Svalbard (Arctic Islands macroregion). The analysis focuses on winter, summer, and annual mass balance series of eight glaciers. The climatic variables (atmospheric pressure, air temperature, precipitation) and indices of teleconnection patterns (e.g., North Atlantic Oscillation, Pacific Decadal Oscillation) are used from the gridded databases of the University of East Anglia, Climatic Research Unit and the National Oceanic and Atmospheric Administration, National Center for Environmental Prediction. However, the period and length of available mass balance data in the selected regions vary greatly (the first full record is in 1958, Polar Ural; the last is in 2010, Caucasus Mountains), a comparative analysis can be carried out for the period of 1968-1981. Since glaciers from different regions respond to large- and mesoscale climatic forcings differently, and because the mass balance of glaciers within a region often co-vary, our specific objectives are (i) to examine the variability and the
When Equal Masses Don't Balance
ERIC Educational Resources Information Center
Newburgh, Ronald; Peidle, Joseph; Rueckner, Wolfgang
2004-01-01
We treat a modified Atwood's machine in which equal masses do not balance because of being in an accelerated frame of reference. Analysis of the problem illuminates the meaning of inertial forces, d'Alembert's principle, the use of free-body diagrams and the selection of appropriate systems for the diagrams. In spite of the range of these…
NASA Astrophysics Data System (ADS)
Salafian, Iman; Stewart, Blake; Newman, Matthew; Zygielbaum, Arthur I.; Terry, Benjamin
2017-04-01
A four cable-driven parallel manipulator (CDPM), consisting of sophisticated spectrometers and imagers, is under development for use in acquiring phenotypic and environmental data over an acre-sized crop field. To obtain accurate and high quality data from the instruments, the end effector must be stable during sensing. One of the factors that reduces stability is the center of mass offset of the end effector, which can cause a pendulum effect or undesired tilt angle. The purpose of this work is to develop a system and method for balancing the center of mass of a 12th-scale CDPM to minimize vibration that can cause error in the acquired data. A simple method for balancing the end effector is needed to enable end users of the CDPM to arbitrarily add and remove sensors and imagers from the end effector as their experiments may require. A Center of Mass Balancing System (CMBS) is developed in this study which consists of an adjustable system of weights and a gimbal for tilt mitigation. An electronic circuit board including an orientation sensor, wireless data communication, and load cells was designed to validate the CMBS. To measure improvements gained by the CMBS, several static and dynamic experiments are carried out. In the experiments, the dynamic vibrations due to the translational motion and static orientation were measured with and without CMBS use. The results show that the CMBS system improves the stability of the end-effector by decreasing vibration and static tilt angle.
NASA Astrophysics Data System (ADS)
Réveillet, Marion; Six, Delphine; Vincent, Christian; Rabatel, Antoine; Dumont, Marie; Lafaysse, Matthieu; Morin, Samuel; Vionnet, Vincent; Litt, Maxime
2018-04-01
This study focuses on simulations of the seasonal and annual surface mass balance (SMB) of Saint-Sorlin Glacier (French Alps) for the period 1996-2015 using the detailed SURFEX/ISBA-Crocus snowpack model. The model is forced by SAFRAN meteorological reanalysis data, adjusted with automatic weather station (AWS) measurements to ensure that simulations of all the energy balance components, in particular turbulent fluxes, are accurately represented with respect to the measured energy balance. Results indicate good model performance for the simulation of summer SMB when using meteorological forcing adjusted with in situ measurements. Model performance however strongly decreases without in situ meteorological measurements. The sensitivity of the model to meteorological forcing indicates a strong sensitivity to wind speed, higher than the sensitivity to ice albedo. Compared to an empirical approach, the model exhibited better performance for simulations of snow and firn melting in the accumulation area and similar performance in the ablation area when forced with meteorological data adjusted with nearby AWS measurements. When such measurements were not available close to the glacier, the empirical model performed better. Our results suggest that simulations of the evolution of future mass balance using an energy balance model require very accurate meteorological data. Given the uncertainties in the temporal evolution of the relevant meteorological variables and glacier surface properties in the future, empirical approaches based on temperature and precipitation could be more appropriate for simulations of glaciers in the future.
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.
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.
NASA Astrophysics Data System (ADS)
Mandal, Arindan; Ramanathan, Alagappan; Farooq Azam, Mohd; Wagnon, Patrick; Vincent, Christian; Linda, Anurag; Sharma, Parmanand; Angchuk, Thupstan; Bahadur Singh, Virendra; Pottakkal, Jose George; Kumar, Naveen; Soheb, Mohd
2015-04-01
Several studies on Himalayan glaciers have been recently initiated as they are of particular interest in terms of future water supply, regional climate change and sea-level rise. In 2002, a long-term monitoring program was initiated on Chhota Shigri Glacier (15.7 square km, 9 km long, 6263-4050 m a.s.l.) located in Lahaul and Spiti Valley, Himachal Pradesh, India. This glacier lies in the monsoon-arid transition zone (western Himalaya) and is a representative glacier in Lahaul and Spiti Valley. While annual mass balances have been measured continuously since 2002 using the glaciological method, seasonal scale observations began in 2009. The annual and seasonal mass balances were then analyzed along with meteorological conditions in order to understand the role of winter and summer balances on annual glacier-wide mass balance of Chhota Shigri glacier. During the period 2002-2013, the glacier experienced a negative glacier-wide mass balance of -0.59±0.40 m w.e. a-1 with a cumulative glaciological mass balance of -6.45 m w.e. Annual glacier-wide mass balances were negative except for four years (2004/05, 2008/09, 2009/10 and 2010/11) where it was generally close to balanced conditions. Equilibrium line altitude (ELA) for steady state condition is calculated as 4950 m a.s.l. corresponding to an accumulation area ratio (AAR) of 62% using annual glacier-wide mass balance, ELA and AAR data between 2002 and 2013. The winter glacier-wide mass balance between 2009 and 2013 ranges from a maximum value of 1.38 m w.e. in 2009/10 to a minimum value of 0.89 in 2012/13 year whereas the summer glacier-wide mass balance varies from the highest value of -0.95 m w.e. in 2010/11 to the lowest value of -1.72 m w.e. in 2011/12 year. The mean vertical mass balance gradient between 2002 and 2013 was 0.66 m w.e. (100 m)-1 quite similar to Alps, Nepalese Himalayas etc. Over debris covered area, the gradients are highly variable with a negative mean value of -2.15 m w.e. (100 m)-1 over 2002
Thurman, E Michael; Ferrer, Imma; Zavitsanos, Paul; Zweigenbaum, Jerry A
2013-09-15
Imidacloprid is a potent and widely used insecticide on vegetable crops, such as onion (Allium cepa L.). Because of possible toxicity to beneficial insects, imidacloprid and several metabolites have raised safety concerns for pollenating insects, such as honey bees. Thus, imidacloprid metabolites continue to be an important subject for new methods that better understand its dissipation and fate in plants, such as onions. One month after a single addition of imidacloprid to soil containing onion plants, imidacloprid and its metabolites were extracted from pulverized onion with a methanol/water-buffer mixture and analyzed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS) using a labeled imidacloprid internal standard and tandem mass spectrometric (MS/MS) analysis. Accurate mass tools were developed and applied to detect seven new metabolites of imidacloprid with the goal to better understand its fate in onion. The accurate mass tools include: database searching, diagnostic ions, chlorine mass filters, Mass Profiler software, and manual use of metabolic analogy. The new metabolites discovered included an amine reduction product (m/z 226.0854), and its methylated analogue (m/z 240.1010), and five other metabolites, all of unknown toxicity to insects. The accurate mass tools were combined with LC/QTOF-MS and were able to detect both known and new metabolites of imidacloprid using fragmentation studies of both parent and labeled standards. New metabolites and their structures were inferred from these MS/MS studies with accurate mass, which makes it possible to better understand imidacloprid metabolism in onion as well as new metabolite targets for toxicity studies. Copyright © 2013 John Wiley & Sons, Ltd.
MASS MEASUREMENTS BY AN ACCURATE AND SENSITIVE SELECTED ION RECORDING TECHNIQUE
Trace-level components of mixtures were successfully identified or confirmed by mass spectrometric accurate mass measurements, made at high resolution with selected ion recording, using GC and LC sample introduction. Measurements were made at 20 000 or 10 000 resolution, respecti...
Yang, Hong; Xing, Yangping; Xie, Ping; Ni, Leyi; Rong, Kewen
2008-02-01
Although studies on carbon burial in lake sediments have shown that lakes are disproportionately important carbon sinks, many studies on gaseous carbon exchange across the water-air interface have demonstrated that lakes are supersaturated with CO(2) and CH(4) causing a net release of CO(2) and CH(4) to the atmosphere. In order to more accurately estimate the net carbon source/sink function of lake ecosystems, a more comprehensive carbon budget is needed, especially for gaseous carbon exchange across the water-air interface. Using two methods, overall mass balance and gas exchange and carbon burial balance, we assessed the carbon source/sink function of Lake Donghu, a subtropical, eutrophic lake, from April 2003 to March 2004. With the overall mass balance calculations, total carbon input was 14 905 t, total carbon output was 4950 t, and net carbon budget was +9955 t, suggesting that Lake Donghu was a great carbon sink. For the gas exchange and carbon burial balance, gaseous carbon (CO(2) and CH(4)) emission across the water-air interface totaled 752 t while carbon burial in the lake sediment was 9477 t. The ratio of carbon emission into the atmosphere to carbon burial into the sediment was only 0.08. This low ratio indicates that Lake Donghu is a great carbon sink. Results showed good agreement between the two methods with both showing Lake Donghu to be a great carbon sink. This results from the high primary production of Lake Donghu, substantive allochthonous carbon inputs and intensive anthropogenic activity. Gaseous carbon emission accounted for about 15% of the total carbon output, indicating that the total output would be underestimated without including gaseous carbon exchange.
Mass Balance of a Maritime Glacier on the Southeast Tibetan Plateau and Its Climatic Sensitivity
NASA Astrophysics Data System (ADS)
Yang, W.
2014-12-01
Based on glacio-meteorological measurements and mass-balance stake records during the five-year period of 2005-2010 on the southeast Tibetan Plateau, an energy-mass balance model was applied to study the surface mass balance of the Parlung No. 94 Glacier, as well as its response to regional climate conditions. The primary physical parameters involved in the model were locally calibrated by using relevant glacio-meteorological datasets. The good agreement between the snowpack height/mass balance simulations and the in-situ measurements available from a total of 12 monitoring stakes over this glacier confirmed the satisfactory performance of the energy-mass balance model. Results suggested that the recent state of the Parlung No. 94 Glacier was far removed from the 'ideal' climatic regime leading to zero mass balance, with its annual mass balance of approximately -0.9 m w.e. during 2005-2010. Climatic sensitivity experiments were also carried out to interpret the observed mass-balance changes, and the experiments demonstrated that the maritime glaciers concerned herein were theoretically more vulnerable to ongoing climate warming on the Tibetan Plateau than potential changes in the amount of precipitation. A plausible causal explanation for the recent glacier shrinkage in this region was concerned with the increasing air temperature. Moreover, both the mass balance simulations and the field measurements indicated that the mass accumulation over this maritime glacier occurred primarily in the boreal spring. Such "spring-accumulation type" glaciers are presumed to be distributed mainly within a narrow wedge-shaped region along the Brahmaputra River. Climatic sensitivities of the glacier mass balanceare also found to be closely linked to the regional precipitation seasonality that is simultaneously modulated by various atmospheric circulation patterns, such as the southern westerlies, the Bay of Bengal vortex in the spring season and the Indian monsoon in the summer
Land motion due to 20th century mass balance of the Greenland Ice Sheet
NASA Astrophysics Data System (ADS)
Kjeldsen, K. K.; Khan, S. A.
2017-12-01
Quantifying the contribution from ice sheets and glaciers to past sea level change is of great value for understanding sea level projections into the 21st century. However, quantifying and understanding past changes are equally important, in particular understanding the impact in the near-field where the signal is highest. We assess the impact of 20th century mass balance of the Greenland Ice Sheet on land motion using results from Kjeldsen et al, 2015. These results suggest that the ice sheet on average lost a minimum of 75 Gt/yr, but also show that the mass balance was highly spatial- and temporal variable, and moreover that on a centennial time scale changes were driven by a decreasing surface mass balance. Based on preliminary results we discuss land motion during the 20th century due to mass balance changes and the driving components surface mass balance and ice dynamics.
Measuring air-water interfacial area for soils using the mass balance surfactant-tracer method.
Araujo, Juliana B; Mainhagu, Jon; Brusseau, Mark L
2015-09-01
There are several methods for conducting interfacial partitioning tracer tests to measure air-water interfacial area in porous media. One such approach is the mass balance surfactant tracer method. An advantage of the mass-balance method compared to other tracer-based methods is that a single test can produce multiple interfacial area measurements over a wide range of water saturations. The mass-balance method has been used to date only for glass beads or treated quartz sand. The purpose of this research is to investigate the effectiveness and implementability of the mass-balance method for application to more complex porous media. The results indicate that interfacial areas measured with the mass-balance method are consistent with values obtained with the miscible-displacement method. This includes results for a soil, for which solid-phase adsorption was a significant component of total tracer retention. Copyright © 2015 Elsevier Ltd. All rights reserved.
Modeling and Understanding the Mass Balance of Himalayan Glaciers
NASA Astrophysics Data System (ADS)
Rengaraju, S.; Achutarao, K. M.
2017-12-01
Changes in glaciers are among the most visible manifestations of a changing climate. Retreating glaciers have significant impacts on global sea-level rise and stream flow of rivers. Modeling the response of glaciers to climate change is important for many reasons including predicting changes in global sea level and water resources. The mass balance of a glacier provides a robust way of ascertaining whether there has been a net loss or gain of ice from the glacier. The mass balance reflects all of the meteorological forcing of the glacier - from the accumulation of snow and the combined losses from ablation and sublimation. The glaciers in the Himalayan region are considered sensitive to climate change and their fate under climate change is critical to the billions of humans that rely on rivers originating from these glaciers. Owing to complex terrain and harsh climate, Himalayan glaciers have historically been poorly monitored and this makes it harder to understand and predict their fate.In this study we model the observed mass balance of Himalayan glaciers using the methods of Radic and Hock (2011) and analyze the response to future changes in climate based on the model projections from the Coupled Model Intercomparison Project Phase-5 (CMIP5; Taylor et al., 2012). We make use of available observations of mass balance from various sources for 14 glaciers across the Himalayas. These glaciers are located across distinct climatic conditions - from the Karakoram and Hindu Kush in the West that are fed by winter precipitation caused by westerly disturbances to the Eastern Himalayas where the summer monsoon provides the bulk of the precipitation. For the historical observed period, we use the ECMWF Re-Analysis (ERA-40) for temperature and VASClimO (GPCC) data at 2.5°x2.5° resolution to calibrate the mass balance model. We evaluate the CMIP5 model simulations for their fidelity in capturing the distinct climatic conditions across the Himalayas in order to select
Hypsometric control on glacier mass balance sensitivity in Alaska
NASA Astrophysics Data System (ADS)
McGrath, D.; Sass, L.; Arendt, A. A.; O'Neel, S.; Kienholz, C.; Larsen, C.; Burgess, E. W.
2015-12-01
Mass loss from glaciers in Alaska is dominated by strongly negative surface balances, particularly on small, continental glaciers but can be highly variable from glacier to glacier. Glacier hypsometry can exert significant control on mass balance sensitivity, particularly if the equilibrium line altitude (ELA) is in a broad area of low surface slope. In this study, we explore the spatial variability in glacier response to future climate forcings on the basis of hypsometry. We first derive mass balance sensitivities (30-70 m ELA / 1° C and 40-90 m ELA / 50% decrease in snow accumulation) from the ~50-year USGS Benchmark glaciers mass balance record. We subsequently assess mean climate fields in 2090-2100 derived from the IPCC AR5/CMIP5 RCP 6.0 5-model mean. Over glaciers in Alaska, we find 2-4° C warming and 10-20% increase in precipitation relative to 2006-2015, but a corresponding 0-50% decrease in snow accumulation due to rising temperatures. We assess changes in accumulation area ratios (AAR) to a rising ELA using binned individual glacier hypsometries. For an ELA increase of 150 m, the mean statewide AAR drops by 0.45, representing a 70% reduction in accumulation area on an individual glacier basis. Small, interior glaciers are the primary drivers of this reduction and for nearly 25% of all glaciers, the new ELA exceeds the glacier's maximum elevation, portending eventual loss. The loss of small glaciers, particularly in the drier interior of Alaska will significantly modify streamflow properties (flashy hydrographs, earlier and reduced peak flows, increased interannual variability, warmer temperatures) with poorly understood downstream ecosystem and oceanographic impacts.
Improving the XAJ Model on the Basis of Mass-Energy Balance
NASA Astrophysics Data System (ADS)
Fang, Yuanhao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco
2014-11-01
Introduction: The Xin'anjiang(XAJ) model is a conceptual model developed by the group led by Prof. Ren-Jun Zhao, which takes the pan evaporation as one of its input and then computes the effective evapotranspiration (ET) of the catchment by mass balance. Such scheme can ensure a good performance of discharge simulation but has obvious defects, one of which is that the effective ET is spatially-constant over the computation unit, neglecting the spatial variation of variables that influence the effective ET and therefore the simulation of ET and SM by the XAJ model, comparing with discharge, is less reliable. In this study, The XAJ model was improved to employ both energy and mass balance to compute the ET following the energy-mass balance scheme of FEST-EWB. model.
Improving the XAJ Model on the Basis of Mass-Energy Balance
NASA Astrophysics Data System (ADS)
Fang, Yuanghao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco
2014-11-01
The Xin’anjiang(XAJ) model is a conceptual model developed by the group led by Prof. Ren-Jun Zhao, which takes the pan evaporation as one of its input and then computes the effective evapotranspiration (ET) of the catchment by mass balance. Such scheme can ensure a good performance of discharge simulation but has obvious defects, one of which is that the effective ET is spatially-constant over the computation unit, neglecting the spatial variation of variables that influence the effective ET and therefore the simulation of ET and SM by the XAJ model, comparing with discharge, is less reliable. In this study, The XAJ model was improved to employ both energy and mass balance to compute the ET following the energy-mass balance scheme of FEST-EWB. model.
NASA Astrophysics Data System (ADS)
Belart, Joaquín M. C.; Berthier, Etienne; Magnússon, Eyjólfur; Anderson, Leif S.; Pálsson, Finnur; Thorsteinsson, Thorsteinn; Howat, Ian M.; Aðalgeirsdóttir, Guðfinna; Jóhannesson, Tómas; Jarosch, Alexander H.
2017-06-01
Sub-meter resolution, stereoscopic satellite images allow for the generation of accurate and high-resolution digital elevation models (DEMs) over glaciers and ice caps. Here, repeated stereo images of Drangajökull ice cap (NW Iceland) from Pléiades and WorldView2 (WV2) are combined with in situ estimates of snow density and densification of firn and fresh snow to provide the first estimates of the glacier-wide geodetic winter mass balance obtained from satellite imagery. Statistics in snow- and ice-free areas reveal similar vertical relative accuracy (< 0.5 m) with and without ground control points (GCPs), demonstrating the capability for measuring seasonal snow accumulation. The calculated winter (14 October 2014 to 22 May 2015) mass balance of Drangajökull was 3.33 ± 0.23 m w.e. (meter water equivalent), with ∼ 60 % of the accumulation occurring by February, which is in good agreement with nearby ground observations. On average, the repeated DEMs yield 22 % less elevation change than the length of eight winter snow cores due to (1) the time difference between in situ and satellite observations, (2) firn densification and (3) elevation changes due to ice dynamics. The contributions of these three factors were of similar magnitude. This study demonstrates that seasonal geodetic mass balance can, in many areas, be estimated from sub-meter resolution satellite stereo images.
Pereira, Camila; Silva, Rubens A da; de Oliveira, Marcio R; Souza, Rejane D N; Borges, Renata J; Vieira, Edgar R
2018-05-01
The purpose of this study was to evaluate the impact of body mass index (BMI) and fat mass on balance force platform measurements in older adults. The sample consisted of 257 participants who were stratified into four groups by BMI: low weight, normal weight, pre-obesity and obesity. For fat mass variables, older individuals were classified into low and high-fat mass. All groups investigated performed three trials of one-legged stance balance on a force platform. Center of pressure (COP) domain parameters were computed from the mean across trials. Analysis of variance results revealed no significant interactions for groups and sexes for all COP parameters. Comparable balance results were found for BMI and fat groups for all COP parameters. A statistical effect (P < 0.05) was only reported for sex differences for COP parameters, regardless of BMI and fat mass variables. Overall, women presented better balance than men. In conclusion, BMI and fat mass do not seem to influence the balance of older adults during a one-leg stance task.
Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013.
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 .
Determination of Interannual to Decadal Changes in Ice Sheet Mass Balance from Satellite Altimetry
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Busalacchi, Antonioa J. (Technical Monitor)
2001-01-01
A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the +/- 25% uncertainty in current mass balance corresponds to +/- 2 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. Although the overall ice mass balance and seasonal and inter-annual variations can be derived from time-series of ice surface elevations from satellite altimetry, satellite radar altimeters have been limited in spatial coverage and elevation accuracy. Nevertheless, new data analysis shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. In addition, observed seasonal and interannual variations in elevation demonstrate the potential for relating the variability in mass balance to changes in precipitation, temperature, and melting. From 2001, NASA's ICESat laser altimeter mission will provide significantly better elevation accuracy and spatial coverage to 86 deg latitude and to the margins of the ice sheets. During 3 to 5 years of ICESat-1 operation, an estimate of the overall ice sheet mass balance and sea level contribution will be obtained. The importance of continued ice monitoring after the first ICESat is illustrated by the variability in the area of Greenland surface melt observed over 17-years and its correlation with temperature. In addition, measurement of ice sheet changes, along with measurements of sea level change by a series of ocean altimeters, should enable direct detection of ice level and global sea level correlations.
Mass Balance Analysis of Contaminated Heparin Product
Liu, Zhenling; Xiao, Zhongping; Masuko, Sayaka; Zhao, Wenjing; Sterner, Eric; Bansal, Vinod; Fareed, Jawed; Dordick, Jonathan; Zhang, Fuming; Linhardt, Robert J.
2011-01-01
A quantitative analysis of a recalled contaminated lot of heparin (HP) sodium injection United States Pharmacopeial (USP) was undertaken in response to the controversy regarding the exact nature of the contaminant involved in the HP crisis. A mass balance analysis of the formulated drug product was performed. After freeze-drying, a 1 ml vial for injection afforded 54.8 ± 0.3 mg of dry solids. The excipients, sodium chloride and residual benzyl alcohol, accounted for 11.4 ± 0.5 mg and 0.9 ± 0.5 mg, respectively. Active pharmaceutical ingredient (API) represented 41.5 ± 1.0 mg, corresponding to 75.7 wt% of dry mass. Exhaustive treatment of API with specific enzymes, heparin lyases and/or chondroitin lyases was used to close mass balance. HP represented 30.5 ± 0.5 mg, corresponding to 73.5 wt% of the API. Dermatan sulfate (DS) impurity represented 1.7 ± 0.3 mg, corresponding to 4.1 wt% of the API. Contaminant, 9.3 ± 0.1 mg corresponding to 22.4 wt% of API, was found in the contaminated formulated drug product. The recovery of contaminant was close to quantitative (95.6-100 wt%). A single contaminant was unambiguously identified as oversulfated chondroitin sulfate (OSCS). PMID:20850409
Validation of a robotic balance system for investigations in the control of human standing balance.
Luu, Billy L; Huryn, Thomas P; Van der Loos, H F Machiel; Croft, Elizabeth A; Blouin, Jean-Sébastien
2011-08-01
Previous studies have shown that human body sway during standing approximates the mechanics of an inverted pendulum pivoted at the ankle joints. In this study, a robotic balance system incorporating a Stewart platform base was developed to provide a new technique to investigate the neural mechanisms involved in standing balance. The robotic system, programmed with the mechanics of an inverted pendulum, controlled the motion of the body in response to a change in applied ankle torque. The ability of the robotic system to replicate the load properties of standing was validated by comparing the load stiffness generated when subjects balanced their own body to the robot's mechanical load programmed with a low (concentrated-mass model) or high (distributed-mass model) inertia. The results show that static load stiffness was not significantly (p > 0.05) different for standing and the robotic system. Dynamic load stiffness for the robotic system increased with the frequency of sway, as predicted by the mechanics of an inverted pendulum, with the higher inertia being accurately matched to the load properties of the human body. This robotic balance system accurately replicated the physical model of standing and represents a useful tool to simulate the dynamics of a standing person. © 2011 IEEE
When equal masses don't balance
NASA Astrophysics Data System (ADS)
Newburgh, Ronald; Peidle, Joseph; Rueckner, Wolfgang
2004-05-01
We treat a modified Atwood's machine in which equal masses do not balance because of being in an accelerated frame of reference. Analysis of the problem illuminates the meaning of inertial forces, d'Alembert's principle, the use of free-body diagrams and the selection of appropriate systems for the diagrams. In spite of the range of these applications the analysis does not require calculus, so the ideas are accessible even to first-year students.
NASA Astrophysics Data System (ADS)
Chandrasekharan, Anita; Ramsankaran, Raaj
2017-04-01
The current study aims at modelling glacier mass balances over Chhota Shigiri glacier (32.28o N; 77.58° E) in Himachal Pradesh, India using the Equilibrium Line Altitude (ELA) gradient approach proposed by Rabatel et al. (2005). The model requires yearly ELA, average mass balance and mass balance gradient to estimate annual mass balance of a glacier which can be obtained either through field measurements or remote sensing observations. However, in view of the general scenario of lack of field data for Himalayan glaciers, in this study the model has been applied only using the inputs derived through multi-temporal satellite remote sensing observations thus eliminating the need for any field measurements. Preliminary analysis show that the obtained results are comparable with the observed field mass balance. The results also demonstrate that this approach with remote sensing inputs has potential to be used for glacier mass balance estimations provided good quality multi-temporal remote sensing dataset are available.
A MASS BALANCE OF SURFACE WATER GENOTOXICITY IN PROVIDENCE RIVER (RHODE ISLAND USA)
White and Rasmussen (Mutation Res. 410:223-236) used a mass balance approach to demonstrate that over 85% of the total genotoxic loading to the St. Lawrence River at Montreal is non-industrial. To validate the mass balance approach and investigate the sources of genotoxins in sur...
Diagnosing the decline in climatic mass balance of glaciers in Svalbard over 1957-2014
NASA Astrophysics Data System (ADS)
Ims Østby, Torbjørn; Vikhamar Schuler, Thomas; Ove Hagen, Jon; Hock, Regine; Kohler, Jack; Reijmer, Carleen H.
2017-01-01
Estimating the long-term mass balance of the high-Arctic Svalbard archipelago is difficult due to the incomplete geodetic and direct glaciological measurements, both in space and time. To close these gaps, we use a coupled surface energy balance and snow pack model to analyse the mass changes of all Svalbard glaciers for the period 1957-2014. The model is forced by ERA-40 and ERA-Interim reanalysis data, downscaled to 1 km resolution. The model is validated using snow/firn temperature and density measurements, mass balance from stakes and ice cores, meteorological measurements, snow depths from radar profiles and remotely sensed surface albedo and skin temperatures. Overall model performance is good, but it varies regionally. Over the entire period the model yields a climatic mass balance of 8.2 cm w. e. yr-1, which corresponds to a mass input of 175 Gt. Climatic mass balance has a linear trend of -1.4 ± 0.4 cm w. e. yr-2 with a shift from a positive to a negative regime around 1980. Modelled mass balance exhibits large interannual variability, which is controlled by summer temperatures and further amplified by the albedo feedback. For the recent period 2004-2013 climatic mass balance was -21 cm w. e. yr-1, and accounting for frontal ablation estimated by Błaszczyk et al.(2009) yields a total Svalbard mass balance of -39 cm w. e. yr-1 for this 10-year period. In terms of eustatic sea level, this corresponds to a rise of 0.037 mm yr-1. Refreezing of water in snow and firn is substantial at 22 cm w. e. yr-1 or 26 % of total annual accumulation. However, as warming leads to reduced firn area over the period, refreezing decreases both absolutely and relative to the total accumulation. Negative mass balance and elevated equilibrium line altitudes (ELAs) resulted in massive reduction of the thick (> 2 m) firn extent and an increase in the superimposed ice, thin (< 2 m) firn and bare ice extents. Atmospheric warming also leads to a marked change in the thermal regime
Glaciological measurements and mass balances from Sperry Glacier, Montana, USA, years 2005-2015
NASA Astrophysics Data System (ADS)
Clark, Adam M.; Fagre, Daniel B.; Peitzsch, Erich H.; Reardon, Blase A.; Harper, Joel T.
2017-01-01
Glacier mass balance measurements help to provide an understanding of the behavior of glaciers and their response to local and regional climate. In 2005 the United States Geological Survey established a surface mass balance monitoring program on Sperry Glacier, Montana, USA. This project is the first quantitative study of mass changes of a glacier in the US northern Rocky Mountains and continues to the present. The following paper describes the methods used during the first 11 years of measurements and reports the associated results. From 2005 to 2015, Sperry Glacier had a cumulative mean mass balance loss of 4.37 m w.e. (water equivalent). The mean winter, summer, and annual glacier-wide mass balances were 2.92, -3.41, and -0.40 m w.e. yr-1 respectively. We derive these cumulative and mean results from an expansive data set of snow depth, snow density, and ablation measurements taken at selected points on the glacier. These data allow for the determination of mass balance point values and a time series of seasonal and annual glacier-wide mass balances for all 11 measurement years. We also provide measurements of glacier extent and accumulation areas for select years. All data have been submitted to the World Glacier Monitoring Service and are available at doi:10.5904/wgms-fog-2016-08. This foundational work provides valuable insight about Sperry Glacier and supplies additional data to the worldwide record of glaciers measured using the glaciological method. Future research will focus on the processes that control accumulation and ablation patterns across the glacier. Also we plan to examine the uncertainties related to our methods and eventually quantify a more robust estimate of error associated with our results.
NASA Astrophysics Data System (ADS)
Visnjevic, Vjeran; Herman, Frédéric; Licul, Aleksandar
2016-04-01
With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. We recently developed a model that describes large-scale erosion and its response to climate and dynamical changes with the application to the Alps for the LGM period. Here we will present an inverse approach we have recently developed to infer the LGM mass balance from known ice extent data, focusing on a glacier or ice cap. The ice flow model is developed using the shallow ice approximation and the developed codes are accelerated using GPUs capabilities. The mass balance field is the constrained variable defined by the balance rate β and the equilibrium line altitude (ELA), where c is the cutoff value: b = max(βṡ(S(z) - ELA), c) We show that such a mass balance can be constrained from the observed past ice extent and ice thickness. We are also investigating several different geostatistical methods to constrain spatially variable mass balance, and derive uncertainties on each of the mass balance parameters.
Re-analysis of Alaskan benchmark glacier mass-balance data using the index method
Van Beusekom, Ashely E.; O'Nell, Shad R.; March, Rod S.; Sass, Louis C.; Cox, Leif H.
2010-01-01
At Gulkana and Wolverine Glaciers, designated the Alaskan benchmark glaciers, we re-analyzed and re-computed the mass balance time series from 1966 to 2009 to accomplish our goal of making more robust time series. Each glacier's data record was analyzed with the same methods. For surface processes, we estimated missing information with an improved degree-day model. Degree-day models predict ablation from the sum of daily mean temperatures and an empirical degree-day factor. We modernized the traditional degree-day model and derived new degree-day factors in an effort to match the balance time series more closely. We estimated missing yearly-site data with a new balance gradient method. These efforts showed that an additional step needed to be taken at Wolverine Glacier to adjust for non-representative index sites. As with the previously calculated mass balances, the re-analyzed balances showed a continuing trend of mass loss. We noted that the time series, and thus our estimate of the cumulative mass loss over the period of record, was very sensitive to the data input, and suggest the need to add data-collection sites and modernize our weather stations.
pyQms enables universal and accurate quantification of mass spectrometry data.
Leufken, Johannes; Niehues, Anna; Sarin, L Peter; Wessel, Florian; Hippler, Michael; Leidel, Sebastian A; Fufezan, Christian
2017-10-01
Quantitative mass spectrometry (MS) is a key technique in many research areas (1), including proteomics, metabolomics, glycomics, and lipidomics. Because all of the corresponding molecules can be described by chemical formulas, universal quantification tools are highly desirable. Here, we present pyQms, an open-source software for accurate quantification of all types of molecules measurable by MS. pyQms uses isotope pattern matching that offers an accurate quality assessment of all quantifications and the ability to directly incorporate mass spectrometer accuracy. pyQms is, due to its universal design, applicable to every research field, labeling strategy, and acquisition technique. This opens ultimate flexibility for researchers to design experiments employing innovative and hitherto unexplored labeling strategies. Importantly, pyQms performs very well to accurately quantify partially labeled proteomes in large scale and high throughput, the most challenging task for a quantification algorithm. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
The Greenland Ice Sheet's surface mass balance in a seasonally sea ice-free Arctic
NASA Astrophysics Data System (ADS)
Day, J. J.; Bamber, J. L.; Valdes, P. J.
2013-09-01
General circulation models predict a rapid decrease in sea ice extent with concurrent increases in near-surface air temperature and precipitation in the Arctic over the 21st century. This has led to suggestions that some Arctic land ice masses may experience an increase in accumulation due to enhanced evaporation from a seasonally sea ice-free Arctic Ocean. To investigate the impact of this phenomenon on Greenland Ice Sheet climate and surface mass balance (SMB), a regional climate model, HadRM3, was used to force an insolation-temperature melt SMB model. A set of experiments designed to investigate the role of sea ice independently from sea surface temperature (SST) forcing are described. In the warmer and wetter SI + SST simulation, Greenland experiences a 23% increase in winter SMB but 65% reduced summer SMB, resulting in a net decrease in the annual value. This study shows that sea ice decline contributes to the increased winter balance, causing 25% of the increase in winter accumulation; this is largest in eastern Greenland as the result of increased evaporation in the Greenland Sea. These results indicate that the seasonal cycle of Greenland's SMB will increase dramatically as global temperatures increase, with the largest changes in temperature and precipitation occurring in winter. This demonstrates that the accurate prediction of changes in sea ice cover is important for predicting Greenland SMB and ice sheet evolution.
LAKE MICHIGAN MASS BALANCE STUDY: PROGNOSIS FOR PCBS
The Lake Michigan Mass Balance Study was conducted to measure and model nutrients, atrazine, PCBs, trans-nonachlor, and mercury to gain a better understanding of the transport and fate of these substances within the system and to aid managers in the environmental decision-making ...
CHEMICAL MASS BALANCE MODEL: EPA-CMB8.2
The Chemical Mass Balance (CMB) method has been a popular approach for receptor modeling of ambient air pollutants for over two decades. For the past few years the U.S. Environmental Protection Agency's Office of Research and Development (ORD) and Office of Air Quality Plannin...
Autonomous Ice Mass Balance Buoys for Seasonal Sea Ice
NASA Astrophysics Data System (ADS)
Whitlock, J. D.; Planck, C.; Perovich, D. K.; Parno, J. T.; Elder, B. C.; Richter-Menge, J.; Polashenski, C. M.
2017-12-01
The ice mass-balance represents the integration of all surface and ocean heat fluxes and attributing the impact of these forcing fluxes on the ice cover can be accomplished by increasing temporal and spatial measurements. Mass balance information can be used to understand the ongoing changes in the Arctic sea ice cover and to improve predictions of future ice conditions. Thinner seasonal ice in the Arctic necessitates the deployment of Autonomous Ice Mass Balance buoys (IMB's) capable of long-term, in situ data collection in both ice and open ocean. Seasonal IMB's (SIMB's) are free floating IMB's that allow data collection in thick ice, thin ice, during times of transition, and even open water. The newest generation of SIMB aims to increase the number of reliable IMB's in the Arctic by leveraging inexpensive commercial-grade instrumentation when combined with specially developed monitoring hardware. Monitoring tasks are handled by a custom, expandable data logger that provides low-cost flexibility for integrating a large range of instrumentation. The SIMB features ultrasonic sensors for direct measurement of both snow depth and ice thickness and a digital temperature chain (DTC) for temperature measurements every 2cm through both snow and ice. Air temperature and pressure, along with GPS data complete the Arctic picture. Additionally, the new SIMB is more compact to maximize deployment opportunities from multiple types of platforms.
Josberger, Edward G.; Bidlake, William R.
2010-01-01
The long-term USGS measurement and reporting of mass balance at South Cascade Glacier was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier air temperature and gaged precipitation at a remote site. Mass balance modeling was used with glaciological measurements to estimate dates and magnitudes of critical mass balance phenomena. In support of the modeling, a detailed analysis was made of the "glacier cooling effect" that reduces summer air temperature near the ice surface as compared to that predicted on the basis of a spatially uniform temperature lapse rate. The analysis was based on several years of data from measurements of near-surface air temperature on the glacier. The 2006 and 2007 winter balances of South Cascade Glacier, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer balances were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net balances were -1.59 and -0.22 mWE. PDF version of a presentation on the mass balance of South Cascade Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.
The mass balance of the ice plain of Ice Stream B and Crary Ice Rise
NASA Technical Reports Server (NTRS)
Bindschadler, Robert
1993-01-01
The region in the mouth of Ice Stream B (the ice plain) and that in the vicinity of Crary Ice Rise are experiencing large and rapid changes. Based on velocity, ice thickness, and accumulation rate data, the patterns of net mass balance in these regions were calculated. Net mass balance, or the rate of ice thickness change, was calculated as the residual of all mass fluxes into and out of subregions (or boxes). Net mass balance provides a measure of the state of health of the ice sheet and clues to the current dynamics.
Method of Manufacturing a Micromechanical Oscillating Mass Balance
NASA Technical Reports Server (NTRS)
Altemir, David A. (Inventor)
1999-01-01
A micromechanical oscillating mass balance and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers.The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.
Gulkana Glacier, Alaska-Mass balance, meteorology, and water measurements, 1997-2001
March, Rod S.; O'Neel, Shad
2011-01-01
The measured winter snow, maximum winter snow, net, and annual balances for 1997-2001 in the Gulkana Glacier basin are determined at specific points and over the entire glacier area using the meteorological, hydrological, and glaciological data. We provide descriptions of glacier geometry to aid in estimation of conventional and reference surface mass balances and descriptions of ice motion to aid in the understanding of the glacier's response to its changing geometry. These data provide annual estimates for area altitude distribution, equilibrium line altitude, and accumulation area ratio during the study interval. New determinations of historical area altitude distributions are given for 1900 and annually from 1966 to 2001. As original weather instrumentation is nearing the end of its deployment lifespan, we provide new estimates of overlap comparisons and precipitation catch efficiency. During 1997-2001, Gulkana Glacier showed a continued and accelerated negative mass balance trend, especially below the equilibrium line altitude where thinning was pronounced. Ice motion also slowed, which combined with the negative mass balance, resulted in glacier retreat under a warming climate. Average annual runoff augmentation by glacier shrinkage for 1997-2001 was 25 percent compared to the previous average of 13 percent, in accordance with the measured glacier volume reductions.
NASA Astrophysics Data System (ADS)
Cullen, N. J.; Anderson, B.; Sirguey, P. J.; Stumm, D.; Mackintosh, A.; Conway, J. P.; Horgan, H. J.; Dadic, R.; Fitzsimons, S.; Lorrey, A.
2016-12-01
Recognizing the scarcity of glacier mass balance data in the Southern Hemisphere, a mass balance measurement program was started at Brewster Glacier in 2004. Evolution of the measurement regime over the 11 years of data recorded means there are differences in the spatial density of data obtained. To ensure the temporal integrity of the dataset a new, geostatistical approach has been developed to calculate mass balance. Spatial co-variance between elevation and snow depth has enabled a digital elevation model to be used in a co-kriging approach to develop a snow depth index (SDI). By capturing the observed spatial variability in snow depth, the SDI is a more reliable predictor than elevation and is used to adjust each year of measurements consistently despite variability in sampling spatial density. The SDI also resolves the spatial structure of summer balance better than elevation. Co-kriging is used again to spatially interpolate a derived mean summer balance index using SDI as a co-variate, which yields a spatial predictor for summer balance. A similar approach is also used to create a predictor for annual balance, which allows us to revisit years where summer balance was not obtained. The average glacier-wide surface winter, summer and annual mass balances over the period 2005-2015 are 2484, -2586, and -102 mm w.e., respectively, with changes in summer balance explaining most of the variability in annual balance. On the whole, there is good agreement between our ELA and AAR values and those derived from the end-of-summer snowline (EOSS) program, though discrepancies in some years cannot be fully accounted for. A mass balance map of Brewster Glacier in an equilibrium state, which by definition has a glacier-wide mass balance equal to zero (a balanced-budget), is used to calculate values of ELA (1923 ±25 m) and AAR (0.40) representative of the observational period. The relationships between mass balance and ELA/AAR are explored, demonstrating they are mostly
Antarctic and Greenland ice sheet mass balance products from satellite gravimetry
NASA Astrophysics Data System (ADS)
Horwath, Martin; Groh, Andreas; Horvath, Alexander; Forsberg, René; Meister, Rakia; Barletta, Valentina R.; Shepherd, Andrew
2017-04-01
Because of their important role in the Earth's climate system, ESA's Climate Change Initiative (CCI) has identified both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS) as Essential Climate Variables (ECV). Since respondents of a user survey indicated that the ice sheet mass balance is one of the most important ECV data products needed to better understand climate change, the AIS_cci and the GIS_cci project provide Gravimetric Mass Balance (GMB) products based on satellite gravimetry data. The GMB products are derived from GRACE (Gravity Recovery and Climate Experiment) monthly solutions of release ITSG-Grace2016 produced at TU Graz. GMB basin products (i.e. time series of monthly mass changes for the entire ice sheets and selected drainage basins) and GMB gridded products (e.g. mass balance estimates with a formal resolution of about 50km, covering the entire ice sheets) are generated for the period from 2002 until present. The first GMB product was released in mid 2016. Here we present an extended and updated version of the ESA CCI GMB products, which are freely available through data portals hosted by the projects (https://data1.geo.tu-dresden.de/ais_gmb, http://products.esa-icesheets-cci.org/products/downloadlist/GMB). Since the initial product release, the applied processing strategies have been improved in order to further reduce GRACE errors and to enhance the separation of signals super-imposed to the ice mass changes. While a regional integration approach is used by the AIS_cci project, the GMB products of the GIS_cci project are derived using a point mass inversion. The differences between both approaches are investigated through the example of the GIS, where an alternative GMB product was generated using the regional integration approach implemented by the AIS_cci. Finally, we present the latest mass balance estimates for both ice sheets as well as their corresponding contributions to global sea level rise.
Mass-balance approach for assessing nitrate flux intidal wetlands -- lessons learned
Field experiments were carried out in 2010 and 2011 to assess the nitrate balance in a small tidal slough located in the Yaquina Estuary, Oregon. In 2010 we used a whole-slough, mass-balance approach, while a smaller scale, flume-like experiment in a tidal channel with a dense ...
Accurate mass and velocity functions of dark matter haloes
NASA Astrophysics Data System (ADS)
Comparat, Johan; Prada, Francisco; Yepes, Gustavo; Klypin, Anatoly
2017-08-01
N-body cosmological simulations are an essential tool to understand the observed distribution of galaxies. We use the MultiDark simulation suite, run with the Planck cosmological parameters, to revisit the mass and velocity functions. At redshift z = 0, the simulations cover four orders of magnitude in halo mass from ˜1011M⊙ with 8783 874 distinct haloes and 532 533 subhaloes. The total volume used is ˜515 Gpc3, more than eight times larger than in previous studies. We measure and model the halo mass function, its covariance matrix w.r.t halo mass and the large-scale halo bias. With the formalism of the excursion-set mass function, we explicit the tight interconnection between the covariance matrix, bias and halo mass function. We obtain a very accurate (<2 per cent level) model of the distinct halo mass function. We also model the subhalo mass function and its relation to the distinct halo mass function. The set of models obtained provides a complete and precise framework for the description of haloes in the concordance Planck cosmology. Finally, we provide precise analytical fits of the Vmax maximum velocity function up to redshift z < 2.3 to push for the development of halo occupation distribution using Vmax. The data and the analysis code are made publicly available in the Skies and Universes data base.
Glaciological measurements and mass balances from Sperry Glacier, Montana, USA, years 2005–2015
Clark, Adam; Fagre, Daniel B.; Peitzsch, Erich H.; Reardon, Blase A.; Harper, Joel T.
2017-01-01
Glacier mass balance measurements help to provide an understanding of the behavior of glaciers and their response to local and regional climate. In 2005 the United States Geological Survey established a surface mass balance monitoring program on Sperry Glacier, Montana, USA. This project is the first quantitative study of mass changes of a glacier in the US northern Rocky Mountains and continues to the present. The following paper describes the methods used during the first 11 years of measurements and reports the associated results. From 2005 to 2015, Sperry Glacier had a cumulative mean mass balance loss of 4.37 m w.e. (water equivalent). The mean winter, summer, and annual glacier-wide mass balances were 2.92, −3.41, and −0.40 m w.e. yr−1 respectively. We derive these cumulative and mean results from an expansive data set of snow depth, snow density, and ablation measurements taken at selected points on the glacier. These data allow for the determination of mass balance point values and a time series of seasonal and annual glacier-wide mass balances for all 11 measurement years. We also provide measurements of glacier extent and accumulation areas for select years. All data have been submitted to the World Glacier Monitoring Service and are available at doi:10.5904/wgms-fog-2016-08. This foundational work provides valuable insight about Sperry Glacier and supplies additional data to the worldwide record of glaciers measured using the glaciological method. Future research will focus on the processes that control accumulation and ablation patterns across the glacier. Also we plan to examine the uncertainties related to our methods and eventually quantify a more robust estimate of error associated with our results.
A Simple Watt Balance for the Absolute Determination of Mass
ERIC Educational Resources Information Center
Quinn, Terry; Quinn, Lucas; Davis, Richard
2013-01-01
A watt balance is an electromechanical device that allows a mass to be determined in terms of measurable electrical and mechanical quantities, themselves traceable to the fundamental constants of physics. International plans are well advanced to redefine the unit of mass, the kilogram, in terms of a fixed numerical value for the Planck constant. A…
Mass Balance Modelling of Saskatchewan Glacier, Canada Using Empirically Downscaled Reanalysis Data
NASA Astrophysics Data System (ADS)
Larouche, O.; Kinnard, C.; Demuth, M. N.
2017-12-01
Observations show that glaciers around the world are retreating. As sites with long-term mass balance observations are scarce, models are needed to reconstruct glacier mass balance and assess its sensitivity to climate. In regions with discontinuous and/or sparse meteorological data, high-resolution climate reanalysis data provide a convenient alternative to in situ weather observations, but can also suffer from strong bias due to the spatial and temporal scale mismatch. In this study we used data from the North American Regional Reanalysis (NARR) project with a 30 x 30 km spatial resolution and 3-hour temporal resolution to produce the meteorological forcings needed to drive a physically-based, distributed glacier mass balance model (DEBAM, Hock and Holmgren 2005) for the historical period 1979-2016. A two-year record from an automatic weather station (AWS) operated on Saskatchewan Glacier (2014-2016) was used to downscale air temperature, relative humidity, wind speed and incoming solar radiation from the nearest NARR gridpoint to the glacier AWS site. An homogenized historical precipitation record was produced using data from two nearby, low-elevation weather stations and used to downscale the NARR precipitation data. Three bias correction methods were applied (scaling, delta and empirical quantile mapping - EQM) and evaluated using split sample cross-validation. The EQM method gave better results for precipitation and for air temperature. Only a slight improvement in the relative humidity was obtained using the scaling method, while none of the methods improved the wind speed. The later correlates poorly with AWS observations, probably because the local glacier wind is decoupled from the larger scale NARR wind field. The downscaled data was used to drive the DEBAM model in order to reconstruct the mass balance of Saskatchewan Glacier over the past 30 years. The model was validated using recent snow thickness measurements and previously published geodetic mass
A better GRACE solution for improving the regional Greenland mass balance
NASA Astrophysics Data System (ADS)
Schrama, E.; Xu, Z.
2012-04-01
In most GRACE based researches, a variety of smoothing methods is employed to remove alternating bands of positive and negative stripes stretching in the north-south direction. Many studies have suggested to smooth the GRACE maps, on which mass variations are represented as equivalent water height (EWH). Such maps are capable of exposing the redistribution of earth surface mass over time. In Greenland the shrinking of the ice cap becomes significant in the last decade. Our present study confirms that the dominating melting trends are in the east and southeast coastal zones, however, the smoothed signals along the coastline in these areas do not represent the original but averaged measurements from GRACE satellites which means the signal strength indicating that negative mass variations are mixed with some positive signals that are very close to this area. An exact identification of the topographic edge is not possible and visually the EWH maps appear to be blurred. To improve this, we firstly used spherical harmonic coefficients of GRACE level-2 data from CSR-RL04 and produced a smoothed EWH map. Empirical Orthogonal Functions(EOF)/Principal Component Analysis(PCA) have been introduced as well, in order to extract the melting information associated with the recent warming climate. Next, the Greenland area is redefined by 16 basins and the corresponding melting zones are quantified respectively. Least Squares methods are invoked to interpolate the mass distribution function on each basin. In this way we are able to estimate more accurately regional ice melting rate and we sharpen the EWH map. After comparing our results with a hydrological model the combination SMB - D is established which contains the surface mass balance (SMB) and ice-discharge (D). A general agreement can be reached and it turns out this method is capable to enhance our understanding of the shrinking global cryosphere
Experimental design for evaluating WWTP data by linear mass balances.
Le, Quan H; Verheijen, Peter J T; van Loosdrecht, Mark C M; Volcke, Eveline I P
2018-05-15
A stepwise experimental design procedure to obtain reliable data from wastewater treatment plants (WWTPs) was developed. The proposed procedure aims at determining sets of additional measurements (besides available ones) that guarantee the identifiability of key process variables, which means that their value can be calculated from other, measured variables, based on available constraints in the form of linear mass balances. Among all solutions, i.e. all possible sets of additional measurements allowing the identifiability of all key process variables, the optimal solutions were found taking into account two objectives, namely the accuracy of the identified key variables and the cost of additional measurements. The results of this multi-objective optimization problem were represented in a Pareto-optimal front. The presented procedure was applied to a full-scale WWTP. Detailed analysis of the relation between measurements allowed the determination of groups of overlapping mass balances. Adding measured variables could only serve in identifying key variables that appear in the same group of mass balances. Besides, the application of the experimental design procedure to these individual groups significantly reduced the computational effort in evaluating available measurements and planning additional monitoring campaigns. The proposed procedure is straightforward and can be applied to other WWTPs with or without prior data collection. Copyright © 2018 Elsevier Ltd. All rights reserved.
Leypoldt, John K; Agar, Baris U; Akonur, Alp; Gellens, Mary E; Culleton, Bruce F
2012-11-01
Mathematical models of phosphorus kinetics and mass balance during hemodialysis are in early development. We describe a theoretical phosphorus steady state mass balance model during hemodialysis based on a novel pseudo one-compartment kinetic model. The steady state mass balance model accounted for net intestinal absorption of phosphorus and phosphorus removal by both dialysis and residual kidney function. Analytical mathematical solutions were derived to describe time-dependent intradialytic and interdialytic serum phosphorus concentrations assuming hemodialysis treatments were performed symmetrically throughout a week. Results from the steady state phosphorus mass balance model are described for thrice weekly hemodialysis treatment prescriptions only. The analysis predicts 1) a minimal impact of dialyzer phosphorus clearance on predialysis serum phosphorus concentration using modern, conventional hemodialysis technology, 2) variability in the postdialysis-to-predialysis phosphorus concentration ratio due to differences in patient-specific phosphorus mobilization, and 3) the importance of treatment time in determining the predialysis serum phosphorus concentration. We conclude that a steady state phosphorus mass balance model can be developed based on a pseudo one-compartment kinetic model and that predictions from this model are consistent with previous clinical observations. The predictions from this mass balance model are theoretical and hypothesis-generating only; additional prospective clinical studies will be required for model confirmation.
Accurate EPR radiosensitivity calibration using small sample masses
NASA Astrophysics Data System (ADS)
Hayes, R. B.; Haskell, E. H.; Barrus, J. K.; Kenner, G. H.; Romanyukha, A. A.
2000-03-01
We demonstrate a procedure in retrospective EPR dosimetry which allows for virtually nondestructive sample evaluation in terms of sample irradiations. For this procedure to work, it is shown that corrections must be made for cavity response characteristics when using variable mass samples. Likewise, methods are employed to correct for empty tube signals, sample anisotropy and frequency drift while considering the effects of dose distribution optimization. A demonstration of the method's utility is given by comparing sample portions evaluated using both the described methodology and standard full sample additive dose techniques. The samples used in this study are tooth enamel from teeth removed during routine dental care. We show that by making all the recommended corrections, very small masses can be both accurately measured and correlated with measurements of other samples. Some issues relating to dose distribution optimization are also addressed.
Uncertainty in Modeling Dust Mass Balance and Radiative Forcing from Size Parameterization
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhao, Chun; Chen, Siyu; Leung, Lai-Yung R.
2013-11-05
This study examines the uncertainties in simulating mass balance and radiative forcing of mineral dust due to biases in the aerosol size parameterization. Simulations are conducted quasi-globally (180oW-180oE and 60oS-70oN) using the WRF24 Chem model with three different approaches to represent aerosol size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or 4-bin approaches against a relatively more accurate 8-bin approach in simulating dust mass balance and radiative forcing are identified. Compared to the 8-bin approach, the 4-bin approach simulates similar but coarser size distributions of dust particles in the atmosphere, while the 3-mode pproach retains more finemore » dust particles but fewer coarse dust particles due to its prescribed og of each mode. Although the 3-mode approach yields up to 10 days longer dust mass lifetime over the remote oceanic regions than the 8-bin approach, the three size approaches produce similar dust mass lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the global dust mass lifetime is mainly determined by the dust mass lifetime near the dust source regions. With the same global dust emission (~6000 Tg yr-1), the 8-bin approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust mass loading, respectively. The difference in dust mass loading between the 8-bin approach and the 4-bin or 3-mode approaches has large spatial variations, with generally smaller relative difference (<10%) near the surface over the dust source regions. The three size approaches also result in significantly different dry and wet deposition fluxes and number concentrations of dust. The difference in dust aerosol optical depth (AOD) (a factor of 3) among the three size approaches is much larger than their difference (25%) in dust mass loading. Compared to the 8-bin approach, the 4-bin approach yields stronger dust absorptivity, while the 3
California's Snow Gun and its implications for mass balance predictions under greenhouse warming
NASA Astrophysics Data System (ADS)
Howat, I.; Snyder, M.; Tulaczyk, S.; Sloan, L.
2003-12-01
Precipitation has received limited treatment in glacier and snowpack mass balance models, largely due to the poor resolution and confidence of precipitation predictions relative to temperature predictions derived from atmospheric models. Most snow and glacier mass balance models rely on statistical or lapse rate-based downscaling of general or regional circulation models (GCM's and RCM's), essentially decoupling sub-grid scale, orographically-driven evolution of atmospheric heat and moisture. Such models invariably predict large losses in the snow and ice volume under greenhouse warming. However, positive trends in the mass balance of glaciers in some warming maritime climates, as well as at high elevations of the Greenland Ice Sheet, suggest that increased precipitation may play an important role in snow- and glacier-climate interactions. Here, we present a half century of April snowpack data from the Sierra Nevada and Cascade mountains of California, USA. This high-density network of snow-course data indicates that a gain in winter snow accumulation at higher elevations has compensated loss in snow volume at lower elevations by over 50% and has led to glacier expansion on Mt. Shasta. These trends are concurrent with a region-wide increase in winter temperatures up to 2° C. They result from the orographic lifting and saturation of warmer, more humid air leading to increased precipitation at higher elevations. Previous studies have invoked such a "Snow Gun" effect to explain contemporaneous records of Tertiary ocean warming and rapid glacial expansion. A climatological context of the California's "snow gun" effect is elucidated by correlation between the elevation distribution of April SWE observations and the phase of the Pacific Decadal Oscillation and the El Nino Southern Oscillation, both controlling the heat and moisture delivered to the U.S. Pacific coast. The existence of a significant "Snow Gun" effect presents two challenges to snow and glacier mass
Mass balances of dissolved gases at river network scales across biomes.
NASA Astrophysics Data System (ADS)
Wollheim, W. M.; Stewart, R. J.; Sheehan, K.
2016-12-01
Estimating aquatic metabolism and gas fluxes at broad spatial scales is needed to evaluate the role of aquatic ecosystems in continental carbon cycles. We applied a river network model, FrAMES, to quantify the mass balances of dissolved oxygen at river network scales across five river networks in different biomes. The model accounts for hydrology; spatially varying re-aeration rates due to flow, slope, and water temperature; gas inputs via terrestrial runoff; variation in light due to canopy cover and water depth; benthic gross primary production; and benthic respiration. The model was parameterized using existing groundwater information and empirical relationships of GPP, R, and re-aeration, and was tested using dissolved oxygen patterns measured throughout river networks. We found that during summers, internal aquatic production dominates the river network mass balance of Kings Cr., Konza Prairie, KS (16.3 km2), whereas terrestrial inputs and aeration dominate the network mass balance at Coweeta Cr., Coweeta Forest, NC (15.7 km2). At network scales, both river networks are net heterotrophic, with Coweeta more so than Kings Cr. (P:R 0.6 vs. 0.7, respectively). The river network of Kings Creek showed higher network-scale GPP and R compared to Coweeta, despite having a lower drainage density because streams are on average wider so cumulative benthic surface areas are similar. Our findings suggest that the role of aquatic systems in watershed carbon balances will depend on interactions of drainage density, channel hydraulics, terrestrial vegetation, and biological activity.
Shao, Zhecheng; Wyatt, Mark F; Stein, Bridget K; Brenton, A Gareth
2010-10-30
A method for the accurate mass measurement of negative radical ions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is described. This is an extension to our previously described method for the accurate mass measurement of positive radical ions (Griffiths NW, Wyatt MF, Kean SD, Graham AE, Stein BK, Brenton AG. Rapid Commun. Mass Spectrom. 2010; 24: 1629). The porphyrin standard reference materials (SRMs) developed for positive mode measurements cannot be observed in negative ion mode, so fullerene and fluorinated porphyrin compounds were identified as effective SRMs. The method is of immediate practical use for the accurate mass measurement of functionalised fullerenes, for which negative ion MALDI-TOFMS is the principal mass spectrometry characterisation technique. This was demonstrated by the accurate mass measurement of six functionalised C(60) compounds. Copyright © 2010 John Wiley & Sons, Ltd.
Balance Velocities of the Greenland Ice Sheet
NASA Technical Reports Server (NTRS)
Joughin, Ian; Fahnestock, Mark; Ekholm, Simon; Kwok, Ron
1997-01-01
We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetry data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an ice stream in northeastern Greenland, which was only recently discovered using satellite imagery. Enhanced flow associated with all of the major outlets is clearly visible, although small errors in the source data result in less accurate estimates of the absolute flow speeds. Nevertheless, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning.
Dual-sensor mapping of mass balance on Russia's northernmost ice caps
NASA Astrophysics Data System (ADS)
Nikolskiy, D.; Malinnikov, V.; Sharov, A.; Ukolova, M.
2012-04-01
Mass balance of Russia's northernmost ice caps is poorly known and scarcely mapped. Thorough information about glacier fluctuations in the outer periphery of Russian shelf seas is both lacking and highly desired since it may constitute the relevant benchmark for judging and projecting climate change impacts in the entire Arctic. The present study is focussed on geodetic measurements and medium-scale mapping of the mass balance on a dozen insular ice caps, some large and some smaller, homogeneously situated along the Eurasian boundary of Central Arctic Basin. The study region extends for approx. 2.200 km from Victoria and Arthur islands in the west across Rudolph, Eva-Liv, Ushakova, Schmidt and Komsomolets islands in the north to Bennett and Henrietta islands in the east thereby comprising the most distant and least studied ice caps in the Russian Arctic. The situation of insular ice masses close to the edge of summer minimum sea ice proved helpful in analysing spatial asymmetry of glacier accumulation signal. The overall mapping of glacier elevation changes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1960s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. In total, 14 ERS and 4 TanDEM-X high-quality SAR interferograms of 1995/96 and 2011 were acquired, processed in the standard 2-pass DINSAR manner, geocoded, calibrated, mosaicked and interpreted using reference elevation models and co-located ICESat altimetry data of 2003-2010. The DINSAR analysis revealed the existence of fast-flowing outlet glaciers at Arthur, Rudolph, Eva-Liv and Bennett islands. The calculation of separate mass-balance components is complicated in this case because of generally unknown glacier velocities and ice discharge values for the mid-20
Mass balance assessment for mercury in Lake Champlain
Gao, N.; Armatas, N.G.; Shanley, J.B.; Kamman, N.C.; Miller, E.K.; Keeler, G.J.; Scherbatskoy, T.; Holsen, T.M.; Young, T.; McIlroy, L.; Drake, S.; Olsen, Bill; Cady, C.
