Lateral water flux in the unsaturated zone: A mechanism for the formation of spatial soil heterogeneity in a headwater catchment

Science.gov (United States)

John P. Gannon; Kevin J. McGuire; Scott W. Bailey; Rebecca R. Bourgault; Donald S. Ross

2017-01-01

Measurements of soil water potential and water table fluctuations suggest that morphologically distinct soils in a headwater catchment at the Hubbard Brook Experimental Forest in New Hampshire formed as a result of variations in saturated and unsaturated hydrologic fluxes in the mineral soil. Previous work showed that each group of these soils had distinct water table...

Abstracts of the symposium on unsaturated flow and transport modeling

International Nuclear Information System (INIS)

1982-03-01

Abstract titles are: Recent developments in modeling variably saturated flow and transport; Unsaturated flow modeling as applied to field problems; Coupled heat and moisture transport in unsaturated soils; Influence of climatic parameters on movement of radionuclides in a multilayered saturated-unsaturated media; Modeling water and solute transport in soil containing roots; Simulation of consolidation in partially saturated soil materials; modeling of water and solute transport in unsaturated heterogeneous fields; Fluid dynamics and mass transfer in variably-saturated porous media; Solute transport through soils; One-dimensional analytical transport modeling; Convective transport of ideal tracers in unsaturated soils; Chemical transport in macropore-mesopore media under partially saturated conditions; Influence of the tension-saturated zone on contaminant migration in shallow water regimes; Influence of the spatial distribution of velocities in porous media on the form of solute transport; Stochastic vs deterministic models for solute movement in the field; and Stochastic analysis of flow and solute transport

Visualization of microscale phase displacement proceses in retention and outflow experiments: nonuniquensess of unsaturated flow properties

DEFF Research Database (Denmark)

Mortensen, Annette Pia; Glass, R.J.; Hollenbeck, K.J.

2001-01-01

-scale heterogeneities. Because the mixture of these microscale processes yields macroscale effective behavior, measured unsaturated flow properties are also a function of these controls. Such results suggest limitations on the current definitions and uniqueness of unsaturated hydraulic properties....

An integrated QSAR-PBK/D modelling approach for predicting detoxification and DNA adduct formation of 18 acyclic food-borne α,β-unsaturated aldehydes

Energy Technology Data Exchange (ETDEWEB)

Kiwamoto, R., E-mail: reiko.kiwamoto@wur.nl; Spenkelink, A.; Rietjens, I.M.C.M.; Punt, A.

2015-01-01

Acyclic α,β-unsaturated aldehydes present in food raise a concern because the α,β-unsaturated aldehyde moiety is considered a structural alert for genotoxicity. However, controversy remains on whether in vivo at realistic dietary exposure DNA adduct formation is significant. The aim of the present study was to develop physiologically based kinetic/dynamic (PBK/D) models to examine dose-dependent detoxification and DNA adduct formation of a group of 18 food-borne acyclic α,β-unsaturated aldehydes without 2- or 3-alkylation, and with no more than one conjugated double bond. Parameters for the PBK/D models were obtained using quantitative structure–activity relationships (QSARs) defined with a training set of six selected aldehydes. Using the QSARs, PBK/D models for the other 12 aldehydes were defined. Results revealed that DNA adduct formation in the liver increases with decreasing bulkiness of the molecule especially due to less efficient detoxification. 2-Propenal (acrolein) was identified to induce the highest DNA adduct levels. At realistic dietary intake, the predicted DNA adduct levels for all aldehydes were two orders of magnitude lower than endogenous background levels observed in disease free human liver, suggesting that for all 18 aldehydes DNA adduct formation is negligible at the relevant levels of dietary intake. The present study provides a proof of principle for the use of QSAR-based PBK/D modelling to facilitate group evaluations and read-across in risk assessment. - Highlights: • Physiologically based in silico models were made for 18 α,β-unsaturated aldehydes. • Kinetic parameters were determined by in vitro incubations and a QSAR approach. • DNA adduct formation was negligible at levels relevant for dietary intake. • The use of QSAR-based PBK/D modelling facilitates group evaluations and read-across.

Numerical experiments on the probability of seepage into underground openings in heterogeneous fractured rock

International Nuclear Information System (INIS)

Birkholzer, J.; Li, G.; Tsang, C.F.; Tsang, Y.

1998-01-01

An important issue for the performance of underground nuclear waste repositories is the rate of seepage into the waste emplacement drifts. A prediction of this rate is particularly complicated for the potential repository site at Yucca Mountain, Nevada, because it is located in thick, unsaturated, fractured tuff formations. Underground opening in unsaturated media might act as capillary barriers, diverting water around them. In the present work, they study the potential rate of seepage into drifts as a function of the percolation flux at Yucca Mountain, based on a stochastic model of the fractured rock mass in the drift vicinity. A variety of flow scenarios are considered, assuming present-day and possible future climate conditions. They show that the heterogeneity in the flow domain is a key factor controlling seepage rates, since it causes channelized flow and local ponding in the unsaturated flow field

Unsaturated glycerophospholipids mediate heme crystallization: biological implications for hemozoin formation in the kissing bug Rhodnius prolixus.

Directory of Open Access Journals (Sweden)

Renata Stiebler

Full Text Available Hemozoin (Hz is a heme crystal produced by some blood-feeding organisms, as an efficient way to detoxify heme derived from hemoglobin digestion. In the triatomine insect Rhodnius prolixus, Hz is essentially produced by midgut extracellular phospholipid membranes known as perimicrovillar membranes (PMVM. Here, we investigated the role of commercial glycerophospholipids containing serine, choline and ethanolamine as headgroups and R. prolixus midgut lipids (RML in heme crystallization. All commercial unsaturated forms of phospholipids, as well as RML, mediated fast and efficient β-hematin formation by means of two kinetically distinct mechanisms: an early and fast component, followed by a late and slow one. The fastest reactions observed were induced by unsaturated forms of phosphatidylethanolamine (uPE and phosphatidylcholine (uPC, with half-lives of 0.04 and 0.7 minutes, respectively. β-hematin crystal morphologies were strikingly distinct among groups, with uPE producing homogeneous regular brick-shaped crystals. Interestingly, uPC-mediated reactions resulted in two morphologically distinct crystal populations: one less representative group of regular crystals, resembling those induced by uPE, and the other largely represented by crystals with numerous sharp edges and tapered ends. Heme crystallization reactions induced by RML were efficient, with a heme to β-hematin conversion rate higher than 70%, but clearly slower (t1/2 of 9.9-17.7 minutes than those induced by uPC and uPE. Interestingly, crystals produced by RML were homogeneous in shape and quite similar to those mediated by uPE. Thus, β-hematin formation can be rapidly and efficiently induced by unsaturated glycerophospholipids, particularly uPE and uPC, and may play a role on biological heme crystallization in R. prolixus midgut.

Heterogeneity and subjectivity in binary-state opinion formation systems

International Nuclear Information System (INIS)

Guo, Long; Luo, Zhongjie; Zhu, Yueying

2013-01-01

In society, there is heterogeneous interaction and randomness in human decision making. In order to unfold the roles and the competition of the two factors mentioned above in opinion formation, we propose a toy model, which follows a majority rule with a Fermi function, on scale-free networks with degree exponent γ. The heterogeneous interaction is related to the connectivity of a person with the interactive parameter β, and the randomness of human decision making is quantified by the interaction noise T. We find that a system with heterogeneity of network topology and interaction shows robustness perturbed by the interaction noise T according to the theoretical analysis and numerical simulation. Then, when T → 0, the homogeneous interaction (β ≃ 0) has a powerful implication for the emergence of a consensus state. Furthermore, the emergence of the two extreme values shows the competition of the heterogeneity of interaction and the subjectivity of human decision making in opinion formation. Our present work provides some perspective on and tools for understanding the diversity of opinion in our society. (paper)

Groundwater recharge dynamics in unsaturated fractured chalk: a case study

Science.gov (United States)

Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicolaetta M.

2016-04-01

The heterogeneity of the unsaturated zone controls its hydraulic response to rainfall and the extent to which pollutants are delayed or attenuated before reaching groundwater. It plays therefore a very important role in the recharge of aquifers and the transfer of pollutants because of the presence of temporary storage zones and preferential flows. A better knowledge of the physical processes in the unsaturated zone would allow an improved assessment of the natural recharge in a heterogeneous aquifer and of its vulnerability to surface-applied pollution. The case study regards the role of the thick unsaturated zone of the Cretaceous chalk aquifer in Picardy (North of France) that controls the hydraulic response to rainfall. In the North Paris Basin, much of the recharge must pass through a regional chalk bed that is composed of a porous matrix with embedded fractures. Different types of conceptual models have been formulated to explain infiltration and recharge processes in the unsaturated fractured rock. The present study analyses the episodic recharge in fractured Chalk aquifer using the kinematic diffusion theory to predict water table fluctuation in response to rainfall. From an analysis of the data, there is the evidence of 1) a seasonal behavior characterized by a constant increase in the water level during the winter/spring period and a recession period, 2) a series of episodic behaviors during the summer/autumn. Kinematic diffusion models are useful for predict preferential fluxes and dynamic conditions. The presented approach conceptualizes the unsaturated flow as a combination of 1) diffusive flow refers to the idealized portion of the pore space of the medium within the flow rate is driven essentially by local gradient of potential; 2) preferential flow by which water moves across macroscopic distances through conduits of macropore length.

Unsaturated zone flow modeling for GWTT-95

International Nuclear Information System (INIS)

Ho, C.K.; Altman, S.J.; McKenna, S.A.; Arnold, B.W.

1995-01-01

In accordance with the Nuclear Regulatory Commission regulation regarding groundwater travel times at geologic repositories, various models of unsaturated flow in fractured tuff have been developed and implemented to assess groundwater travel times at the potential repository at Yucca Mountain, Nevada. Kaplan used one-dimensional models to describe the uncertainty and sensitivity of travel times to various processes at Yucca Mountain. Robey and Arnold et al. used a two-dimensional equivalent continuum model (ECM) with inter- and intra-unit heterogeneity in an attempt to assess fast-flow paths through the unsaturated, fractured tuff at Yucca Mountain (GWTT-94). However, significant flow through the fractures in previous models was not simulated due to the characteristics of the ECM, which requires the matrix to be nearly saturated before flow through the fractures is initiated. In the current study (GWTT-95), four two-dimensional cross-sections at Yucca Mountain are simulated using both the ECM and dual-permeability (DK) models. The properties of both the fracture and matrix domains are geostatistically simulated, yielding completely heterogeneous continua. Then, simulations of flow through the four cross-sections are performed using spatially nonuniform infiltration boundary conditions. Steady-state groundwater travel times from the potential repository to the water table are calculated

Formation of Nitriles in the Interstellar Medium via Reactions of Cyano Radicals, CN(X2Σ+), with Unsaturated Hydrocarbons

Science.gov (United States)

Balucani, N.; Asvany, O.; Huang, L. C. L.; Lee, Y. T.; Kaiser, R. I.; Osamura, Y.; Bettinger, H. F.

2000-12-01

Crossed molecular beam experiments of cyano radicals, CN(X2Σ+, ν=0), in their electronic and vibrational ground state reacting with unsaturated hydrocarbons acetylene, C2H2(X1Σ+g), ethylene, C2H4(X1Ag), methylacetylene, CH3CCH(X1A1), allene, H2CCCH2(X1A1), dimethylacetylene, CH3CCCH3(X1A1'), and benzene, C6H6 (X1A1g), were performed at relative collision energies between 13.3 and 36.4 kJ mol-1 to unravel the formation of unsaturated nitriles in the outflows of late-type AGB carbon stars and molecular clouds. In all reactions, the CN radical was found to attack the π electron density of the hydrocarbon molecule with the radical center located at the carbon atom; the formation of an initial addition complex is a prevalent pathway on all the involved potential energy surfaces. A subsequent carbon-hydrogen bond rupture yields the nitriles cyanoacetylene, HCCCN (X1Σ+), vinylcyanide, C2H3CN (X1A'), 1-methylcyanoacetylene, CH3CCCN (X1A1), cyanoallene, H2CCCH(CN) (X1A'), 3-methylcyanoacetylene, HCCCH2CN(X1A'), 1,1-cyanomethylallene, H2CCC(CN)(CH3) (X1A'), and cyanobenzene, C6H5CN (X1A1). In case of acetylene and ethylene, a second reaction channel involves a [1, 2]-H atom shift in the initial HCCHCN and H2CCH2CN collision complexes prior to a hydrogen atom release to form cyanoacetylene, HCCCN (X1Σ+), and vinylcyanide, C2H3CN (X1A'). Since all these radical-neutral reactions show no entrance barriers, have exit barriers well below the energy of the reactant molecules, and are exothermic, the explicit identification of this CN versus H atom exchange pathway under single collision conditions makes this reaction class a compelling candidate to synthesize unsaturated nitriles in interstellar environments holding temperatures as low as 10 K. This general concept makes it even feasible to predict the formation of nitriles once the corresponding unsaturated hydrocarbons are identified in the interstellar medium. Here HCCCN, C2H3CN, and CH3CCCN have been already observed

Heterogeneous analysis of non-uniform neutron field formation

International Nuclear Information System (INIS)

Zagrebaev, A.M.; Fedosov, A.M.

1979-01-01

Investigated are the specific features of spatial-energy neutron distribution formation in the transient zone between regions, operating at different levels of energy release with accounting for the real structure of fuel element lattice and control elements in the channel reactors of high power. Presented are the calculation results, obtained by heterogeneous method in the two-group monopole approximation by means of the HETLAT code. The analysis, based on the homogeneous model shows, that the efficiency of the transient zone in forming neutron flux qradient can be increased by introducing an additional interlayer of moderator between the layers with extreme multiplying properties. It is stressed, that the most favourable from the point of view of energy release uniformity in zones and width of the transient zone is the variant in which neutron flux gradient is carried out by moving the control elements on the boundaries of regions while the internal rows of control elements create the conditions for flattening the energy release in the zones. The result obtained corresponds to the recommendation on optimal control, coming from the Pontryagin maximum principle. The analysis of neutron field formation using heterogeneous models mainly proves the conclusions following from homogeneous calculations using the maximum principle. At the same time quantitative results for the zones of small dimensions (less than 10 migration lengths) with a vividly expressed heterogeneous structure essentially differ from the forecast, obtained on the basis of the simplified homogeneous one-group model. The heterogeneous analysis shows possibilities for further optimization of the transient zone structure with account of the control element location

Approaches to large scale unsaturated flow in heterogeneous, stratified, and fractured geologic media

International Nuclear Information System (INIS)

Ababou, R.

1991-08-01

This report develops a broad review and assessment of quantitative modeling approaches and data requirements for large-scale subsurface flow in radioactive waste geologic repository. The data review includes discussions of controlled field experiments, existing contamination sites, and site-specific hydrogeologic conditions at Yucca Mountain. Local-scale constitutive models for the unsaturated hydrodynamic properties of geologic media are analyzed, with particular emphasis on the effect of structural characteristics of the medium. The report further reviews and analyzes large-scale hydrogeologic spatial variability from aquifer data, unsaturated soil data, and fracture network data gathered from the literature. Finally, various modeling strategies toward large-scale flow simulations are assessed, including direct high-resolution simulation, and coarse-scale simulation based on auxiliary hydrodynamic models such as single equivalent continuum and dual-porosity continuum. The roles of anisotropy, fracturing, and broad-band spatial variability are emphasized. 252 refs

Busted Butte Unsaturated Zone Transport Test: Fiscal Year 1998 Status Report Yucca Mountain Site Characterization Program Deliverable SPU85M4

International Nuclear Information System (INIS)

Bussod, G.Y.; Turin, H.J.; Lowry, W.E.

1999-01-01

This report describes the status of the Busted Butte Unsaturated Zone Transport Test (UZTT) and documents the progress of construction activities and site and laboratory characterization activities undertaken in fiscal year 1998. Also presented are predictive flow-and-transport simulations for Test Phases 1 and 2 of testing and the preliminary results and status of these test phases. Future anticipated results obtained from unsaturated-zone (UZ) transport testing in the Calico Hills Formation at Busted Butte are also discussed in view of their importance to performance assessment (PA) needs to build confidence in and reduce the uncertainty of site-scale flow-and-transport models and their abstractions for performance for license application. The principal objectives of the test are to address uncertainties associated with flow and transport in the UZ site-process models for Yucca Mountain, as identified by the PA working group in February 1997. These include but are not restricted to: (1) The effect of heterogeneities on flow and transport in unsaturated and partially saturated conditions in the Calico Hills Formation. In particular, the test aims to address issues relevant to fracture-matrix interactions and permeability contrast boundaries; (2) The migration behavior of colloids in fractured and unfractured Calico Hills rocks; (3) The validation through field testing of laboratory sorption experiments in unsaturated Calico Hills rocks; (4) The evaluation of the 3-D site-scale flow-and-transport process model (i.e., equivalent-continuum/dual-permeability/discrete-fracture-fault representations of flow and transport) used in the PA abstractions for license application; and (5) The effect of scaling from lab scale to field scale and site scale

Modelling flow through unsaturated zones: Sensitivity to unsaturated ...

Indian Academy of Sciences (India)

M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

soil properties are studied by varying the unsaturated parameters α and n over a wide range. ... Keywords. Unsaturated zone; capillary fringe; finite element method. ... and radioactive wastes. Several .... The length (L) of the soil sample is 1 m.

Formation Learning Control of Multiple Autonomous Underwater Vehicles With Heterogeneous Nonlinear Uncertain Dynamics.

Science.gov (United States)

Yuan, Chengzhi; Licht, Stephen; He, Haibo

2017-09-26

In this paper, a new concept of formation learning control is introduced to the field of formation control of multiple autonomous underwater vehicles (AUVs), which specifies a joint objective of distributed formation tracking control and learning/identification of nonlinear uncertain AUV dynamics. A novel two-layer distributed formation learning control scheme is proposed, which consists of an upper-layer distributed adaptive observer and a lower-layer decentralized deterministic learning controller. This new formation learning control scheme advances existing techniques in three important ways: 1) the multi-AUV system under consideration has heterogeneous nonlinear uncertain dynamics; 2) the formation learning control protocol can be designed and implemented by each local AUV agent in a fully distributed fashion without using any global information; and 3) in addition to the formation control performance, the distributed control protocol is also capable of accurately identifying the AUVs' heterogeneous nonlinear uncertain dynamics and utilizing experiences to improve formation control performance. Extensive simulations have been conducted to demonstrate the effectiveness of the proposed results.

A mountain-scale model for characterizing unsaturated flow and transport in fractured tuffs of Yucca Mountain

International Nuclear Information System (INIS)

Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Bodvarsson, G.S.

2003-01-01

This paper presents a large-scale modeling study characterizing fluid flow and tracer transport in the unsaturated zone of Yucca Mountain, Nevada, the proposed underground repository site for storing high-level radioactive waste. The modeling study is conducted using a three-dimensional numerical model, which incorporates a wide variety of field data and takes into account the coupled processes of flow and transport in Yucca Mountain's highly heterogeneous, unsaturated, fractured porous rock. The modeling approach is based on a dual-continuum formulation. Using different conceptual models of unsaturated flow, various scenarios of current and future climate conditions and their effects on the unsaturated zone are evaluated to aid in the assessment of the repository's system performance. These models are calibrated against field-measured data. Model-predicted flow and transport processes under current and future climates are discussed

Heterogeneous reaction of SO2 with soot: The roles of relative humidity and surface composition of soot in surface sulfate formation

Science.gov (United States)

Zhao, Yan; Liu, Yongchun; Ma, Jinzhu; Ma, Qingxin; He, Hong

2017-03-01

The conversion of SO2 to sulfates on the surface of soot is still poorly understood. Soot samples with different fractions of unsaturated hydrocarbons and oxygen-containing groups were prepared by combusting n-hexane under well-controlled conditions. The heterogeneous reaction of SO2 with soot was investigated using in situ attenuated total internal reflection infrared (ATR-IR) spectroscopy, ion chromatography (IC) and a flow tube reactor at the ambient pressure and relative humidity (RH). Water promoted SO2 adsorption and sulfate formation at the RH range from 6% to 70%, while exceeded water condensed on soot was unfavorable for sulfate formation due to inhibition of SO2 adsorption when RH was higher than 80%. The surface composition of soot, which was governed by combustion conditions, also played an important role in the heterogeneous reaction of SO2 with soot. This effect was found to greatly depend on RH. At low RH of 6%, soot with the highest fuel/oxygen ratio of 0.162 exhibited a maximum uptake capacity for SO2 because it contained a large amount of aromatic Csbnd H groups, which acted as active sites for SO2 adsorption. At RH of 54%, soot produced with a fuel/oxygen ratio of 0.134 showed the highest reactivity toward SO2 because it contained appropriate amounts of aromatic Csbnd H groups and oxygen-containing groups, subsequently leading to the optimal surface concentrations of both SO2 and water. These results suggest that variation in the surface composition of soot from different sources and/or resulting from chemical aging in the atmosphere likely affects the conversion of SO2 to sulfates.

Transmembrane helices can induce domain formation in crowded model membranes

NARCIS (Netherlands)

Domanski, Jan; Marrink, Siewert J.; Schäfer, Lars V.

We studied compositionally heterogeneous multi-component model membranes comprised of saturated lipids, unsaturated lipids, cholesterol, and a-helical TM protein models using coarse-grained molecular dynamics simulations. Reducing the mismatch between the length of the saturated and unsaturated

Preferential flow occurs in unsaturated conditions

Science.gov (United States)

Nimmo, John R.

2012-01-01

Because it commonly generates high-speed, high-volume flow with minimal exposure to solid earth materials, preferential flow in the unsaturated zone is a dominant influence in many problems of infiltration, recharge, contaminant transport, and ecohydrology. By definition, preferential flow occurs in a portion of a medium – that is, a preferred part, whether a pathway, pore, or macroscopic subvolume. There are many possible classification schemes, but usual consideration of preferential flow includes macropore or fracture flow, funneled flow determined by macroscale heterogeneities, and fingered flow determined by hydraulic instability rather than intrinsic heterogeneity. That preferential flow is spatially concentrated associates it with other characteristics that are typical, although not defining: it tends to be unusually fast, to transport high fluxes, and to occur with hydraulic disequilibrium within the medium. It also has a tendency to occur in association with large conduits and high water content, although these are less universal than is commonly assumed. Predictive unsaturated-zone flow models in common use employ several different criteria for when and where preferential flow occurs, almost always requiring a nearly saturated medium. A threshold to be exceeded may be specified in terms of the following (i) water content; (ii) matric potential, typically a value high enough to cause capillary filling in a macropore of minimum size; (iii) infiltration capacity or other indication of incipient surface ponding; or (iv) other conditions related to total filling of certain pores. Yet preferential flow does occur without meeting these criteria. My purpose in this commentary is to point out important exceptions and implications of ignoring them. Some of these pertain mainly to macropore flow, others to fingered or funneled flow, and others to combined or undifferentiated flow modes.

Modelling of the partial oxidation of {alpha}, {beta}-unsaturated aldehydes on Mo-V-oxides based catalysts

Energy Technology Data Exchange (ETDEWEB)

Boehnke, H.; Petzoldt, J.C.; Stein, B.; Weimer, C.; Gaube, J.W. [Technische Univ. Darmstadt (Germany). Inst. fuer Chemische Technologie

1998-12-31

A kinetic model based on the Mars-van Krevelen mechanism that allows to describe the microkinetics of the heterogeneously catalysed partial oxidation of {alpha}, {beta}-unsaturated aldehydes is presented. This conversion is represented by a network, composed of the oxidation of the {alpha}, {beta}-unsaturated aldehyde towards the {alpha}, {beta}-unsaturated carboxylic acid and the consecutive oxidation of the acid as well as the parallel reaction of the aldehyde to products of deeper oxidation. The reaction steps of aldehyde respectively acid oxidation and catalyst reoxidation have been investigated separately in transient experiments. The combination of steady state and transient experiments has led to an improved understanding of the interaction of the catalyst with the aldehyde and the carboxylic acids as well as to a support of the kinetic model assumptions. (orig.)

The role of Soil Water Retention Curve in slope stability analysis in unsaturated and heterogeneous soils.

Science.gov (United States)

Antinoro, Chiara; Arnone, Elisa; Noto, Leonardo V.

2015-04-01

The mechanisms of rainwater infiltration causing slope instability had been analyzed and reviewed in many scientific works. Rainwater infiltration into unsaturated soil increases the degree of saturation, hence affecting the shear strength properties and thus the probability of slope failure. It has been widely proved that the shear strength properties change with the soil water suction in unsaturated soils; therefore, the accuracy to predict the relationship between soil water content and soil water suction, parameterized by the soil-water characteristic curve, has significant effects on the slope stability analysis. The aim of this study is to investigate how the characterization of SWRC of differently structured unsaturated soils affects the slope stability on a simple infinite slope. In particular, the unimodal and bimodal distributions of the soil pore size were compared. Samples of 40 soils, highly different in terms of structure and texture, were collected and used to calibrate two bimodal SWRCs, i.e. Ross and Smettem (1993) and Dexter et al., (2008). The traditional unimodal van Genuchten (1980) model was also applied for comparison. Slope stability analysis was conducted in terms of Factor of Safety (FS) by applying the infinite slope model for unsaturated soils. In the used formulation, the contribution of the suction effect is tuned by a parameter 'chi' in a rate proportional to the saturation conditions. Different parameterizations of this term were also compared and analyzed. Results indicated that all three SWRC models showed good overall performance in fitting the sperimental SWRCs. Both the RS and DE models described adequately the water retention data for soils with a bimodal behavior confirmed from the analysis of pore size distribution, but the best performance was obtained by DE model confirmed. In terms of FS, the tree models showed very similar results as soil moisture approached to the saturated condition; however, within the residual zone

Parallel computing simulation of fluid flow in the unsaturated zone of Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Zhang, Keni; Wu, Yu-Shu; Bodvarsson, G.S.

2001-01-01

This paper presents the application of parallel computing techniques to large-scale modeling of fluid flow in the unsaturated zone (UZ) at Yucca Mountain, Nevada. In this study, parallel computing techniques, as implemented into the TOUGH2 code, are applied in large-scale numerical simulations on a distributed-memory parallel computer. The modeling study has been conducted using an over-one-million-cell three-dimensional numerical model, which incorporates a wide variety of field data for the highly heterogeneous fractured formation at Yucca Mountain. The objective of this study is to analyze the impact of various surface infiltration scenarios (under current and possible future climates) on flow through the UZ system, using various hydrogeological conceptual models with refined grids. The results indicate that the one-million-cell models produce better resolution results and reveal some flow patterns that cannot be obtained using coarse-grid modeling models

Beaded Fiber Mats of PVA Containing Unsaturated Heteropoly Salt

Institute of Scientific and Technical Information of China (English)

Guo Cheng YANG; Yan PAN; Jian GONG; Chang Lu SHAO; Shang Bin WEN; Chen SHAO; Lun Yu QU

2004-01-01

Poly(vinyl alcohol) (PVA) fiber mats containing unsaturated heteropoly salt was prepared for the first time. IR, X-ray diffraction and SEM photographs characterized the beaded fiber mats.The viscoelasticity and the conductivity of the solution were the key factors that influence the formation of the beaded fiber mats.

Amide Bond Formation Assisted by Vicinal Alkylthio Migration in Enaminones: Metal- and CO-Free Synthesis of α,β-Unsaturated Amides.

Science.gov (United States)

Liu, Zhuqing; Huang, Fei; Wu, Ping; Wang, Quannan; Yu, Zhengkun

2018-05-18

Amide bond formation is one of the most important transformations in organic synthesis, drug development, and materials science. Efficient construction of amides has been among the most challenging tasks for organic chemists. Herein, we report a concise methodology for amide bond (-CONH-) formation assisted by vicinal group migration in alkylthio-functionalized enaminones (α-oxo ketene N, S-acetals) under mild conditions. Simple treatment of such enaminones with PhI(OAc) 2 at ambient temperature in air afforded diverse multiply functionalized α,β-unsaturated amides including β-cyclopropylated acrylamides, in which a wide array of functional groups such as aryl, (hetero)aryl, alkenyl, and alkyl can be conveniently introduced to a ketene moiety. The reaction mechanism was investigated by exploring the origins of the amide oxygen and carbon atoms as well as isolation and structural characterization of the reaction intermediates. The amide bond formation reactions could also be efficiently performed under solventless mechanical milling conditions.

Homogeneously catalysed hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols

NARCIS (Netherlands)

Stouthamer, B.; Vlugter, J.C.

1965-01-01

The use of copper and cadmium oxides or soaps as catalysts for the hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols has been investigated. It is shown that copper soaps homogeneously activate hydrogen. When copper and cadmium oxides are used as catalysts, they react with the

Mechanism of spiral formation in heterogeneous discretized excitable media.

Science.gov (United States)

Kinoshita, Shu-ichi; Iwamoto, Mayuko; Tateishi, Keita; Suematsu, Nobuhiko J; Ueyama, Daishin

2013-06-01

Spiral waves on excitable media strongly influence the functions of living systems in both a positive and negative way. The spiral formation mechanism has thus been one of the major themes in the field of reaction-diffusion systems. Although the widely believed origin of spiral waves is the interaction of traveling waves, the heterogeneity of an excitable medium has recently been suggested as a probable cause. We suggest one possible origin of spiral waves using a Belousov-Zhabotinsky reaction and a discretized FitzHugh-Nagumo model. The heterogeneity of the reaction field is shown to stochastically generate unidirectional sites, which can induce spiral waves. Furthermore, we found that the spiral wave vanished with only a small reduction in the excitability of the reaction field. These results reveal a gentle approach for controlling the appearance of a spiral wave on an excitable medium.

Long Chain Saturated and Unsaturated Carboxylic Acids: Filling a Large Gap of Knowledge in Their Enthalpies of Formation.

Science.gov (United States)

Rogers, Donald W; Zavitsas, Andreas A

2017-01-06

Despite their abundance in nature and their importance in biology, medicine, nutrition, and in industry, gas phase enthalpies of formation of many long chain saturated and unsaturated fatty acids and of dicarboxylic acids are either unavailable or have been estimated with large uncertainties. Available experimental values for stearic acid show a spread of 68 kJ mol -1 . This work fills the knowledge gap by obtaining reliable values by quantum theoretical calculations using G4 model chemistry. Compounds with up to 20 carbon atoms are treated. The theoretical results are in excellent agreement with well established experimental values when such values exist, and they provide a large number of previously unavailable values.

An Erbium-Based Bifuctional Heterogeneous Catalyst: A Cooperative Route Towards C-C Bond Formation

Directory of Open Access Journals (Sweden)

Manuela Oliverio

2014-07-01

Full Text Available Heterogeneous bifuctional catalysts are multifunctional synthetic catalysts enabling efficient organic transformations by exploiting two opposite functionalities without mutual destruction. In this paper we report the first Er(III-based metallorganic heterogeneous catalyst, synthesized by post-calcination MW-assisted grafting and modification of the natural aminoacid L-cysteine. The natural acid–base distance between sites was maintained to assure the cooperation. The applicability of this new bifunctional heterogeneous catalyst to C-C bond formation and the supposed mechanisms of action are discussed as well.

Unsaturated fatty acids protect trophoblast cells from saturated fatty acid-induced autophagy defects.

Science.gov (United States)

Hong, Ye-Ji; Ahn, Hyo-Ju; Shin, Jongdae; Lee, Joon H; Kim, Jin-Hoi; Park, Hwan-Woo; Lee, Sung Ki

2018-02-01

Dysregulated serum fatty acids are associated with a lipotoxic placental environment, which contributes to increased pregnancy complications via altered trophoblast invasion. However, the role of saturated and unsaturated fatty acids in trophoblastic autophagy has yet to be explored. Here, we demonstrated that prolonged exposure of saturated fatty acids interferes with the invasiveness of human extravillous trophoblasts. Saturated fatty acids (but not unsaturated fatty acids) inhibited the fusion of autophagosomes and lysosomes, resulting in the formation of intracellular protein aggregates. Furthermore, when the trophoblast cells were exposed to saturated fatty acids, unsaturated fatty acids counteracted the effects of saturated fatty acids by increasing degradation of autophagic vacuoles. Saturated fatty acids reduced the levels of the matrix metalloproteinases (MMP)-2 and MMP-9, while unsaturated fatty acids maintained their levels. In conclusion, saturated fatty acids induced decreased trophoblast invasion, of which autophagy dysfunction plays a major role. Copyright © 2017 Elsevier B.V. All rights reserved.

Kinetics of contrail particles formation and heterogeneous reactions on such particles

Energy Technology Data Exchange (ETDEWEB)

Kogan, M.N.; Butkovsky, A.V.; Erofeev, A.I.; Freedlender, O.G.; Makashev, N.K. [Central Aerohydrodynamic Inst., Zhukovsky (Russian Federation)

1997-12-31

The research of impact of aircraft emissions upon the atmosphere is very complex and difficult problem. More than two decades of intensive investigations of the problem of ozone decay do not permit to make definite conclusions. Many important problems still remain unsolved in the aircraft/atmosphere interaction: engine, nozzle, jet, jet/vortex system interaction, vortex breakdown, contrail formation, meso-scale and global processes, their effects on climate. The particles formation and heterogeneous reactions play an important role in some of these processes. These problems are discussed. (author) 11 refs.

Kinetics of contrail particles formation and heterogeneous reactions on such particles

Energy Technology Data Exchange (ETDEWEB)

Kogan, M N; Butkovsky, A V; Erofeev, A I; Freedlender, O G; Makashev, N K [Central Aerohydrodynamic Inst., Zhukovsky (Russian Federation)

1998-12-31

The research of impact of aircraft emissions upon the atmosphere is very complex and difficult problem. More than two decades of intensive investigations of the problem of ozone decay do not permit to make definite conclusions. Many important problems still remain unsolved in the aircraft/atmosphere interaction: engine, nozzle, jet, jet/vortex system interaction, vortex breakdown, contrail formation, meso-scale and global processes, their effects on climate. The particles formation and heterogeneous reactions play an important role in some of these processes. These problems are discussed. (author) 11 refs.

Geostatistical and Stochastic Study of Flow and Tracer Transport in the Unsaturated Zone at Yucca Mountain

International Nuclear Information System (INIS)

Ye, Ming; Pan, Feng; Hu, Xiaolong; Zhu, Jianting

2007-01-01

Yucca Mountain has been proposed by the U.S. Department of Energy as the nation's long-term, permanent geologic repository for spent nuclear fuel or high-level radioactive waste. The potential repository would be located in Yucca Mountain's unsaturated zone (UZ), which acts as a critical natural barrier delaying arrival of radionuclides to the water table. Since radionuclide transport in groundwater can pose serious threats to human health and the environment, it is important to understand how much and how fast water and radionuclides travel through the UZ to groundwater. The UZ system consists of multiple hydrogeologic units whose hydraulic and geochemical properties exhibit systematic and random spatial variation, or heterogeneity, at multiple scales. Predictions of radionuclide transport under such complicated conditions are uncertain, and the uncertainty complicates decision making and risk analysis. This project aims at using geostatistical and stochastic methods to assess uncertainty of unsaturated flow and radionuclide transport in the UZ at Yucca Mountain. Focus of this study is parameter uncertainty of hydraulic and transport properties of the UZ. The parametric uncertainty arises since limited parameter measurements are unable to deterministically describe spatial variability of the parameters. In this project, matrix porosity, permeability and sorption coefficient of the reactive tracer (neptunium) of the UZ are treated as random variables. Corresponding propagation of parametric uncertainty is quantitatively measured using mean, variance, 5th and 95th percentiles of simulated state variables (e.g., saturation, capillary pressure, percolation flux, and travel time). These statistics are evaluated using a Monte Carlo method, in which a three-dimensional flow and transport model implemented using the TOUGH2 code is executed with multiple parameter realizations of the random model parameters. The project specifically studies uncertainty of unsaturated flow

Transport of Sr 2+ and SrEDTA 2- in partially-saturated and heterogeneous sediments

Science.gov (United States)

Pace, M. N.; Mayes, M. A.; Jardine, P. M.; McKay, L. D.; Yin, X. L.; Mehlhorn, T. L.; Liu, Q.; Gürleyük, H.

2007-05-01

Strontium-90 has migrated deep into the unsaturated subsurface beneath leaking storage tanks in the Waste Management Areas (WMA) at the U.S. Department of Energy's (DOE) Hanford Reservation. Faster than expected transport of contaminants in the vadose zone is typically attributed to either physical hydrologic processes such as development of preferential flow pathways, or to geochemical processes such as the formation of stable, anionic complexes with organic chelates, e.g., ethylenediaminetetraacetic acid (EDTA). The goal of this paper is to determine whether hydrological processes in the Hanford sediments can influence the geochemistry of the system and hence control transport of Sr 2+ and SrEDTA 2-. The study used batch isotherms, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core. Isotherms and repacked column experiments suggested that the SrEDTA 2- complex was unstable in the presence of Hanford sediments, resulting in dissociation and transport of Sr 2+ as a divalent cation. A decrease in sorption with increasing solid:solution ratio for Sr 2+ and SrEDTA 2- suggested mineral dissolution resulted in competition for sorption sites and the formation of stable aqueous complexes. This was confirmed by detection of MgEDTA 2-, MnEDTA 2-, PbEDTA 2-, and unidentified Sr and Ca complexes. Displacement of Sr 2+ through a partially-saturated undisturbed core resulted in less retardation and more irreversible sorption than was observed in the saturated repacked columns, and model results suggested a significant reservoir (49%) of immobile water was present during transport through the heterogeneous layered sediments. The undisturbed core was subsequently disassembled along distinct bedding planes and subjected to sequential extractions. Strontium was unequally distributed between carbonates (49%), ion exchange sites (37%), and the oxide (14%) fraction. An inverse relationship between mass wetness and Sr suggested that

Focused Flow During Infiltration Into Ethanol-Contaminated Unsaturated Porous Media

Science.gov (United States)

Jazwiec, A.; Smith, J. E.

2017-12-01

The increasing commercial and industrial use of ethanol, e.g. in biofuels, has generated increased incidents of vadose zone contamination by way of ethanol spills and releases. This has increased the interest in better understanding behaviors of ethanol in unsaturated porous media and it's multiphase interactions in the vadose zone. This study uses highly controlled laboratory experiments in a 2-D (0.6mx0.6mx0.01m) flow cell to investigate water infiltration behaviors into ethanol-contaminated porous media. Ethanol and water were applied by either constant head or constant flux methods onto the surface of sands homogenously packed into the flow cell. The constant flux experiments at both low and high application rates were conducted using a rainulator with a row of hypodermic needles connected to a peristaltic pump. The constant head experiments were conducted using an 8cm diameter tension disk infiltrometer set to both low and high tensions. The presence of ethanol contamination generated solute-dependent capillarity induced focused flow (SCIFF) of water infiltration, which was primarily due to decreases in interfacial tensions at the air-liquid interfaces in the unsaturated sands as a function of ethanol concentration. SCIFF was clearly expressed as an unsaturated water flow phenomenon comprised of narrowly focused vertical flow fingers of water within the initially ethanol contaminated porous media. Using analyses of photos and video, comparisons were made between constant flux and constant head application methods. Further comparisons were made between low and high infiltration rates and the two sand textures used. A high degree of sensitivity to minor heterogeneity in relatively homogeneous sands was also observed. The results of this research have implications for rainfall infiltration into ethanol contaminated vadose zones expressing SCIFF, including implications for associated mass fluxes and the nature of flushing of ethanol from the unsaturated zone to

Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region

Science.gov (United States)

Walvoord, Michelle Ann; Andraski, Brian J.; Krabbenhoft, D.P.; Striegl, Robert G.

2008-01-01

Mercury contained in buried landfill waste may be released via upward emission to the atmosphere or downward leaching to groundwater. Data from the US Geological Survey’s Amargosa Desert Research Site (ADRS) in arid southwestern Nevada reveal another potential pathway of Hg release: long-distance (102 m) lateral migration of elemental Hg (Hg0) through the unsaturated zone. Gas collected from multiple depths from two instrumented boreholes that sample the entire 110-m unsaturated zone thickness and are located 100 and 160 m away from the closest waste burial trench exhibit gaseous Hg concentrations of up to 33 and 11 ng m−3, respectively. The vertical distribution of gaseous Hg in the borehole closest to the disposal site shows distinct subsurface peaks in concentration at depths of 1.5 and 24 m that cannot be explained by radial diffusive transport through a heterogeneous layered unsaturated zone. The inability of current models to explain gaseous Hg distribution at the ADRS highlights the need to advance the understanding of gas-phase contaminant transport in unsaturated zones to attain a comprehensive model of landfill Hg release.

Thermal conductivity measurements in unsaturated hydrate-bearing sediments

Science.gov (United States)

Dai, Sheng; Cha, Jong-Ho; Rosenbaum, Eilis J.; Zhang, Wu; Seol, Yongkoo

2015-08-01

Current database on the thermal properties of hydrate-bearing sediments remains limited and has not been able to capture their consequential changes during gas production where vigorous phase changes occur in this unsaturated system. This study uses the transient plane source (TPS) technique to measure the thermal conductivity of methane hydrate-bearing sediments with various hydrate/water/gas saturations. We propose a simplified method to obtain thermal properties from single-sided TPS signatures. Results reveal that both volume fraction and distribution of the pore constituents govern the thermal conductivity of unsaturated specimens. Thermal conductivity hysteresis is observed due to water redistribution and fabric change caused by hydrate formation and dissociation. Measured thermal conductivity increases evidently when hydrate saturation Sh > 30-40%, shifting upward from the geometric mean model prediction to a Pythagorean mixing model. These observations envisage a significant drop in sediment thermal conductivity when residual hydrate/water saturation falls below ~40%, hindering further gas production.

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

Directory of Open Access Journals (Sweden)

Katherine M. Byrd

2015-04-01

Full Text Available The conjugate addition reaction has been a useful tool in the formation of carbon–carbon bonds. The utility of this reaction has been demonstrated in the synthesis of many natural products, materials, and pharmacological agents. In the last three decades, there has been a significant increase in the development of asymmetric variants of this reaction. Unfortunately, conjugate addition reactions using α,β-unsaturated amides and lactams remain underdeveloped due to their inherently low reactivity. This review highlights the work that has been done on both diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams.

The Unsaturated Hydromechanical Coupling Model of Rock Slope Considering Rainfall Infiltration Using DDA

Directory of Open Access Journals (Sweden)

Xianshan Liu

2017-01-01

Full Text Available Water flow and hydromechanical coupling process in fractured rocks is more different from that in general porous media because of heterogeneous spatial fractures and possible fracture-dominated flow; a saturated-unsaturated hydromechanical coupling model using a discontinuous deformation analysis (DDA similar to FEM and DEM was employed to analyze water movement in saturated-unsaturated deformed rocks, in which the Van-Genuchten model differently treated the rock and fractures permeable properties to describe the constitutive relationships. The calibrating results for the dam foundation indicated the validation and feasibility of the proposed model and are also in good agreement with the calculations based on DEM still demonstrating its superiority. And then, the rainfall infiltration in a reservoir rock slope was detailedly investigated to describe the water pressure on the fault surface and inside the rocks, displacement, and stress distribution under hydromechanical coupling conditions and uncoupling conditions. It was observed that greater rainfall intensity and longer rainfall time resulted in lower stability of the rock slope, and larger difference was very obvious between the hydromechanical coupling condition and uncoupling condition, demonstrating that rainfall intensity, rainfall time, and hydromechanical coupling effect had great influence on the saturated-unsaturated water flow behavior and mechanical response of the fractured rock slopes.

Full-field dye concentration measurement within saturated/unsaturated thin slabs of porous media

International Nuclear Information System (INIS)

Norton, D.L.; Glass, R.J.

1993-01-01

This paper presents a full-field dye concentration measurement technique that extends our experimental capabilities to the measurement of transient dye concentration fields within steady state flow fields under unsaturated or saturated conditions. Simple light absorption theory provides a basis for translating images into high resolution dye concentration fields. A series of dye pulse experiments that demonstrate the combined use of the full-field saturation and dye concentration techniques was conducted at four different degrees of saturation. Each of these experimental sequences was evaluated with respect to mass balance, the results being within 5% of the known dye mass input. An image windowing technique allowed us to see increased dispersion due to decreasing moisture content, tailing of concentration at the rear of the dye pulse and slight velocity changes of the dispersive front due to changes in moisture content. The exceptional resolution of dye concentration in space and time provided by this laboratory technique allows systematic experimentation for examining basic processes affecting solute transport within saturated/unsaturated porous media. Future challenges for this work will be to use these techniques to analyze more complex systems involving heterogeneities, scaling laws, and detailed investigations of the relationship between transverse and longitudinal dispersion in unsaturated media

Analysis of pumping-induced unsaturated regions beneath aperennial river

Energy Technology Data Exchange (ETDEWEB)

Su, G.W.; Jasperse, J.; Seymour, D.; Constantz, J.; Zhou, Q.

2007-05-15

The presence of an unsaturated region beneath a streambedduring groundwater pumping near streams reduces the pumping capacity whenit reaches the well screens, changes flow paths, and alters the types ofbiological transformations in the streambed sediments. Athree-dimensional, multi-phase flow model of two horizontal collectorwells along the Russian River near Forestville, California was developedto investigate the impact of varying the ratio of the aquifer tostreambed permeability on (1) the formation of an unsaturated regionbeneath the stream, (2) the pumping capacity, (3) stream-water fluxesthrough the streambed, and (4) stream-water travel times to the collectorwells. The aquifer to streambed permeability ratio at which theunsaturated region was initially observed ranged from 10 to 100. The sizeof the unsaturated region beneath the streambed increased as the aquiferto streambed permeability ratio increased. The simulations also indicatedthat for a particular aquifer permeability, decreasing the streambedpermeability by only a factor of 2-3 from the permeability wheredesaturation initially occurred resulted in reducing the pumpingcapacity. In some cases, the stream-water fluxes increased as thestreambed permeability decreased. However, the stream water residencetimes increased and the fraction of stream water that reached that thewells decreased as the streambed permeability decreased, indicating thata higher streambed flux does not necessarily correlate to greaterrecharge of stream water around the wells.

Monte Carlo simulation of nonlinear reactive contaminant transport in unsaturated porous media

International Nuclear Information System (INIS)

Giacobbo, F.; Patelli, E.

2007-01-01

In the current proposed solutions of radioactive waste repositories, the protective function against the radionuclide water-driven transport back to the biosphere is to be provided by an integrated system of engineered and natural geologic barriers. The occurrence of several nonlinear interactions during the radionuclide migration process may render burdensome the classical analytical-numerical approaches. Moreover, the heterogeneity of the barriers' media forces approximations to the classical analytical-numerical models, thus reducing their fidelity to reality. In an attempt to overcome these difficulties, in the present paper we adopt a Monte Carlo simulation approach, previously developed on the basis of the Kolmogorov-Dmitriev theory of branching stochastic processes. The approach is here extended for describing transport through unsaturated porous media under transient flow conditions and in presence of nonlinear interchange phenomena between the liquid and solid phases. This generalization entails the determination of the functional dependence of the parameters of the proposed transport model from the water content and from the contaminant concentration, which change in space and time during the water infiltration process. The corresponding Monte Carlo simulation approach is verified with respect to a case of nonreactive transport under transient unsaturated flow and to a case of nonlinear reactive transport under stationary saturated flow. Numerical applications regarding linear and nonlinear reactive transport under transient unsaturated flow are reported

Numerical modeling of isothermal and nonisothermal flow in unsaturated fractured rock: A review

International Nuclear Information System (INIS)

Pruess, K.; Wang, J.S.Y.

1986-01-01

The tuff formations at and near the Nevada Test Site are comprised of fractured-porous material, with hydrologic properties quite different from those encountered in most previous unsaturated flow studies dealing with soils. In the vicinity of the waste packages, flow is driven by high temperatures (exceeding 100 0 C) and large temperature gradients. The approximations developed in soil science for weakly nonisothermal flow are not applicable to this situation, and a multiphase description of flow is required, similar to approaches used in modeling of geothermal reservoirs and thermally enhance oil recovery. The conventional approach to unsaturated flow is applicable, however, to a variety of problems relating to natural (undisturbed) and far-field flow conditions. This paper reviews recent work on numerical modeling of unsaturated flow undertaken in the context of nuclear waste isolation studies. Concepts and applications of broader interest are summarized, and important issues are identified that have not been adequately explored. 84 refs, 8 figs

CAPILLARY BARRIERS IN UNSATURATED FRACTURED ROCKS OF YUCCA MOUNTAIN, NEVADA

International Nuclear Information System (INIS)

Wu, Y.S.; Zhang, W.; Pan, L.; Hinds, J.; Bodvarsson, G.

2000-01-01

This work presents modeling studies investigating the effects of capillary barriers on fluid-flow and tracer-transport processes in the unsaturated zone of Yucca Mountain, Nevada, a potential site for storing high-level radioactive waste. These studies are designed to identify factors controlling the formation of capillary barriers and to estimate their effects on the extent of possible large-scale lateral flow in unsaturated fracture rocks. The modeling approach is based on a continuum formulation of coupled multiphase fluid and tracer transport through fractured porous rock. Flow processes in fractured porous rock are described using a dual-continuum concept. In addition, approximate analytical solutions are developed and used for assessing capillary-barrier effects in fractured rocks. This study indicates that under the current hydrogeologic conceptualization of Yucca Mountain, strong capillary-barrier effects exist for significantly diverting moisture flow

Heterogeneity-enhanced gas phase formation in shallow aquifers during leakage of CO2-saturated water from geologic sequestration sites

DEFF Research Database (Denmark)

Plampin, Michael R.; Lassen, Rune Nørbæk; Sakaki, Toshihiro

2014-01-01

sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2......, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been...... quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test...

Variability of soil potential for biodegradation of petroleum hydrocarbons in a heterogeneous subsurface

DEFF Research Database (Denmark)

Kristensen, Andreas Houlberg; Poulsen, Tjalfe; Mortensen, Lars

2010-01-01

for biodegradation was highly variable, which from autoregressive state-space modeling was partly explained by changes in soil air-filled porosity and gravimetric water content. The results suggest considering biological heterogeneity when evaluating the fate of contaminants in the subsurface.......Quantifying the spatial variability of factors affecting natural attenuation of hydrocarbons in the unsaturated zone is important to (i) performing a reliable risk assessment and (ii) evaluating the possibility for bioremediation of petroleum-polluted sites. Most studies to date have focused...... on the shallow unsaturated zone. Based on a data set comprising analysis of about 100 soil samples taken in a 16-m-deep unsaturated zone polluted with volatile petroleum compounds, we statistically and geostatistically analyzed values of essential soil properties. The subsurface of the site was highly layered...

Fourier transform infrared imaging showing reduced unsaturated lipid content in the hippocampus of a mouse model of Alzheimer's disease.

Science.gov (United States)

Leskovjan, Andreana C; Kretlow, Ariane; Miller, Lisa M

2010-04-01

Polyunsaturated fatty acids are essential to brain functions such as membrane fluidity, signal transduction, and cell survival. It is also thought that low levels of unsaturated lipid in the brain may contribute to Alzheimer's disease (AD) risk or severity. However, it is not known how accumulation of unsaturated lipids is affected in different regions of the hippocampus, which is a central target of AD plaque pathology, during aging. In this study, we used Fourier transform infrared imaging (FTIRI) to visualize the unsaturated lipid content in specific regions of the hippocampus in the PSAPP mouse model of AD as a function of plaque formation. Specifically, the unsaturated lipid content was imaged using the olefinic =CH stretching mode at 3012 cm(-1). The axonal, dendritic, and somatic layers of the hippocampus were examined in the mice at 13, 24, 40, and 56 weeks old. Results showed that lipid unsaturation in the axonal layer was significantly increased with normal aging in control (CNT) mice (p avoiding progression of the disease.

A genetic meta-algorithm-assisted inversion approach: hydrogeological study for the determination of volumetric rock properties and matrix and fluid parameters in unsaturated formations

Science.gov (United States)

Szabó, Norbert Péter

2018-03-01

An evolutionary inversion approach is suggested for the interpretation of nuclear and resistivity logs measured by direct-push tools in shallow unsaturated sediments. The efficiency of formation evaluation is improved by estimating simultaneously (1) the petrophysical properties that vary rapidly along a drill hole with depth and (2) the zone parameters that can be treated as constant, in one inversion procedure. In the workflow, the fractional volumes of water, air, matrix and clay are estimated in adjacent depths by linearized inversion, whereas the clay and matrix properties are updated using a float-encoded genetic meta-algorithm. The proposed inversion method provides an objective estimate of the zone parameters that appear in the tool response equations applied to solve the forward problem, which can significantly increase the reliability of the petrophysical model as opposed to setting these parameters arbitrarily. The global optimization meta-algorithm not only assures the best fit between the measured and calculated data but also gives a reliable solution, practically independent of the initial model, as laboratory data are unnecessary in the inversion procedure. The feasibility test uses engineering geophysical sounding logs observed in an unsaturated loessy-sandy formation in Hungary. The multi-borehole extension of the inversion technique is developed to determine the petrophysical properties and their estimation errors along a profile of drill holes. The genetic meta-algorithmic inversion method is recommended for hydrogeophysical logging applications of various kinds to automatically extract the volumetric ratios of rock and fluid constituents as well as the most important zone parameters in a reliable inversion procedure.

Combined effects of headgroup charge and tail unsaturation of lipids on lateral organization and diffusion of lipids in model biomembranes

International Nuclear Information System (INIS)

Chen Xiao-Jie; Liang Qing

2017-01-01

Lateral organization and dynamics of lipids in plasma membranes are crucial for several cellular processes such as signal transduction across the membrane and still remain elusive. In this paper, using coarse-grained molecular dynamics simulation, we theoretically study the combined effects of headgroup charge and tail unsaturation of lipids on the lateral organization and diffusion of lipids in ternary lipid bilayers. In neutral ternary lipid bilayers composed of saturated lipids, unsaturated lipids, and cholesterols, under the conditions of given temperature and components, the main factor for the phase separation is the unsaturation of unsaturated lipids and the bilayers can be separated into liquid-ordered domains enriched in saturated lipids and cholesterols and liquid-disordered domains enriched in unsaturated lipids. Once the headgroup charge is introduced, the electrostatic repulsion between the negatively charged lipid headgroups will increase the distance between the charged lipids. We find that the lateral organization and diffusion of the lipids in the (partially) charged ternary lipid bilayers are determined by the competition between the headgroup charge and the unsaturation of the unsaturated lipids. In the bilayers containing unsaturated lipids with lower unsaturation, the headgroup charge plays a crucial role in the lateral organization and diffusion of lipids. The headgroup charge may make the lipid domains unstable and even can suppress phase separation of the lipids in some systems. However, in the bilayers containing highly unsaturated lipids, the lateral organization and diffusion of lipids are mainly dominated by the unsaturation of the unsaturated lipids. This work may provide some theoretical insights into understanding the formation of nanosized domains and lateral diffusion of lipids in plasma membranes. (paper)

Monte Carlo simulation of radioactive contaminant transport in unsaturated porous media

International Nuclear Information System (INIS)

Giacobbo, F.; Patelli, E.; Zio, E.

2005-01-01

In the current proposed solutions of radioactive waste repositories, the protective function against the radionuclide water-driven transport back to the biosphere is to be provided by an integrated system of artificial and natural geologic barriers. The complexity of the transport process in the barriers' heterogeneous media forces approximations to the classical analytical-numerical models, thus reducing their adherence to reality. In an attempt to overcome these difficulties, in the present paper we adopt a Monte Carlo simulation approach, previously developed on the basis of the Kolmogorov and Dmitriev theory of branching stochastic processes. The approach is here extended for describing transport through unsaturated porous media under unsteady flow conditions. This generalization entails the determination of the functional dependence of the parameters of the proposed transport model from the water content, which changes in space and time during the water infiltration process. The approach is verified with respect to a case of non-reactive transport under transient unsaturated field conditions by a comparison with a standard code based on the classical advection-dispersion equations. An application regarding linear reactive transport is then presented. (authors)

The unsaturated bistable stochastic resonance system.

Science.gov (United States)

Zhao, Wenli; Wang, Juan; Wang, Linze

2013-09-01

We investigated the characteristics of the output saturation of the classical continuous bistable system (saturation bistable system) and its impact on stochastic resonance (SR). We further proposed a piecewise bistable SR system (unsaturated bistable system) and developed the expression of signal-to-noise ratio (SNR) using the adiabatic approximation theory. Compared with the saturation bistable system, the SNR is significantly improved in our unsaturated bistable SR system. The numerical simulation showed that the unsaturated bistable system performed better in extracting weak signals from strong background noise than the saturation bistable system.

Patterned biofilm formation reveals a mechanism for structural heterogeneity in bacterial biofilms.

Science.gov (United States)

Gu, Huan; Hou, Shuyu; Yongyat, Chanokpon; De Tore, Suzanne; Ren, Dacheng

2013-09-03

Bacterial biofilms are ubiquitous and are the major cause of chronic infections in humans and persistent biofouling in industry. Despite the significance of bacterial biofilms, the mechanism of biofilm formation and associated drug tolerance is still not fully understood. A major challenge in biofilm research is the intrinsic heterogeneity in the biofilm structure, which leads to temporal and spatial variation in cell density and gene expression. To understand and control such structural heterogeneity, surfaces with patterned functional alkanthiols were used in this study to obtain Escherichia coli cell clusters with systematically varied cluster size and distance between clusters. The results from quantitative imaging analysis revealed an interesting phenomenon in which multicellular connections can be formed between cell clusters depending on the size of interacting clusters and the distance between them. In addition, significant differences in patterned biofilm formation were observed between wild-type E. coli RP437 and some of its isogenic mutants, indicating that certain cellular and genetic factors are involved in interactions among cell clusters. In particular, autoinducer-2-mediated quorum sensing was found to be important. Collectively, these results provide missing information that links cell-to-cell signaling and interaction among cell clusters to the structural organization of bacterial biofilms.

Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei

Directory of Open Access Journals (Sweden)

D. Barahona

2009-08-01

Full Text Available This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from observations. The parameterization reproduces the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. The formulation presented is fast and free from requirements of numerical integration.

Chemo-hydro-mechanical behaviour of unsaturated clays

International Nuclear Information System (INIS)

Mokni, N.; Olivella, S.; Alonso, E.E.; Romero, E.

2010-01-01

influence of chemical loading on this reference formation in Belgium. To map out the chemo-hydro-mechanical behaviour of the Boom Clay a series of oedometric tests under saturated and unsaturated conditions are being performed. The experiments are being conducted on reconstituted specimens prepared by mixing the powdered clay with sodium nitrate solution to slurry at about the liquid limit. (authors)

Numerical simulation of gas flow through unsaturated fractured rock at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Cooper, C.A.

1990-01-01

Numerical analysis is used to identify the physical phenomena associated with barometrically driven gas (air and water vapor) flow through unsaturated fractured rock at Yucca Mountain, Nevada. Results from simple finite difference simulations indicate that for a fractured rock scenario, the maximum velocity of air out of an uncased 10 cm borehole is 0.002 m s -1 . An equivalent porous medium (EPM) model was incorporated into a multiphase, multicomponent simulator to test more complex conceptual models. Results indicate that for a typical June day, a diurnal pressure wave propagates about 160 m into the surrounding Tiva Canyon hydrogeologic unit. Dry air that enters the formation evaporates water around the borehole which reduces capillary pressure. Multiphase countercurrent flow develops in the vicinity of the hole; the gas phase flows into the formation while the liquid phase flows toward the borehole. The effect occurs within 0.5 m of the borehole. The amount of water vapor leaving the formation during 1 day is 900 cm 3 . This is less than 0.1% of the total recharge into the formation, suggesting that the barometric effect may be insignificant in drying the unsaturated zone. However, gas phase velocities out of the borehole (3 m s -1 ), indicating that observed flow rates from wells along the east flank of Yucca Mountain were able to be simulated with a barometric model

Semi-analytical treatment of fracture/matrix flow in a dual-porosity simulator for unsaturated fractured rock masses

International Nuclear Information System (INIS)

Zimmerman, R.W.; Bodvarsson, G.S.

1992-04-01

A semi-analytical dual-porosity simulator for unsaturated flow in fractured rock masses has been developed. Fluid flow between the fracture network and the matrix blocks is described by analytical expressions that have been derived from approximate solutions to the imbibition equation. These expressions have been programmed into the unsaturated flow simulator, TOUGH, as a source/sink term. Flow processes are then simulated using only fracture elements in the computational grid. The modified code is used to simulate flow along single fractures, and infiltration into pervasively fractured formations

Evaluating sensitivity of unsaturated soil properties

International Nuclear Information System (INIS)

Abdel-Rahman, R.O.; El-Kamash, A.M.; Nagy, M.E.; Khalill, M.Y.

2005-01-01

The assessment of near surface disposal performance relay on numerical models of groundwater flow and contaminant transport. These models use the unsaturated soil properties as input parameters, which are subject to uncertainty due to measurements errors and the spatial variability in the subsurface environment. To ascertain how much the output of the model will depend on the unsaturated soil properties the parametric sensitivity analysis is used. In this paper, a parametric sensitivity analysis of the Van Genuchten moisture retention characteristic (VGMRC) model will be presented and conducted to evaluate the relative importance of the unsaturated soil properties under different pressure head values that represent various dry and wet conditions. (author)

Conceptual hydrologic model of flow in the unsaturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Montazer, P.; Wilson, W.E.

1984-01-01

The purpose of this report is to propose a conceptual hydrologic model that reasonably describes the flow of fluids through the unsaturated zone at Yucca Mountain, for use as a basis for preliminary site-performance assessment and as a guide to further investigations. Scott and others (1983) presented an initial conceptual hydrogeologic model for the unsaturated zone at Yucca Mountain, based on detailed geologic, but very limited hydrologic, information. In this report, some of their concepts are examined and either supported or modified, and new concepts are developed. The model describes the manner in which flow probably occurs at Yucca Mountain and is based on: (1) current understanding of the hydrogeologic framework; (2) application of the principles of unsaturated flow; and (3) interpretation of some preliminary data from ongoing field and laboratory investigations. Included are extensive geologic information but relatively few hydrologic data that currently exist from the unsaturated zone in the Yucca Mountain area. Many uncertainties remain to be resolved concerning hydrologic conditions and processes. As a result, most of the concepts presented are intentionally descriptive and conjectural, with little quantitative basis provided. However, for the sake of directness and simplicity of expression, the model is presented as if it were a true expression of the facts. The authors recognize, and the reader should be aware, that the proposed model probably is not the only reasonable description that could be made at this point, and it certainly is subject to revision and quantification as more data become available. Although various alternative models probably could be developed, the one described in this report seems to fit current understanding of the unsaturated flow through a section of layered, fractured-rock formations with contrasting hydrologic properties, such as occurs at Yucca Mountain. 41 refs., 14 figs., 1 tab

Heterogeneous hydrogenation of unsaturated compounds with catalyst P-2-Ni with turnover numbers up to 90,000

Energy Technology Data Exchange (ETDEWEB)

Strohmeier, W; Pfoehler, M; Steigerwald, H [Wuerzburg Univ. (Germany, F.R.). Inst. fuer Physikalische Chemie

1977-12-01

Unsaturated compounds are very rapidly hydrogenated with nickel-boride catalyst P-2-Ni without solvent under mild conditions (70-85/sup 0/C and 10 bar). Turnover numbers UZ up to 90,000 and space-time-yields of 7.440 mmol product per l and 1 mgA Nickel in one hour with a mean catalyst activity a = 124 were observed. This hydrogenation catalyst has a power, which is in the same magnitude of very active noble metal catalysts.