2006-01-01
A mass balance model for mercury in Lake Champlain was developed in an effort to understand the sources, inventories, concentrations, and effects of mercury (Hg) contamination in the lake ecosystem. To construct the mass balance model, air, water, and sediment were sampled as a part of this project and other research/monitoring projects in the Lake Champlain Basin. This project produced a STELLA-based computer model and quantitative apportionments of the principal input and output pathways of Hg for each of 13 segments in the lake. The model Hg concentrations in the lake were consistent with measured concentrations. Specifically, the modeling identified surface water inflows as the largest direct contributor of Hg into the lake. Direct wet deposition to the lake was the second largest source of Hg followed by direct dry deposition. Volatilization and sedimentation losses were identified as the two major removal mechanisms. This study significantly improves previous estimates of the relative importance of Hg input pathways and of wet and dry deposition fluxes of Hg into Lake Champlain. It also provides new estimates of volatilization fluxes across different lake segments and sedimentation loss in the lake. ?? 2006 American Chemical Society.
Greenland ice sheet mass balance: a review.
Khan, Shfaqat A; Aschwanden, Andy; Bjørk, Anders A; Wahr, John; Kjeldsen, Kristian K; Kjær, Kurt H
2015-04-01
Over the past quarter of a century the Arctic has warmed more than any other region on Earth, causing a profound impact on the Greenland ice sheet (GrIS) and its contribution to the rise in global sea level. The loss of ice can be partitioned into processes related to surface mass balance and to ice discharge, which are forced by internal or external (atmospheric/oceanic/basal) fluctuations. Regardless of the measurement method, observations over the last two decades show an increase in ice loss rate, associated with speeding up of glaciers and enhanced melting. However, both ice discharge and melt-induced mass losses exhibit rapid short-term fluctuations that, when extrapolated into the future, could yield erroneous long-term trends. In this paper we review the GrIS mass loss over more than a century by combining satellite altimetry, airborne altimetry, interferometry, aerial photographs and gravimetry data sets together with modelling studies. We revisit the mass loss of different sectors and show that they manifest quite different sensitivities to atmospheric and oceanic forcing. In addition, we discuss recent progress in constructing coupled ice-ocean-atmosphere models required to project realistic future sea-level changes.
NASA Astrophysics Data System (ADS)
Vogler, K.; McNeil, C.; Bond, M.; Getraer, B.; Huxley-Reicher, B.; McNamara, G.; Reinhardt-Ertman, T.; Silverwood, J.; Kienholz, C.; Beedle, M. J.
2017-12-01
Glacier-wide annual mass balances (Ba) have been calculated for Taku (726 km2) and Lemon Creek glaciers (10.2 km2) since 1946 and 1953 respectively. These are the longest mass balance records in North America, and the only Ba time-series available for Southeast Alaska, making them particularly valuable for the global glacier mass balance monitoring network. We compared Ba time-series from Taku and Lemon Creek glaciers to Gravity Recovery and Climate Experiment (GRACE) mascon solutions (1352 and 1353) during the 2004-2015 period to assess how well these gravimetric solutions reflect individual glaciological records. Lemon Creek Glacier is a challenging candidate for this comparison because it is small compared to the 12,100 km2 GRACE mascon solutions. Taku Glacier is equally challenging because its mass balance is stable compared to the negative balances dominating its neighboring glaciers. Challenges notwithstanding, a high correlation between the glaciological and gravimetrically-derived Ba for Taku and Lemon Creek glaciers encourage future use of GRACE to measure glacier mass balance. Additionally, we employed high frequency ground penetrating radar (GPR) to measure the variability of accumulation around glaciological sites to assess uncertainty in our glaciological measurements, and the resulting impact to Ba. Finally, we synthesize this comparison of glaciological and gravimetric mass balance solutions with a discussion of potential sources of error in both methods and their combined utility for measuring regional glacier change during the 21st century.
Selenium mass balance in the Great Salt Lake, Utah
Diaz, X.; Johnson, W.P.; Naftz, D.L.
2009-01-01
A mass balance for Se in the south arm of the Great Salt Lake was developed for September 2006 to August 2007 of monitoring for Se loads and removal flows. The combined removal flows (sedimentation and volatilization) totaled to a geometric mean value of 2079??kg Se/yr, with the estimated low value being 1255??kg Se/yr, and an estimated high value of 3143??kg Se/yr at the 68% confidence level. The total (particulates + dissolved) loads (via runoff) were about 1560??kg Se/yr, for which the error is expected to be ?? 15% for the measured loads. Comparison of volatilization to sedimentation flux demonstrates that volatilization rather than sedimentation is likely the major mechanism of selenium removal from the Great Salt Lake. The measured loss flows balance (within the range of uncertainties), and possibly surpass, the measured annual loads. Concentration histories were modeled using a simple mass balance, which indicated that no significant change in Se concentration was expected during the period of study. Surprisingly, the measured total Se concentration increased during the period of the study, indicating that the removal processes operate at their low estimated rates, and/or there are unmeasured selenium loads entering the lake. The selenium concentration trajectories were compared to those of other trace metals to assess the significance of selenium concentration trends. ?? 2008 Elsevier B.V.
NASA Astrophysics Data System (ADS)
Malone, A.
2017-12-01
Quantifying mass balance sensitivity to climate change is essential for forecasting glacier evolution and deciphering climate signals embedded in archives of past glacier changes. Ideally, these quantifications result from decades of field measurement, remote sensing, and a hierarchy modeling approach, but in data-sparse regions, such as the Himalayas and tropical Andes, regional-scale modeling rooted in first principles provides a first-order picture. Previous regional-scaling modeling studies have applied a surface energy and mass balance approach in order to quantify equilibrium line altitude sensitivity to climate change. In this study, an expanded regional-scale surface energy and mass balance model is implemented to quantify glacier-wide mass balance sensitivity to climate change for tropical Andean glaciers. Data from the Randolph Glacier Inventory are incorporated, and additional physical processes are included, such as a dynamic albedo and cloud-dependent atmospheric emissivity. The model output agrees well with the limited mass balance records for tropical Andean glaciers. The dominant climate variables driving interannual mass balance variability differ depending on the climate setting. For wet tropical glaciers (annual precipitation >0.75 m y-1), temperature is the dominant climate variable. Different hypotheses for the processes linking wet tropical glacier mass balance variability to temperature are evaluated. The results support the hypothesis that glacier-wide mass balance on wet tropical glaciers is largely dominated by processes at the lowest elevation where temperature plays a leading role in energy exchanges. This research also highlights the transient nature of wet tropical glaciers - the vast majority of tropical glaciers and a vital regional water resource - in an anthropogenic warming world.
Mercury mass balance in Lake Michigan--the knowns and unknowns
LM2-Mercury, a mercury mass balance model, was developed to simulate and evaluate the transport, fate, and biogeochemical transformations of mercury in Lake Michigan. The model simulates total suspended solids (TSS), disolved organic carbon (DOC), and total, elemental, divalent, ...
NASA Astrophysics Data System (ADS)
Mölg, Thomas; Cullen, Nicolas J.; Kaser, Georg
Broadband radiation schemes (parameterizations) are commonly used tools in glacier mass-balance modelling, but their performance at high altitude in the tropics has not been evaluated in detail. Here we take advantage of a high-quality 2 year record of global radiation (G) and incoming longwave radiation (L↓) measured on Kersten Glacier, Kilimanjaro, East Africa, at 5873 m a.s.l., to optimize parameterizations of G and L↓. We show that the two radiation terms can be related by an effective cloud-cover fraction neff, so G or L↓ can be modelled based on neff derived from measured L↓ or G, respectively. At neff = 1, G is reduced to 35% of clear-sky G, and L↓ increases by 45-65% (depending on altitude) relative to clear-sky L↓. Validation for a 1 year dataset of G and L↓ obtained at 4850 m on Glaciar Artesonraju, Peruvian Andes, yields a satisfactory performance of the radiation scheme. Whether this performance is acceptable for mass-balance studies of tropical glaciers is explored by applying the data from Glaciar Artesonraju to a physically based mass-balance model, which requires, among others, G and L↓ as forcing variables. Uncertainties in modelled mass balance introduced by the radiation parameterizations do not exceed those that can be caused by errors in the radiation measurements. Hence, this paper provides a tool for inclusion in spatially distributed mass-balance modelling of tropical glaciers and/or extension of radiation data when only G or L↓ is measured.
NASA Astrophysics Data System (ADS)
Kent, E. R.; Bailey, S.; Stephens, J.; Horwath, W. R.; Paw U, K.
2013-12-01
Managed decomposition of organic materials is increasingly being used as an alternative waste management option and the resulting compost can be used as a fertilizer and soil amendment in home gardens and agriculture. An additional benefit is the avoidance of methane emissions associated with anaerobic decomposition in landfills. Greenhouse gases are still emitted during the composting process, but few studies have measured emissions from a full-scale windrow of composting green-waste. This study uses a micrometeorological mass balance technique (upwind and downwind vertical profile measurements of trace gas concentrations and wind velocity) to calculate emissions of carbon dioxide, methane, and nitrous oxide from a pile of composting green-waste during the dry season in Northern California. The expected source pattern was observed in measured upwind-downwind concentration differences of all three gases averaged over the study period despite substantial noise seen in the half-hourly emission calculations. Sources of uncertainty are investigated and temporal patterns analyzed. An in-situ zero-source test was conducted to examine the mass balance technique when the source of emissions was removed. Results from the micrometeorological mass balance measurements are compared with measurements taken using the more common open chamber technique.
Glacier mass balance and its potential impacts in the Altai Mountains over the period 1990-2011
NASA Astrophysics Data System (ADS)
Zhang, Yong; Enomoto, Hiroyuki; Ohata, Tetsuo; Kitabata, Hideyuki; Kadota, Tsutomu; Hirabayashi, Yukiko
2017-10-01
The Altai Mountains contain 1281 glaciers covering an area of 1191 km2. These glaciers have undergone significant changes in glacial length and area over the past decade. However, mass changes of these glaciers and their impacts remain poorly understood. Here we present surface mass balances of all glaciers in the region for the period 1990-2011, using a glacier mass-balance model forced by the outputs of a regional climate model. Our results indicate that the mean specific mass balance for the whole region is about -0.69 m w.e. yr-1 over the entire period, and about 81.3% of these glaciers experience negative net mass balance. We detect an accelerated wastage of these glaciers in recent years, and marked differences in mass change and its sensitivity to climate change for different regions and size classes. In particular, higher mass loss and temperature sensitivity are observed for glaciers smaller than 0.5 km2. In addition to temperature rise, a decrease in precipitation in the western part of the region and an increase in precipitation in the eastern part likely contribute to significant sub-region differences in mass loss. With significant glacier wastage, the contribution of all glaciers to regional water resources and sea-level change becomes larger than before, but may not be a potential threat to human populations through impacts on water availability.
Estimation of Greenland's Ice Sheet Mass Balance Using ICESat and GRACE Data
NASA Astrophysics Data System (ADS)
Slobbe, D.; Ditmar, P.; Lindenbergh, R.
2007-12-01
Data of the GRACE gravity mission and the ICESat laser altimetry mission are used to create two independent estimates of Greenland's ice sheet mass balance over the full measurement period. For ICESat data, a processing strategy is developed using the elevation differences of geometrically overlapping footprints of both crossing and repeated tracks. The dataset is cleaned using quality flags defined by the GLAS science team. The cleaned dataset reveals some strong, spatially correlated signals that are shown to be related to physical phenomena. Different processing strategies are used to convert the observed temporal height differences to mass changes for 6 different drainage systems, further divided into a region above and below 2000 meter elevation. The results are compared with other altimetry based mass balance estimates. In general, the obtained results confirm trends discovered by others, but we also show that the choice of processing strategy strongly influences our results, especially for the areas below 2000 meter. Furthermore, GRACE based monthly variations of the Earth's gravity field as processed by CNES, CSR, GFZ and DEOS are used to estimate the mass balance change for North and South Greenland. It is shown that our results are comparable with recently published GRACE estimates (mascon solutions). On the other hand, the estimates based on GRACE data are only partly confirmed by the ICESat estimates. Possible explanations for the obvious differences will be discussed.
Wyatt, Mark F; Stein, Bridget K; Brenton, A Gareth
2006-05-01
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been shown to be an effective technique for the characterization of organometallic, coordination, and highly conjugated compounds. The preferred matrix is 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), with radical ions observed. However, MALDI-TOFMS is generally not favored for accurate mass measurement. A specific method had to be developed for such compounds to assure the quality of our accurate mass results. Therefore, in this preliminary study, two methods of data acquisition, and both even-electron (EE+) ion and odd-electron (OE+.) radical ion mass calibration standards, have been investigated to establish the basic measurement technique. The benefit of this technique is demonstrated for a copper compound for which ions were observed by MALDI, but not by electrospray (ESI) or liquid secondary ion mass spectrometry (LSIMS); a mean mass accuracy error of -1.2 ppm was obtained.
OVERVIEW AND STATUS OF LAKE MICHIGAN MASS BALANCE MODELLING PROJECT
With most of the data available from the Lake Michigan Mass Balance Project field program, the modeling efforts have begun in earnest. The tributary and atmospheric load estimates are or will be completed soon, so realistic simulations for calibration are beginning. A Quality Ass...
A simple, mass balance model of carbon flow in a controlled ecological life support system
NASA Technical Reports Server (NTRS)
Garland, Jay L.
1989-01-01
Internal cycling of chemical elements is a fundamental aspect of a Controlled Ecological Life Support System (CELSS). Mathematical models are useful tools for evaluating fluxes and reservoirs of elements associated with potential CELSS configurations. A simple mass balance model of carbon flow in CELSS was developed based on data from the CELSS Breadboard project at Kennedy Space Center. All carbon reservoirs and fluxes were calculated based on steady state conditions and modelled using linear, donor-controlled transfer coefficients. The linear expression of photosynthetic flux was replaced with Michaelis-Menten kinetics based on dynamical analysis of the model which found that the latter produced more adequate model output. Sensitivity analysis of the model indicated that accurate determination of the maximum rate of gross primary production is critical to the development of an accurate model of carbon flow. Atmospheric carbon dioxide was particularly sensitive to changes in photosynthetic rate. The small reservoir of CO2 relative to large CO2 fluxes increases the potential for volatility in CO2 concentration. Feedback control mechanisms regulating CO2 concentration will probably be necessary in a CELSS to reduce this system instability.
A LEGO Watt balance: An apparatus to determine a mass based on the new SI
NASA Astrophysics Data System (ADS)
Chao, L. S.; Schlamminger, S.; Newell, D. B.; Pratt, J. R.; Seifert, F.; Zhang, X.; Sineriz, G.; Liu, M.; Haddad, D.
2015-11-01
A global effort to redefine our International System of Units (SI) is underway, and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed numerical values of seven reference constants. In particular, the unit of mass (the kilogram) will be realized through a fixed value of the Planck constant h. A so-called watt balance, for example, can then be used to realize the kilogram unit of mass within a few parts in 108. Such a balance has been designed and constructed at the National Institute of Standards and Technology. For educational outreach and to demonstrate the principle, we have constructed a LEGO tabletop watt balance capable of measuring a gram-level masses to 1% relative uncertainty. This article presents the design, construction, and performance of the LEGO watt balance and its ability to determine h.
NASA Technical Reports Server (NTRS)
Sinko, P. J.; Leesman, G. D.; Amidon, G. L.
1993-01-01
A theoretical analysis for estimating the extent of intestinal peptide and peptide analogue absorption was developed on the basis of a mass balance approach that incorporates convection, permeability, and reaction. The macroscopic mass balance analysis (MMBA) was extended to include chemical and enzymatic degradation. A microscopic mass balance analysis, a numerical approach, was also developed and the results compared to the MMBA. The mass balance equations for the fraction of a drug absorbed and reacted in the tube were derived from the general steady state mass balance in a tube: [formula: see text] where M is mass, z is the length of the tube, R is the tube radius, Pw is the intestinal wall permeability, kr is the reaction rate constant, C is the concentration of drug in the volume element over which the mass balance is taken, VL is the volume of the tube, and vz is the axial velocity of drug. The theory was first applied to the oral absorption of two tripeptide analogues, cefaclor (CCL) and cefatrizine (CZN), which degrade and dimerize in the intestine. Simulations using the mass balance equations, the experimental absorption parameters, and the literature stability rate constants yielded a mean estimated extent of CCL (250-mg dose) and CZN (1000-mg dose) absorption of 89 and 51%, respectively, which was similar to the mean extent of absorption reported in humans (90 and 50%). It was proposed previously that 15% of the CCL dose spontaneously degraded systematically; however, our simulations suggest that significant CCL degradation occurs (8 to 17%) presystemically in the intestinal lumen.(ABSTRACT TRUNCATED AT 250 WORDS).
Choi, Ahnryul; Sim, Taeyong; Mun, Joung Hwan
2016-01-01
Golf requires proper dynamic balance to accurately control the club head through a harmonious coordination of each human segment and joint. In this study, we evaluated the ability for dynamic balance during a golf swing by using the centre of mass (COM)-centre of pressure (COP) inclination variables. Twelve professional, 13 amateur and 10 novice golfers participated in this study. Six infrared cameras, two force platforms and SB-Clinic software were used to measure the net COM and COP trajectories. In order to evaluate dynamic balance ability, the COM-COP inclination angle, COM-COP inclination angular velocity and normalised COM-COP inclination angular jerk were used. Professional golfer group revealed a smaller COM-COP inclination angle and angular velocity than novice golfer group in the lead/trail direction (P < 0.01). In the normalised COM-COP inclination angular jerk, the professional golfer group showed a lower value than the other two groups in all directions. Professional golfers tend to exhibit improved dynamic balance, and this can be attributed to the neuromusculoskeletal system that maintains balance with proper postural control. This study has the potential to allow for an evaluation of the dynamic balance mechanism and will provide useful basic information for swing training and prevention of golf injuries.
Mass balance and surface velocity reconstructions of two reference Caucasus glaciers
NASA Astrophysics Data System (ADS)
Rybak, Oleg; Kaminskaia, Mariia; Kutuzov, Stanislav; Lavrentiev, Ivan; Morozova, Polina; Popovnin, Victor; Rybak, Elena
2016-04-01
Total glacial volume of the Greater Caucasus exceeds 40 cubic km and its area exceeds 1 thousand square km. During the 20th century, mountain glaciers at the Greater Caucasus were continuously degrading. According to various estimates, their area reduced more than one-third and their volume almost by half. The process of degradation was accompanied by growing population and economical development on surrounding territories. In the 21st century under proceeding global warming, a tendency of shrinking of area and volume of glaciation is obviously expected to continue. Working out of strategy of sustainable economic development of the region is the main motivation for elaboration of predictions of glaciers' evolution in the changing environment. Growing demand of fresh water is the basic challenge for the local economy, and efficient planning of water resources is impossible without knowing future state of glaciation. Therefore our research aims at obtaining accurate evaluation of probable future change of the most prominent mountain glaciers of the Greater Caucasus in forthcoming decades and at studying impacts of changing characteristics of glaciation on the run-off in the area. Initially, we focus on two so-called reference glaciers - Marukh (Western Caucasus) and Djankuat (Central Caucasus). Intensive field observations on both of them have been conducted during the last half of the century and essential amount of detailed relevant information has been collected on their geometry change and on mass balance. Besides, meteorological measurements were episodically carried out directly on the glaciers providing enough data for correlation of the local weather conditions with the data from the closest meteorological stations. That is why studying of response of Marukh and Djankuat on the environmental change can be accurately verified, which is crucial for understanding mechanisms driving evolution of large glaciated area in the Caucasus. As the instrument of research
Mass spectrometry-based protein identification with accurate statistical significance assignment.
Alves, Gelio; Yu, Yi-Kuo
2015-03-01
Assigning statistical significance accurately has become increasingly important as metadata of many types, often assembled in hierarchies, are constructed and combined for further biological analyses. Statistical inaccuracy of metadata at any level may propagate to downstream analyses, undermining the validity of scientific conclusions thus drawn. From the perspective of mass spectrometry-based proteomics, even though accurate statistics for peptide identification can now be achieved, accurate protein level statistics remain challenging. We have constructed a protein ID method that combines peptide evidences of a candidate protein based on a rigorous formula derived earlier; in this formula the database P-value of every peptide is weighted, prior to the final combination, according to the number of proteins it maps to. We have also shown that this protein ID method provides accurate protein level E-value, eliminating the need of using empirical post-processing methods for type-I error control. Using a known protein mixture, we find that this protein ID method, when combined with the Sorić formula, yields accurate values for the proportion of false discoveries. In terms of retrieval efficacy, the results from our method are comparable with other methods tested. The source code, implemented in C++ on a linux system, is available for download at ftp://ftp.ncbi.nlm.nih.gov/pub/qmbp/qmbp_ms/RAId/RAId_Linux_64Bit. Published by Oxford University Press 2014. This work is written by US Government employees and is in the public domain in the US.
MODELLING SEDIMENT TRANSPORT FOR THE LAKE MICHIGAN MASS BALANCE PROJECT
A sediment transport model is one component of the overall ensemble of models being developed for the Lake Michigan Mass Balance. The SEDZL model is being applied to simulate the fine-grained sediment transport in Lake Michigan for the 1982-1983 and 1994-1995 periods. Model perf...
Study of Annual Mass Balance (2011-2013) of Rikha Samba Glacier, Hidden Valley, Mustang, Nepal
NASA Astrophysics Data System (ADS)
Gurung, S.; Bhattrai, B. C.; Kayastha, R. B.; Stumm, D.; Joshi, S.; Mool, P. K.
2016-12-01
lthough Himalayan glaciers are of particular interest interms of future water supplies, regional climate changes, and sea-level rises, little is known about them due to lack of reliable and consistent data. There is a need for monitoring these glaciers to bridge this knowledge gap and to provide field measurements necessary to calibrate and validate the results from different remote sensing operations. Therefore, glaciological observations have been carried out by the Cryosphere Monitoring Project (CMP) since September 2011 on Rikha Samba Glacier in Hidden valley, Mustang district in western Nepal in order to study its annual mass balance. This paper presents the first results of that study. There are 10 glaciers in Hidden Valley, named G1, G2, G3, up to G10. Of these, G5 is the Rikha Samba Glacier, which has the largest area (5.37 km2) in this valley and the highest and lowest altitudes (6,476 and 5,392 m a.s.l., respectively). The glacier mass balance discussed in this paper was calculated using the glaciological method and the equilibrium line altitude (ELA).The glacier showed a negative annual point mass balance along the longitudinal profile of its lower part from September 10, 2011 to October 3, 2012. Stake measurements from October 4, 2012 to September 30, 2013 indicated a negative areal average of annual mass balance -0.088±0.019 m w.e. for the whole glacier. Based on these observations, the ELA of the Rikha Samba Glacier is estimated at 5,800 m a.s.l. in 2013. This negative balance may be due to rising air temperatures in the region, which have been incrementally rising since 1980 accompanied by little or no significant increase in precipitation in that period. The negative mass balance confirms the general shrinking trend of the glacier.
A spatially resolved estimate of High Mountain Asia glacier mass balances from 2000 to 2016
NASA Astrophysics Data System (ADS)
Brun, Fanny; Berthier, Etienne; Wagnon, Patrick; Kääb, Andreas; Treichler, Désirée
2017-09-01
High Mountain Asia hosts the largest glacier concentration outside the polar regions. These glaciers are important contributors to streamflow in one of the most populated areas of the world. Past studies have used methods that can provide only regionally averaged glacier mass balances to assess the glacier contribution to rivers and sea level rise. Here we compute the mass balance for about 92% of the glacierized area of High Mountain Asia using time series of digital elevation models derived from satellite stereo-imagery. We calculate a total mass change of -16.3 +/- 3.5 Gt yr-1 (-0.18 +/- 0.04 m w.e. yr-1) between 2000 and 2016, which is less negative than most previous estimates. Region-wide mass balances vary from -4.0 +/- 1.5 Gt yr-1 (-0.62 +/- 0.23 m w.e. yr-1) in Nyainqentanglha to +1.4 +/- 0.8 Gt yr-1 (+0.14 +/- 0.08 m w.e. yr-1) in Kunlun, with large intra-regional variability of individual glacier mass balances (standard deviation within a region ~0.20 m w.e. yr-1). Specifically, our results shed light on the Nyainqentanglha and Pamir glacier mass changes, for which contradictory estimates exist in the literature. They provide crucial information for the calibration of the models used for projecting glacier response to climatic change, as these models do not capture the pattern, magnitude and intra-regional variability of glacier changes at present.
NASA Astrophysics Data System (ADS)
Angchuk, T.; AL, R.; Mandal, A.; Soheb, M.; Bahuguna, I. M.; Singh, V.; Linda, A.
2016-12-01
The present ongoing study is oriented to do the detailed study of the Patsio glacier which is in the Bhaga Basin, Lahaul, Himachal Pradesh. Patsio glacier is a compound valley glacier survived by two prominent tributaries namely Eastern and Western. The two tributaries are facing opposite to each other. The Western tributary facing almost eastward shows higher melting as compared to Eastern tributary facing northwest. This is probably due to solar radiation and sunshine hour, as Western tributary receives high solar radiation and for longer duration. A series of supraglacial lakes which were connected to each other through supra channels were observed on the upper part of the ablation zone at an altitude range of 5100 m and 5300 m amsl. A dead ice covered with thick debris was observed below the current terminus. Despite the large variability of the mass balance in the different seasons Patsio glacier annual balance for the year 2012-2013 was found to be 0.04 ± 0.40 m w.e. the low values signifies that glacier has lost significant amount of mass in recent past and now it is near to the equilibrium state. Seasonal mass balance of Patsio glacier has shown wide range of variability in the mass balances. Patsio glacier receives most of the accumulation during the winter months and duration is long whereas, ablation season is short but quite significant. Monthly and daily variation has depicted that peak ablation months are July and August. The daily ablation in the month of August 2013 was found to be around 5 cm per day, probably due to air temperature. To have a clear picture of the meteorological parameters and its relation with glacier an AWS has set up on the Patsio glacier at an altitude of 5050 m amsl in June 2014. Seasonal mass balance gradients show that gradient was high during the early and late ablation seasons as compared to peak ablation season. The mass balance for the year 2010-2011 was slightly positive.
Balance of dark and luminous mass in rotating galaxies.
McGaugh, Stacy S
2005-10-21
A fine balance between dark and baryonic mass is observed in spiral galaxies. As the contribution of the baryons to the total rotation velocity increases, the contribution of the dark matter decreases by a compensating amount. This poses a fine-tuning problem for galaxy formation models, and may point to new physics for dark matter particles or even a modification of gravity.
The Influence of Intensifying Irrigation on Glacier Mass Balances in High Mountain Asia
NASA Astrophysics Data System (ADS)
de Kok, R.; Tuinenburg, O.; Bonekamp, P. N. J.; Immerzeel, W. W.
2017-12-01
Melt water from snow and glaciers in High Mountain Asia provide a major source of water for millions of inhabitants in the downstream low lying plains. This densely populated region also hosts some of the largest areas of irrigated land in the world. Not only is the water from High Mountain Asia important as a source of irrigation water, the irrigation itself might also change the regional, and even global, climate by increasing atmospheric moisture and by cooling the surface through evapotranspiration. We explore the effect of irrigation in the region on the synoptic climate patterns in High Mountain Asia using the WRF regional climate model. By studying the changes in the energy balance, temperatures and precipitation, we assess how the changes in irrigation patterns may have contributed to the observed trends in mountain climates and associated glacier mass balances. Initial results show that the intensifying irrigation during the last decades causes an increase in summer snowfall in the mountains in Central Karakoram and Kunlun Shan, which are the regions where slight positive mass balances have been observed in recent years. A moisture tracking model confirms that the irrigated areas are a significant moisture source for summer precipitation in High Mountain Asia. These results thus suggest that irrigation may significantly influence glaciers in High Mountain Asia, especially in the regions of observed anomalous mass balance.
Water vapor mass balance method for determining air infiltration rates in houses
David R. DeWalle; Gordon M. Heisler
1980-01-01
A water vapor mass balance technique that includes the use of common humidity-control equipment can be used to determine average air infiltration rates in buildings. Only measurements of the humidity inside and outside the home, the mass of vapor exchanged by a humidifier/dehumidifier, and the volume of interior air space are needed. This method gives results that...
Accurate mass measurements and their appropriate use for reliable analyte identification.
Godfrey, A Ruth; Brenton, A Gareth
2012-09-01
Accurate mass instrumentation is becoming increasingly available to non-expert users. This data can be mis-used, particularly for analyte identification. Current best practice in assigning potential elemental formula for reliable analyte identification has been described with modern informatic approaches to analyte elucidation, including chemometric characterisation, data processing and searching using facilities such as the Chemical Abstracts Service (CAS) Registry and Chemspider.
Studying the Effects of Amazonian Land Cover Change on Glacier Mass Balance in the Tropical Andes
NASA Astrophysics Data System (ADS)
Mark, B. G.; Fernandez, A.; Gabrielli, P.; Montenegro, A.; Postigo, J.; Hellstrom, R. A.
2017-12-01
Recent research has highlighted several ongoing environmental changes occurring across Tropical South America, including Andean glacier retreat, drought, as well as changes in land-use and land-cover. As the regional climate of the area is mostly characterized by land-ocean interactions, the atmospheric convection in the Amazon, and the effect of the Andes on circulation patterns, it follows that changes in one of those regions may affect the other. Most scholars who have studied the causes of tropical glaciers' fluctuations have not analyzed the linkages with changes in the Amazon with the same attention paid to the influence of Pacific sea surface temperature. Here we study the response of glacier surface mass balance in the Cordillera Blanca, Peru (10°S), to a scenario where the Amazonian rainforest is replaced by savannas. We ran climatic simulations at 2-km spatial resolution utilizing the Weather Research and Forecasting (WRF) model considering two scenarios: (a) control (CRTL), with today's rainforest extent; and (b) land cover change (LCC), where all the rainforest was replaced by savanna. WRF output was in turn ingested into a glacier energy and mass balance (GEMB) model that we validate by reconstructing both the accumulated mass balance from available observations, and the altitudinal distribution of mass balance in the region. Seasonal comparison between CRTL and LCC scenarios indicates that forest replacement by savanna results in more positive glacier mass balance. This shift to more positive mass balance contrasts with a (WRF) modeled rise in the elevation of the freezing line (0°C) between 30 to 120 m for the LCC scenario. Our results are surprising because most previous studies have shown that reducing Amazon forest cover diminishes rainfall and increases temperature, suggesting that glaciers should lose mass. We hypothesize and discuss implications of possible land-atmospheric processes that might drive this tropical glacier response to
NASA Astrophysics Data System (ADS)
Steffensen Schmidt, Louise; Aðalgeirsdóttir, Guðfinna; Guðmundsson, Sverrir; Langen, Peter L.; Pálsson, Finnur; Mottram, Ruth; Gascoin, Simon; Björnsson, Helgi
2017-07-01
A simulation of the surface climate of Vatnajökull ice cap, Iceland, carried out with the regional climate model HIRHAM5 for the period 1980-2014, is used to estimate the evolution of the glacier surface mass balance (SMB). This simulation uses a new snow albedo parameterization that allows albedo to exponentially decay with time and is surface temperature dependent. The albedo scheme utilizes a new background map of the ice albedo created from observed MODIS data. The simulation is evaluated against observed daily values of weather parameters from five automatic weather stations (AWSs) from the period 2001-2014, as well as in situ SMB measurements from the period 1995-2014. The model agrees well with observations at the AWS sites, albeit with a general underestimation of the net radiation. This is due to an underestimation of the incoming radiation and a general overestimation of the albedo. The average modelled albedo is overestimated in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and not taking the surface darkening from dirt and volcanic ash deposition during dust storms and volcanic eruptions into account. A comparison with the specific summer, winter, and net mass balance for the whole of Vatnajökull (1995-2014) shows a good overall fit during the summer, with a small mass balance underestimation of 0.04 m w.e. on average, whereas the winter mass balance is overestimated by on average 0.5 m w.e. due to too large precipitation at the highest areas of the ice cap. A simple correction of the accumulation at the highest points of the glacier reduces this to 0.15 m w.e. Here, we use HIRHAM5 to simulate the evolution of the SMB of Vatnajökull for the period 1981-2014 and show that the model provides a reasonable representation of the SMB for this period. However, a major source of uncertainty in the representation of the SMB is the representation of the albedo, and processes currently not accounted for in RCMs
Plöchl, Matthias; Heiermann, Monika; Rodemann, Bernd; Bandte, Martina; Büttner, Carmen
2014-01-15
Knowledge of fate and behavior of plant pathogens in the biogas production chain is limited and hampers the estimation and evaluation of the potential phytosanitary risk if digestate is spread on arable land as a fertilizer. Therefore, simulation is an appropriate tool to demonstrate the effects which influence the steady state of pathogen infected plant material in both digesters and digestate. Simple approaches of kinetics of inactivation and mass balances of infected material were carried out considering single-step as well as two-step digestion. The simulation revealed a very fast to fast reduction of infected material after a singular feeding, reaching a cutback to less than 1% of input within 4 days even for D90-values of 68 h. Steady state mass balances below input rate could be calculated with D90-values of less than 2 h at a continuous hourly feeding. At higher D90-values steady state mass balances exceed the input rate but are still clearly below the sum of input mass. Dilution further decreases mass balances to values 10(-5) to 10(-6) Mg m(-3) for first-step digestion and 10(-8) to 10(-9) for second-step. Copyright © 2013 Elsevier Ltd. All rights reserved.
Virtual Reality-Based Center of Mass-Assisted Personalized Balance Training System
Kumar, Deepesh; González, Alejandro; Das, Abhijit; Dutta, Anirban; Fraisse, Philippe; Hayashibe, Mitsuhiro; Lahiri, Uttama
2018-01-01
Poststroke hemiplegic patients often show altered weight distribution with balance disorders, increasing their risk of fall. Conventional balance training, though powerful, suffers from scarcity of trained therapists, frequent visits to clinics to get therapy, one-on-one therapy sessions, and monotony of repetitive exercise tasks. Thus, technology-assisted balance rehabilitation can be an alternative solution. Here, we chose virtual reality as a technology-based platform to develop motivating balance tasks. This platform was augmented with off-the-shelf available sensors such as Nintendo Wii balance board and Kinect to estimate one’s center of mass (CoM). The virtual reality-based CoM-assisted balance tasks (Virtual CoMBaT) was designed to be adaptive to one’s individualized weight-shifting capability quantified through CoM displacement. Participants were asked to interact with Virtual CoMBaT that offered tasks of varying challenge levels while adhering to ankle strategy for weight shifting. To facilitate the patients to use ankle strategy during weight-shifting, we designed a heel lift detection module. A usability study was carried out with 12 hemiplegic patients. Results indicate the potential of our system to contribute to improving one’s overall performance in balance-related tasks belonging to different difficulty levels. PMID:29359128
Virtual Reality-Based Center of Mass-Assisted Personalized Balance Training System.
Kumar, Deepesh; González, Alejandro; Das, Abhijit; Dutta, Anirban; Fraisse, Philippe; Hayashibe, Mitsuhiro; Lahiri, Uttama
2017-01-01
Poststroke hemiplegic patients often show altered weight distribution with balance disorders, increasing their risk of fall. Conventional balance training, though powerful, suffers from scarcity of trained therapists, frequent visits to clinics to get therapy, one-on-one therapy sessions, and monotony of repetitive exercise tasks. Thus, technology-assisted balance rehabilitation can be an alternative solution. Here, we chose virtual reality as a technology-based platform to develop motivating balance tasks. This platform was augmented with off-the-shelf available sensors such as Nintendo Wii balance board and Kinect to estimate one's center of mass (CoM). The virtual reality-based CoM-assisted balance tasks (Virtual CoMBaT) was designed to be adaptive to one's individualized weight-shifting capability quantified through CoM displacement. Participants were asked to interact with Virtual CoMBaT that offered tasks of varying challenge levels while adhering to ankle strategy for weight shifting. To facilitate the patients to use ankle strategy during weight-shifting, we designed a heel lift detection module. A usability study was carried out with 12 hemiplegic patients. Results indicate the potential of our system to contribute to improving one's overall performance in balance-related tasks belonging to different difficulty levels.
Antarctic Ice-Sheet Mass Balance from Satellite Altimetry 1992 to 2001
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Brenner, Anita C.; Cornejo, Helen; Giovinetto, Mario; Saba, Jack L.; Yi, Donghui
2003-01-01
A major uncertainty in understanding the causes of the current rate of sea level rise is the potential contributions from mass imbalances of the Greenland and Antarctic ice sheets. Estimates of the current mass balance of the Antarctic ice sheet are derived from surface- elevation changes obtained from 9 years of ERS - 1 & 2 radar altimeter data. Elevation time-series are created from altimeter crossovers among 90-day data periods on a 50 km grid to 81.5 S. The time series are fit with a multivariate linear/sinusoidal function to give the average rate of elevation change (dH/dt). On the major Rome-Filchner, Ross, and Amery ice shelves, the W d t are small or near zero. In contrast, the ice shelves of the Antarctic Peninsula and along the West Antarctic coast appear to be thinning significantly, with a 23 +/- 3 cm per year surface elevation decrease on the Larsen ice shelf and a 65 +/- 4 cm per year decrease on the Dotson ice shelf. On the grounded ice, significant elevation decreases are obtained over most of the drainage basins of the Pine Island and Thwaites glaciers in West Antarctica and inland of Law Dome in East Antarctica. Significant elevation increases are observed within about 200 km of the coast around much of the rest of the ice sheet. Farther inland, the changes are a mixed pattern of increases and decreases with increases of a few centimeters per year at the highest elevations of the East Antarctic plateau. The derived elevation changes are combined with estimates of the bedrock uplift from several models to provide maps of ice thickness change. The ice thickness changes enable estimates of the ice mass balances for the major drainage basins, the overall mass balance, and the current contribution of the ice sheet to global sea level change.
Xue, Min; Pan, Shilong; Zhao, Yongjiu
2015-02-15
A novel optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation and balanced photodetection is proposed and experimentally demonstrated, which can eliminate the measurement error induced by the high-order sidebands in the OSSB signal. According to the analytical model of the conventional OSSB-based OVNA, if the optical carrier in the OSSB signal is fully suppressed, the measurement result is exactly the high-order-sideband-induced measurement error. By splitting the OSSB signal after the optical device-under-test (ODUT) into two paths, removing the optical carrier in one path, and then detecting the two signals in the two paths using a balanced photodetector (BPD), high-order-sideband-induced measurement error can be ideally eliminated. As a result, accurate responses of the ODUT can be achieved without complex post-signal processing. A proof-of-concept experiment is carried out. The magnitude and phase responses of a fiber Bragg grating (FBG) measured by the proposed OVNA with different modulation indices are superimposed, showing that the high-order-sideband-induced measurement error is effectively removed.
Grams, Paul E.; Topping, David J.; Schmidt, John C.; Hazel, Joseph E.; Kaplinski, Matt
2013-01-01
Measurements of morphologic change are often used to infer sediment mass balance. Such measurements may, however, result in gross errors when morphologic changes over short reaches are extrapolated to predict changes in sediment mass balance for long river segments. This issue is investigated by examination of morphologic change and sediment influx and efflux for a 100 km segment of the Colorado River in Grand Canyon, Arizona. For each of four monitoring intervals within a 7 year study period, the direction of sand-storage response within short morphologic monitoring reaches was consistent with the flux-based sand mass balance. Both budgeting methods indicate that sand storage was stable or increased during the 7 year period. Extrapolation of the morphologic measurements outside the monitoring reaches does not, however, provide a reasonable estimate of the magnitude of sand-storage change for the 100 km study area. Extrapolation results in large errors, because there is large local variation in site behavior driven by interactions between the flow and local bed topography. During the same flow regime and reach-average sediment supply, some locations accumulate sand while others evacuate sand. The interaction of local hydraulics with local channel geometry exerts more control on local morphodynamic response than sand supply over an encompassing river segment. Changes in the upstream supply of sand modify bed responses but typically do not completely offset the effect of local hydraulics. Thus, accurate sediment budgets for long river segments inferred from reach-scale morphologic measurements must incorporate the effect of local hydraulics in a sampling design or avoid extrapolation altogether.
Mass Balance of the West Antarctic Ice-Sheet from ICESat Measurements
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Li, Jun; Robins, John; Saba, Jack L.; Yi, Donghui
2011-01-01
Mass balance estimates for 2003-2008 are derived from ICESat laser altimetry and compared with estimates for 1992-2002 derived from ERS radar altimetry. The net mass balance of 3 drainage systems (Pine Island, Thwaites/Smith, and the coast of Marie Bryd) for 2003-2008 is a loss of 100 Gt/yr, which increased from a loss of 70 Gt/yr for the earlier period. The DS including the Bindschadler and MacAyeal ice streams draining into the Ross Ice Shelf has a mass gain of 11 Gt/yr for 2003-2008, compared to an earlier loss of 70 Gt/yr. The DS including the Whillans and Kamb ice streams has a mass gain of 12 Gt/yr, including a significant thickening on the upper part of the Kamb DS, compared to a earlier gain of 6 Gt/yr (includes interpolation for a large portion of the DS). The other two DS discharging into the Ronne Ice Shelf and the northern Ellsworth Coast have a mass gain of 39 Gt/yr, compared to a gain of 4 Gt/yr for the earlier period. Overall, the increased losses of 30 Gt/yr in the Pine Island, Thwaites/Smith, and the coast of Marie Bryd DSs are exceeded by increased gains of 59 Gt/yr in the other 4 DS. Overall, the mass loss from the West Antarctic ice sheet has decreased to 38 Gt/yr from the earlier loss of 67 Gt/yr, reducing the contribution to sea level rise to 0.11 mm/yr from 0.19 mm/yr
Energy and Mass Balance At Gran Campo Nevado, Patagonia, Chile
NASA Astrophysics Data System (ADS)
Schneider, C.; Kilian, R.; Casassa, G.
The Gran Campo Nevado (GCN) Ice Cap on Peninsula Muñoz Gamero, Chile, is lo- cated in the southernmost part of the Patagonian Andes at 53S. It comprises an ice cap and numerous outlet glaciers which mostly end in proglacial lakes at sea level. The total ice covered area sums up to approximately 250 km2. GCN forms the only major ice body between the Southern Patagonian Icefield and the Street of Magallan. Its almost unique location in the zone of the all-year westerlies makes it a region of key interest in terms of glacier and climate change studies of the westwind zone of the Southern Hemisphere. Mean annual temperature of approximately +5C at sea level and high precipitation of about 8.000 mm per year lead to an extreme turn-over of ice mass from the accumulation area of the GCN Ice Cap to the ablation areas of the outlet glaciers. Since October 1999 an automated weather station (AWS) is run continuously in the area at Bahia Bahamondes for monitoring climate parameters. From February to April 2000 an additional AWS was operated on Glaciar Lengua a small outlet glacier of GCN to the north-west. Ablation has been measured at stakes during the same pe- riod. The aim of this study, was to obtain point energy and mass balance on Glaciar Lengua. The work was conducted as part of the international and interdisciplinary working group SGran Campo NevadoT and supported by the German Research Foun- & cedil;dation (DFG). Energy balance was calculated using the bulk approach formulas and calibrated to the measured ablation. It turns out, that sensible heat transfer is the major contribution to the energy balance. Since high cloud cover rates prevail, air tempera- ture is the key factor for the energy balance of the glacier. Despite high rain fall rates, energy input from rain fall is of only minor importance to the overall energy balance. From the energy balance computed, it was possible to derive summer-time degree-day factors for Glaciar Lengua. With data from the nearby
Sea Ice Mass Balance Buoys (IMBs): First Results from a Data Processing Intercomparison Study
NASA Astrophysics Data System (ADS)
Hoppmann, Mario; Tiemann, Louisa; Itkin, Polona
2017-04-01
IMBs are autonomous instruments able to continuously monitor the growth and melt of sea ice and its snow cover at a single point on an ice floe. Complementing field expeditions, remote sensing observations and modelling studies, these in-situ data are crucial to assess the mass balance and seasonal evolution of sea ice and snow in the polar oceans. Established subtypes of IMBs combine coarse-resolution temperature profiles through air, snow, ice and ocean with ultrasonic pingers to detect snow accumulation and ice thermodynamic growth. Recent technological advancements enable the use of high-resolution temperature chains, which are also able to identify the surrounding medium through a „heating cycle". The temperature change during this heating cycle provides additional information on the internal properties and processes of the ice. However, a unified data processing technique to reliably and accurately determine sea ice thickness and snow depth from this kind of data is still missing, and an unambiguous interpretation remains a challenge. Following the need to improve techniques for remotely measuring sea ice mass balance, an international IMB working group has recently been established. The main goals are 1) to coordinate IMB deployments, 2) to enhance current IMB data processing and -interpretation techniques, and 3) to provide standardized IMB data products to a broader community. Here we present first results from two different data processing algorithms, applied to selected IMB datasets from the Arctic and Antarctic. Their performance with regard to sea ice thickness and snow depth retrieval is evaluated, and an uncertainty is determined. Although several challenges and caveats in IMB data processing and -interpretation are found, such datasets bear great potential and yield plenty of useful information about sea ice properties and processes. It is planned to include many more algorithms from contributors within the working group, and we explicitly invite
NASA Astrophysics Data System (ADS)
Schlegel, Nicole-Jeanne; Wiese, David N.; Larour, Eric Y.; Watkins, Michael M.; Box, Jason E.; Fettweis, Xavier; van den Broeke, Michiel R.
2016-09-01
Quantifying the Greenland Ice Sheet's future contribution to sea level rise is a challenging task that requires accurate estimates of ice sheet sensitivity to climate change. Forward ice sheet models are promising tools for estimating future ice sheet behavior, yet confidence is low because evaluation of historical simulations is challenging due to the scarcity of continental-wide data for model evaluation. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained mass concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of monthly global gravity fields. Specifically, the Jet Propulsion Laboratory's JPL RL05M GRACE mascon solution (GRACE_JPL) offers an opportunity for the assessment of model-based estimates of ice sheet mass balance (MB) at ˜ 300 km spatial scales. Here, we quantify the differences between Greenland monthly observed MB (GRACE_JPL) and that estimated by state-of-the-art, high-resolution models, with respect to GRACE_JPL and model uncertainties. To simulate the years 2003-2012, we force the Ice Sheet System Model (ISSM) with anomalies from three different surface mass balance (SMB) products derived from regional climate models. Resulting MB is compared against GRACE_JPL within individual mascons. Overall, we find agreement in the northeast and southwest where MB is assumed to be primarily controlled by SMB. In the interior, we find a discrepancy in trend, which we presume to be related to millennial-scale dynamic thickening not considered by our model. In the northwest, seasonal amplitudes agree, but modeled mass trends are muted relative to GRACE_JPL. Here, discrepancies are likely controlled by temporal variability in ice discharge and other related processes not represented by our model simulations, i.e., hydrological processes and ice-ocean interaction. In the southeast, GRACE_JPL exhibits larger seasonal amplitude than predicted by
NASA Astrophysics Data System (ADS)
Fischer, M.; Huss, M.; Hoelzle, M.
2015-12-01
Measuring glacier mass balance is important as it directly reflects the climatic forcing on the glacier surface. Today, repeated comparison of digital elevation models (DEMs) is a popular and widely used approach to derive surface elevation, volume and mass changes for a large number of glaciers. In high-mountain environments, airborne laser scanning (ALS) techniques currently provide the most accurate and highest resolution DEMs on the catchment scale, allowing the computation of glacier changes on an annual or even semi-annual basis. For monitoring individual glaciers though, terrestrial laser scanning (TLS) is easier and more cost-efficiently applied on the seasonal timescale compared to ALS. Since most recently, the application of the latest generation of ultra-long-range near infrared TLS systems allows the acquisition of surface elevation information over snow and ice of unprecedented quality and over larger zones than with previous near infrared TLS devices. Although very small glaciers represent the majority in number in most mountain ranges on Earth, their response to climatic changes is still not fully understood and field measurements are sparse. Therefore, a programme was set up in 2012 to monitor both the seasonal and annual surface mass balance of six very small glaciers across the Swiss Alps using the direct glaciological method. As often nearly the entire surface is visible from one single location, TLS is a highly promising technique to generate repeated high-resolution DEMs as well as to derive seasonal geodetic mass balances of very small ice masses. In this study, we present seasonal surface elevation, volume and geodetic mass changes for five very small glaciers in Switzerland (Glacier de Prapio, Glacier du Sex Rouge, St. Annafirn, Schwarzbachfirn and Pizolgletscher) derived from the comparison of seasonally repeated high-resolution DEMs acquired since autumn 2013 with the new ultra-long-range TLS device Riegl VZ-6000. We show the different
NASA Astrophysics Data System (ADS)
Davaze, Lucas; Rabatel, Antoine; Arnaud, Yves; Sirguey, Pascal; Six, Delphine; Letreguilly, Anne; Dumont, Marie
2018-01-01
Less than 0.25 % of the 250 000 glaciers inventoried in the Randolph Glacier Inventory (RGI V.5) are currently monitored with in situ measurements of surface mass balance. Increasing this archive is very challenging, especially using time-consuming methods based on in situ measurements, and complementary methods are required to quantify the surface mass balance of unmonitored glaciers. The current study relies on the so-called albedo method, based on the analysis of albedo maps retrieved from optical satellite imagery acquired since 2000 by the MODIS sensor, on board the TERRA satellite. Recent studies revealed substantial relationships between summer minimum glacier-wide surface albedo and annual surface mass balance, because this minimum surface albedo is directly related to the accumulation-area ratio and the equilibrium-line altitude. On the basis of 30 glaciers located in the French Alps where annual surface mass balance data are available, our study conducted on the period 2000-2015 confirms the robustness and reliability of the relationship between the summer minimum surface albedo and the annual surface mass balance. For the ablation season, the integrated summer surface albedo is significantly correlated with the summer surface mass balance of the six glaciers seasonally monitored. These results are promising to monitor both annual and summer glacier-wide surface mass balances of individual glaciers at a regional scale using optical satellite images. A sensitivity study on the computed cloud masks revealed a high confidence in the retrieved albedo maps, restricting the number of omission errors. Albedo retrieval artifacts have been detected for topographically incised glaciers, highlighting limitations in the shadow correction algorithm, although inter-annual comparisons are not affected by systematic errors.
NASA Astrophysics Data System (ADS)
Roth, A. C.; Hock, R.; Schuler, T.; Bieniek, P.; Aschwanden, A.
2017-12-01
Mass loss from glaciers in Southeast Alaska is expected to alter downstream ecological systems as runoff patterns change. To investigate these potential changes under future climate scenarios, distributed glacier mass balance modeling is required. However, the spatial resolution gap between global or regional climate models and the requirements for glacier mass balance modeling studies must be addressed first. We have used a linear theory of orographic precipitation model to downscale precipitation from both the Weather Research and Forecasting (WRF) model and ERA-Interim to the Juneau Icefield region over the period 1979-2013. This implementation of the LT model is a unique parameterization that relies on the specification of snow fall speed and rain fall speed as tuning parameters to calculate the cloud time delay, τ. We assessed the LT model results by considering winter precipitation so the effect of melt was minimized. The downscaled precipitation pattern produced by the LT model captures the orographic precipitation pattern absent from the coarse resolution WRF and ERA-Interim precipitation fields. Observational data constraints limited our ability to determine a unique parameter combination and calibrate the LT model to glaciological observations. We established a reference run of parameter values based on literature and performed a sensitivity analysis of the LT model parameters, horizontal resolution, and climate input data on the average winter precipitation. The results of the reference run showed reasonable agreement with the available glaciological measurements. The precipitation pattern produced by the LT model was consistent regardless of parameter combination, horizontal resolution, and climate input data, but the precipitation amount varied strongly with these factors. Due to the consistency of the winter precipitation pattern and the uncertainty in precipitation amount, we suggest a precipitation index map approach to be used in combination with
Krimmel, R.M.
1999-01-01
Net mass balance has been measured since 1958 at South Cascade Glacier using the 'direct method,' e.g. area averages of snow gain and firn and ice loss at stakes. Analysis of cartographic vertical photography has allowed measurement of mass balance using the 'geodetic method' in 1970, 1975, 1977, 1979-80, and 1985-97. Water equivalent change as measured by these nearly independent methods should give similar results. During 1970-97, the direct method shows a cumulative balance of about -15 m, and the geodetic method shows a cumulative balance of about -22 m. The deviation between the two methods is fairly consistent, suggesting no gross errors in either, but rather a cumulative systematic error. It is suspected that the cumulative error is in the direct method because the geodetic method is based on a non-changing reference, the bedrock control, whereas the direct method is measured with reference to only the previous year's summer surface. Possible sources of mass loss that are missing from the direct method are basal melt, internal melt, and ablation on crevasse walls. Possible systematic measurement errors include under-estimation of the density of lost material, sinking stakes, or poorly represented areas.
Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Kärki, Janne
2014-11-01
In this work, the fraction of construction and demolition waste (C&D waste) complicated and economically not feasible to sort out for recycling purposes is used to produce solid recovered fuel (SRF) through mechanical treatment (MT). The paper presents the mass, energy and material balances of this SRF production process. All the process streams (input and output) produced in MT waste sorting plant to produce SRF from C&D waste are sampled and treated according to CEN standard methods for SRF. Proximate and ultimate analysis of these streams is performed and their composition is determined. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. By mass balance means the overall mass flow of input waste material stream in the various output streams and material balances mean the mass flow of components of input waste material stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. The results from mass balance of SRF production process showed that of the total input C&D waste material to MT waste sorting plant, 44% was recovered in the form of SRF, 5% as ferrous metal, 1% as non-ferrous metal, and 28% was sorted out as fine fraction, 18% as reject material and 4% as heavy fraction. The energy balance of this SRF production process showed that of the total input energy content of C&D waste material to MT waste sorting plant, 74% was recovered in the form of SRF, 16% belonged to the reject material and rest 10% belonged to the streams of fine fraction and heavy fraction. From the material balances of this process, mass fractions of plastic (soft), paper and cardboard, wood and plastic (hard) recovered in the SRF stream were 84%, 82%, 72% and 68% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC) and rubber material was found in the reject material
Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Kärki, Janne
2014-08-01
This paper presents the mass, energy and material balances of a solid recovered fuel (SRF) production process. The SRF is produced from commercial and industrial waste (C&IW) through mechanical treatment (MT). In this work various streams of material produced in SRF production process are analyzed for their proximate and ultimate analysis. Based on this analysis and composition of process streams their mass, energy and material balances are established for SRF production process. Here mass balance describes the overall mass flow of input waste material in the various output streams, whereas material balance describes the mass flow of components of input waste stream (such as paper and cardboard, wood, plastic (soft), plastic (hard), textile and rubber) in the various output streams of SRF production process. A commercial scale experimental campaign was conducted on an MT waste sorting plant to produce SRF from C&IW. All the process streams (input and output) produced in this MT plant were sampled and treated according to the CEN standard methods for SRF: EN 15442 and EN 15443. The results from the mass balance of SRF production process showed that of the total input C&IW material to MT waste sorting plant, 62% was recovered in the form of SRF, 4% as ferrous metal, 1% as non-ferrous metal and 21% was sorted out as reject material, 11.6% as fine fraction, and 0.4% as heavy fraction. The energy flow balance in various process streams of this SRF production process showed that of the total input energy content of C&IW to MT plant, 75% energy was recovered in the form of SRF, 20% belonged to the reject material stream and rest 5% belonged with the streams of fine fraction and heavy fraction. In the material balances, mass fractions of plastic (soft), plastic (hard), paper and cardboard and wood recovered in the SRF stream were 88%, 70%, 72% and 60% respectively of their input masses to MT plant. A high mass fraction of plastic (PVC), rubber material and non
NASA Astrophysics Data System (ADS)
Kern, Sara E.; Lin, Lora A.; Fricke, Frederick L.
2014-08-01
U.S. food imports have been increasing steadily for decades, intensifying the need for a rapid and sensitive screening technique. A method has been developed that uses foam disks to sample the surface of incoming produce. This work provides complimentary information to the extensive amount of published pesticide fragmentation data collected using LCMS systems (Sack et al. Journal of Agricultural and Food Chemistry, 59, 6383-6411, 2011; Mol et al. Analytical and Bioanalytical Chemistry, 403, 2891-2908, 2012). The disks are directly analyzed using transmission-mode direct analysis in real time (DART) ambient pressure desorption ionization coupled to a high resolution accurate mass-mass spectrometer (HRAM-MS). In order to provide more certainty in the identification of the pesticides detected, a library of accurate mass fragments and isotopes of the protonated parent molecular ion (the [M+H]+) has been developed. The HRAM-MS is equipped with a quadrupole mass filter, providing the capability of "data-dependent" fragmentation, as opposed to "all -ion" fragmentation (where all of the ions enter a collision chamber and are fragmented at once). A temperature gradient for the DART helium stream and multiple collision energies were employed to detect and fragment 164 pesticides of varying chemical classes, sizes, and polarities. The accurate mass information of precursor ([M+H]+ ion) and fragment ions is essential in correctly identifying chemical contaminants on the surface of imported produce. Additionally, the inclusion of isotopes of the [M+H]+ in the database adds another metric to the confirmation process. The fragmentation data were collected using a Q-Exactive mass spectrometer and were added to a database used to process data collected with an Exactive mass spectrometer, an instrument that is more readily available for this screening application. The commodities investigated range from smooth-skinned produce such as apples to rougher surfaces like broccoli. The
NASA Astrophysics Data System (ADS)
Klug, Christoph; Bollmann, Erik; Galos, Stephan; Kaser, Georg; Prinz, Rainer; Rieg, Lorenzo; Sailer, Rudolf
2016-04-01
The quantification of glacier mass changes is fundamental for glacier monitoring and provides important information for climate change assessments, hydrological applications and sea-level changes. On Alpine glaciers two methods of measuring glacier mass changes are widely applied: the direct glaciological method and the geodetic method. Over the last decades several studies compared the mass balance estimates obtained by both methods to identify and correct stochastic and systematic errors. In almost all of these studies, the time span for comparison between the two methods is about one decade or longer. On Hintereisferner (HEF; Ötztal Alps, Austria) mass balance measurements were initiated in the glaciological year 1952/53, resulting in a consistent mass balance data set with an estimated accuracy of ±0.2 m w.e. a-1. Furthermore, 11 airborne laser scanning (ALS) campaigns were conducted between 2001 and 2011 at HEF, all consistent in accuracy as well as in precision (± 0.04 to 0.10 m for slopes ≤ 50°). This is a world-wide unique ALS dataset of a glacierized alpine catchment. Flight campaigns were performed close to the end of the hydrological year (30th September). Resulting data provide high quality topographic information to derive glacier mass changes by applying the geodetic method. On sub-decadal time-scales such method comparisons are rare, or reveal unexplainable large discrepancies between both mass balance methods. In this study we estimate stochastic and systematic uncertainties of the ALS data for processing volume changes, and quantify methodological differences, such as density assumptions, unequal measurement dates, crevasses and glacier dynamics. Hence, we present a method to compare direct glaciological and geodetic mass balances on an annual basis. In a first step, we calculate the annual geodetic mass balance of HEF between 2001 and 2011, resulting in a thickness change map of the glacier. In a second step, the snow cover, which has
NASA Astrophysics Data System (ADS)
Machguth, H.; Paul, F.; Kotlarski, S.; Hoelzle, M.
2009-04-01
Climate model output has been applied in several studies on glacier mass balance calculation. Hereby, computation of mass balance has mostly been performed at the native resolution of the climate model output or data from individual cells were selected and statistically downscaled. Little attention has been given to the issue of downscaling entire fields of climate model output to a resolution fine enough to compute glacier mass balance in rugged high-mountain terrain. In this study we explore the use of gridded output from a regional climate model (RCM) to drive a distributed mass balance model for the perimeter of the Swiss Alps and the time frame 1979-2003. Our focus lies on the development and testing of downscaling and validation methods. The mass balance model runs at daily steps and 100 m spatial resolution while the RCM REMO provides daily grids (approx. 18 km resolution) of dynamically downscaled re-analysis data. Interpolation techniques and sub-grid parametrizations are combined to bridge the gap in spatial resolution and to obtain daily input fields of air temperature, global radiation and precipitation. The meteorological input fields are compared to measurements at 14 high-elevation weather stations. Computed mass balances are compared to various sets of direct measurements, including stake readings and mass balances for entire glaciers. The validation procedure is performed separately for annual, winter and summer balances. Time series of mass balances for entire glaciers obtained from the model run agree well with observed time series. On the one hand, summer melt measured at stakes on several glaciers is well reproduced by the model, on the other hand, observed accumulation is either over- or underestimated. It is shown that these shifts are systematic and correlated to regional biases in the meteorological input fields. We conclude that the gap in spatial resolution is not a large drawback, while biases in RCM output are a major limitation to
Water and sodium balances and their relation to body mass changes in microgravity.
Drummer, C; Hesse, C; Baisch, F; Norsk, P; Elmann-Larsen, B; Gerzer, R; Heer, M
2000-12-01
Since the very beginning of space physiology research, the deficit in body mass that is often observed after landing has always been interpreted as an indication of the absolute fluid loss early during space missions. However, in contrast to central hypervolemic conditions on Earth, the acute shift of blood volume from the legs to the upper part of the body in astronauts entering microgravity (microG) has neither stimulated diuresis and natriuresis nor resulted in negative water-and sodium-balances. We therefore examined the kinetics of body mass changes in astronauts (n = 3) during their several weeks aboard the space station MIR. A continuous diet monitoring was performed during the first mission (EuroMIR94, 30 days). The second mission (MIR97, 19 days) comprised a 15-day metabolic ward period (including predefined constant energy and sodium intake). Water and sodium balances were calculated and the kinetic of changes in basal concentrations of fluid-balance-related hormones during flight were determined. The data suggest firstly that loss of body mass during space flight is rather a consequence of hypocaloric nutrition. Secondly, microG provokes a sodium retaining hormonal status and may lead to sodium storage without an accompanying fluid retention.
Composition of Meridiani Hematite-rich Spherules: A Mass-Balance Mixing-Model Approach
NASA Astrophysics Data System (ADS)
Jolliff, B. L.; Athena Science Team
2005-03-01
A mass-balance model using APXS data and microscopic images indicates that the composition of spherules ("blueberries"), found at the Meridiani site by the Mars Exploration Rover Opportunity and thought to be concretions, contain ~45-60 wt% hematite.
NASA Astrophysics Data System (ADS)
Nakamura, Kazuki; Yamanokuchi, Tsutomu; Doi, Koichiro; Shibuya, Kazuo
2016-06-01
We quantify the mass budget of the Shirase drainage basin (SHI), Antarctica, by separately estimating snow accumulation (surface mass balance; SMB) and glacier ice mass discharge (IMD). We estimated the SMB in the SHI, using a regional atmospheric climate model (RACMO2.1). The SMB of the mainstream A flow region was 12.1 ± 1.5 Gt a-1 for an area of 1.985 × 105 km2. Obvious overestimation of the model round the coast, ∼0.5 Gt a-1, was corrected for. For calculating the IMD, we employed a 15-m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with a digital elevation model (DEM) to determine the heights at the grounding line (GL), after comparison with the interpolated Bamber DEM grid heights; the results of this are referred to as the measured heights. Ice thickness data at the GL were inferred by using a free-board relationship between the measured height and the ice thickness, and considering the measured firn depth correction (4.2 m with the reference ice density of 910 kg m-3) for the nearby blue-ice area. The total IMD was estimated to be 14.0 ± 1.8 Gt a-1. Semi-empirical firn densification model gives the estimate within 0.1-0.2 Gt a-1 difference. The estimated net mass balance, -1.9 Gt a-1, has a two-σ uncertainty of ±3.3 Gt a-1, and probable melt water discharge strongly suggests negative NMB, although the associated uncertainty is large.
Development of the ECLSS Sizing Analysis Tool and ARS Mass Balance Model Using Microsoft Excel
NASA Technical Reports Server (NTRS)
McGlothlin, E. P.; Yeh, H. Y.; Lin, C. H.
1999-01-01
The development of a Microsoft Excel-compatible Environmental Control and Life Support System (ECLSS) sizing analysis "tool" for conceptual design of Mars human exploration missions makes it possible for a user to choose a certain technology in the corresponding subsystem. This tool estimates the mass, volume, and power requirements of every technology in a subsystem and the system as a whole. Furthermore, to verify that a design sized by the ECLSS Sizing Tool meets the mission requirements and integrates properly, mass balance models that solve for component throughputs of such ECLSS systems as the Water Recovery System (WRS) and Air Revitalization System (ARS) must be developed. The ARS Mass Balance Model will be discussed in this paper.
Apparatus for accurate density measurements of fluids based on a magnetic suspension balance
NASA Astrophysics Data System (ADS)
Gong, Maoqiong; Li, Huiya; Guo, Hao; Dong, Xueqiang; Wu, J. F.
2012-06-01
A new apparatus for accurate pressure, density and temperature (p, ρ, T) measurements over wide ranges of (p, ρ, T) (90 K to 290 K; 0 MPa to 3 MPa; 0 kg/m3 to 2000 kg/m3) is described. This apparatus is based on a magnetic suspension balance which applies the Archimedes' buoyancy principle. In order to verify the new apparatus, comprehensive (p, ρ, T) measurements on pure nitrogen were carried out. The maximum relative standard uncertainty is 0.09% in density. The maximum standard uncertainty in temperature is 5 mK, and that in pressure is 250 Pa for 1.5 MPa and 390 Pa for 3MPa full scale range respectively. The experimental data were compared with selected literature data and good agreements were found.
Surface mass balance of Greenland mountain glaciers and ice caps
NASA Astrophysics Data System (ADS)
Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.
2009-12-01
Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.
NASA Astrophysics Data System (ADS)
Pratap, B.
2015-12-01
The glacier mass balance is undelayed, unfiltered and direct method to assess the impact of climate change on the glaciers. Many studies suggest that some of the Himalayan glaciers have lost their mass at an increased rate during the past few decades. Furthermore, the mass balance gradient and hypsometric analysis are important to understand the glacier response towards climatic perturbations. Our long term in-situ monitoring on the Dokriani Glacier provides great insights to understand the variability in central Himalayan glaciers. We report the relationship between glacier hypsometry and annual mass balance gradient (12 years) to understand the glacier's response towards climate change. Dokriani Glacier in the Bhagirathi basin is a small (7 km2) NNW exposed glacier in the western part of central Himalaya, India. The study analysed the annual balance, mass balance gradient and length changes observed during first decade of 21st century (2007-2013) and compare with the previous observations of 1990s (1992-2000). A large spatial variability in the mass balance gradients of two different periods has been observed. The equilibrium-line altitude (ELA) was fluctuated between 5000 and 5100 m a.s.l. and the derived time averaged ELA (ELAn) and balance budget ELA (ELA0) were 5075 and 4965 m a.s.l respectively during 1992-2013. The observed time-averaged accumulation-area ratio (AARn) and balance budget AAR (AAR0) were 0.67 and 0.72 respectively during 1992-2013. The higher value of AAR comprises due to flat and broader accumulation area (4.50 km2) of the glacier. Although, having larger accumulation area, the glacier has faced strong mass wasting with average annual ablation of -1.82 m w.e. a-1 in the ablation zone as compare to residual average annual accumulation of 0.41 m w.e. a-1. Based on the annual mass balance series (12 years) Dokriani Glacier has continuous negative annual balances with monotonically negative cumulative mass loss of -3.86 m w.e with the average
LINKING GREAT WATERSHEDS WITH LAKE MICHIGAN: THE LAKE MICHIGAN MASS BALANCE STUDY
An overview of the Lake Michigan Mass Balance Study -- which is focusing on atrazine, PCBs, nutrients, suspended solids, trans-nonachlor, and mercury. The relative contribution of contaminants to Lake Michigan will be examined for all major watersheds in the basin. - - - Further ...
Mass Balance of Perfluoroalkyl Acids in the Baltic Sea
2013-01-01
A mass balance was assembled for perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDA), and perfluorooctanesulfonic acid (PFOS) in the Baltic Sea. Inputs (from riverine discharge, atmospheric deposition, coastal wastewater discharges, and the North Sea) and outputs (to sediment burial, transformation of the chemical, and the North Sea), as well as the inventory in the Baltic Sea, were estimated from recently published monitoring data. Formation of the chemicals in the water column from precursors was not considered. River inflow and atmospheric deposition were the dominant inputs, while wastewater treatment plant (WWTP) effluents made a minor contribution (<5%). A mass balance of the Oder River watershed was assembled to explore the sources of the perfluoroalkyl acids (PFAAs) in the river inflow. It indicated that WWTP effluents made only a moderate contribution to riverine discharge (21% for PFOA, 6% for PFOS), while atmospheric deposition to the watershed was 1–2 orders of magnitude greater than WWTP discharges. The input to the Baltic Sea exceeded the output for all four PFAAs, suggesting that inputs were higher during 2005–2010 than during the previous 20 years despite efforts to reduce emissions of PFAAs. One possible explanation is the retention and delayed release of PFAAs from atmospheric deposition in the soils and groundwater of the watershed. PMID:23528236
Large-scale subduction of continental crust implied by India-Asia mass-balance calculation
NASA Astrophysics Data System (ADS)
Ingalls, Miquela; Rowley, David B.; Currie, Brian; Colman, Albert S.
2016-11-01
Continental crust is buoyant compared with its oceanic counterpart and resists subduction into the mantle. When two continents collide, the mass balance for the continental crust is therefore assumed to be maintained. Here we use estimates of pre-collisional crustal thickness and convergence history derived from plate kinematic models to calculate the crustal mass balance in the India-Asia collisional system. Using the current best estimates for the timing of the diachronous onset of collision between India and Eurasia, we find that about 50% of the pre-collisional continental crustal mass cannot be accounted for in the crustal reservoir preserved at Earth's surface today--represented by the mass preserved in the thickened crust that makes up the Himalaya, Tibet and much of adjacent Asia, as well as southeast Asian tectonic escape and exported eroded sediments. This implies large-scale subduction of continental crust during the collision, with a mass equivalent to about 15% of the total oceanic crustal subduction flux since 56 million years ago. We suggest that similar contamination of the mantle by direct input of radiogenic continental crustal materials during past continent-continent collisions is reflected in some ocean crust and ocean island basalt geochemistry. The subduction of continental crust may therefore contribute significantly to the evolution of mantle geochemistry.
20 years of mass balances on the Piloto glacier, Las Cuevas river basin, Mendoza, Argentina
NASA Astrophysics Data System (ADS)
Leiva, J. C.; Cabrera, G. A.; Lenzano, L. E.
2007-10-01
Climatic changes of the 20th century have altered the water cycle in the Andean basins of central Argentina. The most visible change is seen in the mountain glaciers, with loss of part of their mass due to decreasing thickness and a substantial recession in the last 100 years. This paper briefly describes the results of glacier mass balance research since 1979 in the Piloto Glacier at the Cajón del Rubio, in the headwaters of Las Cuevas River, presenting new results for the period 1997-2003. Very large interannual variability of net annual specific balance is evident, due largely to variations in winter snow accumulation, with a maximum net annual value of + 151 cm w.e. and a minimum value of - 230 cm w.e. Wet El Niño years are normally associated with positive net annual balances, while dry La Niña years generally result in negative balances. Within the 24-year period, 67% of the years show negative net annual specific balances, with a cumulative mass balance loss of - 10.50 m water equivalent (w.e.). Except for exceptions normally related to El Niño events, a general decreasing trend of winter snow accumulation is evident in the record, particularly after 1992, which has a strong effect in the overall negative mass balance values. The glacier contribution to Las Cuevas River runoff is analysed based on the Punta de Vacas River gauge station for a hypothetical year without snow precipitation (YWSP), when the snowmelt component is zero. Extremely dry years similar to a YWSP have occurred in 1968-1969, 1969-1970 and 1996-1997. The Punta de Vacas gauge station is located 62 km downstream from Piloto Glacier, and the basin contains 3.0% of uncovered glacier ice and 3.7% of debris-covered ice. The total glacier contribution to Las Cuevas River discharge is calculated as 82 ± 8% during extremely dry years. If glacier wastage continues at the present trend as observed during the last 2 decades, it will severely affect the water resources in the arid central Andes of
Glacier mass balance in high-arctic areas with anomalous gravity
NASA Astrophysics Data System (ADS)
Sharov, A.; Rieser, D.; Nikolskiy, D.
2012-04-01
All known glaciological models describing the evolution of Arctic land- and sea-ice masses in changing climate treat the Earth's gravity as horizontally constant, but it isn't. In the High Arctic, the strength of the gravitational field varies considerably across even short distances under the influence of a density gradient, and the magnitude of free air gravity anomalies attains 100 mGal and more. On long-term base, instantaneous deviations of gravity can have a noticeable effect on the regime and mass budget of glaciological objects. At best, the gravity-induced component of ice mass variations can be determined on topographically smooth, open and steady surfaces, like those of arctic planes, regular ice caps and landfast sea ice. The present research is devoted to studying gravity-driven impacts on glacier mass balance in the outer periphery of four Eurasian shelf seas with a very cold, dry climate and rather episodic character of winter precipitation. As main study objects we had chosen a dozen Russia's northernmost insular ice caps, tens to hundreds of square kilometres in extent, situated in a close vicinity of strong gravity anomalies and surrounded with extensive fields of fast and/or drift ice for most of the year. The supposition about gravitational forcing on glacioclimatic settings in the study region is based on the results of quantitative comparison and joint interpretation of existing glacier change maps and available data on the Arctic gravity field and solid precipitation. The overall mapping of medium-term (from decadal to half-centennial) changes in glacier volumes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1980s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. Free-air gravity anomalies were
Identification of "Known Unknowns" Utilizing Accurate Mass Data and ChemSpider
NASA Astrophysics Data System (ADS)
Little, James L.; Williams, Antony J.; Pshenichnov, Alexey; Tkachenko, Valery
2012-01-01
In many cases, an unknown to an investigator is actually known in the chemical literature, a reference database, or an internet resource. We refer to these types of compounds as "known unknowns." ChemSpider is a very valuable internet database of known compounds useful in the identification of these types of compounds in commercial, environmental, forensic, and natural product samples. The database contains over 26 million entries from hundreds of data sources and is provided as a free resource to the community. Accurate mass mass spectrometry data is used to query the database by either elemental composition or a monoisotopic mass. Searching by elemental composition is the preferred approach. However, it is often difficult to determine a unique elemental composition for compounds with molecular weights greater than 600 Da. In these cases, searching by the monoisotopic mass is advantageous. In either case, the search results are refined by sorting the number of references associated with each compound in descending order. This raises the most useful candidates to the top of the list for further evaluation. These approaches were shown to be successful in identifying "known unknowns" noted in our laboratory and for compounds of interest to others.
Thurman, E Michael; Ferrer, Imma; Blotevogel, Jens; Borch, Thomas
2014-10-07
Two series of ethylene oxide (EO) surfactants, polyethylene glycols (PEGs from EO3 to EO33) and linear alkyl ethoxylates (LAEs C-9 to C-15 with EO3-EO28), were identified in hydraulic fracturing flowback and produced water using a new application of the Kendrick mass defect and liquid chromatography/quadrupole-time-of-flight mass spectrometry. The Kendrick mass defect differentiates the proton, ammonium, and sodium adducts in both singly and doubly charged forms. A structural model of adduct formation is presented, and binding constants are calculated, which is based on a spherical cagelike conformation, where the central cation (NH4(+) or Na(+)) is coordinated with ether oxygens. A major purpose of the study was the identification of the ethylene oxide (EO) surfactants and the construction of a database with accurate masses and retention times in order to unravel the mass spectral complexity of surfactant mixtures used in hydraulic fracturing fluids. For example, over 500 accurate mass assignments are made in a few seconds of computer time, which then is used as a fingerprint chromatogram of the water samples. This technique is applied to a series of flowback and produced water samples to illustrate the usefulness of ethoxylate "fingerprinting", in a first application to monitor water quality that results from fluids used in hydraulic fracturing.
THE LAKE MICHIGAN MASS BALANCE PROJECT: QUALITY ASSURANCE PLAN FOR MATHEMATICAL MODELLING
This report documents the quality assurance process for the development and application of the Lake Michigan Mass Balance Models. The scope includes the overall modeling framework as well as the specific submodels that are linked to form a comprehensive synthesis of physical, che...
DOE Office of Scientific and Technical Information (OSTI.GOV)
KLEM, M.J.
2000-05-11
The purpose of these calculations is to develop the material balances for documentation of the Canister Storage Building (CSB) Process Flow Diagram (PFD) and future reference. The attached mass balances were prepared to support revision two of the PFD for the CSB. The calculations refer to diagram H-2-825869.
NASA Astrophysics Data System (ADS)
Ban, Yunyun; Chen, Tianqin; Yan, Jun; Lei, Tingwu
2017-04-01
The measurement of sediment concentration in water is of great importance in soil erosion research and soil and water loss monitoring systems. The traditional weighing method has long been the foundation of all the other measuring methods and instrument calibration. The development of a new method to replace the traditional oven-drying method is of interest in research and practice for the quick and efficient measurement of sediment concentration, especially field measurements. A new method is advanced in this study for accurately measuring the sediment concentration based on the accurate measurement of the mass of the sediment-water mixture in the confined constant volume container (CVC). A sediment-laden water sample is put into the CVC to determine its mass before the CVC is filled with water and weighed again for the total mass of the water and sediments in the container. The known volume of the CVC, the mass of sediment-laden water, and sediment particle density are used to calculate the mass of water, which is replaced by sediments, therefore sediment concentration of the sample is calculated. The influence of water temperature was corrected by measuring water density to determine the temperature of water before measurements were conducted. The CVC was used to eliminate the surface tension effect so as to obtain the accurate volume of water and sediment mixture. Experimental results showed that the method was capable of measuring the sediment concentration from 0.5 up to 1200 kg m-3. A good liner relationship existed between the designed and measured sediment concentrations with all the coefficients of determination greater than 0.999 and the averaged relative error less than 0.2%. All of these seem to indicate that the new method is capable of measuring a full range of sediment concentration above 0.5 kg m-3 to replace the traditional oven-drying method as a standard method for evaluating and calibrating other methods.
Surface Mass Balance of the Greenland Ice Sheet Derived from Paleoclimate Reanalysis
NASA Astrophysics Data System (ADS)
Badgeley, J.; Steig, E. J.; Hakim, G. J.; Anderson, J.; Tardif, R.
2017-12-01
Modeling past ice-sheet behavior requires independent knowledge of past surface mass balance. Though models provide useful insight into ice-sheet response to climate forcing, if past climate is unknown, then ascertaining the rate and extent of past ice-sheet change is limited to geological and geophysical constraints. We use a novel data-assimilation framework developed under the Last Millennium Reanalysis Project (Hakim et al., 2016) to reconstruct past climate over ice sheets with the intent of creating an independent surface mass balance record for paleo ice-sheet modeling. Paleoclimate data assimilation combines the physics of climate models and the time series evidence of proxy records in an offline, ensemble-based approach. This framework allows for the assimilation of numerous proxy records and archive types while maintaining spatial consistency with known climate dynamics and physics captured by the models. In our reconstruction, we use the Community Climate System Model version 4, CMIP5 last millennium simulation (Taylor et al., 2012; Landrum et al., 2013) and a nearly complete database of ice core oxygen isotope records to reconstruct Holocene surface temperature and precipitation over the Greenland Ice Sheet on a decadal timescale. By applying a seasonality to this reconstruction (from the TraCE-21ka simulation; Liu et al., 2009), our reanalysis can be used in seasonally-based surface mass balance models. Here we discuss the methods behind our reanalysis and the performance of our reconstruction through prediction of unassimilated proxy records and comparison to paleoclimate reconstructions and reanalysis products.
ERIC Educational Resources Information Center
Carnegie, John W.
This module describes the process used to determine solids mass and location throughout a waste water treatment plant, explains how these values are used to determine the solids mass balance around single treatment units and the entire system, and presents calculations of solids in pounds and sludge units. The instructor's manual contains a…
Origin of howardites, diogenites and eucrites - A mass balance constraint
NASA Technical Reports Server (NTRS)
Warren, P. H.
1985-01-01
Two petrogenetic models for the noncumulate-basaltic parts of howardite meteorites are discussed. A mass balance constraint is developed which indicates that more than half of the basaltic components in howardites formed as residual liquids from fractional crystallization of melts that had earlier produced diogentelike pyroxene cumulate components. Other model constriants involving scandium trends, clustering near olivine-pyroxene-plagioclase peritectic, and MgO/(MgO + FeO) ratios are discussed.
The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle
Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.
2002-01-01
A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining
The role of crystallization-driven exsolution on the sulfur mass balance in volcanic arc magmas
Su, Yanqing; Huber, Christian; Bachmann, Olivier; Zajacz, Zoltán; Wright, Heather M.; Vazquez, Jorge A.
2016-01-01
The release of large amounts of sulfur to the stratosphere during explosive eruptions affects the radiative balance in the atmosphere and consequentially impacts climate for up to several years after the event. Quantitative estimations of the processes that control the mass balance of sulfur between melt, crystals, and vapor bubbles is needed to better understand the potential sulfur yield of individual eruption events and the conditions that favor large sulfur outputs to the atmosphere. The processes that control sulfur partitioning in magmas are (1) exsolution of volatiles (dominantly H2O) during decompression (first boiling) and during isobaric crystallization (second boiling), (2) the crystallization and breakdown of sulfide or sulfate phases in the magma, and (3) the transport of sulfur-rich vapor (gas influx) from deeper unerupted regions of the magma reservoir. Vapor exsolution and the formation/breakdown of sulfur-rich phases can all be considered as closed-system processes where mass balance arguments are generally easier to constrain, whereas the contribution of sulfur by vapor transport (open system process) is more difficult to quantify. The ubiquitous “excess sulfur” problem, which refers to the much higher sulfur mass released during eruptions than what can be accounted for by amount of sulfur originally dissolved in erupted melt, as estimated from melt inclusion sulfur concentrations (the “petrologic estimate”), reflects the challenges in closing the sulfur mass balance between crystals, melt, and vapor before and during a volcanic eruption. In this work, we try to quantify the relative importance of closed- and open-system processes for silicic arc volcanoes using kinetic models of sulfur partitioning during exsolution. Our calculations show that crystallization-induced exsolution (second boiling) can generate a significant fraction of the excess sulfur observed in crystal-rich arc magmas. This result does not negate the important role of
NASA Astrophysics Data System (ADS)
Hillerup Larsen, S.; Citterio, M.; Hock, R. M.; Ahlstrom, A. P.
2012-12-01
The A.P. Olsen Ice Cap (74.6 N, 21.5 W) in NE Greenland covers an area of 295 km2, is composed by two domes, of which the western is the largest, and spans an elevation range between 200 and 1450 m a.s.l. In this study we calculate the 2008-2011 annual glacier mass balance based on in situ observations, we model the surface energy balance over the same period, and we reconstruct annual glacier mass balance since 1995. We use GlacioBasis Monitoring Programme observations from a network of 15 ablation stakes and three automatic weather stations (AWS) at 600 m (ca. 100 m higher than the terminus) and at 840 m on the main glacier outlet of the western dome, and at 1430 m in the accumulation area. Accumulation is measured every year in springtime by snow radar surveys calibrated with manual probing and density profiles from snow pits. GlacioBasis data start in 2008, but a longer time series starting in 1995 is available from a weather station at 44 m a.s.l. close to Zackenberg Research Station, ca. 30 km further west. Shorter data series from three more AWS on land at 145 m, 410 m and 1283 m a.s.l. are used to estimate monthly average temperature lapse rates outside of the glacier boundary layer, and to detect the occurrence of temperature inversions. The surface energy mass balance is dominated by the radiative fluxes. We discuss the effect of shadows from the valley sides over parts of the tongue, especially early and late in the melt season when the sun is lower over the horizon, and analyze the modeled mass balance sensitivity to a 1 °C temperature increase. A temperature index model driven by the 1995-2008 time series and calibrated using post-2008 glacier mass balance measurements shows large interannual variability, with 5 of the most negative mass balance years of the entire 1995-2011period occurring between 2003 and 2008. In particular during 2008 the glacier experienced almost no net accumulation over the entire elevation range. This matches 2008 mass balance
NASA Astrophysics Data System (ADS)
DeTemple, B.; Wilcock, P.
2011-12-01
In an alluvial, gravel-bed stream governed by a plane-bed bedload transport regime, the physicochemical properties, size distribution, and granular architecture of the sediment grains that constitute the streambed surface influence many hydrodynamic, geomorphic, chemical, and ecological processes. Consequently, the abilities to accurately characterize the morphology and model the morphodynamics of the streambed surface and its interaction with the bedload above and subsurface below are necessary for a more complete understanding of how sediment, flow, organisms, and biogeochemistry interact. We report on our progress in the bottom-up development of low-pass filtered continuum streambed and bedload sediment mass balance laws for an alluvial, gravel-bed stream. These balance laws are assembled in a four stage process. First, the stream sediment-water system is conceptually abstracted as a nested, multi-phase, multi-species, structured continuum. Second, the granular surface of an aggregate of sediment grains is mathematically defined. Third, an integral approach to mass balance, founded in the continuum theory of multiphase flow, is used to formulate primordial, differential, instantaneous, local, continuum, mass balance laws applicable at any material point within a gravel-bed stream. Fourth, area averaging and time-after-area averaging, employing planform, low-pass filtering expressed as correlation or convolution integrals and based on the spatial and temporal filtering techniques found in the fields of multiphase flow, porous media flow, and large eddy simulation of turbulent fluid flow, are applied to smooth the primordial equations while maximizing stratigraphic resolution and preserving the definitions of relevant morphodynamic surfaces. Our approach unifies, corrects, contextualizes, and generalizes prior efforts at developing stream sediment continuity equations, including the top-down derivations of the surface layer (or "active layer") approach of Hirano
Energy balance of stellar coronae. III - Effect of stellar mass and radius
NASA Technical Reports Server (NTRS)
Hammer, R.
1984-01-01
A homologous transformation is derived which permits the application of the numerical coronal models of Hammer from a star with solar mass and radius to other stars. This scaling requires a few approximations concerning the lower boundary conditions and the temperature dependence of the conductivity and emissivity. These approximations are discussed and found to be surprisingly mild. Therefore, the scaling of the coronal models to other stars is rather accurate; it is found to be particularly accurate for main-sequence stars. The transformation is used to derive an equation that gives the maximum temperature of open coronal regions as a function of stellar mass and radius, the coronal heating flux, and the characteristic damping length over which the corona is heated.
Griffiths, Nia W; Wyatt, Mark F; Kean, Suzanna D; Graham, Andrew E; Stein, Bridget K; Brenton, A Gareth
2010-06-15
A method for the accurate mass measurement of positive radical ions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is described. Initial use of a conjugated oligomeric calibration material was rejected in favour of a series of meso-tetraalkyl/tetraalkylaryl-functionalised porphyrins, from which the two calibrants required for a particular accurate mass measurement were chosen. While all measurements of monoisotopic species were within +/-5 ppm, and the method was rigorously validated using chemometrics, mean values of five measurements were used for extra confidence in the generation of potential elemental formulae. Potential difficulties encountered when measuring compounds containing multi-isotopic elements are discussed, where the monoisotopic peak is no longer the lowest mass peak, and a simple mass-correction solution can be applied. The method requires no significant expertise to implement, but care and attention is required to obtain valid measurements. The method is operationally simple and will prove useful to the analytical chemistry community. Copyright (c) 2010 John Wiley & Sons, Ltd.
MASS BALANCE MODELLING OF PCBS IN THE FOX RIVER/GREEN BAY COMPLEX
The USEPA Office of Research and Development developed and applies a multimedia, mass balance modeling approach to the Fox River/Green Bay complex to aid managers with remedial decision-making. The suite of models were applied to PCBs due to the long history of contamination and ...
Tectonic controls on the long-term carbon isotope mass balance.
Shields, Graham A; Mills, Benjamin J W
2017-04-25
The long-term, steady-state marine carbon isotope record reflects changes to the proportional burial rate of organic carbon relative to total carbon on a global scale. For this reason, times of high δ 13 C are conventionally interpreted to be oxygenation events caused by excess organic burial. Here we show that the carbon isotope mass balance is also significantly affected by tectonic uplift and erosion via changes to the inorganic carbon cycle that are independent of changes to the isotopic composition of carbon input. This view is supported by inverse covariance between δ 13 C and a range of uplift proxies, including seawater 87 Sr/ 86 Sr, which demonstrates how erosional forcing of carbonate weathering outweighs that of organic burial on geological timescales. A model of the long-term carbon cycle shows that increases in δ 13 C need not be associated with increased organic burial and that alternative tectonic drivers (erosion, outgassing) provide testable and plausible explanations for sustained deviations from the long-term δ 13 C mean. Our approach emphasizes the commonly overlooked difference between how net and gross carbon fluxes affect the long-term carbon isotope mass balance, and may lead to reassessment of the role that the δ 13 C record plays in reconstructing the oxygenation of earth's surface environment.
Mass balance model parameter transferability on a tropical glacier
NASA Astrophysics Data System (ADS)
Gurgiser, Wolfgang; Mölg, Thomas; Nicholson, Lindsey; Kaser, Georg
2013-04-01
The mass balance and melt water production of glaciers is of particular interest in the Peruvian Andes where glacier melt water has markedly increased water supply during the pronounced dry seasons in recent decades. However, the melt water contribution from glaciers is projected to decrease with appreciable negative impacts on the local society within the coming decades. Understanding mass balance processes on tropical glaciers is a prerequisite for modeling present and future glacier runoff. As a first step towards this aim we applied a process-based surface mass balance model in order to calculate observed ablation at two stakes in the ablation zone of Shallap Glacier (4800 m a.s.l., 9°S) in the Cordillera Blanca, Peru. Under the tropical climate, the snow line migrates very frequently across most of the ablation zone all year round causing large temporal and spatial variations of glacier surface conditions and related ablation. Consequently, pronounced differences between the two chosen stakes and the two years were observed. Hourly records of temperature, humidity, wind speed, short wave incoming radiation, and precipitation are available from an automatic weather station (AWS) on the moraine near the glacier for the hydrological years 2006/07 and 2007/08 while stake readings are available at intervals of between 14 to 64 days. To optimize model parameters, we used 1000 model simulations in which the most sensitive model parameters were varied randomly within their physically meaningful ranges. The modeled surface height change was evaluated against the two stake locations in the lower ablation zone (SH11, 4760m) and in the upper ablation zone (SH22, 4816m), respectively. The optimal parameter set for each point achieved good model skill but if we transfer the best parameter combination from one stake site to the other stake site model errors increases significantly. The same happens if we optimize the model parameters for each year individually and transfer
A nitrogen mass balance for California
NASA Astrophysics Data System (ADS)
Liptzin, D.; Dahlgren, R. A.
2010-12-01
Human activities have greatly altered the global nitrogen cycle and these changes are apparent in water quality, air quality, ecosystem and human health. However, the relative magnitude of the sources of new reactive nitrogen and the fate of this nitrogen is not well established. Further, the biogeochemical aspects of the nitrogen cycle are often studied in isolation from the economic and social implications of all the transformations of nitrogen. The California Nitrogen Assessment is an interdisciplinary project whose aim is evaluating the current state of nitrogen science, practice, and policy in the state of California. Because of the close proximity of large population centers, highly productive and diverse agricultural lands and significant acreage of undeveloped land, California is a particularly interesting place for this analysis. One component of this assessment is developing a mass balance of nitrogen as well as identifying gaps in knowledge and quantifying uncertainty. The main inputs of new reactive nitrogen to the state are 1) synthetic nitrogen fertilizer, 2) biological nitrogen fixation, and 3) atmospheric nitrogen deposition. Permanent losses of nitrogen include 1) gaseous losses (N2, N2O, NHx, NOy), 2) riverine discharge, 3) wastewater discharge to the ocean, and 4) net groundwater recharge. A final term is the balance of food, feed, and fiber to support the human and animal populations. The largest input of new reactive nitrogen to California is nitrogen fertilizer, but both nitrogen fixation and atmospheric deposition contribute significantly. Non-fertilizer uses, such as the production of nylon and polyurethane, constitutes about 5% of the synthetic N synthesized production. The total nitrogen fixation in California is roughly equivalent on the 400,000 ha of alfalfa and the approximately 40 million ha of natural lands. In addition, even with highly productive agricultural lands, the large population of livestock, in particular dairy cows
Energy and mass balance in the three-phase interstellar medium
NASA Technical Reports Server (NTRS)
Wang, Zhong; Cowie, Lennox L.
1988-01-01
Details of the energy and mass balances are considered in the context of a three-phase interstellar medium. The rates of mass exchange between the different phases are derived based on the pressure variations created by supernova remnant expansions. It is shown that the pressure-confined warm and cold gases have stable temperatures under a variety of interstellar conditions. The three-phase quasi-static configuration is found to be a natural outcome, and both warm and cold phases generally contribute about half of the total mass density to the diffuse interstellar gas. The model is also likely to be self-regulatory in the sense that variations of the input parameters do not strongly alter the general result, which is consistent with most current observations. The consequences of extreme conditions on this model are considered, and the possible implications for interstellar medium in other galaxies are briefly discussed.
Mass balance for on-line alphakLa estimation in activated sludge oxidation ditch.
Chatellier, P; Audic, J M
2001-01-01
The capacity of an aeration system to transfer oxygen to a given activated sludge oxidation ditch is characterised by the alphakLa parameter. This parameter is difficult to measure under normal plant working conditions. Usually this measurement involves off-gas techniques or static mass balance. Therefore an on-line technique has been developed and tested in order to evaluate alphakLa. This technique deduces alphakLa from a data analysis of low cost sensor measurement: two flow meters and one oxygen probe. It involves a dynamic mass balance applied to aeration cycles selected according to given criteria. This technique has been applied to a wastewater treatment plant during four years. Significant variations of the alphakLa values have been detected while the number of blowers changes. This technique has been applied to another plant during two months.
Meng, Xianshuang; Bai, Hua; Guo, Teng; Niu, Zengyuan; Ma, Qiang
2017-12-15
Comprehensive identification and quantitation of 100 multi-class regulated ingredients in cosmetics was achieved using ultra-high-performance liquid chromatography (UHPLC) coupled with hybrid quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). A simple, efficient, and inexpensive sample pretreatment protocol was developed using ultrasound-assisted extraction (UAE), followed by dispersive solid-phase extraction (dSPE). The cosmetic samples were analyzed by UHPLC-Q-Orbitrap HRMS under synchronous full-scan MS and data-dependent MS/MS (full-scan MS 1 /dd-MS 2 ) acquisition mode. The mass resolution was set to 70,000 FWHM (full width at half maximum) for full-scan MS 1 and 17,500 FWHM for dd-MS 2 stage with the experimentally measured mass deviations of less than 2ppm (parts per million) for quasi-molecular ions and 5ppm for characteristic fragment ions for each individual analyte. An accurate-mass database and a mass spectral library were built in house for searching the 100 target compounds. Broad screening was conducted by comparing the experimentally measured exact mass of precursor and fragment ions, retention time, isotopic pattern, and ionic ratio with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. The developed methodology was evaluated and validated in terms of limits of detection (LODs), limits of quantitation (LOQs), linearity, stability, accuracy, and matrix effect. The UHPLC-Q-Orbitrap HRMS approach was applied for the analysis of 100 target illicit ingredients in 123 genuine cosmetic samples, and exhibited great potential for high-throughput, sensitive, and reliable screening of multi-class illicit compounds in cosmetics. Copyright © 2017 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Buri, P.; Steiner, J. F.; Miles, E.; Ragettli, S.; Pellicciotti, F.
2017-12-01
Supraglacial cliffs are typical surface features of debris-covered glaciers worldwide, affecting surface evolution, and mass balance by providing a direct ice-atmosphere interface where melt rates can be very high. As a result, ice cliffs act as windows of energy transfer from the atmosphere to the ice, and enhance melt and mass losses of otherwise insulated ice. However, their contribution to glacier mass balance has never been quantified at the glacier scale, and all inference has been obtained from upscaling results of point-scale models or observations at select individual cliffs. Here we use a 3D, physically-based backwasting model to estimate the volume losses associated with the melting and backwasting of supraglacial ice cliffs for the entire debris-covered glacier area of the Langtang catchment. We estimate mass losses for the 2014 melt season and compare them to recent values of glacier mass balance determined from geodetic and numerical modelling approached. Cliff outlines and topography are derived from high-resolution stereo SPOT6-imagery from April 2014. Meteorological data to force the model are provided by automatic weather stations on- and off-glacier within the valley. The model simulates ice cliff backwasting by considering the cliff-atmosphere energy-balance, reburial by debris and the effects of adjacent ponds. In the melt season of 2014, cliffs' distribution and patterns of mass losses vary considerably from glacier to glacier, and we relate rates of volume loss to both glaciers' and cliffs' characteristics. Only cliffs with a northerly aspect account for substantial losses. Uncertainty in our estimates is due to the quality of the stereo DEM, uncertainties in the cliff delineation and the fact that we use a conservative approach to cliff delineation and discard very small cliffs and those for which uncertainty in topography is high. Despite these uncertainties, our work presents the first estimate of the importance of supraglacial ice
LM-3: A High-resolution Lake Michigan Mass Balance Water Quality Model
This report is a user’s manual that describes the high-resolution mass balance model known as LM3. LM3 has been applied to Lake Michigan to describe the transport and fate of atrazine, PCB congeners, and chloride in that system. The model has also been used to model eutrophicat...
An overview of the Lake Michigan Mass Balance models were provided (eutrophication/nutrients, atrazine, mercury, and PCBs) with emphasis on the PCB model post-audit and forecast for Lake Trout. Provided were modeling construct, model description, and primary results. An assessm...
Surface mass balance model evaluation from satellite and airborne lidar mapping
NASA Astrophysics Data System (ADS)
Sutterley, T. C.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.
2016-12-01
We present estimates of Greenland Ice Sheet (GrIS) surface elevation change from a novel combination of satellite and airborne laser altimetry measurements. Our method combines measurements from the Airborne Topographic Mapper (ATM), the Land, Vegetation and Ice Sensor (LVIS) and ICESat-1 to generate elevation change rates at high spatial resolution. This method allows to extend the records of each instrument, increases the overall spatial coverage compared to a single instrument, and produces high-quality, coherent maps of surface elevation change. In addition by combining the lidar datasets, we are able to investigate seasonal and interannual surface elevation change for years where Spring and Fall Operation IceBridge campaigns are available. We validate our method by comparing with the standard NSIDC elevation change product calculated using overlapping Level-1B ATM data. We use the altimetry-derived mass changes to evaluate the uncertainty in surface mass balance, particularly in the runoff component, from two Regional Climate Models (RCM's), the Regional Atmospheric Climate Model (RACMO) and the Modéle Atmosphérique Régional (MAR), and one Global Climate Model (GCM), MERRA2/GEOS-5. We investigate locations with low ice sheet surface velocities that are within the estimated ablation zones of each regional climate model. We find that the surface mass balance outputs from RACMO and MAR show good correspondence with mass changes derived from surface elevation changes over long periods. At two sites in Northeast Greenland (NEGIS), the MAR model has better correspondence with the altimetry estimate. We find that the differences at these locations are primarily due to the characterization of meltwater refreeze within the ice sheet.
Accurate Mass Determination of Organotrifluoroborates
Petrillo, Daniel E.; Kohli, Rakesh K.; Molander, Gary A.
2007-01-01
Exact mass measurements were obtained for a variety of potassium- and tetra-n-butylammonium organotrifluoroborates using commercially available organic sulfate salts as internal reference standards. Accuracies were determined within 5 ppm using a sector ESI mass spectrometer operating in the negative ionization mode. PMID:17112738
Gao, Pin; Ding, Yunjie; Li, Hui; Xagoraraki, Irene
2012-06-01
Occurrence and removal efficiencies of fifteen pharmaceuticals were investigated in a conventional municipal wastewater treatment plant in Michigan. Concentrations of these pharmaceuticals were determined in both wastewater and sludge phases by a high-performance liquid chromatograph coupled to a tandem mass spectrometer. Detailed mass balance analysis was conducted during the whole treatment process to evaluate the contributing processes for pharmaceutical removal. Among the pharmaceuticals studied, demeclocycline, sulfamerazine, erythromycin and tylosin were not detected in the wastewater treatment plant influent. Other target pharmaceuticals detected in wastewater were also found in the corresponding sludge phase. The removal efficiencies of chlortetracycline, tetracycline, sulfamerazine, acetaminophen and caffeine were >99%, while doxycycline, oxytetracycline, sulfadiazine and lincomycin exhibited relatively lower removal efficiencies (e.g., <50%). For sulfamethoxazole, the removal efficiency was approximately 90%. Carbamazepine manifested a net increase of mass, i.e. 41% more than the input from the influent. Based on the mass balance analysis, biotransformation is believed to be the predominant process responsible for the removal of pharmaceuticals (22% to 99%), whereas contribution of sorption to sludge was relatively insignificant (7%) for the investigated pharmaceuticals. Copyright © 2012 Elsevier Ltd. All rights reserved.
REVIEW OF VOLATILE ORGANIC COMPOUND SOURCE APPORTIONMENT BY CHEMICAL MASS BALANCE. (R826237)
The chemical mass balance (CMB) receptor model has apportioned volatile organic compounds (VOCs) in more than 20 urban areas, mostly in the United States. These applications differ in terms of the total fraction apportioned, the calculation method, the chemical compounds used ...
ATMOSPHERIC MERCURY DEPOSITION TO LAKE MICHIGAN DURING THE LAKE MICHIGAN MASS BALANCE STUDY
Wet and dry mercury (Hg) deposition were calculated to Lake Michigan using a hybrid receptor modeling framework. The model utilized mercury monitoring data collected during the Lake Michigan Mass Balance Study and the Atmospheric Exchange Over Lakes and Oceans Study together w...
Progress toward Consensus Estimates of Regional Glacier Mass Balances for IPCC AR5
NASA Astrophysics Data System (ADS)
Arendt, A. A.; Gardner, A. S.; Cogley, J. G.
2011-12-01
Glaciers are potentially large contributors to rising sea level. Since the last IPCC report in 2007 (AR4), there has been a widespread increase in the use of geodetic observations from satellite and airborne platforms to complement field observations of glacier mass balance, as well as significant improvements in the global glacier inventory. Here we summarize our ongoing efforts to integrate data from multiple sources to arrive at a consensus estimate for each region, and to quantify uncertainties in those estimates. We will use examples from Alaska to illustrate methods for combining Gravity Recovery and Climate Experiment (GRACE), elevation differencing and field observations into a single time series with related uncertainty estimates. We will pay particular attention to reconciling discrepancies between GRACE estimates from multiple processing centers. We will also investigate the extent to which improvements in the glacier inventory affect the accuracy of our regional mass balances.
Tectonic controls on the long-term carbon isotope mass balance
Mills, Benjamin J. W.
2017-01-01
The long-term, steady-state marine carbon isotope record reflects changes to the proportional burial rate of organic carbon relative to total carbon on a global scale. For this reason, times of high δ13C are conventionally interpreted to be oxygenation events caused by excess organic burial. Here we show that the carbon isotope mass balance is also significantly affected by tectonic uplift and erosion via changes to the inorganic carbon cycle that are independent of changes to the isotopic composition of carbon input. This view is supported by inverse covariance between δ13C and a range of uplift proxies, including seawater 87Sr/86Sr, which demonstrates how erosional forcing of carbonate weathering outweighs that of organic burial on geological timescales. A model of the long-term carbon cycle shows that increases in δ13C need not be associated with increased organic burial and that alternative tectonic drivers (erosion, outgassing) provide testable and plausible explanations for sustained deviations from the long-term δ13C mean. Our approach emphasizes the commonly overlooked difference between how net and gross carbon fluxes affect the long-term carbon isotope mass balance, and may lead to reassessment of the role that the δ13C record plays in reconstructing the oxygenation of earth’s surface environment. PMID:28396434
Kim, Yong-Hyun; Kim, Ki-Hyun
2014-05-16
Accurate values for the Henry's law constants are essential to describe the environmental dynamics of a solute, but substantial errors are recognized in many reported data due to practical difficulties in measuring solubility and/or vapor pressure. Despite such awareness, validation of experimental approaches has scarcely been made. An experimental approach based on thermal desorption-gas chromatography-mass spectrometery (TD-GC-MS) method was developed to concurrently allow the accurate determination of target compounds from the headspace and aqueous samples in closed equilibrated system. The analysis of six aromatics and eight non-aromatic oxygenates was then carried out in a static headspace mode. An estimation of the potential bias and mass balance (i.e., sum of mass measured individually from gas and liquid phases vs. the mass initially added to the system) demonstrates compound-specific phase dependency so that the best results are obtained by aqueous (less soluble aromatics) and headspace analysis (more soluble non-aromatics). Accordingly, we were able to point to the possible sources of biases in previous studies and provide the best estimates for the Henry's constants (Matm(-1)): benzene (0.17), toluene (0.15), p-xylene (0.13), m-xylene (0.13), o-xylene (0.19), styrene (0.27); propionaldehyde (9.26), butyraldehyde (6.19), isovaleraldehyde (2.14), n-valeraldehyde (3.98), methyl ethyl ketone (10.5), methyl isobutyl ketone (3.93), n-butyl acetate (2.41), and isobutyl alcohol (22.2). Copyright © 2014 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Fischer, Mauro; Huss, Matthias; Kummert, Mario; Hoelzle, Martin
2016-06-01
Due to the relative lack of empirical field data, the response of very small glaciers (here defined as being smaller than 0.5 km2) to current atmospheric warming is not fully understood yet. Investigating their mass balance, e.g. using the direct glaciological method, is a prerequisite to fill this knowledge gap. Terrestrial laser scanning (TLS) techniques operating in the near infrared range can be applied for the creation of repeated high-resolution digital elevation models and consecutive derivation of annual geodetic mass balances of very small glaciers. This method is promising, as laborious and potentially dangerous field measurements as well as the inter- and extrapolation of point measurements can be circumvented. However, it still needs to be validated. Here, we present TLS-derived annual surface elevation and geodetic mass changes for five very small glaciers in Switzerland (Glacier de Prapio, Glacier du Sex Rouge, St. Annafirn, Schwarzbachfirn, and Pizolgletscher) and two consecutive years (2013/14-2014/15). The scans were acquired with a long-range Riegl -6000 especially designed for surveying snow- and ice-covered terrain. Zonally variable conversion factors for firn and bare ice surfaces were applied to convert geodetic volume to mass changes. We compare the geodetic results to direct glaciological mass balance measurements coinciding with the TLS surveys and assess the uncertainties and errors included in both methods. Average glacier-wide mass balances were negative in both years, showing stronger mass losses in 2014/15 (-1.65 m w.e.) compared to 2013/14 (-0.59 m w.e.). Geodetic mass balances were slightly less negative but in close agreement with the direct glaciological ones (R2 = 0.91). Due to the dense in situ measurements, the uncertainties in the direct glaciological mass balances were small compared to the majority of measured glaciers worldwide (±0.09 m w.e. yr-1 on average), and similar to uncertainties in the TLS-derived geodetic mass
Quantification of colloidal and aqueous element transfer in soils: The dual-phase mass balance model
Bern, Carleton R.; Thompson, Aaron; Chadwick, Oliver A.
2015-01-01
Mass balance models have become standard tools for characterizing element gains and losses and volumetric change during weathering and soil development. However, they rely on the assumption of complete immobility for an index element such as Ti or Zr. Here we describe a dual-phase mass balance model that eliminates the need for an assumption of immobility and in the process quantifies the contribution of aqueous versus colloidal element transfer. In the model, the high field strength elements Ti and Zr are assumed to be mobile only as suspended solids (colloids) and can therefore be used to distinguish elemental redistribution via colloids from redistribution via dissolved aqueous solutes. Calculations are based upon element concentrations in soil, parent material, and colloids dispersed from soil in the laboratory. We illustrate the utility of this model using a catena in South Africa. Traditional mass balance models systematically distort elemental gains and losses and changes in soil volume in this catena due to significant redistribution of Zr-bearing colloids. Applying the dual-phase model accounts for this colloidal redistribution and we find that the process accounts for a substantial portion of the major element (e.g., Al, Fe and Si) loss from eluvial soil. In addition, we find that in illuvial soils along this catena, gains of colloidal material significantly offset aqueous elemental loss. In other settings, processes such as accumulation of exogenous dust can mimic the geochemical effects of colloid redistribution and we suggest strategies for distinguishing between the two. The movement of clays and colloidal material is a major process in weathering and pedogenesis; the mass balance model presented here is a tool for quantifying effects of that process over time scales of soil development.
Climate, not atmospheric deposition, drives the biogeochemical mass-balance of a mountain watershed
Baron, Jill S.; Heath, Jared
2014-01-01
Watershed mass-balance methods are valuable tools for demonstrating impacts to water quality from atmospheric deposition and chemical weathering. Owen Bricker, a pioneer of the mass-balance method, began applying mass-balance modeling to small watersheds in the late 1960s and dedicated his career to expanding the literature and knowledge of complex watershed processes. We evaluated long-term trends in surface-water chemistry in the Loch Vale watershed, a 660-ha. alpine/subalpine catchment located in Rocky Mountain National Park, CO, USA. Many changes in surface-water chemistry correlated with multiple drivers, including summer or monthly temperature, snow water equivalent, and the runoff-to-precipitation ratio. Atmospheric deposition was not a significant causal agent for surface-water chemistry trends. We observed statistically significant increases in both concentrations and fluxes of weathering products including cations, SiO2, SO4 2−, and ANC, and in inorganic N, with inorganic N being primarily of atmospheric origin. These changes are evident in the individual months June, July, and August, and also in the combined June, July, and August summer season. Increasingly warm summer temperatures are melting what was once permanent ice and this may release elements entrained in the ice, stimulate chemical weathering with enhanced moisture availability, and stimulate microbial nitrification. Weathering rates may also be enhanced by sustained water availability in high snowpack years. Rapid change in the flux of weathering products and inorganic N is the direct and indirect result of a changing climate from warming temperatures and thawing cryosphere.
MICHTOX: A MASS BALANCE AND BIOACCUMULATION MODEL FOR TOXIC CHEMICALS IN LAKE MICHIGAN
MICHTOX is a toxic chemical mass balance and bioaccumulation model for Lake Michigan. It was developed for USEPA's Region V in support of the Lake Michigan Lake-wide Management Plan (LaMP) to provide guidance on expected water quality improvements in response to critical pollutan...
Development of a mass balance model for estimating PCB export from the lower Fox River to Green Bay
DOE Office of Scientific and Technical Information (OSTI.GOV)
Velleux, M.; Endicott, D.
A mass balance approach was used to model contaminant cycling in the lower Fox River from the DePere Dam to Green Bay. The objectives of this research were (1) to estimate present contaminant export from the Fox River to Green Bay, and (2) to quantify contaminant transport and fate pathways in the lower river for the study period. Specifically, a model describing the transport, fate, and export of chlorides, total suspended solids, total PCBs, and six PCB congeners for the lower Fox River was developed. Field data collected as part of the U.S. Environmental Protection Agency's Green Bay Mass Balancemore » Study were used to calibrate the model. Model results suggest that the transport of inplace pollutants significantly contributed to the cumulative export of total PCBs over this period. Estimated total PCB transport in the Fox River during 1989 increased 60% between the dam and river mouth due to the resuspension of lower river sediments. Total suspended solids and PCB predictions are most sensitive to particle transport parameters, particularly the settling and resuspension velocities. The significant components of the total PCB mass balance are import (loading over the DePere Dam), settling, resuspension, and export to Green Bay. Volatilization, porewater transport, and point source input were not significant to the mass balance. Present point source discharges to the river are not significant total PCB sources, collectively contributing less than 6 kg of PCB to the river during the mass balance period.« less
Fatty acids composition of Caenorhabditis elegans using accurate mass GCMS-QTOF
Henry, Parise; Owopetu, Olufunmilayo; Adisa, Demilade; Nguyen, Thao; Anthony, Kevin; Ijoni-Animadu, David; Jamadar, Sakha; Abdel-Rahman, Fawzia; Saleh, Mahmoud A.
2016-01-01
The free living nematode Caenorhabditis elegans is a proven model organism for lipid metabolism research. Total lipids of C. elegans were extracted using chloroform, methanol 2:1(v/v). Fatty acids composition of the extracted total lipids were converted to their corresponding methyl esters (FAMEs) and analyzed by gas chromatography/accurate mass quadrupole time of flight mass spectrometry (GCMS-QTOF) using both electron ionization (EI) and chemical ionization (CI) techniques. 28 fatty acids consisting of 12 to 22 carbon atoms were identified, 65% of them were unsaturated. Fatty acids containing 12 to 17 carbons were mostly saturated with stearic acid (18:0) as the major constituent. Several branched-chain fatty acids were identified. Methyl-14-methylhexadecanoate (iso-17:0) was the major identified branched fatty acid. This is the first report to detect the intact molecular parent ions of the identified fatty acids using chemical ionization compared to electron ionization which produced fragmentations of the fatty acids methyl esters (FAMEs). PMID:27166662
NASA Astrophysics Data System (ADS)
Shean, D. E.; Arendt, A. A.; Osmanoglu, B.; Montesano, P.
2017-12-01
High Mountain Asia (HMA) constitutes the largest glacierized region outside of the Earth's polar regions. Although available observations are limited, long-term records indicate sustained regional glacier mass loss since 1850, with increased loss in recent decades. Recent satellite data (e.g., GRACE, ICESat-1) show spatially variable glacier mass balance, with significant mass loss in the Himalaya and Hindu Kush and slight mass gain in the Karakoram. We generated 4000 high-resolution digital elevation models (DEMs) from sub-meter commercial stereo imagery (DigitalGlobe WorldView/GeoEye) acquired over glaciers in High-mountain Asia from 2002-present (mostly 2013-present). We produced a regional 8-m DEM mosaic for 2015 and estimated 15-year geodetic mass balance for 40000 glaciers larger than 0.1 km2. We are combining with other regional DEM sources to systematically document the spatiotemporal evolution of glacier mass balance for the entire HMA region. We also generated monthly to interannual DEM and velocity time series for high-priority sites distributed across the region, with >15-20 DEMs available for some locations from 2010-present. These records document glacier dynamics, seasonal snow accumulation/redistribution, and processes that affect glacier mass balance (e.g., ice-cliff retreat, debris cover evolution). These efforts will provide basin-scale assessments of snow/ice melt runoff contributions for model cal/val and downstream water resources applications. We will continue processing all archived and newly available commercial stereo imagery for HMA, and will release all DEMs through the HiMAT DAAC.
Sustainability of algae derived biodiesel: a mass balance approach.
Pfromm, Peter H; Amanor-Boadu, Vincent; Nelson, Richard
2011-01-01
A rigorous chemical engineering mass balance/unit operations approach is applied here to bio-diesel from algae mass culture. An equivalent of 50,000,000 gallons per year (0.006002 m3/s) of petroleum-based Number 2 fuel oil (US, diesel for compression-ignition engines, about 0.1% of annual US consumption) from oleaginous algae is the target. Methyl algaeate and ethyl algaeate diesel can according to this analysis conceptually be produced largely in a technologically sustainable way albeit at a lower available diesel yield. About 11 square miles of algae ponds would be needed with optimistic assumptions of 50 g biomass yield per day and m2 pond area. CO2 to foster algae growth should be supplied from a sustainable source such as a biomass-based ethanol production. Reliance on fossil-based CO2 from power plants or fertilizer production renders algae diesel non-sustainable in the long term. Copyright © 2010 Elsevier Ltd. All rights reserved.
Nasrullah, Muhammad; Vainikka, Pasi; Hannula, Janne; Hurme, Markku; Kärki, Janne
2015-02-01
This is the third and final part of the three-part article written to describe the mass, energy and material balances of the solid recovered fuel production process produced from various types of waste streams through mechanical treatment. This article focused the production of solid recovered fuel from municipal solid waste. The stream of municipal solid waste used here as an input waste material to produce solid recovered fuel is energy waste collected from households of municipality. This article presents the mass, energy and material balances of the solid recovered fuel production process. These balances are based on the proximate as well as the ultimate analysis and the composition determination of various streams of material produced in a solid recovered fuel production plant. All the process streams are sampled and treated according to CEN standard methods for solid recovered fuel. The results of the mass balance of the solid recovered fuel production process showed that 72% of the input waste material was recovered in the form of solid recovered fuel; 2.6% as ferrous metal, 0.4% as non-ferrous metal, 11% was sorted as rejects material, 12% as fine faction and 2% as heavy fraction. The energy balance of the solid recovered fuel production process showed that 86% of the total input energy content of input waste material was recovered in the form of solid recovered fuel. The remaining percentage (14%) of the input energy was split into the streams of reject material, fine fraction and heavy fraction. The material balances of this process showed that mass fraction of paper and cardboard, plastic (soft) and wood recovered in the solid recovered fuel stream was 88%, 85% and 90%, respectively, of their input mass. A high mass fraction of rubber material, plastic (PVC-plastic) and inert (stone/rock and glass particles) was found in the reject material stream. © The Author(s) 2014.
Application of the accurate mass and time tag approach in studies of the human blood lipidome
Ding, Jie; Sorensen, Christina M.; Jaitly, Navdeep; Jiang, Hongliang; Orton, Daniel J.; Monroe, Matthew E.; Moore, Ronald J.; Smith, Richard D.; Metz, Thomas O.
2008-01-01
We report a preliminary demonstration of the accurate mass and time (AMT) tag approach for lipidomics. Initial data-dependent LC-MS/MS analyses of human plasma, erythrocyte, and lymphocyte lipids were performed in order to identify lipid molecular species in conjunction with complementary accurate mass and isotopic distribution information. Identified lipids were used to populate initial lipid AMT tag databases containing 250 and 45 entries for those species detected in positive and negative electrospray ionization (ESI) modes, respectively. The positive ESI database was then utilized to identify human plasma, erythrocyte, and lymphocyte lipids in high-throughput LC-MS analyses based on the AMT tag approach. We were able to define the lipid profiles of human plasma, erythrocytes, and lymphocytes based on qualitative and quantitative differences in lipid abundance. PMID:18502191
NASA Astrophysics Data System (ADS)
Barandun, Martina; Huss, Matthias; Usubaliev, Ryskul; Azisov, Erlan; Berthier, Etienne; Kääb, Andreas; Bolch, Tobias; Hoelzle, Martin
2018-06-01
Glacier surface mass balance observations in the Tien Shan and Pamir are relatively sparse and often discontinuous. Nevertheless, glaciers are one of the most important components of the high-mountain cryosphere in the region as they strongly influence water availability in the arid, continental and intensely populated downstream areas. This study provides reliable and continuous surface mass balance series for selected glaciers located in the Tien Shan and Pamir-Alay. By cross-validating the results of three independent methods, we reconstructed the mass balance of the three benchmark glaciers, Abramov, Golubin and Glacier no. 354 for the past 2 decades. By applying different approaches, it was possible to compensate for the limitations and shortcomings of each individual method. This study proposes the use of transient snow line observations throughout the melt season obtained from satellite optical imagery and terrestrial automatic cameras. By combining modelling with remotely acquired information on summer snow depletion, it was possible to infer glacier mass changes for unmeasured years. The model is initialized with daily temperature and precipitation data collected at automatic weather stations in the vicinity of the glacier or with adjusted data from climate reanalysis products. Multi-annual mass changes based on high-resolution digital elevation models and in situ glaciological surveys were used to validate the results for the investigated glaciers. Substantial surface mass loss was confirmed for the three studied glaciers by all three methods, ranging from -0.30 ± 0.19 to -0.41 ± 0.33 m w.e. yr-1 over the 2004-2016 period. Our results indicate that integration of snow line observations into mass balance modelling significantly narrows the uncertainty ranges of the estimates. Hence, this highlights the potential of the methodology for application to unmonitored glaciers at larger scales for which no direct measurements are available.
Mayo, Lawrence R.; Trabant, Dennis C.; March, Rod S.
2004-01-01
Scientific measurements at Wolverine Glacier, on the Kenai Peninsula in south-central Alaska, began in April 1966. At three long-term sites in the research basin, the measurements included snow depth, snow density, heights of the glacier surface and stratigraphic summer surfaces on stakes, and identification of the surface materials. Calculations of the mass balance of the surface strata-snow, new firn, superimposed ice, and old firn and ice mass at each site were based on these measurements. Calculations of fixed-date annual mass balances for each hydrologic year (October 1 to September 30), as well as net balances and the dates of minimum net balance measured between time-transgressive summer surfaces on the glacier, were made on the basis of the strata balances augmented by air temperature and precipitation recorded in the basin. From 1966 through 1995, the average annual balance at site A (590 meters altitude) was -4.06 meters water equivalent; at site B (1,070 meters altitude), was -0.90 meters water equivalent; and at site C (1,290 meters altitude), was +1.45 meters water equivalent. Geodetic determination of displacements of the mass balance stake, and glacier surface altitudes was added to the data set in 1975 to detect the glacier motion responses to variable climate and mass balance conditions. The average surface speed from 1975 to 1996 was 50.0 meters per year at site A, 83.7 meters per year at site B, and 37.2 meters per year at site C. The average surface altitudes were 594 meters at site A, 1,069 meters at site B, and 1,293 meters at site C; the glacier surface altitudes rose and fell over a range of 19.4 meters at site A, 14.1 meters at site B, and 13.2 meters at site C.