Design of dry barriers for containment of contaminants in unsaturated soils

International Nuclear Information System (INIS)

Morris, C.E.; Thomson, B.M.; Stormont, J.C.

1997-01-01

A dry barrier is a region of very dry conditions in unsaturated soil that prevents vertical migration of water created by circulating dry air through the formation. Dry soil creates a barrier to vertical water movement by decreasing the soil's hydraulic conductivity, a concept also used in capillary barriers. A dry barrier may be a viable method for providing containment of a contaminant plume in a setting with a thick unsaturated zone and dry climate. The principal factors which determine the feasibility of a dry barrier include: (1) an and environment, (2) thick vadose zone, and (3) the ability to circulate air through the vadose zone. This study investigated the technical and economic considerations associated with creating a dry barrier to provide containment of a hypothetical 1 ha aqueous contaminant plume. The concept appears to be competitive with other interim containment methods such as ground freezing

Validation studies for assessing unsaturated flow and transport through fractured rock

International Nuclear Information System (INIS)

Bassett, R.L.; Neuman, S.P.; Rasmussen, T.C.; Guzman, A.; Davidson, G.R.; Lohrstorfer, C.F.

1994-08-01

*The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and evaluation of procedures for estimating hydraulic, pneumatic, and solute transport coefficients for a range of thermal regimes. A field heater experiment was designed that focused on identifying the suitability of existing monitoring equipment to obtain required data. A reliable method was developed for conducting and interpreting tests for air permeability using a straddle-packer arrangement. Detailed studies of fracture flow from Queen Creek into the Magina Copper Company ore haulage tunnel have been initiated. These studies will provide data on travel time for transport of water and solute in unsaturated tuff. The collection of rainfall runoff, and infiltration data at two small watersheds at the Apache Leap Tuff Site enabled us to evaluate the quantity and rate of water infiltrating into the subsurface via either fractures or matrix. Characterization methods for hydraulic parameters relevant to Weigh-level waste transport, including fracture apertures, transmissivity, matrix porosity, and fracture wetting front propagation velocities, were developed

Validation studies for assessing unsaturated flow and transport through fractured rock

Energy Technology Data Exchange (ETDEWEB)

Bassett, R.L.; Neuman, S.P.; Rasmussen, T.C.; Guzman, A.; Davidson, G.R.; Lohrstorfer, C.F. [Arizona Univ., Tucson, AZ (United States). Dept. of Hydrology and Water Resources

1994-08-01

*The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and evaluation of procedures for estimating hydraulic, pneumatic, and solute transport coefficients for a range of thermal regimes. A field heater experiment was designed that focused on identifying the suitability of existing monitoring equipment to obtain required data. A reliable method was developed for conducting and interpreting tests for air permeability using a straddle-packer arrangement. Detailed studies of fracture flow from Queen Creek into the Magina Copper Company ore haulage tunnel have been initiated. These studies will provide data on travel time for transport of water and solute in unsaturated tuff. The collection of rainfall runoff, and infiltration data at two small watersheds at the Apache Leap Tuff Site enabled us to evaluate the quantity and rate of water infiltrating into the subsurface via either fractures or matrix. Characterization methods for hydraulic parameters relevant to Weigh-level waste transport, including fracture apertures, transmissivity, matrix porosity, and fracture wetting front propagation velocities, were developed.

Investigation into reaction of heterogenous isotopic exchange with gaseoUs tritium in solution for preparation labelled lipid compounds

International Nuclear Information System (INIS)

Shevchenko, V.P.; Myasoedov, N.F.

1983-01-01

The applicability of the method of heterogeneous catalytic isotopic exchange with gaseous tritium in the solution for the production of labelled lipide preparations is studied. Labelled saturated and unsaturated aliphatic acids, prostaglandins, phospholipides and sphingolipides are prepared

Uranium Sequestration by Aluminum Phosphate Minerals in Unsaturated Soils

International Nuclear Information System (INIS)

Jerden, James L. Jr.

2007-01-01

A mineralogical and geochemical study of soils developed from the unmined Coles Hill uranium deposit (Virginia) was undertaken to determine how phosphorous influences the speciation of uranium in an oxidizing soil/saprolite system typical of the eastern United States. This paper presents mineralogical and geochemical results that identify and quantify the processes by which uranium has been sequestered in these soils. It was found that uranium is not leached from the saturated soil zone (saprolites) overlying the deposit due to the formation of a sparingly soluble uranyl phosphate mineral of the meta-autunite group. The concentration of uranium in the saprolites is approximately 1000 mg uranium per kg of saprolite. It was also found that a significant amount of uranium was retained in the unsaturated soil zone overlying uranium-rich saprolites. The uranium concentration in the unsaturated soils is approximately 200 mg uranium per kg of soil (20 times higher than uranium concentrations in similar soils adjacent to the deposit). Mineralogical evidence indicates that uranium in this zone is sequestered by a barium-strontium-calcium aluminum phosphate mineral of the crandallite group (gorceixite). This mineral is intimately inter-grown with iron and manganese oxides that also contain uranium. The amount of uranium associated with both the aluminum phosphates (as much as 1.4 weight percent) has been measured by electron microprobe micro-analyses and the geochemical conditions under which these minerals formed has been studied using thermodynamic reaction path modeling. The geochemical data and modeling results suggest the meta-autunite group minerals present in the saprolites overlying the deposit are unstable in the unsaturated zone soils overlying the deposit due to a decrease in soil pH (down to a pH of 4.5) at depths less than 5 meters below the surface. Mineralogical observations suggest that, once exposed to the unsaturated environment, the meta-autunite group

Role of Unsaturated Lipid and Ergosterol in Ethanol Tolerance of Model Yeast Biomembranes

KAUST Repository

Vanegas, Juan M.

2012-02-07

We present a combined atomic force microscopy and fluorescence microscopy study of the behavior of a ternary supported lipid bilayer system containing a saturated lipid (DPPC), an unsaturated lipid (DOPC), and ergosterol in the presence of high ethanol (20 vol %). We find that the fluorescent probe Texas Red DHPE preferentially partitions into the ethanol-induced interdigitated phase, which allows the use of fluorescence imaging to investigate the phase behavior of the system. Atomic force microscopy and fluorescence images of samples with the same lipid mixture show good agreement in sample morphology and area fractions of the observed phases. Using area fractions obtained from fluorescence images over a broad range of compositions, we constructed a phase diagram of the DPPC/DOPC/ergosterol system at 20 vol % ethanol. The phase diagram clearly shows that increasing unsaturated lipid and/or ergosterol protects the membrane by preventing the formation of the interdigitated phase. This result supports the hypothesis that yeast cells increase ergosterol and unsaturated lipid content to prevent interdigitation and maintain an optimal membrane thickness as ethanol concentration increases during anaerobic fermentations. Changes in plasma membrane composition provide an important survival factor for yeast cells to deter ethanol toxicity.

Role of Unsaturated Lipid and Ergosterol in Ethanol Tolerance of Model Yeast Biomembranes

KAUST Repository

Vanegas, Juan  M.; Contreras, Maria F.; Faller, Roland; Longo, Marjorie  L.

2012-01-01

We present a combined atomic force microscopy and fluorescence microscopy study of the behavior of a ternary supported lipid bilayer system containing a saturated lipid (DPPC), an unsaturated lipid (DOPC), and ergosterol in the presence of high ethanol (20 vol %). We find that the fluorescent probe Texas Red DHPE preferentially partitions into the ethanol-induced interdigitated phase, which allows the use of fluorescence imaging to investigate the phase behavior of the system. Atomic force microscopy and fluorescence images of samples with the same lipid mixture show good agreement in sample morphology and area fractions of the observed phases. Using area fractions obtained from fluorescence images over a broad range of compositions, we constructed a phase diagram of the DPPC/DOPC/ergosterol system at 20 vol % ethanol. The phase diagram clearly shows that increasing unsaturated lipid and/or ergosterol protects the membrane by preventing the formation of the interdigitated phase. This result supports the hypothesis that yeast cells increase ergosterol and unsaturated lipid content to prevent interdigitation and maintain an optimal membrane thickness as ethanol concentration increases during anaerobic fermentations. Changes in plasma membrane composition provide an important survival factor for yeast cells to deter ethanol toxicity.

An experimental program for testing the validity of flow and transport models in unsaturated tuff: The Yucca Mountain Project

International Nuclear Information System (INIS)

Shephard, L.E.; Glass, R.J.; Siegel, M.D.; Tidwell, V.C.

1990-01-01

Groundwater flow and contaminant transport through the unsaturated zone are receiving increased attention as options for waste disposal in saturated media continue to be considered as a potential means for resolving the nation's waste management concerns. An experimental program is being developed to test the validity of conceptual flow and transport models that are being formulated to predict the long-term performance at Yucca Mountain. This program is in the developmental stage and will continue to evolve as information is acquired and knowledge is improved with reference to flow and transport in unsaturated fractured media. The general approach for directing the validation effort entails identifying those processes which may cause the site to fail relative to imposed regulatory requirements, evaluating the key assumptions underlying the conceptual models used or developed to describe these processes, and developing new conceptual models as needed. Emphasis is currently being placed in four general areas: flow and transport in unsaturated fractures; fracture-matrix interactions; infiltration flow instability; and evaluation of scale effects in heterogeneous fractured media. Preliminary results and plans or each of these areas for both the laboratory and field investigation components will be presented in the manuscript. 1 ref

Pollutant transport in clayey sands: reactive flows in saturated porous media and unsaturated flows

International Nuclear Information System (INIS)

Cadalen, Sebastien

2008-01-01

In the context of nuclear risk control associated to nuclear waste storage, the french nuclear agency plays an increasing role in terms of research and development in the area of subsurface contamination. This study focuses on an homogeneous porous media constituted of Fontainebleau sand and clay grains (illite) presenting sorption capacities. The modeling of the complex geometry and physical phenomena at different scales enables us to describe the average transport at Darcy's scale. The two main axes developed are the impact of an heterogeneous sorption on transport phenomena and the dispersivity of an unsaturated porous media. (author) [fr

Adsorption of binary gas mixtures in heterogeneous carbon predicted by density functional theory: on the formation of adsorption azeotropes.

Science.gov (United States)

Ritter, James A; Pan, Huanhua; Balbuena, Perla B

2010-09-07

Classical density functional theory (DFT) was used to predict the adsorption of nine different binary gas mixtures in a heterogeneous BPL activated carbon with a known pore size distribution (PSD) and in single, homogeneous, slit-shaped carbon pores of different sizes. By comparing the heterogeneous results with those obtained from the ideal adsorbed solution theory and with those obtained in the homogeneous carbon, it was determined that adsorption nonideality and adsorption azeotropes are caused by the coupled effects of differences in the molecular size of the components in a gas mixture and only slight differences in the pore sizes of a heterogeneous adsorbent. For many binary gas mixtures, selectivity was found to be a strong function of pore size. As the width of a homogeneous pore increases slightly, the selectivity for two different sized adsorbates may change from being greater than unity to less than unity. This change in selectivity can be accompanied by the formation of an adsorption azeotrope when this same binary mixture is adsorbed in a heterogeneous adsorbent with a PSD, like in BPL activated carbon. These results also showed that the selectivity exhibited by a heterogeneous adsorbent can be dominated by a small number of pores that are very selective toward one of the components in the gas mixture, leading to adsorption azeotrope formation in extreme cases.

An XML-based loose-schema approach to managing diagnostic data in heterogeneous formats

Energy Technology Data Exchange (ETDEWEB)

Naito, O., E-mail: naito.osamu@jaea.go.j [Japan Atomic Energy Agency, 801-1 Mukouyama, Naka, Ibaraki 311-0193 (Japan)

2010-07-15

An approach to managing diagnostic data in heterogenous formats by using XML-based (eXtensible Markup Language) tag files is discussed. The tag file functions like header information in ordinary data formats but it is separate from the main body of data, human readable, and self-descriptive. Thus all the necessary information for reading the contents of data can be obtained without prior information or reading the data body itself. In this paper, modeling of diagnostic data and its representation in XML are studied and a very primitive implementation of this approach in C++ is presented. The overhead of manipulating XML in a proof-of-principle code was found to be small. The merits, demerits, and possible extensions of this approach are also discussed.

An XML-based loose-schema approach to managing diagnostic data in heterogeneous formats

International Nuclear Information System (INIS)

Naito, O.

2010-01-01

An approach to managing diagnostic data in heterogenous formats by using XML-based (eXtensible Markup Language) tag files is discussed. The tag file functions like header information in ordinary data formats but it is separate from the main body of data, human readable, and self-descriptive. Thus all the necessary information for reading the contents of data can be obtained without prior information or reading the data body itself. In this paper, modeling of diagnostic data and its representation in XML are studied and a very primitive implementation of this approach in C++ is presented. The overhead of manipulating XML in a proof-of-principle code was found to be small. The merits, demerits, and possible extensions of this approach are also discussed.

On transport in formations of large heterogeneity scales

International Nuclear Information System (INIS)

Dagan, Gedeon

1990-01-01

It has been suggested that in transport through heterogeneous aquifers, the effective dispersivity increases with the travel distance, since plumes encounter heterogeneity of increasing scales. This conclusion is underlain, however, by the assumption of ergodicity. If the plume is viewed as made up of different particles, this means that these particles move independently from a statistical point of view. To satisfy ergodicity the solute body has to be of a much larger extent than heterogeneity scales. Thus, if the latter are increasing for ever and the solute body is finite, ergodicity cannot be obeyed. To demonstrate this thesis we relate to the two-dimensional heterogeneity associated with transmissivity variations in the horizontal plane. First, the effective dispersion coefficient is defined as half the rate of change of the expected value of the solute body second spatial moment relative to its centroid. Subsequently the asymptotic large time limit of dispersivity is evaluated in terms of the log transmissivity integral scale and of the dimensions of the initial solute body in the direction of mean flow and normal to it. It is shown that for a thin plume aligned with the mean flow the effective dispersivity is zero and the effect of heterogeneity is a slight and finite expansion determined solely by the solute body size. In the case of a solute body transverse to the mean flow the effective dispersivity is different from zero, but has a maximal value which is again dependent on the solute body size and not on the heterogeneity scale. It is concluded that from a theoretical standpoint and for the definition of dispersivity adopted here for non-ergodic conditions, the claim of ever-increasing dispersivity with travel distance is not valid for the scale of heterogeneity analyzed here. (Author) (21 refs., 6 figs.)

Unsaturated fatty acids in the diet of inpatients

OpenAIRE

KONHEFROVÁ, Veronika

2015-01-01

The thesis with the name "Unsaturated fatty acids in the diet of inpatients" is divided into a theoretical and a research parts. The theoretical part is focused on sorting out lipids and the recommended daily dosing. Next there are described the chemical structure of fatty acids and basic differences between saturated (SFA) and unsaturated (trans and cis) fatty acids. The biggest part of the theory is formed by the unsaturated fatty acids, their characteristics, food source and their effect o...

The Parabolic Variational Inequalities for Variably Saturated Water Flow in Heterogeneous Fracture Networks

Directory of Open Access Journals (Sweden)

Zuyang Ye

2018-01-01

Full Text Available Fractures are ubiquitous in geological formations and have a substantial influence on water seepage flow in unsaturated fractured rocks. While the matrix permeability is small enough to be ignored during the partially saturated flow process, water seepage in heterogeneous fracture systems may occur in a non-volume-average manner as distinguished from a macroscale continuum model. This paper presents a systematic numerical method which aims to provide a better understanding of the effect of fracture distribution on the water seepage behavior in such media. Based on the partial differential equation (PDE formulations with a Signorini-type complementary condition on the variably saturated water flow in heterogeneous fracture networks, the equivalent parabolic variational inequality (PVI formulations are proposed and the related numerical algorithm in the context of the finite element scheme is established. With the application to the continuum porous media, the results of the numerical simulation for one-dimensional infiltration fracture are compared to the analytical solutions and good agreements are obtained. From the application to intricate fracture systems, it is found that water seepage flow can move rapidly along preferential pathways in a nonuniform fashion and the variably saturated seepage behavior is intimately related to the geometrical characteristics orientation of fractures.

Physiologically based in silico modelling to examine DNA adduct formation by different food-borne a,ß-unsaturated aldehydes at realistic low dietary exposure levels

NARCIS (Netherlands)

Kiwamoto, R.

2015-01-01

Abstract (R.Kiwamoto ISBN 978-94-6257-284-3)

Various α,β-unsaturated aldehydes are present in fruits, vegetables, spices, or processed products containing these items as natural constituents or as added food flavouring agents. Because of the α,β-unsaturated aldehyde moiety the β carbon in

Seepage into drifts in unsaturated fractured rock at Yucca Mountain

International Nuclear Information System (INIS)

Birkholzer, Jens; Li, Guomin; Tsang, Chin-Fu; Tsang, Yvonne

1998-01-01

An important issue for the long-term performance of underground nuclear waste repository is the rate of seepage into the waste emplacement drifts. A prediction of the future seepage rate is particularly complicated for the potential repository site at Yucca Mountain, Nevada, as it is located in thick, partially saturated, fractured tuff formations. The long-term situation in the drifts several thousand years after waste emplacement will be characterized by a relative humidity level close to or equal to 100%, as the drifts will be sealed and unventilated, and the waste packages will have cooled. The underground tunnels will then act as capillary barriers for the unsaturated flow, ideally diverting water around them, if the capillary forces are stronger than gravity and viscous forces. Seepage into the drifts will only be possible if the hydraulic pressure in the rock close to the drift walls increases to positive values; i.e., the flow field becomes locally saturated. In the present work, they have developed and applied a methodology to study the potential rate of seepage into underground cavities embedded in a variably saturated, heterogeneous fractured rock formation. The fractured rock mass is represented as a stochastic continuum where the fracture permeabilities vary by several orders of magnitude. Three different realizations of random fracture permeability fields are generated, with the random permeability structure based on extensive fracture mapping, borehole video analysis, and in-situ air permeability testing. A 3-D numerical model is used to simulate the heterogeneous steady-state flow field around the drift, with the drift geometry explicitly represented within the numerical discretization grid. A variety of flow scenarios are considered assuming present-day and future climate conditions at Yucca Mountain. The numerical study is complemented by theoretical evaluations of the drift seepage problem, using stochastic perturbation theory to develop a better

Biodiesel unsaturation degree effects on diesel engine NOx emissions and cotton wick flame temperature

Directory of Open Access Journals (Sweden)

Abdullah Mohd Fareez Edzuan

2017-01-01

Full Text Available As compared with conventional diesel fuel, biodiesel has better lubricity and lower particulate matter (PM emissions however nitrogen oxides (NOx emissions generally increase in biodiesel-fuelled diesel engine. Strict regulation on NOx emissions is being implemented in current Euro 6 standard and it is expected to be tighter in next standard, thus increase of NOx cannot be accepted. In this study, biodiesel unsaturation degree effects on NOx emissions are investigated. Canola, palm and coconut oils are selected as the feedstock based on their unsaturation degree. Biodiesel blends of B20 were used to fuel a single cylinder diesel engine and exhaust emissions were sampled directly at exhaust tailpipe with a flue gas analyser. Biodiesel flame temperature was measured from a cotton wick burned in simple atmospheric conditions using a thermocouple. Fourier transform infrared (FTIR spectrometer was also used to identify the functional groups presence in the biodiesel blends. Oxygen content in biodiesel may promote complete combustion as the NOx emissions and flame temperatures were increased while the carbon monoxide (CO emissions were decreased for all biodiesel blends. It is interesting to note that the NOx emissions and flame temperatures were directly proportional with biodiesel unsaturation degree. It might be suggested that apart from excess oxygen and free radical formation, higher NOx emissions can also be caused by the elevated flame temperatures due to the presence of double bonds in unsaturated biodiesel.

Synthesis of porphyryl boronates with (un)saturated side-chains

OpenAIRE

SENGE, MATHIAS; SERGEEVA, NATALIA

2008-01-01

PUBLISHED Porphyrins with (un)saturated side?chains containing boron residues were developed as synthons for porphyrin functionalization. Porphyrins with mono and bis-substituted unsaturated boronyl residues were prepared in good yields (52?66 %) using a cross?metathesis approach in the presence of Grubbs I-generation catalysts. In all cases complete E?stereoselectivity (100 %) was observed. Furthermore, formal cross?metathesis products with ?,??unsaturated chains smoothly underwent additi...

Heterogeneity-enhanced gas phase formation in shallow aquifers during leakage of CO2-saturated water from geologic sequestration sites

Science.gov (United States)

Plampin, Michael R.; Lassen, Rune N.; Sakaki, Toshihiro; Porter, Mark L.; Pawar, Rajesh J.; Jensen, Karsten H.; Illangasekare, Tissa H.

2014-12-01

A primary concern for geologic carbon storage is the potential for leakage of stored carbon dioxide (CO2) into the shallow subsurface where it could degrade the quality of groundwater and surface water. In order to predict and mitigate the potentially negative impacts of CO2 leakage, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2 concentration in the flowing water, the distance between the heterogeneity and the leakage location, and some fundamental properties of the porous media. Results also show that interfaces where a less permeable material overlies a more permeable material affect gas phase evolution more significantly than interfaces with the opposite layering.

Numerical simulation of the impact of water-air fronts on radionuclides plumes in heterogeneous media

International Nuclear Information System (INIS)

Aquino, J.; Francisco, A.S.; Pereira, F.; Amaral Souto, H.P.

2004-01-01

The goal of this paper is to investigate the interaction of water-air fronts with radionuclide plumes in unsaturated heterogeneous porous media. This problem is modeled by a system of equations that describes both the water-air flow and the radionuclide transport. The water-air problem is solved numerically by a mixed finite element combined with a non-oscillatory central difference scheme. For the radionuclide transport equation we use the Modified Method of Characteristics (MMOC). We present the results of numerical simulations for heterogeneous permeability fields taking into account sorption effects. (author)

Mechanochemical formation of heterogeneous diamond structures during rapid uniaxial compression in graphite

Science.gov (United States)

Kroonblawd, Matthew P.; Goldman, Nir

2018-05-01

We predict mechanochemical formation of heterogeneous diamond structures from rapid uniaxial compression in graphite using quantum molecular dynamics simulations. Ensembles of simulations reveal the formation of different diamondlike products starting from thermal graphite crystal configurations. We identify distinct classes of final products with characteristic probabilities of formation, stress states, and electrical properties and show through simulations of rapid quenching that these products are nominally stable and can be recovered at room temperature and pressure. Some of the diamond products exhibit significant disorder and partial closure of the energy gap between the highest-occupied and lowest-unoccupied molecular orbitals (i.e., the HOMO-LUMO gap). Seeding atomic vacancies in graphite significantly biases toward forming products with small HOMO-LUMO gap. We show that a strong correlation between the HOMO-LUMO gap and disorder in tetrahedral bonding configurations informs which kinds of structural defects are associated with gap closure. The rapid diffusionless transformation of graphite is found to lock vacancy defects into the final diamond structure, resulting in configurations that prevent s p3 bonding and lead to localized HOMO and LUMO states with a small gap.

At the frontier between heterogeneous and homogeneous catalysis : hydrogenation of olefins and alkynes with soluble iron nanoparticles

NARCIS (Netherlands)

Rangheard, Claudine; Julián Fernández, César de; Phua, Pim-Huat; Hoorn, Johan; Lefort, Laurent; Vries, Johannes G. de

2010-01-01

The use of non-supported Fe nanoparticles in the hydrogenation of unsaturated C–C bonds is a green catalytic concept at the frontier between homogeneous and heterogeneous catalysis. Iron nanoparticles can be obtained by reducing Fe salts with strong reductants in various solvents. FeCl3 reduced by 3

Laboratory research program to aid in developing and testing the validity of conceptual models for flow and transport through unsaturated porous media

International Nuclear Information System (INIS)

Glass, R.J.

1991-01-01

As part of the Yucca Mountain Project, a laboratory research program is being developed at Sandia National Laboratories that will integrate fundamental physical experimentation with conceptual model formulation and mathematical modeling and aid in subsequent model validation for unsaturated zone water and contaminant transport. Experimental systems are being developed to explore flow and transport processes and assumptions of fundamental importance to various conceptual models. Experimentation will run concurrently in two types of systems: fractured and nonfractured tuffaceous systems; and analogue systems having specific characteristics of the tuff systems but designed to maximize experimental control and resolution of data measurement. Areas in which experimentation currently is directed include infiltration flow instability, water and solute movement in unsaturated fractures, fracture-matrix interaction, and scaling laws to define effective large-scale properties for heterogeneous, fractured media. 16 refs

Laboratory research program to aid in developing and testing the validity of conceptual models for flow and transport through unsaturated porous media

International Nuclear Information System (INIS)

Glass, R.J.

1990-01-01

As part of the Yucca Mountain Project, a laboratory research program is being developed at Sandia National Laboratories that will integrate fundamental physical experimentation with conceptual formulation and mathematical modeling and aid in subsequent model validation for unsaturated zone water and contaminant transport. Experimental systems are being developed to explore flow and transport processes and assumptions of fundamental importance to various conceptual models. Experimentation will run concurrently in two types of systems: fractured and nonfractured tuffaceous systems; and analogue systems having specific characteristics of the tuff systems but designed to maximize experimental control and resolution of data measurement. Questions to which experimentation currently is directed include infiltration flow instability, water and solute movement in unsaturated fractures, fracture-matrix interaction, and the definition of effective large-scale properties for heterogeneous, fractured media. 16 refs

Analysis of Rainfall Infiltration Law in Unsaturated Soil Slope

OpenAIRE

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering t...

Accumulation of macular xanthophylls in unsaturated membrane domains.

Science.gov (United States)

Wisniewska, Anna; Subczynski, Witold K

2006-05-15

The distribution of macular xanthophylls, lutein and zeaxanthin, between domains formed in membranes made from an equimolar ternary mixture of dioleoylphosphatidylcholine/sphingomyelin/cholesterol, called a raft-forming mixture, was investigated. In these membranes, two domains are formed: the raft domain enriched in saturated lipids and cholesterol (detergent-resistant membranes, DRM), and the bulk domain enriched in unsaturated lipids (detergent-soluble membranes, DSM). These membrane domains have been separated using cold Triton X-100 extraction from membranes containing 1 mol% of either lutein or zeaxanthin. The results indicated that xanthophylls are substantially excluded from DRM and remain concentrated in DSM. Concentrations of xanthophylls in DRM and DSM calculated as the mole ratio of either xanthophyll to phospholipid were 0.005 and 0.03, respectively, and calculated as the mole ratio of either xanthophyll to total lipid (phospholipid + cholesterol) were 0.003 and 0.025, respectively. Thus, xanthophylls are over eight times more concentrated in DSM than in DRM. No significant difference in the distribution of lutein and zeaxanthin was found. It was also demonstrated using saturation-recovery EPR that at 1 mol%, neither lutein nor zeaxanthin affect the formation of membrane domains. The location of xanthophylls in domains formed from unsaturated lipids is ideal if they are to act as a lipid antioxidant, which is the most accepted mechanism through which lutein and zeaxanthin protect the retina from age-related macular diseases.

Unsaturated free fatty acids increase benzodiazepine receptor agonist binding depending on the subunit composition of the GABAA receptor complex.

Science.gov (United States)

Witt, M R; Westh-Hansen, S E; Rasmussen, P B; Hastrup, S; Nielsen, M

1996-11-01

It has been shown previously that unsaturated free fatty acids (FFAs) strongly enhance the binding of agonist benzodiazepine receptor ligands and GABAA receptor ligands in the CNS in vitro. To investigate the selectivity of this effect, recombinant human GABAA/benzodiazepine receptor complexes formed by different subunit compositions (alpha x beta y gamma 2, x = 1, 2, 3, and 5; y = 1, 2, and 3) were expressed using the baculovirus-transfected Sf9 insect cell system. At 10(-4) M, unsaturated FFAs, particularly arachidonic (20:4) and docosahexaenoic (22:6) acids, strongly stimulated (> 200% of control values) the binding of [3H]flunitrazepam ([3H]FNM) to the alpha 3 beta 2 gamma 2 receptor combination in whole cell preparations. No effect or small increases in levels of unsaturated FFAs on [3H]FNM binding to alpha 1 beta x gamma 2 and alpha 2 beta x gamma 2 receptor combinations were observed, and weak effects (130% of control values) were detected using the alpha 5 beta 2 gamma 2 receptor combination. The saturated FFAs, stearic and palmitic acids, were without effect on [3H]FNM binding to any combination of receptor complexes. The hydroxylated unsaturated FFAs, ricinoleic and ricinelaidic acids, were shown to decrease the binding of [3H]FNM only if an alpha 1 beta 2 gamma 2 receptor combination was used. Given the heterogeneity of the GABAA/ benzodiazepine receptor subunit distribution in the CNS, the effects of FFAs on the benzodiazepine receptor can be assumed to vary at both cellular and regional levels.

Imaging and Measurements of Flow Phenomena and Impact of Soil Associated Constituents Through Unsaturated Porous Media in a 2D System

Science.gov (United States)

Pales, A. R.; Li, B.; Clifford, H.; Edayilam, N.; Montgomery, D.; Dogan, M.; Tharayil, N.; Martinez, N. E.; Moysey, S. M.; Darnault, C. J. G.

2016-12-01

This research aims to build upon past two-dimension (2D) tank light transmission methods to quantify real-time flow in unsaturated porous media (ASTM silica sand; US Silica, Ottawa, IL, USA) and how exudates effect unstable flow patterns. A 2D tank light transmission method was created using a transparent flow through tank coupled with a random rainfall simulator; a commercial LED light and a complementary metal oxide semiconductor digital single lens reflex (CMOS DSLR) Nikon D5500 camera were used to capture the real-time flow images. The images were broken down from red-green-blue (RGB) into hue-saturation-intensity (HVI) and analyzed in Matlab to produce quantifiable data about finger formation and water saturation distribution. Contact angle and surface tension of the chemical plant exudate solutions was measured using a Kruss EasyDrop FM40Mk2 (Kruss GmbH Germany). The exudates (oxalate, citrate, tannic acid, and Suwannee River Natural Organic Matter) had an increased wettability effect compared to control rain water (0.01M NaCl). This resulted in variable finger formation and speed of finger propagation; dependent on exudate type and concentration. Water saturation along the vertical and horizontal profile (Matlab) was used to quantify the finger more objectively than by eye assessment alone. The changes in finger formation and speed of propagation between the control rain water (0.01M NaCl) and the solutions containing plant exudates illustrates that the plant exudates increased the wettability (mobility) of water moving through unsaturated porous media. This understanding of plant exudates effect on unsaturated flow is important for future works in this study to analyze how plants, their roots and exudates, may affect the mobility of radionuclides in unsaturated porous media.

Pumping Test Determination of Unsaturated Aquifer Properties

Science.gov (United States)

Mishra, P. K.; Neuman, S. P.