NASA Astrophysics Data System (ADS)
Dussaillant, Inés; Berthier, Etienne; Brun, Fanny
2018-02-01
We compare two independent estimates of the rate of elevation change and geodetic mass balance of the Northern Patagonian Icefield (NPI) between 2000 (3856 km²) and 2012 (3740 km²) from space-borne data. The first is obtained by differencing the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) from February 2000 and a Satellite pour l’Observation de la Terre 5 (SPOT5) DEM from March 2012. The second is deduced by fitting pixel-based linear elevation trends over 118 DEMs calculated from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) stereo images acquired between 2000 and 2012. Both methods lead to similar and strongly negative icefield-wide mass balances of -1.02±0.21 and -1.06±0.14 m w.e. yr-1 respectively, which is in agreement with earlier studies. Contrasting glacier responses are observed, with individual glacier mass balances ranging from -0.15 to -2.30 m w.e. yr-1 (standard deviation = 0.49 m w.e. yr-1; N = 38). For individual glaciers, the two methods agree within error bars, except for small glaciers poorly sampled in the SPOT5 DEM due to clouds. Importantly, our study confirms the lack of penetration of the C-band SRTM radar signal into the NPI snow and firn except for a region above 2900 m a.s.l. covering less than 1% of the total area. Ignoring penetration would bias the mass balance by only 0.005 m w.e. yr-1. A strong advantage of the ASTER method is that it relies only on freely available data and can thus be extended to other glacierized areas.
NASA Astrophysics Data System (ADS)
de la Peña, S.; Howat, I.; Behar, A.; Price, S. F.; Thanga, J.; Crowell, J. M.; Huseas, S.; Tedesco, M.
2016-12-01
Observations made in recent years by repeated altimetry from CryoSat-2 and NASA's Operation IceBridge reveal large fluctuations in the firn volume of the Greenland Ice Sheet. Although an order of magnitude smaller than ice thinning rates observed in some areas at the margins of the ice sheet, short-term departures in surface elevation trends occur over most of the accumulation zone of Greenland. Changes in the thickness of the firn column are influenced by variability in surface mass balance, firn compaction, and abrupt seasonal densification near the surface caused by refreezing at depth of variable amounts of surface meltwater in the summer. These processes and dynamic thinning cannot be differentiated from each other by altimetry alone. Until recently, nearly all information on density and surface mass balance changes over the firn layer came from ice core and snow pit stratigraphy that provided annual rates with relatively large uncertainties. Here we present direct, continuous measurements of firn density and surface mass balance along with annual estimates of firn ice content used to assess observed elevation change in the percolation zone of western Greenland in relation to firn processes. Since 2012, autonomous in-situ firn compaction sensors have monitored several sites in the catchment area of Jakobshavn Isbrae, and since 2015 surface mass balance and surface displacement has been measured continuously using a combination of sensors. In addition to identify the different components in the altimetry signal, The temporal resolution of the data acquired provide a means to monitor short-term changes in the near-surface firn, and identifying individual events causing surface elevation displacement.
Maintaining Atmospheric Mass and Water Balance Within Reanalysis
NASA Technical Reports Server (NTRS)
Takacs, Lawrence L.; Suarez, Max; Todling, Ricardo
2015-01-01
This report describes the modifications implemented into the Goddard Earth Observing System Version-5 (GEOS-5) Atmospheric Data Assimilation System (ADAS) to maintain global conservation of dry atmospheric mass as well as to preserve the model balance of globally integrated precipitation and surface evaporation during reanalysis. Section 1 begins with a review of these global quantities from four current reanalysis efforts. Section 2 introduces the modifications necessary to preserve these constraints within the atmospheric general circulation model (AGCM), the Gridpoint Statistical Interpolation (GSI) analysis procedure, and the Incremental Analysis Update (IAU) algorithm. Section 3 presents experiments quantifying the impact of the new procedure. Section 4 shows preliminary results from its use within the GMAO MERRA-2 Reanalysis project. Section 5 concludes with a summary.
Camarillo, Mary Kay; Stringfellow, William T; Spier, Chelsea L; Hanlon, Jeremy S; Domen, Jeremy K
2013-10-15
Anaerobic digestion of manure and other agricultural waste streams with subsequent energy production can result in more sustainable dairy operations; however, importation of digester feedstocks onto dairy farms alters previously established carbon, nutrient, and salinity mass balances. Salt and nutrient mass balance must be maintained to avoid groundwater contamination and salination. To better understand salt and nutrient contributions of imported methane-producing substrates, a mass balance for a full-scale dairy biomass energy project was developed for solids, carbon, nitrogen, sulfur, phosphorus, chloride, and potassium. Digester feedstocks, consisting of thickened manure flush-water slurry, screened manure solids, sudan grass silage, and feed-waste, were tracked separately in the mass balance. The error in mass balance closure for most elements was less than 5%. Manure contributed 69.2% of influent dry matter while contributing 77.7% of nitrogen, 90.9% of sulfur, and 73.4% of phosphorus. Sudan grass silage contributed high quantities of chloride and potassium, 33.3% and 43.4%, respectively, relative to the dry matter contribution of 22.3%. Five potential off-site co-digestates (egg waste, grape pomace, milk waste, pasta waste, whey wastewater) were evaluated for anaerobic digestion based on salt and nutrient content in addition to bio-methane potential. Egg waste and wine grape pomace appeared the most promising co-digestates due to their high methane potentials relative to bulk volume. Increasing power production from the current rate of 369 kW to the design value of 710 kW would require co-digestion with either 26800 L d(-1) egg waste or 60900 kg d(-1) grape pomace. However, importation of egg waste would more than double nitrogen loading, resulting in an increase of 172% above the baseline while co-digestion with grape pomace would increase potassium by 279%. Careful selection of imported co-digestates and management of digester effluent is required to
Thurman, E.M.; Ferrer, I.; Parry, R.
2002-01-01
Degradates of acetochlor and alachlor (ethanesulfonic acids, ESAs) were analyzed in both standards and in a groundwater sample using high-performance liquid chromatography-time-of-flight mass spectrometry with electrospray ionization. The negative pseudomolecular ion of the secondary amide of acetochlor ESA and alachlor ESA gave average masses of 256.0750??0.0049 amu and 270.0786??0.0064 amu respectively. Acetochlor and alachlor ESA gave similar masses of 314.1098??0.0061 amu and 314.1153??0.0048 amu; however, they could not be distinguished by accurate mass because they have the same empirical formula. On the other hand, they may be distinguished using positive-ion electrospray because of different fragmentation spectra, which did not occur using negative-ion electrospray.
Thurman, E.M.; Ferrer, Imma; Parry, R.
2002-01-01
Degradates of acetochlor and alachlor (ethanesulfonic acids, ESAs) were analyzed in both standards and in a groundwater sample using high-performance liquid chromatography-time-of-flight mass spectrometry with electrospray ionization. The negative pseudomolecular ion of the secondary amide of acetochlor ESA and alachlor ESA gave average masses of 256.0750+/-0.0049 amu and 270.0786+/-0.0064 amu respectively. Acetochlor and alachlor ESA gave similar masses of 314.1098+/-0.0061 amu and 314.1153+/-0.0048 amu; however, they could not be distinguished by accurate mass because they have the same empirical formula. On the other hand, they may be distinguished using positive-ion electrospray because of different fragmentation spectra, which did not occur using negative-ion electrospray.
NASA Astrophysics Data System (ADS)
Velicogna, I.; Sutterley, T. C.; A, G.; van den Broeke, M. R.; Ivins, E. R.
2016-12-01
We use Gravity Recovery and Climate Experiment (GRACE) monthly gravity fields to determine the regional acceleration in ice mass loss in Antarctica for 2002-2016. We find that the total mass loss is controlled by only a few regions. In Antarctica, the Amundsen Sea (AS) sector and the Antarctic Peninsula account for 65% and 18%, respectively, of the total loss (186 ± 10 Gt/yr) mainly from ice dynamics. The AS sector contributes most of the acceleration in loss (9 ± 1 Gt/yr2 ), and Queen Maud Land, East Antarctica, is the only sector with a significant mass gain due to a local increase in SMB (57 ± 5 Gt/yr). We compare GRACE regional mass balance estimates with independent estimates from ICESat-1 and Operation IceBridge laser altimetry, CryoSat-2 radar altimetry, and surface mass balance outputs from RACMO2.3. In the Amundsen Sea Embayment of West Antarctica, an area experiencing rapid retreat and mass loss to the sea, we find good agreement between GRACE and altimetry estimates. Comparison of GRACE with these independent techniques in East Antarctic shows that GIA estimates from the new regional ice deglaciation models underestimate the GIA correction in the EAIS interior, which implies larger losses of the Antarctica ice sheet by about 70 Gt/yr. Sectors where we are observing the largest losses are closest to warm circumpolar water, and with polar constriction of the westerlies enhanced by climate warming, we expect these sectors to contribute more and more to sea level as the ice shelves that protect these glaciers will melt faster in contact with more heat from the surrounding oc
Ochiai, Nobuo; Mitsui, Kazuhisa; Sasamoto, Kikuo; Yoshimura, Yuta; David, Frank; Sandra, Pat
2014-09-05
A method is developed for identification of sulfur compounds in tobacco smoke extract. The method is based on large volume injection (LVI) of 10μL of tobacco smoke extract followed by selectable one-dimensional ((1)D) or two-dimensional ((2)D) gas chromatography (GC) coupled to a hybrid quadrupole time-of-flight mass spectrometer (Q-TOF-MS) using electron ionization (EI) and positive chemical ionization (PCI), with parallel sulfur chemiluminescence detection (SCD). In order to identify each individual sulfur compound, sequential heart-cuts of 28 sulfur fractions from (1)D GC to (2)D GC were performed with the three MS detection modes (SCD/EI-TOF-MS, SCD/PCI-TOF-MS, and SCD/PCI-Q-TOF-MS). Thirty sulfur compounds were positively identified by MS library search, linear retention indices (LRI), molecular mass determination using PCI accurate mass spectra, formula calculation using EI and PCI accurate mass spectra, and structure elucidation using collision activated dissociation (CAD) of the protonated molecule. Additionally, 11 molecular formulas were obtained for unknown sulfur compounds. The determined values of the identified and unknown sulfur compounds were in the range of 10-740ngmg total particulate matter (TPM) (RSD: 1.2-12%, n=3). Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.
Constrained Allocation Flux Balance Analysis
Mori, Matteo; Hwa, Terence; Martin, Olivier C.
2016-01-01
New experimental results on bacterial growth inspire a novel top-down approach to study cell metabolism, combining mass balance and proteomic constraints to extend and complement Flux Balance Analysis. We introduce here Constrained Allocation Flux Balance Analysis, CAFBA, in which the biosynthetic costs associated to growth are accounted for in an effective way through a single additional genome-wide constraint. Its roots lie in the experimentally observed pattern of proteome allocation for metabolic functions, allowing to bridge regulation and metabolism in a transparent way under the principle of growth-rate maximization. We provide a simple method to solve CAFBA efficiently and propose an “ensemble averaging” procedure to account for unknown protein costs. Applying this approach to modeling E. coli metabolism, we find that, as the growth rate increases, CAFBA solutions cross over from respiratory, growth-yield maximizing states (preferred at slow growth) to fermentative states with carbon overflow (preferred at fast growth). In addition, CAFBA allows for quantitatively accurate predictions on the rate of acetate excretion and growth yield based on only 3 parameters determined by empirical growth laws. PMID:27355325
NASA Astrophysics Data System (ADS)
Villamil-Otero, G.; Zhang, J.; Yao, Y.
2017-12-01
The Antarctic Peninsula (AP) has long been the focus of climate change studies due to its rapid environmental changes such as significantly increased glacier melt and retreat, and ice-shelf break-up. Progress has been continuously made in the use of regional modeling to simulate surface mass changes over ice sheets. Most efforts, however, focus on the ice sheets of Greenland with considerable fewer studies in Antarctica. In this study the Weather Research and Forecasting (WRF) model, which has been applied to the Antarctic region for weather modeling, is adopted to capture the past and future surface mass balance changes over AP. In order to enhance the capabilities of WRF model simulating surface mass balance over the ice surface, we implement various ice and snow processes within the WRF and develop a new WRF suite (WRF-Ice). The WRF-Ice includes a thermodynamic ice sheet model that improves the representation of internal melting and refreezing processes and the thermodynamic effects over ice sheet. WRF-Ice also couples a thermodynamic sea ice model to improve the simulation of surface temperature and fluxes over sea ice. Lastly, complex snow processes are also taken into consideration including the implementation of a snowdrift model that takes into account the redistribution of blowing snow as well as the thermodynamic impact of drifting snow sublimation on the lower atmospheric boundary layer. Intensive testing of these ice and snow processes are performed to assess the capability of WRF-Ice in simulating the surface mass balance changes over AP.
Blair, Benjamin; Nikolaus, Adam; Hedman, Curtis; Klaper, Rebecca; Grundl, Timothy
2015-09-01
Conventional activated sludge (CAS) wastewater treatment processes are insufficient at removing many pharmaceutical and personal care products (PPCPs) from wastewater. In addition, negative mass balances, where the effluent concentration is greater than the influent concentration, have been observed in wastewater treatment studies and a further understanding of these results is needed. In this study, the fate and occurrence of 57 PPCPs and hormones were evaluated in an activated sludge process and the mass balances were determined. The goal of the project was to understand the PPCPs biological degradation and the extent of sorption to solids. The samples containing in situ PPCPs (i.e. samples were not spiked with additional PPCPs) were evaluated. Forty-eight of the PPCPs were detected in the soluble form and 29 were detected sorbed to solids. Two notable results were found. First, the results of this study indicate a subset of the highly biodegradable PPCPs stop being degraded at low, yet notable, concentrations. Second, the results revealed that negative mass balances were present for a subset of the PPCPs when evaluating both the soluble and sorbed concentration, for example carbamazepine and ofloxacin. Desorption from solids was not found to attribute to negative mass balances. Overall, the results from this study provide new insights into the fate of PPCPs during CAS wastewater treatment by evaluating the degradation kinetics and sorption and the results may explain the consistent levels of highly degradable PPCPs being emitted from WWTPs worldwide. Copyright © 2015 Elsevier Ltd. All rights reserved.
Racault, Y; Stricker, A-E; Husson, A; Gillot, S
2011-01-01
Oxygen transfer in biological wastewater treatment processes with high sludge concentration, such as membrane bioreactor (MBR), is an important issue. The variation of alpha-factor versus mixed liquor suspended solids (MLSS) concentration was investigated in a full scale MBR plant under process conditions, using mass balances. Exhaustive data from the Supervisory Control And Data Acquisition (SCADA) and from additional online sensors (COD, DO, MLSS) were used to calculate the daily oxygen consumption (OC) using a non-steady state mass balance for COD and total N on a 24-h basis. To close the oxygen balance, OC has to match the total oxygen transfer rate (OTRtot) of the system, which is provided by fine bubble (FB) diffusers in the aeration tank and coarse bubbles (CB) in separate membrane tanks. First assessing OTR(CB) then closing the balance OC = OTRtot allowed to calculate OTR(FB) and to fit an exponential relationship between OTR(FB) and MLSS. A comparison of the alpha-factor obtained by this balance method and by direct measurements with the off-gas method on the same plant is presented and discussed.
A Range Correction for Icesat and Its Potential Impact on Ice-sheet Mass Balance Studies
NASA Technical Reports Server (NTRS)
Borsa, A. A.; Moholdt, G.; Fricker, H. A.; Brunt, Kelly M.
2014-01-01
We report on a previously undocumented range error in NASA's Ice, Cloud and land Elevation Satellite (ICESat) that degrades elevation precision and introduces a small but significant elevation trend over the ICESat mission period. This range error (the Gaussian-Centroid or 'G-C'offset) varies on a shot-to-shot basis and exhibits increasing scatter when laser transmit energies fall below 20 mJ. Although the G-C offset is uncorrelated over periods less than1 day, it evolves over the life of each of ICESat's three lasers in a series of ramps and jumps that give rise to spurious elevation trends of -0.92 to -1.90 cm yr(exp -1), depending on the time period considered. Using ICESat data over the Ross and Filchner-Ronne ice shelves we show that (1) the G-C offset introduces significant biases in ice-shelf mass balance estimates, and (2) the mass balance bias can vary between regions because of different temporal samplings of ICESat.We can reproduce the effect of the G-C offset over these two ice shelves by fitting trends to sample-weighted mean G-C offsets for each campaign, suggesting that it may not be necessary to fully repeat earlier ICESat studies to determine the impact of the G-C offset on ice-sheet mass balance estimates.
Jason R. Price; Michael A. Velbel; Lina C. Patino
2005-01-01
Rates of clay formation in three watersheds located at the Coweeta Hydrologic Laboratory, western North Carolina, have been determined from solute flux-based mass balance methods. A system of mass balance equations with enough equations and unknowns to allow calculation of secondary mineral formation rates as well as the more commonly determined primary-...
Mass balance of Djankuat Glacier, Central Caucasus: observations, modeling and prediction
NASA Astrophysics Data System (ADS)
Rybak, Oleg; Mariia, Kaminskaia; Stanislav, Kutuzov; Ivan, Lavrentiev; Polina, Morozova; Victor, Popovnin; Elena, Rybak
2017-04-01
Djankuat is a typical valley glacier on the northern slope of the main Caucasus chain. Its present day area is approximately 2.5 square km with the characteristic ice thickness of several tens of meters. As well as other glaciers in the region, Djankuat has been shrinking during the last several decades, its cumulative mass balance in 1968-2016 was equal to -13.6 m w.e. In general, Caucasus' glaciers lost approximately one-third of their area and half of the volume. Prediction of further deradation of glaciers in changing environment is a challenging task because rivers fed by glacier melt water provide from 40 to 70% of the total river run-off in the adjacent piedmont territories. Growing demand in fresh water is rather critical for the local economy development and for growing population, motivating elaboration of an effitient instrument for evaluation and forecasting of the glaciation in the Greater Caucasus. Unfortunately, systematic observations are sparse limiting possibilities for proper model development for the most of the glaciers. Under these circumstances, we have to rely on the models developed for the few well-studied ones, like Djankuat, which is probably one of the most explored glaciers in the world. Accumulation and ablation rates have been observed here systematically and uninterruptedly since mid 60-ies using dense stake network. Together with the mass balance components, changes in flow velocity, ice thickness and geometry were regularly evaluated. During the last several ablation seasons, direct meteorological observations were carried out using an AMS. Long series of meteorological observations at the nearest weather station allow making assessment of the glacier response to climate change in the second half of the 20th century. Abundant observation data gave us the opportunity to elaborate, calibrate and validate an efficient mathematical model of surface mass balance of a typical glacier in the region. Since many glaciers in the Caucasus
NASA Astrophysics Data System (ADS)
Falk, Ulrike; López, Damián A.; Silva-Busso, Adrián
2018-04-01
The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP). This region was subject to strong warming trends in the atmospheric surface layer. Surface air temperature increased about 3 K in 50 years, concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. The positive trend in surface air temperature has currently come to a halt. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K (100 m)-1) and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns. The increased mesocyclonic activity during the wintertime over the past decades in the study area results in intensified advection of warm, moist air with high temperatures and rain and leads to melt conditions on the ice cap, fixating surface air temperatures to the melting point. Its impact on winter accumulation results in the observed negative mass balance estimates. Six years of continuous glaciological measurements on mass balance stake transects as well as 5 years of climatological data time series are presented and a spatially distributed glacier energy balance melt model adapted and run based on these multi-year data sets. The glaciological surface mass balance model is generally in good agreement with observations, except for atmospheric conditions promoting snow drift by high wind speeds, turbulence-driven snow deposition and snow layer erosion by rain. No drift in the difference between simulated mass balance and mass balance measurements can be seen over the course of the 5-year model run period. The winter accumulation does not suffice to compensate for the high variability in summer ablation. The results are analysed to assess changes in meltwater input to the coastal waters, specific glacier mass balance and the equilibrium line altitude (ELA). The Fourcade Glacier catchment drains
Hogenboom, A C; van Leerdam, J A; de Voogt, P
2009-01-16
The European Reach legislation will possibly drive producers to develop newly designed chemicals that will be less persistent, bioaccumulative or toxic. If this innovation leads to an increased use of more hydrophilic chemicals it may result in higher mobilities of chemicals in the aqueous environment. As a result, the drinking water companies may face stronger demands on removal processes as the hydrophilic compounds inherently are more difficult to remove. Monitoring efforts will also experience a shift in focus to more water-soluble compounds. Screening source waters on the presence of (emerging) contaminants is an essential step in the control of the water cycle from source to tap water. In this article, some of our experiences are presented with the hybrid linear ion trap (LTQ) FT Orbitrap mass spectrometer, in the area of chemical water analysis. A two-pronged strategy in mass spectrometric research was employed: (i) exploring effluent, surface, ground- and drinking-water samples searching for accurate masses corresponding to target compounds (and their product ions) known from, e.g. priority lists or the scientific literature and (ii) full-scan screening of water samples in search of 'unknown' or unexpected masses, followed by MS(n) experiments to elucidate the structure of the unknowns. Applications of both approaches to emerging water contaminants are presented and discussed. Results are presented for target analysis search for pharmaceuticals, benzotriazoles, illicit drugs and for the identification of unknown compounds in a groundwater sample and in a polar extract of a landfill soil sample (a toxicity identification evaluation bioassay sample). The applications of accurate mass screening and identification described in this article demonstrate that the LC-LTQ FT Orbitrap MS is well equipped to meet the challenges posed by newly emerging polar contaminants.
Changes in ice dynamics and mass balance of the Antarctic ice sheet.
Rignot, Eric
2006-07-15
The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 degrees C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.
Geodetic glacier mass balancing on ice caps - inseparably connected to firn modelling?
NASA Astrophysics Data System (ADS)
Saß, Björn L.; Sauter, Tobias; Seehaus, Thorsten; Braun, Matthias H.
2017-04-01
Observed melting of glaciers and ice caps in the polar regions contribute to the ongoing global sea level rise (SLR). A rising sea level and its consequences are one of the major challenges for coastal societies in the next decades to centuries. Gaining knowledge about the main drivers of SLR and bringing it together is one recent key-challenge for environmental science. The high arctic Svalbard archipelago faced a strong climatic change in the last decades, associated with a change in the cryosphere. Vestfonna, a major Arctic ice cap in the north east of Svalbard, harbors land and marine terminating glaciers, which expose a variability of behavior. We use high resolution remote sensing data from space-borne radar (TanDEM-X, TerraSAR-X, Sentinel-1a), acquired between 2009 and 2015, to estimate glacier velocity and high accurate surface elevation changes. For DEM registration we use space-borne laser altimetry (ICESat) and an existing in-situ data archive (IPY Kinnvika). In order to separate individual glacier basin changes for a detailed mass balance study and for further SLR contribution estimates, we use glacier outlines from the Global Land Ice Measurements from Space (GLIMS) project. Remaining challenges of space-borne observations are the reduction of measurement uncertainties, in the case of Synthetic Aperture Radar most notably signal penetration into the glacier surface. Furthermore, in order to convert volume to mass change one has to use the density of the changed mass (conversion factor) and one has to account for the mass conservation processes in the firn package (firn compaction). Both, the conversion factor and the firn compaction are not (yet) measurable for extensive ice bodies. They have to be modelled by coupling point measurements and regional gridded climate data. Results indicate a slight interior thickening contrasted with wide spread thinning in the ablation zone of the marine terminating outlets. While one glacier system draining to the
Sona Psarska; Edward A. Nater; Randy Kolka
2016-01-01
Invasive earthworms perturb natural forest ecosystems that initially developed without them, mainly by consuming the forest floor (an organic rich surficial soil horizon) and by mixing the upper parts of the soil. The fate of mercury (Hg) formerly contained in the forest floor is largely unknown. We used two mass balance approaches (simple mass balance and geochemical...
Geodetic mass balance measurements on debris and clean-ice tropical glaciers in Ecuador
NASA Astrophysics Data System (ADS)
La Frenierre, J.; Decker, C. R.; Jordan, E.; Wigmore, O.; Hodge, B. E.; Niederriter, C.; Michels, A.
2017-12-01
Glaciers are recognized as highly sensitive indicators of climate change in high altitude, low latitude environments. In the tropical Andes, various analyses of glacier surface area change have helped illuminate the manifestation of climate change in this region, however, information about actual glacier mass balance behavior is much more limited given the relatively small glaciers, difficult access, poor weather, and/or limited local resources common here. Several new technologies, including aerial and terrestrial LIDAR and structure-from-motion photogrammetry using small unmanned aerial vehicles (UAVs), make mass balance measurements using geodetic approaches increasingly feasible in remote mountain locations, which can both further our understanding of changing climatic conditions, and improve our ability to evaluate the downstream hydrologic impacts of ice loss. At Volcán Chimborazo, Ecuador, these new technologies, combined with a unique, 5-meter resolution digital elevation model derived from 1997 aerial imagery, make possible an analysis of the magnitude and spatial patterns of mass balance behavior over the past two decades. Here, we evaluate ice loss between 1997 and 2017 at the tongues of two adjacent glaciers, one debris-covered and detached from its accumulation area (Reschreiter Glacier), and one debris-free and intact (Hans Meyer Glacier). Additionally, we incorporate data from 2012 and 2013 terrestrial LIDAR surveys to evaluate the behavior of the Reschreiter at a finer temporal resolution. We find that on the Hans Meyer, the mean surface deflation rate since 1997 at the present-day tongue has been nearly 3 m yr-1, while on the lower-elevation Reschreiter, the mean deflation rate has been approximately 1 m yr-1. However, the processes by which debris-covered ice becomes exposed results in highly heterogeneous patterns of ice loss, with some areas experiencing surface deflation rates approaching 15 m yr-1 when energy absorption is unimpeded.
NASA Astrophysics Data System (ADS)
Falk, Ulrike; Lopez, Damian; Silva-Busso, Adrian
2017-04-01
The South Shetland Islands are located at the northern tip of the Antarctic Peninsula which is among the fastest warming regions on Earth. Surface air temperature increases (ca. 3 K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K/100 m), and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns especially during winter glacial mass accumulation periods. The increased mesocyclonic activity during the winter time in the study area results in intensified advection of warm, moist air with high temperatures and rain, and leads to melt conditions on the ice cap, fixating surface air temperatures to the melting point. The impact on winter accumulation results in even more negative mass balance estimates. Six years of glaciological measurements on mass balance stake transects are used with a glacier melt model to assess changes in melt water input to the coastal waters, glacier surface mass balance and the equilibrium line altitude. The average equilibrium line altitude (ELA) calculated from own glaciological observations for KGI over the time period 2010 - 2015 amounts to ELA=330±100 m. Published studies suggest rather stable condition slightly negative glacier mass balance until the mid 80's with an ELA of approx. 150 m. The calculated accumulation area ratio suggests rather dramatic changes in extension of the inland ice cap for the South Shetland Islands until an equilibrium with concurrent climate conditions is reached.
NASA Astrophysics Data System (ADS)
Mohd, S.; AL, R.
2017-12-01
Understanding mass balance and volumetric change of glaciers are extremely important in areas where the majority of the population depends on cryospheric sources for the livelihood. Ladakh is one of the coldest and the aridest region of India. The majority of the population live in mountain pockets where the only source of water is snow and glacier melt for agriculture and domestic use. Stok village catchment (52 km2) has seven very small glaciers with an area ranging between 0.2-1.05 km2 at an elevation above 5300m a.s.l (GSI 2009). These glaciers contribute to a stream feeding Stok village of 274 ( 1469 individuals) households and a portion of Chuchot village before joining the Indus River. Ironically very limited studies have been carried out so far in this region, making it even more urgent to monitor the health of the glaciers in this region. With the changing climate, booming of the tourism industry and scarcity of water resources during the spring season, there is a shift in the livelihood of the region towards other option leading to a negative impact on the environment and over exploitation of natural resources. In this study we present analysis of measured annual mass balances for the period 2015-2017 and reconstruction of annual mass balances since 1969 to 2015 of Stok glacier located on the north eastern slope of Zanskar range in Ladakh region of western Himalayas. Direct glaciological methods were used to obtain annual mass balance for 2015-2017 and for reconstruction of annual mass balances, Classical Temperature Index model were used with the help of meteorological data from Indian Meteorological Department. The data gaps were filled with the help of several modelled datasets viz. HAR (High Asia Reanalysis), REMO, and Climate Research Unit (CRU) TS2.1 dataset. We also present catchment wide change in volume of the glaciers since 1969 to 2015. Declassified satellite images and Landsat images were used to obtain the change in volume of the glacier with
NASA Astrophysics Data System (ADS)
Robinson, Ian A.
2014-04-01
The time is fast approaching when the SI unit of mass will cease to be based on a single material artefact and will instead be based upon the defined value of a fundamental constant—the Planck constant—h . This change requires that techniques exist both to determine the appropriate value to be assigned to the constant, and to measure mass in terms of the redefined unit. It is important to ensure that these techniques are accurate and reliable to allow full advantage to be taken of the stability and universality provided by the new definition and to guarantee the continuity of the world's mass measurements, which can affect the measurement of many other quantities such as energy and force. Up to now, efforts to provide the basis for such a redefinition of the kilogram were mainly concerned with resolving the discrepancies between individual implementations of the two principal techniques: the x-ray crystal density (XRCD) method [1] and the watt and joule balance methods which are the subject of this special issue. The first three papers report results from the NRC and NIST watt balance groups and the NIM joule balance group. The result from the NRC (formerly the NPL Mk II) watt balance is the first to be reported with a relative standard uncertainty below 2 × 10-8 and the NIST result has a relative standard uncertainty below 5 × 10-8. Both results are shown in figure 1 along with some previous results; the result from the NIM group is not shown on the plot but has a relative uncertainty of 8.9 × 10-6 and is consistent with all the results shown. The Consultative Committee for Mass and Related Quantities (CCM) in its meeting in 2013 produced a resolution [2] which set out the requirements for the number, type and quality of results intended to support the redefinition of the kilogram and required that there should be agreement between them. These results from NRC, NIST and the IAC may be considered to meet these requirements and are likely to be widely debated
2013-01-01
Background Forest residues represent an abundant and sustainable source of biomass which could be used as a biorefinery feedstock. Due to the heterogeneity of forest residues, such as hog fuel and bark, one of the expected challenges is to obtain an accurate material balance of these feedstocks. Current compositional analytical methods have been standardised for more homogenous feedstocks such as white wood and agricultural residues. The described work assessed the accuracy of existing and modified methods on a variety of forest residues both before and after a typical pretreatment process. Results When “traditional” pulp and paper methods were used, the total amount of material that could be quantified in each of the six softwood-derived residues ranged from 88% to 96%. It was apparent that the extractives present in the substrate were most influential in limiting the accuracy of a more representative material balance. This was particularly evident when trying to determine the lignin content, due to the incomplete removal of the extractives, even after a two stage water-ethanol extraction. Residual extractives likely precipitated with the acid insoluble lignin during analysis, contributing to an overestimation of the lignin content. Despite the minor dissolution of hemicellulosic sugars, extraction with mild alkali removed most of the extractives from the bark and improved the raw material mass closure to 95% in comparison to the 88% value obtained after water-ethanol extraction. After pretreatment, the extent of extractive removal and their reaction/precipitation with lignin was heavily dependent on the pretreatment conditions used. The selective removal of extractives and their quantification after a pretreatment proved to be even more challenging. Regardless of the amount of extractives that were originally present, the analytical methods could be refined to provide reproducible quantification of the carbohydrates present in both the starting material and
Wood, Jessica L; Steiner, Robert R
2011-06-01
Forensic analysis of pharmaceutical preparations requires a comparative analysis with a standard of the suspected drug in order to identify the active ingredient. Purchasing analytical standards can be expensive or unattainable from the drug manufacturers. Direct Analysis in Real Time (DART™) is a novel, ambient ionization technique, typically coupled with a JEOL AccuTOF™ (accurate mass) mass spectrometer. While a fast and easy technique to perform, a drawback of using DART™ is the lack of component separation of mixtures prior to ionization. Various in-house pharmaceutical preparations were purified using thin-layer chromatography (TLC) and mass spectra were subsequently obtained using the AccuTOF™- DART™ technique. Utilizing TLC prior to sample introduction provides a simple, low-cost solution to acquiring mass spectra of the purified preparation. Each spectrum was compared against an in-house molecular formula list to confirm the accurate mass elemental compositions. Spectra of purified ingredients of known pharmaceuticals were added to an in-house library for use as comparators for casework samples. Resolving isomers from one another can be accomplished using collision-induced dissociation after ionization. Challenges arose when the pharmaceutical preparation required an optimized TLC solvent to achieve proper separation and purity of the standard. Purified spectra were obtained for 91 preparations and included in an in-house drug standard library. Primary standards would only need to be purchased when pharmaceutical preparations not previously encountered are submitted for comparative analysis. TLC prior to DART™ analysis demonstrates a time efficient and cost saving technique for the forensic drug analysis community. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.
Radar Interferometry Studies of the Mass Balance of Polar Ice Sheets
NASA Technical Reports Server (NTRS)
Rignot, Eric (Editor)
1999-01-01
The objectives of this work are to determine the current state of mass balance of the Greenland and Antarctic Ice Sheets. Our approach combines different techniques, which include satellite synthetic-aperture radar interferometry (InSAR), radar and laser altimetry, radar ice sounding, and finite-element modeling. In Greenland, we found that 3.5 times more ice flows out of the northern part of the Greenland Ice Sheet than previously accounted for. The discrepancy between current and past estimates is explained by extensive basal melting of the glacier floating sections in the proximity of the grounding line where the glacier detaches from its bed and becomes afloat in the ocean. The inferred basal melt rates are very large, which means that the glaciers are very sensitive to changes in ocean conditions. Currently, it appears that the northern Greenland glaciers discharge more ice than is being accumulated in the deep interior, and hence are thinning. Studies of temporal changes in grounding line position using InSAR confirm the state of retreat of northern glaciers and suggest that thinning is concentrated at the lower elevations. Ongoing work along the coast of East Greenland reveals an even larger mass deficit for eastern Greenland glaciers, with thinning affecting the deep interior of the ice sheet. In Antarctica, we found that glaciers flowing into a large ice shelf system, such as the Ronne Ice Shelf in the Weddell Sea, exhibit an ice discharge in remarkable agreement with mass accumulation in the interior, and the glacier grounding line positions do not migrate with time. Glaciers flowing rapidly into the Amudsen Sea, unrestrained by a major ice shelf, are in contrast discharging more ice than required to maintain a state of mass balance and are thinning quite rapidly near the coast. The grounding line of Pine Island glacier (see diagram) retreated 5 km in 4 years, which corresponds to a glacier thinning rate of 3.5 m/yr. Mass imbalance is even more negative
A Mass Balance-Based Semiparametric Approach to Evaluate Neonatal Erythropoiesis.
Kuruvilla, Denison J; Widness, John A; Nalbant, Demet; Schmidt, Robert L; Mock, Donald M; Veng-Pedersen, Peter
2016-01-01
Postnatal hemoglobin (Hb) production in anemic preterm infants is determined by several factors including the endogenous erythropoietin levels, allogeneic RBC transfusions administered to treat anemia, and developmental age. As a result, their postnatal Hb production rate can vary considerably. This work introduces a novel Hb mass balance-based semiparametric approach that utilizes infant blood concentrations of Hb from the first 30 postnatal days to estimate the amount of Hb produced and the erythropoiesis rate in newborn infants. The proposed method has the advantage of not relying on specific structural pharmacodynamic model assumptions to describe the Hb production, but instead utilizes simple mass balance principles and nonparametric regression analysis. The developed method was applied to the Hb data from 79 critically ill anemic very low birth weight preterm infants to evaluate the dynamic changes in erythropoiesis during the first month of life and to determine the inter-subject variability in Hb production. The estimated mean (±SD) cumulative amount of Hb produced by the infants over the first month of life was 6.6 ± 3.4 g (mean body weight, 0.768 kg), and the mean estimated body weight-scaled Hb production rate over the same period was 0.23 ± 0.12 g/day/kg. A significant positive correlation was observed between infant gestational age and the mean body weight-scaled Hb production rate over the first month of life (P < 0.05). We conclude that the proposed mathematical approach and its implementation provide a flexible framework to evaluate postnatal erythropoiesis in newborn infants.
Curtis, Matthew E; Jones, Patrick R; Sparkman, O David; Cody, Robert B
2009-11-01
Based on the concern about the presence of sulfur materials being in drywall (wallboard), a quick and reliable test to confirm the presence or absence of these materials using direct analysis in real time (DART) mass spectrometry in conjunction with an accurate-mass time-of-flight (TOF) mass spectrometer has been developed and is described here.
Nitrate Removal in Two Relict Oxbow Urban Wetlands: A 15N Mass-balance Approach
A 15N-tracer method was used to quantify nitrogen (N) removal processes in two relict oxbow wetlands located adjacent to the Minebank Run restored stream reach in Baltimore County (Maryland, USA) during summer 2009 and early spring 2010. A mass-balance approach was used to determ...
Mass, Energy, Entropy and Exergy Rate Balance in a Ranque-Hilsh Vortex Tube
ERIC Educational Resources Information Center
Carrascal Lecumberri, Edorta; Sala Lizarraga, José María
2013-01-01
The objective of this paper is to present a laboratory program designed for the Thermodynamics course offered in the Department of Thermal Engineering at the University of the Basque Country. With reference to one of the examples given in the textbook by Moran, Shapiro, Boettner and Bailey (2012), the balances of mass, energy, entropy and exergy…
Leak detection by mass balance effective for Norman Wells line
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liou, J.C.P.
Mass-balance calculations for leak detection have been shown as effective as a leading software system, in a comparison based on a major Canadian crude-oil pipeline. The calculations and NovaCorp`s Leakstop software each detected 4% (approximately) or greater leaks on Interprovincial Pipe Line (IPL) Inc.`s Norman Wells pipeline. Insufficient data exist to assess performances of the two methods for leaks smaller than 4%. Pipeline leak detection using such software-based systems are common. Their effectiveness is measured by how small and how quickly a leak can be detected. Algorithms used and measurement uncertainties determine leak detectability.
A mass-balanced definition of corrected retention volume in gas chromatography.
Kurganov, A
2007-05-25
The mass balance equation of a chromatographic system using a compressible moving phase has been compiled for mass flow of the mobile phase instead of traditional volumetric flow allowing solution of the equation in an analytical form. The relation obtained correlates retention volume measured under ambient conditions with the partition coefficient of the solute. Compared to the relation in the ideal chromatographic system the equation derived contains an additional correction term accounting for the compressibility of the moving phase. When the retention volume is measured under the mean column pressure and column temperature the correction term is reduced to unit and the relation is simplified to those known for the ideal system. This volume according to International Union of Pure and Applied Chemistry (IUPAC) is called the corrected retention volume.
Davies, Stephen R; Jones, Kai; Goldys, Anna; Alamgir, Mahuiddin; Chan, Benjamin K H; Elgindy, Cecile; Mitchell, Peter S R; Tarrant, Gregory J; Krishnaswami, Maya R; Luo, Yawen; Moawad, Michael; Lawes, Douglas; Hook, James M
2015-04-01
Quantitative NMR spectroscopy (qNMR) has been examined for purity assessment using a range of organic calibration standards of varying structural complexities, certified using the traditional mass balance approach. Demonstrated equivalence between the two independent purity values confirmed the accuracy of qNMR and highlighted the benefit of using both methods in tandem to minimise the potential for hidden bias, thereby conferring greater confidence in the overall purity assessment. A comprehensive approach to purity assessment is detailed, utilising, where appropriate, multiple peaks in the qNMR spectrum, chosen on the basis of scientific reason and statistical analysis. Two examples are presented in which differences between the purity assignment by qNMR and mass balance are addressed in different ways depending on the requirement of the end user, affording fit-for-purpose calibration standards in a cost-effective manner.
NASA Astrophysics Data System (ADS)
Schlegel, N.-J.; Larour, E.; Seroussi, H.; Morlighem, M.; Box, J. E.
2013-06-01
The behavior of the Greenland Ice Sheet, which is considered a major contributor to sea level changes, is best understood on century and longer time scales. However, on decadal time scales, its response is less predictable due to the difficulty of modeling surface climate, as well as incomplete understanding of the dynamic processes responsible for ice flow. Therefore, it is imperative to understand how modeling advancements, such as increased spatial resolution or more comprehensive ice flow equations, might improve projections of ice sheet response to climatic trends. Here we examine how a finely resolved climate forcing influences a high-resolution ice stream model that considers longitudinal stresses. We simulate ice flow using a two-dimensional Shelfy-Stream Approximation implemented within the Ice Sheet System Model (ISSM) and use uncertainty quantification tools embedded within the model to calculate the sensitivity of ice flow within the Northeast Greenland Ice Stream to errors in surface mass balance (SMB) forcing. Our results suggest that the model tends to smooth ice velocities even when forced with extreme errors in SMB. Indeed, errors propagate linearly through the model, resulting in discharge uncertainty of 16% or 1.9 Gt/yr. We find that mass flux is most sensitive to local errors but is also affected by errors hundreds of kilometers away; thus, an accurate SMB map of the entire basin is critical for realistic simulation. Furthermore, sensitivity analyses indicate that SMB forcing needs to be provided at a resolution of at least 40 km.
Surface Energy and Mass Balance Model for Greenland Ice Sheet and Future Projections
NASA Astrophysics Data System (ADS)
Liu, Xiaojian
The Greenland Ice Sheet contains nearly 3 million cubic kilometers of glacial ice. If the entire ice sheet completely melted, sea level would raise by nearly 7 meters. There is thus considerable interest in monitoring the mass balance of the Greenland Ice Sheet. Each year, the ice sheet gains ice from snowfall and loses ice through iceberg calving and surface melting. In this thesis, we develop, validate and apply a physics based numerical model to estimate current and future surface mass balance of the Greenland Ice Sheet. The numerical model consists of a coupled surface energy balance and englacial model that is simple enough that it can be used for long time scale model runs, but unlike previous empirical parameterizations, has a physical basis. The surface energy balance model predicts ice sheet surface temperature and melt production. The englacial model predicts the evolution of temperature and meltwater within the ice sheet. These two models can be combined with estimates of precipitation (snowfall) to estimate the mass balance over the Greenland Ice Sheet. We first compare model performance with in-situ observations to demonstrate that the model works well. We next evaluate how predictions are degraded when we statistically downscale global climate data. We find that a simple, nearest neighbor interpolation scheme with a lapse rate correction is able to adequately reproduce melt patterns on the Greenland Ice Sheet. These results are comparable to those obtained using empirical Positive Degree Day (PDD) methods. Having validated the model, we next drove the ice sheet model using the suite of atmospheric model runs available through the CMIP5 atmospheric model inter-comparison, which in turn built upon the RCP 8.5 (business as usual) scenarios. From this exercise we predict how much surface melt production will increase in the coming century. This results in 4-10 cm sea level equivalent, depending on the CMIP5 models. Finally, we try to bound melt water
NASA Astrophysics Data System (ADS)
Rodehacke, C. B.; Mottram, R.; Boberg, F.
2017-12-01
The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we various boundary conditions, ranging from ERA-Interim reanalysis data via global climate model high resolution (5km) output from the regional climate model HIRHAM5, to determine the surface mass balance of the Devon ice cap. These SMB estimates are used to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.
Mass balance of Mars' residual south polar cap from CTX images and other data
NASA Astrophysics Data System (ADS)
Thomas, P. C.; Calvin, W.; Cantor, B.; Haberle, R.; James, P. B.; Lee, S. W.
2016-04-01
Erosion of pits in the residual south polar cap (RSPC) of Mars concurrent with deposition and fluctuating cap boundaries raises questions about the mass balance and long term stability of the cap. Determining a mass balance by measurement of a net gain or loss of atmospheric CO2 by direct pressure measurements (Haberle, R.M. et al. [2014]. Secular climate change on Mars: An update using one Mars year of MSL pressure data. American Geophysical Union (Fall). Abstract 3947), although perhaps the most direct method, has so far given ambiguous results. Estimating volume changes from imaging data faces challenges, and has previously been attempted only in isolated areas of the cap. In this study we use 6 m/pixel Context Imager (CTX) data from Mars year 31 to map all the morphologic units of the RSPC, expand the measurement record of pit erosion rates, and use high resolution images to place limits on vertical changes in the surface of the residual cap. We find the mass balance in Mars years 9-31 to be -6 to +4 km3/♂y, or roughly -0.039% to +0.026% of the mean atmospheric CO2 mass/♂y. The indeterminate sign results chiefly from uncertainty in the amounts of deposition or erosion on the upper surfaces of deposits (as opposed to scarp retreat). Erosion and net deposition in this period appear to be controlled by summertime planetary scale dust events, the largest occurring in MY 9, another, smaller one in MY 28. The rates of erosion and the deposition observed since MY 9 appear to be consistent with the types of deposits and erosional behavior found in most of the residual cap. However, small areas (<10%) of the cap are distinguished by their greater thickness, polygonal troughs, and embayed contacts with thinner units. These deposits may require extended periods (>100 ♂y) of depositional and/or erosional conditions different from those occurring in the period since MY 9, although these environmental differences could be subtle.
Modeling associated with the Lake Michigan Mass Balance Project (LMMBP) is being conducted using WASP-type water quality models to gain a better understanding of the ecosystem transport and fate of polychlorinated biphenyls (PCBs), atrazine, mercury, and trans-nonachlor in Lake M...
NASA Astrophysics Data System (ADS)
Van Pelt, Ward; Pohjola, Veijo; Reijmer, Carleen
2016-11-01
Glacier surface melt and runoff depend strongly on seasonal and perennial snow (firn) conditions. Not only does the presence of snow and firn directly affect melt rates by reflecting solar radiation, it may also act as a buffer against mass loss by storing melt water in refrozen or liquid form. In Svalbard, ongoing and projected amplified climate change with respect to the global mean change has severe implications for the state of snow and firn and its impact on glacier mass loss. Model experiments with a coupled surface energy balance - firn model were done to investigate the surface mass balance and the changing role of snow and firn conditions for an idealized Svalbard glacier. A climate forcing for the past, present and future (1984-2104) is constructed, based on observational data from Svalbard Airport and a seasonally dependent projection scenario. Results illustrate ongoing and future firn degradation in response to an elevational retreat of the equilibrium line altitude (ELA) of 31 m decade-1. The temperate firn zone is found to retreat and expand, while cold ice in the ablation zone warms considerably. In response to pronounced winter warming and an associated increase in winter rainfall, the current prevalence of refreezing during the melt season gradually shifts to the winter season in a future climate. Sensitivity tests reveal that in a present and future climate the density and thermodynamic structure of Svalbard glaciers are heavily influenced by refreezing. Refreezing acts as a net buffer against mass loss. However, the net mass balance change after refreezing is substantially smaller than the amount of refreezing itself, which can be ascribed to melt-enhancing effects after refreezing, which partly offset the primary mass-retaining effect of refreezing.
Nitrogen isotope and mass balance approach in the Elbe Estuary
NASA Astrophysics Data System (ADS)
Sanders, Tina; Wankel, Scott D.; Dähnke, Kirstin
2017-04-01
The supply of bioavailable nitrogen is crucial to primary production in the world's oceans. Especially in estuaries, which act as a nutrient filter for coastal waters, microbial nitrogen turnover and removal has a particular significance. Nitrification as well as other nitrogen-based processes changes the natural abundance of the stable isotope, which can be used as proxies for sources and sinks as well as for process identification. The eutrophic Elbe estuary in northern Germany is loaded with fertilizer-derived nitrogen, but management efforts have started to reduce this load effectively. However, an internal nitrate source in turn gained in importance and the estuary changed from a sink to a source of dissolved inorganic nitrogen: Nitrification is responsible for significant estuarine nutrient regeneration, especially in the Hamburg Port. In our study, we aimed to quantify sources and sinks of nitrogen based on a mass and stable isotope budget in the Elbe estuary. A model was developed reproduce internal N-cycling and associated isotope changes. For that approach we measured dissolved inorganic nitrogen (DIN), particulate nitrogen and their stable isotopes in a case study in July 2013. We found an almost closed mass balance of nitrogen, with only low lost or gains which we attribute to sediment resuspension. The isotope values of different DIN components and the model approach both support a high fractionation of up to -25‰ during nitrification. However, the nitrogen balance and nitrogen stable isotopes suggest that most important processes are remineralization of organic matter to ammonium and further on the oxidation to nitrate. Denitrification and nitrate assimilation play a subordinate role in the Elbe Estuary.
Quantifying Uncertainty in the Greenland Surface Mass Balance Elevation Feedback
NASA Astrophysics Data System (ADS)
Edwards, T.
2015-12-01
As the shape of the Greenland ice sheet responds to changes in surface mass balance (SMB) and dynamics, it affects the surface mass balance through the atmospheric lapse rate and by altering atmospheric circulation patterns. Positive degree day models include simplified representations of this feedback, but it is difficult to simulate with state-of-the-art models because it requires coupling of regional climate models with dynamical ice sheet models, which is technically challenging. This difficulty, along with the high computational expense of regional climate models, also drastically limits opportunities for exploring the impact of modelling uncertainties on sea level projections. We present a parameterisation of the SMB-elevation feedback in the MAR regional climate model that provides a far easier and quicker estimate than atmosphere-ice sheet model coupling, which can be used with any ice sheet model. This allows us to use ensembles of different parameter values and ice sheet models to assess the effect of uncertainty in the feedback and ice sheet model structure on future sea level projections. We take a Bayesian approach to uncertainty in the feedback parameterisation, scoring the results from multiple possible "SMB lapse rates" according to how well they reproduce a MAR simulation with altered ice sheet topography. We test the impact of the resulting parameterisation on sea level projections using five ice sheet models forced by MAR (in turned forced by two different global climate models) under the emissions scenario A1B. The estimated additional sea level contribution due to the SMB-elevation feedback is 4.3% at 2100 (95% credibility interval 1.8-6.9%), and 9.6% at 2200 (3.6-16.0%).
Balance Mass Flux and Velocity Across the Equilibrium Line in Ice Drainage Systems of Greenland
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Giovinetto, Mario B.; Koblinsky, Chester J. (Technical Monitor)
2001-01-01
Estimates of balance mass flux and the depth-averaged ice velocity through the cross-section aligned with the equilibrium line are produced for each of six drainage systems in Greenland. (The equilibrium line, which lies at approximately 1200 m elevation on the ice sheet, is the boundary between the area of net snow accumulation at higher elevations and the areas of net melting at lower elevations around the ice sheet.) Ice drainage divides and six major drainage systems are delineated using surface topography from ERS (European Remote Sensing) radar altimeter data. The net accumulation rate in the accumulation zone bounded by the equilibrium line is 399 Gt/yr and net ablation rate in the remaining area is 231 Gt/yr. (1 GigaTon of ice is 1090 kM(exp 3). The mean balance mass flux and depth-averaged ice velocity at the cross-section aligned with the modeled equilibrium line are 0.1011 Gt kM(exp -2)/yr and 0.111 km/yr, respectively, with little variation in these values from system to system. The ratio of the ice mass above the equilibrium line to the rate of mass output implies an effective exchange time of approximately 6000 years for total mass exchange. The range of exchange times, from a low of 3 ka in the SE drainage system to 14 ka in the NE, suggests a rank as to which regions of the ice sheet may respond more rapidly to climate fluctuations.
NASA Astrophysics Data System (ADS)
Bhushan, S.; Shean, D. E.; Haritashya, U. K.; Arendt, A. A.; Syed, T. H.; Setiawan, L.
2017-12-01
Glacial lake outburst floods can impact downstream communities due to the sudden outflux of huge quantities of stored water. In this study, we develop a hazard assessment of the moraine dammed glacial lakes in Sikkim Himalayas by analyzing the morphometry of proglacial features, and the surface velocity and mass balance of glaciers. We generated high-resolution digital elevation models (DEMs) using the open-source NASA Ames Stereo Pipeline (ASP) and use other open-source tools to calculate surface velocity and patterns of glacier downwasting over time. Geodetic glacier mass balance is obtained for three periods using high-resolution WorldView/GeoEye stereo DEMs (8 m posting, 2014-2016), Cartosat-1 stereo DEMs (10 m, 2006-2008) and SRTM (30 m, 2000). Initial results reveal a region-wide mass balance of -0.31±0.13 m w.eq.a-1 for the 2007-2015 period, with some debris covered glaciers showing a very low mass loss rate. Additionally, 12 annual glacier velocity fields spanning from 1991 to 2017.derived from Landsat imagery are used to explore the relationship between glacier dynamics and changes in proglacial lakes. Multi-temporal glacial lake mapping is conducted using Landsat and Cartosat imagery. Avalanche and rockfall modeling are combined with morphometric analysis of the proglacial lake area to assess the likelihood of glacial lake dam failure. The above parameters are integrated into a decision tree approach enabling categorization of moraine-dammed lakes according to their potential for outburst events.
Recycled Uranium Mass Balance Project Y-12 National Security Complex Site Report
DOE Office of Scientific and Technical Information (OSTI.GOV)
NONE
2000-12-01
This report has been prepared to summarize the findings of the Y-12 National Security Complex (Y-12 Complex) Mass Balance Project and to support preparation of associated U. S. Department of Energy (DOE) site reports. The project was conducted in support of DOE efforts to assess the potential for health and environmental issues resulting from the presence of transuranic (TRU) elements and fission products in recycled uranium (RU) processed by DOE and its predecessor agencies. The United States government used uranium in fission reactors to produce plutonium and tritium for nuclear weapons production. Because uranium was considered scarce relative to demandmore » when these operations began almost 50 years ago, the spent fuel from U.S. fission reactors was processed to recover uranium for recycling. The estimated mass balance for highly enriched RU, which is of most concern for worker exposure and is the primary focus of this project, is summarized in a table. A discrepancy in the mass balance between receipts and shipments (plus inventory and waste) reflects an inability to precisely distinguish between RU and non-RU shipments and receipts involving the Y-12 Complex and Savannah River. Shipments of fresh fuel (non-RU) and sweetener (also non-RU) were made from the Y-12 Complex to Savannah River along with RU shipments. The only way to distinguish between these RU and non-RU streams using available records is by enrichment level. Shipments of {le}90% enrichment were assumed to be RU. Shipments of >90% enrichment were assumed to be non-RU fresh fuel or sweetener. This methodology using enrichment level to distinguish between RU and non-RU results in good estimates of RU flows that are reasonably consistent with Savannah River estimates. Although this is the best available means of distinguishing RU streams, this method does leave a difference of approximately 17.3 MTU between receipts and shipments. Slightly depleted RU streams received by the Y-12 Complex from
NASA Astrophysics Data System (ADS)
Smith, S.; Ullman, D. J.; He, F.; Carlson, A. E.; Marzeion, B.; Maussion, F.
2017-12-01
Understanding the behavior of the world's glaciers during previous interglaciations is key to interpreting the sensitivity and behavior of the cryosphere under scenarios of future anthropogenic warming. Previous studies of the Last Interglaciation (LIG, 130 ka to 116 ka) indicate elevated global temperatures and higher sea levels than the Holocene, but most assessments of the impact on the cryosphere have focused on the mass balance and volume change of polar ice sheets. In assessing sea-level sources, most studies assume complete deglacation of global glaciers, but this has yet to be tested. In addition, the significant changes in orbital forcing during the LIG and the associated impacts on climate seasonality and variability may have led to unique glacier evolution.Here, we explore the effect of LIG climate on the global glacier budget. We employ the Open Global Glacier Model (OGGM), forced by simulated LIG equilibrium climate anomalies (127 ka) from the Community Climate System Model Version 3 (CCSM3). OGGM is a glacier mass balance and dynamics model, specifically designed to reconstruct global glacier volume change. Our simulations have been conducted in an equilibrium state to determine the effect of the prolonged climate forcing of the LIG. Due to unknown flow characteristics of glaciers during the LIG, we explore the parametric uncertainty in the mass balance and flow sensitivity parameters. As a point of comparison, we also conduct a series of simulations using forcing anomalies from the CCSM3 mid-Holocene (6 ka) experiment. Results from both experiments show that glacier mass balance is highly sensitive to these sensitivity parameters, pointing at the need for glacier margin calibration for OGGM in paleoclimate applications.
System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator
2006-08-01
commanded torque to move away from these singularity points. The introduction of this error may not degrade the performance for large slew angle ...trajectory has been generated and quaternion feedback control has been implemented for reference trajectory tracking. The testbed was reasonably well...System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator Jae-Jun Kim∗ and Brij N. Agrawal † Department of
Implications of sodium mass balance for interpreting the calcium cycle of a forested ecosystem
Scott W. Bailey; Donald C. Buso; Gene E. Likens
2003-01-01
Disturbance of forest ecosystems, such as that caused by harvesting or acid deposition, is thought to alter the ability of the ecosystem to retain nutrients. Although many watershed studies have suggested depletion of available calcium (Ca) pools, interpretation of ecosystem Ca mass balance has been limited by the difficulty in obtaining mineral weathering flux...
A new statistical model to find bedrock, a prequel to geochemical mass balance
NASA Astrophysics Data System (ADS)
Fisher, B.; Rendahl, A. K.; Aufdenkampe, A. K.; Yoo, K.
2016-12-01
We present a new statistical model to assess weathering trends in deep weathering profiles. The Weathering Trends (WT) model is presented as an extension of the geochemical mass balance model (Brimhall & Dietrich, 1987), and is available as an open-source R library on GitHub (https://github.com/AaronRendahl/WeatheringTrends). WT uses element concentration data to determine the depth to fresh bedrock by assessing the maximum extent of weathering for all elements and the model applies confidence intervals on the depth to bedrock. WT models near-surface features and the shape of the weathering profile using a log transformation of data to capture the magnitude of changes that are relevant to geochemical kinetics and thermodynamics. The WT model offers a new, enhanced opportunity to characterize and understand biogeochemical weathering in heterogeneous rock types. We apply the model to two 21-meter drill cores in the Laurels Schist bedrock in the Christina River Basin Critical Zone Observatory in the Pennsylvania Piedmont. The Laurels Schist had inconclusive weathering indicators prior to development and application of WT model. The model differentiated between rock variability and weathering to delineate the maximum extent of weathering at 12.3 (CI 95% [9.2, 21.3]) meters in Ridge Well 1 and 7.2 (CI 95% [4.3, 13.0]) meters in Interfluve Well 2. The modeled extent to weathering is decoupled from the water table at the ridge, but coincides with the water table at the interfluve. These depths were applied as the parent material for the geochemical mass balance for the Laurels Schist. We test statistical approaches to assess the variability and correlation of immobile elements to facilitate the selection of the best immobile element for use in both models. We apply the model to other published data where the geochemical mass balance was applied, to demonstrate how the WT model provides additional information about weathering depth and weathering trends.
Schulte, Marcel; Jochmann, Maik A; Gehrke, Tobias; Thom, Andrea; Ricken, Tim; Denecke, Martin; Schmidt, Torsten C
2017-11-01
Biological methane oxidation may be regarded as a method of aftercare treatment for landfills to reduce climate relevant methane emissions. It is of social and economic interest to estimate the behavior of bacterial methane oxidation in aged landfill covers due to an adequate long-term treatment of the gas emissions. Different approaches assessing methane oxidation in laboratory column studies have been investigated by other authors recently. However, this work represents the first study in which three independent approaches, ((i) mass balance, (ii) stable isotope analysis, and (iii) stoichiometric balance of product (CO 2 ) and reactant (CH 4 ) by CO 2 /CH 4 -ratio) have been compared for the estimation of the biodegradation by a robust statistical validation on a rectangular, wide soil column. Additionally, an evaluation by thermal imaging as a potential technique for the localization of the active zone of bacterial methane oxidation has been addressed in connection with stable isotope analysis and CO 2 /CH 4 -ratios. Although landfills can be considered as open systems the results for stable isotope analysis based on a closed system correlated better with the mass balance than calculations based on an open system. CO 2 /CH 4 -ratios were also in good agreement with mass balance. In general, highest values for biodegradation were determined from mass balance, followed by CO 2 /CH 4 -ratio, and stable isotope analysis. The investigated topsoil proved to be very suitable as a potential cover layer by removing up to 99% of methane for CH 4 loads of 35-65gm -2 d -1 that are typical in the aftercare phase of landfills. Finally, data from stable isotope analysis and the CO 2 /CH 4 -ratios were used to trace microbial activity within the reactor system. It was shown that methane consumption and temperature increase, as a cause of high microbial activity, correlated very well. Copyright © 2017 Elsevier Ltd. All rights reserved.
Energy and mass balance observations on La Mare Glacier (Ortles-Cevedale, European Alps)
NASA Astrophysics Data System (ADS)
Carturan, L.; Cazorzi, F.; Dalla Fontana, G.