2008-12-01

Tartakovsky and Neuman [2007] presented a new analytical solution for flow to a partially penetrating well pumping at a constant rate from a compressible unconfined aquifer considering the unsaturated zone. In their solution three-dimensional, axially symmetric unsaturated flow is described by a linearized version of Richards' equation in which both hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value, the latter defining the interface between the saturated and unsaturated zones. Both exponential functions are characterized by a common exponent k having the dimension of inverse length, or equivalently a dimensionless exponent kd=kb where b is initial saturated thickness. The authors used their solution to analyze drawdown data from a pumping test conducted by Moench et al. [2001] in a Glacial Outwash Deposit at Cape Cod, Massachusetts. Their analysis yielded estimates of horizontal and vertical saturated hydraulic conductivities, specific storage, specific yield and k . Recognizing that hydraulic conductivity and water content seldom vary identically with incremental capillary pressure head, as assumed by Tartakovsky and Neuman [2007], we note that k is at best an effective rather than a directly measurable soil parameter. We therefore ask to what extent does interpretation of a pumping test based on the Tartakovsky-Neuman solution allow estimating aquifer unsaturated parameters as described by more common constitutive water retention and relative hydraulic conductivity models such as those of Brooks and Corey [1964] or van Genuchten [1980] and Mualem [1976a]? We address this question by showing how may be used to estimate the capillary air entry pressure head k and the parameters of such constitutive models directly, without a need for inverse unsaturated numerical simulations of the kind described by Moench [2003]. To assess the validity of such direct estimates we use maximum

Deuterium labelling studies with unsaturated acids and nitriles

International Nuclear Information System (INIS)

Desai, U.V.; Mane, R.B.

1986-01-01

α-Deuteriated α,β-unsaturated acids have been prepared by Knoevenagel condensation of aldehydes with deuteriated malonic acid. The decarboxylation of α,β-unsaturated cyano acid with pyridine/D 2 O yields α- and γ-labelled nitriles. The deuterium incorporation is studied by pmr spectroscopy. (author). 8 refs

Vertical hydrochemical profiles in the unsaturated zone of louga ...

African Journals Online (AJOL)

Solutions chemistry of the rainwater and the unsaturated zone interstitial water of Louga (Northern Senegal) local aquifer provide valuable ... together with chemical analysis of the interstitial water carried out through the entire unsaturated ...

Electrokinetic extraction of chromate from unsaturated soils

International Nuclear Information System (INIS)

Mattson, E.D.; Lindgren, E.R.

1993-01-01

Heavy-metal contamination of soil and groundwater is a widespread problem in industrial nations. Remediation by excavation of such sites may not be cost effective or politically acceptable. Electrokinetic remediation is one possible remediation technique for in situ removal of such contaminants from unsaturated soils. Previous papers discussing the work performed by researchers at Sandia National Laboratories (SNL) and Sat-Unsat, Inc. (SUI) (Lindgren et al., 1991, 1992, 1993) focused on the transport of contaminants and dyes by electrokinetics in unsaturated soils. These experiments were conducted with graphite electrodes with no extraction system. As the contaminants migrated through the soil, they increased in concentration at the electrode creating a diffusion flux in the opposite direction. This paper discusses a technique to remove the contaminants from unsaturated soils once they have reached an electrode

Electrokinetic extraction of chromate from unsaturated soils

Energy Technology Data Exchange (ETDEWEB)

Mattson, E.D. [SAT-UNSAT, Inc., Albuquerque, NM (United States); Lindgren, E.R. [Sandia National Labs., Albuquerque, NM (United States)

1993-11-01

Heavy-metal contamination of soil and groundwater is a widespread problem in industrial nations. Remediation by excavation of such sites may not be cost effective or politically acceptable. Electrokinetic remediation is one possible remediation technique for in situ removal of such contaminants from unsaturated soils. Previous papers discussing the work performed by researchers at Sandia National Laboratories (SNL) and Sat-Unsat, Inc. (SUI) (Lindgren et al., 1991, 1992, 1993) focused on the transport of contaminants and dyes by electrokinetics in unsaturated soils. These experiments were conducted with graphite electrodes with no extraction system. As the contaminants migrated through the soil, they increased in concentration at the electrode creating a diffusion flux in the opposite direction. This paper discusses a technique to remove the contaminants from unsaturated soils once they have reached an electrode.

Conceptualization of a hypothetical high-level nuclear waste repository site in unsaturated, fractured tuff

International Nuclear Information System (INIS)

Parsons, A.M.; Olague, N.E.; Gallegos, D.P.

1991-01-01

Under the sponsorship of the US Nuclear Regulatory Commission (NRC), Sandia National Laboratories (SNL) is developing a performance assessment methodology for the analysis of long-term disposal and isolation of high-level nuclear wastes (HLW) in alternative geologic media. As part of this exercise, SNL created a conceptualization of ground-water flow and radionuclide transport in the far field of a hypothetical HLW repository site located in unsaturated, fractured tuff formations. This study provides a foundation for the development of conceptual mathematical, and numerical models to be used in this performance assessment methodology. This conceptualization is site specific in terms of geometry, the regional ground-water flow system, stratigraphy, and structure in that these are based on information from Yucca Mountain located on the Nevada Test Site. However, in terms of processes in unsaturated, fractured, porous media, the model is generic. This report also provides a review and evaluation of previously proposed conceptual models of unsaturated and saturated flow and solute transport. This report provides a qualitative description of a hypothetical HLW repository site in fractured tuff. However, evaluation of the current knowledge of flow and transport at Yucca Mountain does not yield a single conceptual model. Instead, multiple conceptual models are possible given the existing information

Conceptualization of a hypothetical high-level nuclear waste repository site in unsaturated, fractured tuff

Energy Technology Data Exchange (ETDEWEB)

Parsons, A.M.; Olague, N.E.; Gallegos, D.P. [Sandia National Labs., Albuquerque, NM (USA)

1991-01-01

Under the sponsorship of the US Nuclear Regulatory Commission (NRC), Sandia National Laboratories (SNL) is developing a performance assessment methodology for the analysis of long-term disposal and isolation of high-level nuclear wastes (HLW) in alternative geologic media. As part of this exercise, SNL created a conceptualization of ground-water flow and radionuclide transport in the far field of a hypothetical HLW repository site located in unsaturated, fractured tuff formations. This study provides a foundation for the development of conceptual mathematical, and numerical models to be used in this performance assessment methodology. This conceptualization is site specific in terms of geometry, the regional ground-water flow system, stratigraphy, and structure in that these are based on information from Yucca Mountain located on the Nevada Test Site. However, in terms of processes in unsaturated, fractured, porous media, the model is generic. This report also provides a review and evaluation of previously proposed conceptual models of unsaturated and saturated flow and solute transport. This report provides a qualitative description of a hypothetical HLW repository site in fractured tuff. However, evaluation of the current knowledge of flow and transport at Yucca Mountain does not yield a single conceptual model. Instead, multiple conceptual models are possible given the existing information.

Movement of radionuclides through unsaturated soils

International Nuclear Information System (INIS)

de Sousa, F.N.C.

1985-01-01

The advantages of the disposal of low-level radioactive wastes in the unsaturated zone above the fluctuations of the water table have been recognized for some time. However, most the numerical models used to simulate the environmental impact of a shallow land burial site assume that the soils surrounding the waste forms are saturated; this assumption may lead, in many cases, to unrealistic large leach and water flow rates. The main purpose of this study was the development of a procedure which could give a reliable prediction on the movement of radionuclides from shallow land burial sites located in the unsaturated zone. In order to accomplish this objective three different soils having different sand, silt, and clay fractions were selected and characterized. These soils were then used to fill a number of flow columns that were used in tests designed to provide input data for the flow and transport models. A one-dimensional finite element model was developed in order to simulate the water flow and radionuclide transport through unsaturated soils. The results obtained showed that the model accurately described the transport of radionuclides through saturated-unsaturated soils. Simulations were done, for all three soils, involving different degrees of soil saturation, and the results showed that assuming the soils are always saturated may lead to nuclide transport times which are orders of magnitude larger than the real ones, depending on the clay percentage present in the soil

Seismic response of earth dams considering dynamic properties of unsaturated zone

Directory of Open Access Journals (Sweden)

Ariyan M.

2016-01-01

Full Text Available It is conventionally assumed in the analysis and design of earth dams that the soil located above the phreatic line, i.e. the uppermost seepage flow line, is completely dry. However, there is often an unsaturated flow of water through an unsaturated zone above this borderline and variation in moisture content in this zone results in variation of matric suction throughout this region. Variation of matric suction, in turn, results in variation of effective stresses in this zone. In this research, the seismic response of earth dams in terms of the displacement and acceleration at the crown of the dam as well as the stress distribution in the dam body is investigated. Taking into account the effect of unsaturated zone, a comparison is made to investigate the effect of conventional simplification in ignoring the dynamic characteristics of the unsaturated zone above the phreatic line and the more complicated analysis which includes the unsaturated zone. A function for the soil-water retention curve (SWRC was assigned to the soil in the unsaturated zone to determine the variation of matric suction in this zone and analyses were made using finite difference software (FLAC. Results are then compared to the conventional method for homogeneous dams. In these analyzes the soil shear modulus was assumed to vary with the mean effective stress both for saturated and unsaturated zones. Among various results, it was notable that the history of crest x-displacement, and acceleration show higher values in models accounting for the unsaturated region. It was attributed to the considerably lower values of damping ratio in the crest region in the unsaturated models.

Infiltration in Unsaturated Soils

DEFF Research Database (Denmark)

Ghotbi, Abdoul R.; Omidvar, M.; Barari, Amin

2011-01-01

An approximate analytical solution has been established for the well known Richards’ equation for unsaturated flow of transports in soils. Despite the importance of Richards’ equation in geotechnical and geoenvironmental applications, most solutions to the problem are generally based on numerical...

Characterization of unsaturated hydraulic conductivity at the Hanford Site

Energy Technology Data Exchange (ETDEWEB)

Rockhold, M.L.; Fayler, M.J.; Gee, G.W.

1988-07-01

This report details some recent field measurements and compares predicted and measured values of hydraulic conductivities for three locations at the Hanford Site. Measurements from small (6-cm-dia) /open quotes/point/close quotes/ and large (2-m by 2-m) /open quotes/plot/close quotes/ areas utilized inflitration and drainage techniques to obtain in situ data for field-saturated and unsaturated hydraulic conductivity. The Guelph permeameter was used for point sampling, and the unsteady drainage-flux method was used on plots for field-saturated and unsaturated hydraulic conductivity measurements. Steady-state techniques were used to measure unsaturated hydraulic conductivities in small columns in the laboratory for one of the three soils tested to provide a comparison with data obtained from the field. Measured unsaturated hydraulic conductivities and those predicted from particle-size distribution and bulk density data agree within one-half to one and one-half orders of magnitude, depending on soil type. To use a particle-size distribution to estimate water retention characteristics and, subsequently, to predict unsaturated hydraulic conductivities, measurements of water-retention characteristics are necessary to determine a parameter value used in one of the models. No single method for measuring or calculating unsaturated hydraulic conductivities was found appropriate for all Hanford Site soils. Ideally, several methods should be used to take advantage of the strengths of each method, considering the data needs and resources available. 45 refs., 24 figs., 19 tabs.

Characterization of unsaturated hydraulic conductivity at the Hanford Site

International Nuclear Information System (INIS)

Rockhold, M.L.; Fayler, M.J.; Gee, G.W.

1988-07-01

This report details some recent field measurements and compares predicted and measured values of hydraulic conductivities for three locations at the Hanford Site. Measurements from small (6-cm-dia) /open quotes/point/close quotes/ and large (2-m by 2-m) /open quotes/plot/close quotes/ areas utilized inflitration and drainage techniques to obtain in situ data for field-saturated and unsaturated hydraulic conductivity. The Guelph permeameter was used for point sampling, and the unsteady drainage-flux method was used on plots for field-saturated and unsaturated hydraulic conductivity measurements. Steady-state techniques were used to measure unsaturated hydraulic conductivities in small columns in the laboratory for one of the three soils tested to provide a comparison with data obtained from the field. Measured unsaturated hydraulic conductivities and those predicted from particle-size distribution and bulk density data agree within one-half to one and one-half orders of magnitude, depending on soil type. To use a particle-size distribution to estimate water retention characteristics and, subsequently, to predict unsaturated hydraulic conductivities, measurements of water-retention characteristics are necessary to determine a parameter value used in one of the models. No single method for measuring or calculating unsaturated hydraulic conductivities was found appropriate for all Hanford Site soils. Ideally, several methods should be used to take advantage of the strengths of each method, considering the data needs and resources available. 45 refs., 24 figs., 19 tabs

Analysis of rainfall infiltration law in unsaturated soil slope.

Science.gov (United States)

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θs - θr), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process.

Interpretation of chemical and isotopic data from boreholes in the unsaturated zone at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Yang, I.C.; Rattray, G.W.; Yu, P.

1996-01-01

Analyses of pore water from boreholes at Yucca Mountain indicate that unsaturated-zone pore water has significantly larger concentrations of chloride and dissolved solids than the saturated-zone water or perched-water bodies. Chemical compositions are of the calcium sulfate or calcium chloride types in the Paintbrush Group (Tiva Canyon, Yucca Mountain, Pah Canyon, and bedded tuffs), and sodium carbonate or bicarbonate type water in the Calico Hills Formation. Tritium profiles from boreholes at Yucca Mountain indicate tritium-concentration inversions (larger tritium concentrations are located below the smaller tritium concentration in a vertical profile) occur in many places. These inversions indicate preferential flow through fractures. Rock-gas compositions are similar to that of atmospheric air except that carbon dioxide concentrations are generally larger than those in the air. The delta carbon-13 values of gas are fairly constant from surface to 365.8 meters, indicating little interaction between the gas CO 2 and caliche in the soil. Model calculations indicate that the gas transport in the unsaturated zone at Yucca Mountain agrees well with the gas-diffusion process. Tritium-modeling results indicate that the high tritium value of about 100 tritium units in the Calico Hills Formation of UZ-16 is within limits of a piston-flow model with a water residence time of 32 to 35 years. The large variations in tritium concentrations with narrow peaks imply piston flow or preferential fracture flow rather than matrix flow. In reality, the aqueous-phase flow in the unsaturated zone is between piston and well-mixed flows but is closer to a piston flow

Formation of nitro-PAHs from the heterogeneous reaction of ambient particle-bound PAHs with NO3/N2O5

Science.gov (United States)

Zimmermann, K.; Jariyasopit, N.; Simonich, S. L.; Atkinson, R.; Arey, J.

2012-12-01

Polycyclic aromatic hydrocarbons (PAHs) and their nitrated derivatives (nitro-PAHs) have been shown to be mutagenic in bacterial and mammalian assays and are classified as probable human carcinogens. Semi-volatile PAHs partition between the gas and particulate phases, depending on their liquid-phase vapor pressures and ambient temperatures. These PAHs have been extensively measured in ambient particulate matter and can ultimately undergo long-range transport from source regions (e.g., China to the western USA) (1). During transport these particle-bound PAHs may undergo reaction with NO3/N2O5 to form nitro-PAH derivatives. Previous studies of heterogeneous nitration of PAHs have used particles composed of graphite, diesel soot, and wood smoke (2-4). This study investigates the heterogeneous formation of nitro-PAHs from ambient particle-bound PAHs from Beijing, China and sites located within the Los Angeles air basin. These ambient particle samples, along with filters coated with isotopically labeled PAHs, were exposed to a mix of NO2/NO3/N2O5 in a 7000 L Teflon chamber, with analysis focused on the heterogeneous formation of molecular weight 247 and 273 nitro-PAHs. The heterogeneous formation of certain nitro-PAHs (including1-nitropyrene and 1- and 2-nitrotriphenylene) was observed for some, but not all, ambient samples. Formation of nitro-PAHs typically formed through gas-phase reactions (2-nitrofluoranthene and 2-nitropyrene) was not observed. The effect of particle age and local photochemical conditions during sampling on the degree of nitration in environmental chamber reactions, as well as ambient implications, will be presented. 1. Primbs, T.; Simonich, S.; Schmedding, D.; Wilson, G.; Jaffe, D.; Takami, A.; Kato, S.; Hatakeyama, S.; Kajii, Y. Environ. Sci. Technol. 2007, 41, 3551-3558. 2. Esteve, W.; Budzinski, H.; Villenave, E. Atmospheric Environment 2004, 38, 6063-6072. 3. Nguyen, M.; Bedjanian, Y.; Guilloteau, A. Journal of Atmospheric Chemistry 2009, 62

Mechanisms for formation of organic acids in gas-phase reactions of ozone and hydroxyl radical with dialkenes and unsaturated carbonyls

Science.gov (United States)

Chien, Chao-Jung

2001-07-01

Carboxylic acids are ubiquitous throughout the troposphere and may contribute significant fractions of the free acidity in some remote areas. One of the important sources of these carboxylic acids is thought to be photochemical transformation of biogenic hydrocarbons such as isoprene. For the work reported here, atmospheric samples from University of North Carolina dual outdoor environmental chamber under simulated urban atmospheric conditions were analyzed for carboxylic acids. Both OH radicals and O3 initiated photooxidation reaction experiments were performed for isoprene, along with its structural analogs, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene, and their primary photooxidation products, methacrolein, acrolein, and methyl vinyl ketone. Among the detected carboxylic acids were formic, acetic, and several multifunctional carboxylic acids, including methacrylic, acrylic, glyoxylic, and glycolic acids. Quantification of most carboxylic acid products was also established. Formation yields of carboxylic acids from the reactions of O3 with studied compounds were determined, and time-concentration series of the reactants and carboxylic acid products were measured to facilitate mechanism formulation. While the reaction mechanisms of Criegee biradicals arising from decomposition of primary ozonides are proposed to account for the observed carboxylic acid products in the ozonolysis of unsaturated hydrocarbons, reactions of peroxy acyl radicals with HO2 and/or other peroxy radicals are thought to be responsible for the formation of carboxylic acids during the OH-initiated reactions in the presence of NOx. In this study, smog chamber simulations have also been performed for selected compounds using Morpho, a photochemical kinetic simulation software package. Explicit photochemical mechanisms with O 3 and OH radicals that lead to formation of carboxylic acids were elaborated and implemented, and the simulation results were compared with those from other chemical

Principles of Physical Modelling of Unsaturated Soils

OpenAIRE

CAICEDO, Bernardo; THOREL, Luc

2014-01-01

Centrifuge modelling has been widely used to simulate the performance of a variety of geotechnical works, most of them focusing on saturated clays or dry sands. On the other hand, the performance of some geotechnical works depends on the behaviour of shallow layers in the soil deposit where it is frequently unsaturated. Centrifuge modelling could be a powerful tool to study the performance of shallow geotechnical works. However all the experimental complexities related to unsaturated soils, w...

Assimilation of ambient seismic noise in hydrological models allows estimation of hydraulic conductivity in unsaturated media

Science.gov (United States)

Fores, B.; Champollion, C.; Mainsant, G.; Fort, A.; Albaric, J.

2016-12-01

Karstic hydrosystems represent one of the main water resources in the Mediterranean area but are challenging for geophysical methods. The GEK (Geodesy in Karstic Environment) observatory has been setup in 2011 to study the unsaturated zone of a karstic system in the south of France. The unsaturated zone (the epikarst) is thick and up to 100m on the site. Since 2011, gravity, rainfall and evapotranspiration are monitored. Together, they allow precise estimation of the global water storage changes but lack depth resolution. Surface waves velocity variations, obtained from ambient seismic noise monitoring are used here to overcome this lack. Indeed, velocities depend on saturation and the depths where changes occur can be defined as surface waves are dispersive. From October 2014 to November 2015, two seismometers have been recording noise. Velocity changes at a narrow frequency band (6-8 Hz) have shown a clear annual cycle. Minimum velocity is several months late on precipitations, which is coherent with a slow infiltration and a maximum sensitivity at -40m for these frequencies and this site. Models have been made with the Hydrus-1D software which allows modeling 1D-flow in variably saturated media. With a stochastic sampling, we have researched the underground parameters that reproduce the most the different observations (gravity, evapotranspiration and rainfall, and velocity changes). We show that velocity changes clearly constrain the hydraulic conductivity of the medium. Ambient seismic noise is therefore a promising method to study unsaturated zone which are too deep or too heterogeneous for classic methods.

Quantifying Preferential Flow and Seasonal Storage in an Unsaturated Fracture-Facial Domain

Science.gov (United States)

Nimmo, J. R.; Malek-Mohammadi, S.

2012-12-01

Preferential flow through deep unsaturated zones of fractured rock is hydrologically important to a variety of contaminant transport and water-resource issues. The unsaturated zone of the English Chalk Aquifer provides an important opportunity for a case study of unsaturated preferential flow in isolation from other flow modes. The chalk matrix has low hydraulic conductivity and stays saturated, owing to its fine uniform pores and the wet climate of the region. Therefore the substantial fluxes observed in the unsaturated chalk must be within fractures and interact minimally with matrix material. Price et al. [2000] showed that irregularities on fracture surfaces provide a significant storage capacity in the chalk unsaturated zone, likely accounting for volumes of water required to explain unexpected dry-season water-table stability during substantial continuing streamflow observed by Lewis et al. [1993] In this presentation we discuss and quantify the dynamics of replenishment and drainage of this unsaturated zone fracture-face storage domain using a modification of the source-responsive model of Nimmo [2010]. This model explains the processes in terms of two interacting flow regimes: a film or rivulet preferential flow regime on rough fracture faces, active on an individual-storm timescale, and a regime of adsorptive and surface-tension influences, resembling traditional diffuse formulations of unsaturated flow, effective mainly on a seasonal timescale. The modified model identifies hydraulic parameters for an unsaturated fracture-facial domain lining the fractures. Besides helping to quantify the unsaturated zone storage described by Price et al., these results highlight the importance of research on the topic of unsaturated-flow relations within a near-fracture-surface domain. This model can also facilitate understanding of mechanisms for reinitiation of preferential flow after temporary cessation, which is important in multi-year preferential flow through deep

Dispersal networks for enhancing bacterial degradation in heterogeneous environments

International Nuclear Information System (INIS)

Banitz, Thomas; Wick, Lukas Y.; Fetzer, Ingo; Frank, Karin; Harms, Hauke; Johst, Karin

2011-01-01

Successful biodegradation of organic soil pollutants depends on their bioavailability to catabolically active microorganisms. In particular, environmental heterogeneities often limit bacterial access to pollutants. Experimental and modelling studies revealed that fungal networks can facilitate bacterial dispersal and may thereby improve pollutant bioavailability. Here, we investigate the influence of such bacterial dispersal networks on biodegradation performance under spatially heterogeneous abiotic conditions using a process-based simulation model. To match typical situations in polluted soils, two types of abiotic conditions are studied: heterogeneous bacterial dispersal conditions and heterogeneous initial resource distributions. The model predicts that networks facilitating bacterial dispersal can enhance biodegradation performance for a wide range of these conditions. Additionally, the time horizon over which this performance is assessed and the network's spatial configuration are key factors determining the degree of biodegradation improvement. Our results support the idea of stimulating the establishment of fungal mycelia for enhanced bioremediation of polluted soils. - Highlights: → Bacterial dispersal networks can considerably improve biodegradation performance. → They facilitate bacterial access to dispersal-limited areas and remote resources. → Abiotic conditions, time horizon and network structure govern the improvements. → Stimulating the establishment of fungal mycelia promises enhanced soil remediation. - Simulation modelling demonstrates that fungus-mediated bacterial dispersal can considerably improve the bioavailability of organic pollutants under spatially heterogeneous abiotic conditions typical for water-unsaturated soils.

Dispersal networks for enhancing bacterial degradation in heterogeneous environments

Energy Technology Data Exchange (ETDEWEB)

Banitz, Thomas, E-mail: thomas.banitz@ufz.de [Department of Ecological Modelling, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Wick, Lukas Y.; Fetzer, Ingo [Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Frank, Karin [Department of Ecological Modelling, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Harms, Hauke [Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Johst, Karin [Department of Ecological Modelling, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany)

2011-10-15

Successful biodegradation of organic soil pollutants depends on their bioavailability to catabolically active microorganisms. In particular, environmental heterogeneities often limit bacterial access to pollutants. Experimental and modelling studies revealed that fungal networks can facilitate bacterial dispersal and may thereby improve pollutant bioavailability. Here, we investigate the influence of such bacterial dispersal networks on biodegradation performance under spatially heterogeneous abiotic conditions using a process-based simulation model. To match typical situations in polluted soils, two types of abiotic conditions are studied: heterogeneous bacterial dispersal conditions and heterogeneous initial resource distributions. The model predicts that networks facilitating bacterial dispersal can enhance biodegradation performance for a wide range of these conditions. Additionally, the time horizon over which this performance is assessed and the network's spatial configuration are key factors determining the degree of biodegradation improvement. Our results support the idea of stimulating the establishment of fungal mycelia for enhanced bioremediation of polluted soils. - Highlights: > Bacterial dispersal networks can considerably improve biodegradation performance. > They facilitate bacterial access to dispersal-limited areas and remote resources. > Abiotic conditions, time horizon and network structure govern the improvements. > Stimulating the establishment of fungal mycelia promises enhanced soil remediation. - Simulation modelling demonstrates that fungus-mediated bacterial dispersal can considerably improve the bioavailability of organic pollutants under spatially heterogeneous abiotic conditions typical for water-unsaturated soils.

Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation

Directory of Open Access Journals (Sweden)

P. O. Wennberg

2010-08-01

Full Text Available Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene, the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA via methacrolein (a C4-unsaturated aldehyde under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN as the important intermediate to isoprene and methacrolein SOA in this NOx regime. Here we show that as a result of this chemistry, NO2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NOx effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232 is insignificant, even under high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(OOONO2 formation is structurally unfavorable. At atmospherically relevant NO2/NO ratios (3–8, the SOA yields from isoprene high-NOx photooxidation are 3 times greater than previously measured at lower NO2/NO ratios. At sufficiently high NO2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO2 can exceed that from RO2+HO2 reactions under the same inorganic seed conditions, making RO2+NO2 an important channel for SOA formation.

Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation

Science.gov (United States)

Chan, A. W. H.; Chan, M. N.; Surratt, J. D.; Chhabra, P. S.; Loza, C. L.; Crounse, J. D.; Yee, L. D.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H.

2010-08-01

Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA) via methacrolein (a C4-unsaturated aldehyde) under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN) as the important intermediate to isoprene and methacrolein SOA in this NOx regime. Here we show that as a result of this chemistry, NO2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NOx effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232) is insignificant, even under high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(O)OONO2) formation is structurally unfavorable. At atmospherically relevant NO2/NO ratios (3-8), the SOA yields from isoprene high-NOx photooxidation are 3 times greater than previously measured at lower NO2/NO ratios. At sufficiently high NO2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO2 can exceed that from RO2+HO2 reactions under the same inorganic seed conditions, making RO2+NO2 an important channel for SOA formation.

Structure of products of the condensation of α,β-unsaturated aldehydes with dimedone

International Nuclear Information System (INIS)

Yurchenko, O.I.; Pushkareva, K.S.; Zheldubovskaya, G.A.; Komarov, N.V.; Berkova, G.A.

1987-01-01

α,β-Acetylenic aldehydes and cinnamaldehyde in reaction with dimedone give the corresponding unsaturated bis(dimedonyl)methanes. In the case of acrolein and crotonaldehyde intramolecular cyclization occurs with the participation of hydroxyl of the dimedone fragment and the double bond with the formation of pyran systems. The PMR spectra were determined on Tesla BS-487C (80 MHz) and Tesla BS-467C (60 MHz) spectrometers in chloroform-d, pyridine-d 5 , and trifluoroacetic acid solutions. Internal standards HMDS and methylene chloride

Virus movement in soil during saturated and unsaturated flow.

Science.gov (United States)

Lance, J C; Gerba, C P

1984-02-01

Virus movement in soil during saturated and unsaturated flow was compared by adding poliovirus to sewage water and applying the water at different rates to a 250-cm-long soil column equipped with ceramic samplers at different depths. Movement of viruses during unsaturated flow of sewage through soil columns was much less than during saturated flow. Viruses did not move below the 40-cm level when sewage water was applied at less than the maximum infiltration rate; virus penetration in columns flooded with sewage was at least 160 cm. Therefore, virus movement in soils irrigated with sewage should be less than in flooded groundwater recharge basins or in saturated soil columns. Management of land treatment systems to provide unsaturated flow through the soil should minimize the depth of virus penetration. Differences in virus movement during saturated and unsaturated flow must be considered in the development of any model used to simulate virus movement in soils.

1DFEMWATER: A one-dimensional finite element model of WATER flow through saturated-unsaturated media

International Nuclear Information System (INIS)

Yeh, G.T.

1988-08-01

This report presents the development and verification of a one- dimensional finite element model of water flow through saturated- unsaturated media. 1DFEMWATER is very flexible and capable of modeling a wide range of real-world problems. The model is designed to (1) treat heterogeneous media consisting of many geologic formations; (2) consider distributed and point sources/sinks that are spatially and temporally variable; (3) accept prescribed initial conditions or obtain them from steady state simulations; (4) deal with transient heads distributed over the Dirichlet boundary; (5) handle time-dependent fluxes caused by pressure gradient on the Neumann boundary; (6) treat time-dependent total fluxes (i.e., the sum of gravitational fluxes and pressure-gradient fluxes) on the Cauchy boundary; (7) automatically determine variable boundary conditions of evaporation, infiltration, or seepage on the soil-air interface; (8) provide two options for treating the mass matrix (consistent and lumping); (9) provide three alternatives for approximating the time derivative term (Crank-Nicolson central difference, backward difference, and mid-difference); (10) give three options (exact relaxation, underrelaxation, and overrelaxation) for estimating the nonlinear matrix; (11) automatically reset the time step size when boundary conditions or source/sinks change abruptly; and (12) check mass balance over the entire region for every time step. The model is verified with analytical solutions and other numerical models for three examples

Inter-chromosomal heterogeneity in the formation of radiation induced chromosomal aberrations

International Nuclear Information System (INIS)

Natarajan, A.T.; Vermeulen, S.; Boei, J.J.W.A.

1997-01-01

It is generally assumed that radiation induced chromosomal lesions are distributed randomly and repaired randomly among the genome. Recent studies using fluorescent in situ hybridization (FISH) and chromosome specific DNA libraries indicate that some chromosomes are more sensitive for radiation induced aberration formation than others. Chromosome No. 4 in human and chromosome No. 8 in Chinese hamster have been found to involve more in exchange aberrations than others, when calculated on the basis of their DNA content. Painting with arm specific chromosome libraries indicate that the frequencies of radiation induced intra-chromosome exchanges (i.e., between the arms of a chromosome, such as centric rings and inversions) are far in excess than one would expect on the basis of the frequencies of observed inter-chromosomal exchanges. The possible factors leading to the observed heterogeneity will be discussed

Study on the formation of heterogeneous structures in leached layers during the corrosion process of glass

Directory of Open Access Journals (Sweden)

Willemien Anaf

2010-11-01

Full Text Available Le verre, corrodé dans des conditions naturelles, montre souvent des hétérogénéités dans la couche lixiviée, comme une structure lamellaire ou des inclusions de MnO2 ou Ca3(PO42. La formation de ces hétérogénéités n’est pas encore bien comprise. Des structures de ce type ont été produites artificiellement en laboratoire en immergeant des échantillons de verre dans des solutions riches en métaux. Les résultats expérimentaux ont été comparés avec des théories décrivant la corrosion du verre.Glass that corrodes under natural conditions often shows heterogeneities in the leached layer, such as a lamellar structure or inclusions of MnO2 or Ca3(PO42. The formation of these heterogeneities is still not well understood. By means of experiments under laboratory conditions, our aim was to artificially generate specific structures. Therefore, glass samples were immersed in metal-rich solutions. The experimental results were compared with theories describing glass corrosion from a molecular point of view.

Waste migration in shallow burial sites under unsaturated flow conditions

International Nuclear Information System (INIS)

Eicholz, G.G.; Whang, J.

1987-01-01

Unsaturated conditions prevail in many shallow-land burial sites, both in arid and humid regions. Unless a burial site is allowed to flood and possibly overflow, a realistic assessment of any migration scenario must take into account the conditions of unsaturated flow. These are more difficult to observe and to model, but introduce significant changes into projected rates of waste leaching and waste migration. Column tests have been performed using soils from the Southeastern coastal plain to observe the effects of varying degrees of ''unsaturation'' on the movement of radioactive tracers. The moisture content in the columns was controlled by maintaining various levels of hydrostatic suction on soil columns whose hydrodynamic characteristics had been determined carefully. Tracer tests, employing Cs-137, I-131 and Ba-133 were used to determine migration profiles and to follow their movement down the column for different suction values. A calculational model has been developed for unsaturated flow and seems to match the observations fairly well. It is evident that a full description of migration processes must take into account the reduced migration rates under unsaturated conditions and the hysteresis effects associated with wetting-drying cycles

Flow modelling and radionuclide transport research and development in saturated and unsaturated soils

International Nuclear Information System (INIS)

Carvalho Filho, Carlos Alberto de; Branco, Otavio Eurico de Aquino; Loureiro, Celso de Oliveira

1996-01-01

The Engenho Nogueira Hydrogeological Project, PROHBEN, was idealized with the goal of implementing an Experimental Hydrogeological basin within its limits, in order to permit the development of hydrogeological studies and techniques, mainly in the modeling of flow and transport of contaminants (radionuclides) in the saturated and unsaturated porous media. The PROHBEN is located in Belo Horizonte, Minas Gerais, amounting a 5 km 2 area. The local porous-granular, heterogeneous and anisotropic, water-table aquifer reaches 40 meters of thickness, and is compound mainly by alluvial deposits and alteration rocks products, with a sandy texture. The flow and transport modeling are being done using the Modflow and MT3D codes. Three master degree researches are being done in the PROHBEN area and one expects is that more researchers come to use this experimental site. (author)

Heterogeneous Formation of Polar Stratospheric Clouds- Part 1: Nucleation of Nitric Acid Trihydrate (NAT)

Science.gov (United States)

Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooss, J.-U.; Peter, T.

2013-01-01

Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

A framework for the behaviour of unsaturated expansive clays

International Nuclear Information System (INIS)

Gens, A.; Alonso, E.E.

1992-01-01

The paper presents a framework for describing the mechanical behaviour of unsaturated expansive clays. It is an extension of an existing formulation developed for unsaturated soils of low activity. The extended framework is based on the distinction within the material of a microstructural level where the basic swelling of the active minerals takes place, and a macrostructural level responsible for major structural rearrangements. Bu adopting simple assumptions concerning the coupling between the two levels, it is possible to reproduce major features of the behaviour of unsaturated expansive clays. Some selected qualitative comparisons between model predictions and experimental results reported in the literature are presented. Despite the simplified hypotheses made, a very encouraging agreement is obtained

Effect of Unsaturated Flow on Delayed Response of Unconfined Aquifiers to Pumping

Science.gov (United States)

Tartakovsky, G.; Neuman, S. P.

2005-12-01

A new analytical solution is presented for the delayed response process characterizing flow to a partially penetrating well in an unconfined aquifer. The new solution generalizes that of Neuman [1972, 1974] by accounting for unsaturated flow above the water table. Axially symmetric three-dimensional flow in the unsaturated zone is described by a linearized version of Richards' equation in which hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value (defining the interface between the saturated and unsaturated zones). Unsaturated soil properties are characterized by an exponent κ having the dimension of inverse length and a dimensionless exponent κD = κb where b is initial saturated thickness. Our treatment of the unsaturated zone is similar to that of Kroszynski and Dagan [1975] who however have ignored internal (artesian) aquifer storage. It has been suggested by Boulton [1954, 1963, 1970] and Neuman [1972, 1974], and is confirmed by our solution, that internal storage is required to reproduce the early increase in drawdown characterizing delayed response to pumping in typical aquifers. According to our new solution such aquifers are characterized by relatively large κ_ D values, typically 10 or larger; in the limit as κD tends to infinity (the soil unsaturated water retention capacity becomes insignificant and/or aquifer thickness become large), unsaturated flow becomes unimportant and our solution reduces to that of Neuman. In typical cases corresponding to κD larger than or equal to 10, unsaturated flow is found to have little impact on early and late dimensionless time behaviors of drawdown measured wholly or in part at some distance below the water table; unsaturated flow causes drawdown to increase slightly at intermediate dimensionless time values that represent transition from an early artesian dominated to a late water-table dominated flow regime. The increase in drawdown

Stochastic analysis of radionuclide migration in saturated-unsaturated soils

International Nuclear Information System (INIS)

Kawanishi, Moto

1988-01-01

In Japan, LLRW (low level radioactive wastes) generated from nuclear power plants shall be started to store concentrically in the Shimokita site from 1990, and those could be transformed into land disposal if the positive safety is confirmed. Therefore, it is hoped that the safety assessment method shall be successed for the land disposal of LLRW. In this study, a stochastic model to analyze the radionuclide migration in saturated-unsaturated soils was constructed. The principal results are summarized as follows. 1) We presented a generalized idea for the modeling of the radionuclide migration in saturated-unsaturated soils as an advective-dispersion phenomena followed by the decay of radionuclides and those adsorption/desorption in soils. 2) Based on the radionuclide migration model mentioned above, we developed a stochastic analysis model on radionuclide migration in saturated-unsaturated soils. 3) From the comparison between the simulated results and the exact solution on a few simple one-dimensional advective-dispersion problems of radionuclides, the good validity of this model was confirmed. 4) From the comparison between the simulated results by this model and the experimental results of radionuclide migration in a one-dimensional unsaturated soil column with rainfall, the good applicability was shown. 5) As the stochastic model such as this has several advantages that it is easily able to represent the image of physical phenomena and has basically no numerical dissipation, this model should be more applicable to the analysis of the complicated radionuclide migration in saturated-unsaturated soils. (author)

Simulation of unsaturated flow and solute transport at the Las Cruces trench site using the PORFLO-3 computer code

International Nuclear Information System (INIS)

Rockhold, M.L.; Wurstner, S.K.

1991-03-01

The objective of this work was to test the ability of the PORFLO-3 computer code to simulate water infiltration and solute transport in dry soils. Data from a field-scale unsaturated zone flow and transport experiment, conducted near Las Cruces, New Mexico, were used for model validation. A spatial moment analysis was used to provide a quantitative basis for comparing the mean simulated and observed flow behavior. The scope of this work was limited to two-dimensional simulations of the second experiment at the Las Cruces trench site. Three simulation cases are presented. The first case represents a uniform soil profile, with homogeneous, isotropic hydraulic and transport properties. The second and third cases represent single stochastic realizations of randomly heterogeneous hydraulic conductivity fields, generated from the cumulative probability distribution of the measured data. Two-dimensional simulations produced water content changes that matched the observed data reasonably well. Models that explicitly incorporated heterogeneous hydraulic conductivity fields reproduced the characteristics of the observed data somewhat better than a uniform, homogeneous model. Improved predictions of water content changes at specific spatial locations were obtained by adjusting the soil hydraulic properties. The results of this study should only be considered a qualitative validation of the PORFLO-3 code. However, the results of this study demonstrate the importance of site-specific data for model calibration. Applications of the code for waste management and remediation activities will require site-specific data for model calibration before defensible predictions of unsaturated flow and containment transport can be made. 23 refs., 16 figs., 3 tabs

On the Longitudinal Dispersion in Conservative Transport Through Heterogeneous Porous Formations at Finite Peclet Numbers

Science.gov (United States)

Severino, Gerardo; Cuomo, Salvatore; Sommella, Angelo; D'urso, Guido

2017-10-01

We consider transport of a conservative solute through an aquifer as determined: (i) by the advective velocity, which depends upon the hydraulic conductivity K and (ii) by the local spreading due to the pore-scale dispersion (PSD). The flow is steady, and it takes place in a porous formation where, owing to its erratic spatial variations, the hydraulic log conductivity Y≡ln⁡K is modeled as a stationary Gaussian random field. The relative effect of the above mechanisms (i)-(ii) is quantified by the Peclet number>(Pe>) which, in most of the previous studies, was considered infinite (i.e., no PSD) due to the overtake of advective heterogeneities upon the PSD. Here we aim at generalizing such studies by accounting for the impact of finite Pe on conservative transport. Previous studies on the topic required extensive numerical computations. In the present note, we remove the computational burden by adopting the rational approximate expression of Dagan and Cvetkovic (1993) for the covariance of the velocity field. This allows one to obtain closed form expressions for the quantities characterizing the longitudinal plume's dispersion. Transport can be straightforwardly investigated by dealing with a modified Peclet number>(Pe>¯>) incorporating both the PSD and the aquifer's anisotropy. The satisfactory match to Cape Cod field data suggests that the present theoretical results lend themselves as a useful tool to assess the impact of the PSD upon conservative transport through heterogeneous porous formations.

Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei

Directory of Open Access Journals (Sweden)

D. Barahona

2009-01-01

Full Text Available We present a parameterization of cirrus cloud formation that computes the ice crystal number and size distribution under the presence of homogeneous and heterogeneous freezing. The parameterization is very simple to apply and is derived from the analytical solution of the cloud parcel equations, assuming that the ice nuclei population is monodisperse and chemically homogeneous. In addition to the ice distribution, an analytical expression is provided for the limiting ice nuclei number concentration that suppresses ice formation from homogeneous freezing. The parameterization is evaluated against a detailed numerical parcel model, and reproduces numerical simulations over a wide range of conditions with an average error of 6±33%. The parameterization also compares favorably against other formulations that require some form of numerical integration.

Unsaturated Fatty Acid Esters Metathesis Catalyzed by Silica Supported WMe5

KAUST Repository

Riache, Nassima; Callens, Emmanuel; Talbi, Karima; Basset, Jean-Marie

2015-01-01

Metathesis of unsaturated fatty acid esters (FAEs) by silica supported multifunctional W-based catalyst is disclosed. This transformation represents a novel route towards unsaturated di-esters. Especially, the self-metathesis of ethyl undecylenate

Heterogeneous formation of HONO on carbonaceous aerosol

Energy Technology Data Exchange (ETDEWEB)

Ammann, M.; Kalberer, M.; Tabor, K. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)] [and others

1997-09-01

Based on an on-line and in situ experimental approach, for the first time heterogeneous production of nitrous acid (HONO) on carbon aerosol at ambient pressure and low NO{sub 2} concentration has been quantified by use of a {sup 13}N tracer technique. (author) 1 fig., 4 refs.

Unsaturated zone investigation at the radioactive waste storage facility site

Energy Technology Data Exchange (ETDEWEB)

Skuratovic, Zana; Mazeika, Jonas; Petrosius, Rimantas; Jakimaviciute-Maseliene, Vaidote [Nature Research Centre, Akademijos St. 2, LT-08412, Vilnius (Lithuania); Klizas, Petras; Mokrik, Robert [Vilnius University, M.K. Ciurlionio St. 21/27, LT-03101 Vilnius (Lithuania)

2014-07-01

Unsaturated zone is an important part of water circulation cycle and an integral part of many hydrological and hydrogeological factors and processes. The soils of unsaturated zone are regarded as the first natural barrier to a large extent able to limit the spread of contaminants. Nuclear waste disposal site (Maisiagala radioactive waste storage facility site) was analysed in terms of the moisture movement through the unsaturated zone. Extensive data sets of the hydraulic properties, water content and isotope composition have been collected and summarized. The main experimental and observational tasks included the collection of soil samples; determination of the physical properties and the hydraulic conductivity values of soil samples, moisture extraction from the soil sample for isotopic studies; observation of the groundwater dynamics at the Maisiagala piezometer; groundwater sampling for isotopic analysis ({sup 3}H, {sup 18}O/{sup 16}O, {sup 2}H/{sup 1}H ); and monthly precipitation isotopic analysis. Distribution features of globally widespread radionuclide tritium ({sup 3}H) and the water molecule tracer isotopes in precipitation, unsaturated zone soil moisture profiles and groundwater were determined. It was used the well-known unsaturated flow and transport model of HYDRUS-1D (Simunek et al., 2008). In this study, van Genuchten equations for the retention and conductivity estimations have been used. The retention characteristics and van Genuchten model parameters were estimated internally by HYDRUS based on the empirical equations involved in the program. Basic inputs of the tritium transport simulation are the tritium input function and meteorological variables (precipitation and potential evapotranspiration). In order to validate the representativeness of the hydraulic parameters, the model has been used to estimate the tritium distribution in the unsaturated zone, which properly represents the dynamics of the unsaturated zone. The uniformity of the daily

An XML-based Schema-less Approach to Managing Diagnostic Data in Heterogeneous Formats

Energy Technology Data Exchange (ETDEWEB)

Naito, O. [Japan Atomic Energy Agency, Ibaraki (Japan)

2009-07-01

Managing diagnostic data in heterogeneous formats is always a nuisance, especially when a new diagnostic technique requires a new data structure that does not fit in the existing data format. Ideally, it is best to have an all-purpose schema that can specify any data structures. But devising such a schema is a difficult task and the resultant data management system tends to be large and complicated. As a complementary approach, we can think of a system that has no specific schema but requires each of the data to describe itself without assuming any prior information. In this paper, a very primitive implementation of such a system based on extensible Markup Language (XML) is examined. The actual implementation is no more than an addition of a tiny XML meta-data file that describes the detailed format of the associated diagnostic data file. There are many ways to write and read such meta-data files. For example, if the data are in a standard format that is foreign to the existing system, just specify the name of the format and what interface to use for reading the data. If the data are in a non-standard arbitrary format, write what is written and how into the meta-data file at every occurrence of data output. And as a last resort, if the format of the data is too complicated, a code to read the data can be stored in the meta-data file. Of course, this schema-less approach has some drawbacks, two of which are the doubling of the number of files to be managed and the low performance of data handling, though the former can be a merit, when it is necessary to update the meta-data leaving the body data intact. The important point is that the necessary information to read the data is decoupled from data itself. The merits and demerits of this approach are discussed. This document is composed of an abstract followed by the presentation slides. (author)

Isotope Investigations of Groundwater Movement in a Coarse Gravel Unsaturated Zone

Energy Technology Data Exchange (ETDEWEB)

Mali, N. [Geological Survey of Slovenia, Department of Hydrogeology, Ljubljana (Slovenia); Kozar-Logar, J. [Jozef Stefan Institute, Ljubljana (Slovenia); Leis, A. [Institute of Water Resources Management, Hydrogeology and Geophysics, Joanneum Research Forschungsgesellschaft mbH, Graz (Austria)

2013-07-15

The unsaturated zone above an aquifer serves as a water reservoir which discharges water and possible pollution to the saturated zone. This paper presents the application of oxygen-18 and tritium isotope methods in the study of groundwater transport processes in the unsaturated zone of Selniska Dobrava coarse gravel aquifer. The Selniska Dobrava gravel aquifer is an important water resource for Maribor and its surroundings, therefore the determination of transport processes in the unsaturated zone is important regarding its protection. Groundwater flow characteristics were estimated using isotopes and based on experimental work in a lysimeter. Tritium investigation results were compared with the results of long term oxygen-18 isotope investigation. In this paper the analytical approach, results and interpretation of {delta}{sup 18}O and tritium measurements in the unsaturated zone are presented. (author)

Transport of citrate-coated silver nanoparticles in unsaturated sand

Science.gov (United States)

Kumahor, Samuel; Hron, Pavel; Metreveli, George; Schaumann, Gabriele; Vogel, Hans-Jörg

2015-04-01

Chemical factors and physical constraints lead to coupled effects during particle transport in unsaturated porous media. Unlike for saturated transport, studies on unsaturated transport as typical for soil are currently scarce. We investigated the mobility of citrate-coated Ag NPs in unsaturated sand (grain diameter: 0.1-0.3 mm). For three flux rates and a given pore-water ionic strength (1 mM KNO3), the citrate-coated Ag NPs were less mobile at pH = 5 compared to pH = 9. The classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory suggests unfavorable deposition conditions at both, the air-water interface and solid-water interface. Breakthrough curves measured under quasi-steady state unsaturated flow showed retardation of the citrate-coated Ag NPs compared to inert solute (KBr). After flushing with nanoparticle-free 1 mM KNO3 solution (pH-adjusted), retention was much lower in deeper depths compared to the surface where the particles entered the flow field. The results show a non-linear dependence of nanoparticle (NP) mobility on flux rate and water content. Especially the observed retardation similar to equilibrium sorption is in contrast to observations under saturated flow conditions. A convection-dispersion and reaction model that combines a reversible equilibrium process and a non-equilibrium interaction process reproduced the measured breakthrough curves reasonably well. From comparison between saturated and unsaturated experiments we conclude that the air-water interface is responsible for the reversible equilibrium process while the water-solid interface accounts for irreversible soption.

Completion evaluation of the Eagle Ford formation with heterogeneous proppant placement

Energy Technology Data Exchange (ETDEWEB)

Viswanathan, A.; Altman, R.; Oussoltsev, D.; Kanneganti, K.; Xu, J.; Grant, D.; Indriati, S.; Pena, A.; Loayza, M.; Kirkham, B.; Rhein, T. [Society of Petroleum Engineers (Canada)

2011-07-01

With the major developments of the Eagle Ford shale in Texas, there has been an increasing focus on the optimization of stimulation techniques. Many techniques have already been implemented in order to improve productivity across Eagle Ford. This paper analyzes completion techniques currently in place through the Hawkville field with the goal of determining key parameters and their impact on the well. The paper focuses mainly on channel fracturing based on a heterogeneous proppant placement technique and evaluates it against current slickwater and hybrid stimulation treatments. The evaluation described in the paper was conducted by first collecting data from 51 horizontal wells in the Eagle Ford formation. It then follows through the evaluation completing a normalized production comparison, a productivity index analysis, neural network trained self-organizing maps, and numerical simulations. Through evaluations and comparisons the paper shows that channel fracturing can allow for a significant improvement in production of dry gas wells.

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

Science.gov (United States)

Chung Kwong, Kai; Chim, Man Mei; Davies, James F.; Wilson, Kevin R.; Nin Chan, Man

2018-02-01

Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH) of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time, DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4-) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O) and a sulfate radical anion (SO4 ṡ -) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10-13 cm3 molecule-1 s-1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 1012 molecule cm-3 s), only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an

A mathematical model in charactering chloride diffusivity in unsaturated cementitious material

NARCIS (Netherlands)

Zhang, Y.; Ye, G.; Pecur, I.B.; Baricevic, A.; Stirmer, N; Bjegovic, D.

2017-01-01

In this paper, a new analytic model for predicting chloride diffusivity in unsaturated cementitious materials is developed based on conductivity theory and Nernst-Einstein equation. The model specifies that chloride diffusivity in unsaturated cementitious materials can be mathematically described as

Longitudinal dispersion coefficients for numerical modeling of groundwater solute transport in heterogeneous formations.

Science.gov (United States)

Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K

2017-09-15

Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion

Gold nanoparticles on OMS-2 for heterogeneously catalyzed aerobic oxidative α,β-dehydrogenation of β-heteroatom-substituted ketones.

Science.gov (United States)

Yoshii, Daichi; Jin, Xiongjie; Yatabe, Takafumi; Hasegawa, Jun-Ya; Yamaguchi, Kazuya; Mizuno, Noritaka

2016-12-06

In the presence of Au nanoparticles supported on manganese oxide OMS-2 (Au/OMS-2), various kinds of β-heteroatom-substituted α,β-unsaturated ketones (heteroatom = N, O, S) can be synthesized through α,β-dehydrogenation of the corresponding saturated ketones using O 2 (in air) as the oxidant. The catalysis of Au/OMS-2 is truly heterogeneous, and the catalyst can be reused.

Unsaturated and Saturated Permeabilities of Fiber Reinforcement: Critics and Suggestions

Directory of Open Access Journals (Sweden)

Chung Hae ePARK

2015-04-01

Full Text Available In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.

Reactive distillation: an attractive alternative for the synthesis of unsaturated polyester

NARCIS (Netherlands)

Shah, M.R.; Zondervan, E.; Oudshoorn, M.L.; Haan, de A.B.

2011-01-01

Unsaturated polyester is traditionally produced in a batch wise operating reaction vessel connected to a distillation unit. An attractive alternative for the synthesis of unsaturated polyester is a reactive distillation. To value such alternative synthesis route reliable process models need to be

Sensitivity Analysis of Unsaturated Flow and Contaminant Transport with Correlated Parameters

Science.gov (United States)

Relative contributions from uncertainties in input parameters to the predictive uncertainties in unsaturated flow and contaminant transport are investigated in this study. The objectives are to: (1) examine the effects of input parameter correlations on the sensitivity of unsaturated flow and conta...

Leaching patterns and secondary phase formation during unsaturated leaching of UO2 at 90 degrees C

International Nuclear Information System (INIS)

Wronkiewicz, D.J.; Bates, J.K.; Gerding, T.J.; Veleckis, E.; Tani, B.S.

1991-11-01

Experiments are being conducted that examine the reaction of UO 2 with dripping oxygenated ground water at 90 degrees C. The experiments are designed to identify secondary phases formed during UO 2 alteration, evaluate parameters controlling U release, and act as scoping tests for studies with spent fuel. This study is the first of its kind that examines the alteration of UO 2 under unsaturated conditions expected to exist at the proposed Yucca Mountain repository site. Results suggest the UO 2 matrix will readily react within a few months after being exposed to simulated Yucca Mountain conditions. A pulse of rapid U release, combined with the formation of dehydrated schoepite on the UO 2 surface, characterizes the reaction between one to two years. Rapid dissolution of intergrain boundaries and spallation of UO 2 granules appears to be responsible for much of the U released. Differential release of the UO 2 granules may be responsible for much of the variation observed between duplicate experiments. Less than 5 wt % of the released U remains in solution or in a suspended form, while the remaining settles out of solution as fine particles or is reprecipitated as secondary phases. Subsequent to the pulse period, U release rates decline and a more stable assemblage of uranyl silicate phases are formed by incorporating cations from the ground water leachant. Uranophane, boltwoodite, and sklodowskite appear as the final solubility limiting phases that form in these tests. This observed paragenetic sequence (from uraninite to schoepite-type phases to uranyl silicates) is identical to those observed in weathered zones of natural uraninite occurrences. The combined results indicate that the release of radionuclides from spent fuel may not be limited by U solubility constraints, but that spallation of particulate matter may be an important, if not the dominant release mechanism affecting release

Determination of Transport Properties From Flowing Fluid Temperature Logging In Unsaturated Fractured Rocks: Theory And Semi-Analytical Solution

International Nuclear Information System (INIS)

Mukhopadhyay, Sumit; Tsang, Yvonne W.

2008-01-01

Flowing fluid temperature logging (FFTL) has been recently proposed as a method to locate flowing fractures. We argue that FFTL, backed up by data from high-precision distributed temperature sensors, can be a useful tool in locating flowing fractures and in estimating the transport properties of unsaturated fractured rocks. We have developed the theoretical background needed to analyze data from FFTL. In this paper, we present a simplified conceptualization of FFTL in unsaturated fractured rock, and develop a semianalytical solution for spatial and temporal variations of pressure and temperature inside a borehole in response to an applied perturbation (pumping of air from the borehole). We compare the semi-analytical solution with predictions from the TOUGH2 numerical simulator. Based on the semi-analytical solution, we propose a method to estimate the permeability of the fracture continuum surrounding the borehole. Using this proposed method, we estimated the effective fracture continuum permeability of the unsaturated rock hosting the Drift Scale Test (DST) at Yucca Mountain, Nevada. Our estimate compares well with previous independent estimates for fracture permeability of the DST host rock. The conceptual model of FFTL presented in this paper is based on the assumptions of single-phase flow, convection-only heat transfer, and negligible change in system state of the rock formation. In a sequel paper (Mukhopadhyay et al., 2008), we extend the conceptual model to evaluate some of these assumptions. We also perform inverse modeling of FFTL data to estimate, in addition to permeability, other transport parameters (such as porosity and thermal conductivity) of unsaturated fractured rocks

A green synthesis of α,β-unsaturated carbonyl compounds from glyceraldehyde acetonide

Directory of Open Access Journals (Sweden)

Cláudia O. Veloso

2011-01-01

Full Text Available The catalytic behavior of Cs-exchanged and Cs-impregnated zeolites (X and Y was studied using the Knoevenagel condensation between glyceraldehyde acetonide and ethyl acetoacetate in order to produce the corresponding α,β-unsaturated carbonyl compound that is an important intermediate for fine chemicals. The influence of reaction temperature, type of zeolite, and basicity of the sites on the catalytic behavior of the samples was evaluated. All zeolites were active for the studied reaction. The formation of the main condensation product was favored at lower reaction temperatures. Products of further condensations were also observed especially for samples that were only dried before catalytic test.

Effects of Chain Length and Degree of Unsaturation of Fatty Acids on Structure and in Vitro Digestibility of Starch-Protein-Fatty Acid Complexes.

Science.gov (United States)

Zheng, Mengge; Chao, Chen; Yu, Jinglin; Copeland, Les; Wang, Shuo; Wang, Shujun

2018-02-28

The effects of chain length and degree of unsaturation of fatty acids (FAs) on structure and in vitro digestibility of starch-protein-FA complexes were investigated in model systems. Studies with the rapid visco analyzer (RVA) showed that the formation of ternary complex resulted in higher viscosities than those of binary complex during the cooling and holding stages. The results of differential scanning calorimetry (DSC), Raman, and X-ray diffraction (XRD) showed that the structural differences for ternary complexes were much less than those for binary complexes. Starch-protein-FA complexes presented lower in vitro enzymatic digestibility compared with starch-FAs complexes. We conclude that shorter chain and lower unsaturation FAs favor the formation of ternary complexes but decrease the thermal stability of these complexes. FAs had a smaller effect on the ordered structures of ternary complexes than on those of binary complexes and little effect on enzymatic digestibility of both binary and ternary complexes.

Oxygenated gasoline release in the unsaturated zone - Part 1: Source zone behavior.

Science.gov (United States)

Freitas, Juliana G; Barker, James F

2011-11-01

Oxygenates present in gasoline, such as ethanol and MTBE, are a concern in subsurface contamination related to accidental spills. While gasoline hydrocarbon compounds have low solubility, MTBE and ethanol are more soluble, ethanol being completely miscible with water. Consequently, their fate in the subsurface is likely to differ from that of gasoline. To evaluate the fate of gasoline containing oxygenates following a release in the unsaturated zone shielded from rainfall/recharge, a controlled field test was performed at Canadian Forces Base Borden, in Ontario. 200L of a mixture composed of gasoline with 10% ethanol and 4.5% MTBE was released in the unsaturated zone, into a trench 20cm deep, about 32cm above the water table. Based on soil cores, most of the ethanol was retained in the source, above the capillary fringe, and remained there for more than 100 days. Ethanol partitioned from the gasoline to the unsaturated pore-water and was retained, despite the thin unsaturated zone at the site (~35cm from the top of the capillary fringe to ground surface). Due to its lower solubility, most of the MTBE remained within the NAPL as it infiltrated deeper into the unsaturated zone and accumulated with the gasoline on top of the depressed capillary fringe. Only minor changes in the distribution of ethanol were noted following oscillations in the water table. Two methods to estimate the capacity of the unsaturated zone to retain ethanol are explored. It is clear that conceptual models for sites impacted by ethanol-fuels must consider the unsaturated zone. Copyright © 2011 Elsevier B.V. All rights reserved.

Saturated versus unsaturated hydrocarbon interactions with carbon nanostructures

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Deivasigamani eUmadevi

2014-09-01

Full Text Available The interactions of various acyclic and cyclic hydrocarbons in both saturated and unsaturated forms with the carbon nanostructures (CNSs have been explored by using density functional theory (DFT calculations. Model systems representing armchair and zigzag carbon nanotubes (CNTs and graphene have been considered to investigate the effect of chirality and curvature of the CNSs towards these interactions. Results of this study reveal contrasting binding nature of the acyclic and cyclic hydrocarbons towards CNSs. While the saturated molecules show stronger binding affinity in acyclic hydrocarbons; the unsaturated molecules exhibit higher binding affinity in cyclic hydrocarbons. In addition, acyclic hydrocarbons exhibit stronger binding affinity towards the CNSs when compared to their corresponding cyclic counterparts. The computed results excellently corroborate the experimental observations. The interaction of hydrocarbons with graphene is more favourable when compared with CNTs. Bader’s theory of atoms in molecules has been invoked to characterize the noncovalent interactions of saturated and unsaturated hydrocarbons. Our results are expected to provide useful insights towards the development of rational strategies for designing complexes with desired noncovalent interaction involving CNSs.

Investigations of the unsaturated zone at two radioactive waste disposal sites in Lithuania.

Science.gov (United States)

Skuratovič, Žana; Mažeika, Jonas; Petrošius, Rimantas; Martma, Tõnu

2016-01-01

The unsaturated zone is an important part of the water cycle, governed by many hydrological and hydrogeological factors and processes and provide water and nutrients to the terrestrial ecosystem. Besides, the soils of the unsaturated zone are regarded as the first natural barrier to a large extent and are able to limit the spread of contaminants depending on their properties. The unsaturated zone provides a linkage between atmospheric moisture, groundwater, and seepage of groundwater to streams, lakes, or other surface water bodies. The major difference between water flow in saturated and unsaturated soils is that the hydraulic conductivity, which is conventionally assumed to be a constant in saturated soils, is a function of the degree of saturation or matrix suction in the unsaturated soils. In Lithuania, low and intermediate level radioactive wastes generated from medicine, industry and research were accumulated at the Maisiagala radioactive waste repository. Short-lived low and intermediate levels radioactive waste, generated during the operation of the Ignalina Nuclear Power Plant (INPP) and arising after the INPP decommissioning will be disposed of in the near surface repository close to the INPP (Stabatiske site). Extensive data sets of the hydraulic properties and water content attributed to unsaturated zone soil profiles of the two radioactive waste disposal sites have been collected and summarized. Globally widespread radionuclide tritium ((3)H) and stable isotope ratio ((18)O/(16)O and (2)H/(1)H) distribution features were determined in precipitation, unsaturated zone soil moisture profiles and groundwater.

Unsaturated soil moisture drying and wetting diffusion coefficient measurements in the laboratory.

Science.gov (United States)

2009-09-01

ABSTRACTTransient moisture flow in an unsaturated soil in response to suction changes is controlled by the unsaturated moisture diffusion coefficient. The moisture diffusion coefficient can be determined by measuring suction profiles over time. The l...

Second European Conference on Unsaturated Soils, E-UNSAT 2012

CERN Document Server

Jommi, Cristina; D’Onza, Francesca; Unsaturated Soils: Research and Applications

2012-01-01

These volumes contain the contributions to the Second European Conference on Unsaturated Soils, E-UNSAT 2012, held in Napoli, Italy, in June 2012. The event is the second of a series of European conferences, and follows the first successful one, organised in Durham, UK, in 2008. The conference series is supported by Technical Committee 106 of the International Society of Soil Mechanics and Geotechnical Engineering on Unsaturated Soils. The published contributions were selected after a careful peer-review process. A collection of more than one hundred papers is included, addressing the three thematic areas experimental, including advances in testing techniques and soil behaviour, modelling, covering theoretical and constitutive issues together with numerical and physical modelling, and engineering, focusing on approaches, case histories and geo-environmental themes. The areas of application of the papers embrace most of the geotechnical problems related to unsaturated soils. Increasing interest in geo-environm...

Saturated-unsaturated flow in a compressible leaky-unconfined aquifer

Science.gov (United States)

Mishra, Phoolendra K.; Vesselinov, Velimir V.; Kuhlman, Kristopher L.