2009-04-01
An experimental site was setup in 2005 on the ablation area of La Mare Glacier, at 2990 m a.s.l., to study the energy and mass balance exchanges between the glacier surface and the atmosphere and to investigate the climatic sensitivity of this particular glacier. An Automatic Weather Station was operated, in the framework of a monitoring network which has been implemented in the Upper Val de La Mare experimental watershed (Trentino, Italy). This basin was selected for a study of climate change effects on cryosphere and hydrology at high-altitude catchments. The 36.2 km2 wide basin has an average altitude of 2906 m a.s.l. and at present the 25% of its surface is glacierized; the annual runoff regime is dominated by snow and ice melt. Direct mass balance measurements have been performed since 1967 on Careser glacier (2.83 km2) and since 2003 on La Mare glacier (3.97 km2). The AWS is mounted on a tripod which stands freely on the glacier surface and is solar-powered. The variables measured are: air temperature and relative humidity, wind speed and direction, shortwave and longwave incoming and outgoing radiation, precipitation and surface height. All the data are sampled at five-minute intervals as average values, with the exception of surface height which is sampled at hourly intervals, as instantaneous values. The collected data were used to calculate the point energy and mass balance and to compare the results with similar investigations carried out on glaciers and available in literature. In particular, our attention has been focussed on some processes which regulate the response to climate changes. The relative importance of the energy balance components was examined and a clear predominance of shortwave radiation inputs was found to exist during melt conditions. Given the relevance of the shortwave net balance, the ice albedo temporal variability (values ranging from 0.1 to 0.5) has been investigated and correlated with meteorological variables. Furthermore, a
NASA Astrophysics Data System (ADS)
Wilson, Nat; Straneo, Fiammetta; Heimbach, Patrick
2017-12-01
Ice-shelf-like floating extensions at the termini of Greenland glaciers are undergoing rapid changes with potential implications for the stability of upstream glaciers and the ice sheet as a whole. While submarine melting is recognized as a major contributor to mass loss, the spatial distribution of submarine melting and its contribution to the total mass balance of these floating extensions is incompletely known and understood. Here, we use high-resolution WorldView satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining ice tongues - Nioghalvfjerdsbræ (79 North Glacier, 79N), Ryder Glacier (RG), and Petermann Glacier (PG). Submarine melt rates under the ice tongues vary considerably, exceeding 50 m a-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. We compare the total melt rates to the influx of ice to the ice tongue to assess their contribution to the current mass balance. At Petermann Glacier and Ryder Glacier, we find that the combined submarine and aerial melt approximately balances the ice flux from the grounded ice sheet. At Nioghalvfjerdsbræ the total melt flux (14.2 ± 0.96 km3 a-1 w.e., water equivalent) exceeds the inflow of ice (10.2 ± 0.59 km3 a-1 w.e.), indicating present thinning of the ice tongue.
State of balance of the cryosphere
NASA Technical Reports Server (NTRS)
Van Der Veen, C. J.
1991-01-01
Available observations and mass balance estimates of the cryosphere are summarized. Problems discussed include mountain glaciers, the Greenland ice sheet, the Antarctic ice sheet, conventional glacier measurement techniques, and satellite applications in glacier mass balance studies. It is concluded that the interior part of the Greenland ice sheet is thickening or in near equilibrium. Estimates of the mass balance of the Antarctic ice sheet suggest that it is positive, although the error limits allow for a slightly negative balance.
Wang, Joanna Shaofen; Chiu, Kong-Hwa
2006-03-01
The objective of this work is to track the amount of metal complexes distributed in the extraction cell, collection vial, and tubing used in supercritical fluid extraction (SFE) systems after progressive removal of metal ions in supercritical carbon dioxide (SC-CO2). Sodium diethyldithiocarbamate (NaDDC) and dibutylammonium dibutyldithiocarbamate (DBDC) ligands were used to form complexes with Cd, Cu, Pb, and Zn and CO(2)/5% methanol as a supercritical fluid. The mass balance of metal complexes were obtained before and after extraction, and metals in different locations in the system were flushed out using an organic solvent and nitric acid (HNO3). These results infer that the stability constant (beta) of the metal-ligand complex has a strong correlation with SFE. Because of the composition of the stainless-steel cell, Fe, Cr, and Ni or other trace elements in the cell might interfere with the mass balance of metal complexes in SFE due to an exchange mechanism taking place between the cell and the sample.
A California Nitrogen Mass Balance: Uncertainties and information needs
NASA Astrophysics Data System (ADS)
Liptzin, D.; Dahlgren, R. A.
2011-12-01
The goal of the California Nitrogen (N) Assessment (CNA) is to evaluate the current state of N science, practice, and policy in the state of California. One component is to develop a N mass balance for the state. Because the CNA is an assessment, evaluating the data quality and quantifying uncertainty are also part of the mass balance . We estimate that a total of 1500 Gg of new reactive N is added to California every year. Of this new N, only about half of the N leaves the state while the rest is retained. The main inputs of new reactive N to California are, in order of importance: synthetic N fertilizer, fossil fuel combustion, and biological N fixation. The three largest N outputs from the state are, in order of importance, atmospheric advection, wastewater discharge to the ocean, and riverine discharge to the ocean. Approximately half of the stored N leaches to groundwater, with the other half divided between soils and vegetation, reservoirs, and urban landscapes. These N flows vary not just in magnitude, but also in the uncertainty associated with them. There was no trend in the tonnage of fertilizer sold from 1981-2001, but the 2002-2007 average has remained higher (760 Gg N) than the long-term average (520 Gg N). Bottom up calculations based on crop acreage and fertilization rates are more consistent with the 1980-2001 average suggesting a problem with the sales data. The emission of NOx from fossil fuel burning is one of the most well established flows of N. The production of ammonia and nitrous oxide from fossil fuel combustion is significantly lower than NOx, but there is less evidence to support the emissions inventories. Rates of biological N fixation are speculative with evidence more limited in natural lands than croplands. For most crops it appears that N fixation rates are strongly related to plant production, suggesting that using a single rate across large regions may be inappropriate. In addition, many studies either only measure aboveground N
Method of Calibrating a Force Balance
NASA Technical Reports Server (NTRS)
Parker, Peter A. (Inventor); Rhew, Ray D. (Inventor); Johnson, Thomas H. (Inventor); Landman, Drew (Inventor)
2015-01-01
A calibration system and method utilizes acceleration of a mass to generate a force on the mass. An expected value of the force is calculated based on the magnitude and acceleration of the mass. A fixture is utilized to mount the mass to a force balance, and the force balance is calibrated to provide a reading consistent with the expected force determined for a given acceleration. The acceleration can be varied to provide different expected forces, and the force balance can be calibrated for different applied forces. The acceleration may result from linear acceleration of the mass or rotational movement of the mass.
Glacial changes and glacier mass balance at Gran Campo Nevado, Chile during recent decades
NASA Astrophysics Data System (ADS)
Schneider, C.; Schnirch, M.; Kilian, R.; Acuña, C.; Casassa, G.
2003-04-01
/2001 and 8.5 m in 2001/2002. This is in excellent accordance (+/-4%) with measurements at 12 m-long ablation stakes that have been drilled into the glacier. The DEM and a GIS layer defining glacier boundaries provide the basis for the distributed calculation of glacier mass balance. It was computed from the degree-day-model by applying elevation-corrected temperature and precipitation data to each grid point of the DEM. Furthermore, weather station data from Punta Arenas and Faro Evangelistas since 1905 enables to estimate the mass balance of Glaciar Lengua for almost one century. The derived mass balance record indicates a slightly negative mass balance during most of the 20th century. This in excellent agreement with the result obtained from aerial photography and GIS. The work was conducted as part of the international and interdisciplinary working group “Gran Campo Nevado” and was supported by the German Research Foundation (DFG).
NASA Astrophysics Data System (ADS)
Hong, Pengyu; Sun, Hui; Sha, Long; Pu, Yi; Khatri, Kshitij; Yu, Xiang; Tang, Yang; Lin, Cheng
2017-08-01
A major challenge in glycomics is the characterization of complex glycan structures that are essential for understanding their diverse roles in many biological processes. We present a novel efficient computational approach, named GlycoDeNovo, for accurate elucidation of the glycan topologies from their tandem mass spectra. Given a spectrum, GlycoDeNovo first builds an interpretation-graph specifying how to interpret each peak using preceding interpreted peaks. It then reconstructs the topologies of peaks that contribute to interpreting the precursor ion. We theoretically prove that GlycoDeNovo is highly efficient. A major innovative feature added to GlycoDeNovo is a data-driven IonClassifier which can be used to effectively rank candidate topologies. IonClassifier is automatically learned from experimental spectra of known glycans to distinguish B- and C-type ions from all other ion types. Our results showed that GlycoDeNovo is robust and accurate for topology reconstruction of glycans from their tandem mass spectra. [Figure not available: see fulltext.
2015-01-01
Systematic analysis and interpretation of the large number of tandem mass spectra (MS/MS) obtained in metabolomics experiments is a bottleneck in discovery-driven research. MS/MS mass spectral libraries are small compared to all known small molecule structures and are often not freely available. MS2Analyzer was therefore developed to enable user-defined searches of thousands of spectra for mass spectral features such as neutral losses, m/z differences, and product and precursor ions from MS/MS spectra in MSP/MGF files. The software is freely available at http://fiehnlab.ucdavis.edu/projects/MS2Analyzer/. As the reference query set, 147 literature-reported neutral losses and their corresponding substructures were collected. This set was tested for accuracy of linking neutral loss analysis to substructure annotations using 19 329 accurate mass tandem mass spectra of structurally known compounds from the NIST11 MS/MS library. Validation studies showed that 92.1 ± 6.4% of 13 typical neutral losses such as acetylations, cysteine conjugates, or glycosylations are correct annotating the associated substructures, while the absence of mass spectra features does not necessarily imply the absence of such substructures. Use of this tool has been successfully demonstrated for complex lipids in microalgae. PMID:25263576
DETERMINING ION COMPOSITIONS USING AN ACCURATE MASS, TRIPLE QUADRUPOLE MASS SPECTROMETER
For the past decade, we have used double focusing mass spectrometers to determine
compositions of ions observed in mass spectra produced from compounds introduced by GC
based on measured exact masses of the ions and their +1 and +2 isotopic profiles arising from atoms of ...
Estimation of air-water gas exchange coefficient in a shallow lagoon based on 222Rn mass balance.
Cockenpot, S; Claude, C; Radakovitch, O
2015-05-01
The radon-222 mass balance is now commonly used to quantify water fluxes due to Submarine Groundwater Discharge (SGD) in coastal areas. One of the main loss terms of this mass balance, the radon evasion to the atmosphere, is based on empirical equations. This term is generally estimated using one among the many empirical equations describing the gas transfer velocity as a function of wind speed that have been proposed in the literature. These equations were, however, mainly obtained from areas of deep water and may be less appropriate for shallow areas. Here, we calculate the radon mass balance for a windy shallow coastal lagoon (mean depth of 6m and surface area of 1.55*10(8) m(2)) and use these data to estimate the radon loss to the atmosphere and the corresponding gas transfer velocity. We present new equations, adapted to our shallow water body, to express the gas transfer velocity as a function of wind speed at 10 m height (wind range from 2 to 12.5 m/s). When compared with those from the literature, these equations fit particularly well with the one of Kremer et al. (2003). Finally, we emphasize that some gas transfer exchange may always occur, even for conditions without wind. Copyright © 2015 Elsevier Ltd. All rights reserved.
Improving Surface Mass Balance Over Ice Sheets and Snow Depth on Sea Ice
NASA Technical Reports Server (NTRS)
Koenig, Lora Suzanne; Box, Jason; Kurtz, Nathan
2013-01-01
Surface mass balance (SMB) over ice sheets and snow on sea ice (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists' abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On ice sheets, snow accumulation is the sole mass gain to SMB, and meltwater runoff can be the dominant single loss factor in extremely warm years such as 2012. SOSI affects the growth and melt cycle of the Earth's polar sea ice cover. The summer of 2012 saw the largest satellite-recorded melt area over the Greenland ice sheet and the smallest satellite-recorded Arctic sea ice extent, making this meeting both timely and relevant.
NASA Technical Reports Server (NTRS)
Chakrabarti, Suman; Schmidt, George R.; Thio, Y. C.; Hurst, Chantelle M.
1999-01-01
A preliminary model for spacecraft propulsion performance analysis based on nuclear gain and subsystem mass-power balances are presented in viewgraph form. For very fast missions with straight-line trajectories, it has been shown that mission trip time is proportional to the cube root of alpha. Analysis of spacecraft power systems via a power balance and examination of gain vs. mass-power ratio has shown: 1) A minimum gain is needed to have enough power for thruster and driver operation; and 2) Increases in gain result in decreases in overall mass-power ratio, which in turn leads to greater achievable accelerations. However, subsystem mass-power ratios and efficiencies are crucial: less efficient values for these can partially offset the effect of nuclear gain. Therefore, it is of interest to monitor the progress of gain-limited subsystem technologies and it is also possible that power-limited systems with sufficiently low alpha may be competitive for such ambitious missions. Topics include Space flight requirements; Spacecraft energy gain; Control theory for performance; Mission assumptions; Round trips: Time and distance; Trip times; Vehicle acceleration; and Minimizing trip times.
Gaussian Process Model for Antarctic Surface Mass Balance and Ice Core Site Selection
NASA Astrophysics Data System (ADS)
White, P. A.; Reese, S.; Christensen, W. F.; Rupper, S.
2017-12-01
Surface mass balance (SMB) is an important factor in the estimation of sea level change, and data are collected to estimate models for prediction of SMB on the Antarctic ice sheet. Using Favier et al.'s (2013) quality-controlled aggregate data set of SMB field measurements, a fully Bayesian spatial model is posed to estimate Antarctic SMB and propose new field measurement locations. Utilizing Nearest-Neighbor Gaussian process (NNGP) models, SMB is estimated over the Antarctic ice sheet. An Antarctic SMB map is rendered using this model and is compared with previous estimates. A prediction uncertainty map is created to identify regions of high SMB uncertainty. The model estimates net SMB to be 2173 Gton yr-1 with 95% credible interval (2021,2331) Gton yr-1. On average, these results suggest lower Antarctic SMB and higher uncertainty than previously purported [Vaughan et al. (1999); Van de Berg et al. (2006); Arthern, Winebrenner and Vaughan (2006); Bromwich et al. (2004); Lenaerts et al. (2012)], even though this model utilizes significantly more observations than previous models. Using the Gaussian process' uncertainty and model parameters, we propose 15 new measurement locations for field study utilizing a maximin space-filling, error-minimizing design; these potential measurements are identied to minimize future estimation uncertainty. Using currently accepted Antarctic mass balance estimates and our SMB estimate, we estimate net mass loss [Shepherd et al. (2012); Jacob et al. (2012)]. Furthermore, we discuss modeling details for both space-time data and combining field measurement data with output from mathematical models using the NNGP framework.
Active balance system and vibration balanced machine
NASA Technical Reports Server (NTRS)
White, Maurice A. (Inventor); Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor)
2005-01-01
An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass.
Uncertainty analysis on simple mass balance model to calculate critical loads for soil acidity
Harbin Li; Steven G. McNulty
2007-01-01
Simple mass balance equations (SMBE) of critical acid loads (CAL) in forest soil were developed to assess potential risks of air pollutants to ecosystems. However, to apply SMBE reliably at large scales, SMBE must be tested for adequacy and uncertainty. Our goal was to provide a detailed analysis of uncertainty in SMBE so that sound strategies for scaling up CAL...
Estimating ground-water inflow to lakes in central Florida using the isotope mass-balance approach
Sacks, Laura A.
2002-01-01
The isotope mass-balance approach was used to estimate ground-water inflow to 81 lakes in the central highlands and coastal lowlands of central Florida. The study area is characterized by a subtropical climate and numerous lakes in a mantled karst terrain. Ground-water inflow was computed using both steady-state and transient formulations of the isotope mass-balance equation. More detailed data were collected from two study lakes, including climatic, hydrologic, and isotopic (hydrogen and oxygen isotope ratio) data. For one of these lakes (Lake Starr), ground-water inflow was independently computed from a water-budget study. Climatic and isotopic data collected from the two lakes were similar even though they were in different physiographic settings about 60 miles apart. Isotopic data from all of the study lakes plotted on an evaporation trend line, which had a very similar slope to the theoretical slope computed for Lake Starr. These similarities suggest that data collected from the detailed study lakes can be extrapolated to the rest of the study area. Ground-water inflow computed using the isotope mass-balance approach ranged from 0 to more than 260 inches per year (or 0 to more than 80 percent of total inflows). Steady-state and transient estimates of ground-water inflow were very similar. Computed ground-water inflow was most sensitive to uncertainty in variables used to calculate the isotopic composition of lake evaporate (isotopic compositions of lake water and atmospheric moisture and climatic variables). Transient results were particularly sensitive to changes in the isotopic composition of lake water. Uncertainty in ground-water inflow results is considerably less for lakes with higher ground-water inflow than for lakes with lower ground-water inflow. Because of these uncertainties, the isotope mass-balance approach is better used to distinguish whether ground-water inflow quantities fall within certain ranges of values, rather than for precise
Schievano, Andrea; D'Imporzano, Giuliana; Salati, Silvia; Adani, Fabrizio
2011-09-01
The mass balance (input/output mass flows) of full-scale anaerobic digestion (AD) processes should be known for a series of purposes, e.g. to understand carbon and nutrients balances, to evaluate the contribution of AD processes to elemental cycles, especially when digestates are applied to agricultural land and to measure the biodegradation yields and the process efficiency. In this paper, three alternative methods were studied, to determine the mass balance in full-scale processes, discussing their reliability and applicability. Through a 1-year survey on three full-scale AD plants and through 38 laboratory-scale batch digesters, the congruency of the considered methods was demonstrated and a linear equation was provided that allows calculating the wet weight losses (WL) from the methane produced (MP) by the plant (WL=41.949*MP+20.853, R(2)=0.950, p<0.01). Additionally, this new tool was used to calculate carbon, nitrogen, phosphorous and potassium balances of the three observed AD plants. Copyright © 2011 Elsevier Ltd. All rights reserved.
Hydrothermal liquefaction of high- and low-lipid algae: Mass and energy balances.
Cheng, Feng; Cui, Zheng; Mallick, Kwonit; Nirmalakhandan, Nagamany; Brewer, Catherine E
2018-06-01
Hydrothermal liquefaction (HTL) of high-lipid microalgae Nannochloropsis salina (N. salina) and low-lipid microalgae Galdieria sulphuraria (G. sulphuraria) were run under subcritical conditions (310-350 °C and 10-17 MPa) in a 1.8 L batch autoclave system. HTL mass and energy balances for both species were compared under different operating conditions to predict the optimum reaction conditions for new algae strains based on their feedstock composition. Bio-crude oils and chars were characterized by bomb calorimetry, elemental analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), and thermogravimetric analysis (TGA). Under the optimized conditions, 59 wt% and 31 wt% bio-crude oil yields were obtained from HTL of N. salina and G. sulphuraria, while 85% and 59% of the feedstock energy were partitioned into N. salina-derived and G. sulphuraria-derived bio-crude oils, respectively. More favorable energy balances were related to shorter reaction times and higher algal solid contents. Copyright © 2018 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Beamer, J. P.; Hill, D. F.; Arendt, A.; Liston, G. E.
2016-05-01
A comprehensive study of the Gulf of Alaska (GOA) drainage basin was carried out to improve understanding of the coastal freshwater discharge (FWD) and glacier volume loss (GVL). Hydrologic processes during the period 1980-2014 were modeled using a suite of physically based, spatially distributed weather, energy-balance snow/ice melt, soil water balance, and runoff routing models at a high-resolution (1 km horizontal grid; daily time step). Meteorological forcing was provided by the North American Regional Reanalysis (NARR), Modern Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR) data sets. Streamflow and glacier mass balance modeled using MERRA and CFSR compared well with observations in four watersheds used for calibration in the study domain. However, only CFSR produced regional seasonal and long-term trends in water balance that compared favorably with independent Gravity Recovery and Climate Experiment (GRACE) and airborne altimetry data. Mean annual runoff using CFSR was 760 km3 yr-1, 8% of which was derived from the long-term removal of stored water from glaciers (glacier volume loss). The annual runoff from CFSR was partitioned into 63% snowmelt, 17% glacier ice melt, and 20% rainfall. Glacier runoff, taken as the sum of rainfall, snow, and ice melt occurring each season on glacier surfaces, was 38% of the total seasonal runoff, with the remaining runoff sourced from nonglacier surfaces. Our simulations suggests that existing GRACE solutions, previously reported to represent glacier mass balance alone, are actually measuring the full water budget of land and ice surfaces.
NASA Astrophysics Data System (ADS)
Davaze, Lucas; Rabatel, Antoine; Arnaud, Yves; Sirguey, Pascal; Six, Delphine; Letreguilly, Anne; Dumont, Marie
2017-04-01
Increasing the number of glaciers monitored for surface mass balance is very challenging, especially using laborious methods based on in situ data. Complementary methods are therefore required to quantify the surface mass balance of unmonitored glaciers. The current study relies on the so-called albedo method, based on the analysis of albedo maps retrieved from optical satellite imagery acquired since 2000 by the MODIS sensor, onboard of TERRA satellite. Recent studies performed on single glaciers in the French Alps, the Himalayas or the Southern Alps of New Zealand revealed substantial relationships between summer minimum glacier-wide surface albedo and annual mass balance, because this minimum surface albedo is directly related to accumulation-area ratio and the equilibrium-line altitude. On the basis of 30 glaciers located in the French Alps where annual surface mass balance are available, our study conducted on the period 2000-2015 confirms the robustness and reliability of the relationship between the summer minimum surface albedo and the annual surface mass balance. At the seasonal scale, the integrated summer surface albedo is significantly correlated with the summer mass balance of the six glaciers seasonally surveyed. For the winter season, four of the six glaciers showed a significant correlation when linking the winter surface mass balance and the integrated winter surface albedo, using glacier-dependent thresholds to filter the albedo signal. Sensitivity study on the computed cloud detection algorithm revealed high confidence in retrieved albedo maps. These results are promising to monitor both annual and seasonal glacier-wide surface mass balances of individual glaciers at a regional scale using optical satellite images.
NASA Astrophysics Data System (ADS)
Rott, Helmut; Abdel Jaber, Wael; Wuite, Jan; Scheiblauer, Stefan; Floricioiu, Dana; Melchior van Wessem, Jan; Nagler, Thomas; Miranda, Nuno; van den Broeke, Michiel R.
2018-04-01
We analysed volume change and mass balance of outlet glaciers on the northern Antarctic Peninsula over the periods 2011 to 2013 and 2013 to 2016, using high-resolution topographic data from the bistatic interferometric radar satellite mission TanDEM-X. Complementary to the geodetic method that applies DEM differencing, we computed the net mass balance of the main outlet glaciers using the mass budget method, accounting for the difference between the surface mass balance (SMB) and the discharge of ice into an ocean or ice shelf. The SMB values are based on output of the regional climate model RACMO version 2.3p2. To study glacier flow and retrieve ice discharge we generated time series of ice velocity from data from different satellite radar sensors, with radar images of the satellites TerraSAR-X and TanDEM-X as the main source. The study area comprises tributaries to the Larsen A, Larsen Inlet and Prince Gustav Channel embayments (region A), the glaciers calving into the Larsen B embayment (region B) and the glaciers draining into the remnant part of the Larsen B ice shelf in Scar Inlet (region C). The glaciers of region A, where the buttressing ice shelf disintegrated in 1995, and of region B (ice shelf break-up in 2002) show continuing losses in ice mass, with significant reduction of losses after 2013. The mass balance numbers for the grounded glacier area of region A are -3.98 ± 0.33 Gt a-1 from 2011 to 2013 and -2.38 ± 0.18 Gt a-1 from 2013 to 2016. The corresponding numbers for region B are -5.75 ± 0.45 and -2.32 ± 0.25 Gt a-1. The mass balance in region C during the two periods was slightly negative, at -0.54 ± 0.38 Gt a-1 and -0.58 ± 0.25 Gt a-1. The main share in the overall mass losses of the region was contributed by two glaciers: Drygalski Glacier contributing 61 % to the mass deficit of region A, and Hektoria and Green glaciers accounting for 67 % to the mass deficit of region B. Hektoria and Green glaciers accelerated significantly in 2010
Mass spectrometry in Earth sciences: the precise and accurate measurement of time.
Schaltegger, Urs; Wotzlaw, Jörn-Frederik; Ovtcharova, Maria; Chiaradia, Massimo; Spikings, Richard
2014-01-01
Precise determinations of the isotopic compositions of a variety of elements is a widely applied tool in Earth sciences. Isotope ratios are used to quantify rates of geological processes that occurred during the previous 4.5 billion years, and also at the present time. An outstanding application is geochronology, which utilizes the production of radiogenic daughter isotopes by the radioactive decay of parent isotopes. Geochronological tools, involving isotopic analysis of selected elements from smallest volumes of minerals by thermal ionization mass spectrometry, provide precise and accurate measurements of time throughout the geological history of our planet over nine orders of magnitude, from the accretion of the proto-planetary disk, to the timing of the last glaciation. This article summarizes the recent efforts of the Isotope Geochemistry, Geochronology and Thermochronology research group at the University of Geneva to advance the U-Pb geochronological tool to achieve unprecedented precision and accuracy, and presents two examples of its application to two significant open questions in Earth sciences: what are the triggers and timescales of volcanic supereruptions, and what were the causes of mass extinctions in the geological past, driven by global climatic and environmental deterioration?
ERIC Educational Resources Information Center
Barrera-Garrido, Azael
2017-01-01
In order to measure the mass of an object in the absence of gravity, one useful tool for many decades has been the inertial balance. One of the simplest forms of inertial balance is made by two mass holders or pans joined together with two stiff metal plates, which act as springs.
NASA Astrophysics Data System (ADS)
Alves, Gelio; Wang, Guanghui; Ogurtsov, Aleksey Y.; Drake, Steven K.; Gucek, Marjan; Suffredini, Anthony F.; Sacks, David B.; Yu, Yi-Kuo
2016-02-01
Correct and rapid identification of microorganisms is the key to the success of many important applications in health and safety, including, but not limited to, infection treatment, food safety, and biodefense. With the advance of mass spectrometry (MS) technology, the speed of identification can be greatly improved. However, the increasing number of microbes sequenced is challenging correct microbial identification because of the large number of choices present. To properly disentangle candidate microbes, one needs to go beyond apparent morphology or simple `fingerprinting'; to correctly prioritize the candidate microbes, one needs to have accurate statistical significance in microbial identification. We meet these challenges by using peptidome profiles of microbes to better separate them and by designing an analysis method that yields accurate statistical significance. Here, we present an analysis pipeline that uses tandem MS (MS/MS) spectra for microbial identification or classification. We have demonstrated, using MS/MS data of 81 samples, each composed of a single known microorganism, that the proposed pipeline can correctly identify microorganisms at least at the genus and species levels. We have also shown that the proposed pipeline computes accurate statistical significances, i.e., E-values for identified peptides and unified E-values for identified microorganisms. The proposed analysis pipeline has been implemented in MiCId, a freely available software for Microorganism Classification and Identification. MiCId is available for download at http://www.ncbi.nlm.nih.gov/CBBresearch/Yu/downloads.html.
Hindle, Ralph; Noestheden, Matthew; Peru, Kerry; Headley, John
2013-04-19
This study details the development of a routine method for quantitative analysis of oil sands naphthenic acids, which are a complex class of compounds found naturally and as contaminants in oil sands process waters from Alberta's Athabasca region. Expanding beyond classical naphthenic acids (CnH2n-zO2), those compounds conforming to the formula CnH2n-zOx (where 2≥x≤4) were examined in commercial naphthenic acid and environmental water samples. HPLC facilitated a five-fold reduction in ion suppression when compared to the more commonly used flow injection analysis. A comparison of 39 model naphthenic acids revealed significant variability in response factors, demonstrating the necessity of using naphthenic acid mixtures for quantitation, rather than model compounds. It was also demonstrated that naphthenic acidic heterogeneity (commercial and environmental) necessitates establishing a single NA mix as the standard against which all quantitation is performed. The authors present the first ISO17025 accredited method for the analysis of naphthenic acids in water using HPLC high resolution accurate mass time-of-flight mass spectrometry. The method detection limit was 1mg/L total oxy-naphthenic acids (Sigma technical mix). Copyright © 2013 Elsevier B.V. All rights reserved.
Engine balance apparatus and accessory drive device
NASA Technical Reports Server (NTRS)
Egleston, Robert W. (Inventor)
2002-01-01
A balancing mechanism for an engine that has a rotating crankshaft and reciprocating pistons. The balancing mechanism comprises a primary balance mass assembly non-rotatably and removably affixed to the crankshaft. The primary mass assembly comprises a primary mass affixed to a primary hub portion and a primary cap portion removably affixed to the primary hub portion to clamp a portion of the crankshaft therebetween. A secondary balance mass assembly may be rotatably and removably supported on the crankshaft. A driver assembly is affixed to the crankshaft to cause the secondary balance mass to rotate in a direction that is opposite to the direction in which the crank shaft is rotating. The driver assembly may include auxiliary gears configured to transport rotary power to auxiliary components. The gears are readily detachable from the apparatus to facilitate inspection and repair operations.
Transfer of arsenic from poultry feed to poultry litter: A mass balance study.
Gupta, Sanjay K; Le, X Chris; Kachanosky, Gary; Zuidhof, Martin J; Siddique, Tariq
2018-07-15
Roxarsone (rox), an arsenic (As) containing organic compound, is a common feed additive used in poultry production. To determine if As present in rox is excreted into the poultry litter without any retention in chicken meat for safe human consumption, the transference of As from the feed to poultry excreta was assessed using two commercial chicken strains fed with and without dietary rox. The results revealed that both the strains had similar behaviour in growth (chicken weight; 2.17-2.25kg), feed consumption (282-300kgpen -1 initially containing 102 chicken) and poultry litter production (73-81kgpen -1 ) during the growth phase of 35days. Our mass balance calculations showed that chickens ingested 2669-2730mg As with the feed and excreted out 2362-2896mg As in poultry litter during the growth period of 28days when As containing feed was used, yielding As recovery between 86 and 108%. Though our complementary studies show that residual arsenic species in rox-fed chicken meat may have relevance to human exposure, insignificant retention of total As in the chicken meat substantiates our mass balance results. The results are important in evaluating the fate of feed additive used in poultry production and its potential environmental implications if As containing poultry litter is applied to soil for crop production. Copyright © 2018 Elsevier B.V. All rights reserved.
2012-01-01
Background Effective pretreatment is key to achieving high enzymatic saccharification efficiency in processing lignocellulosic biomass to fermentable sugars, biofuels and value-added products. Ionic liquids (ILs), still relatively new class of solvents, are attractive for biomass pretreatment because some demonstrate the rare ability to dissolve all components of lignocellulosic biomass including highly ordered (crystalline) cellulose. In the present study, three ILs, 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), 1-ethyl-3-methylimidazolium chloride ([C2mim]Cl), 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) are used to dissolve/pretreat and fractionate sugarcane bagasse. In these IL-based pretreatments the biomass is completely or partially dissolved in ILs at temperatures greater than 130°C and then precipitated by the addition of an antisolvent to the IL biomass mixture. For the first time mass balances of IL-based pretreatments are reported. Such mass balances, along with kinetics data, can be used in process modelling and design. Results Lignin removals of 10% mass of lignin in bagasse with [C4mim]Cl, 50% mass with [C2mim]Cl and 60% mass with [C2mim]OAc, are achieved by limiting the amount of water added as antisolvent to 0.5 water:IL mass ratio thus minimising lignin precipitation. Enzyme saccharification (24 h, 15FPU) yields (% cellulose mass in starting bagasse) from the recovered solids rank as: [C2mim]OAc(83%) > >[C2mim]Cl(53%) = [C4mim]Cl(53%). Composition of [C2mim]OAc-treated solids such as low lignin, low acetyl group content and preservation of arabinosyl groups are characteristic of aqueous alkali pretreatments while those of chloride IL-treated solids resemble aqueous acid pretreatments. All ILs are fully recovered after use (100% mass as determined by ion chromatography). Conclusions In all three ILs regulated addition of water as an antisolvent effected a polysaccharide enriched precipitate since some of the lignin remained dissolved
Andres, Britta; Engström, Ann-Christine; Blomquist, Nicklas; Forsberg, Sven; Dahlström, Christina; Olin, Håkan
2016-01-01
Symmetric electric double-layer capacitors (EDLCs) have equal masses of the same active material in both electrodes. However, having equal electrode masses may prevent the EDLC to have the largest possible specific capacitance if the sizes of the hydrated anions and cations in the electrolyte differ because the electrodes and the electrolyte may not be completely utilized. Here we demonstrate how this issue can be resolved by mass balancing. If the electrode masses are adjusted according to the size of the ions, one can easily increase an EDLC’s specific capacitance. To that end, we performed galvanostatic cycling to measure the capacitances of symmetric EDLCs with different electrode mass ratios using four aqueous electrolytes— Na2SO4, H2SO4, NaOH, and KOH (all with a concentration of 1 M)—and compared these to the theoretical optimal electrode mass ratio that we calculated using the sizes of the hydrated ions. Both the theoretical and experimental values revealed lower-than-1 optimal electrode ratios for all electrolytes except KOH. The largest increase in capacitance was obtained for EDLCs with NaOH as electrolyte. Specifically, we demonstrate an increase of the specific capacitance by 8.6% by adjusting the electrode mass ratio from 1 to 0.86. Our findings demonstrate that electrode mass balancing is a simple and inexpensive method to increase the capacitance of EDLCs. Furthermore, our results imply that one can reduce the amount of unused material in EDLCs and thus decrease their weight, volume and cost. PMID:27658253
NASA Astrophysics Data System (ADS)
Cambaliza, M. O. L.; Shepson, P. B.; Caulton, D. R.; Stirm, B.; Samarov, D.; Gurney, K. R.; Turnbull, J.; Davis, K. J.; Possolo, A.; Karion, A.; Sweeney, C.; Moser, B.; Hendricks, A.; Lauvaux, T.; Mays, K.; Whetstone, J.; Huang, J.; Razlivanov, I.; Miles, N. L.; Richardson, S. J.
2014-09-01
Urban environments are the primary contributors to global anthropogenic carbon emissions. Because much of the growth in CO2 emissions will originate from cities, there is a need to develop, assess, and improve measurement and modeling strategies for quantifying and monitoring greenhouse gas emissions from large urban centers. In this study the uncertainties in an aircraft-based mass balance approach for quantifying carbon dioxide and methane emissions from an urban environment, focusing on Indianapolis, IN, USA, are described. The relatively level terrain of Indianapolis facilitated the application of mean wind fields in the mass balance approach. We investigate the uncertainties in our aircraft-based mass balance approach by (1) assessing the sensitivity of the measured flux to important measurement and analysis parameters including wind speed, background CO2 and CH4, boundary layer depth, and interpolation technique, and (2) determining the flux at two or more downwind distances from a point or area source (with relatively large source strengths such as solid waste facilities and a power generating station) in rapid succession, assuming that the emission flux is constant. When we quantify the precision in the approach by comparing the estimated emissions derived from measurements at two or more downwind distances from an area or point source, we find that the minimum and maximum repeatability were 12 and 52%, with an average of 31%. We suggest that improvements in the experimental design can be achieved by careful determination of the background concentration, monitoring the evolution of the boundary layer through the measurement period, and increasing the number of downwind horizontal transect measurements at multiple altitudes within the boundary layer.
NASA Astrophysics Data System (ADS)
Koppes, M.; Conway, H.; Rasmussen, L. A.; Chernos, M.
2011-09-01
Mass balance variations of Glaciar San Rafael, the northernmost tidewater glacier in the Southern Hemisphere, are reconstructed over the period 1950-2005 using NCEP-NCAR reanalysis climate data together with sparse, local historical observations of air temperature, precipitation, accumulation, ablation, thinning, calving, and glacier retreat. The combined observations over the past 50 yr indicate that Glaciar San Rafael has thinned and retreated since 1959, with a total mass loss of ~22 km3 of ice eq. Over that period, except for a short period of cooling from 1998-2003, the climate has become progressively warmer and drier, which has resulted primarily in pervasive thinning of the glacier surface and a decrease in calving rates, with only minor acceleration in retreat of the terminus. A comparison of calving fluxes derived from the mass balance variations and from theoretical calving and sliding laws suggests that calving rates are inversely correlated with retreat rates, and that terminus geometry is more important than balance fluxes to the terminus in driving calving dynamics. For Glaciar San Rafael, regional climate warming has not yet resulted in the significant changes in glacier length seen in other calving glaciers in the region, emphasizing the complex dynamics between climate inputs, topographic constraints and glacier response in calving glacier systems.
NASA Astrophysics Data System (ADS)
Koppes, M.; Conway, H.; Rasmussen, L. A.; Chernos, M.
2011-04-01
Mass balance variations of Glaciar San Rafael, the most equatorial tidewater glacier in the North Patagonian Icefield, are reconstructed over the period 1950-2005 using NCEP-NCAR reanalysis climate data together with sparse, local historical observations of air temperature, precipitation, accumulation, ablation, thinning, calving, and glacier retreat. The combined observations over the past 50 yr indicate that Glaciar San Rafael has thinned and retreated since 1959, with a total mass loss of ~22 km3 of ice equivalent. Over that period, except for a short period of cooling from 1998-2003, the climate has become progressively warmer and drier, which has resulted primarily in pervasive thinning of the glacier surface and a decrease in calving rates, with only minor acceleration in retreat of the terminus. A comparison of calving fluxes derived from the mass balance variations and from theoretical calving and sliding laws suggest that calving rates are inversely correlated with retreat rates, and that terminus geometry is more important than changes in balance fluxes to the terminus in driving calving dynamics. For Glaciar San Rafael, regional climate warming has not yet resulted in the significant changes in glacier length seen in other calving glaciers in the region, emphasizing the complex dynamics between climate inputs, topographic constraints and glacier response in calving glacier systems.
Geochemical cycling, mass balance, and Earth’s dynamic structure (Invited)
NASA Astrophysics Data System (ADS)
Allegre, C. J.
2009-12-01
The use of radiogenic tracers is now established as one of the standard methods (together with seismic tomography) to constrain Earth models. One of the advantages of radiogenic tracers is that they constrain not only present day structures, but also their historical evolution since the earliest time. A mandatory condition is to use not only one but all of the available isotopic systems, with their diverse cycling properties and different radioactive half-lives. Mass balances calculations are the basic tool which allows one to use quantitatively the various tracers. However, the inverse method approach, when applied to mass balance, is strongly non-linear, particularly for tracers with intermediate to short half lives. 142Nd, 82W, and 129Xe allows one to define a consistent model for the Present and past evolutions. Results point to a 3-layer model for the present mantle: an upper mantle with two layers separated by the 450 km discontinuity, and a lower mantle below the 670 km discontinuity. These layers all convect independently though none of them is fully isolated. They exchange matter and energy, not necessarily through the same process. For instance, most hotspots (though not all of them!) are boundary layer instabilities generated at the 670 km discontinuity, but there is important heat transfer from the lower mantle through megablobs. Recent results on the Hadean period are in agreement with core-mantle- atmosphere differentiation at 4444 My. The early crust was mostly anorthositic but has been recycled into the upper mantle within the first billion years. Formation of granitic continents started at 4300 My. 80% of their material was already present on the surface as acidic rocks by 2500 My. The reworking process involved in continental development increased continuously with time and today is the dominant process. Continents are now in a stage of steady state, with general addition of mantle and subducted continental material.
Bosy-Westphal, Anja; Müller, Manfred J
2015-09-01
For the assessment of energy balance or monitoring of therapeutic interventions, there is a need for noninvasive and highly precise methods of body composition analysis that are able to accurately measure small changes in fat and fat-free mass (FFM). The use of quantitative magnetic resonance (QMR) for measurement of body composition has long been established in animal studies. There are, however, only a few human studies that examine the validity of this method. These studies have consistently shown a high precision of QMR and only a small underestimation of fat mass by QMR when compared with a 4-compartment model as a reference. An underestimation of fat mass by QMR is also supported by the comparison between measured energy balance (as a difference between energy intake and energy expenditure) and energy balance predicted from changes in fat mass and FFM. Fewer calories were lost and gained as fat mass compared with the value expected from measured energy balance. Current evidence in healthy humans has shown that QMR is a valid and precise method for noninvasive measurement of body composition. Contrary to standard reference methods, such as densitometry and dual X-ray absorptiometry, QMR results are independent of FFM hydration. However, despite a high accuracy and a low minimal detectable change, underestimation of fat mass by QMR is possible and limits the use of this method for quantification of energy balance.
Hourly mass and snow energy balance measurements from Mammoth Mountain, CA USA, 2011-2017
NASA Astrophysics Data System (ADS)
Bair, Edward H.; Davis, Robert E.; Dozier, Jeff
2018-03-01
The mass and energy balance of the snowpack govern its evolution. Direct measurement of these fluxes is essential for modeling the snowpack, yet there are few sites where all the relevant measurements are taken. Mammoth Mountain, CA USA, is home to the Cold Regions Research and Engineering Laboratory and University of California - Santa Barbara Energy Site (CUES), one of five energy balance monitoring sites in the western US. There is a ski patrol study site on Mammoth Mountain, called the Sesame Street Snow Study Plot, with automated snow and meteorological instruments where new snow is hand-weighed to measure its water content. There is also a site at Mammoth Pass with automated precipitation instruments. For this dataset, we present a clean and continuous hourly record of selected measurements from the three sites covering the 2011-2017 water years. Then, we model the snow mass balance at CUES and compare model runs to snow pillow measurements. The 2011-2017 period was marked by exceptional variability in precipitation, even for an area that has high year-to-year variability. The driest year on record, and one of the wettest years, occurred during this time period, making it ideal for studying climatic extremes. This dataset complements a previously published dataset from CUES containing a smaller subset of daily measurements. In addition to the hand-weighed SWE, novel measurements include hourly broadband snow albedo corrected for terrain and other measurement biases. This dataset is available with a digital object identifier: https://doi.org/10.21424/R4159Q.
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.
Mass balance of nitrogen and potassium in urban groundwater in Central Africa, Yaounde/Cameroon.
Kringel, R; Rechenburg, A; Kuitcha, D; Fouépé, A; Bellenberg, S; Kengne, I M; Fomo, M A
2016-03-15
Mass flow of nutrients from innumerous latrines and septic tanks was assessed to best describe the groundwater quality situation in the urban environment of Yaounde. 37 groundwater samples were taken at the end of dry season 2012 and analysed for nutrient related (NO3(-), NH4(+), NO2(-), K(+), Cl(-), HPO4(2-) and TOC) and physico-chemical ambient parameters. A survey on waste water discharge close to water points constrained point sources from sanitation. The results showed that the median of nitrate concentration exceeds the WHO limit. We realized that EC increases from the geogenic background to very high levels in the urban area within short distance, suggesting anthropogenic input. Dug wells showed nitrate and ammonium in equivalent concentrations, indicating incomplete nitrification and mandating their inclusion into water type classification. The mass turnover of nutrients in urban groundwater scales high in comparison to national statistical figures on fertilizer import for 2012. A mass N,K balance for infiltration water overestimates observed concentrations by a factor of 4.5. The marked balance gap is attributed to dynamic non-equilibrium between input and output. Unresolved questions like a) urban sanitation, b) hygiene & health and c) environmental protection urgently call for closing the nutrient cycle. In the light of Cameroonian strategies on rural development, tackling the groundwater nutrient, urban agriculture, food--NEXUS might partially restore urban and periurban ecosystem services under economical constraints and thus improve living conditions. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.
BALANCE: Towards a Usable Pervasive Wellness Application with Accurate Activity Inference
Denning, Tamara; Andrew, Adrienne; Chaudhri, Rohit; Hartung, Carl; Lester, Jonathan; Borriello, Gaetano; Duncan, Glen
2010-01-01
Technology offers the potential to objectively monitor people’s eating and activity behaviors and encourage healthier lifestyles. BALANCE is a mobile phone-based system for long term wellness management. The BALANCE system automatically detects the user’s caloric expenditure via sensor data from a Mobile Sensing Platform unit worn on the hip. Users manually enter information on foods eaten via an interface on an N95 mobile phone. Initial validation experiments measuring oxygen consumption during treadmill walking and jogging show that the system’s estimate of caloric output is within 87% of the actual value. Future work will refine and continue to evaluate the system’s efficacy and develop more robust data input and activity inference methods. PMID:20445819
A carbon isotope mass balance for an anoxic marine sediment: Isotopic signatures of diagenesis
NASA Technical Reports Server (NTRS)
Boehme, Susan E.
1993-01-01
A carbon isotope mass balance was determined for the sediments of Cape Lookout Bight, NC to constrain the carbon budgets published previously. The diffusive, ebullitive and burial fluxes of sigma CO2 and CH4, as well as the carbon isotope signatures of these fluxes, were measured. The flux-weighted isotopic signature of the remineralized carbon (-18.9 plus or minus 2.7 per mil) agreed with the isotopic composition of the remineralized organic carbon determined from the particulate organic carbon (POC) delta(C-13) profiles (-19.2 plus or minus 0.2), verifying the flux and isotopic signature estimates. The measured delta(C-13) values of the sigma CO2 and CH4 diffusive fluxes were significantly different from those calculated from porewater gradients. The differences appear to be influenced by methane oxidation at the sediment-water interface, although other potential processes cannot be excluded. The isotope mass balance provides important information concerning the locations of potential diagenetic isotope effects. Specifically, the absence of downcore change in the delta(C-13) value of the POC fraction and the identical isotopic composition of the POC and the products of remineralization indicate that no isotopic fractionation is expressed during the initial breakdown of the POC, despite its isotopically heterogeneous composition.
Engine balance apparatus and accessory drive device
NASA Technical Reports Server (NTRS)
Brogdon, James William (Inventor); Gill, David Keith (Inventor)
2000-01-01
A balancing mechanism for an engine that has a rotating crankshaft and reciprocating pistons such as those engines used in automobiles, aircrafts, boats, piston-driven compressors, piston-driven slider crank mechanisms, etc. The present balancing mechanism may comprise a first balance mass non-rotatably affixed to the crankshaft and a second balance mass rotatably supported on the crankshaft. A driver assembly is affixed to crankshaft to cause the second balance mass to rotate in a direction that is opposite to the direction in which the crank shaft is rotating. The driver assembly may include auxiliary gears configured to transport rotary power to auxiliary components.
Stanley, Jeffrey R.; Adkins, Joshua N.; Slysz, Gordon W.; Monroe, Matthew E.; Purvine, Samuel O.; Karpievitch, Yuliya V.; Anderson, Gordon A.; Smith, Richard D.; Dabney, Alan R.
2011-01-01
Current algorithms for quantifying peptide identification confidence in the accurate mass and time (AMT) tag approach assume that the AMT tags themselves have been correctly identified. However, there is uncertainty in the identification of AMT tags, as this is based on matching LC-MS/MS fragmentation spectra to peptide sequences. In this paper, we incorporate confidence measures for the AMT tag identifications into the calculation of probabilities for correct matches to an AMT tag database, resulting in a more accurate overall measure of identification confidence for the AMT tag approach. The method is referred to as Statistical Tools for AMT tag Confidence (STAC). STAC additionally provides a Uniqueness Probability (UP) to help distinguish between multiple matches to an AMT tag and a method to calculate an overall false discovery rate (FDR). STAC is freely available for download as both a command line and a Windows graphical application. PMID:21692516
Balanced Flow Meters without Moving Parts
NASA Technical Reports Server (NTRS)
Kelley, Anthony R.; VanBuskirk, Paul
2008-01-01
Balanced flow meters are recent additions to an established class of simple, rugged flow meters that contain no moving parts in contact with flow and are based on measurement of pressure drops across objects placed in flow paths. These flow meters are highly accurate, minimally intrusive, easily manufacturable, and reliable. A balanced flow meter can be easily mounted in a flow path by bolting it between conventional pipe flanges. A balanced flow meter can be used to measure the flow of any of a variety of liquids or gases, provided that it has been properly calibrated. Relative to the standard orifice-plate flow meter, the balanced flow meter introduces less turbulence and two times less permanent pressure loss and is therefore capable of offering 10 times greater accuracy and repeatability with less dissipation of energy. A secondary benefit of the reduction of turbulence is the reduction of vibration and up to 15 times less acoustic noise generation. Both the balanced flow meter and the standard orifice-plate flow meter are basically disks that contain holes and are instrumented with pressure transducers on their upstream and downstream faces. The most obvious difference between them is that the standard orifice plate contains a single, central hole while the balanced flow meter contains multiple holes. The term 'balanced' signifies that in designing the meter, the sizes and locations of the holes are determined in an optimization procedure that involves balancing of numerous factors, including volumetric flow, mass flow, dynamic pressure, kinetic energy, all in an effort to minimize such undesired effects as turbulence, pressure loss, dissipation of kinetic energy, and non-repeatability and nonlinearity of response over the anticipated range of flow conditions. Due to proper balancing of these factors, recent testing demonstrated that the balanced flow-meter performance was similar to a Venturi tube in both accuracy and pressure recovery, but featured reduced
The Lake Michigan (LM) Mass Balance Study was conducted to measure and model polychlorinated biphenyls (PCBs) and other anthropogenic substances to gain a better understanding of the transport, fate, and effects of these substances within the system and to aid managers in the env...
Wert, David M.; Hile, Elizabeth S.; Studenski, Stephanie A.; Brach, Jennifer S.
2011-01-01
Background The incidence of obesity is increasing in older adults, with associated worsening in the burden of disability. Little is known about the impact of body mass index (BMI) on self-report and performance-based balance and mobility measures in older adults. Objective The purposes of this study were (1) to examine the association of BMI with measures of balance and mobility and (2) to explore potential explanatory factors. Design This was a cross-sectional, observational study. Methods Older adults (mean age=77.6 years) who participated in an ongoing observational study (N=120) were classified as normal weight (BMI=18.5–24.9 kg/m2), overweight (BMI=25.0–29.9 kg/m2), moderately obese (BMI=30.0–34.9 kg/m2), or severely obese (BMI≥35 kg/m2). Body mass index data were missing for one individual; thus, data for 119 participants were included in the analysis. Mobility and balance were assessed using self-report and performance-based measures and were compared among weight groups using analysis of variance and chi-square analysis for categorical data. Multiple linear regression analysis was used to examine the association among BMI, mobility, and balance after controlling for potential confounding variables. Results Compared with participants who were of normal weight or overweight, those with moderate or severe obesity were less likely to report their mobility as very good or excellent (52%, 55%, 39%, and 6%, respectively); however, there was no difference in self-report of balance among weight groups. Participants with severe obesity (n=17) had the lowest levels of mobility on the performance-based measures, followed by those who were moderately obese (n=31), overweight (n=42), and of normal weight (n=29). There were no differences on performance-based balance measures among weight groups. After controlling for age, sex, minority status, physical activity level, education level, and comorbid conditions, BMI still significantly contributed to mobility (
NASA Astrophysics Data System (ADS)
Grima, C.; Koch, I.; Greenbaum, J. S.; Soderlund, K. M.; Blankenship, D. D.; Young, D. A.; Fitzsimons, S.
2017-12-01
The McMurdo ice shelves (northern and southern MIS), adjacent to the eponymous station and the Ross Ice Shelf, Antarctica, are known for large gradients in surface snow accumulation and snow/ice impurities. Marine ice accretion and melting are important contributors to MIS's mass balance. Due to erosive winds, the southern MIS (SMIS) shows a locally negative surface mass balance. Thus, marine ice once accreted at the ice shelf base crops out at the surface. However, the exact processes that exert primary control on SMIS mass balance have remained elusive. Radar statistical reconnaissance (RSR) is a recent technique that has been used to characterize the surface properties of the Earth's cryosphere, Mars, and Titan from the stochastic character of energy scattered by the surface. Here, we apply RSR to map the surface density and roughness of the SMIS and extend the technique to derive the basal reflectance and scattering coefficients of the ice-ocean interface. We use an airborne radar survey grid acquired over the SMIS in the 2014-2015 austral summer by the University of Texas Institute for Geophysics with the High Capability Radar Sounder (HiCARS2; 60-MHz center frequency and 15-MHz bandwidth). The RSR-derived snow density values and patterns agree with directly -measured ice shelf surface accumulation rates. We also compare the composition of SMIS ice surface samples to test the ability of RSR to discriminate ices with varying dielectric properties (e.g., marine versus meteoric ice) and hypothesize relationships between the RSR-derived basal reflectance/scattered coefficients and accretion or melting at the ice-ocean interface. This improved knowledge of air-ice and ice-ocean boundaries provides a new perspective on the processes governing SMIS surface and basal mass balance.
Strynar, Mark; Dagnino, Sonia; McMahen, Rebecca; Liang, Shuang; Lindstrom, Andrew; Andersen, Erik; McMillan, Larry; Thurman, Michael; Ferrer, Imma; Ball, Carol
2015-10-06
Recent scientific scrutiny and concerns over exposure, toxicity, and risk have led to international regulatory efforts resulting in the reduction or elimination of certain perfluorinated compounds from various products and waste streams. Some manufacturers have started producing shorter chain per- and polyfluorinated compounds to try to reduce the potential for bioaccumulation in humans and wildlife. Some of these new compounds contain central ether oxygens or other minor modifications of traditional perfluorinated structures. At present, there has been very limited information published on these "replacement chemistries" in the peer-reviewed literature. In this study we used a time-of-flight mass spectrometry detector (LC-ESI-TOFMS) to identify fluorinated compounds in natural waters collected from locations with historical perfluorinated compound contamination. Our workflow for discovery of chemicals included sequential sampling of surface water for identification of potential sources, nontargeted TOFMS analysis, molecular feature extraction (MFE) of samples, and evaluation of features unique to the sample with source inputs. Specifically, compounds were tentatively identified by (1) accurate mass determination of parent and/or related adducts and fragments from in-source collision-induced dissociation (CID), (2) in-depth evaluation of in-source adducts formed during analysis, and (3) confirmation with authentic standards when available. We observed groups of compounds in homologous series that differed by multiples of CF2 (m/z 49.9968) or CF2O (m/z 65.9917). Compounds in each series were chromatographically separated and had comparable fragments and adducts produced during analysis. We detected 12 novel perfluoroalkyl ether carboxylic and sulfonic acids in surface water in North Carolina, USA using this approach. A key piece of evidence was the discovery of accurate mass in-source n-mer formation (H(+) and Na(+)) differing by m/z 21.9819, corresponding to the
Estimating Regional Mass Balance of Himalayan Glaciers Using Hexagon Imagery: An Automated Approach
NASA Astrophysics Data System (ADS)
Maurer, J. M.; Rupper, S.
2013-12-01
Currently there is much uncertainty regarding the present and future state of Himalayan glaciers, which supply meltwater for river systems vital to more than 1.4 billion people living throughout Asia. Previous assessments of regional glacier mass balance in the Himalayas using various remote sensing and field-based methods give inconsistent results, and most assessments are over relatively short (e.g., single decade) timescales. This study aims to quantify multi-decadal changes in volume and extent of Himalayan glaciers through efficient use of the large database of declassified 1970-80s era Hexagon stereo imagery. Automation of the DEM extraction process provides an effective workflow for many images to be processed and glacier elevation changes quantified with minimal user input. The tedious procedure of manual ground control point selection necessary for block-bundle adjustment (as ephemeral data is not available for the declassified images) is automated using the Maximally Stable Extremal Regions algorithm, which matches image elements between raw Hexagon images and georeferenced Landsat 15 meter panchromatic images. Additional automated Hexagon DEM processing, co-registration, and bias correction allow for direct comparison with modern ASTER and SRTM elevation data, thus quantifying glacier elevation and area changes over several decades across largely inaccessible mountainous regions. As consistent methodology is used for all glaciers, results will likely reveal significant spatial and temporal patterns in regional ice mass balance. Ultimately, these findings could have important implications for future water resource management in light of environmental change.
Nitrogen losses from dairy manure estimated through nitrogen mass balance and chemical markers
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.
Regional Modeling of Dust Mass Balance and Radiative Forcing over East Asia using WRF-Chem
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chen, Siyu; Zhao, Chun; Qian, Yun
The Weather Research and Forecasting model with Chemistry (WRF-Chem) is used to investigate the seasonal and annual variations of mineral dust over East Asia during 2007-2011, with a focus on the dust mass balance and radiative forcing. A variety of measurements from in-stu and satellite observations have been used to evaluate simulation results. Generally, WRF-Chem reproduces not only the column variability but also the vertical profile and size distribution of mineral dust over and near the dust source regions of East Asia. We investigate the dust lifecycle and the factors that control the seasonal and spatial variations of dust massmore » balance and radiative forcing over the seven sub-regions of East Asia, i.e. source regions, the Tibetan Plateau, Northern China, Southern China, the ocean outflow region, and Korea-Japan regions. Results show that, over the source regions, transport and dry deposition are the two dominant sinks. Transport contributes to ~30% of the dust sink over the source regions. Dust results in a surface cooling of up to -14 and -10 W m-2, atmospheric warming of up to 20 and 15 W m-2, and TOA cooling of -5 and -8 W m-2 over the two major dust source regions of East Asia, respectively. Over the Tibetan Plateau, transport is the dominant source with a peak in summer. Over identified outflow regions, maximum dust mass loading in spring is contributed by the transport. Dry and wet depositions are the comparably dominant sinks, but wet deposition is larger than dry deposition over the Korea-Japan region, particularly in spring (70% versus 30%). The WRF-Chem simulations can generally capture the measured features of dust aerosols and its radaitve properties and dust mass balance over East Asia, which provides confidence for use in further investigation of dust impact on climate over East Asia.« less
Reconstruction of mass balance variations for Franz Josef Glacier, New Zealand, 1913 to 1989
DOE Office of Scientific and Technical Information (OSTI.GOV)
Woo, Mingko Woo; Fitzharris, B.B.
1992-11-01
A model of mass balance is constructed for the Franz Josef Glacier on the west coast of New Zealand. It uses daily data from a nearby, but short-record climate station. The model is extended back to 1913 by creating hybrid climate data from a long-record, but more distant, climate station. Its monthly data provide long-term temperature and precipitation trends, and daily fluctuations are simulated using a stochastic approach that is tuned to the characteristics of the short-record station. The glacier model provides estimates of equilibrium-line altitudes which are in reasonable agreement with those observed, and variations of cumulative mass balancemore » that correspond with patterns of advance and retreat of the glacier terminus.« less
Changes in the Mass Balance of the Greenland Ice Sheet in a Warming Climate During 2003-2009
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Luthcke, Scott
2010-01-01
Mass changes of the Greenland ice sheet (GIS) derived from ICESat and GRACE data both show that the net mass loss from GIS during 2003-2009 is about 175 Gt/year, which contributes 0.5mm/yr global sea-level rise. The rate of mass loss has increased significantly since the 1990's when the GIS was close to mass balance. Even though the GIS was close to mass balance during the 1990's, it was already showing characteristics of responding to8 warmer climate, specifically thinning at the margins and thickening inland at higher elevations. During 2003-2009, increased ice thinning due to increases in melting and acceleration of outlet glaciers began to strongly exceed the inland thickening from increases in accumulation. Over the entire GIS, the mass loss between the two periods, from increased melting and ice dynamics, increased by about 190 Gt/year while the mass gain, from increased precipitation and accumulation, increased by only about 15Gt/year. These ice changes occurred during a time when the temperature on GIS changed at rate of about 2K/decade. The distribution of elevation and mass changes derived from ICESat have high spatial resolution showing details over outlet glaciers, by drainage systems, and by elevation. However, information on the seasonal cycle of changes from ICESat data is limited, because the ICESat lasers were only operated during two to three campaigns per year of about 35 days duration each. In contrast, the temporal resolution of GRACE data, provided by the continuous data collection, is much better showing details of the seasonal cycle and the inter-annual variability. The differing sensitivity of the ICESat altimetry and the GRACE gravity methods to motion of the underlying bedrock from glacial isostatic adjustment (GIA) is used to evaluate the GIA corrections provided by models. The two data types are also combined to make estimates of the partitioning of the mass gains and losses among accumulation, melting, and ice discharge from outlet
Hinke, Jefferson T.; Perryman, Wayne L.; Goebel, Michael E.; LeRoi, Donald J.