2012-06-01

An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

Transport of citrate-coated silver nanoparticles in unsaturated sand

Energy Technology Data Exchange (ETDEWEB)

Kumahor, Samuel K., E-mail: samuel.kumahor@ufz.de [Department of Soil Physics, Helmholtz Centre for Environmental Research–UFZ, Theodor-Lieser-Strasse 4, 06120 Halle-Saale (Germany); Hron, Pavel, E-mail: pavel.hron@iwr.uni-heidelberg.de [Interdisciplinary Center for Scientific Computing, University of Heidelberg, Im Neuenheimer Feld 368, Raum 422, 69120 Heidelberg (Germany); Metreveli, George, E-mail: metreveli@uni-landau.de [Universität Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstr. 7, D-76829 Landau (Germany); Schaumann, Gabriele E., E-mail: schaumann@uni-landau.de [Universität Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstr. 7, D-76829 Landau (Germany); Vogel, Hans-Jörg, E-mail: hans-joerg.vogel@ufz.de [Department of Soil Physics, Helmholtz Centre for Environmental Research–UFZ, Theodor-Lieser-Strasse 4, 06120 Halle-Saale (Germany); Institute of Soil Science and Plant Nutrition, Martin-Luther-University Halle-Wittenberg, Von-Seckendorff-Platz 3, 06120 Halle-Saale (Germany)

2015-12-01

Chemical factors and physical constraints lead to coupled effects during particle transport in unsaturated porous media. Studies on unsaturated transport as typical for soils are currently scarce. In unsaturated porous media, particle mobility is determined by the existence of an air–water interface in addition to a solid–water interface. To this end, we measured breakthrough curves and retention profiles of citrate-coated Ag nanoparticles in unsaturated sand at two pH values (5 and 9) and three different flow rates corresponding to different water contents with 1 mM KNO{sub 3} as background electrolyte. The classical DLVO theory suggests unfavorable deposition conditions at the air–water and solid–water interfaces. The breakthrough curves indicate modification in curve shapes and retardation of nanoparticles compared to inert solute. Retention profiles show sensitivity to flow rate and pH and this ranged from almost no retention for the highest flow rate at pH = 9 to almost complete retention for the lowest flow rate at pH = 5. Modeling of the breakthrough curves, thus, required coupling two parallel processes: a kinetically controlled attachment process far from equilibrium, responsible for the shape modification, and an equilibrium sorption, responsible for particle retardation. The non-equilibrium process and equilibrium sorption are suggested to relate to the solid–water and air–water interfaces, respectively. This is supported by the DLVO model extended for hydrophobic interactions which suggests reversible attachment, characterized by a secondary minimum (depth 3–5 kT) and a repulsive barrier at the air–water interface. In contrast, the solid–water interface is characterized by a significant repulsive barrier and the absence of a secondary minimum suggesting kinetically controlled and non-equilibrium interaction. This study provides new insights into particle transport in unsaturated porous media and offers a model concept representing the

Modeling tritium transport through a deep unsaturated zone in an arid environment

Science.gov (United States)

Mayers, C.J.; Andraski, Brian J.; Cooper, C.A.; Wheatcraft, S.W.; Stonestrom, David A.; Michel, R.L.

2005-01-01

Understanding transport of tritium (3H) in unsaturated zones is critical to evaluating options for waste isolation. Tritium typically is a large component of low-level radioactive waste (LLRW). Studies at the U.S. Geological Survey's Amargosa Desert Research Site (ADRS) in Nevada investigate 3H transport from a closed LLRW facility. Two boreholes are 100 and 160 m from the nearest waste trench and extend to the water table at 110 m. Soil-water vapor samples from the deep boreholes show elevated levels of 3H at all depths. The objectives of this study were to (i) test source thermal and gas-advection mechanisms driving 3H transport and (ii) evaluate model sensitivity to these mechanisms and to selected physical and hydraulic properties including porosity, tortuosity, and anisotropy. A two-dimensional numerical model incorporated a non-isothermal, heterogeneous domain of the unsaturated zone and instantaneous isotopic equilibrium. The TOUGH2 code was used; however, it required modification to account for temperature dependence of both the Henry's law equilibrium constant and isotopic fractionation with respect to tritiated water. Increases in source temperature, pressure, and porosity enhanced 3H migration, but failed to match measured 3H distributions. All anisotropic simulations with a source pressure component resembled, in shape, the upper portion of the 3H distribution of the nearest borehole. Isotopic equilibrium limited migration of 3H, while effects of radioactive decay were negligible. A 500 Pa pressure increase above ambient pressure in conjunction with a high degree of anisotropy (1:100) was necessary for simulated 3H transport to reach the nearest borehole.

Uncertainty analyses of unsaturated zone travel time at Yucca Mountain

International Nuclear Information System (INIS)

Nichols, W.E.; Freshley, M.D.

1993-01-01

Uncertainty analysis method can be applied to numerical models of ground-water flow to estimate the relative importance of physical and hydrologic input variables with respect to ground-water travel time. Monte Carlo numerical simulations of unsaturated flow in the Calico Hills nonwelded zeolitic (CHnz) layer at Yucca Mountain, Nevada, indicate that variability in recharge, and to a lesser extent in matrix porosity, explains most of the variability in predictions of water travel time through the unsaturated zone. Variations in saturated hydraulic conductivity and unsaturated curve-fitting parameters were not statistically significant in explaining variability in water travel time through the unsaturated CHnz unit. The results of this study suggest that the large uncertainty associated with recharge rate estimates for the Yucca Mountain site is of concern because the performance of the potential repository would be more sensitive to uncertainty in recharge than to any other parameter evaluated. These results are not exhaustive because of the limited site characterization data available and because of the preliminary nature of this study, which is limited to a single stratigraphic unit, one dimension, and does not account for fracture flow or other potential fast pathways at Yucca Mountain

Electrokinetic remediation of anionic contaminants from unsaturated soils

International Nuclear Information System (INIS)

Lindgren, E.R.; Kozak, M.W.; Mattson, E.D.

1992-01-01

Heavy-metal contamination of soil and groundwater is a widespread problem in the DOE weapons complex, and for the nation as a whole. Electrokinetic remediation is one possible technique for in situ removal of such contaminants from unsaturated soils. In previous studies at Sandia National Laboratories, the electromigration of chromate ions and anionic dye ions have been demonstrated. This paper reports on a series of experiments that were conducted to study the effect of moisture content on the electromigration rate of anionic contaminants in unsaturated soil and determine the limiting moisture content for which electromigration occurs

Unsaturated Fatty Acid Esters Metathesis Catalyzed by Silica Supported WMe5

KAUST Repository

Riache, Nassima

2015-11-14

Metathesis of unsaturated fatty acid esters (FAEs) by silica supported multifunctional W-based catalyst is disclosed. This transformation represents a novel route towards unsaturated di-esters. Especially, the self-metathesis of ethyl undecylenate results almost exclusively on the homo-coupling product whereas with such catalyst, 1-decene gives ISOMET (isomerization and metathesis olefin) products. The olefin metathesis in the presence of esters is very selective without any secondary cross-metathesis products demonstrating that a high selective olefin metathesis could operate at 150 °C. Additionally, a cross-metathesis of unsaturated FAEs and α-olefins allowed the synthesis of the corresponding ester with longer hydrocarbon skeleton without isomerisation.

Repository site data report for unsaturated tuff, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Tien, P.L.; Updegraff, C.D.; Siegel, M.D.; Wahi, K.K.; Guzowski, R.V.

1985-11-01

The US Department of Energy is currently considering the thick sequences of unsaturated, fractured tuff at Yucca Mountain, on the southwestern boundary of the Nevada Test Site, as a possible candidate host rock for a nuclear-waste repository. Yucca Mountain is in one of the most arid areas in the United States. The site is within the south-central part of the Great Basin section of the Basin and Range physiographic province and is located near a number of silicic calderas of Tertiary age. Although localized zones of seismic activity are common throughout the province, and faults are present at Yucca Mountain, the site itself is basically aseismic. No data are available on the composition of ground water in the unsaturated zone at Yucca Mountain. It has been suggested that the composition is bounded by the compositions of water from wells USW-H3, UE25p-1, J-13, and snow or rain. There are relatively few data available from Yucca Mountain on the moisture content and saturation, hydraulic conductivity, and characteristic curves of the unsaturated zone. The available literature on thermomechanical properties of tuff does not always distinguish between data from the saturated zone and data from the unsaturated zone. Geochemical, hydrologic, and thermomechanical data available on the unsaturated tuffs of Yucca Mountain are tabulated in this report. Where the data are very sparse, they have been supplemented by data from the saturated zone or from areas other than Yucca Mountain. 316 refs., 58 figs., 37 tabs

Repository site data report for unsaturated tuff, Yucca Mountain, Nevada

Energy Technology Data Exchange (ETDEWEB)

Tien, P.L.; Updegraff, C.D.; Siegel, M.D.; Wahi, K.K.; Guzowski, R.V.

1985-11-01

The US Department of Energy is currently considering the thick sequences of unsaturated, fractured tuff at Yucca Mountain, on the southwestern boundary of the Nevada Test Site, as a possible candidate host rock for a nuclear-waste repository. Yucca Mountain is in one of the most arid areas in the United States. The site is within the south-central part of the Great Basin section of the Basin and Range physiographic province and is located near a number of silicic calderas of Tertiary age. Although localized zones of seismic activity are common throughout the province, and faults are present at Yucca Mountain, the site itself is basically aseismic. No data are available on the composition of ground water in the unsaturated zone at Yucca Mountain. It has been suggested that the composition is bounded by the compositions of water from wells USW-H3, UE25p-1, J-13, and snow or rain. There are relatively few data available from Yucca Mountain on the moisture content and saturation, hydraulic conductivity, and characteristic curves of the unsaturated zone. The available literature on thermomechanical properties of tuff does not always distinguish between data from the saturated zone and data from the unsaturated zone. Geochemical, hydrologic, and thermomechanical data available on the unsaturated tuffs of Yucca Mountain are tabulated in this report. Where the data are very sparse, they have been supplemented by data from the saturated zone or from areas other than Yucca Mountain. 316 refs., 58 figs., 37 tabs.

Numerical Study of Critical Role of Rock Heterogeneity in Hydraulic Fracture Propagation

Energy Technology Data Exchange (ETDEWEB)

J. Zhou; H. Huang; M. Deo

2016-03-01

Log and seismic data indicate that most shale formations have strong heterogeneity. Conventional analytical and semi-analytical fracture models are not enough to simulate the complex fracture propagation in these highly heterogeneous formation. Without considering the intrinsic heterogeneity, predicted morphology of hydraulic fracture may be biased and misleading in optimizing the completion strategy. In this paper, a fully coupling fluid flow and geomechanics hydraulic fracture simulator based on dual-lattice Discrete Element Method (DEM) is used to predict the hydraulic fracture propagation in heterogeneous reservoir. The heterogeneity of rock is simulated by assigning different material force constant and critical strain to different particles and is adjusted by conditioning to the measured data and observed geological features. Based on proposed model, the effects of heterogeneity at different scale on micromechanical behavior and induced macroscopic fractures are examined. From the numerical results, the microcrack will be more inclined to form at the grain weaker interface. The conventional simulator with homogeneous assumption is not applicable for highly heterogeneous shale formation.

Role of Lipid Peroxidation-Derived α, β-Unsaturated Aldehydes in Vascular Dysfunction

Directory of Open Access Journals (Sweden)

Seung Eun Lee

2013-01-01

Full Text Available Vascular diseases are the most prominent cause of death, and inflammation and vascular dysfunction are key initiators of the pathophysiology of vascular disease. Lipid peroxidation products, such as acrolein and other α, β-unsaturated aldehydes, have been implicated as mediators of inflammation and vascular dysfunction. α, β-Unsaturated aldehydes are toxic because of their high reactivity with nucleophiles and their ability to form protein and DNA adducts without prior metabolic activation. This strong reactivity leads to electrophilic stress that disrupts normal cellular function. Furthermore, α, β-unsaturated aldehydes are reported to cause endothelial dysfunction by induction of oxidative stress, redox-sensitive mechanisms, and inflammatory changes such as induction of cyclooxygenase-2 and cytokines. This review provides an overview of the effects of lipid peroxidation products, α, β-unsaturated aldehydes, on inflammation and vascular dysfunction.

Investigating Unsaturated Zone Travel Times with Tritium and Stable Isotopes

Science.gov (United States)

Visser, A.; Thaw, M.; Van der Velde, Y.

2017-12-01

Travel times in the unsaturated zone are notoriously difficult to assess. Travel time tracers relying on the conservative transport of dissolved (noble) gases (tritium-helium, CFCs or SF6) are not applicable. Large water volume requirements of other cosmogenic radioactive isotopes (sulfur-35, sodium-22) preclude application in the unsaturated zone. Prior investigations have relied on models, introduced tracers, profiles of stable isotopes or tritium, or a combination of these techniques. Significant unsaturated zone travel times (UZTT) complicate the interpretation of stream water travel time tracers by ranked StorAge Selection (rSAS) functions. Close examination of rSAS functions in a sloping soil lysimeter[1] show the effect of the UZTT on the shape of the rSAS cumulative distribution function. We studied the UZTT at the Southern Sierra Critical Zone Observatory (SS-CZO) using profiles of tritium and stable isotopes (18O and 2H) in the unsaturated zone, supported by soil water content data. Tritium analyses require 100-500 mL of soil water and therefore large soil samples (1-5L), and elaborate laboratory procedures (oven drying, degassing and noble gas mass spectrometry). The high seasonal and interannual variability in precipitation of the Mediterranean climate, variable snow pack and high annual ET/P ratios lead to a dynamic hydrology in the deep unsaturated soils and regolith and highly variable travel time distributions. Variability of the tritium concentration in precipitation further complicates direct age estimates. Observed tritium profiles (>3 m deep) are interpreted in terms of advective and dispersive vertical transport of the input variability and radioactive decay of tritium. Significant unsaturated zone travel times corroborate previously observed low activities of short-lived cosmogenic radioactive nuclides in stream water. Under these conditions, incorporating the UZTT is critical to adequately reconstruct stream water travel time distributions. 1

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

Directory of Open Access Journals (Sweden)

K. C. Kwong

2018-02-01

Full Text Available Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity (RH of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (direct analysis in real time, DART coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4− has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O and a sulfate radical anion (SO4 ⋅ − upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19  ×  10−13 cm3 molecule−1 s−1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27  ×  1012 molecule cm−3 s, only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

International Nuclear Information System (INIS)

Nakatani, Hisayuki; Kurniawan, Dodik; Taniike, Toshiaki; Terano, Minoru

2008-01-01

In this work, the relationship between the unsaturated chain end group content and the thermal oxidative degradation rate was systematically studied with binary polymer blends of isotactic polypropylene (iPP) with and without the unsaturated chain end group. The iPPs with and without the unsaturated chain end group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blends was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated chain end group. The thermal oxidative degradation rate apparently depends on the content of the unsaturated chain end group. This tendency suggests that the unsaturated chain end acts as a radical initiator of the iPP degradation reaction.

Heterogeneity and Networks

OpenAIRE

Goyal, S.

2018-01-01

This chapter shows that networks can have large and differentiated effects on behavior and then argues that social and economic pressures facilitate the formation of heterogenous networks. Thus networks can play an important role in understanding the wide diversity in human behaviour and in economic outcomes.

Saturated and unsaturated stability analysis of slope subjected to rainfall infiltration

Directory of Open Access Journals (Sweden)

Gofar Nurly

2017-01-01

Full Text Available This paper presents results of saturated and unsaturated stability analysis of typical residual slopes subjected to rainfall infiltration corresponds to 50 years rainfall return period. The slope angles considered were 45° and 70°. The saturated stability analyses were carried out for original and critical ground water level commonly considered by practicing engineer. The analyses were conducted using limit equilibrium method. Unsaturated stability analyses used combination of coupled stress–pore-water pressure analysis to evaluate the effect of rainfall infiltration on the deformation and transient pore-water pressure on slope stability. Slope stability analyses were performed at some times during and after rainfall infiltration. Results show that the critical condition for slope made by sandy material was at the end of rainfall while for clayey material was at some specified times after the rainfall ceased. Unsaturated stability analysis on sandy soil gives higher factor of safety because the soil never reached saturation. Transient analysis using unsaturated soil concept could predict more critical condition of delayed failure of slopes made up of clayey soil.

Multiscale heterogeneity characterization of tidal channel, tidal delta and foreshore facies, Almond Formation outcrops, Rock Springs uplift, Wyoming

Energy Technology Data Exchange (ETDEWEB)

Schatzinger, R.A.; Tomutsa, L. [BDM Petroleum Technologies, Bartlesville, OK (United States)

1997-08-01

In order to accurately predict fluid flow within a reservoir, variability in the rock properties at all scales relevant to the specific depositional environment needs to be taken into account. The present work describes rock variability at scales from hundreds of meters (facies level) to millimeters (laminae) based on outcrop studies of the Almond Formation. Tidal channel, tidal delta and foreshore facies were sampled on the eastern flank of the Rock Springs uplift, southeast of Rock Springs, Wyoming. The Almond Fm. was deposited as part of a mesotidal Upper Cretaceous transgressive systems tract within the greater Green River Basin. Bedding style, lithology, lateral extent of beds of bedsets, bed thickness, amount and distribution of depositional clay matrix, bioturbation and grain sorting provide controls on sandstone properties that may vary more than an order of magnitude within and between depositional facies in outcrops of the Almond Formation. These features can be mapped on the scale of an outcrop. The products of diagenesis such as the relative timing of carbonate cement, scale of cemented zones, continuity of cemented zones, selectively leached framework grains, lateral variability of compaction of sedimentary rock fragments, and the resultant pore structure play an equally important, although less predictable role in determining rock property heterogeneity. A knowledge of the spatial distribution of the products of diagenesis such as calcite cement or compaction is critical to modeling variation even within a single facies in the Almond Fin. because diagenesis can enhance or reduce primary (depositional) rock property heterogeneity. Application of outcrop heterogeneity models to the subsurface is greatly hindered by differences in diagenesis between the two settings. The measurements upon which this study is based were performed both on drilled outcrop plugs and on blocks.

Determination of Polybutadiene Unsaturation Content in Thermal and Thermo-Oxidative Degradation Processes by NMR

Directory of Open Access Journals (Sweden)

Farshid Ziaee

2013-01-01

Full Text Available The unsaturation content of various polybutadiene (PBD types of 1,4-cis, 1,4-trans and 1,2-vinyl isomers with different molecular weights was investigated. An important parameter for unsaturation content of polybutadiene would be the determination of olefnic and aliphatic contents for three types of isomers. For this purpose, proton and carbon nuclear magnetic resonance spectroscopy methods were employed for determination of 1,4-cis, 1,4-trans and 1,2-vinyl contents. A change of adjustable parameter of NMR software was made for accurate integrals giving better results. The accuracy in calculation of low molecular weight PBD, surface area of chain end group decreased in aliphatic region. Furthermore, the changing of unsaturation content versus time was considered for 1,2-PBD and 1,4-PBD in thermal degradation conditions at 250°C. NMR results showed that during heating, the unsaturation content decreased for 1,2-PBD and was not changed for 1,4-PBD. In fact, the basic factor responsible for changing of unsaturation content in thermal degradation of PBD may be due to the presence of 1,2-vinyl isomer. Finally, changing in unsaturation content versus time was observed for 1,2-PBD and 1,4-PBD in thermo-oxidative degradation conditions at 100°C. The NMR results showed that at extended time, the unsaturation content decreased for 1,4-PBD and was not changed for 1,2-PBD. Moreover, the basic factor for changes in unsaturation content in thermo-oxidative degradation of PBD is due to the presence of 1,4-cis and 1,4-trans isomers.

(E)-α,β-unsaturated amides from tertiary amines, olefins and CO via Pd/Cu-catalyzed aerobic oxidative N-dealkylation.

Science.gov (United States)

Shi, Renyi; Zhang, Hua; Lu, Lijun; Gan, Pei; Sha, Yuchen; Zhang, Heng; Liu, Qiang; Beller, Matthias; Lei, Aiwen

2015-02-21

A novel Pd/Cu-catalyzed chemoselective aerobic oxidative N-dealkylation/carbonylation reaction has been developed. Tertiary amines are utilized as a "reservoir" of "active" secondary amines in this transformation, which inhibits the formation of undesired by-products and the deactivation of the catalysts. This protocol allows for an efficient and straightforward construction of synthetically useful and bioactive (E)-α,β-unsaturated amide derivatives from easily available tertiary amines, olefins and CO.

Challenges in the Greener Production of Formates/Formic Acid, Methanol, and DME by Heterogeneously Catalyzed CO2 Hydrogenation Processes

KAUST Repository

Álvarez, Andrea

2017-06-28

The recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO2 capture and green routes to produce H2. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO2 valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions.

Metabolic incorporation of unsaturated fatty acids into boar spermatozoa lipids and de novo formation of diacylglycerols

DEFF Research Database (Denmark)

Svetlichnyy, V.; Müller, P.; Günther-Pomorski, Thomas

2014-01-01

Lipids play an important role in the maturation, viability and function of sperm cells. In this study, we examined the neutral and polar lipid composition of boar spermatozoa by thin-layer chromatography/mass spectrometry. Main representatives of the neutral lipid classes were diacylglycerols...... containing saturated (myristoyl, palmitoyl and stearoyl) fatty acyl residues. Glycerophosphatidylcholine and glycerophosphatidylethanolamine with alk(en)yl ether residues in the sn-1 position and unsaturated long chained fatty acyl residues in sn-2 position were identified as the most prominent polar lipids....... The only glycoglycerolipid was sulfogalactosylglycerolipid carrying 16:0-alkyl- and 16:0-acyl chains. Using stable isotope-labelling, the metabolic incorporation of exogenously supplied fatty acids was analysed. Boar spermatozoa incorporated hexadecenoic (16:1), octadecenoic (18:1), octadecadienoic (18...

A numerical study of water percolation through an unsaturated variable aperture fracture under coupled thermomechanical effects

International Nuclear Information System (INIS)

Tsang, C.F.; Noorishad, J.; Hale, F.V.

1991-12-01

In calculation of ground water travel times associated with performance assessment of a nuclear waste repository, the role of fractures may turn out to be very important. There are two aspects related to fracture flow that have not been fully resolved. The first is the effect of coupled thermomechanical impact on fracture apertures due to the thermal output of the nuclear waste repository. The second is the effect of the variable aperture nature of the fractures. The present paper is an exploratory study of the impact of these two effects on water percolation through unsaturated fractures. The paper is divided into two main sections. the first section describes a calculation of the thermomechanical behavior of the geologic formation around a waste repository. In this exploratory study we assume two major fractures, one vertical and one horizontal through the repository center. Temperatures and thermally induced stress fields are calculated. The second part of the paper considers the unsaturated case and describes a study of water infiltration from the land surface through the vertical fracture to the repository

Compilation of field-scale caisson data on solute transport in the unsaturated zone

International Nuclear Information System (INIS)

Polzer, W.L.; Essington, E.H.; Fuentes, H.R.; Nyhan, J.W.

1986-11-01

Los Alamos National Laboratory has conducted technical support studies to assess siting requirements mandated by Nuclear Regulatory Commission in 10 CFR Part 61. Field-scale transport studies were conducted under unsaturated moisture conditions and under steady and unsteady flow conditions in large caissons located and operated in a natural (field) environment. Moisture content, temperature, flow rate, base-line chemical, tracer influent, and tracer breakthrough data collected during tracer migration studies in the caisson are compiled in tables and graphs. Data suggest that the imposition of a period of drainage (influent solution flow was stopped) may cause an increase in tracer concentration in the soil solution at various sampling points in the caisson. Evaporation during drainage and diffusion of the tracers from immobile to mobile water are two phenomena that could explain the increase. Data also suggest that heterogeneity of sorption sites may increase the variability in transport of sorbing tracers compared with nonsorbing tracers

Modelling the effects of pore-water chemistry on the behaviour of unsaturated clays

Directory of Open Access Journals (Sweden)

Lei Xiaoqin

2016-01-01

Full Text Available Due to their various applications in geo-environmental engineering, such as in landfill and nuclear waste disposals, the coupled chemo-hydro-mechanical analysis of expansive soils has gained more and more attention recently. These expansive soils are usually unsaturated under field conditions; therefore the capillary effects need to be taken into account appropriately. For this purpose, based on a rigorous thermodynamic framework (Lei et al., 2014, the authors have extended the chemo-mechanical model of Loret el al. (2002 for saturated homoionic expansive soils to the unsaturated case (Lei, 2015. In this paper, this chemo-mechanical unsaturated model is adopted to simulate the chemo-elastic-plastic consolidation process of an unsaturated expansive soil layer. Logical tendencies of changes in the chemical, mechanical and hydraulic field quantities are obtained.

Method development and strategy for the characterization of complexly faulted and fractured rhyolitic tuffs, Yucca Mountain, Nevada

Energy Technology Data Exchange (ETDEWEB)

Karasaki, K. [Lawrence Berkeley Lab., CA (United States); Galloway, D. [Geological Survey, Sacramento, CA (United States)

1991-06-01

The planned high-level nuclear waste repository at Yucca Mountain, Nevada, would exist in unsaturated, fractured welded tuff. One possible contaminant pathway to the accessible environment is transport by groundwater infiltrating to the water table and flowing through the saturated zone. Therefore, an effort to characterize the hydrology of the saturated zone is being undertaken in parallel with that of the unsaturated zone. As a part of the saturated zone investigation, there wells-UE-25c{number_sign}1, UE-25c{number_sign}2, and UE-25c{number_sign}3 (hereafter called the c-holes)-were drilled to study hydraulic and transport properties of rock formations underlying the planned waste repository. The location of the c-holes is such that the formations penetrated in the unsaturated zone occur at similar depths and with similar thicknesses as at the planned repository site. In characterizing a highly heterogeneous flow system, several issues emerge. (1) The characterization strategy should allow for the virtual impossibility to enumerate and characterize all heterogeneities. (2) The methodology to characterize the heterogeneous flow system at the scale of the well tests needs to be established. (3) Tools need to be developed for scaling up the information obtained at the well-test scale to the larger scale of the site. In the present paper, the characterization strategy and the methods under development are discussed with the focus on the design and analysis of the field experiments at the c-holes.

Thermal history of the unsaturated zone at Yucca Mountain, Nevada, USA

International Nuclear Information System (INIS)

Whelan, Joseph F.; Neymark, Leonid A.; Moscati, Richard J.; Marshall, Brian D.; Roedder, Edwin

2008-01-01

Secondary calcite, silica and minor amounts of fluorite deposited in fractures and cavities record the chemistry, temperatures, and timing of past fluid movement in the unsaturated zone at Yucca Mountain, Nevada, the proposed site of a high-level radioactive waste repository. The distribution and geochemistry of these deposits are consistent with low-temperature precipitation from meteoric waters that infiltrated at the surface and percolated down through the unsaturated zone. However, the discovery of fluid inclusions in calcite with homogenization temperatures (T h ) up to ∼80 deg. C was construed by some scientists as strong evidence for hydrothermal deposition. This paper reports the results of investigations to test the hypothesis of hydrothermal deposition and to determine the temperature and timing of secondary mineral deposition. Mineral precipitation temperatures in the unsaturated zone are estimated from calcite- and fluorite-hosted fluid inclusions and calcite δ 18 O values, and depositional timing is constrained by the 207 Pb/ 235 U ages of chalcedony or opal in the deposits. Fluid inclusion T h from 50 samples of calcite and four samples of fluorite range from ∼35 to ∼90 deg. C. Calcite δ 18 O values range from ∼0 to ∼22 per mille (SMOW) but most fall between 12 and 20 per mille . The highest T h and the lowest δ 18 O values are found in the older calcite. Calcite T h and δ 18 O values indicate that most calcite precipitated from water with δ 18 O values between -13 and -7 per mille , similar to modern meteoric waters. Twenty-two 207 Pb/ 235 U ages of chalcedony or opal that generally postdate elevated depositional temperatures range from ∼9.5 to 1.9 Ma. New and published 207 Pb/ 235 U and 230 Th/Uages coupled with the T h values and estimates of temperature from calcite δ 18 O values indicate that maximum unsaturated zone temperatures probably predate ∼10 Ma and that the unsaturated zone had cooled to near-present-day temperatures

GDTN: Genome-Based Delay Tolerant Network Formation in Heterogeneous 5G Using Inter-UA Collaboration.

Science.gov (United States)

You, Ilsun; Sharma, Vishal; Atiquzzaman, Mohammed; Choo, Kim-Kwang Raymond

2016-01-01

With a more Internet-savvy and sophisticated user base, there are more demands for interactive applications and services. However, it is a challenge for existing radio access networks (e.g. 3G and 4G) to cope with the increasingly demanding requirements such as higher data rates and wider coverage area. One potential solution is the inter-collaborative deployment of multiple radio devices in a 5G setting designed to meet exacting user demands, and facilitate the high data rate requirements in the underlying networks. These heterogeneous 5G networks can readily resolve the data rate and coverage challenges. Networks established using the hybridization of existing networks have diverse military and civilian applications. However, there are inherent limitations in such networks such as irregular breakdown, node failures, and halts during speed transmissions. In recent years, there have been attempts to integrate heterogeneous 5G networks with existing ad hoc networks to provide a robust solution for delay-tolerant transmissions in the form of packet switched networks. However, continuous connectivity is still required in these networks, in order to efficiently regulate the flow to allow the formation of a robust network. Therefore, in this paper, we present a novel network formation consisting of nodes from different network maneuvered by Unmanned Aircraft (UA). The proposed model utilizes the features of a biological aspect of genomes and forms a delay tolerant network with existing network models. This allows us to provide continuous and robust connectivity. We then demonstrate that the proposed network model has an efficient data delivery, lower overheads and lesser delays with high convergence rate in comparison to existing approaches, based on evaluations in both real-time testbed and simulation environment.

Flame Retardance and Physical Properties of Novel Cured Blends of Unsaturated Polyester and Furan Resins

Directory of Open Access Journals (Sweden)

Baljinder Kaur Kandola

2015-02-01

Full Text Available Novel blends of two furan resins with an unsaturated polyester have been prepared and cured by parallel free radical (for the unsaturated polyester and acid-catalysed crosslinking (for the furan resin to give co-cured composite materials. Although these materials have inferior physical properties, such as low Tg and low storage modulus compared with those of unsaturated polyester and furan resins alone, they show markedly improved flame retardance compared with that of the normally highly flammable unsaturated polyester. This increased flame retardance arises from a condensed phase mechanism in which the furanic component forms a semi-protective char, reducing rates of thermal degradation and total heat release and heat of combustion. The blends also burn with reduced smoke output compared with that from unsaturated polyester alone.

Waste package performance in unsaturated rock

International Nuclear Information System (INIS)

Pigford, T.H.; Lee, W.W.-L.

1989-03-01

The unsaturated rock and near-atmospheric pressure of the potential nuclear waste repository at Yucca Mountain present new problems of predicting waste package performance. In this paper we present some illustrations of predictions of waste package performance and discuss important data needs. 11 refs., 9 figs., 1 tab

Geophysical borehole logging in the unsaturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Schimschal, U.; Nelson, P.H.

1991-01-01

Borehole geophysical logging for site characterization in the volcanic rocks at the proposed nuclear waste repository at Yucca Mountain, Nevada, requires data collection under rather unusual conditions. Logging tools must operate in rugose, dry holes above the water table in the unsaturated zone. Not all logging tools will operate in this environment, therefore; careful consideration must be given to selection and calibration. A sample suite of logs is presented that demonstrates correlation of geological formations from borehole to borehole, the definition of zones of altered mineralogy, and the quantitative estimates of rock properties. The authors show the results of an exploratory calculation of porosity and water saturation based upon density and epithermal neutron logs. Comparison of the results with a few core samples is encouraging, particularly because the logs can provide continuous data in boreholes where core samples are not available

Hydrocarbons biodegradation in unsaturated porous medium

International Nuclear Information System (INIS)

Gautier, C.