2017-01-01
Measurements of body size and mass are fundamental to pinniped population management and research. Manual measurements tend to be accurate but are invasive and logistically challenging to obtain. Ground-based photogrammetric techniques are less invasive, but inherent limitations make them impractical for many field applications. The recent proliferation of unmanned aerial systems (UAS) in wildlife monitoring has provided a promising new platform for the photogrammetry of free-ranging pinnipeds. Leopard seals (Hydrurga leptonyx) are an apex predator in coastal Antarctica whose body condition could be a valuable indicator of ecosystem health. We aerially surveyed leopard seals of known body size and mass to test the precision and accuracy of photogrammetry from a small UAS. Flights were conducted in January and February of 2013 and 2014 and 50 photogrammetric samples were obtained from 15 unrestrained seals. UAS-derived measurements of standard length were accurate to within 2.01 ± 1.06%, and paired comparisons with ground measurements were statistically indistinguishable. An allometric linear mixed effects model predicted leopard seal mass within 19.40 kg (4.4% error for a 440 kg seal). Photogrammetric measurements from a single, vertical image obtained using UAS provide a noninvasive approach for estimating the mass and body condition of pinnipeds that may be widely applicable. PMID:29186134
Krause, Douglas J; Hinke, Jefferson T; Perryman, Wayne L; Goebel, Michael E; LeRoi, Donald J
2017-01-01
Measurements of body size and mass are fundamental to pinniped population management and research. Manual measurements tend to be accurate but are invasive and logistically challenging to obtain. Ground-based photogrammetric techniques are less invasive, but inherent limitations make them impractical for many field applications. The recent proliferation of unmanned aerial systems (UAS) in wildlife monitoring has provided a promising new platform for the photogrammetry of free-ranging pinnipeds. Leopard seals (Hydrurga leptonyx) are an apex predator in coastal Antarctica whose body condition could be a valuable indicator of ecosystem health. We aerially surveyed leopard seals of known body size and mass to test the precision and accuracy of photogrammetry from a small UAS. Flights were conducted in January and February of 2013 and 2014 and 50 photogrammetric samples were obtained from 15 unrestrained seals. UAS-derived measurements of standard length were accurate to within 2.01 ± 1.06%, and paired comparisons with ground measurements were statistically indistinguishable. An allometric linear mixed effects model predicted leopard seal mass within 19.40 kg (4.4% error for a 440 kg seal). Photogrammetric measurements from a single, vertical image obtained using UAS provide a noninvasive approach for estimating the mass and body condition of pinnipeds that may be widely applicable.
Edwards, Joel; Othman, Maazuza; Crossin, Enda; Burn, Stewart
2017-11-01
When assessing the environmental and human health impact of a municipal food waste (FW) management system waste managers typically rely on the principles of the waste hierarchy; using metrics such as the mass or rate of waste that is 'prepared for recycling,' 'recovered for energy,' or 'sent to landfill.' These metrics measure the collection and sorting efficiency of a waste system but are incapable of determining the efficiency of a system to turn waste into a valuable resource. In this study a life cycle approach was employed using a system boundary that includes the entire waste service provision from collection to safe end-use or disposal. A life cycle inventory of seven waste management systems was calculated, including the first service wide inventory of FW management through kitchen in-sink disposal (food waste disposer). Results describe the mass, energy and water balance of each system along with key emissions profile. It was demonstrated that the energy balance can differ significantly from its' energy generation, exemplified by mechanical biological treatment, which was the best system for generating energy from waste but only 5 th best for net-energy generation. Furthermore, the energy balance of kitchen in-sink disposal was shown to be reduced because 31% of volatile solids were lost in pre-treatment. The study also confirmed that higher FW landfill diversion rates were critical for reducing many harmful emissions to air and water. Although, mass-balance analysis showed that the alternative end-use of the FW material may still contain high impact pollutants. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Abdullahi, K. L.; Delgado-Saborit, J. M.; Harrison, Roy M.
2018-04-01
Use of a Chemical Mass Balance model is one of the two most commonly used approaches to estimating atmospheric concentrations of cooking aerosol. Such models require the input of chemical profiles for each of the main sources contributing to particulate matter mass and there is appreciable evidence from the literature that not only the mass emission but also the chemical composition of particulate matter varies according to the food being prepared and the style of cooking. In this study, aerosol has been sampled in the laboratory from four different styles of cooking, i.e. Indian, Chinese, Western and African cooking. The chemical profiles of molecular markers have been quantified and are used individually within a Chemical Mass Balance model applied to air samples collected in a multi-ethnic area of Birmingham, UK. The model results give a source contribution estimate for cooking aerosol which is consistent with other comparable UK studies, but also shows a very low sensitivity of the model to the cooking aerosol profile utilised. A survey of local restaurants suggested a wide range of cooking styles taking place which may explain why no one profile gives an appreciably better fit in the CMB model.
NASA Astrophysics Data System (ADS)
Whorton, E.; Headman, A.; Shean, D. E.; McCann, E.
2017-12-01
Understanding the implications of glacier recession on water resources in the western U.S. requires quantifying glacier mass change across large regions over several decades. Very few glaciers in North America have long-term continuous field measurements of glacier mass balance. However, systematic aerial photography campaigns began in 1957 on many glaciers in the western U.S. and Alaska. These historical, vertical aerial stereo-photographs documenting glacier evolution have recently become publically available. Digital elevation models (DEM) of the transient glacier surface preserved in each imagery timestamp can be derived, then differenced to calculate glacier volume and mass change to improve regional geodetic solutions of glacier mass balance. In order to batch process these data, we use Python-based algorithms and Agisoft Photoscan structure from motion (SfM) photogrammetry software to semi-automate DEM creation, and orthorectify and co-register historical aerial imagery in a high-performance computing environment. Scanned photographs are rotated to reduce scaling issues, cropped to the same size to remove fiducials, and batch histogram equalization is applied to improve image quality and aid pixel-matching algorithms using the Python library OpenCV. Processed photographs are then passed to Photoscan through the Photoscan Python library to create DEMs and orthoimagery. To extend the period of record, the elevation products are co-registered to each other, airborne LiDAR data, and DEMs derived from sub-meter commercial satellite imagery. With the exception of the placement of ground control points, the process is entirely automated with Python. Current research is focused on: one, applying these algorithms to create geodetic mass balance time series for the 90 photographed glaciers in Washington State and two, evaluating the minimal amount of positional information required in Photoscan to prevent distortion effects that cannot be addressed during co
NETPATH-WIN: an interactive user version of the mass-balance model, NETPATH
El-Kadi, A. I.; Plummer, Niel; Aggarwal, P.
2011-01-01
NETPATH-WIN is an interactive user version of NETPATH, an inverse geochemical modeling code used to find mass-balance reaction models that are consistent with the observed chemical and isotopic composition of waters from aquatic systems. NETPATH-WIN was constructed to migrate NETPATH applications into the Microsoft WINDOWS® environment. The new version facilitates model utilization by eliminating difficulties in data preparation and results analysis of the DOS version of NETPATH, while preserving all of the capabilities of the original version. Through example applications, the note describes some of the features of NETPATH-WIN as applied to adjustment of radiocarbon data for geochemical reactions in groundwater systems.
Etheridge, Alexandra B.
2013-01-01
he U.S. Geological Survey (USGS), in cooperation with Idaho Department of Environmental Quality, developed spreadsheet mass-balance models for total phosphorus using results from three synoptic sampling periods conducted in the lower Boise River watershed during August and October 2012, and March 2013. The modeling reach spanned 46.4 river miles (RM) along the Boise River from Veteran’s Memorial Parkway in Boise, Idaho (RM 50.2), to Parma, Idaho (RM 3.8). The USGS collected water-quality samples and measured streamflow at 14 main-stem Boise River sites, two Boise River north channel sites, two sites on the Snake River upstream and downstream of its confluence with the Boise River, and 17 tributary and return-flow sites. Additional samples were collected from treated effluent at six wastewater treatment plants and two fish hatcheries. The Idaho Department of Water Resources quantified diversion flows in the modeling reach. Total phosphorus mass-balance models were useful tools for evaluating sources of phosphorus in the Boise River during each sampling period. The timing of synoptic sampling allowed the USGS to evaluate phosphorus inputs to and outputs from the Boise River during irrigation season, shortly after irrigation ended, and soon before irrigation resumed. Results from the synoptic sampling periods showed important differences in surface-water and groundwater distribution and phosphorus loading. In late August 2012, substantial streamflow gains to the Boise River occurred from Middleton (RM 31.4) downstream to Parma (RM 3.8). Mass-balance model results indicated that point and nonpoint sources (including groundwater) contributed phosphorus loads to the Boise River during irrigation season. Groundwater exchange within the Boise River in October 2012 and March 2013 was not as considerable as that measured in August 2012. However, groundwater discharge to agricultural tributaries and drains during non-irrigation season was a large source of discharge and
Liu, Yan-Chun; Xiao, Sa; Yang, Kun; Ling, Li; Sun, Zhi-Liang; Liu, Zhao-Ying
2017-06-01
This study reports an applicable analytical strategy of comprehensive identification and structure characterization of target components from Gelsemium elegans by using high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QqTOF MS) based on the use of accurate mass databases combined with MS/MS spectra. The databases created included accurate masses and elemental compositions of 204 components from Gelsemium and their structural data. The accurate MS and MS/MS spectra were acquired through data-dependent auto MS/MS mode followed by an extraction of the potential compounds from the LC-QqTOF MS raw data of the sample. The same was matched using the databases to search for targeted components in the sample. The structures for detected components were tentatively characterized by manually interpreting the accurate MS/MS spectra for the first time. A total of 57 components have been successfully detected and structurally characterized from the crude extracts of G. elegans, but has failed to differentiate some isomers. This analytical strategy is generic and efficient, avoids isolation and purification procedures, enables a comprehensive structure characterization of target components of Gelsemium and would be widely applicable for complicated mixtures that are derived from Gelsemium preparations. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.
Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard
NASA Astrophysics Data System (ADS)
Granskog, Mats A.; Rösel, Anja; Dodd, Paul A.; Divine, Dmitry; Gerland, Sebastian; Martma, Tõnu; Leng, Melanie J.
2017-03-01
The salinity and water oxygen isotope composition (δ18O) of 29 first-year (FYI) and second-year (SYI) Arctic sea ice cores (total length 32.0 m) from the drifting ice pack north of Svalbard were examined to quantify the contribution of snow to sea ice mass. Five cores (total length 6.4 m) were analyzed for their structural composition, showing variable contribution of 10-30% by granular ice. In these cores, snow had been entrained in 6-28% of the total ice thickness. We found evidence of snow contribution in about three quarters of the sea ice cores, when surface granular layers had very low δ18O values. Snow contributed 7.5-9.7% to sea ice mass balance on average (including also cores with no snow) based on δ18O mass balance calculations. In SYI cores, snow fraction by mass (12.7-16.3%) was much higher than in FYI cores (3.3-4.4%), while the bulk salinity of FYI (4.9) was distinctively higher than for SYI (2.7). We conclude that oxygen isotopes and salinity profiles can give information on the age of the ice and enables distinction between FYI and SYI (or older) ice in the area north of Svalbard.
Jones, B.F.; Herman, J.S.
2008-01-01
Geochemical research on natural weathering has often been directed towards explanations of the chemical composition of surface water and ground water resulting from subsurface water-rock interactions. These interactions are often defined as the incongruent dissolution of primary silicates, such as feldspar, producing secondary weathering products, such as clay minerals and oxyhydroxides, and solute fluxes (Meunier and Velde, 1979). The chemical composition of the clay-mineral product is often ignored. However, in earlier investigations, the saprolitic weathering profile at the South Fork Brokenback Run (SFBR) watershed, Shenandoah National Park, Virginia, was characterized extensively in terms of its mineralogical and chemical composition (Piccoli, 1987; Pochatila et al., 2006; Jones et al., 2007) and its basic hydrology. O'Brien et al. (1997) attempted to determine the contribution of primary mineral weathering to observed stream chemistry at SFBR. Mass-balance model results, however, could provide only a rough estimate of the weathering reactions because idealized mineral compositions were utilized in the calculations. Making use of detailed information on the mineral occurrence in the regolith, the objective of the present study was to evaluate the effects of compositional variation on mineral-solute mass-balance modelling and to generate plausible quantitative weathering reactions that support both the chemical evolution of the surface water and ground water in the catchment, as well as the mineralogical evolution of the weathering profile. ?? 2008 The Mineralogical Society.
GMI Instrument Spin Balance Method, Optimization, Calibration, and Test
NASA Technical Reports Server (NTRS)
Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph
2014-01-01
The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3 year mission life. Therefore, GMI must be very precisely balanced about the spin axis and CG to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.
GMI Instrument Spin Balance Method, Optimization, Calibration and Test
NASA Technical Reports Server (NTRS)
Ayari, Laoucet; Kubitschek, Michael; Ashton, Gunnar; Johnston, Steve; Debevec, Dave; Newell, David; Pellicciotti, Joseph
2014-01-01
The Global Microwave Imager (GMI) instrument must spin at a constant rate of 32 rpm continuously for the 3-year mission life. Therefore, GMI must be very precisely balanced about the spin axis and center of gravity (CG) to maintain stable scan pointing and to minimize disturbances imparted to the spacecraft and attitude control on-orbit. The GMI instrument is part of the core Global Precipitation Measurement (GPM) spacecraft and is used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center to design, build, and test the GMI instrument. The GMI design has to meet a challenging set of spin balance requirements and had to be brought into simultaneous static and dynamic spin balance after the entire instrument was already assembled and before environmental tests began. The focus of this contribution is on the analytical and test activities undertaken to meet the challenging spin balance requirements of the GMI instrument. The novel process of measuring the residual static and dynamic imbalances with a very high level of accuracy and precision is presented together with the prediction of the optimal balance masses and their locations.
Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992 - 2009
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Giovinetto, Mario B.
2011-01-01
Published mass balance estimates for the Antarctic Ice Sheet (AIS) lie between approximately +50 to -250 Gt/year for 1992 to 2009, which span a range equivalent to 15% of the annual mass input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar-altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (+28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. Although recent reports of large and accelerating rates of mass loss from GRACE=based studies cite agreement with IOM results, our evaluation does not support that conclusion. We find that the extrapolation used in the published IOM estimates for the 15 % of the periphery for which discharge velocities are not observed gives twice the rate of discharge per unit of associated ice-sheet area than the 85% faster-moving parts. Our calculations show that the published extrapolation overestimates the ice discharge by 282 Gt/yr compared to our assumption that the slower moving areas have 70% as much discharge per area as the faster moving parts. Also, published data on the time-series of discharge velocities and accumulation/precipitation do not support mass output increases or input decreases with time, respectively. Our modified IOM estimate, using the 70% discharge assumption and substituting input from a field-data compilation for input from an atmospheric model over 6% of area, gives a loss of only 13 Gt/year (versus 136 Gt/year) for the period around 2000. Two ERS-based estimates, our modified IOM, and a GRACE-based estimate for observations within 1992 to 2005 lie in a narrowed range of +27 to - 40 Gt/year, which is about 3% of the annual mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992-2001 is - 47 Gt
Accurate donor electron wave functions from a multivalley effective mass theory.
NASA Astrophysics Data System (ADS)
Pendo, Luke; Hu, Xuedong
Multivalley effective mass (MEM) theories combine physical intuition with a marginal need for computational resources, but they tend to be insensitive to variations in the wavefunction. However, recent papers suggest full Bloch functions and suitable central cell donor potential corrections are essential to replicating qualitative and quantitative features of the wavefunction. In this talk, we consider a variational MEM method that can accurately predict both spectrum and wavefunction of isolated phosphorus donors. As per Gamble et. al, we employ a truncated series representation of the Bloch function with a tetrahedrally symmetric central cell correction. We use a dynamic dielectric constant, a feature commonly seen in tight-binding methods. Uniquely, we use a freely extensible basis of either all Slater- or all Gaussian-type functions. With a large basis able to capture the influence of higher energy eigenstates, this method is well positioned to consider the influence of external perturbations, such as electric field or applied strain, on the charge density. This work is supported by the US Army Research Office (W911NF1210609).
The Lake Michigan (LM) Mass Balance Study was conducted to measure and model polychlorinated biphenyls (PCBs) and other anthropogenic substances to gain a better understanding of the transport, fate, and effects of these substances within the system and to aid managers in the env...
NASA Astrophysics Data System (ADS)
Wang, L.; Davis, J. L.; Tamisiea, M. E.
2017-12-01
The Antarctic ice sheet (AIS) holds about 60% of all fresh water on the Earth, an amount equivalent to about 58 m of sea-level rise. Observation of AIS mass change is thus essential in determining and predicting its contribution to sea level. While the ice mass loss estimates for West Antarctica (WA) and the Antarctic Peninsula (AP) are in good agreement, what the mass balance over East Antarctica (EA) is, and whether or not it compensates for the mass loss is under debate. Besides the different error sources and sensitivities of different measurement types, complex spatial and temporal variabilities would be another factor complicating the accurate estimation of the AIS mass balance. Therefore, a model that allows for variabilities in both melting rate and seasonal signals would seem appropriate in the estimation of present-day AIS melting. We present a stochastic filter technique, which enables the Bayesian separation of the systematic stripe noise and mass signal in decade-length GRACE monthly gravity series, and allows the estimation of time-variable seasonal and inter-annual components in the signals. One of the primary advantages of this Bayesian method is that it yields statistically rigorous uncertainty estimates reflecting the inherent spatial resolution of the data. By applying the stochastic filter to the decade-long GRACE observations, we present the temporal variabilities of the AIS mass balance at basin scale, particularly over East Antarctica, and decipher the EA mass variations in the past decade, and their role in affecting overall AIS mass balance and sea level.
The Six-Component Wind Balance
NASA Technical Reports Server (NTRS)
Zahm, A F
1923-01-01
Dr. Zahm's report is a description of the six-component wind-tunnel balance in use at the Aerodynamic Laboratory, Washington Navy Yard. The description of the balance gives the mechanical details and the method of operation, and is accompanied by line drawings showing the construction of the balance. The balance is of particular interest, as it allows the model to be set up quickly and accurately in roll, pitch, and yaw, without stopping the wind. It is possible to measure automatically, directly, and independently the drag, cross-wind force, and lift; also the rolling, pitching, and yawing moments. It is also possible to make the balance self-recording.
Ross, Charles W; Simonsick, William J; Bogusky, Michael J; Celikay, Recep W; Guare, James P; Newton, Randall C
2016-06-28
Ceramides are a central unit of all sphingolipids which have been identified as sites of biological recognition on cellular membranes mediating cell growth and differentiation. Several glycosphingolipids have been isolated, displaying immunomodulatory and anti-tumor activities. These molecules have generated considerable interest as potential vaccine adjuvants in humans. Accurate analyses of these and related sphingosine analogues are important for the characterization of structure, biological function, and metabolism. We report the complementary use of direct laser desorption ionization (DLDI), sheath flow electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) and high-field nuclear magnetic resonance (NMR) analysis for the rapid, accurate identification of hexacosanoylceramide and starting materials. DLDI does not require stringent sample preparation and yields representative ions. Sheath-flow ESI yields ions of the product and byproducts and was significantly better than monospray ESI due to improved compound solubility. Negative ion sheath flow ESI provided data of starting materials and products all in one acquisition as hexacosanoic acid does not ionize efficiently when ceramides are present. NMR provided characterization of these lipid molecules complementing the results obtained from MS analyses. NMR data was able to differentiate straight chain versus branched chain alkyl groups not easily obtained from mass spectrometry.
Jaffe, Jacob D; Keshishian, Hasmik; Chang, Betty; Addona, Theresa A; Gillette, Michael A; Carr, Steven A
2008-10-01
Verification of candidate biomarker proteins in blood is typically done using multiple reaction monitoring (MRM) of peptides by LC-MS/MS on triple quadrupole MS systems. MRM assay development for each protein requires significant time and cost, much of which is likely to be of little value if the candidate biomarker is below the detection limit in blood or a false positive in the original discovery data. Here we present a new technology, accurate inclusion mass screening (AIMS), designed to provide a bridge from unbiased discovery to MS-based targeted assay development. Masses on the software inclusion list are monitored in each scan on the Orbitrap MS system, and MS/MS spectra for sequence confirmation are acquired only when a peptide from the list is detected with both the correct accurate mass and charge state. The AIMS experiment confirms that a given peptide (and thus the protein from which it is derived) is present in the plasma. Throughput of the method is sufficient to qualify up to a hundred proteins/week. The sensitivity of AIMS is similar to MRM on a triple quadrupole MS system using optimized sample preparation methods (low tens of ng/ml in plasma), and MS/MS data from the AIMS experiments on the Orbitrap can be directly used to configure MRM assays. The method was shown to be at least 4-fold more efficient at detecting peptides of interest than undirected LC-MS/MS experiments using the same instrumentation, and relative quantitation information can be obtained by AIMS in case versus control experiments. Detection by AIMS ensures that a quantitative MRM-based assay can be configured for that protein. The method has the potential to qualify large number of biomarker candidates based on their detection in plasma prior to committing to the time- and resource-intensive steps of establishing a quantitative assay.
Tree carbon allocation dynamics determined using a carbon mass balance approach.
Klein, Tamir; Hoch, Günter
2015-01-01
Tree internal carbon (C) fluxes between compound and compartment pools are difficult to measure directly. Here we used a C mass balance approach to decipher these fluxes and provide a full description of tree C allocation dynamics. We collected independent measurements of tree C sinks, source and pools in Pinus halepensis in a semi-arid forest, and converted all fluxes to g C per tree d(-1) . Using this data set, a process flowchart was created to describe and quantify the tree C allocation on diurnal to annual time-scales. The annual C source of 24.5 kg C per tree yr(-1) was balanced by C sinks of 23.5 kg C per tree yr(-1) , which partitioned into 70%, 17% and 13% between respiration, growth, and litter (plus export to soil), respectively. Large imbalances (up to 57 g C per tree d(-1) ) were observed as C excess during the wet season, and as C deficit during the dry season. Concurrent changes in C reserves (starch) were sufficient to buffer these transient C imbalances. The C pool dynamics calculated using the flowchart were in general agreement with the observed pool sizes, providing confidence regarding our estimations of the timing, magnitude, and direction of the internal C fluxes. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.
Apicella, B; Wang, X; Passaro, M; Ciajolo, A; Russo, C
2016-10-15
Time-of-Flight (TOF) Mass Spectrometry is a powerful analytical technique, provided that an accurate calibration by standard molecules in the same m/z range of the analytes is performed. Calibration in a very large m/z range is a difficult task, particularly in studies focusing on the detection of high molecular weight clusters of different molecules or high molecular weight species. External calibration is the most common procedure used for TOF mass spectrometric analysis in the gas phase and, generally, the only available standards are made up of mixtures of noble gases, covering a small mass range for calibration, up to m/z 136 (higher mass isotope of xenon). In this work, an accurate calibration of a Molecular Beam Time-of Flight Mass Spectrometer (MB-TOFMS) is presented, based on the use of water clusters up to m/z 3000. The advantages of calibrating a MB-TOFMS with water clusters for the detection of analytes with masses above those of the traditional calibrants such as noble gases were quantitatively shown by statistical calculations. A comparison of the water cluster and noble gases calibration procedures in attributing the masses to a test mixture extending up to m/z 800 is also reported. In the case of the analysis of combustion products, another important feature of water cluster calibration was shown, that is the possibility of using them as "internal standard" directly formed from the combustion water, under suitable experimental conditions. The water clusters calibration of a MB-TOFMS gives rise to a ten-fold reduction in error compared to the traditional calibration with noble gases. The consequent improvement in mass accuracy in the calibration of a MB-TOFMS has important implications in various fields where detection of high molecular mass species is required. In combustion products analysis, it is also possible to obtain a new calibration spectrum before the acquisition of each spectrum, only modifying some operative conditions. Copyright © 2016
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mernild, Sebastian Haugard; Liston, Glen
2009-01-01
In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier ice melt, and glacier mass-balance simulations. A physically based snow-evolution modeling system (SnowModel) was used to simulate eight years (1998/99 to 2005/06) of snow accumulation and snow and glacier ice ablation from numerous small coastal marginal glaciers on the SW-part of Ammassalik Island in SE Greenland. These glaciers are regularly influenced by inversions and sea breezes associated with the adjacent relatively low temperature and frequently ice-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of airmore » temperature and snow and glacier melt rates, temperature inversion routines were added to MircoMet, the meteorological distribution sub-model used in SnowModel. The inversions were observed and modeled to occur during 84% of the simulation period. Modeled inversions were defined not to occur during days with strong winds and high precipitation rates due to the potential of inversion break-up. Field observations showed inversions to extend from sea level to approximately 300 m a.s.l., and this inversion level was prescribed in the model simulations. Simulations with and without the inversion routines were compared. The inversion model produced air temperature distributions with warmer lower elevation areas and cooler higher elevation areas than without inversion routines due to the use of cold sea-breeze base temperature data from underneath the inversion. This yielded an up to 2 weeks earlier snowmelt in the lower areas and up to 1 to 3 weeks later snowmelt in the higher elevation areas of the simulation domain. Averaged mean annual modeled surface mass-balance for all glaciers (mainly located above the inversion layer) was -720 {+-} 620 mm w.eq. y{sup -1} for inversion simulations, and -880 {+-} 620 mm w.eq. y{sup -1} without the inversion routines, a difference of 160 mm w
Gap-Balancing versus Measured Resection Technique in Total Knee Arthroplasty: A Comparison Study.
Churchill, Jessica L; Khlopas, Anton; Sultan, Assem A; Harwin, Steven F; Mont, Michael A
2018-01-01
Proper femoral component alignment in the axial plane during total knee arthroplasty (TKA) depends on accurate bone cuts and soft tissue balancing. Two methods that are used to achieve this are "measured resection" and "gap balancing." However, a controversy exists as to which method is more accurate and leads to better outcomes. Therefore, the purpose of this study was to evaluate: (1) implant survivorship, (2) patient outcomes, (3) complications, and (4) radiographic analysis comparing patients who underwent TKA with either gap-balancing or measured resection techniques. A total of 214 consecutive patients (221 knees) underwent primary TKA by a single surgeon between 2011 and 2012. Component alignment was achieved by using measured resection in 116 knees and gap balancing was used in 105 knees. The patients had a mean age of 66 years (range, 44-86 years) and a mean body mass index of 32 kg/m 2 (range, 22-52 kg/m 2 ). Patient range-of-motion (ROM) and Knee Society (KS) function and pain scores, and radiographic assessment, were assessed preoperatively and postoperatively at ∼6 weeks, 3 months, 1 year, and then annually. The mean follow-up time was 3 years. A Kaplan-Meier's analysis was performed to calculate the survivorship. The aseptic survivorship was 98% in both the measured resection and gap-balancing groups. The mean ROM was not significantly different between the measured resection and gap-balancing groups (123 vs. 123 degrees, p = 0.990). There were no significant differences between the two groups in terms of the KS function scores (86 vs. 85 points, p = 0.829) or the KS pain scores (93 vs. 92 points, p = 0.425). Otherwise, the radiographic evaluation at latest follow-up did not demonstrate any evidence of progressive radiolucencies or loosening, of any prosthesis. The results of this study found that at a mean follow-up of 3 years, both the measured resection and gap-balancing techniques achieved excellent survivorship and
Recent evolution and mass balance of Cordón Martial glaciers, Cordillera Fueguina Oriental
NASA Astrophysics Data System (ADS)
Strelin, Jorge; Iturraspe, Rodolfo
2007-10-01
Past and present glacier changes have been studied at Cordón Martial, Cordillera Fueguina Oriental, Tierra del Fuego, providing novel data for the Holocene deglaciation history of southern South America and extrapolating as well its future behavior based on predicted climatic changes. Regional geomorphologic and stratigraphic correlations indicate that the last glacier advance deposited the ice-proximal ("internal") moraines of Cordón Martial, around 330 14C yr BP, during the Late Little Ice Age (LLIA). Since then glaciers have receded slowly, until 60 years ago, when major glacier retreat started. There is a good correspondence for the past 100 years between the surface area variation of four small cirque glaciers at Cordón Martial and the annual temperature and precipitation data of Ushuaia. Between 1984 and 1998, Martial Este Glacier lost 0.64 ± 0.02 × 10 6 m 3 of ice mass (0.59 ± 0.02 × 10 6 m 3 w.e.), corresponding to an average ice thinning of 7.0 ± 0.2 m (6.4 ± 0.2 m w.e), according to repeated topographic mapping. More detailed climatic data have been obtained since 1998 at the Martial Este Glacier, including air temperature, humidity and solar radiation. These records, together with the monthly mass balance measured since March 2000, document the annual response of the Martial Este Glacier to the climate variation. Mass balances during hydrological years were positive in 2000, negative in 2001 and near equilibrium in 2002. Finally, using these data and the regional temperature trend projections, modeled for different future scenarios by the Atmosphere-Ocean Model (GISS-NASA/GSFC), potential climatic-change effects on this mountain glacier were extrapolated. The analysis shows that only the Martial Este Glacier may survive this century.
Three years of PM2.5 speciated data were collected and chemically analyzed using the IMPROVE protocol at the Beacon Hill site in Seattle. The data were analyzed by the Chemical Mass Balance Version 8 (CMB8) and Positive Matrix Factorization (PMF) source apportionment models. T...
NASA Technical Reports Server (NTRS)
Newsom, H. E.; Hagerty, J. J.; Shearer, C. W.
2002-01-01
New SIMS data for mobile elements in Lonar Crater clay minerals are remarkably similar to data for alteration material in the Lafayette Mars meteorite. This work strongly supports the use of terrestrial analogues for Mars, including a new mass balance model for mobile elements through time. Additional information is contained in the original extended abstract.
Microprocessor-Controlled Laser Balancing System
NASA Technical Reports Server (NTRS)
Demuth, R. S.
1985-01-01
Material removed by laser action as part tested for balance. Directed by microprocessor, laser fires appropriate amount of pulses in correct locations to remove necessary amount of material. Operator and microprocessor software interact through video screen and keypad; no programing skills or unprompted system-control decisions required. System provides complete and accurate balancing in single load-and-spinup cycle.
SPARC: MASS MODELS FOR 175 DISK GALAXIES WITH SPITZER PHOTOMETRY AND ACCURATE ROTATION CURVES
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lelli, Federico; McGaugh, Stacy S.; Schombert, James M., E-mail: federico.lelli@case.edu
2016-12-01
We introduce SPARC ( Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 μ m and high-quality rotation curves from previous H i/H α studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i mass–radius relation is extremely tight. We build detailedmore » mass models and quantify the ratio of baryonic to observed velocity ( V {sub bar}/ V {sub obs}) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ{sub ⋆}) at [3.6]. Assuming ϒ{sub ⋆} ≃ 0.5 M {sub ⊙}/ L {sub ⊙} (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity; (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii) V {sub bar}/ V {sub obs} varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ{sub ⋆} ≃ 0.2 M {sub ⊙}/ L {sub ⊙} as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ{sub ⋆} ≃ 0.7 M {sub ⊙}/ L {sub ⊙} at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang Huijun; Matsuto, Toshihiko, E-mail: matsuto@eng.hokudai.ac.jp
2011-03-15
Mass balance, energy consumption and cost are basic pieces of information necessary for selecting a waste management technology. In this study, composting facilities that treat different types of organic waste were studied by questionnaire survey and via a chemical analysis of material collected at the facilities. The mass balance was calculated on a dry weight basis because the moisture content of organic waste was very high. Even though the ratio of bulking material to total input varied in the range 0-65% on a dry basis, the carbon and ash content, carbon/nitrogen ratio, heavy metal content and inorganic nutrients in themore » compost were clearly influenced by the different characteristics of the input waste. The use of bulking material was not correlated with ash or elemental content in the compost. The operating costs were categorised into two groups. There was some economy of scale for wages and maintenance cost, but the costs for electricity and fuel were proportional to the amount of waste. Differences in operating costs can be explained by differences in the process characteristics.« less
Szulc, Pawel; Beck, Tom J; Marchand, François; Delmas, Pierre D
2005-05-01
In 796 men, 50-85 years of age, decreased relative skeletal muscle mass index was associated with narrower bones, thinner cortices, and a consequent decreased bending strength (lower section modulus), as well as with impaired balance and an increased risk of falls. In men, appendicular skeletal muscle mass (ASM) is correlated positively with BMC and areal BMD (aBMD). In elderly men, low muscle mass and strength (sarcopenia) is associated with difficulties in daily living activities. The aim of this study was to evaluate if ASM is correlated with bone size, mechanical properties of bones, balance, and risk of falls in elderly men. This study used 796 men, 50-85 years of age, belonging to the MINOS cohort. Lifestyle factors were evaluated by standardized questionnaires. Estimates of mechanical bone properties were derived from aBMD measured by DXA. ASM was estimated by DXA. The relative skeletal muscle mass index (RASM) was calculated as ASM/(body height)(2.3). After adjustment for age, body size, tobacco smoking, professional physical activity, and 17beta-estradiol concentration, RASM was correlated positively with BMC, aBMD, external diameter, and cortical thickness (r = 0.17-0.34, p < 0.0001) but not with volumetric BMD. Consequently, RASM was correlated with section modulus (r = 0.29-0.39, p < 0.0001). Men in the lowest quartile of RASM had section modulus of femoral neck and distal radius lower by 12-18% in comparison with men in the highest quartile of RASM. In contrast, bone width was not correlated with fat mass, reflecting the load of body weight (except for L(3)), which suggests that the muscular strain may exert a direct stimulatory effect on periosteal apposition. After adjustment for confounding variables, a decrease in RASM was associated with increased risk of falls and of inability to accomplish clinical tests of muscle strength, static balance, and dynamic balance (odds ratio per 1 SD decrease in RASM, 1.31-2.23; p < 0.05-0.001). In elderly men
NASA Astrophysics Data System (ADS)
Piermattei, Livia; Carturan, Luca; Calligaro, Simone; Blasone, Giacomo; Guarnieri, Alberto; Tarolli, Paolo; Dalla Fontana, Giancarlo; Vettore, Antonio
2014-05-01
Digital elevation models (DEMs) of glaciated terrain are commonly used to measure changes in geometry and hence infer the mass balance of glaciers. Different tools and methods exist to obtain information about the 3D geometry of terrain. Recent improvements on the quality and performance of digital cameras for close-range photogrammetry, and the development of automatic digital photogrammetric processing makes the 'structure from motion' photogrammetric technique (SfM) competitive for high quality 3D models production, compared to efficient but also expensive and logistically-demanding survey technologies such as airborn and terrestrial laser scanner (TLS). The purpose of this work is to test the SfM approach, using a consumer-grade SLR camera and the low-cost computer vision-based software package Agisoft Photoscan (Agisoft LLC), to monitor the mass balance of Montasio Occidentale glacier, a 0.07km2, low-altitude, debris-covered glacier located in the Eastern Italian Alps. The quality of the 3D models produced by the SfM process has been assessed by comparison with digital terrain models obtained through TLS surveys carried out at the same dates. TLS technique has indeed proved to be very effective in determining the volume change of this glacier in the last years. Our results shows that the photogrammetric approach can produce point cloud densities comparable to those derived from TLS measurements. Furthermore, the horizontal and vertical accuracies are also of the same order of magnitude as for TLS (centimetric to decimetric). The effect of different landscape characteristics (e.g. distance from the camera or terrain gradient) and of different substrata (rock, debris, ice, snow and firn) was also evaluated in terms of SfM reconstruction's accuracy vs. TLS. Given the good results obtained on the Montasio Occidentale glacier, it can be concluded that the terrestrial photogrammetry, with the advantageous features of portability, ease of use and above all low costs
ACCURATE LOW-MASS STELLAR MODELS OF KOI-126
DOE Office of Scientific and Technical Information (OSTI.GOV)
Feiden, Gregory A.; Chaboyer, Brian; Dotter, Aaron, E-mail: gregory.a.feiden@dartmouth.edu
2011-10-10
The recent discovery of an eclipsing hierarchical triple system with two low-mass stars in a close orbit (KOI-126) by Carter et al. appeared to reinforce the evidence that theoretical stellar evolution models are not able to reproduce the observational mass-radius relation for low-mass stars. We present a set of stellar models for the three stars in the KOI-126 system that show excellent agreement with the observed radii. This agreement appears to be due to the equation of state implemented by our code. A significant dispersion in the observed mass-radius relation for fully convective stars is demonstrated; indicative of the influencemore » of physics currently not incorporated in standard stellar evolution models. We also predict apsidal motion constants for the two M dwarf companions. These values should be observationally determined to within 1% by the end of the Kepler mission.« less
The Lake Michigan Mass Balance Project (LMMBP) was initiated to support the development of a Lake Wide Management Plan (LaMP) for Lake Michigan. As one of the models in the LMMBP modeling framework, the Level 2 Lake Michigan containment transport and fate (LM2) model has been dev...
Pierson-Wickmann, Anne-Catherine; Gruau, Gérard; Jardé, Emilie; Gaury, Nicolas; Brient, Luc; Lengronne, Marion; Crocq, André; Helle, Daniel; Lambert, Thibault
2011-04-01
A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9mgL(-1)) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ(13)C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ(13)C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ(13)C values of the DOC recovered in the reservoir (-28.5±0.2‰; n=22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ(13)C in algae=-30.1±0.3‰; n=2) being indistinguishable from the δ(13)C values of allochthonous DOC from inflowing rivers (-28.6±0.1‰; n=8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs. Copyright © 2010 Elsevier Ltd. All rights reserved.
Leak detectability of the Norman Wells pipeline by mass balance
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liou, J.C.P.
Pipeline leak detection using software-based systems is becoming common practice. The detectability of such systems is measured by how small and how quickly a leak can be detected. Algorithms used and measurement uncertainties determine leak detectability. This paper addresses leak detectability using mass balance, establishes leak detectability for Norman Wells pipelines, and compares it with field leak test results. The pipeline is operated by the Interprovincial Pipe Line (IPL) Inc., of Edmonton, Canada. It is a 12.75-inch outside diameter steel pipe with variable wall thickness. The length of the pipe is approximately 550 miles (868.9 km). The pipeline transports lightmore » crude oil at a constant flow rate of about 250 m{sup 3}/hr. The crude oil can enter the pipeline at two locations. Besides the Norman Wells inlet, there is a side line near Zama terminal that can inject crude oil into the pipeline.« less
NASA Astrophysics Data System (ADS)
Johnson, E. S.; Rupper, S.; Steenburgh, W. J.; Strong, C.; Kochanski, A.
2017-12-01
Climate model outputs are often used as inputs to glacier energy and mass balance models, which are essential glaciological tools for testing glacier sensitivity, providing mass balance estimates in regions with little glaciological data, and providing a means to model future changes. Climate model outputs, however, are sensitive to the choice of physical parameterizations, such as those for cloud microphysics, land-surface schemes, surface layer options, etc. Furthermore, glacier mass balance (MB) estimates that use these climate model outputs as inputs are likely sensitive to the specific parameterization schemes, but this sensitivity has not been carefully assessed. Here we evaluate the sensitivity of glacier MB estimates across the Indus Basin to the selection of cloud microphysics parameterizations in the Weather Research and Forecasting Model (WRF). Cloud microphysics parameterizations differ in how they specify the size distributions of hydrometeors, the rate of graupel and snow production, their fall speed assumptions, the rates at which they convert from one hydrometeor type to the other, etc. While glacier MB estimates are likely sensitive to other parameterizations in WRF, our preliminary results suggest that glacier MB is highly sensitive to the timing, frequency, and amount of snowfall, which is influenced by the cloud microphysics parameterization. To this end, the Indus Basin is an ideal study site, as it has both westerly (winter) and monsoonal (summer) precipitation influences, is a data-sparse region (so models are critical), and still has lingering questions as to glacier importance for local and regional resources. WRF is run at a 4 km grid scale using two commonly used parameterizations: the Thompson scheme and the Goddard scheme. On average, these parameterizations result in minimal differences in annual precipitation. However, localized regions exhibit differences in precipitation of up to 3 m w.e. a-1. The different schemes also impact the
Mass balance of decabromodiphenyl ethane and decabromodiphenyl ether in a WWTP.
Ricklund, Niklas; Kierkegaard, Amelie; McLachlan, Michael S; Wahlberg, Cajsa
2009-01-01
The additive flame retardant decabromodiphenyl ethane (deBDethane) has been identified in the environment, but little is known about its environmental behaviour. It is structurally similar to decabromodiphenyl ether (decaBDE), making it conceivable that it may also become an environmental contaminant of concern. In this study a mass balance of deBDethane and decaBDE was undertaken in a modern WWTP in Stockholm serving 7.05x10(5) inhabitants. Flow proportional samples of plant influent and effluent as well as daily grab samples of digested sludge were collected during two 7-day periods. All samples were analyzed with GC/HRMS using isotope labelled internal standards. The mean mass flows of deBDethane and decaBDE to the WWTP were 6.0 g per day and 55 g per day, respectively. Of this, less than 1% of both BFRs left the WWTP via the effluent, while the bulk was sequestered into the digested sludge, where the mean concentrations of deBDethane and decaBDE were 81 and 800 ng g(-1)d.wt., respectively. It is concluded that the transfer efficiency of deBDethane from the technosphere to the environment via WWTPs is similar to that of decaBDE.
Langseth, Brian J.; Jones, Michael L.; Riley, Stephen C.
2014-01-01
Ecopath with Ecosim (EwE) is a widely used modeling tool in fishery research and management. Ecopath requires a mass-balanced snapshot of a food web at a particular point in time, which Ecosim then uses to simulate changes in biomass over time. Initial inputs to Ecopath, including estimates for biomasses, production to biomass ratios, consumption to biomass ratios, and diets, rarely produce mass balance, and thus ad hoc changes to inputs are required to balance the model. There has been little previous research of whether ad hoc changes to achieve mass balance affect Ecosim simulations. We constructed an EwE model for the offshore community of Lake Huron, and balanced the model using four contrasting but realistic methods. The four balancing methods were based on two contrasting approaches; in the first approach, production of unbalanced groups was increased by increasing either biomass or the production to biomass ratio, while in the second approach, consumption of predators on unbalanced groups was decreased by decreasing either biomass or the consumption to biomass ratio. We compared six simulation scenarios based on three alternative assumptions about the extent to which mortality rates of prey can change in response to changes in predator biomass (i.e., vulnerabilities) under perturbations to either fishing mortality or environmental production. Changes in simulated biomass values over time were used in a principal components analysis to assess the comparative effect of balancing method, vulnerabilities, and perturbation types. Vulnerabilities explained the most variation in biomass, followed by the type of perturbation. Choice of balancing method explained little of the overall variation in biomass. Under scenarios where changes in predator biomass caused large changes in mortality rates of prey (i.e., high vulnerabilities), variation in biomass was greater than when changes in predator biomass caused only small changes in mortality rates of prey (i.e., low
Nitrogen emissions from broilers measured by mass balance over eighteen consecutive flocks.
Coufal, C D; Chavez, C; Niemeyer, P R; Carey, J B
2006-03-01
Emission of nitrogen in the form of ammonia from poultry rearing facilities has been an important topic for the poultry industry because of concerns regarding the effects of ammonia on the environment. Sound scientific data is needed to accurately estimate air emissions from poultry operations. Many factors, such as season of the year, ambient temperature and humidity, bird health, and management practices can influence ammonia volatilization from broiler rearing facilities. Precise results are often difficult to attain from commercial facilities, particularly over long periods of time. Therefore, an experiment was conducted to determine nitrogen loss from broilers in a research facility under conditions simulating commercial production for 18 consecutive flocks. Broilers were reared to 40 to 42 d of age and fed diets obtained from a commercial broiler integrator. New rice hulls were used for litter for the first flock, and the same litter was recycled for all subsequent flocks with caked litter removed between flocks. All birds, feeds, and litter materials entering and leaving the facility were quantified, sampled, and analyzed for total nitrogen content. Nitrogen loss was calculated by the mass balance method in which loss was equal to the difference between the nitrogen inputs and the nitrogen outputs. Nitrogen partitioning as a percentage of inputs averaged 15.29, 6.84, 55.52, 1.27, and 21.08% for litter, caked litter, broiler carcasses, mortalities, and nitrogen loss, respectively, over all eighteen flocks. During the production of 18 flocks of broilers on the same recycled litter, the average nitrogen emission rate was calculated to range from 4.13 to 19.74 g of N/ kg of marketed broiler (grams of nitrogen per kilogram) and averaged 11.07 g of N/kg. Nitrogen loss was significantly (P < 0.05) greater for flocks reared in summer vs. winter. Results of this experiment have demonstrated that the rate of nitrogen volatilization from broiler grow-out facilities
NASA Astrophysics Data System (ADS)
Berger, Sophie; Drews, Reinhard; Helm, Veit; Sun, Sainan; Pattyn, Frank
2017-11-01
Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB), i.e. the difference between refreezing and melting. Here, we present an improved technique - based on satellite observations - to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmospheric-model surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from -14.7 to 8.6 m a-1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km) lowers by 0.5 to 1.4 m a-1, which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks). However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing) toward the ice shelf front. Although the absolute, satellite-based BMB values remain uncertain, we have
NASA Astrophysics Data System (ADS)
Nias, I. J.; Cornford, S. L.; Payne, A. J.
2018-04-01
High-resolution ice flow modeling requires bedrock elevation and ice thickness data, consistent with one another and with modeled physics. Previous studies have shown that gridded ice thickness products that rely on standard interpolation techniques (such as Bedmap2) can be inconsistent with the conservation of mass, given observed velocity, surface elevation change, and surface mass balance, for example, near the grounding line of Pine Island Glacier, West Antarctica. Using the BISICLES ice flow model, we compare results of simulations using both Bedmap2 bedrock and thickness data, and a new interpolation method that respects mass conservation. We find that simulations using the new geometry result in higher sea level contribution than Bedmap2 and reveal decadal-scale trends in the ice stream dynamics. We test the impact of several sliding laws and find that it is at least as important to accurately represent the bedrock and initial ice thickness as the choice of sliding law.
ERIC Educational Resources Information Center
King, Kenneth P.
2007-01-01
The inertial balance is one device that can help students to quantify the quality of inertia--a body's resistance to a change in movement--in more generally understood terms of mass. In this hands-on activity, students use the inertial balance to develop a more quantitative idea of what mass means in an inertial sense. The activity also helps…
Glacier crevasses: Observations, models, and mass balance implications
NASA Astrophysics Data System (ADS)
Colgan, William; Rajaram, Harihar; Abdalati, Waleed; McCutchan, Cheryl; Mottram, Ruth; Moussavi, Mahsa S.; Grigsby, Shane
2016-03-01
We review the findings of approximately 60 years of in situ and remote sensing studies of glacier crevasses, as well as the three broad classes of numerical models now employed to simulate crevasse fracture. The relatively new insight that mixed-mode fracture in local stress equilibrium, rather than downstream advection alone, can introduce nontrivial curvature to crevasse geometry may merit the reinterpretation of some key historical observation studies. In the past three decades, there have been tremendous advances in the spatial resolution of satellite imagery, as well as fully automated algorithms capable of tracking crevasse displacements between repeat images. Despite considerable advances in developing fully transient three-dimensional ice flow models over the past two decades, both the zero stress and linear elastic fracture mechanics crevasse models have remained fundamentally unchanged over this time. In the past decade, however, multidimensional and transient formulations of the continuum damage mechanics approach to simulating ice fracture have emerged. The combination of employing damage mechanics to represent slow upstream deterioration of ice strength and fracture mechanics to represent rapid failure at downstream termini holds promise for implementation in large-scale ice sheet models. Finally, given the broad interest in the sea level rise implications of recent and future cryospheric change, we provide a synthesis of 10 mechanisms by which crevasses can influence glacier mass balance.
Biogeochemical mass balances in a turbid tropical reservoir. Field data and modelling approach
NASA Astrophysics Data System (ADS)
Phuong Doan, Thuy Kim; Némery, Julien; Gratiot, Nicolas; Schmid, Martin
2014-05-01
The turbid tropical Cointzio reservoir, located in the Trans Mexican Volcanic Belt (TMVB), behaves as a warm monomictic water body (area = 6 km2, capacity 66 Mm3, residence time ~ 1 year). It is strategic for the drinking water supply of the city of Morelia, capital of the state of Michoacán, and for downstream irrigation during the dry season. This reservoir is a perfect example of a human-impacted system since its watershed is mainly composed of degraded volcanic soils and is subjected to high erosion processes and agricultural loss. The reservoir is threatened by sediment accumulation and nutrients originating from untreated waters in the upstream watershed. The high content of very fine clay particles and the lack of water treatment plants lead to serious episodes of eutrophication (up to 70 μg chl. a L-1), high levels of turbidity (Secchi depth < 30 cm) and a long period of anoxia (from May to October). Based on intensive field measurements in 2009 (deposited sediment, benthic chamber, water vertical profiles, reservoir inflow and outflow) we determined suspended sediment (SS), carbon (C), nitrogen (N) and phosphorus (P) mass balances. Watershed SS yields were estimated at 35 t km2 y-1 of which 89-92 % were trapped in the Cointzio reservoir. As a consequence the reservoir has already lost 25 % of its initial storage capacity since its construction in 1940. Nutrient mass balances showed that 50 % and 46 % of incoming P and N were retained by sedimentation, and mainly eliminated through denitrification respectively. Removal of C by 30 % was also observed both by sedimentation and through gas emission. To complete field data analyses we examined the ability of vertical one dimensional (1DV) numerical models (Aquasim biogeochemical model coupled with k-ɛ mixing model) to reproduce the main biogeochemical cycles in the Cointzio reservoir. The model can describe all the mineralization processes both in the water column and in the sediment. The values of the
Biological Productivity from an Oxygen Mass Balance in the subarctic North Pacific
NASA Astrophysics Data System (ADS)
Giesbrecht, K. E.; Hamme, R. C.
2008-12-01
Biological productivity is an important process controlling the export of carbon into the deep ocean and thus influencing the earth's climate. An O2 mass balance of the upper ocean can estimate this export of organic carbon if the physical processes affecting the O2 concentrations are accounted for. This can be accomplished by measuring the dissolved O2/Ar ratio, because their similar physical properties allow us to consider Ar an 'abiotic' O2 analogue. Here we present a two-year data set of O2/N2/Ar ratio measurements collected at Station Papa and along Line P in 2007/08. Line P, situated in the subarctic North Pacific, is a series of oceanographic stations running from the southwest tip of Vancouver Island to Station Papa (50°N, 145°W), one of the oldest deep-ocean time series in existence which is located in the High-Nutrient/Low-Chlorophyll (HNLC) region of the subarctic gyre. Current cruises along Line P run three times per year, typically in February, June and August. The dissolved gas ratios are measured using a stable isotope mass spectrometer and oxygen concentrations by titration. In a simple steady state, we equate biological O2 production to diffusive gas exchange, using the O2/Ar ratio to normalize the physical component of the oxygen signal and calculate the net biological oxygen production. Diffusive gas exchange is calculated using a wind speed parameterization. Preliminary estimates of the net biological production in the mixed layer at Station Papa for 2007 are calculated at 30.9 and 14.0 mmol C m-2 d- 1 for June and August respectively, both exhibiting mixed layer O2/Ar supersaturations. The O2/Ar undersaturation in the mixed layer for February 2007 suggests net respiration at that time. The wind speed parameterization of diffusive gas exchange is the major source of error for this method. We plan to refine our productivity calculation to account for vertical mixing and also by measuring rates of production using a number of different methods
Changes in nutrient mass balances over time and related drivers for 54 New York State dairy farms.
Soberon, Melanie A; Cela, Sebastian; Ketterings, Quirine M; Rasmussen, Caroline N; Czymmek, Karl J
2015-08-01
Whole-farm nutrient mass balances (NMB) can assist producers in evaluation and monitoring the nutrient status of dairy farms over time. Most of the previous studies that report NMB for dairy farms were conducted over 1 to 3 yr. In this study, annual N, P, and K mass balances were assessed on 54 dairy farms in New York State for 4 to 6 yr between 2005 and 2010 with the objectives to (1) document changes in NMB over time and drivers for change, and (2) identify nutrient use efficiency parameters that predicted the potential for improvement in NMB. The study farms varied in size (42 small, 12 medium and large) and management practices. Phosphorus, K, and 2 N balances (N1 without N2 fixation, and N2 including N2 fixation) were calculated. In general, farms with high initial NMB levels reduced them over time whereas farms with negative NMB tended to increase their NMB, demonstrating a tendency across all farms to move toward more optimal NMB levels over time. Sixty-three to 76% of farms (depending on the nutrient) reduced their NMB per hectare over the 4 to 6 yr, and 55 to 61% of these farms were able to do so while increasing milk production per cow. Across all farms, the overall reduction in NMB per hectare averaged -22kg of N/ha for N1 (29% reduction), -16kg of N/ha for N2 (15% reduction), -4kg of P/ha (36% reduction), and -10kg of K/ha (29% reduction). Change in feed imports was the most important driver for change in N and P balances across farms, whereas adjustments in both feed and fertilizer imports affected the K balances. Key predictors of potential areas for improvement in NMB over time include total nutrient imports, feed imports, animal density, percentage of farm-produced feed and nutrients, and feed nutrient use efficiency. Overall, this study highlights the opportunities of an adaptive management approach that includes NMB assessments to evaluate and monitor changes in nutrient use efficiency and cost-efficiency over time. Copyright © 2015 American
The Parent Magmas of the Cumulate Eucrites: A Mass Balance Approach
NASA Technical Reports Server (NTRS)
Treiman, Allan H.
1996-01-01
The cumulate eucrite meteorites are gabbros that are related to the eucrite basalt meteorites. The eucrite basalts are relatively primitive (nearly flat REE patterns with La approx. 8-30 x CI), but the parent magmas of the cumulate eucrites have been inferred as extremely evolved (La to greater than 100 x CI). This inference has been based on mineral/magma partitioning, and on mass balance considering the cumulate eucrites as adcumulates of plagioclase + pigeonite only; both approaches have been criticized as inappropriate. Here, mass balance including magma + equilibrium pigeonite + equilibrium plagiociase is used to test a simple model for the cumulate eucrites: that they formed from known eucritic magma types, that they consisted only of magma + crystals in chemical equilibrium with the magma, and that they were closed to chemical exchange after the accumulation of crystals. This model is tested for major and Rare Earth Elements (REE). The cumulate eucrites Serra de Mage and Moore County are consistent, in both REE and major elements, with formation by this simple model from a eucrite magma with a composition similar to the Nuevo Laredo meteorite: Serra de Mage as 14% magma, 47.5% pigeonite, and 38.5% plagioclase; Moore County as 35% magma, 37.5% pigeonite, and 27.5% plagioclase. These results are insensitive to the choice of mineral/magma partition coefficients. Results for the Moama cumulate eucrite are strongly dependent on choice of partition coefficients; for one reasonable choice, Moama's composition can be modeled as 4% Nuevo Laredo magma, 60% pigeonite, and 36% plagioclase. Selection of parent magma composition relies heavily on major elements; the REE cannot uniquely indicate a parent magma among the eucrite basalts. The major element composition of Y-791195 can be fit adequately as a simple cumulate from any basaltic eucrite composition. However, Y-791195 has LREE abundances and La/Lu too low to be accommodated within the model using any basaltic
ERIC Educational Resources Information Center
Yang, Allen H. J.; Dimiduk, Kathryn; Daniel, Susan
2011-01-01
We present a simplified human alcohol metabolism model for a mass balance team project. Students explore aspects of engineering in biotechnology: designing/modeling biological systems, testing the design/model, evaluating new conditions, and exploring cutting-edge "lab-on-a-chip" research. This project highlights chemical engineering's impact on…
The recycling of heavy-metalcontaining wastes: Mass balances and economical estimations
NASA Astrophysics Data System (ADS)
Antrekowitsch, J.; Steinlechner, S.
2011-01-01
As environmental legislation has become stricter in recent decades, efforts for treating residues have also increased. The existing pyrometallurgical reprocessing methods for metal-containing wastes recover mainly only one valuable metal or produce low-grade byproducts. The aim of developing an economic process has to be the simultaneous recovery of more than one valuable metal and increased product quality. In the case of zinccontaining residues the goal has to be a high-quality zinc product. Moreover, the target is a nearly zero waste process and, accordingly, small amounts of generated residues. In this paper four possible secondary raw materials are compared regarding their mass and energy balance for a treatment in a carbon-containing metal bath. Furthermore, an evaluation of the economy is given for a neutral leaching residue, Waelz kiln slag, dust from secondary copper industry as well as an electro arc furnace dust from carbon steel production.
Banks, Charles J; Chesshire, Michael; Heaven, Sonia; Arnold, Rebecca
2011-01-01
An anaerobic digester receiving food waste collected mainly from domestic kitchens was monitored over a period of 426 days. During this time information was gathered on the waste input material, the biogas production, and the digestate characteristics. A mass balance accounted for over 90% of the material entering the plant leaving as gaseous or digestate products. A comprehensive energy balance for the same period showed that for each tonne of input material the potential recoverable energy was 405 kWh. Biogas production in the digester was stable at 642 m3 tonne(-1) VS added with a methane content of around 62%. The nitrogen in the food waste input was on average 8.9 kg tonne(-1). This led to a high ammonia concentration in the digester which may have been responsible for the accumulation of volatile fatty acids that was also observed. Copyright © 2010 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Sharma, P.; Ramanathan, A.; Linda, A.; Wagnon, P.; Arnod, Y.; Jose, P. G.; Chevallier, P.
2009-04-01
The Mass Balance of the Chhota Shigri glacier (32.2°N, 77.5°E; 15.7 km2, 4050 to 6263m a.m.s.l., 9 km long) located in Lahaul and Spiti valley, Himachal Pradesh, India has been monitored from 2002 to 2008 using glaciological method. In 2008, an additional field survey during 3- 10th August was undertaken to understand the impact of monsoonal rainfall on specific mass balance at various points on the ablation zone of this glacier that is alternatively influenced by the Indian monsoon and the mid-latitude westerlies. Specific Annual Mass Balance is negative (0.93 mweq), Equilibrium Line Altitude (ELA) is 5120m and Accumulation Area Ratio (AAR) is 38% in the 2007-08 hydrological year. In 2008 data obtained from nearest Weather station at Keylong show that the monsoon hit the Spiti valley in the middle of June (15 days earlier than normal date ) .The results reveal that 70% of total specific mass balance occurred by the first week of August indicating that most of the melting occurred in the first half of ablation season, dominated by monsoonal rainfall. The rainfall may accelerate ablation rate by supplying ( heat ) energy even it is very low and exposing bare dirty ice thereby decreasing albedo. In part A of the glacier, the mean vertical gradient of ablation up to August 08 is 0.67 m w.e. 100 m-1 between 4350 and 4850 m a.s.l., (area free of debris) and for part B, it is 0.41 m w.e. 100 m-1 between 4600m a.s.l. and 5000m a.s.l. From August 08 up to 1st week of October, mean vertical gradient of the ablation for part A is 0.54m w.e. 100 m-1 and it is 0.61 m w.e. 100 m-1 in part B for the same altitude ranges. Below 4350m a.s.l. the whole glacier is covered by debris and the melting rate is significantly reduced. Overall, ablation rate is influenced by rainfall, incoming solar radiation and debris cover.
NASA Astrophysics Data System (ADS)
Shean, David E.; Christianson, Knut; Larson, Kristine M.; Ligtenberg, Stefan R. M.; Joughin, Ian R.; Smith, Ben E.; Stevens, C. Max; Bushuk, Mitchell; Holland, David M.
2017-11-01
In the last 2 decades, Pine Island Glacier (PIG) experienced marked speedup, thinning, and grounding-line retreat, likely due to marine ice-sheet instability and ice-shelf basal melt. To better understand these processes, we combined 2008-2010 and 2012-2014 GPS records with dynamic firn model output to constrain local surface and basal mass balance for PIG. We used GPS interferometric reflectometry to precisely measure absolute surface elevation (zsurf) and Lagrangian surface elevation change (Dzsurf/ Dt). Observed surface elevation relative to a firn layer tracer for the initial surface (zsurf - zsurf0') is consistent with model estimates of surface mass balance (SMB, primarily snow accumulation). A relatively abrupt ˜ 0.2-0.3 m surface elevation decrease, likely due to surface melt and increased compaction rates, is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed Dzsurf/ Dt trends (-1 to -4 m yr-1) for the PIG shelf sites are all highly linear. Corresponding basal melt rate estimates range from ˜ 10 to 40 m yr-1, in good agreement with those derived from ice-bottom acoustic ranging, phase-sensitive ice-penetrating radar, and high-resolution stereo digital elevation model (DEM) records. The GPS and DEM records document higher melt rates within and near features associated with longitudinal extension (i.e., transverse surface depressions, rifts). Basal melt rates for the 2012-2014 period show limited temporal variability despite large changes in ocean temperature recorded by moorings in Pine Island Bay. Our results demonstrate the value of long-term GPS records for ice-shelf mass balance studies, with implications for the sensitivity of ice-ocean interaction at PIG.
Using bioprocess stoichiometry to build a plant-wide mass balance based steady-state WWTP model.
Ekama, G A
2009-05-01
Steady-state models are useful for design of wastewater treatment plants (WWTPs) because they allow reactor sizes and interconnecting flows to be simply determined from explicit equations in terms of unit operation performance criteria. Once the overall WWTP scheme is established and the main system defining parameters of the individual unit operations estimated, dynamic models can be applied to the connected unit operations to refine their design and evaluate their performance under dynamic flow and load conditions. To model anaerobic digestion (AD) within plant-wide WWTP models, not only COD and nitrogen (N) but also carbon (C) fluxes entering the AD need to be defined. Current plant-wide models, like benchmark simulation model No 2 (BSM2), impose a C flux at the AD influent. In this paper, the COD and N mass balance steady-state models of activated sludge (AS) organics degradation, nitrification and denitrification (ND) and anaerobic (AD) and aerobic (AerD) digestion of wastewater sludge are extended and linked with bioprocess transformation stoichiometry to form C, H, O, N, chemical oxygen demand (COD) and charge mass balance based models so that also C (and H and O) can be tracked through the whole WWTP. By assigning a stoichiometric composition (x, y, z and a in C(x)H(y)O(z)N(a)) to each of the five main influent wastewater organic fractions and ammonia, these, and the products generated from them via the biological processes, are tracked through the WWTP. The model is applied to two theoretical case study WWTPs treating the same raw wastewater (WW) to the same final sludge residual biodegradable COD. It is demonstrated that much useful information can be generated with the relatively simple steady-state models to aid WWTP layout design and track the different products exiting the WWTP via the solid, liquid and gas streams, such as aerobic versus anaerobic digestion of waste activated sludge, N loads in recycle streams, methane production for energy recovery
Fe and Cu isotope mass balances in the human body
NASA Astrophysics Data System (ADS)
Balter, V.; Albarede, F.; Jaouen, K.
2011-12-01
The ranges of the Fe and Cu isotope compositions in the human body are large, i.e. ~3% and ~2%, respectively. Both isotopic fractionations appear to be mainly controlled by redox conditions. The Fe and Cu isotope compositions of the tissues analyzed so far plot on a mixing hyperbolae between a reduced and an oxidized metals pools. The reduced metals pool is composed by erythrocytes, where Fe is bounded to hemoglobin as Fe(II) and Cu to superoxide-dismutase as Cu(I). The oxidized metals pool is composed by hepatocytes, where Fe and Cu are stored as Fe(III) ferritin and as Cu(II) ceruloplasmine, respectively. The position of each biological component in the δ56Fe-δ65Cu diagram therefore reflects the oxidation state of Fe and Cu of the predominant metal carrier protein and allows to quantify Fe and Cu fluxes between organs using mass balance calculations. For instance, serum and clot Fe and Cu isotope compositions show that current biological models of erythropoiesis violates mass conservation requirements, and suggest hidden Fe and Cu pathways during red blood cells synthesis. The results also show that a coupled Fe-Cu strong gender isotopic effect is observed in various organs. The isotopic difference between men and women is unlikely to be due to differential dietary uptake or endometrium loss, but rather reflects the effect of menstrual losses and a correlative solicitation of hepatic stores. We speculate that thorough studies of the metabolism of stable isotopes in normal conditions is a prerequisite for the understanding of the pathological dysregulations.
Aqueous gradient by balancing diffusive and convective mass transport (Conference Presentation)
NASA Astrophysics Data System (ADS)
Habhab, Mohammed-Baker I.; Ismail, Tania; Lo, Joe F.; Haque, Arefa
2016-03-01
In wounds, cells secret biomolecules such as vascular endothelial growth factor (VEGF), a protein that controls many processes in healing. VEGF protein is expressed in a gradient in tissue, and its shape will be affected by the tissue injury sustained during wounding. In order to study the responses of keratinocyte cell migration to VEGF gradients and the geometric factors on wound healing, we designed a microfluidic gradient device that can generate large area gradients (1.5 cm in diameter) capable of mimicking arbitrary wound shapes. Microfluidic devices offer novel techniques to address biological and biomedical issues. Different from other gradient microfluidics, our device balances diffusion of biomolecules versus the convective clearance by a buffer flow on the opposite ends of the gradient. This allows us to create a large area gradient within shorter time scales by actively driving mass transport. In addition, the microfluidic device makes use of a porous filter membrane to create this balance as well as to deliver the resulting gradient to a culture of cells. The culture of cells are seeded above the gradient in a gasket chamber. However, Keratinocytes do not migrate effectively on filter paper. Therefore, in order to improve the motility of cells on the surface, we coated the filter paper with a 30m thick layer of gelatin type B. after observation under the microscope we found that the gelatin coated sample showed cells with more spread out morphology, with 97% viability, suggesting better adhesion than the non-coated sample.
Overview and Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992-2009
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Giovinetto, Mario B.
2011-01-01
Mass balance estimates for the Antarctic Ice Sheet (AIS) in the 2007 report by the Intergovernmental Panel on Climate Change and in more recent reports lie between approximately ?50 to -250 Gt/year for 1992 to 2009. The 300 Gt/year range is approximately 15% of the annual mass input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (?28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. We also modify the IOM estimate using (1) an alternate extrapolation to estimate the discharge from the non-observed 15% of the periphery, and (2) substitution of input from a field data compilation for input from an atmospheric model in 6% of area. The modified IOM estimate reduces the loss from 136 Gt/year to 13 Gt/year. Two ERS-based estimates, the modified IOM, and a GRACE-based estimate for observations within 1992 2005 lie in a narrowed range of ?27 to -40 Gt/year, which is about 3% of the annual mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992 2001 is -47 Gt/year for West Antarctica, ?16 Gt/year for East Antarctica, and -31 Gt/year overall (?0.1 mm/year SLE), not including part of the Antarctic Peninsula (1.07% of the AIS area). Although recent reports of large and increasing rates of mass loss with time from GRACE-based studies cite agreement with IOM results, our evaluation does not support that conclusion
A mass balance approach to investigate arsenic cycling in a petroleum plume
Ziegler, Brady A.; Schreiber, Madeline E.; Cozzarelli, Isabelle M.; Ng. G.-H. Crystal,
2017-01-01
Natural attenuation of organic contaminants in groundwater can give rise to a series of complex biogeochemical reactions that release secondary contaminants to groundwater. In a crude oil contaminated aquifer, biodegradation of petroleum hydrocarbons is coupled with the reduction of ferric iron (Fe(III)) hydroxides in aquifer sediments. As a result, naturally occurring arsenic (As) adsorbed to Fe(III) hydroxides in the aquifer sediment is mobilized from sediment into groundwater. However, Fe(III) in sediment of other zones of the aquifer has the capacity to attenuate dissolved As via resorption. In order to better evaluate how long-term biodegradation coupled with Fe-reduction and As mobilization can redistribute As mass in contaminated aquifer, we quantified mass partitioning of Fe and As in the aquifer based on field observation data. Results show that Fe and As are spatially correlated in both groundwater and aquifer sediments. Mass partitioning calculations demonstrate that 99.9% of Fe and 99.5% of As are associated with aquifer sediment. The sediments act as both sources and sinks for As, depending on the redox conditions in the aquifer. Calculations reveal that at least 78% of the original As in sediment near the oil has been mobilized into groundwater over the 35-year lifespan of the plume. However, the calculations also show that only a small percentage of As (∼0.5%) remains in groundwater, due to resorption onto sediment. At the leading edge of the plume, where groundwater is suboxic, sediments sequester Fe and As, causing As to accumulate to concentrations 5.6 times greater than background concentrations. Current As sinks can serve as future sources of As as the plume evolves over time. The mass balance approach used in this study can be applied to As cycling in other aquifers where groundwater As results from biodegradation of an organic carbon point source coupled with Fe reduction.
Jung, HoHyun; Chun, Keyoung Jin; Hong, Jaesoo; Lim, Dohyung
2015-01-01
Balance is important in daily activities and essential for maintaining an independent lifestyle in the elderly. Recent studies have shown that balance rehabilitation training can improve the balance ability of the elderly, and diverse balance rehabilitation training equipment has been developed. However, there has been little research into optimized strategies for balance rehabilitation training. To provide an optimized strategy, we analyzed the balance characteristics of participants in response to the rotation of a base plate on multiple axes. Seven male adults with no musculoskeletal or nervous system-related diseases (age: 25.5±1.7 years; height: 173.9±6.4 cm; body mass: 71.3±6.5 kg; body mass index: 23.6±2.4 kg/m2) were selected to investigate the balance rehabilitation training using customized rehabilitation equipment. Rotation of the base plate of the equipment was controlled to induce dynamic rotation of participants in the anterior–posterior, right-diagonal, medial–lateral, and left-diagonal directions. We used a three-dimensional motion capture system employing infrared cameras and the Pedar Flexible Insoles System to characterize the major lower-extremity joint angles, center of body mass, and center of pressure. We found statistically significant differences between the changes in joint angles in the lower extremities in response to dynamic rotation of the participants (P<0.05). The maximum was greater with anterior–posterior and medial–lateral dynamic rotation than with that in other directions (P<0.05). However, there were no statistically significant differences in the frequency of center of body mass deviations from the base of support (P>0.05). These results indicate that optimizing rotation control of the base plate of balance rehabilitation training equipment to induce anterior–posterior and medial–lateral dynamic rotation preferentially can lead to effective balance training. Additional tests with varied speeds and ranges of
Kato, Kota; Hale, Christine; Kowalski, Donna; Lademacher, Christopher; Yamazaki, Takao; Akhtar, Shahzad; Desai, Amit
2017-01-01
Abstract Isavuconazonium sulfate is the water‐soluble prodrug of the active triazole isavuconazole. Two phase 1 studies were conducted to identify the metabolic profile and mass balance of isavuconazole and BAL8728 (inactive cleavage product). Seven subjects in study 1 (isavuconazole mass balance) received a single oral dose of [cyano‐14C]isavuconazonium sulfate corresponding to 200 mg isavuconazole. Six subjects in study 2 (BAL8728 mass balance) received a single intravenous dose of [pyridinylmethyl‐14C]isavuconazonium sulfate corresponding to 75 mg BAL8728. Pharmacokinetic parameters of radioactivity in whole blood and plasma and of isavuconazole and BAL8728 in plasma were assessed. Radioactivity ratio of blood/plasma, percentage of dose, and cumulative percentage of radioactive dose recovered in urine and feces for isavuconazole and BAL8728 were assessed. Metabolic profiling was carried out by high‐performance liquid chromatography and mass spectrometry. Mean plasma isavuconazole pharmacokinetic parameters included apparent clearance (2.3 ± 0.7 L/h), apparent volume of distribution (301.8 ± 105.7 L), and terminal elimination half‐life (99.9 ± 44.6 hours). In study 1, isavuconazole‐derived radioactivity was recovered approximately equally in urine and feces (46.1% and 45.5%, respectively). In study 2, BAL8728‐derived radioactivity was predominantly recovered in urine (96.0%). Isavuconazole (study 1) and M4 (cleavage metabolite of BAL8728; study 2) were the predominant circulating components of radioactivity in plasma. PMID:28750160
Zuo, Xiaojun; Fu, Dafang; Li, He
2012-11-01
Heavy metal pollution in road runoff had caused widespread concern since the last century. However, there are little references on metal speciation in multiple environmental media (e.g., rain, road sediments, and road runoff). Our research targeted the investigation of metal speciation in rain, road sediments, and runoff; the analysis of speciation variation and mass balance of metals among rain, road sediments, and runoff; the selection of main factors by principal component analysis (PCA); and the establishment of equation to evaluate the impact of rain and road sediments to metals in road runoff. Sequential extraction procedure contains five steps for the chemical fractionation of metals. Flame atomic absorption spectrometry (Shimadzu, AA-6800) was used to determine metal speciation concentration, as well as the total and dissolved fractions. The dissolved fractions for both Cu and Zn were dominant in rain. The speciation distribution of Zn was different from that of Cu in road sediments, while speciation distribution of Zn is similar to that of Cu in runoff. The bound to carbonates for both Cu and Zn in road sediments were prone to be dissolved by rain. The levels of Cu and Zn in runoff were not obviously influenced by rain, but significantly influenced by road sediments. The masses for both Cu and Zn among rain, road sediments, and road runoff approximately meet the mass balance equation for all rainfall patterns. Five principal factors were selected for metal regression equation based on PCA, including rainfall, average rainfall intensity, antecedent dry periods, total suspended particles, and temperature. The established regression equations could be used to predict the effect of road runoff on receiving environments.
A high-resolution dissolved oxygen mass balance model was developed for the Louisiana coastal shelf in the northern Gulf of Mexico. GoMDOM (Gulf of Mexico Dissolved Oxygen Model) was developed to assist in evaluating the impacts of nutrient loading on hypoxia development and exte...
In order to develop effective strategies for toxics management, the Great Lakes National Program Office (GLNPO) of the United States Environmental Protection Agency (U.S. EPA), in 1994, launched an ambitious five year program to conduct a mass balance study of selected toxics p...
Fahrenfeld, Nicole; Knowlton, Katharine; Krometis, Leigh Anne; Hession, W Cully; Xia, Kang; Lipscomb, Emily; Libuit, Kevin; Green, Breanna Lee; Pruden, Amy
2014-01-01
The development of models for understanding antibiotic resistance gene (ARG) persistence and transport is a critical next step toward informing mitigation strategies to prevent the spread of antibiotic resistance in the environment. A field study was performed that used a mass balance approach to gain insight into the transport and dissipation of ARGs following land application of manure. Soil from a small drainage plot including a manure application site, an unmanured control site, and an adjacent stream and buffer zone were sampled for ARGs and metals before and after application of dairy manure slurry and a dry stack mixture of equine, bovine, and ovine manure. Results of mass balance suggest growth of bacterial hosts containing ARGs and/or horizontal gene transfer immediately following slurry application with respect to ermF, sul1, and sul2 and following a lag (13 days) for dry-stack-amended soils. Generally no effects on tet(G), tet(O), or tet(W) soil concentrations were observed despite the presence of these genes in applied manure. Dissipation rates were fastest for ermF in slurry-treated soils (logarithmic decay coefficient of -3.5) and for sul1 and sul2 in dry-stack-amended soils (logarithmic decay coefficients of -0.54 and -0.48, respectively), and evidence for surface and subsurface transport was not observed. Results provide a mass balance approach for tracking ARG fate and insights to inform modeling and limiting the transport of manure-borne ARGs to neighboring surface water.
A mass-balance model to separate and quantify colloidal and solute redistributions in soil
Bern, C.R.; Chadwick, O.A.; Hartshorn, A.S.; Khomo, L.M.; Chorover, J.
2011-01-01
Studies of weathering and pedogenesis have long used calculations based upon low solubility index elements to determine mass gains and losses in open systems. One of the questions currently unanswered in these settings is the degree to which mass is transferred in solution (solutes) versus suspension (colloids). Here we show that differential mobility of the low solubility, high field strength (HFS) elements Ti and Zr can trace colloidal redistribution, and we present a model for distinguishing between mass transfer in suspension and solution. The model is tested on a well-differentiated granitic catena located in Kruger National Park, South Africa. Ti and Zr ratios from parent material, soil and colloidal material are substituted into a mixing equation to quantify colloidal movement. The results show zones of both colloid removal and augmentation along the catena. Colloidal losses of 110kgm-2 (-5% relative to parent material) are calculated for one eluviated soil profile. A downslope illuviated profile has gained 169kgm-2 (10%) colloidal material. Elemental losses by mobilization in true solution are ubiquitous across the catena, even in zones of colloidal accumulation, and range from 1418kgm-2 (-46%) for an eluviated profile to 195kgm-2 (-23%) at the bottom of the catena. Quantification of simultaneous mass transfers in solution and suspension provide greater specificity on processes within soils and across hillslopes. Additionally, because colloids include both HFS and other elements, the ability to quantify their redistribution has implications for standard calculations of soil mass balances using such index elements. ?? 2011.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, Woohyun; Braun, J.
Refrigerant mass flow rate is an important measurement for monitoring equipment performance and enabling fault detection and diagnostics. However, a traditional mass flow meter is expensive to purchase and install. A virtual refrigerant mass flow sensor (VRMF) uses a mathematical model to estimate flow rate using low-cost measurements and can potentially be implemented at low cost. This study evaluates three VRMFs for estimating refrigerant mass flow rate. The first model uses a compressor map that relates refrigerant flow rate to measurements of inlet and outlet pressure, and inlet temperature measurements. The second model uses an energy-balance method on the compressormore » that uses a compressor map for power consumption, which is relatively independent of compressor faults that influence mass flow rate. The third model is developed using an empirical correlation for an electronic expansion valve (EEV) based on an orifice equation. The three VRMFs are shown to work well in estimating refrigerant mass flow rate for various systems under fault-free conditions with less than 5% RMS error. Each of the three mass flow rate estimates can be utilized to diagnose and track the following faults: 1) loss of compressor performance, 2) fouled condenser or evaporator filter, 3) faulty expansion device, respectively. For example, a compressor refrigerant flow map model only provides an accurate estimation when the compressor operates normally. When a compressor is not delivering the expected flow due to a leaky suction or discharge valve or other internal fault, the energy-balance or EEV model can provide accurate flow estimates. In this paper, the flow differences provide an indication of loss of compressor performance and can be used for fault detection and diagnostics.« less
NASA Astrophysics Data System (ADS)
Hardesty, R.; Brewer, A.; Banta, R. M.; Senff, C. J.; Sandberg, S. P.; Alvarez, R. J.; Weickmann, A. M.; Sweeney, C.; Karion, A.; Petron, G.; Frost, G. J.; Trainer, M.
2012-12-01
Aircraft-based mass balance approaches are often used to estimate greenhouse gas emissions from distributed sources such as urban areas and oil and gas fields. A scanning Doppler lidar, which measures range-resolved wind and aerosol backscatter information, can provide important information on mixing and transport processes in the planetary boundary layer for these studies. As part of the Uintah Basin Winter Ozone Study, we deployed a high resolution Doppler lidar to characterize winds and turbulence, atmospheric mixing, and mixing layer depth in the oil and gas fields near Vernal, Utah. The lidar observations showed evolution of the horizontal wind field, vertical mixing and aerosol structure for each day during the 5-week deployment. This information was used in conjunction with airborne in situ observations of methane and carbon dioxide to compute methane fluxes and estimate basin-wide methane emissions. A similar experiment incorporating a lidar along with a radar wind profiler and instrumented aircraft was subsequently carried out in the vicinity of the Denver-Julesburg Basin in Colorado. Using examples from these two studies we discuss the use of Doppler lidar in conjunction with other sources of wind information and boundary layer structure for mass-balance type studies. Plans for a one-year deployment of a Doppler lidar as part of the Indianapolis Flux experiment to estimate urban-scale greenhouse gas emissions near are also presented.
NASA Astrophysics Data System (ADS)
Alves, Gelio; Wang, Guanghui; Ogurtsov, Aleksey Y.; Drake, Steven K.; Gucek, Marjan; Sacks, David B.; Yu, Yi-Kuo
2018-06-01
Rapid and accurate identification and classification of microorganisms is of paramount importance to public health and safety. With the advance of mass spectrometry (MS) technology, the speed of identification can be greatly improved. However, the increasing number of microbes sequenced is complicating correct microbial identification even in a simple sample due to the large number of candidates present. To properly untwine candidate microbes in samples containing one or more microbes, one needs to go beyond apparent morphology or simple "fingerprinting"; to correctly prioritize the candidate microbes, one needs to have accurate statistical significance in microbial identification. We meet these challenges by using peptide-centric representations of microbes to better separate them and by augmenting our earlier analysis method that yields accurate statistical significance. Here, we present an updated analysis workflow that uses tandem MS (MS/MS) spectra for microbial identification or classification. We have demonstrated, using 226 MS/MS publicly available data files (each containing from 2500 to nearly 100,000 MS/MS spectra) and 4000 additional MS/MS data files, that the updated workflow can correctly identify multiple microbes at the genus and often the species level for samples containing more than one microbe. We have also shown that the proposed workflow computes accurate statistical significances, i.e., E values for identified peptides and unified E values for identified microbes. Our updated analysis workflow MiCId, a freely available software for Microorganism Classification and Identification, is available for download at https://www.ncbi.nlm.nih.gov/CBBresearch/Yu/downloads.html.
Alves, Gelio; Wang, Guanghui; Ogurtsov, Aleksey Y; Drake, Steven K; Gucek, Marjan; Sacks, David B; Yu, Yi-Kuo
2018-06-05
Rapid and accurate identification and classification of microorganisms is of paramount importance to public health and safety. With the advance of mass spectrometry (MS) technology, the speed of identification can be greatly improved. However, the increasing number of microbes sequenced is complicating correct microbial identification even in a simple sample due to the large number of candidates present. To properly untwine candidate microbes in samples containing one or more microbes, one needs to go beyond apparent morphology or simple "fingerprinting"; to correctly prioritize the candidate microbes, one needs to have accurate statistical significance in microbial identification. We meet these challenges by using peptide-centric representations of microbes to better separate them and by augmenting our earlier analysis method that yields accurate statistical significance. Here, we present an updated analysis workflow that uses tandem MS (MS/MS) spectra for microbial identification or classification. We have demonstrated, using 226 MS/MS publicly available data files (each containing from 2500 to nearly 100,000 MS/MS spectra) and 4000 additional MS/MS data files, that the updated workflow can correctly identify multiple microbes at the genus and often the species level for samples containing more than one microbe. We have also shown that the proposed workflow computes accurate statistical significances, i.e., E values for identified peptides and unified E values for identified microbes. Our updated analysis workflow MiCId, a freely available software for Microorganism Classification and Identification, is available for download at https://www.ncbi.nlm.nih.gov/CBBresearch/Yu/downloads.html . Graphical Abstract ᅟ.
The Lake Michigan Mass Balance Project (LMMBP) is a part of the Enhanced Monitoring Plan (EMP) for Lake Michigan (McCarty, et al., 2006). PCBs (polychlorinated biphenyls) were one of the targeted pollutants studied in the project. As one of the components in the overall LMMBP mod...
NASA Astrophysics Data System (ADS)
Kittel, Christoph; Lang, Charlotte; Agosta, Cécile; Prignon, Maxime; Fettweis, Xavier; Erpicum, Michel
2016-04-01
This study presents surface mass balance (SMB) results at 5 km resolution with the regional climate MAR model over the Greenland ice sheet. Here, we use the last MAR version (v3.6) where the land-ice module (SISVAT) using a high resolution grid (5km) for surface variables is fully coupled while the MAR atmospheric module running at a lower resolution of 10km. This online downscaling technique enables to correct near-surface temperature and humidity from MAR by a gradient based on elevation before forcing SISVAT. The 10 km precipitation is not corrected. Corrections are stronger over the ablation zone where topography presents more variations. The model has been force by ERA-Interim between 1979 and 2014. We will show the advantages of using an online SMB downscaling technique in respect to an offline downscaling extrapolation based on local SMB vertical gradients. Results at 5 km show a better agreement with the PROMICE surface mass balance data base than the extrapolated 10 km MAR SMB results.
Booth, D.B.
1986-01-01
An estimate of the sliding velocity and basal meltwater discharge of the Puget lobe of the Cordilleran ice sheet can be calculated from its reconstructed extent, altitude, and mass balance. Lobe dimensions and surface altitudes are inferred from ice limits and flow-direction indicators. Net annual mass balance and total ablation are calculated from relations empirically derived from modern maritime glaciers. An equilibrium-line altitude between 1200 and 1250 m is calculated for the maximum glacial advance (ca. 15,000 yr B.P.) during the Vashon Stade of the Fraser Glaciation. This estimate is in accord with geologic data and is insensitive to plausible variability in the parameters used in the reconstruction. Resultant sliding velocities are as much as 650 m/a at the equilibrium line, decreasing both up- and downglacier. Such velocities for an ice sheet of this size are consistent with nonsurging behavior. Average meltwater discharge increases monotonically downglacier to 3000 m3/sec at the terminus and is of a comparable magnitude to ice discharge over much of the glacier's ablation area. Palcoclimatic inferences derived from this reconstruction are consistent with previous, independently derived studies of late Pleistocene temperature and precipitation in the Pacific Northwest. ?? 1986.
Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900.
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
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
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dyer, J. A.
In preparation for the next revision of the E-Area Low-Level Waste Facility (LLWF) Performance Assessment (PA), a mass balance model was developed in Microsoft Excel to confirm correct implementation of intact- and subsided-area infiltration profiles for the proposed closure cap in the PORFLOW vadose-zone model. The infiltration profiles are based on the results of Hydrologic Evaluation of Landfill Performance (HELP) model simulations for both intact and subsided cases.
Besil, Natalia; Uclés, Samanta; Mezcúa, Milagros; Heinzen, Horacio; Fernández-Alba, Amadeo R
2015-08-01
Gas chromatography coupled to high resolution hybrid quadrupole time-of-flight mass spectrometry (GC-QTOF MS), operating in negative chemical ionization (NCI) mode and combining full scan with MSMS experiments using accurate mass analysis, has been explored for the automated determination of pesticide residues in fruit and vegetables. Seventy compounds were included in this approach where 50 % of them are not approved by the EU legislation. A global 76 % of the analytes could be identified at 1 μg kg(-1). Recovery studies were developed at three concentration levels (1, 5, and 10 μg kg(-1)). Seventy-seven percent of the detected pesticides at the lowest level yielded recoveries within the 70 %-120 % range, whereas 94 % could be quantified at 5 μg kg(-1), and the 100 % were determined at 10 μg kg(-1). Good repeatability, expressed as relative standard deviation (RSD <20 %), was obtained for all compounds. The main drawback of the method was the limited dynamic range that was observed for some analytes that can be overcome either diluting the sample or lowering the injection volume. A home-made database was developed and applied to an automatic accurate mass data processing. Measured mass accuracies of the generated ions were mainly less than 5 ppm for at least one diagnostic ion. When only one ion was obtained in the single-stage NCI-MS, a representative product ion from MSMS experiments was used as identification criterion. A total of 30 real samples were analyzed and 67 % of the samples were positive for 12 different pesticides in the range 1.0-1321.3 μg kg(-1).
Townsend, Robert; Kato, Kota; Hale, Christine; Kowalski, Donna; Lademacher, Christopher; Yamazaki, Takao; Akhtar, Shahzad; Desai, Amit
2018-02-01
Isavuconazonium sulfate is the water-soluble prodrug of the active triazole isavuconazole. Two phase 1 studies were conducted to identify the metabolic profile and mass balance of isavuconazole and BAL8728 (inactive cleavage product). Seven subjects in study 1 (isavuconazole mass balance) received a single oral dose of [cyano- 14 C]isavuconazonium sulfate corresponding to 200 mg isavuconazole. Six subjects in study 2 (BAL8728 mass balance) received a single intravenous dose of [pyridinylmethyl- 14 C]isavuconazonium sulfate corresponding to 75 mg BAL8728. Pharmacokinetic parameters of radioactivity in whole blood and plasma and of isavuconazole and BAL8728 in plasma were assessed. Radioactivity ratio of blood/plasma, percentage of dose, and cumulative percentage of radioactive dose recovered in urine and feces for isavuconazole and BAL8728 were assessed. Metabolic profiling was carried out by high-performance liquid chromatography and mass spectrometry. Mean plasma isavuconazole pharmacokinetic parameters included apparent clearance (2.3 ± 0.7 L/h), apparent volume of distribution (301.8 ± 105.7 L), and terminal elimination half-life (99.9 ± 44.6 hours). In study 1, isavuconazole-derived radioactivity was recovered approximately equally in urine and feces (46.1% and 45.5%, respectively). In study 2, BAL8728-derived radioactivity was predominantly recovered in urine (96.0%). Isavuconazole (study 1) and M4 (cleavage metabolite of BAL8728; study 2) were the predominant circulating components of radioactivity in plasma. © 2017 The Authors. Clinical Pharmacology in Drug Development Published by Wiley Periodicals, Inc. on behalf of The American College of Clinical Pharmacology.
Cuervo, Darío; Loli, Cynthia; Fernández-Álvarez, María; Muñoz, Gloria; Carreras, Daniel
2017-10-15
A complete analytical protocol for the determination of 25 doping-related peptidic drugs and 3 metabolites in urine was developed by means of accurate-mass quadrupole time-of-flight (Q-TOF) LC-MS analysis following solid-phase extraction (SPE) on microplates and conventional SPE pre-treatment for initial testing and confirmation, respectively. These substances included growth hormone releasing factors, gonadotropin releasing factors and anti-diuretic hormones, with molecular weights ranging from 540 to 1320Da. Optimal experimental conditions were stablished after investigation of different parameters concerning sample preparation and instrumental analysis. Weak cation exchange SPE followed by C18 HPLC chromatography and accurate mass detection provided the required sensitivity and selectivity for all the target peptides under study. 2mg SPE on 96-well microplates can be used in combination with full scan MS detection for the initial testing, thus providing a fast, cost-effective and high-throughput protocol for the processing of a large batch of samples simultaneously. On the other hand, extraction on 30mg SPE cartridges and subsequent target MS/MS determination was the protocol of choice for confirmatory purposes. The methodology was validated in terms of selectivity, recovery, matrix effect, precision, sensitivity (limit of detection, LOD), cross contamination, carryover, robustness and stability. Recoveries ranged from 6 to 70% (microplates) and 17-95% (cartridges), with LODs from 0.1 to 1ng/mL. The suitability of the method was assessed by analyzing different spiked or excreted urines containing some of the target substances. Copyright © 2017 Elsevier B.V. All rights reserved.
2016-01-01
Occurrence and removal of six high-production high-volume neonicotinoids was investigated in 13 conventional wastewater treatment plants (WWTPs) and one engineered wetland. Flow-weighted daily composites were analyzed by isotope dilution liquid chromatography tandem mass spectrometry, revealing the occurrence of imidacloprid, acetamiprid, and clothianidin at ng/L concentrations in WWTP influent (60.5 ± 40.0; 2.9 ± 1.9; 149.7 ± 289.5, respectively) and effluent (58.5 ± 29.1; 2.3 ± 1.4; 70.2 ± 121.8, respectively). A mass balance showed insignificant removal of imidacloprid (p = 0.09, CI = 95%) and limited removal of the sum of acetamiprid and its degradate, acetamiprid-N-desmethyl (18 ± 4%, p = 0.01, CI = 95%). Clothianidin was found only intermittently, whereas thiamethoxam, thiacloprid, and dinotefuran were never detected. In the wetland, no removal of imidacloprid or acetamiprid was observed. Extrapolation of data from 13 WWTPs to the nation as a whole suggests annual discharges on the order of 1000–3400 kg/y of imidacloprid contained in treated effluent to surface waters nationwide. This first mass balance and first United States nationwide wastewater reconnaissance identified imidacloprid, acetamiprid, and clothianidin as recalcitrant sewage constituents that persist through wastewater treatment to enter water bodies at significant loadings, potentially harmful to sensitive aquatic invertebrates. PMID:27196423
NASA Astrophysics Data System (ADS)
Haywood, Raphaëlle D.; Vanderburg, Andrew; Mortier, Annelies; Giles, Helen A. C.; López-Morales, Mercedes; Lopez, Eric D.; Malavolta, Luca; Charbonneau, David; Collier Cameron, Andrew; Coughlin, Jeffrey L.; Dressing, Courtney D.; Nava, Chantanelle; Latham, David W.; Dumusque, Xavier; Lovis, Christophe; Molinari, Emilio; Pepe, Francesco; Sozzetti, Alessandro; Udry, Stéphane; Bouchy, François; Johnson, John A.; Mayor, Michel; Micela, Giusi; Phillips, David; Piotto, Giampaolo; Rice, Ken; Sasselov, Dimitar; Ségransan, Damien; Watson, Chris; Affer, Laura; Bonomo, Aldo S.; Buchhave, Lars A.; Ciardi, David R.; Fiorenzano, Aldo F.; Harutyunyan, Avet
2018-05-01
We present the confirmation of a small, moderately irradiated (F = 155 ± 7 F ⊕) Neptune with a substantial gas envelope in a P = 11.8728787 ± 0.0000085 day orbit about a quiet, Sun-like G0V star Kepler-1655. Based on our analysis of the Kepler light curve, we determined Kepler-1655b’s radius to be 2.213 ± 0.082 R ⊕. We acquired 95 high-resolution spectra with Telescopio Nazionale Galileo/HARPS-N, enabling us to characterize the host star and determine an accurate mass for Kepler-1655b of 5.0{+/- }2.83.1 {M}\\oplus via Gaussian-process regression. Our mass determination excludes an Earth-like composition with 98% confidence. Kepler-1655b falls on the upper edge of the evaporation valley, in the relatively sparsely occupied transition region between rocky and gas-rich planets. It is therefore part of a population of planets that we should actively seek to characterize further.
Galaxy And Mass Assembly: accurate panchromatic photometry from optical priors using LAMBDAR
NASA Astrophysics Data System (ADS)
Wright, A. H.; Robotham, A. S. G.; Bourne, N.; Driver, S. P.; Dunne, L.; Maddox, S. J.; Alpaslan, M.; Andrews, S. K.; Bauer, A. E.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Clarke, C.; Cluver, M.; Davies, L. J. M.; Grootes, M. W.; Holwerda, B. W.; Hopkins, A. M.; Jarrett, T. H.; Kafle, P. R.; Lange, R.; Liske, J.; Loveday, J.; Moffett, A. J.; Norberg, P.; Popescu, C. C.; Smith, M.; Taylor, E. N.; Tuffs, R. J.; Wang, L.; Wilkins, S. M.
2016-07-01
We present the Lambda Adaptive Multi-Band Deblending Algorithm in R (LAMBDAR), a novel code for calculating matched aperture photometry across images that are neither pixel- nor PSF-matched, using prior aperture definitions derived from high-resolution optical imaging. The development of this program is motivated by the desire for consistent photometry and uncertainties across large ranges of photometric imaging, for use in calculating spectral energy distributions. We describe the program, specifically key features required for robust determination of panchromatic photometry: propagation of apertures to images with arbitrary resolution, local background estimation, aperture normalization, uncertainty determination and propagation, and object deblending. Using simulated images, we demonstrate that the program is able to recover accurate photometric measurements in both high-resolution, low-confusion, and low-resolution, high-confusion, regimes. We apply the program to the 21-band photometric data set from the Galaxy And Mass Assembly (GAMA) Panchromatic Data Release (PDR; Driver et al. 2016), which contains imaging spanning the far-UV to the far-IR. We compare photometry derived from LAMBDAR with that presented in Driver et al. (2016), finding broad agreement between the data sets. None the less, we demonstrate that the photometry from LAMBDAR is superior to that from the GAMA PDR, as determined by a reduction in the outlier rate and intrinsic scatter of colours in the LAMBDAR data set. We similarly find a decrease in the outlier rate of stellar masses and star formation rates using LAMBDAR photometry. Finally, we note an exceptional increase in the number of UV and mid-IR sources able to be constrained, which is accompanied by a significant increase in the mid-IR colour-colour parameter-space able to be explored.
Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr
NASA Astrophysics Data System (ADS)
Parrenin, Frédéric; Fujita, Shuji; Abe-Ouchi, Ayako; Kawamura, Kenji; Masson-Delmotte, Valérie; Motoyama, Hideaki; Saito, Fuyuki; Severi, Mirko; Stenni, Barbara; Uemura, Ryu; Wolff, Eric
2016-04-01
Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level change. Here we reconstruct the past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronisation of the two ice cores and on corrections for the vertical thinning of layers. During the past 216,000 years, this SMB ratio, denoted SMB_EDC/SMB_DF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 20% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not reflected in the isotope profiles are one of the possible causes of the observed differences between the ice core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air mass trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for ice sheet modeling (for which SMB is a boundary condition) or atmospheric modeling (our inferred SMB
Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr
NASA Astrophysics Data System (ADS)
Parrenin, F.; Fujita, S.; Abe-Ouchi, A.; Kawamura, K.; Masson-Delmotte, V.; Motoyama, H.; Saito, F.; Severi, M.; Stenni, B.; Uemura, R.; Wolff, E.
2015-02-01
Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level. Here we reconstruct the past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronisation of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 years, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, decreasing during cold periods and increasing during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within interglacial periods and during the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 30% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not closely related to isotopic changes are one of the possible causes of the observed gaps between the ice core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air mass trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for ice sheet modeling (for which SMB is a boundary condition) or atmospheric
Improving traditional balancing methods for high-speed rotors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ling, J.; Cao, Y.
1996-01-01
This paper introduces frequency response functions, analyzes the relationships between the frequency response functions and influence coefficients theoretically, and derives corresponding mathematical equations for high-speed rotor balancing. The relationships between the imbalance masses on the rotor and frequency response functions are also analyzed based upon the modal balancing method, and the equations related to the static and dynamic imbalance masses and the frequency response function are obtained. Experiments on a high-speed rotor balancing rig were performed to verify the theory, and the experimental data agree satisfactorily with the analytical solutions. The improvement on the traditional balancing method proposed in thismore » paper will substantially reduce the number of rotor startups required during the balancing process of rotating machinery.« less
Dynamic Stability and Gravitational Balancing of Multiple Extended Bodies
NASA Technical Reports Server (NTRS)
Quadrelli, Marco
2008-01-01
Feasibility of a non-invasive compensation scheme was analyzed for precise positioning of a massive extended body in free fall using gravitational forces influenced by surrounding source masses in close proximity. The N-body problem of classical mechanics is a paradigm used to gain insight into the physics of the equivalent N-body problem subject to control forces. The analysis addressed how a number of control masses move around the proof mass so that the proof mass position can be accurately and remotely compensated when exogenous disturbances are acting on it, while its sensitivity to gravitational waves remains unaffected. Past methods to correct the dynamics of the proof mass have considered active electrostatic or capacitive methods, but the possibility of stray capacitances on the surfaces of the proof mass have prompted the investigation of other alternatives, such as the method presented in this paper. While more rigorous analyses of the problem should be carried out, the data show that, by means of a combined feedback and feed-forward control approach, the control masses succeeded in driving the proof mass along the specified trajectory, which implies that the proof mass can, in principle, be balanced via gravitational forces only while external perturbations are acting on it. This concept involves the dynamic stability of a group of massive objects interacting gravitationally under active control, and can apply to drag-free control of spacecraft during missions, to successor gravitational wave space borne sensors, or to any application requiring flying objects to be precisely controlled in position and attitude relative to another body via gravitational interactions only.
Source identification and mass balance studies of mercury in Lake An-dong, S. Korea
NASA Astrophysics Data System (ADS)
Han, J.; Byeon, M.; Yoon, J.; Park, J.; Lee, M.; Huh, I.; Na, E.; Chung, D.; Shin, S.; Kim, Y.
2009-12-01
In this study, mercury and methylmercury were measured in atmospheric, tributary, open-lake water column, sediment, planktons and fish samples in the catchments area of Lake An-dong, S. Korea. Lake An-dong, an artificial freshwater lake is located on the upstream of River Nak-dong. It has 51.5 km2 of open surface water and 1.33 year of hydraulic residence time. It is a source of drinking water for 0.3 million S. Koreans. Recently, the possibilities of its mercury contamination became an issue since current studies showed that the lake had much higher mercury level in sediment and certain freshwater fish species than any other lakes in S. Korea. This catchments area has the possibilities of historical mercury pollution by the location of more than 50 abandoned gold mines and Young-poong zinc smelter. The objective of this study was to develop a mercury mass balance and identify possible mercury sources in the lake. The results of this study are thus expected to offer valuable insights for the sources of mercury loading through the watershed. In order to estimate the mercury flux, TGM, RGM and particulate mercury were measured using TEKRAN 2537 at the five sites surrounding Lake An-dong from May, 2009 with wet and dry deposition. The fate and transport of mercury in water body were predicted by using EFDC (Environmental Dynamic Fluid Code) and Mercury module in WASP7 (Water quality analysis program) after subsequent distribution into water body, sediments, followed by bioaccumulation and ultimate uptake by humans. The mercury mass balance in Young-poong zinc smelter was also pre-estimated by measuring mercury content in zinc ores, emission gases, sludge, wastewater and products.
Yang, Guan-Dong; Agapow, Paul-Michael
2017-01-01
The kind and duration of phylogenetic topological “signatures” left in the wake of macroevolutionary events remain poorly understood. To this end, we examined a broad range of simulated phylogenies generated using trait-biased, heritable speciation probabilities and mass extinction that could be either random or selective on trait value, but also using background extinction and diversity-dependence to constrain clade sizes. In keeping with prior results, random mass extinction increased imbalance of clades that recovered to pre-extinction size, but was a relatively weak effect. Mass extinction that was selective on trait values tended to produce clades of similar or greater balance compared to random extinction or controls. Allowing evolution to continue past the point of clade-size recovery resulted in erosion and eventual erasure of this signal, with all treatments converging on similar values of imbalance, except for very intense extinction regimes targeted at taxa with high speciation rates. Return to a more balanced state with extended post-extinction evolution was also associated with loss of the previous phylogenetic root in most treatments. These results further demonstrate that while a mass extinction event can produce a recognizable phylogenetic signal, its effects become increasingly obscured the further an evolving clade gets from that event, with any sharp imbalance due to unrelated evolutionary factors. PMID:28644846
Berryman, C E; Sepowitz, J J; McClung, H L; Lieberman, H R; Farina, E K; McClung, J P; Ferrando, A A; Pasiakos, S M
2017-06-01
Negative energy balance during military operations can be severe and result in significant reductions in fat-free mass (FFM). Consuming supplemental high-quality protein following such military operations may accelerate restoration of FFM. Body composition (dual-energy X-ray absorptiometry) and whole body protein turnover (single-pool [ 15 N]alanine method) were determined before (PRE) and after 7 days (POST) of severe negative energy balance during military training in 63 male US Marines (means ± SD, 25 ± 3 yr, 84 ± 9 kg). After POST measures were collected, volunteers were randomized to receive higher protein (HIGH: 1,103 kcal/day, 133 g protein/day), moderate protein (MOD: 974 kcal/day, 84 g protein/day), or carbohydrate-based low protein control (CON: 1,042 kcal/day, 7 g protein/day) supplements, in addition to a self-selected, ad libitum diet, for the 27-day intervention (REFED). Measurements were repeated POST-REFED. POST total body mass (TBM; -5.8 ± 1.0 kg, -7.0%), FFM (-3.1 ± 1.6 kg, -4.7%), and net protein balance (-1.7 ± 1.1 g protein·kg -1 ·day -1 ) were lower and proteolysis (1.1 ± 1.9 g protein·kg -1 ·day -1 ) was higher compared with PRE ( P < 0.05). Self-selected, ad libitum dietary intake during REFED was similar between groups (3,507 ± 730 kcal/day, 2.0 ± 0.5 g protein·kg -1 ·day -1 ). However, diets differed by protein intake due to supplementation (CON: 2.0 ± 0.4, MOD: 3.2 ± 0.7, and HIGH: 3.5 ± 0.7 g·kg -1 ·day -1 ; P < 0.05) but not total energy (4,498 ± 725 kcal/day). All volunteers, independent of group assignment, achieved positive net protein balance (0.4 ± 1.0 g protein·kg -1 ·day -1 ) and gained TBM (5.9 ± 1.7 kg, 7.8%) and FFM (3.6 ± 1.8 kg, 5.7%) POST-REFED compared with POST ( P < 0.05). Supplementing ad libitum, energy-adequate, higher protein diets with additional protein may not be necessary to restore FFM after short-term severe negative energy balance. NEW & NOTEWORTHY This article demonstrates 1 ) the
NASA Astrophysics Data System (ADS)
Kiefer, F.; Halbwachs, J.-L.; Lebreton, Y.; Soubiran, C.; Arenou, F.; Pourbaix, D.; Famaey, B.; Guillout, P.; Ibata, R.; Mazeh, T.
2018-02-01
The orbital motion of non-contact double-lined spectroscopic binaries (SB2s), with periods of a few tens of days to several years, holds unique, accurate information on individual stellar masses, which only long-term monitoring can unlock. The combination of radial velocity measurements from high-resolution spectrographs and astrometric measurements from high-precision interferometers allows the derivation of SB2 component masses down to the percent precision. Since 2010, we have observed a large sample of SB2s with the SOPHIE spectrograph at the Observatoire de Haute-Provence, aiming at the derivation of orbital elements with sufficient accuracy to obtain masses of components with relative errors as low as 1 per cent when the astrometric measurements of the Gaia satellite are taken into account. In this paper, we present the results from 6 yr of observations of 14 SB2 systems with periods ranging from 33 to 4185 days. Using the TODMOR algorithm, we computed radial velocities from the spectra and then derived the orbital elements of these binary systems. The minimum masses of the 28 stellar components are then obtained with an average sample accuracy of 1.0 ± 0.2 per cent. Combining the radial velocities with existing interferometric measurements, we derived the masses of the primary and secondary components of HIP 61100, HIP 95995 and HIP 101382 with relative errors for components (A,B) of, respectively, (2.0, 1.7) per cent, (3.7, 3.7) per cent and (0.2, 0.1) per cent. Using the CESAM2K stellar evolution code, we constrained the initial He abundance, age and metallicity for HIP 61100 and HIP 95995.
Comparisons of soil nitrogen mass balances for an ...
We compared the N budgets of an ombrotrophic bog and a minerotrophic fen to quantify the importance of denitrification in peatlands and their watersheds. We also compared the watershed upland mineral soils to bog/fen peat; lagg and transition zone peat to central bog/fen peat; and surface, mid-layer and deep soil and peat horizons. Bog and fen area were derived from a wetland boundary GIS data layer, and bog and fen volumes were calculated as the interpolated product of area and depth of peat. Atmospheric N deposition to the bog and fen were based on measurements from a station located 2km north of the bog watershed and 0.5km from the fen watershed. Precipitation was analyzed for nitrate (NO3-), ammonium (NH4+), and total N (TN), and aggregated to annual values. Outflow water samples from the bog and fen were collected as surface grab samples on each of the May-October sampling dates over the 2010-2013 study, and were analyzed and aggregated annually as for atmospheric N. Soil and peat samples were analyzed for N content, and for net ammonification (AM), nitrification (NT), and ambient (DN) and potential (DEA) denitrification rates. Nitrogen mass balances are based on mean annual atmospheric deposition and outflow; soil and peat standing stocks of N, and mean annual estimates of DN, weighted for contributions of the uplands, lagg or transition zone, and bog or fen hollows and hummocks, and accounting for soil depth effects. Annual deposition of N species was: N
NASA Astrophysics Data System (ADS)
Coatman, Liam; Hewett, Paul C.; Banerji, Manda; Richards, Gordon T.; Hennawi, Joseph F.; Prochaska, Jason X.
2017-01-01
Accurate black-hole (BH) mass estimates for high-redshift (z>2) quasars are essential for better understanding the relationship between super-massive BH accretion and star formation. Progress is currently limited by the large systematic errors in virial BH-masses derived from the CIV broad emission line, which is often significantly blueshifted relative to systemic, most likely due to outflowing gas in the quasar broad-line region. We have assembled Balmer-line based BH masses for a large sample of 230 high-luminosity (1045.5-1048 ergs-1), redshift 1.5
A mass balance approach to investigate arsenic cycling in a petroleum plume.
Ziegler, Brady A; Schreiber, Madeline E; Cozzarelli, Isabelle M; Crystal Ng, G-H
2017-12-01
Natural attenuation of organic contaminants in groundwater can give rise to a series of complex biogeochemical reactions that release secondary contaminants to groundwater. In a crude oil contaminated aquifer, biodegradation of petroleum hydrocarbons is coupled with the reduction of ferric iron (Fe(III)) hydroxides in aquifer sediments. As a result, naturally occurring arsenic (As) adsorbed to Fe(III) hydroxides in the aquifer sediment is mobilized from sediment into groundwater. However, Fe(III) in sediment of other zones of the aquifer has the capacity to attenuate dissolved As via resorption. In order to better evaluate how long-term biodegradation coupled with Fe-reduction and As mobilization can redistribute As mass in contaminated aquifer, we quantified mass partitioning of Fe and As in the aquifer based on field observation data. Results show that Fe and As are spatially correlated in both groundwater and aquifer sediments. Mass partitioning calculations demonstrate that 99.9% of Fe and 99.5% of As are associated with aquifer sediment. The sediments act as both sources and sinks for As, depending on the redox conditions in the aquifer. Calculations reveal that at least 78% of the original As in sediment near the oil has been mobilized into groundwater over the 35-year lifespan of the plume. However, the calculations also show that only a small percentage of As (∼0.5%) remains in groundwater, due to resorption onto sediment. At the leading edge of the plume, where groundwater is suboxic, sediments sequester Fe and As, causing As to accumulate to concentrations 5.6 times greater than background concentrations. Current As sinks can serve as future sources of As as the plume evolves over time. The mass balance approach used in this study can be applied to As cycling in other aquifers where groundwater As results from biodegradation of an organic carbon point source coupled with Fe reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.
Mass balance of polychlorinated biphenyls and other organochlorine compounds in a lactating cow
DOE Office of Scientific and Technical Information (OSTI.GOV)
McLachlan, M.S.
1993-03-01
A contaminant mass balance was conducted of a lactating cow in its natural state. PCBs, HDHs, DDE, DDT, HCB, and several other chlorinated substances were investigated. It was found that virtually all of the cow's exposure was through feed. The contaminant absorption in the cow and hence the carry-over rate of persistent compounds was found to be a function of K[sub ow], with approximately constant values up to a log K[sub ow] of 6.5 and thereafter rapidly decreasing absorption with increasing lipophilicity of the contaminant. The key to PCB persistence in the cow was the 4,4[prime] substitution pattern. The 2,3,5more » substitution was a less effective hindrance for PCB metabolism. 33 refs., 2 figs., 7 tabs.« less
Mass balance of the Antarctic ice sheet.
Wingham, D J; Shepherd, A; Muir, A; Marshall, G J
2006-07-15
The Antarctic contribution to sea-level rise has long been uncertain. While regional variability in ice dynamics has been revealed, a picture of mass changes throughout the continental ice sheet is lacking. Here, we use satellite radar altimetry to measure the elevation change of 72% of the grounded ice sheet during the period 1992-2003. Depending on the density of the snow giving rise to the observed elevation fluctuations, the ice sheet mass trend falls in the range -5-+85Gtyr-1. We find that data from climate model reanalyses are not able to characterise the contemporary snowfall fluctuation with useful accuracy and our best estimate of the overall mass trend-growth of 27+/-29Gtyr-1-is based on an assessment of the expected snowfall variability. Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica. The result exacerbates the difficulty of explaining twentieth century sea-level rise.
Breivik, Knut; Sweetman, Andy; Pacyna, Jozef M; Jones, Kevin C
2007-05-15
Previously published estimates of the global production, consumption and atmospheric emissions of 22 individual PCB congeners [Breivik K, Sweetman A, Pacyna JM, Jones KC. Towards a global historical emission inventory for selected PCB congeners - a mass balance approach. 1. Global production and consumption. Sci Total Environ 2002a; 290: 181-198.; Breivik K, Sweetman A, Pacyna JM, Jones KC. Towards a global historical emission inventory for selected PCB congeners--a mass balance approach. 2. Emissions. Sci Total Environ 2002b; 290: 181-198.] have provided useful information for later studies attempting to interpret contaminant levels in remote areas as well as in the global environment. As a result of the need for more contemporary emission data (following the year 2000), an update of this emission database is presented. This exercise takes into account new information on PCB production in Poland, as well as new data on the chemical composition of various technical mixtures for which less information had been available. The methodology to estimate temporal trends of PCB emissions associated with various types of PCB usage is improved. Projected emissions up to year 2100 are presented to facilitate predictions of future environmental exposure. The national emission data for each of the 114 countries considered is spatially resolved on a 1 degrees x1 degrees grid for each congener and year, using population density as a surrogate.
March, Rod S.
2000-01-01
The 1995 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data obtained in the basin. Averaged over the glacier, the measured winter snow balance was 0.94 meter on April 19, 1995, 0.6 standard deviation below the long-term average; the maximum winter snow balance, 0.94 meter, was reached on April 25, 1995; the net balance (from September 18, 1994 to August 29, 1995) was -0.70 meter, 0.76 standard deviation below the long-term average. The annual balance (October 1, 1994, to September 30, 1995) was -0.86 meter. Ice-surface motion and altitude changes measured at three index sites document seasonal ice speed and glacier-thickness changes. Annual stream runoff was 2.05 meters averaged over the basin, approximately equal to the long-term average. The 1976 ice-thickness data are reported from a single site near the highest measurement site (180 meters thick) and from two glacier cross profiles near the mid-glacier (270 meters thick on centerline) and low glacier (150 meters thick on centerline) measurement sites. A new area-altitude distribution determined from 1993 photogrammetry is reported. Area-averaged balances are reported from both the 1967 and 1993 area-altitude distribution so the reader may directly see the effect of the update. Briefly, loss of ablation area between 1967 and 1993 results in a larger weighting being applied to data from the upper glacier site and hence, increases calculated area-averaged balances. The balance increase is of the order of 15 percent for net balance.
NASA Astrophysics Data System (ADS)
Melis, T. S.; Topping, D. J.; Rubin, D. M.; Agrawal, Y. C.
2002-12-01
Intensive monitoring of suspended-sediment in the Colorado River ecosystem below Glen Canyon Dam is a priority for environmental management. Historically, the program has been logistically complicated, costly and limited in spatial and temporal resolution. These elements have contributed to relatively large uncertainties in mass-balance estimates of sediment export. To improve mass-balance estimates, the Grand Canyon Monitoring and Research Center is field testing new and existing technologies to develop a continuous suspended-sediment transport protocol. A recent innovation includes use of optical forward-scattering instruments, LISST, in combination with programmable pumping samplers. The LISST-100 (Laser In-Situ Scattering and Transmissometry) is both a particle-size analyzer (size range 2.5 to 500 microns) and a transmissometer capable of measuring variable concentrations, depending on particle size. A second innovation, the LISST-25X, is a recently developed variation of the instrumentation that allows sand to be measured separately from finer particles. This is achieved by use of shaped focal plane detectors that compute 2 distinct weighted sums of angular scattering by suspended particles. The LISST-25X currently collects volume-concentration and grain size (Sauter-mean-diameter) data for suspended particles at four sites below the dam. Unit values are derived by averaging 1000 individual measurements every 15-minutes (sampling about 1.1 liters of water per hour). The volume-to-mass conversion is made once average particle density has been gravimetrically determined through conventional methods. During high-concentration conditions, laser-transmission values (T) can fall outside of the user-defined minimal threshold (20
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.;
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.
Lee, Hyeyoung; Cuthbertson, Daniel J; Otter, Don E; Barile, Daniela
2016-08-17
A bovine milk oligosaccharide (BMO) library, prepared from cow colostrum, with 34 structures was generated and used to rapidly screen oligosaccharides in domestic animal milks and a whey permeate powder. The novel library was entered into a custom Personal Compound Database and Library (PCDL) and included accurate mass, retention time, and tandem mass spectra. Oligosaccharides in minute-sized samples were separated using nanoliquid chromatography (nanoLC) coupled to a high resolution and sensitive quadrupole-Time of Flight (Q-ToF) MS system. Using the PCDL, 18 oligosaccharides were found in a BMO-enriched product obtained from whey permeate processing. The usefulness of the analytical system and BMO library was further validated using milks from domestic sheep and buffaloes. Through BMO PCDL searching, 15 and 13 oligosaccharides in the BMO library were assigned in sheep and buffalo milks, respectively, thus demonstrating significant overlap between oligosaccharides in bovine (cow and buffalo) and ovine (sheep) milks. This method was shown to be an efficient, reliable, and rapid tool to identify oligosaccharide structures using automated spectral matching.
Lee, Hyeyoung; Cuthbertson, Daniel J.; Otter, Don E.; Barile, Daniela
2018-01-01
A bovine milk oligosaccharide (BMO) library, prepared from cow colostrum, with 34 structures was generated and used to rapidly screen oligosaccharides in domestic animal milks and a whey permeate powder. The novel library was entered into a custom Personal Compound Database and Library (PCDL) and included accurate mass, retention time, and tandem mass spectra. Oligosaccharides in minute-sized samples were separated using nanoliquid chromatography (nanoLC) coupled to a high resolution and sensitive quadrupole-Time of Flight (Q-ToF) MS system. Using the PCDL, 18 oligosaccharides were found in a BMO-enriched product obtained from whey permeate processing. The usefulness of the analytical system and BMO library was further validated using milks from domestic sheep and buffaloes. Through BMO PCDL searching, 15 and 13 oligosaccharides in the BMO library were assigned in sheep and buffalo milks, respectively, thus demonstrating significant overlap between oligosaccharides in bovine (cow and buffalo) and ovine (sheep) milks. This method was shown to be an efficient, reliable, and rapid tool to identify oligosaccharide structures using automated spectral matching. PMID:27428379
Experimental Evaluation of Balance Prediction Models for Sit-to-Stand Movement in the Sagittal Plane
Pena Cabra, Oscar David; Watanabe, Takashi
2013-01-01
Evaluation of balance control ability would become important in the rehabilitation training. In this paper, in order to make clear usefulness and limitation of a traditional simple inverted pendulum model in balance prediction in sit-to-stand movements, the traditional simple model was compared to an inertia (rotational radius) variable inverted pendulum model including multiple-joint influence in the balance predictions. The predictions were tested upon experimentation with six healthy subjects. The evaluation showed that the multiple-joint influence model is more accurate in predicting balance under demanding sit-to-stand conditions. On the other hand, the evaluation also showed that the traditionally used simple inverted pendulum model is still reliable in predicting balance during sit-to-stand movement under non-demanding (normal) condition. Especially, the simple model was shown to be effective for sit-to-stand movements with low center of mass velocity at the seat-off. Moreover, almost all trajectories under the normal condition seemed to follow the same control strategy, in which the subjects used extra energy than the minimum one necessary for standing up. This suggests that the safety considerations come first than the energy efficiency considerations during a sit to stand, since the most energy efficient trajectory is close to the backward fall boundary. PMID:24187580
NASA Astrophysics Data System (ADS)
Vladimirova, D.; Ekaykin, A.; Lipenkov, V.; Popov, S. V.; Petit, J. R.; Masson-Delmotte, V.
2017-12-01
Glaciological and meteorological observations conducted during the past four decades in Princess Elizabeth Land, East Antarctica, are compiled. The database is used to investigate spatial patterns of surface snow isotopic composition and surface mass balance, including detailed information near subglacial lake Vostok. We show diverse relationships between snow isotopic composition and surface temperature. In the most inland part (elevation 3200-3400 m a.s.l.), surface snow isotopic composition varies independently from surface temperature, and is closely related to the distance to the open water source (with a slope of 0.98±0.17 ‰ per 100 km). Surface mass balance values are higher along the ice sheet slope, and relatively evenly distributed inland. The minimum values of snow isotopic composition and surface mass balance are identified in an area XX km southwestward from Vostok station. The spatial distribution of deuterium excess delineates regions influenced by the Indian Ocean and Pacific Ocean air masses, with Vostok area being situated close to their boundary. Anomalously high deuterium excess values are observed near Dome A, suggesting high kinetic fractionation for its moisture source, or specifically high post-deposition artifacts. The dataset is available for further studies such as the assessment of skills of general circulation or regional atmospheric models, and the search for the oldest ice.
Eltoukhy, Moataz A; Kuenze, Christopher; Oh, Jeonghoon; Signorile, Joseph F
2018-01-01
Reduction in balance is an indicator of fall risk, and therefore, an accurate and cost-effective balance assessment tool is essential for prescribing effective postural control strategies. This study established the validity of the Kinect v2 sensor in assessing center of mass (CoM) excursion and velocity during single-leg balance and voluntary ankle sway tasks among young and elderly subjects. We compared balance outcome measures (anteroposterior (AP) and mediolateral (ML) CoM excursion and velocity and average sway length) to a traditional three-dimensional motion analysis system. Twenty subjects (10 young: age = y, height cm, weight kg; 10 elderly: age y, height cm, weight kg), with no history of lower extremity injury, participated in this study. Subjects performed six randomized trials; four single-leg stand (SLS) and two ankle sway trials. SLS and voluntary ankle sway trials showed that consistency (ICC(2, k)) and agreement (ICC(3, k)) for all variables when all subjects were considered, as well as when the elderly and young groups were analyzed separately. Concordance between systems ranged from poor to nearly perfect depending on the group, task, and variable assessed.
NASA Astrophysics Data System (ADS)
Battaïa, Olga; Dolgui, Alexandre; Guschinsky, Nikolai; Levin, Genrikh
2014-10-01
Solving equipment selection and line balancing problems together allows better line configurations to be reached and avoids local optimal solutions. This article considers jointly these two decision problems for mass production lines with serial-parallel workplaces. This study was motivated by the design of production lines based on machines with rotary or mobile tables. Nevertheless, the results are more general and can be applied to assembly and production lines with similar structures. The designers' objectives and the constraints are studied in order to suggest a relevant mathematical model and an efficient optimization approach to solve it. A real case study is used to validate the model and the developed approach.
Research concerning the balancing of a plane mechanism
NASA Astrophysics Data System (ADS)
Bădoiu, D.; Petrescu, M. G.; Antonescu, N. N.; Toma, G.