2007-12-01

Biological processes are expected to play an important role in the degradation of petroleum hydrocarbons in contaminated soils. However, factors influencing the kinetics of biodegradation are still not well known, especially in the unsaturated zone. To address these biodegradation questions in the unsaturated zone an innovative experimental set up based on a physical column model was developed. This experimental set up appeared to be an excellent tool for elaboration of a structured porous medium, with well defined porous network and adjusted water/oil saturations. Homogeneous repartition of both liquid phases (i.e., aqueous and non aqueous) in the soil pores, which also contain air, was achieved using ceramic membranes placed at the bottom of the soil column. Reproducible interfaces (and connectivity) are developed between gas, and both non mobile water and NAPL phases, depending on the above-defined characteristics of the porous media and on the partial saturations of these three phases (NAPL, water and gas). A respirometric apparatus was coupled to the column. Such experimental set up have been validated with hexadecane in dilution in an HMN phase. This approach allowed detailed information concerning n-hexadecane biodegradation, in aerobic condition, through the profile of the oxygen consumption rate. We have taken benefit of this technique, varying experimental conditions, to determine the main parameters influencing the biodegradation kinetics and compositional evolution of hydrocarbons, under steady state unsaturated conditions and with respect to aerobic metabolism. Impacts of the nitrogen quantity and of three different grain sizes have been examined. Biodegradation of petroleum cut, as diesel cut and middle distillate without aromatic fraction, were, also studied. (author)

Hydrogeology of the unsaturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Montazer, P.; Wilson, W.E.

1985-01-01

The unsaturated volcanic tuff beneath Yucca Mountain, Nevada, is being evaluated by the US Department of Energy as a host rock for a potential mined geologic repository for high-level radioactive waste. Assessment of site suitability needs an efficient and focused investigative program. A conceptual hydrogeologic model that simulates the flow of fluids through the unsaturated zone at Yucca Mountain was developed to guide the program and to provide a basis for preliminary assessment of site suitability. The study was made as part of the Nevada Nuclear Waste Storage Investigations Project of the US Department of Energy. Thickness of the unsaturated zone is about 1640 to 2460 feet (500 to 750 meters). Based on physical properties, the rocks in the unsaturated zone are grouped for the purpose of this paper into five informal hydrogeologic units. From top to bottom these units are: Tiva Canyon welded unit, Paintbrush nonwelded unit. Topopah Spring welded unit, Calico Hills nonwelded unit, and Crater Flat unit. Welded units have a mean fracture density of 8 to 40 fractures per unit cubic meter, mean matrix porosities of 12 to 23%, matrix hydraulic conductivities with geometric means ranging from 6.5 x 10 -6 to 9.8 x 10 -6 foot per day (2 x 10 -6 to 3 x 10 -6 meter per day), and bulk hydraulic conductivities of 0.33 to 33 feet per day (0.1 to 10 meters per day). The nonwelded units have a mean fracture density of 1 to 3 fractures per unit cubic meter, mean matrix porosities of 31 to 46%, and saturated hydraulic conductivities with geometric means ranging from 2.6 x 10 -5 to 2.9 x 10 -2 foot per day (8 x 10 -6 to 9 x 10 -3 meter per day). 15 refs., 4 figs., 1 tab

Improved forward and inverse analyses of saturated-unsaturated flow toward a well in a compressible unconfined aquifer

Science.gov (United States)

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2010-07-01

We present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or unsaturated zone. We improve upon a previous such solution due to Tartakovsky and Neuman (2007) by (1) adopting a more flexible representation of unsaturated zone constitutive properties and (2) allowing the unsaturated zone to have finite thickness. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time; demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten-Mualem constitutive model; use our solution to analyze drawdown data from a pumping test conducted by the U.S. Geological Survey at Cape Cod, Massachusetts; and compare our estimates of van Genuchten-Mualem parameters with laboratory values obtained for similar materials in the area.

Unsaturated Lipids Change in Olive Tree Drupe and Seed during Fruit Development and in Response to Cold-Stress and Acclimation

Directory of Open Access Journals (Sweden)

Simone D’Angeli

2016-11-01

Full Text Available The olive tree is a plant of economic value for the oil of its drupe. It is a cultigen complex composed of genotypes with differences in cold-hardiness. About 90% of the oil is stored in oil bodies (OBs in the drupe during the oleogenic phase. Phenols and lipids contribute to oil quality, but the unsaturated fatty acid (FA fraction is emerging as the most important for quality, because of the very high content in oleic acid, the presence of ω6-linoleic acid and ω3-linolenic acid, and the very low saturated FA content. Another 10% of oil is produced by the seed. Differences in unsaturated FA-enriched lipids exist among seed coat, endosperm, and embryo. Olive oil quality is also affected by the environmental conditions during fruit growth and genotype peculiarities. Production of linoleic and α-linolenic acids, fruit growth, fruit and leaf responses to low temperatures, including cuticle formation, and cold-acclimation are related processes. The levels of unsaturated FAs are changed by FA-desaturase (FAD activities, involving the functioning of chloroplasts and endoplasmic reticulum. Cold induces lipid changes during drupe and seed development, affecting FADs, but its effect is related to the genotype capability to acclimate to the cold.

The foam drainage equation for drainage dynamics in unsaturated porous media

Science.gov (United States)

Lehmann, P.; Hoogland, F.; Assouline, S.; Or, D.

2017-07-01

Similarity in liquid-phase configuration and drainage dynamics of wet foam and gravity drainage from unsaturated porous media expands modeling capabilities for capillary flows and supplements the standard Richards equation representation. The governing equation for draining foam (or a soil variant termed the soil foam drainage equation—SFDE) obviates the need for macroscopic unsaturated hydraulic conductivity function by an explicit account of diminishing flow pathway sizes as the medium gradually drains. The study provides new and simple analytical expressions for drainage rates and volumes from unsaturated porous media subjected to different boundary conditions. Two novel analytical solutions for saturation profile evolution were derived and tested in good agreement with a numerical solution of the SFDE. The study and the proposed solutions rectify the original formulation of foam drainage dynamics of Or and Assouline (2013). The new framework broadens the scope of methods available for quantifying unsaturated flow in porous media, where the intrinsic conductivity and geometrical representation of capillary drainage could improve understanding of colloid and pathogen transport. The explicit geometrical interpretation of flow pathways underlying the hydraulic functions used by the Richards equation offers new insights that benefit both approaches.

Performance analyses and improvements for the IEEE 802.15.4 CSMA/CA scheme with heterogeneous buffered conditions.

Science.gov (United States)

Zhu, Jianping; Tao, Zhengsu; Lv, Chunfeng

2012-01-01

Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes-OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)-are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results.

Study on the concentration of unsaturated fatty acid methyl esters by urea complexation

International Nuclear Information System (INIS)

Jiang, B.; Liu, Y.

2014-01-01

This study was done to obtain concentrated unsaturated fatty acid methyl esters (FAME) by urea complexation from soybean derived FAME. Effects of urea-to-FAME ratio, 95% ethanol-to-FAME ratio, crystallization temperature and time on the purification of unsaturated FAME were investigated through single factor experiments. Optimum conditions to obtain maximum FAME yield of NUCF with the purity of unsaturated FAME greater than 98% were established using Box-Behnken design (BBD) method and response surface methodology (RSM). Under optimal conditions, the FAME yield was 58.08%, and the purity of unsaturated FAME was 98% at a urea-to-FAME ratio of 1.23, 95% ethanol-to-FAME ratio of 7 and crystallization temperature of 0 degree C. Verification results revealed that the predicted values were reasonably close to experimentally observed values of 56.93% and 98.01%. (author)

Measurement and modeling of flow through unsaturated heterogeneous rock in the context of geologic disposal of nuclear waste

International Nuclear Information System (INIS)

Sagar, B.; Bagtzoglou, A.C.; Green, R.T.; Stothoff, S.A.

1995-01-01

Deep geologic disposal of high-level and transuranic waste is currently being pursued vigorously. Assessing long-term performance of such repositories involves laboratory and field measurements, and numerical modeling. There exist two primary characteristics, associated with assessing repository performance, that define problems of modeling and measurement of non-isothermal flow through geologic media exposed to variable boundary conditions (e.g., climatic changes). These are: (1) the large time scale (tens of thousands of years) and highly variable space scale (from one meter to 10 5 meters); and (2) the hierarchy of heterogeneities and discontinuities characterizing the medium. This paper provides an overview of recent work, conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA), related to laboratory experiments, consideration of similitude, and numerical modeling of flow through heterogeneous media under non-homogeneous boundary conditions. As discussed, there exist neither good methods of measuring flows at these scales nor are there adequate similitude analyses that would allow reasonable scaling up of laboratory-scale experiments. Reliable assessment of long-term geologic repositories will require sophisticated geostatistical models capable of addressing variables scales of heterogeneities conditioned with observed results from adequately sized field-scale experiments conducted for sufficiently long durations

Process for making unsaturated hydrocarbons using microchannel process technology

Science.gov (United States)

Tonkovich, Anna Lee [Dublin, OH; Yuschak, Thomas [Lewis Center, OH; LaPlante, Timothy J [Columbus, OH; Rankin, Scott [Columbus, OH; Perry, Steven T [Galloway, OH; Fitzgerald, Sean Patrick [Columbus, OH; Simmons, Wayne W [Dublin, OH; Mazanec, Terry Daymo, Eric

2011-04-12

The disclosed invention relates to a process for converting a feed composition comprising one or more hydrocarbons to a product comprising one or more unsaturated hydrocarbons, the process comprising: flowing the feed composition and steam in contact with each other in a microchannel reactor at a temperature in the range from about 200.degree. C. to about 1200.degree. C. to convert the feed composition to the product, the process being characterized by the absence of catalyst for converting the one or more hydrocarbons to one or more unsaturated hydrocarbons. Hydrogen and/or oxygen may be combined with the feed composition and steam.

Determination of formation heterogeneity at a range of scales using novel multi-electrode resistivity scanning techniques

International Nuclear Information System (INIS)

Williams, G.M.; Jackson, P.D.; Ward, R.S.; Sen, M.A.; Meldrum, P.; Lovell, M.

1991-01-01

The traditional method of measuring ground resistivity involves passing a current through two outer electrodes, measuring the potential developed across two electrodes in between, and applying Ohm's Law. In the RESCAN system developed by the British Geological Survey, each electrode can be electronically selected and controlled by software to either pass current or measure potential. Thousands of electrodes can be attached to the system either in 2-D surface arrays or along special plastic covered probes driven vertically into the ground or emplaced in boreholes. Under computer control, the resistivity distribution within the emplaced array can be determined automatically with unprecedented detail and speed, and may be displayed as an image. So far, the RESCAN system has been applied at the meso-scale in monitoring the radial migration of an electrolyte introduced into a recharge well in an unconsolidated aquifer; and CORSCAN at the micro-scale on drill cores to evaluate spatial variability in physical properties. The RESCAN technique has considerable potential for determining formation heterogeneity at different scales and provides a basis for developing stochastic models of groundwater and solute flow in heterogeneous systems. 13 figs.; 1 tab.; 12 refs

Thermal history of the unsaturated zone at Yucca Mountain, Nevada, USA

Energy Technology Data Exchange (ETDEWEB)

Whelan, Joseph F. [U.S. Geological Survey, Box 25046, M.S. 963, Denver Federal Center, Denver, CO 80225 (United States)], E-mail: jfwhelan@usgs.gov; Neymark, Leonid A.; Moscati, Richard J.; Marshall, Brian D. [U.S. Geological Survey, Box 25046, M.S. 963, Denver Federal Center, Denver, CO 80225 (United States); Roedder, Edwin [Department of Earth and Planetary Science, Harvard University, Cambridge, MA 02138 (United States)

2008-05-15

Secondary calcite, silica and minor amounts of fluorite deposited in fractures and cavities record the chemistry, temperatures, and timing of past fluid movement in the unsaturated zone at Yucca Mountain, Nevada, the proposed site of a high-level radioactive waste repository. The distribution and geochemistry of these deposits are consistent with low-temperature precipitation from meteoric waters that infiltrated at the surface and percolated down through the unsaturated zone. However, the discovery of fluid inclusions in calcite with homogenization temperatures (T{sub h}) up to {approx}80 deg. C was construed by some scientists as strong evidence for hydrothermal deposition. This paper reports the results of investigations to test the hypothesis of hydrothermal deposition and to determine the temperature and timing of secondary mineral deposition. Mineral precipitation temperatures in the unsaturated zone are estimated from calcite- and fluorite-hosted fluid inclusions and calcite {delta}{sup 18}O values, and depositional timing is constrained by the {sup 207}Pb/{sup 235}U ages of chalcedony or opal in the deposits. Fluid inclusion T{sub h} from 50 samples of calcite and four samples of fluorite range from {approx}35 to {approx}90 deg. C. Calcite {delta}{sup 18}O values range from {approx}0 to {approx}22 per mille (SMOW) but most fall between 12 and 20 per mille . The highest T{sub h} and the lowest {delta}{sup 18}O values are found in the older calcite. Calcite T{sub h} and {delta}{sup 18}O values indicate that most calcite precipitated from water with {delta}{sup 18}O values between -13 and -7 per mille , similar to modern meteoric waters. Twenty-two {sup 207}Pb/{sup 235}U ages of chalcedony or opal that generally postdate elevated depositional temperatures range from {approx}9.5 to 1.9 Ma. New and published {sup 207}Pb/{sup 235}U and {sup 230}Th/Uages coupled with the T{sub h} values and estimates of temperature from calcite {delta}{sup 18}O values indicate

Growth of Synthrophomonas wolfei on unsaturated short chain fatty acids

Energy Technology Data Exchange (ETDEWEB)

Amos, D.A.; McInerney, M.J. (Univ. of Oklahoma, Norman, OK (United States))

1990-01-01

The anaerobic fatty acid-degrading syntrophic bacterium, Syntrophomonas wolfei, was grown in pure culture with either trans-2-pentenoate, trans-2-hexenoate, trans-3-hexenoate, or trans, trans-2, 4-hexadienoate as the substrate. Trans-2-pentenoate was fermented to acetate, propionate, butyrate, and valerate. Acetate, butyrate and hexanoate were produced from the six-carbon mono- and di-unsaturated acids. Propionate was also product from the trans, trans-2, 4-hexadienoate which suggested that compound was degraded by another pathway in addition to [beta]-oxidation. The transient production of trans-2-hexenoate from trans-3-hexenoate suggested that the position of the double bound shifted from carbon-3 to carbon-2 prior to [beta]-oxidation. The specific growth rate decreased with increasing carbon length and degree of unsaturation. Molar growth yields ranged from 8.4 to 17.5 mg (dry wt.) per mmol and suggested that energy was conserved not only from substrate-level phosphorylation, but also from the reduction of unsaturated substrate.

Unsaturated flow characterization utilizing water content data collected within the capillary fringe

Science.gov (United States)

Baehr, Arthur; Reilly, Timothy J.

2014-01-01

An analysis is presented to determine unsaturated zone hydraulic parameters based on detailed water content profiles, which can be readily acquired during hydrological investigations. Core samples taken through the unsaturated zone allow for the acquisition of gravimetrically determined water content data as a function of elevation at 3 inch intervals. This dense spacing of data provides several measurements of the water content within the capillary fringe, which are utilized to determine capillary pressure function parameters via least-squares calibration. The water content data collected above the capillary fringe are used to calculate dimensionless flow as a function of elevation providing a snapshot characterization of flow through the unsaturated zone. The water content at a flow stagnation point provides an in situ estimate of specific yield. In situ determinations of capillary pressure function parameters utilizing this method, together with particle-size distributions, can provide a valuable supplement to data libraries of unsaturated zone hydraulic parameters. The method is illustrated using data collected from plots within an agricultural research facility in Wisconsin.

Saturated and unsaturated stability analysis of slope subjected to rainfall infiltration

OpenAIRE

Gofar Nurly; Rahardjo Harianto

2017-01-01

This paper presents results of saturated and unsaturated stability analysis of typical residual slopes subjected to rainfall infiltration corresponds to 50 years rainfall return period. The slope angles considered were 45° and 70°. The saturated stability analyses were carried out for original and critical ground water level commonly considered by practicing engineer. The analyses were conducted using limit equilibrium method. Unsaturated stability analyses used combination of coupled stress–...

Creep model of unsaturated sliding zone soils and long-term deformation analysis of landslides

Science.gov (United States)

Zou, Liangchao; Wang, Shimei; Zhang, Yeming

2015-04-01

Sliding zone soil is a special soil layer formed in the development of a landslide. Its creep behavior plays a significant role in long-term deformation of landslides. Due to rainfall infiltration and reservoir water level fluctuation, the soils in the slide zone are often in unsaturated state. Therefore, the investigation of creep behaviors of the unsaturated sliding zone soils is of great importance for understanding the mechanism of the long-term deformation of a landslide in reservoir areas. In this study, the full-process creep curves of the unsaturated soils in the sliding zone in different net confining pressure, matric suctions and stress levels were obtained from a large number of laboratory triaxial creep tests. A nonlinear creep model for unsaturated soils and its three-dimensional form was then deduced based on the component model theory and unsaturated soil mechanics. This creep model was validated with laboratory creep data. The results show that this creep model can effectively and accurately describe the nonlinear creep behaviors of the unsaturated sliding zone soils. In order to apply this creep model to predict the long-term deformation process of landslides, a numerical model for simulating the coupled seepage and creep deformation of unsaturated sliding zone soils was developed based on this creep model through the finite element method (FEM). By using this numerical model, we simulated the deformation process of the Shuping landslide located in the Three Gorges reservoir area, under the cycling reservoir water level fluctuation during one year. The simulation results of creep displacement were then compared with the field deformation monitoring data, showing a good agreement in trend. The results show that the creeping deformations of landslides have strong connections with the changes of reservoir water level. The creep model of unsaturated sliding zone soils and the findings obtained by numerical simulations in this study are conducive to

The international INTRAVAL project. Phase 2, working group 1 report. Flow and tracer experiments in unsaturated tuff and soil. Las Cruces trench and Apache Leap tuff studies

International Nuclear Information System (INIS)

Nicholson, T.J.; Guzman-Guzman, A.; Hills, R.; Rasmussen, T.C.

1997-01-01

The Working Group 1 final report summaries two test case studies, the Las Cruces Trench (LCT), and Apache Leap Tuff Site (ALTS) experiments. The objectives of these two field studies were to evaluate models for water flow and contaminant transport in unsaturated, heterogeneous soils and fractured tuff. The LCT experiments were specifically designed to test various deterministic and stochastic models of water flow and solute transport in heterogeneous, unsaturated soils. Experimental data from the first tow LCT experiments, and detailed field characterisation studies provided information for developing and calibrating the models. Experimental results from the third experiment were held confidential from the modellers, and were used for model comparison. Comparative analyses included: point comparisons of water content; predicted mean behavior for water flow; point comparisons of solute concentrations; and predicted mean behavior for tritium transport. These analyses indicated that no model, whether uniform or heterogeneous, proved superior. Since the INTRAVAL study, however, a new method has been developed for conditioning the hydraulic properties used for flow and transport modelling based on the initial field-measured water content distributions and a set of scale-mean hydraulic parameters. Very good matches between the observed and simulated flow and transport behavior were obtained using the conditioning procedure, without model calibration. The ALTS experiments were designed to evaluate characterisation methods and their associated conceptual models for coupled matrix-fracture continua over a range of scales (i.e., 2.5 centimeter rock samples; 10 centimeter cores; 1 meter block; and 30 meter boreholes). Within these spatial scales, laboratory and field tests were conducted for estimating pneumatic, thermal, hydraulic, and transport property values for different conceptual models. The analyses included testing of current conceptual, mathematical and physical

Formation of doubly and triply bonded unsaturated compounds HCN, HNC, and CH2NH via N + CH4 low-temperature solid state reaction: from molecular clouds to solar system objects

Science.gov (United States)

Mencos, Alejandro; Krim, Lahouari

2018-06-01

We show in the current study carried out in solid phase at cryogenic temperatures that methane (CH4) ice exposed to nitrogen atoms is a source of two acids HCN, HNC, and their corresponding hydrogenated unsaturated species CH2NH, in addition to CH3, C2H6, CN-, and three nitrogen hydrides NH, NH2, and NH3. The solid state N + CH4 reaction taken in the ground state seems to be strongly temperature dependent. While at temperatures lower than 10 K only CH3, NH, NH2, and NH3 species formation is promoted due to CH bond dissociation and NH bond formation, stable compounds with CN bonds are formed at temperatures ranged between 10 and 40 K. Many of these reaction products, resulting from CH4 + N reaction, have already been observed in N2-rich regions such as the atmospheres of Titan, Kuiper belt objects, and molecular clouds of the interstellar medium. Our results show the power of the solid state N-atom chemistry in the transformation of simple astrochemical relevant species, such as CH4 molecules and N atoms into complex organic molecules which are also potentially prebiotic species.

Approaches to identifying reservoir heterogeneity and reserve growth opportunities from subsurface data: The Oficina Formation, Budare field, Venezuela

Energy Technology Data Exchange (ETDEWEB)

Hamilton, D.S.; Raeuchle, S.K.; Holtz, M.H. [Bureau of Economic Geology, Austin, TX (United States)] [and others

1997-08-01

We applied an integrated geologic, geophysical, and engineering approach devised to identify heterogeneities in the subsurface that might lead to reserve growth opportunities in our analysis of the Oficina Formation at Budare field, Venezuela. The approach involves 4 key steps: (1) Determine geologic reservoir architecture; (2) Investigate trends in reservoir fluid flow; (3) Integrate fluid flow trends with reservoir architecture; and (4) Estimate original oil-in-place, residual oil saturation, and remaining mobile oil, to identify opportunities for reserve growth. There are three main oil-producing reservoirs in the Oficina Formation that were deposited in a bed-load fluvial system, an incised valley-fill, and a barrier-strandplain system. Reservoir continuity is complex because, in addition to lateral facies variability, the major Oficina depositional systems were internally subdivided by high-frequency stratigraphic surfaces. These surfaces define times of intermittent lacustrine and marine flooding events that punctuated the fluvial and marginal marine sedimentation, respectively. Syn and post depositional faulting further disrupted reservoir continuity. Trends in fluid flow established from initial fluid levels, response to recompletion workovers, and pressure depletion data demonstrated barriers to lateral and vertical fluid flow caused by a combination of reservoir facies pinchout, flooding shale markers, and the faults. Considerable reserve growth potential exists at Budare field because the reservoir units are highly compartment by the depositional heterogeneity and structural complexity. Numerous reserve growth opportunities were identified in attics updip of existing production, in untapped or incompletely drained compartments, and in field extensions.

Intermediate Scale Laboratory Testing to Understand Mechanisms of Capillary and Dissolution Trapping during Injection and Post-Injection of CO₂ in Heterogeneous Geological Formations

Energy Technology Data Exchange (ETDEWEB)

Illangasekare, Tissa [Colorado School of Mines, Golden, CO (United States); Trevisan, Luca [Colorado School of Mines, Golden, CO (United States); Agartan, Elif [Colorado School of Mines, Golden, CO (United States); Mori, Hiroko [Colorado School of Mines, Golden, CO (United States); Vargas-Johnson, Javier [Colorado School of Mines, Golden, CO (United States); Gonzalez-Nicolas, Ana [Colorado School of Mines, Golden, CO (United States); Cihan, Abdullah [Colorado School of Mines, Golden, CO (United States); Birkholzer, Jens [Colorado School of Mines, Golden, CO (United States); Zhou, Quanlin [Colorado School of Mines, Golden, CO (United States)

2015-03-31

Carbon Capture and Storage (CCS) represents a technology aimed to reduce atmospheric loading of CO₂ from power plants and heavy industries by injecting it into deep geological formations, such as saline aquifers. A number of trapping mechanisms contribute to effective and secure storage of the injected CO₂ in supercritical fluid phase (scCO₂) in the formation over the long term. The primary trapping mechanisms are structural, residual, dissolution and mineralization. Knowledge gaps exist on how the heterogeneity of the formation manifested at all scales from the pore to the site scales affects trapping and parameterization of contributing mechanisms in models. An experimental and modeling study was conducted to fill these knowledge gaps. Experimental investigation of fundamental processes and mechanisms in field settings is not possible as it is not feasible to fully characterize the geologic heterogeneity at all relevant scales and gathering data on migration, trapping and dissolution of scCO₂. Laboratory experiments using scCO₂ under ambient conditions are also not feasible as it is technically challenging and cost prohibitive to develop large, two- or three-dimensional test systems with controlled high pressures to keep the scCO₂ as a liquid. Hence, an innovative approach that used surrogate fluids in place of scCO₂ and formation brine in multi-scale, synthetic aquifers test systems ranging in scales from centimeter to meter scale developed used. New modeling algorithms were developed to capture the processes controlled by the formation heterogeneity, and they were tested using the data from the laboratory test systems. The results and findings are expected to contribute toward better conceptual models, future improvements to DOE numerical codes, more accurate assessment of storage capacities, and optimized placement strategies. This report presents the experimental and modeling methods

Formation of Malondialdehyde, 4-Hydroxynonenal, and 4-Hydroxyhexenal during in Vitro Digestion of Cooked Beef, Pork, Chicken, and Salmon.

Science.gov (United States)

Steppeler, Christina; Haugen, John-Erik; Rødbotten, Rune; Kirkhus, Bente

2016-01-20

Red meat high in heme iron may promote the formation of potentially genotoxic aldehydes during lipid peroxidation in the gastrointestinal tract. In this study, the formation of malondialdehyde (MDA) equivalents measured by the thiobarbituric acid reactive substances (TBARS) method was determined during in vitro digestion of cooked red meat (beef and pork), as well as white meat (chicken) and fish (salmon), whereas analysis of 4-hydroxyhexenal (HHE) and 4-hydroxynonenal (HNE) was performed during in vitro digestion of cooked beef and salmon. Comparing products with similar fat contents indicated that the amount of unsaturated fat and not total iron content was the dominating factor influencing the formation of aldehydes. It was also shown that increasing fat content in beef products caused increasing concentrations of MDA equivalents. The highest levels, however, were found in minced beef with added fish oil high in unsaturated fat. This study indicates that when ingested alone, red meat products low in unsaturated fat and low in total fat content contribute to relatively low levels of potentially genotoxic aldehydes in the gastrointestinal tract.

FITTING OF THE DATA FOR DIFFUSION COEFFICIENTS IN UNSATURATED POROUS MEDIA

Energy Technology Data Exchange (ETDEWEB)

B. Bullard

1999-05-01

The purpose of this calculation is to evaluate diffusion coefficients in unsaturated porous media for use in the TSPA-VA analyses. Using experimental data, regression techniques were used to curve fit the diffusion coefficient in unsaturated porous media as a function of volumetric water content. This calculation substantiates the model fit used in Total System Performance Assessment-1995 An Evaluation of the Potential Yucca Mountain Repository (TSPA-1995), Section 6.5.4.

FITTING OF THE DATA FOR DIFFUSION COEFFICIENTS IN UNSATURATED POROUS MEDIA

International Nuclear Information System (INIS)

B. Bullard

1999-01-01

The purpose of this calculation is to evaluate diffusion coefficients in unsaturated porous media for use in the TSPA-VA analyses. Using experimental data, regression techniques were used to curve fit the diffusion coefficient in unsaturated porous media as a function of volumetric water content. This calculation substantiates the model fit used in Total System Performance Assessment-1995 An Evaluation of the Potential Yucca Mountain Repository (TSPA-1995), Section 6.5.4

Unsaturated carbone and allenylidene ruthenium complexes from alkynes

International Nuclear Information System (INIS)

Bozek, Yu.L.; Diznev, P.A.

1995-01-01

The author's studies aimed at activation of terminal alkynes by metal complexes, reactivity patterns and selective preparations of unsaturated carbene, allenylidene and cumulenylidene derivatives of (arene)ruthenium complexes are reviewed. 48 refs

Process for recovering oil from subterranean formations

International Nuclear Information System (INIS)

Knight, B.; Gogarty, W.B.

1978-01-01

Improved flooding of oil-bearing formations is obtained by injecting and displacing through the formation a saline solution containing a water-soluble, substantially linear, high molecular weight polymer obtained by irradiating an aqueous solution of an ethylenically unsaturated monomer and a water-soluble salt under controlled conditions of concentration, radiation intensity, conversion, and total radiation dose. The saline water can contain at least 15,000 ppm of TDS (total dissolved solids) and at least 50 ppm and preferably 300 ppm of polyvalent cations. (Auth.)

Oxygenation of saturated and unsaturated hydrocarbons with ...

Indian Academy of Sciences (India)

Unknown

Oxygenation of saturated and unsaturated hydrocarbons with sodium periodate. 431. Table 1. Competitive oxygenation of tetralin and cyclooctene with sodium periodate catalyzed by different manga- .... Teacher Education University. My grateful thanks also extend to Dr D Mohajer for his useful sugges- tions. References. 1.

A site-scale model for fluid and heat flow in the unsaturated zone of Yucca Mountain, Nevada

Science.gov (United States)

Wu, Yu-Shu; Haukwa, Charles; Bodvarsson, G. S.

1999-05-01

A three-dimensional unsaturated-zone numerical model has been developed to simulate flow and distribution of moisture, gas and heat at Yucca Mountain, Nevada, a potential repository site for high-level radioactive waste. The model takes into account the simultaneous flow dynamics of liquid water, vapor, air and heat in the highly heterogeneous, fractured porous rock in the unsaturated zone (UZ). This model is intended for use in the prediction of the current and future conditions in the UZ so as to aid in the assessment of the system performance of the proposed repository. The modeling approach is based on a mathematical formulation of coupled multiphase, multicomponent fluid and heat flow through porous and fractured rock. Fracture and matrix flow is treated using both dual-permeability and effective-continuum modeling approaches. The model domain covers a total area of approximately 43 km 2, and uses the land surface and the water table as its top and bottom boundaries. In addition, site-specific data, representative surface infiltration, and geothermal conditions are incorporated into the model. The reliability and accuracy of the model have been the subject of a comprehensive model calibration study, in which the model was calibrated against measured data, including liquid saturation, water potential and temperature. It has been found that the model is generally able to reproduce the overall system behavior at Yucca Mountain with respect to moisture profiles, pneumatic pressure variations in different geological units, and ambient geothermal conditions.

Organocatalytic Asymmetric Michael Addition of 4-Hydroxycoumarin to β,γ-Unsaturated α-Keto Esters

Energy Technology Data Exchange (ETDEWEB)

Suh, Chang Won; Han, Tae Hyun; Kim, Dae Young [Soonchunhyang Univ., Asan (Korea, Republic of)

2013-06-15

In conclusion, we have developed organocatalytic enantioselective conjugate addition reaction of 4-hydroxycoumarin (1) to β,γ-unsaturated α-keto esters 2 to afford biologically valuable warfarin derivatives 3. The process is efficiently catalyzed by a binaphthyl-modified thiourea organocatalyst. The coumarin core is present as a characteristic structural motif in a large number of natural products and biologically active molecules.1 Particularly, many of these naturally occurring 4-hydroxycoumarin and their synthetic analogues are important precursors for the synthesis of natural products and pharmaceuticals. Enantioselective organocatalytic conjugate addition of 4-hydroxycoumarin to α,β-unsaturated ketones is a straightforward method to access warfarin which is an effective anticoagulants. Although a number of reactions of α,β-unsaturated ketones as Michael acceptors have been reported, the corresponding β,γ-unsaturated α-keto esters have received relatively little attention as Michael acceptors. Recently, several groups have reported the asymmetric Michael addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters catalyzed by Cu(II)-bisoxazoline, N,N'-dioxide-Ni(II) complexes, thiourea catalysts. Although several efficient methods have been achieved by these systems, an effective method for the synthesis of warfarin analogues is still a challenge.