2018-01-01
By statically balancing of the plane mechanisms and especially those functioning at high speeds is being pursued the decrease of the value of the resultant force of all inertia forces that work on the component elements, thus obtaining a significant decrease in vibrations and shocks during the functioning. On the other hand, the existence of balancing masses which ensure the balancing of the mechanism leads to increased gauge and its mass. In this paper are presented some possibilities of statically balancing a plane mechanism which is composed of three independent contours. First is analyzed the case when the mechanism is totally balanced. Then a solution is proposed for a partial balancing of the mechanism based on the balancing of the first harmonic of the inertia force developed in a piston of the mechanism. Finally, are presented some simulation results concerning the variation of the value of the resultant inertia force during a cinematic cycle when the mechanism is unbalanced and when it is partially balanced. Also, it is analyzed the variation of the motor moment when the mechanism is unbalanced and when is totally and partially balanced.
Nakada, N; Yasojima, M; Okayasu, Y; Komori, K; Suzuki, Y
2010-01-01
The behavior of antibacterial triclosan, insect-repellent diethyltoluamide (DEET), anticonvulsant carbamazepine, and antipruritic crotamiton was investigated at two sewage treatment plants (STPs) to clarify their complete mass balance. Twenty-four-hour flow-proportional composite samples were collected from the influent and effluent of primary and final sedimentation tanks, a biofiltration tank and disinfection tanks. Sludge samples (i.e., activated and excess sludge) and samples of the return flow from the sludge treatment process were collected in the same manner. The analytes in both the dissolved and particulate phases were individually determined by a gas chromatograph equipped with mass spectrometer. Triclosan was dominantly detected in the particulate phase especially in the early stage of treatment (up to 83%) and was efficiently removed (over 90%) in STPs, mainly by sorption to sewage sludge. Limited removal was observed for DEET (55+/-24%), while no significant removal was demonstrated for crotamiton or carbamazepine. The solid-water distribution coefficients (K(d), n=4) for triclosan (log K(d): 3.7-5.1), DEET (1.3-1.9) and crotamiton (1.1-1.6) in the sludge samples are also determined in this study. These findings indicate the limitations of current sewage treatment techniques for the removal of these water-soluble drugs (i.e. DEET, carbamazepine, and crotamiton).
Incorrect interpretation of carbon mass balance biases global vegetation fire emission estimates
Surawski, N. C.; Sullivan, A. L.; Roxburgh, S. H.; Meyer, C.P. Mick; Polglase, P. J.
2016-01-01
Vegetation fires are a complex phenomenon in the Earth system with many global impacts, including influences on global climate. Estimating carbon emissions from vegetation fires relies on a carbon mass balance technique that has evolved with two different interpretations. Databases of global vegetation fire emissions use an approach based on ‘consumed biomass', which is an approximation to the biogeochemically correct ‘burnt carbon' approach. Here we show that applying the ‘consumed biomass' approach to global emissions from vegetation fires leads to annual overestimates of carbon emitted to the atmosphere by 4.0% or 100 Tg compared with the ‘burnt carbon' approach. The required correction is significant and represents ∼9% of the net global forest carbon sink estimated annually. Vegetation fire emission studies should use the ‘burnt carbon' approach to quantify and understand the role of this burnt carbon, which is not emitted to the atmosphere, as a sink enriched in carbon. PMID:27146785
Incorrect interpretation of carbon mass balance biases global vegetation fire emission estimates.
Surawski, N C; Sullivan, A L; Roxburgh, S H; Meyer, C P Mick; Polglase, P J
2016-05-05
Vegetation fires are a complex phenomenon in the Earth system with many global impacts, including influences on global climate. Estimating carbon emissions from vegetation fires relies on a carbon mass balance technique that has evolved with two different interpretations. Databases of global vegetation fire emissions use an approach based on 'consumed biomass', which is an approximation to the biogeochemically correct 'burnt carbon' approach. Here we show that applying the 'consumed biomass' approach to global emissions from vegetation fires leads to annual overestimates of carbon emitted to the atmosphere by 4.0% or 100 Tg compared with the 'burnt carbon' approach. The required correction is significant and represents ∼9% of the net global forest carbon sink estimated annually. Vegetation fire emission studies should use the 'burnt carbon' approach to quantify and understand the role of this burnt carbon, which is not emitted to the atmosphere, as a sink enriched in carbon.
NASA Astrophysics Data System (ADS)
Schlegel, N.; Larour, E. Y.; Gardner, A. S.; Lang, C.; Miller, C. E.; van den Broeke, M. R.
2016-12-01
How Greenland ice flow may respond to future increases in surface runoff and to increases in the frequency of extreme melt events is unclear, as it requires detailed comprehension of Greenland surface climate and the ice sheet's sensitivity to associated uncertainties. With established uncertainty quantification tools run within the framework of Ice Sheet System Model (ISSM), we conduct decadal-scale forward modeling experiments to 1) quantify the spatial resolution needed to effectively force distinct components of the surface radiation budget, and subsequently surface mass balance (SMB), in various regions of the ice sheet and 2) determine the dynamic response of Greenland ice flow to variations in components of the net radiation budget. The Glacier Energy and Mass Balance (GEMB) software is a column surface model (1-D) that has recently been embedded as a module within ISSM. Using the ISSM-GEMB framework, we perform sensitivity analyses to determine how perturbations in various components of the surface radiation budget affect model output; these model experiments allow us predict where and on what spatial scale the ice sheet is likely to dynamically respond to changes in these parameters. Preliminary results suggest that SMB should be forced at at least a resolution of 23 km to properly capture dynamic ice response. In addition, Monte-Carlo style sampling analyses reveals that the areas with the largest uncertainty in mass flux are located near the equilibrium line altitude (ELA), upstream of major outlet glaciers in the North and West of the ice sheet. Sensitivity analysis indicates that these areas are also the most vulnerable on the ice sheet to persistent, far-field shifts in SMB, suggesting that continued warming, and upstream shift in the ELA, are likely to result in increased velocities, and consequentially SMB-induced thinning upstream of major outlet glaciers. Here, we extend our investigation to consider various components of the surface radiation
Laflamme, Dorothy P; Hannah, Steven S
2013-08-01
This study was undertaken to contrast the minimum protein intake needed to maintain nitrogen balance or lean body mass (LBM) in adult cats using a prospective evaluation of 24 adult, neutered male cats fed one to three different diets. Following a 1-month baseline period during which all cats consumed a 34% protein diet, cats were fed a 20% (LO), 26% (MOD) or 34% (HI) protein diet for 2 months. During the baseline period and following the 2-month feeding period, nitrogen balance was assessed using a 96-h complete collection of urine and feces, and LBM was assessed using dual energy X-ray absorptiometry. Weight loss increased in a linear manner with decreasing protein intake (P <0.01), despite no significant difference in calorie intake. Linear regression of the data indicated that approximately 1.5 g protein/kg (2.1 g/kg(0.75)) body weight is needed to maintain nitrogen balance, while 5.2 g protein/kg (7.8 g/kg(0.75)) body weight is needed to maintain LBM. This study provides evidence that nitrogen balance studies are inadequate for determining optimum protein requirements. Animals, including cats, can adapt to low protein intake and maintain nitrogen balance while depleting LBM. Loss of LBM and an associated reduction in protein turnover can result in compromised immune function and increased morbidity. Current Association of American Feed Control Officials (AAFCO) and National Research Council (NRC) standards for protein adequacy may not provide adequate protein to support LBM. The minimum daily protein requirement for adult cats appears to be at least 5.2 g/kg (7.8 g/kg(0.75)) body weight, well in excess of current AAFCO and NRC recommendations. Further research is needed to determine the effect, if any, of body condition, age and gender on protein requirements.
NASA Astrophysics Data System (ADS)
Li, J.; Medley, B.; Neumann, T.; Smith, B. E.; Luthcke, S. B.; Zwally, H. J.
2016-12-01
Surface mass balance (SMB) data are essential in the derivation of ice sheet mass balance. This is because ice sheet mass change consists of short-term and long-term variations. The short-term variations are directly given by the SMB data. For altimetry based ice sheet mass balance studies, these short-term mass changes are converted to firn thickness changes by using a firn densification-elevation model, and then the variations are subtracted from the altimetry measurements to give the long-term ice thickness changes that are associated with the density of ice. So far various SMB data sets such as ERA-Interim, RACMO and MERRA are available and some have been widely used in large number of ice sheet mass balance studies. However theses data sets exhibit the clear discrepancies in both random and systematic manner. In this study, we use our time dependent firn densification- elevation model, driven by the SMB data from MERRA-2, RACMO2.3 and ERA-Int for the period of 1982-2015 and the temperature variations from AVHRR for the same period to examine the corresponding firn thickness variations and the impacts to the mass changes over the Greenland ice sheet. The model was initialized with the1980's climate. Our results show that the relative smaller (centimeter level) differences in the firn thickness driven by the different data set occur at the early stage (1980's) of the model run. As the time progressing, the discrepancies between the SMB data sets accumulate, and the corresponding firn thickness differences quickly become larger with the value > 2m at the end of the period. Although the overall rates for the whole period driven by each of the three data sets are small ranging -0.2 - 0.2 cm a-1 (-3.0-2.7 Gt a-1), the decadal rates can vary greatly with magnitude > 3 cm a-1 and the impact to the Greenland mass change exceeds 30 Gt a-1.
Brandam, Cédric; Lai, Quoc Phong; Julien-Ortiz, Anne; Taillandier, Patricia
2013-01-01
Torulaspora delbrueckii metabolism was assessed in a synthetic culture medium similar to grape must under various conditions: no aeration and three different oxygen feeds, in order to determine the effect of oxygen on metabolism. Carbon and nitrogen mass balances were calculated to quantify metabolic fluxes. The effect of oxygen was to decrease the flux of carbon going into the fermentation pathway in favor of growth. In the absence of aeration, higher amounts of glycerol were produced, probably to maintain the redox balance. The oxygen requirement of this strain was high, since even for the highest air supply oxygen became limiting after 24 h. Nevertheless, this strain developed well in the absence of oxygen and consumed 220 g/L of sugars (glucose/fructose) in 166 h at 20 °C, giving a good ethanol yield (0.50 g/g).
NASA Astrophysics Data System (ADS)
Wood, W. W.; Wood, W. W.
2001-05-01
Evaluation of ground-water supply in arid areas requires estimation of annual recharge. Traditional physical-based hydrologic estimates of ground-water recharge result in large uncertainties when applied in arid, mountainous environments because of infrequent, intense rainfall events, destruction of water-measuring structures associated with those events, and consequent short periods of hydrologic records. To avoid these problems and reduce the uncertainty of recharge estimates, a chloride mass-balance (CMB) approach was used to provide a time-integrated estimate. Seven basins exhibiting dry-stream beds (wadis) in the Asir and Hijaz Mountains, western Saudi Arabia, were selected to evaluate the method. Precipitation among the basins ranged from less than 70 mm/y to nearly 320 mm/y. Rain collected from 35 locations in these basins averaged 2.0 mg/L chloride. Ground water from 140 locations in the wadi alluvium averaged 200 mg/L chloride. This chloride concentration ratio of precipitation to ground water suggests that on average, approximately 1 percent of the rainfall is recharged, while the remainder is lost to evaporation. Ground-water recharge from precipitation in individual basins ranged from less than 1 to nearly 4 percent and was directly proportional to total precipitation. Independent calculations of recharge using Darcy's Law were consistent with these findings and are within the range typically found in other arid areas of the world. Development of ground water has lowered the water level beneath the wadis and provided more storage thus minimizing chloride loss from the basin by river discharge. Any loss of chloride from the basin results in an overestimate of the recharge flux by the chloride-mass balance approach. In well-constrained systems recharge in arid, mountainous areas where the mass of chloride entering and leaving the basin is known or can be reasonably estimated, the CMB approach provides a rapid, inexpensive method for estimating time
Sensitivity of the Antarctic surface mass balance to oceanic perturbations
NASA Astrophysics Data System (ADS)
Kittel, C.; Amory, C.; Agosta, C.; Fettweis, X.
2017-12-01
Regional climate models (RCMs) are suitable numerical tools to study the surface mass balance (SMB) of the wide polar ice sheets due to their high spatial resolution and polar-adapted physics. Nonetheless, RCMs are driven at their boundaries and over the ocean by reanalysis or global climate model (GCM) products and are thus influenced by potential biases in these large-scale fields. These biases can be significant for both the atmosphere and the sea surface conditions (i.e. sea ice concentration and sea surface temperature). With the RCM MAR, a set of sensitivity experiments has been realized to assess the direct response of the SMB of the Antarctic ice sheet to oceanic perturbations. MAR is forced by ERA-Interim and anomalies based on mean GCM biases are introduced in sea surface conditions. Results show significant increases (decreases) of liquid and solid precipitation due to biases related to warm (cold) oceans. As precipitation is mainly caused by low-pressure systems that intrude into the continent and do not penetrate far inland, coastal areas are more sensitive than inland regions. Furthermore, warm ocean representative biases lead to anomalies as large as anomalies simulated by other RCMs or GCMs for the end of the 21st century.
Measurement of the Accurate Mass of a 50 MDa Infectious Virus
Keifer, David Z.; Motwani, Tina; Teschke, Carolyn M.; Jarrold, Martin F.
2016-01-01
RATIONALE Bacteriophage P22 is believed to contain a total of 521 copies of 9 different proteins and a 41,724 base pair genome. Despite its enormous size and complexity, phage P22 can be electrosprayed, and it remains intact in ultra-high vacuum where its molar mass distribution has been measured. METHODS Phage P22 virions were generated by complementation in Salmonella enterica and purified. They were transferred into 100 mM ammonium acetate and then electrosprayed. The masses of individual virions were determined using charge detection mass spectrometry. RESULTS The stoichiometry of the protein components of phage P22 is sufficiently well-known that the theoretical molar mass can be determined to within a narrow range. The measured average molar mass of phage P22, 52,180±59 kDa, is consistent with the theoretical molar mass and supports the proposed stoichiometry of the components. The intrinsic width of the phage P22 mass distribution can be entirely accounted for by the distribution of DNA packaged by the headful mechanism. CONCLUSIONS At over 50 MDa, phage P22 is the largest object with a well-defined molar mass to be analyzed by mass spectrometry. The narrow measured mass distribution indicates that the virions survive the transition into the gas phase intact. PMID:27501430
Balance Calibration – A Method for Assigning a Direct-Reading Uncertainty to an Electronic Balance.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mike Stears
2010-07-01
Paper Title: Balance Calibration – A method for assigning a direct-reading uncertainty to an electronic balance. Intended Audience: Those who calibrate or use electronic balances. Abstract: As a calibration facility, we provide on-site (at the customer’s location) calibrations of electronic balances for customers within our company. In our experience, most of our customers are not using their balance as a comparator, but simply putting an unknown quantity on the balance and reading the displayed mass value. Manufacturer’s specifications for balances typically include specifications such as readability, repeatability, linearity, and sensitivity temperature drift, but what does this all mean when themore » balance user simply reads the displayed mass value and accepts the reading as the true value? This paper discusses a method for assigning a direct-reading uncertainty to a balance based upon the observed calibration data and the environment where the balance is being used. The method requires input from the customer regarding the environment where the balance is used and encourages discussion with the customer regarding sources of uncertainty and possible means for improvement; the calibration process becomes an educational opportunity for the balance user as well as calibration personnel. This paper will cover the uncertainty analysis applied to the calibration weights used for the field calibration of balances; the uncertainty is calculated over the range of environmental conditions typically encountered in the field and the resulting range of air density. The temperature stability in the area of the balance is discussed with the customer and the temperature range over which the balance calibration is valid is decided upon; the decision is based upon the uncertainty needs of the customer and the desired rigor in monitoring by the customer. Once the environmental limitations are decided, the calibration is performed and the measurement data is entered into
Gruendling, Till; Guilhaus, Michael; Barner-Kowollik, Christopher
2008-09-15
We report on the successful application of size exclusion chromatography (SEC) combined with electrospray ionization mass spectrometry (ESI-MS) and refractive index (RI) detection for the determination of accurate molecular weight distributions of synthetic polymers, corrected for chromatographic band broadening. The presented method makes use of the ability of ESI-MS to accurately depict the peak profiles and retention volumes of individual oligomers eluting from the SEC column, whereas quantitative information on the absolute concentration of oligomers is obtained from the RI-detector only. A sophisticated computational algorithm based on the maximum entropy principle is used to process the data gained by both detectors, yielding an accurate molecular weight distribution, corrected for chromatographic band broadening. Poly(methyl methacrylate) standards with molecular weights up to 10 kDa serve as model compounds. Molecular weight distributions (MWDs) obtained by the maximum entropy procedure are compared to MWDs, which were calculated by a conventional calibration of the SEC-retention time axis with peak retention data obtained from the mass spectrometer. Comparison showed that for the employed chromatographic system, distributions below 7 kDa were only weakly influenced by chromatographic band broadening. However, the maximum entropy algorithm could successfully correct the MWD of a 10 kDa standard for band broadening effects. Molecular weight averages were between 5 and 14% lower than the manufacturer stated data obtained by classical means of calibration. The presented method demonstrates a consistent approach for analyzing data obtained by coupling mass spectrometric detectors and concentration sensitive detectors to polymer liquid chromatography.
Huertas Pérez, J F; Sejerøe-Olsen, B; Fernández Alba, A R; Schimmel, H; Dabrio, M
2015-05-01
A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18 column using gradient elution with water-methanol/2.5 mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-(13)C2(15)N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005 mg kg(-1) in the matrix, while LOQs established as the lowest spiking mass fractionation level were in the range 0.01-0.05 mg kg(-1). The method reliably identifies and quantifies the
Sacks, L.A.; Swancar, Amy; Lee, T.M.
1998-01-01
Water budget and chemical mass-balance approaches were used to estimate ground-water exchange with 10 lakes in ridge areas of Polk and Highlands Counties, Florida. At each lake, heads were monitored in the surficial aquifer system and deeper Upper Floridan aquifer, lake stage and rainfall were measured continuously, and lakes and wells were sampled three times between October 1995 and December 1996. The water-budget approach computes net ground-water flow (ground-water inflow minus outflow) as the residual of the monthly waterbudget equation. Net ground-water flow varied seasonally at each of the 10 lakes, and was notably different between lakes, illustrating short-term differences in ground-water fluxes. Monthly patterns in net ground-water flow were related to monthly patterns of other hydrologic variables such as rainfall, ground-water flow patterns, and head differences between the lake and the Upper Floridan aquifer. The chemical mass-balance approach combines the water budget and solute or isotope mass-balance equations, and assumes steady-state conditions. Naturally occurring tracers that were analyzed for include calcium, magnesium, sodium, potassium, chloride, and bromide, the isotopes deuterium and oxygen-18. Chloride and sodium were the most successful solute tracers; however, their concentrations in ground water typically varied spatially, and in places were similar to that in lake water, limiting their sensitivity as tracers. In contrast, the isotopes were more robust tracers because the isotopic composition of ground water was relatively uniform and was distinctly different from the lake water. Groundwater inflow computed using the chemical massbalance method varied significantly between lakes, and ranged from less than 10 to more than 150 inches per year. Both water-budget and chemical mass-balance approaches had limitations, but the multiple lines of evidence gained using both approaches improved the understanding of the role of ground water in the
Fonteyne, Margot; Gildemyn, Delphine; Peeters, Elisabeth; Mortier, Séverine Thérèse F C; Vercruysse, Jurgen; Gernaey, Krist V; Vervaet, Chris; Remon, Jean Paul; Nopens, Ingmar; De Beer, Thomas
2014-08-01
Classically, the end point detection during fluid bed drying has been performed using indirect parameters, such as the product temperature or the humidity of the outlet drying air. This paper aims at comparing those classic methods to both in-line moisture and solid-state determination by means of Process Analytical Technology (PAT) tools (Raman and NIR spectroscopy) and a mass balance approach. The six-segmented fluid bed drying system being part of a fully continuous from-powder-to-tablet production line (ConsiGma™-25) was used for this study. A theophylline:lactose:PVP (30:67.5:2.5) blend was chosen as model formulation. For the development of the NIR-based moisture determination model, 15 calibration experiments in the fluid bed dryer were performed. Six test experiments were conducted afterwards, and the product was monitored in-line with NIR and Raman spectroscopy during drying. The results (drying endpoint and residual moisture) obtained via the NIR-based moisture determination model, the classical approach by means of indirect parameters and the mass balance model were then compared. Our conclusion is that the PAT-based method is most suited for use in a production set-up. Secondly, the different size fractions of the dried granules obtained during different experiments (fines, yield and oversized granules) were compared separately, revealing differences in both solid state of theophylline and moisture content between the different granule size fractions. Copyright © 2014 Elsevier B.V. All rights reserved.
Mukherjee, B; Nivedita, M; Mukherjee, D
2014-05-01
Modelling system dynamics in a hyper-eutrophic lake is quite complex especially with a constant influx of detergents and sewage material which continually changes the state variables and interferes with the assessment of the chemical rhythm occurring in polluted conditions as compared to unpolluted systems. In this paper, a carbon and nutrient mass balance model for predicting system dynamics in a complex environment was studied. Studies were conducted at Ranchi lake to understand the altered environmental dynamics in hyper-eutrophic conditions, and its impact on the plankton community. The lake was monitored regularly for five years (2007 - 2011) and the data collected on the carbon flux, nitrates, phosphates and silicates was used to design a mass balance model for evaluating and predicting the system. The model was then used to correlate the chemical rhythm with that of the phytoplankton dynamics and diversity. Nitrates and phosphates were not limiting (mean nitrate and phosphate concentrations were 1.74 and 0.83 mgl⁻¹ respectively). Free carbon dioxide was found to control the system and, interacting with other parameters determined the diversity and dynamics of the plankton community. N/P ratio determined which group of phytoplankton dominated the community, above 5 it favoured the growth of chlorophyceae while below 5 cyanobacteria dominates. TOC/TIC ratio determined the abundance. The overall system was controlled by the availability of free carbon dioxide which served as a limiting factor.
Schacht, E; Ringe, Johann D
2012-01-01
We investigated the effect of daily therapy with 1 mcg alfacalcidol (Doss(®)-TEVA/AWD-pharma) on muscle power, muscle function, balance performance and fear of falls in an open, multi-centered, uncontrolled, prospective study on a cohort of patients with reduced bone mass. Among the 2,097 participants, 87.1% were post-menopausal women and 12.9% were men. Mean age was 74.8 years and mean body mass index (BMI) 26.3 kg/m². A total of 75.3% of the study population had osteoporosis, 81% a diagnosis of "increased risk of falls" and 70.1% had a creatinine clearance (CrCl) of <65 ml/min. Participants underwent muscle function and muscle power tests at onset and after 3 and 6 months: the timed up and go test (TUG) and the chair rising test (CRT). At baseline and after 6 months, participants performed the tandem gait test (TGT) and filled out a questionnaire evaluating fear of falling. Successful performance in the muscle tests is associated with a significantly lower risk of falls and non-vertebral fractures in elderly patients (successful test performance: TUG ≤ 10 s (sec), CRT ≤ 10 s, TGT ≥ 8 steps). A significant improvement in the performance of the two muscle tests was proved already after 3 months of treatment with alfacalcidol and further increased by the end of the therapeutic intervention. There were significant increases in the number of participants able to successfully perform the tests: 24.6% at baseline and 46.3% at the end of trial for the TUG (P < 0.0001) and 21.7% at baseline and 44.2% at the end for the CRT test (P = 0.0001). The mean time used for the TUG was decreased by 3.0 s from the average onset value of 17.0 s and by 3.1 s from the initial average 16.5 s for the CRT. The percentage of participants able to perform the balance test (TGT) increased from 36.0% at onset to 58.6% at the end of the trial (P < 0.0001). An increased fear of falling was reduced by the end of the study in 74.4% of the patients. Throughout the study, there were 26
NASA Astrophysics Data System (ADS)
Farlin, J.; Drouet, L.; Gallé, T.; Pittois, D.; Bayerle, M.; Braun, C.; Maloszewski, P.; Vanderborght, J.; Elsner, M.; Kies, A.
2013-06-01
A simple method to delineate the recharge areas of a series of springs draining a fractured aquifer is presented. Instead of solving the flow and transport equations, the delineation is reformulated as a mass balance problem assigning arable land in proportion to the pesticide mass discharged annually in a spring at minimum total transport cost. The approach was applied to the Luxembourg Sandstone, a fractured-rock aquifer supplying half of the drinking water for Luxembourg, using the herbicide atrazine. Predictions of the recharge areas were most robust in situations of strong competition by neighbouring springs while the catchment boundaries for isolated springs were extremely sensitive to the parameter controlling flow direction. Validation using a different pesticide showed the best agreement with the simplest model used, whereas using historical crop-rotation data and spatially distributed soil-leaching data did not improve predictions. The whole approach presents the advantage of integrating objectively information on land use and pesticide concentration in spring water into the delineation of groundwater recharge zones in a fractured-rock aquifer.
Transient bright "halos" on the South Polar Residual Cap of Mars: Implications for mass-balance
NASA Astrophysics Data System (ADS)
Becerra, Patricio; Byrne, Shane; Brown, Adrian J.
2015-05-01
Spacecraft imaging of Mars' south polar region during mid-southern summer of Mars year 28 (2007) observed bright halo-like features surrounding many of the pits, scarps and slopes of the heavily eroded carbon dioxide ice of the South Polar Residual Cap (SPRC). These features had not been observed before, and have not been observed since. We report on the results of an observational study of these halos, and spectral modeling of the SPRC surface at the time of their appearance. Image analysis was performed using data from MRO's Context Camera (CTX), and High Resolution Imaging Science Experiment (HiRISE), as well as images from Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC). Data from MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) were used for the spectral analysis of the SPRC ice at the time of the halos. These data were compared with a Hapke reflectance model of the surface to constrain their formation mechanism. We find that the unique appearance of the halos is intimately linked to a near-perihelion global dust storm that occurred shortly before they were observed. The combination of vigorous summertime sublimation of carbon dioxide ice from sloped surfaces on the SPRC and simultaneous settling of dust from the global storm, resulted in a sublimation wind that deflected settling dust particles away from the edges of these slopes, keeping these areas relatively free of dust compared to the rest of the cap. The fact that the halos were not exhumed in subsequent years indicates a positive mass-balance for flat portions of the SPRC in those years. A net accumulation mass-balance on flat surfaces of the SPRC is required to preserve the cap, as it is constantly being eroded by the expansion of the pits and scarps that populate its surface.
The Thermal Circulation on Kilimanjaro, Tanzania and its Relevance to Summit Ice-Field Mass Balance.
NASA Astrophysics Data System (ADS)
Pepin, N. C.; Duane, W. J.
2008-12-01
It is well known that mountains create their own climates. On Kilimanjaro, which is the tallest free standing mountain in Africa, the intense tropical sunlight generates a strong diurnal mountain circulation which transports moisture up the mountain during the day and back downslope at night. This process has strong consequences for development of cloud cover, precipitation, and hence ice-field mass balance on the summit crater. We compare surface climate (temperature, moisture and wind) measured at ten elevations on Kilimanjaro, with equivalent observations in the free atmosphere from NCEP/NCAR reanalysis data for September 2004 to July 2008. There are no simple temporal trends over this period in either surface of free- air data. Correlations between daily surface and free air temperatures are greatest below 2500 metres, meaning that synoptic (inter-diurnal) variability is the major control here. In contrast, temperatures and moisture on the higher slopes above treeline (about 3000 m) are strongly decoupled from the free atmosphere, showing intense heating/cooling by day/night (more than 5°C). The sparsely vegetated upper slopes are the focus for the most intense heating and upslope winds develop by mid-morning. The forest on the lower slopes acts as a moisture source, with large vapour pressure excesses reported (5 mb) which move upslope reaching the crater in the afternoon before subsiding downslope at night. The montane thermal circulation is more effective at upslope moisture transport during January as compared with July. Fluctuations in upper air flow strength and direction (at 500 mb) surprisingly have limited influence on the strength of surface heating and upslope moisture advection. This finding suggests that local changes in surface characteristics such as deforestation could have a strong influence on the mountain climate and the summit ice fields on Kilimanjaro, and make mass-balance somewhat divorced from larger-scale advective changes associated
In 1997, the United States (US) Environmental Protection Agency (EPA) conducted a mass balance study of polychlorinated dibenzo-p-dioxins (CDDs) and dibenzofurans (CDFs) in lactating cows in background conditions. The field portion of the study occurred at the US Department of A...
Pilli, Sridhar; Yan, S; Tyagi, R D; Surampalli, R Y
2016-01-15
Two cases of anaerobic digestion (AD) of sludge, namely (i) with pre-treatment and (ii) without pre-treatment, were assessed using mass-energy balance and the corresponding greenhouse gas (GHG) emissions. For a digestion period of 30 days, volatile solids degradation of the control sludge and the ultrasonicated secondary sludge was 51.4% and 60.1%, respectively. Mass balance revealed that the quantity of digestate required for dewatering, transport and land application was the lowest (20.2 × 10(6) g dry sludge/day) for ultrasonicated secondary sludge at 31.4 g TS/L. Furthermore, for ultrasonicated secondary sludge at 31.4 g TS/L, the maximum net energy (energy output - energy input) of total dry solids (TDS) was 7.89 × 10(-6) kWh/g and the energy ratio (output/input) was 1.0. GHG emissions were also reduced with an increase in the sludge solids concentration (i.e., 40.0 g TS/L < 30.0 g TS/L < 20.0 g TS/L). Ultrasonication pre-treatment proved to be efficient and beneficial for enhancing anaerobic digestion efficiency of the secondary sludge when compared to the primary and mixed sludge. Copyright © 2015 Elsevier Ltd. All rights reserved.
Han, Young-Soo; Tokunaga, Tetsu K
2014-12-01
Renewed interest in managing C balance in soils is motivated by increasing atmospheric concentrations of CO2 and consequent climate change. Here, experiments were conducted in soil columns to determine C mass balances with and without addition of CaSO4-minerals (anhydrite and gypsum), which were hypothesized to promote soil organic carbon (SOC) retention and soil inorganic carbon (SIC) precipitation as calcite under slightly alkaline conditions. Changes in C contents in three phases (gas, liquid and solid) were measured in unsaturated soil columns tested for one year and comprehensive C mass balances were determined. The tested soil columns had no C inputs, and only C utilization by microbial activity and C transformations were assumed in the C chemistry. The measurements showed that changes in C inventories occurred through two processes, SOC loss and SIC gain. However, the measured SOC losses in the treated columns were lower than their corresponding control columns, indicating that the amendments promoted SOC retention. The SOC losses resulted mostly from microbial respiration and loss of CO2 to the atmosphere rather than from chemical leaching. Microbial oxidation of SOC appears to have been suppressed by increased Ca(2+) and SO4(2)(-) from dissolution of CaSO4 minerals. For the conditions tested, SIC accumulation per m(2) soil area under CaSO4-treatment ranged from 130 to 260 g C m(-1) infiltrated water (20-120 g C m(-1) infiltrated water as net C benefit). These results demonstrate the potential for increasing C sequestration in slightly alkaline soils via CaSO4-treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wilton, David J.; Jowett, Amy; Hanna, Edward
Here, we show results from a positive degree-day (PDD) model of Greenland ice sheet (GrIS) surface mass balance (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB:more » mean 1979–2012 SMB (± standard deviation), in Gt a –1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s.« less
Wilton, David J.; Jowett, Amy; Hanna, Edward; ...
2016-12-15
Here, we show results from a positive degree-day (PDD) model of Greenland ice sheet (GrIS) surface mass balance (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB:more » mean 1979–2012 SMB (± standard deviation), in Gt a –1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s.« less
Pilli, Sridhar; More, Tanaji; Yan, Song; Tyagi, Rajeshwar Dayal; Surampalli, Rao Y
2015-07-01
The effect of thermal pre-treatment on sludge anaerobic digestion (AD) efficiency was studied at different total solids (TS) concentrations (20.0, 30.0 and 40.0 g TS/L) and digestion times (0, 5, 10, 15, 20 and 30 days) for primary, secondary and mixed wastewater sludge. Moreover, sludge pre-treatment, AD and disposal processes were evaluated based on a mass-energy balance and corresponding greenhouse gas (GHG) emissions. Mass balance revealed that the least quantity of digestate was generated by thermal pre-treated secondary sludge at 30.0 g TS/L. The net energy (energy output-energy input) and energy ratio (energy output/energy input) for thermal pre-treated sludge was greater than control in all cases. The reduced GHG emissions of 73.8 × 10(-3) g CO2/g of total dry solids were observed for the thermal pre-treated secondary sludge at 30.0 g TS/L. Thermal pre-treatment of sludge is energetically beneficial and required less retention time compared to control. Copyright © 2015 Elsevier Ltd. All rights reserved.
Most compounds are not found in mass spectral libraries and must be identified by other means. Often, compound identities can be deduced from the compositions of the ions in their mass spectra and review of the chemical literature. Confirmation is provided by mass spectra and r...
NASA Astrophysics Data System (ADS)
Plach, Andreas; Hestnes Nisancioglu, Kerim
2016-04-01
The contribution from the Greenland Ice Sheet (GIS) to the global sea level rise during the Eemian interglacial (about 125,000 year ago) was the focus of many studies in the past. A main reason for the interest in this period is the considerable warmer climate during the Eemian which is often seen as an equivalent for possible future climate conditions. Simulated sea level rise during the Eemian can therefore be used to better understand a possible future sea level rise. The most recent assessment report of the Intergovernmental Panel on Climate Change (IPCC AR5) gives an overview of several studies and discusses the possible implications for a future sea level rise. The report also reveals the big differences between these studies in terms of simulated GIS extent and corresponding sea level rise. The present study gives a more exhaustive review of previous work discussing sea level rise from the GIS during the Eemian interglacial. The smallest extents of the GIS simulated by various authors are shown and summarized. A focus is thereby given to the methods used to calculate the surface mass balance. A hypothesis of the present work is that the varying results of the previous studies can largely be explained due to the various methods used to calculate the surface mass balance. In addition, as a first step for future work, the surface mass balance of the GIS for a proxy-data derived forcing ("index method") and a direct forcing with a General Circulation Model (GCM) are shown and discussed.
Mercury mass balance study in Wujiangdu and Dongfeng Reservoirs, Guizhou, China.
Feng, Xinbin; Jiang, Hongmei; Qiu, Guangle; Yan, Haiyu; Li, Guanghui; Li, Zhonggen
2009-10-01
From October 2003 to September 2004, we conducted a detailed study on the mass balance of total mercury (THg) and methylmercury (MeHg) of Dongfeng (DF) and Wujiangdu (WJD) reservoirs, which were constructed in 1992 and 1979, respectively. Both reservoirs were net sinks for THg on an annual scale, absorbing 3319.5 g km(-2) for DF Reservoir, and 489.2 g km(-2) for WJD Reservoirs, respectively. However, both reservoirs were net sources of MeHg to the downstream ecosystems. DF Reservoir provided a source of 32.9 g MeHg km(-2) yr(-1), yielding 10.3% of the amount of MeHg that entered the reservoir, and WJD Reservoir provided 140.9 g MeHg km(-2) yr(-1), yielding 82.5% of MeHg inputs. Our results implied that water residence time is an important variable affecting Hg methylation rate in the reservoirs. Our study shows that building a series of reservoirs in line along a river changes the riverine system into a natural Hg methylation factory which markedly increases the %MeHg in the downstream reservoirs; in effect magnifying the MeHg buildup problem in reservoirs.
NASA Technical Reports Server (NTRS)
Thompson, Bryan
2000-01-01
This is the final report for a project carried out to modify a manual commercial Cavendish Balance for automated use in cryostat. The scope of this project was to modify an off-the-shelf manually operated Cavendish Balance to allow for automated operation for periods of hours or days in cryostat. The purpose of this modification was to allow the balance to be used in the study of effects of superconducting materials on the local gravitational field strength to determine if the strength of gravitational fields can be reduced. A Cavendish Balance was chosen because it is a fairly simple piece of equipment for measuring gravity, one the least accurately known and least understood physical constants. The principle activities that occurred under this purchase order were: (1) All the components necessary to hold and automate the Cavendish Balance in a cryostat were designed. Engineering drawings were made of custom parts to be fabricated, other off-the-shelf parts were procured; (2) Software was written in LabView to control the automation process via a stepper motor controller and stepper motor, and to collect data from the balance during testing; (3)Software was written to take the data collected from the Cavendish Balance and reduce it to give a value for the gravitational constant; (4) The components of the system were assembled and fitted to a cryostat. Also the LabView hardware including the control computer, stepper motor driver, data collection boards, and necessary cabling were assembled; and (5) The system was operated for a number of periods, data collected, and reduced to give an average value for the gravitational constant.
The mass balance of soil evolution on late Quaternary marine terraces, northern California
NASA Technical Reports Server (NTRS)
Merritts, Dorothy J.; Chadwick, Oliver A.; Hendricks, David M.; Brimhall, George H.; Lewis, Christopher J.
1992-01-01
Mass-balance interpretation of a soil chronosequence provides a means of quantifying elemental addition, removal, and transformation that occur in soils from a flight of marine terraces in northern California. Six soil profiles that range in age from several to 240,000 yr are developed in unconsolidated, sandy-marine, and eolian parent material deposited on bedrock marine platforms. Soil evolution is dominated by (1) open-system depletion of Si, Ca, Mg, K, and Na; (2) open-system enrichment of P in surface soil horizons; (3) relative immobility of Fe and Al; and (4) transformation of Fe, Si, and Al in the parent material to secondary clay minerals and sesquioxides. Net mass losses of bases and Si are generally uniform with depth and substantial, in some cases approaching 100 percent; however, the rate of loss of each element differs markedly, causing the ranking of each by relative abundance to shift with time. Loss of Si from the sand fraction by dissolution and particle-size diminution, from about 100 percent to less than 35 percent over 240 ky, mirrors a similar gain in the silt and clay size fractions. The Fe originally present in the sand fraction decreases from greater than 80 percent to less than 10 percent, whereas the amount of Fe present in the clay and crystalline oxyhydroxide fractions increases to 25 percent and 70 percent, respectively.
Li, Jian-Xun; Li, Xiao-Ying; Chang, Qiao-Ying; Li, Yan; Jin, Ling-He; Pang, Guo-Fang; Fan, Chun-Lin
2018-05-03
Because of its unique characteristics of accurate mass full-spectrum acquisition, high resolution, and fast acquisition rates, GC-quadrupole-time-of-flight MS (GC-Q-TOF/MS) has become a powerful tool for pesticide residue analysis. In this study, a TOF accurate mass database and Q-TOF spectrum library of 439 pesticides were established, and the parameters of the TOF database were optimized. Through solid-phase extraction (SPE), whereby pesticides are extracted from fruit and vegetable substrates by using 40 mL 1% acetic acid in acetonitrile (v/v), purified by the Carbon/NH₂ SPE cartridge, and finally detected by GC-Q-TOF/MS, the rapid analysis of 439 pesticides in fruits and vegetables can be achieved. The methodology verification results show that more than 70 and 91% of pesticides, spiked in fruits and vegetables with concentrations of 10 and 100 μg/kg, respectively, saw recoveries that conform to the European Commission's criterion of between 70 and 120% with RSD ≤20%. Eighty-one percent of pesticides have screening detection limits lower than 10 μg/kg, which makes this a reliable analysis technology for the monitoring of pesticide residues in fruits and vegetables. This technology was further validated for its characteristics of high precision, high speed, and high throughput through successful detection of 9817 samples during 2013-2015.
NASA Astrophysics Data System (ADS)
Windmiller, G.; Orosz, J. A.; Etzel, P. B.
2010-04-01
GU Boo is one of only a relatively small number of well-studied double-lined eclipsing binaries that contain low-mass stars. López-Morales & Ribas present a comprehensive analysis of multi-color light and radial velocity curves for this system. The GU Boo light curves presented by López-Morales & Ribas had substantial asymmetries, which were attributed to large spots. In spite of the asymmetry, López-Morales & Ribas derived masses and radii accurate to sime2%. We obtained additional photometry of GU Boo using both a CCD and a single-channel photometer and modeled the light curves with the ELC software to determine if the large spots in the light curves give rise to systematic errors at the few percent level. We also modeled the original light curves from the work of López-Morales & Ribas using models with and without spots. We derived a radius of the primary of 0.6329 ± 0.0026 R sun, 0.6413 ± 0.0049 R sun, and 0.6373 ± 0.0029 R sun from the CCD, photoelectric, and López-Morales & Ribas data, respectively. Each of these measurements agrees with the value reported by López-Morales & Ribas (R 1 = 0.623 ± 0.016 R sun) at the level of ≈2%. In addition, the spread in these values is ≈1%-2% from the mean. For the secondary, we derive radii of 0.6074 ± 0.0035 R sun, 0.5944 ± 0.0069 R sun, and 0.5976 ± 0.0059 R sun from the three respective data sets. The López-Morales & Ribas value is R 2 = 0.620 ± 0.020 R sun, which is ≈2%-3% larger than each of the three values we found. The spread in these values is ≈2% from the mean. The systematic difference between our three determinations of the secondary radius and that of López-Morales & Ribas might be attributed to differences in the modeling process and codes used. Our own fits suggest that, for GU Boo at least, using accurate spot modeling of a single set of multi-color light curves results in radii determinations accurate at the ≈2% level.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Windmiller, G.; Orosz, J. A.; Etzel, P. B., E-mail: windmill@rohan.sdsu.ed, E-mail: orosz@sciences.sdsu.ed, E-mail: etzel@sciences.sdsu.ed
2010-04-01
GU Boo is one of only a relatively small number of well-studied double-lined eclipsing binaries that contain low-mass stars. Lopez-Morales and Ribas present a comprehensive analysis of multi-color light and radial velocity curves for this system. The GU Boo light curves presented by Lopez-Morales and Ribas had substantial asymmetries, which were attributed to large spots. In spite of the asymmetry, Lopez-Morales and Ribas derived masses and radii accurate to {approx_equal}2%. We obtained additional photometry of GU Boo using both a CCD and a single-channel photometer and modeled the light curves with the ELC software to determine if the large spotsmore » in the light curves give rise to systematic errors at the few percent level. We also modeled the original light curves from the work of Lopez-Morales and Ribas using models with and without spots. We derived a radius of the primary of 0.6329 +- 0.0026 R{sub sun}, 0.6413 +- 0.0049 R{sub sun}, and 0.6373 +- 0.0029 R{sub sun} from the CCD, photoelectric, and Lopez-Morales and Ribas data, respectively. Each of these measurements agrees with the value reported by Lopez-Morales and Ribas (R{sub 1} = 0.623 +- 0.016 R{sub sun}) at the level of {approx}2%. In addition, the spread in these values is {approx}1%-2% from the mean. For the secondary, we derive radii of 0.6074 +- 0.0035 R{sub sun}, 0.5944 +- 0.0069 R{sub sun}, and 0.5976 +- 0.0059 R{sub sun} from the three respective data sets. The Lopez-Morales and Ribas value is R{sub 2} = 0.620 +- 0.020 R{sub sun}, which is {approx}2%-3% larger than each of the three values we found. The spread in these values is {approx}2% from the mean. The systematic difference between our three determinations of the secondary radius and that of Lopez-Morales and Ribas might be attributed to differences in the modeling process and codes used. Our own fits suggest that, for GU Boo at least, using accurate spot modeling of a single set of multi-color light curves results in radii
Rapid glucosinolate detection and identification using accurate mass MS-MS
USDA-ARS?s Scientific Manuscript database
Currently, there is a demand for accurate evaluation of brassica plat species for their glucosinolate content. An optimized method has been developed for detecting and identifying glucosinolates in plant extracts using MS-MS fragmentation with ion trap collision induced dissociation (CID) and higher...
GIA models with composite rheology and 3D viscosity: effect on GRACE mass balance in Antarctica
NASA Astrophysics Data System (ADS)
van der Wal, Wouter; Whitehouse, Pippa; Schrama, Ernst
2014-05-01
Most Glacial Isostatic Adjustment (GIA) models that have been used to correct GRACE data for the influence of GIA assume a radial stratification of viscosity in the Earth's mantle (1D viscosity). Seismic data in Antarctica indicate that there are large viscosity variations in the horizontal direction (3D viscosity). The purpose of this research is to determine the effect of 3D viscosity on GIA model output, and hence mass balance estimates in Antarctica. We use a GIA model with 3D viscosity and composite rheology in combination with ice loading histories ICE-5G and W12a. From comparisons with uplift and sea-level data in Fennoscandia and North America three preferred viscosity models are selected. For two of the 3D viscosity models the maximum gravity rate due to ICE-5G forcing is located over the Ronne-Filchner ice shelf. This is in contrast with the results obtained using a 1D model, in which the maximum gravity rate due to ICE-5G forcing is always located over the Ross ice shelf. This demonstrates that not all 3D viscosity models can be approximated with a 1D viscosity model. Using CSR release 5 GRACE data from February 2003 to June 2013 mass balance estimates for the three preferred viscosity models are -131 to -171 Gt/year for the ICE-5G model, and -48 to -57 Gt/year for the W12a model. The range due to Earth model uncertainty is larger than the error bar for GRACE (10 Gt/year), but smaller than the range resulting from the difference in ice loading histories.
How Well do we Know Near-Surface Density When Determining Mass Balance by the Geodetic Method?
NASA Astrophysics Data System (ADS)
Kuhn, M. H.; Matzi, E.
2005-12-01
From a data set of firn pits in the accumulation area of Hintereisferner in the years 1964 - 2002 the behavior of density and water equivalent was analyzed with a view to estimating the potential errors in the application of the geodetic method. Since annual specific balance ranged from 100 to 3300 mm w.e. the profiles were scaled to total depth. For the uppermost 10% of the annual deposit at a typical location the 1964-2002 mean density would be 350 kg/m-3 with a standard deviation of 110 kg/m-3; for the 10% layer at the base of the annual snowpack the respective figures are 510 +- 30 kg/m-3. The normalized long term means of an ensemble of 9 pits ranged from 310 to 380 kg/m-3 in the top layer and from 510 to 540 kg/m-3 in the bottom layer. When one outlier is removed the the range in the bottom layer reduces to 525 to 540 kg/m-3. This small local variance encourages the use of the geodetic method. The comparison of elevation models of 1969 and 1997 yields a mass change that agrees very well with the results of the glaciological method provided the volume change is converted to mass with a density of 900 kg/m-3. While this may be true for the entire glacier on long terms, it will fail for individual years in the accumulation area. Possible errors are calculated from the data set emphasizing the role of year to year changes of specific balance and accumulation area ratio.
Biogeochemical phosphorus mass balance for Lake Baikal, southeastern Siberia, Russia
Callender, E.; Granina, L.
1997-01-01
Extensive data for Lake Baikal have been synthesized into a geochemical mass balance for phosphorus (P). Some of the P budget and internal cycling terms for Baikal have been compared to similar terms for oligotrophic Lake Superior, mesotrophic Lake Michigan and the Baltic Sea, and the Ocean. Lake Baikal has a large external source of fluvial P compared to the Laurentian upper Great Lakes and the Ocean. The major tributary to Lake Baikal has experienced substantial increases in organic P loading during the past 25 years. This, coupled with potential P inputs from possible phosphorite mining, may threaten Baikal's oligotrophic status in the future. Water-column remineralization of particulate organic P is substantially greater in Lake Baikal than in the Laurentian Great Lakes. This is probably due to the great water depths of Lake Baikal. There is a gradient in P burial efficiency, with very high values (80%) for Lake Baikal and Lake Superior, lower values (50%) for Lake Michigan and the Baltic Sea, and a low value (13%) for the Ocean. The accumulation rate of P in Lake Baikal sediments is somewhat greater than that in the Laurentian upper Great Lakes and the Baltic Sea, and much greater than in the Ocean. Benthic regeneration rates are surprisingly similar for large lacustrine and marine environments and supply less than 10% of the P utilized for primary production in these aquatic environments.
NASA Astrophysics Data System (ADS)
Hunter, William Ross; Van Oevelen, Dick; Witte, Ursula
2013-04-01
Over 1 million km2 of seafloor experience permanent low-oxygen conditions within oxygen minimum zones (OMZs). OMZs are predicted to grow as a consequence of climate change, potentially affecting oceanic biogeochemical cycles. The Arabian Sea OMZ impinges upon the western Indian continental margin at bathyal depths (150 - 1500m) producing a strong depth dependent oxygen gradient at the sea floor. The influence of the OMZ upon the short term processing of organic matter by sediment ecosystems was investigated using in situ stable isotope pulse chase experiments. These deployed doses of 13C:15N labeled organic matter onto the sediment surface at four stations from across the OMZ (water depth 540 - 1100 m; [O2] = 0.35 - 15 μM). In order to prevent experimentally anoxia, the mesocosms were not sealed. 13C and 15N labels were traced into sediment, bacteria, fauna and 13C into sediment porewater DIC and DOC. However, the DIC and DOC flux to the water column could not be measured, limiting our capacity to obtain mass-balance for C in each experimental mesocosm. Linear Inverse Modeling (LIM) provides a method to obtain a mass-balanced model of carbon flow that integrates stable-isotope tracer data with community biomass and biogeochemical flux data from a range of sources. Here we present an adaptation of the LIM methodology used to investigate how ecosystem structure influenced carbon flow across the Indian margin OMZ. We demonstrate how oxygen conditions affect food-web complexity, affecting the linkages between the bacteria, foraminifera and metazoan fauna, and their contributions to benthic respiration. The food-web models demonstrate how changes in ecosystem complexity are associated with oxygen availability across the OMZ and allow us to obtain a complete carbon budget for the stationa where stable-isotope labelling experiments were conducted.
Davies, Stephen R; Alamgir, Mahiuddin; Chan, Benjamin K H; Dang, Thao; Jones, Kai; Krishnaswami, Maya; Luo, Yawen; Mitchell, Peter S R; Moawad, Michael; Swan, Hilton; Tarrant, Greg J
2015-10-01
The purity determination of organic calibration standards using the traditional mass balance approach is described. Demonstrated examples highlight the potential for bias in each measurement and the need to implement an approach that provides a cross-check for each result, affording fit for purpose purity values in a timely and cost-effective manner. Chromatographic techniques such as gas chromatography with flame ionisation detection (GC-FID) and high-performance liquid chromatography with UV detection (HPLC-UV), combined with mass and NMR spectroscopy, provide a detailed impurity profile allowing an efficient conversion of chromatographic peak areas into relative mass fractions, generally avoiding the need to calibrate each impurity present. For samples analysed by GC-FID, a conservative measurement uncertainty budget is described, including a component to cover potential variations in the response of each unidentified impurity. An alternative approach is also detailed in which extensive purification eliminates the detector response factor issue, facilitating the certification of a super-pure calibration standard which can be used to quantify the main component in less-pure candidate materials. This latter approach is particularly useful when applying HPLC analysis with UV detection. Key to the success of this approach is the application of both qualitative and quantitative (1)H NMR spectroscopy.
History and progress on accurate measurements of the Planck constant
NASA Astrophysics Data System (ADS)
Steiner, Richard
2013-01-01
The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10-34 J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, NA. As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 108 from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved
Payn, R.A.; Gooseff, M.N.; McGlynn, B.L.; Bencala, K.E.; Wondzell, S.M.
2009-01-01
Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6 km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively high, intermediate, and low base flow conditions. The relative distribution of channel water along the stream was strongly related to a transition in valley structure, with a general increase in gross losses through the recession. During tracer tests at intermediate and low flows, there were frequent substantial losses of tracer mass (>10%) that could not be explained by net loss in flow over the reach, indicating that many of the study reaches were concurrently losing and gaining water. For example, one reach with little net change in discharge exchanged nearly 20% of upstream flow with gains and losses along the reach. These substantial bidirectional exchanges suggest that some channel interactions with subsurface flow paths were not measurable by net change in flow or transient storage of recovered tracer. Understanding bidirectional channel water balances in stream reaches along valleys is critical to an accurate assessment of stream solute fate and transport and to a full assessment of exchanges between the stream channel and surrounding subsurface.
Payn, R.A.; Gooseff, M.N.; McGlynn, B.L.; Bencala, K.E.; Wondzell, S.M.
2009-01-01
Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6 km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively high, intermediate, and low base flow conditions. The relative distribution of channel water along the stream was strongly related to a transition in valley structure, with a general increase in gross losses through the recession. During tracer tests at intermediate and low flows, there were frequent substantial losses of tracer mass (>10%) that could not be explained by net loss in flow over the reach, indicating that many of the study reaches were concurrently losing and gaining water. For example, one reach with little net change in discharge exchanged nearly 20% of upstream flow with gains and losses along the reach. These substantial bidirectional exchanges suggest that some channel interactions with subsurface flow paths were not measurable by net change in flow or transient storage of recovered tracer. Understanding bidirectional channel water balances in stream reaches along valleys is critical to an accurate assessment of stream solute fate and transport and to a full assessment of exchanges between the stream channel and surrounding subsurface. Copyright 2009 by the American Geophysical Union.
Wood, W.W.; Sanford, W.E.
2007-01-01
A solute mass-balance study of ground water of the 3000 km2 coastal sabkhat (salt flats) of the Emirate of Abu Dhabi, United Arab Emirates, documents an annual bromide loss of approximately 255 metric tons (0.0032 Gmoles), or 85 kg/km2. This value is an order of magnitude greater than previously published direct measurements from the atmosphere over an evaporative environment of a salar in Bolivia. Laboratory evidence, consistent with published reports, suggests that this loss is by vapor transport to the atmosphere. If this bromine flux to the atmosphere is representative of the total earth area of active salt flats then it is a significant, and generally under recognized, input to the global atmospheric bromide flux.
Draper, John; Enot, David P; Parker, David; Beckmann, Manfred; Snowdon, Stuart; Lin, Wanchang; Zubair, Hassan
2009-01-01
Background Metabolomics experiments using Mass Spectrometry (MS) technology measure the mass to charge ratio (m/z) and intensity of ionised molecules in crude extracts of complex biological samples to generate high dimensional metabolite 'fingerprint' or metabolite 'profile' data. High resolution MS instruments perform routinely with a mass accuracy of < 5 ppm (parts per million) thus providing potentially a direct method for signal putative annotation using databases containing metabolite mass information. Most database interfaces support only simple queries with the default assumption that molecules either gain or lose a single proton when ionised. In reality the annotation process is confounded by the fact that many ionisation products will be not only molecular isotopes but also salt/solvent adducts and neutral loss fragments of original metabolites. This report describes an annotation strategy that will allow searching based on all potential ionisation products predicted to form during electrospray ionisation (ESI). Results Metabolite 'structures' harvested from publicly accessible databases were converted into a common format to generate a comprehensive archive in MZedDB. 'Rules' were derived from chemical information that allowed MZedDB to generate a list of adducts and neutral loss fragments putatively able to form for each structure and calculate, on the fly, the exact molecular weight of every potential ionisation product to provide targets for annotation searches based on accurate mass. We demonstrate that data matrices representing populations of ionisation products generated from different biological matrices contain a large proportion (sometimes > 50%) of molecular isotopes, salt adducts and neutral loss fragments. Correlation analysis of ESI-MS data features confirmed the predicted relationships of m/z signals. An integrated isotope enumerator in MZedDB allowed verification of exact isotopic pattern distributions to corroborate experimental data
Kappelmann, Jannick; Klein, Bianca; Geilenkirchen, Petra; Noack, Stephan
2017-03-01
In recent years the benefit of measuring positionally resolved 13 C-labeling enrichment from tandem mass spectrometry (MS/MS) collisional fragments for improved precision of 13 C-Metabolic Flux Analysis ( 13 C-MFA) has become evident. However, the usage of positional labeling information for 13 C-MFA faces two challenges: (1) The mass spectrometric acquisition of a large number of potentially interfering mass transitions may hamper accuracy and sensitivity. (2) The positional identity of carbon atoms of product ions needs to be known. The present contribution addresses the latter challenge by deducing the maximal positional labeling information contained in LC-ESI-MS/MS spectra of product anions of central metabolism as well as product cations of amino acids. For this purpose, we draw on accurate mass spectrometry, selectively labeled standards, and published fragmentation pathways to structurally annotate all dominant mass peaks of a large collection of metabolites, some of which with a complete fragmentation pathway. Compiling all available information, we arrive at the most detailed map of carbon atom fate of LC-ESI-MS/MS collisional fragments yet, comprising 170 intense and structurally annotated product ions with unique carbon origin from 76 precursor ions of 72 metabolites. Our 13 C-data proof that heuristic fragmentation rules often fail to yield correct fragment structures and we expose common pitfalls in the structural annotation of product ions. We show that the positionally resolved 13 C-label information contained in the product ions that we structurally annotated allows to infer the entire isotopomer distribution of several central metabolism intermediates, which is experimentally demonstrated for malate using quadrupole-time-of-flight MS technology. Finally, the inclusion of the label information from a subset of these fragments improves flux precision in a Corynebacterium glutamicum model of the central carbon metabolism.
Accurate and precise determination of isotopic ratios by MC-ICP-MS: a review.
Yang, Lu
2009-01-01
For many decades the accurate and precise determination of isotope ratios has remained a very strong interest to many researchers due to its important applications in earth, environmental, biological, archeological, and medical sciences. Traditionally, thermal ionization mass spectrometry (TIMS) has been the technique of choice for achieving the highest accuracy and precision. However, recent developments in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) have brought a new dimension to this field. In addition to its simple and robust sample introduction, high sample throughput, and high mass resolution, the flat-topped peaks generated by this technique provide for accurate and precise determination of isotope ratios with precision reaching 0.001%, comparable to that achieved with TIMS. These features, in combination with the ability of the ICP source to ionize nearly all elements in the periodic table, have resulted in an increased use of MC-ICP-MS for such measurements in various sample matrices. To determine accurate and precise isotope ratios with MC-ICP-MS, utmost care must be exercised during sample preparation, optimization of the instrument, and mass bias corrections. Unfortunately, there are inconsistencies and errors evident in many MC-ICP-MS publications, including errors in mass bias correction models. This review examines "state-of-the-art" methodologies presented in the literature for achievement of precise and accurate determinations of isotope ratios by MC-ICP-MS. Some general rules for such accurate and precise measurements are suggested, and calculations of combined uncertainty of the data using a few common mass bias correction models are outlined.
da Silveira, Raquel Pinhão; Rodrigues, Ana Paula de Castro; Santelli, Ricardo Erthal; Cordeiro, Renato Campello; Bidone, Edison Dausacker
2011-10-01
This study addressed the identification and monitoring of pollution sources of terrestrial origin in rivers (domestic sewage and industrial effluents) and critical fluvial segments in highly polluted environments under tidal influence (mixing marine and continental sources) from Guanabara Bay Basin, Rio de Janeiro, Brazil. The mass balance of contaminants was determined in conditions of continuous flow (low tide) during dry season (lower dilution capability). The results allowed the evaluation of the potential of contaminant mass generation by the different river segments and the estimation of their natural and anthropogenic components. The water quality of Iguaçú and Sarapuí Rivers were evaluated for metals and biochemical oxygen demand. The method gave an excellent response, including the possibility of sources identification and contaminated river segments ranking. The approach also offers fast execution and data interpretation, being highly efficient.
Rapid Weight Loss and the Body Fluid Balance and Hemoglobin Mass of Elite Amateur Boxers
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
NASA Astrophysics Data System (ADS)
Galos, Stephan; Hofer, Marlis; Marzeion, Ben; Mölg, Thomas; Großhauser, Martin
2013-04-01
Due to their setting, tropical glaciers are sensitive indicators of mid-tropospheric meteorological variability and climate change. Furthermore these glaciers are of particular interest because they respond faster to climatic changes than glaciers located in mid- or high-latitudes. As long-term direct meteorological measurements in such remote environments are scarce, reanalysis data (e.g. ERA-Interim) provide a highly valuable source of information. Reanalysis datasets (i) enable a temporal extension of data records gained by direct measurements and (ii) provide information from regions where direct measurements are not available. In order to properly derive the physical exchange processes between glaciers and atmosphere from reanalysis data, downscaling procedures are required. In the present study we investigate if downscaled atmospheric variables (air temperature and relative humidity) from a reanalysis dataset can be used as input for a physically based, high resolution energy and mass balance model. We apply a well validated empirical-statistical downscaling model, fed with ERA-Interim data, to an automated weather station (AWS) on the surface of Glaciar Artesonraju (8.96° S | 77.63° W). The downscaled data is then used to replace measured air temperature and relative humidity in the input for the energy and mass balance model, which was calibrated using ablation data from stakes and a sonic ranger. In order to test the sensitivity of the modeled mass balance to the downscaled data, the results are compared to a reference model run driven solely with AWS data as model input. We finally discuss the results and present future perspectives for further developing this method.
Liquid-circulating garment controls thermal balance
NASA Technical Reports Server (NTRS)
Kuznetz, L. H.
1977-01-01
Experimental data and mathematical model of human thermoregulatory system have been used to investigate use of liquid-circulatory garment (LCG) to control thermal balance. Model proved useful as accurate simulator of such variables as sweat rate, skin temperature, core temperature, and radiative, evaporative, and LCG heat loss.