Organocatalytic Asymmetric Michael Addition of 4-Hydroxycoumarin to β,γ-Unsaturated α-Keto Esters

International Nuclear Information System (INIS)

Suh, Chang Won; Han, Tae Hyun; Kim, Dae Young

2013-01-01

In conclusion, we have developed organocatalytic enantioselective conjugate addition reaction of 4-hydroxycoumarin (1) to β,γ-unsaturated α-keto esters 2 to afford biologically valuable warfarin derivatives 3. The process is efficiently catalyzed by a binaphthyl-modified thiourea organocatalyst. The coumarin core is present as a characteristic structural motif in a large number of natural products and biologically active molecules.1 Particularly, many of these naturally occurring 4-hydroxycoumarin and their synthetic analogues are important precursors for the synthesis of natural products and pharmaceuticals. Enantioselective organocatalytic conjugate addition of 4-hydroxycoumarin to α,β-unsaturated ketones is a straightforward method to access warfarin which is an effective anticoagulants. Although a number of reactions of α,β-unsaturated ketones as Michael acceptors have been reported, the corresponding β,γ-unsaturated α-keto esters have received relatively little attention as Michael acceptors. Recently, several groups have reported the asymmetric Michael addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters catalyzed by Cu(II)-bisoxazoline, N,N'-dioxide-Ni(II) complexes, thiourea catalysts. Although several efficient methods have been achieved by these systems, an effective method for the synthesis of warfarin analogues is still a challenge

Single-Step Access to Long-Chain α,ω-Dicarboxylic Acids by Isomerizing Hydroxycarbonylation of Unsaturated Fatty Acids

KAUST Repository

Goldbach, Verena

2016-11-09

Dicarboxylic acids are compounds of high value, but to date long-chain alpha,omega-dicarboxylic acids have been difficult to access in a direct way. Unsaturated fatty acids are ideal starting materials with their molecular structure of long methylene sequences and a carboxylate functionality, in addition to a double bond that offers itself for functionalization. Within this paper, we established a direct access to alpha,omega-dicarboxylic acids by combining isomerization and selective terminal carbonylation of the internal double bond with water as a nucleophile on unsaturated fatty acids. We identified the key elements of this reaction: a homogeneous reaction mixture ensuring sufficient contact between all reactants and a catalyst system allowing for activation of the Pd precursor under aqueous conditions. Experiments under pressure reactor conditions with [(dtbpx)Pd(OTf)(2)] as catalyst precursor revealed the importance of nucleophile and reactant concentrations and the addition of the diprotonated diphosphine ligand (dtbpxH(2))(OTf)(2) to achieve turnover numbers >120. A variety of unsaturated fatty acids, including a triglyceride, were converted to valuable long-chain dicarboxylic acids with high turnover numbers and selectivities for the linear product of >90%. We unraveled the activation pathway of the Pd-II precursor, which proceeds via a reductive elimination step forming a Pd species and oxidative addition of the diprotonated diphosphine ligand, resulting in the formation of the catalytically active Pd hydride species. Theoretical calculations identified the hydrolysis as the rate-determining step. A low nucleophile concentration in the reaction mixture in combination with this high energetic barrier limits the potential of this reaction. In conclusion, water can be utilized as a nucleophile in isomerizing functionalization reactions and gives access to long-chain dicarboxylic acids from a variety of unsaturated substrates. The activity of the catalytic

Saturated-unsaturated flow to a partially penetrating well with storage in a compressible aquifer

Science.gov (United States)

Mishra, P. K.; Neuman, S. P.

2010-12-01

Mishra and Neuman [2010] developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or the unsaturated zone. We extend their solution to the case of a finite diameter pumping well with storage. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten - Mualem constitutive model; and use our solution to analyze drawdown data from a pumping test conducted at the Borden site in Ontario, Canada.

Transformation of Unsaturated Fatty Acids/Esters to Corresponding Keto Fatty Acids/Esters by Aerobic Oxidation with Pd(II)/Lewis Acid Catalyst.

Science.gov (United States)

Senan, Ahmed M; Zhang, Sicheng; Zeng, Miao; Chen, Zhuqi; Yin, Guochuan

2017-08-16

Utilization of renewable biomass to partly replace the fossil resources in industrial applications has attracted attention due to the limited fossil feedstock with the increased environmental concerns. This work introduced a modified Wacker-type oxidation for transformation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, in which Cu 2+ cation was replaced with common nonredox metal ions, that is, a novel Pd(II)/Lewis acid (LA) catalyst. It was found that adding nonredox metal ions can effectively promote Pd(II)-catalyzed oxidation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, even much better than Cu 2+ , and the promotional effect is highly dependent on the Lewis acidity of added nonredox metal ions. The improved catalytic efficiency is attributed to the formation of heterobimetallic Pd(II)/LA species, and the oxidation mechanism of this Pd(II)/LA catalyst is also briefly discussed.

Quantification of groundwater recharge through application of pilot techniques in the unsaturated zone.

Science.gov (United States)

Kallioras, Andreas; Piepenbrink, Matthias; Schuth, Christoph; Pfletschinger, Heike; Dietrich, Peter; Koeniger, Franz; Rausch, Randolf

2010-05-01

Accurate determination of groundwater recharge is a key issue for the "smart mining" of groundwater resources. Groundwater recharge estimation techniques depend on the investigated hydrologic zone, and therefore main approaches are based on (a) unsaturated zone, (b) saturated zone and (c) surface water studies. This research contributes to the determination of groundwater recharge by investigating the infiltration of groundwater through the unsaturated zone. The investigations are conducted through the application of a combination of different pilot field as well as lab techniques. The field techniques include the installation of specially designed Time Domain Reflectometry (TDR) sensors, at different depths within the unsaturated zone for in-situ and continuous measurements of the volumetric pore water content. Additionally, the extraction of pore water -for analysis of its isotopic composition- from multilevel undisturbed soil samples through significant depths within the unsaturated zone column, enables the dating of the groundwater age through the determination of its isotopic composition. The in-situ investigation of the unsaturated zone is complemented by the determination of high resolution temperature profiles. The installation of the pilot TDR sensors is achieved by using direct push methods at significant depths within the unsaturated zone, providing continuous readings of the soil moisture content. The direct push methods are also ideal for multilevel sampling of undisturbed -without using any drilling fluids which affect the isotopic composition of the containing pore water- soil and consequent extraction of the included pore water for further isotopic determination. The pore water is extracted by applying the method of azeotropic distillation; a method which has the least isotopic fractionation effects on groundwater samples. The determination of different isotopic signals such as 18O, 2H, 3H, and 36Cl, aims to the investigation of groundwater transit

Complex Binding of the FabR Repressor of Bacterial Unsaturated Fatty Acid Biosynthesis to its Cognate Promoters

OpenAIRE

Feng, Youjun; Cronan, John E.

2011-01-01

Two transcriptional regulators, the FadR activator and the FabR repressor control biosynthesis of unsaturated fatty acids in Escherichia coli. FabR represses expression of the two genes, fabA and fabB, required for unsaturated fatty acid synthesis and has been reported to require the presence of an unsaturated thioester (of either acyl carrier protein or CoA) in order to bind the fabA and fabB promoters in vitro. We report in vivo experiments in which unsaturated fatty acid synthesis was bloc...

Biodegradation of vapor-phase toluene in unsaturated porous media: Column experiments

International Nuclear Information System (INIS)

Khan, Ali M.; Wick, Lukas Y.; Harms, Hauke; Thullner, Martin

2016-01-01

Biodegradation of organic chemicals in the vapor phase of soils and vertical flow filters has gained attention as promising approach to clean up volatile organic compounds (VOC). The drivers of VOC biodegradation in unsaturated systems however still remain poorly understood. Here, we analyzed the processes controlling aerobic VOC biodegradation in a laboratory setup mimicking the unsaturated zone above a shallow aquifer. The setup allowed for diffusive vapor-phase transport and biodegradation of three VOC: non-deuterated and deuterated toluene as two compounds of highly differing biodegradability but (nearly) identical physical and chemical properties, and MTBE as (at the applied experimental conditions) non-biodegradable tracer and internal control. Our results showed for toluene an effective microbial degradation within centimeter VOC transport distances despite high gas-phase diffusivity. Degradation rates were controlled by the reactivity of the compounds while oxic conditions were found everywhere in the system. This confirms hypotheses that vadose zone biodegradation rates can be extremely high and are able to prevent the outgassing of VOC to the atmosphere within a centimeter range if compound properties and site conditions allow for sufficiently high degradation rates. - Highlights: • The column setup allows resolving vapor-phase VOC concentration gradients at cm scale resolution. • Vapor-phase and liquid-phase concentrations are measured simultaneously. • Isotopically labelled VOC was used as reference species of low biodegradability. • Biodegradation rates in the unsaturated zone can be very high and act at a cm scale. • Unsaturated material can be an effective bio-barrier avoiding biodegradable VOC emissions. - Microbial degradation activity can be sufficient to remove VOC from unsaturated porous media after a few centimeter of vapor-phase diffusive transport and mayeffectively avoid atmospheric emissions.

Drilling and coring methods that minimize the disturbance of cuttings, core, and rock formation in the unsaturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Hammermeister, D.P.; Blout, D.O.; McDaniel, J.C.

1985-01-01

A drilling-and-casing method (Odex 115 system) utilizing air as a drilling fluid was used successfully to drill through various rock types within the unsaturated zone at Yucca Mountain, Nevada. This paper describes this method and the equipment used to rapidly penetrate bouldery alluvial-colluvial deposits, poorly consolidated bedded and nonwelded tuff, and fractured, densely welded tuff to depths of about 130 meters. A comparison of water-content and water-potential data from drill cuttings with similar measurements on rock cores indicates that drill cuttings were only slightly disturbed for several of the rock types penetrated. Coring, sampling, and handling methods were devised to obtain minimally disturbed drive core from bouldery alluvial-colluvial deposits. Bulk-density values obtained from bulk samples dug from nearby trenches were compared to bulk-density values obtained from drive core to determine the effects of drive coring on the porosity of the core. Rotary coring methods utilizing a triple-tube core barrel and air as the drilling fluid were used to obtain core from welded and nonwelded tuff. Results indicate that the disturbance of the water content of the core was minimal. Water-content distributions in alluvium-colluvium were determined before drilling occurred by drive-core methods. After drilling, water-content distributions were determined by nuclear-logging methods. A comparison of the water-content distributions made before and after drilling indicates that Odex 115 drilling minimally disturbs the water content of the formation rock. 10 refs., 12 figs., 4 tabs

Improved solution for saturated-unsaturated flow to a partially penetrating well in a compressible unconfined aquifer

Science.gov (United States)

Mishra, P. K.; Neuman, S. P.

2009-12-01

Tartakovsky and Neuman [2007] developed an analytical solution for flow to a partially penetrating well pumping at a constant rate from a compressible unconfined aquifer considering an unsaturated zone of infinite thickness. In their solution three-dimensional, axially symmetric unsaturated flow was described by a linearized version of Richards’ equation in which both relative hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value. Both exponential functions were characterized by a common exponent. We present an improved solution in which relative hydraulic conductivity and water content are characterized by separate parameters and the unsaturated zone has finite thickness. Our four-parameter representation of these functions is more flexible than the three-parameter version of Mathias and Butler [2006], who consider flow in the unsaturated zone to be strictly vertical and the pumping well to be fully penetrating. We investigate the effects of unsaturated zone thickness and constitutive parameters on drawdown in the unsaturated and saturated zones as functions of position and time. We then use our new solution to analyze data from synthetic and real pumping tests.

Enhanced Attenuation of Unsaturated Chlorinated Solvent Source Zones using Direct Hydrogen Delivery

Science.gov (United States)

2013-01-01

solvents. This approach for bioremediation of unsaturated soils containing chlorinated solvents was originally proposed in a patent by Hughes et al...have been conducted on the use of hydrogen as an electron donor for the anaerobic bioremediation of saturated and unsaturated porous media (Evans and...proven to be very effective in remediating releases of petroleum products including gasoline, jet fuels, kerosene, and diesel fuel. Several field

Water transport monitoring in an unsaturated zone – Case study: lysimeter Selniška dobrava (Slovenia

Directory of Open Access Journals (Sweden)

Nina Mali

2002-12-01

Full Text Available Pollution transport in an aquifer depends on its structure, upper unsaturated zone and lower saturated zone. In order to understand processes in the unsaturated zone, several hydrogeological field measurements must be done. A field laboratory- lysimeter in Selni{kadobrava was installed for the improvement of field measurements, and explanation of the parameters and processes in the unsaturated zone. The problems, which can be solved by means of investigations in a lysimeter, are defined in this paper. Described are also:concept of investigation planning, construction and equipment of the lysimeter, measurements of unsaturated zone parameters and processes, water sampling for physical, chemical and isotope analysis.

Residual mitochondrial transmembrane potential decreases unsaturated fatty acid level in sake yeast during alcoholic fermentation

Directory of Open Access Journals (Sweden)

Kazutaka Sawada

2016-01-01

Full Text Available Oxygen, a key nutrient in alcoholic fermentation, is rapidly depleted during this process. Several pathways of oxygen utilization have been reported in the yeast Saccharomyces cerevisiae during alcoholic fermentation, namely synthesis of unsaturated fatty acid, sterols and heme, and the mitochondrial electron transport chain. However, the interaction between these pathways has not been investigated. In this study, we showed that the major proportion of unsaturated fatty acids of ester-linked lipids in sake fermentation mash is derived from the sake yeast rather than from rice or koji (rice fermented with Aspergillus. Additionally, during alcoholic fermentation, inhibition of the residual mitochondrial activity of sake yeast increases the levels of unsaturated fatty acids of ester-linked lipids. These findings indicate that the residual activity of the mitochondrial electron transport chain reduces molecular oxygen levels and decreases the synthesis of unsaturated fatty acids, thereby increasing the synthesis of estery flavors by sake yeast. This is the first report of a novel link between residual mitochondrial transmembrane potential and the synthesis of unsaturated fatty acids by the brewery yeast during alcoholic fermentation.

Performance Analyses and Improvements for the IEEE 802.15.4 CSMA/CA Scheme with Heterogeneous Buffered Conditions

Directory of Open Access Journals (Sweden)

Chunfeng Lv

2012-04-01

Full Text Available Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results.

Influence of Nutrient Availability and Quorum Sensing on the Formation of Metabolically Inactive Microcolonies Within Structurally Heterogeneous Bacterial Biofilms: An Individual-Based 3D Cellular Automata Model.

Science.gov (United States)

Machineni, Lakshmi; Rajapantul, Anil; Nandamuri, Vandana; Pawar, Parag D

2017-03-01

The resistance of bacterial biofilms to antibiotic treatment has been attributed to the emergence of structurally heterogeneous microenvironments containing metabolically inactive cell populations. In this study, we use a three-dimensional individual-based cellular automata model to investigate the influence of nutrient availability and quorum sensing on microbial heterogeneity in growing biofilms. Mature biofilms exhibited at least three structurally distinct strata: a high-volume, homogeneous region sandwiched between two compact sections of high heterogeneity. Cell death occurred preferentially in layers in close proximity to the substratum, resulting in increased heterogeneity in this section of the biofilm; the thickness and heterogeneity of this lowermost layer increased with time, ultimately leading to sloughing. The model predicted the formation of metabolically dormant cellular microniches embedded within faster-growing cell clusters. Biofilms utilizing quorum sensing were more heterogeneous compared to their non-quorum sensing counterparts, and resisted sloughing, featuring a cell-devoid layer of EPS atop the substratum upon which the remainder of the biofilm developed. Overall, our study provides a computational framework to analyze metabolic diversity and heterogeneity of biofilm-associated microorganisms and may pave the way toward gaining further insights into the biophysical mechanisms of antibiotic resistance.

Volatile organic compounds in the unsaturated zone from radioactive wastes

Science.gov (United States)

Baker, Ronald J.; Andraski, Brian J.; Stonestrom, David A.; Luo, Wentai

2012-01-01

Volatile organic compounds (VOCs) are often comingled with low-level radioactive wastes (LLRW), but little is known about subsurface VOC emanations from LLRW landfills. The current study systematically quantified VOCs associated with LLRW over an 11-yr period at the USGS Amargosa Desert Research Site (ADRS) in southwestern Nevada. Unsaturated-zone gas samples of VOCs were collected by adsorption on resin cartridges and analyzed by thermal desorption and GC/MS. Sixty of 87 VOC method analytes were detected in the 110-m-thick unsaturated zone surrounding a LLRW disposal facility. Chlorofluorocarbons (CFCs) were detected in 100% of samples collected. Chlorofluorocarbons are powerful greenhouse gases, deplete stratospheric ozone, and are likely released from LLRW facilities worldwide. Soil-gas samples collected from a depth of 24 m and a horizontal distance 100 m south of the nearest waste-disposal trench contained >60,000 ppbv total VOCs, including >37,000 ppbv CFCs. Extensive sampling in the shallow unsaturated zone (0–2 m deep) identified areas where total VOC concentrations exceeded 5000 ppbv at the 1.5-m depth. Volatile organic compound concentrations exceeded background levels up to 300 m from the facility. Maximum vertical diffusive fluxes of total VOCs were estimated to be 1 g m-2 yr-1. Volatile organic compound distributions were similar but not identical to those previously determined for tritium and elemental mercury. To our knowledge, this study is the first to characterize the unsaturated zone distribution of VOCs emanating from a LLRW landfill. Our results may help explain anomalous transport of radionuclides at the ADRS and elsewhere.

Thermo-hydro mechanical modeling in unsaturated hard clay: application to nuclear waste storage

International Nuclear Information System (INIS)

Jia, Y.

2006-07-01

This work presents an elastoplastic damage model for argillite in unsaturated conditions. A short resume of experimental investigations is presented in the first part. The results obtained show an important plastic deformation coupled with damage induced by initiation and growth of microcracks. Influences of water content on the mechanical behaviour are also investigated. Based on experimental data and micro-mechanical considerations, a general constitutive model is proposed for the poro-mechanical behavior of argillite in unsaturated conditions. The time dependent creep has also been incorporated in they model. The performance of the model is examined by comparing numerical simulation with experimental data in various load paths under saturated and unsaturated conditions. Finally, the model is applied to hydro-mechanical coupling study of the REP experiment and thermo-hydro-mechanical coupling study of the HE-D experiment. A good agreement is obtained between experimental data and numerical predictions. It has been shown that the proposed model describe correctly the main features of the mechanical behaviour of unsaturated rocks. (author)

Review and selection of unsaturated flow models

Energy Technology Data Exchange (ETDEWEB)

Reeves, M.; Baker, N.A.; Duguid, J.O. [INTERA, Inc., Las Vegas, NV (United States)

1994-04-04

Since the 1960`s, ground-water flow models have been used for analysis of water resources problems. In the 1970`s, emphasis began to shift to analysis of waste management problems. This shift in emphasis was largely brought about by site selection activities for geologic repositories for disposal of high-level radioactive wastes. Model development during the 1970`s and well into the 1980`s focused primarily on saturated ground-water flow because geologic repositories in salt, basalt, granite, shale, and tuff were envisioned to be below the water table. Selection of the unsaturated zone at Yucca Mountain, Nevada, for potential disposal of waste began to shift model development toward unsaturated flow models. Under the US Department of Energy (DOE), the Civilian Radioactive Waste Management System Management and Operating Contractor (CRWMS M&O) has the responsibility to review, evaluate, and document existing computer models; to conduct performance assessments; and to develop performance assessment models, where necessary. This document describes the CRWMS M&O approach to model review and evaluation (Chapter 2), and the requirements for unsaturated flow models which are the bases for selection from among the current models (Chapter 3). Chapter 4 identifies existing models, and their characteristics. Through a detailed examination of characteristics, Chapter 5 presents the selection of models for testing. Chapter 6 discusses the testing and verification of selected models. Chapters 7 and 8 give conclusions and make recommendations, respectively. Chapter 9 records the major references for each of the models reviewed. Appendix A, a collection of technical reviews for each model, contains a more complete list of references. Finally, Appendix B characterizes the problems used for model testing.

Review and selection of unsaturated flow models

International Nuclear Information System (INIS)

Reeves, M.; Baker, N.A.; Duguid, J.O.

1994-01-01

Since the 1960's, ground-water flow models have been used for analysis of water resources problems. In the 1970's, emphasis began to shift to analysis of waste management problems. This shift in emphasis was largely brought about by site selection activities for geologic repositories for disposal of high-level radioactive wastes. Model development during the 1970's and well into the 1980's focused primarily on saturated ground-water flow because geologic repositories in salt, basalt, granite, shale, and tuff were envisioned to be below the water table. Selection of the unsaturated zone at Yucca Mountain, Nevada, for potential disposal of waste began to shift model development toward unsaturated flow models. Under the US Department of Energy (DOE), the Civilian Radioactive Waste Management System Management and Operating Contractor (CRWMS M ampersand O) has the responsibility to review, evaluate, and document existing computer models; to conduct performance assessments; and to develop performance assessment models, where necessary. This document describes the CRWMS M ampersand O approach to model review and evaluation (Chapter 2), and the requirements for unsaturated flow models which are the bases for selection from among the current models (Chapter 3). Chapter 4 identifies existing models, and their characteristics. Through a detailed examination of characteristics, Chapter 5 presents the selection of models for testing. Chapter 6 discusses the testing and verification of selected models. Chapters 7 and 8 give conclusions and make recommendations, respectively. Chapter 9 records the major references for each of the models reviewed. Appendix A, a collection of technical reviews for each model, contains a more complete list of references. Finally, Appendix B characterizes the problems used for model testing

A Hydromechanic-Electrokinetic Model for CO2 Sequestration in Geological Formations

NARCIS (Netherlands)

Al-Khoury, R.I.N.; Talebian, M.; Sluys, L.J.

2013-01-01

In this contribution, a finite element model for simulating coupled hydromechanic and electrokinetic flow in a multiphase domain is outlined. The model describes CO2 flow in a deformed, unsaturated geological formation and its associated streaming potential flow. The governing field equations are

A quasilinear model for solute transport under unsaturated flow

International Nuclear Information System (INIS)

Houseworth, J.E.; Leem, J.

2009-01-01

We developed an analytical solution for solute transport under steady-state, two-dimensional, unsaturated flow and transport conditions for the investigation of high-level radioactive waste disposal. The two-dimensional, unsaturated flow problem is treated using the quasilinear flow method for a system with homogeneous material properties. Dispersion is modeled as isotropic and is proportional to the effective hydraulic conductivity. This leads to a quasilinear form for the transport problem in terms of a scalar potential that is analogous to the Kirchhoff potential for quasilinear flow. The solutions for both flow and transport scalar potentials take the form of Fourier series. The particular solution given here is for two sources of flow, with one source containing a dissolved solute. The solution method may easily be extended, however, for any combination of flow and solute sources under steady-state conditions. The analytical results for multidimensional solute transport problems, which previously could only be solved numerically, also offer an additional way to benchmark numerical solutions. An analytical solution for two-dimensional, steady-state solute transport under unsaturated flow conditions is presented. A specific case with two sources is solved but may be generalized to any combination of sources. The analytical results complement numerical solutions, which were previously required to solve this class of problems.

Unsaturated flow and transport through fractured rock related to high-level waste repositories

International Nuclear Information System (INIS)

Evans, D.D.; Rasmussen, T.C.

1991-01-01

Research results are summarized for a US Nuclear Regulatory Commission contract with the University of Arizona focusing on field and laboratory methods for characterizing unsaturated fluid flow and solute transport related to high-level radioactive waste repositories. Characterization activities are presented for the Apache Leap Tuff field site. The field site is located in unsaturated, fractured tuff in central Arizona. Hydraulic, pneumatic, and thermal characteristics of the tuff are summarized, along with methodologies employed to monitor and sample hydrologic and geochemical processes at the field site. Thermohydrologic experiments are reported which provide laboratory and field data related to the effects conditions and flow and transport in unsaturated, fractured rock. 29 refs., 17 figs., 21 tabs

Electrocatalytic hydrogenation and hydrodeoxygenation of oxygenated and unsaturated organic compounds

Energy Technology Data Exchange (ETDEWEB)

Jackson, James E.; Lam, Chun Ho; Saffron, Christopher M.; Miller, Dennis J.

2018-04-24

A process and related electrode composition are disclosed for the electrocatalytic hydrogenation and/or hydrodeoxygenation of organic substrates such as biomass-derived bio-oil components by the production of hydrogen atoms on a catalyst surface followed by the reaction of the hydrogen atoms with the organic reactants. Biomass fast pyrolysis-derived bio-oil is a liquid mixture containing hundreds of organic compounds with chemical functionalities that are corrosive to container materials and are prone to polymerization. A high surface area skeletal metal catalyst material such as Raney Nickel can be used as the cathode. Electrocatalytic hydrogenation and/or hydrodeoxygenation convert the organic substrates under mild conditions to reduce coke formation and catalyst deactivation. The process converts oxygen-containing functionalities and unsaturated bonds into chemically reduced forms with an increased hydrogen content. The process is operated at mild conditions, which enables it to be a good means for stabilizing bio-oil to a form that can be stored and transported using metal containers and pipes.

BUILDING CONCEPTUAL AND MATHEMATICAL MODEL FOR WATER FLOW AND SOLUTE TRANSPORT IN THE UNSATURATED ZONE AT KOSNICA SITE

Directory of Open Access Journals (Sweden)

Stanko Ružičić

2012-12-01

Full Text Available Conceptual model of flow and solute transport in unsaturated zone at Kosnica site, which is the basis for modeling pollution migration through the unsaturated zone to groundwater, is set up. The main characteristics of the unsaturated zone of the Kosnica site are described. Detailed description of investigated profile of unsaturated zone, with all necessary analytical results performed and used in building of conceptual models, is presented. Experiments that are in progress and processes which are modeled are stated. Monitoring of parameters necessary for calibration of models is presented. The ultimate goal of research is risk assessment of groundwater contamination at Kosnica site that has its source in or on unsaturated zone.

Unsaturated polyester resin composition curable with ionizing radiations

International Nuclear Information System (INIS)

Maruyama, Tsutomu; Murata, Koichiro.

1971-01-01

An unsaturated polyester resin composition curable with ionizing radiations and excellent in weather resistance is provided. The composition is obtained by reacting 10-12 moles of a polyhydric alcohol (e.g. ethylene glycol) with 10 moles of an acid mixture (25.45% by mole of endo-cis-bicyclo (2,2,1)-5-heptene-2-3-dicarboxylic acid (A), 20-40% of unsaturated dibasic acid and 15-55% of saturated dibasic acid) so that the acid value reaches 4-11. The composition is useful as coating, laminating and molding materials. As a coating material it is excellent in surface hardening property. The ionizing radiation used is preferably β-, α-rays or electron beams. In one example, and unsaturated polyester was prepared by reacting 3 moles of fumaric acid, 2 moles of phthalic anhydride, 3 moles of adipic acid 3, moles of (A), 10 moles of neopentyl glycol and 1 mole of trimethylolpropane. The resin was dissolved into a mixture of styrene, methyl methacrylate and butyl acrylate (50:8:42) and incorporated with titanium white. An ABS plate was coated with the enamel thus obtained and irradiated with electron beams (12 Mrad). In exposure test at 60 0 C, luster of the film was 92 before exposure and 83 after 30 months. In a comparative run in which (A) was not used, luster of the film decreased from 90 to 45 in 30 months. (Sakaichi, S.)

Unsaturated-zone fast-path flow calculations for Yucca Mountain groundwater travel time analyses (GWTT-94)

International Nuclear Information System (INIS)

Arnold, B.W.; Altman, S.J.; Robey, T.H.

1995-08-01

Evaluation of groundwater travel time (GWTT) is required as part of the investigation of the suitability of Yucca Mountain as a potential high-level nuclear-waste repository site. The Nuclear Regulatory Commission's GWTT regulation is considered to be a measure of the intrinsic ability of the site to contain radionuclide releases from the repository. The work reported here is the first step in a program to provide an estimate of GWTT at the Yucca Mountain site in support of the DOE's Technical Site Suitability and as a component of a license application. Preliminary estimation of the GWTT distribution in the unsaturated zone was accomplished using a numerical model of the physical processes of groundwater flow in the fractured, porous medium of the bedrock. Based on prior investigations of groundwater flow at the site, fractures are thought to provide the fastest paths for groundwater flow; conditions that lead to flow in fractures were investigated and simulated. Uncertainty in the geologic interpretation of Yucca Mountain was incorporated through the use of geostatistical simulations, while variability of hydrogeologic parameters within each unit was accounted for by the random sampling of parameter probability density functions. The composite-porosity formulation of groundwater flow was employed to simulate flow in both the matrix and fracture domains. In this conceptualization, the occurrence of locally saturated conditions within the unsaturated zone is responsible for the initiation of fast-path flow through fractures. The results of the GWTT-94 study show that heterogeneity in the hydraulic properties of the model domain is an important factor in simulating local regions of high groundwater saturation. Capillary-pressure conditions at the surface boundary influence the extent of the local saturation simulated

Simulation of the degradation of a concrete/clay interface: influence of temperature, unsaturated conditions and porosity variations

International Nuclear Information System (INIS)

Burnol, A.; Dupros, F.; Spycher, N.; Xu, T.; Gaucher, E.C.

2006-01-01

For long-lived intermediate-level radioactive waste, the use of concrete as engineering barrier and Callovian-Oxfordian clay as geological barrier at a depth of 500 m is considered in the French disposal concept (ANDRA, 2005). Upon emplacement, initially unsaturated concrete is expected to experience coupled processes involving heating, re-saturation with groundwater from the clay formation, gas exchanges and geochemical reactions. After an early period of re-saturation, solute transport is supposed to be diffusion-controlled because of the extremely low permeability of the two media. These coupled processes may lead to changes in the porosity of the concrete or clay barriers. In the present paper, a fully coupled Thermo-Hydro-Chemical (THC) response of a two-phase (gas and solution) mass-transfer model was evaluated and tested by a sensitivity analysis. This study is an extension of a previous model applied to an isothermal and fully saturated concrete/clay interface (Burnol et al., 2005); it investigated the coupled effect of temperature and unsaturated conditions assuming no production of H2(g). The system was simulated for a 2000-year period, which covers the most predominant thermal perturbation

FTIR study of hydrogen bonding interaction between fluorinated alcohol and unsaturated esters

Science.gov (United States)

Sheng, Xia; Jiang, Xiaotong; Zhao, Hailiang; Wan, Dongjin; Liu, Yongde; Ngwenya, Cleopatra Ashley; Du, Lin

2018-06-01

The 1:1 complexes of two unsaturated esters with 2,2,2-trifluoroethanol (TFE) were investigated experimentally and computationally. The experimental observations of the spectral shifts of the OH-stretching vibrational transitions were obtained at 113 cm-1 for TFE-methyl acrylate (MA) and 92 cm-1 for TFE-vinyl acetate (VA). There are three docking sites in the two unsaturated esters for the incoming TFE. The predicted red shifts of the OH-stretching vibrational transitions were found to be larger for the Osbnd H⋯Odbnd C hydrogen bonded conformer than those for the Osbnd H⋯π and Osbnd H⋯O ones. The binding energies further prove that the Osbnd H⋯Odbnd C hydrogen bonded conformers are the most stable ones. On the basis of the DFT calculations as well as previous works, the carbonyl group is the best docking site for TFE. Furthermore, the thermodynamic equilibrium constants of TFE-MA and TFE-VA were obtained at 0.28 and 0.15 by combining the experimental spectra data and the DFT calculations. Consequently, the Gibbs free energies of formation were determined to be 3.2 and 4.8 kJ mol-1 for TFE-MA and TFE-VA, respectively. The quantum theory of atoms in molecules (AIM) and generalized Kohn-Sham energy decomposition analysis (GKS-EDA) were carried out for further characterization of the hydrogen bonding interactions. GKS-EDA shows an "electrostatic" dominated hydrogen bonding character for the Osbnd H⋯Odbnd C hydrogen bonds.

Prices and heterogeneous search costs

NARCIS (Netherlands)

Luis Moraga-Gonzalez, Jose; Sandor, Zsolt; Wildenbeest, Matthijs R.

2017-01-01

We study price formation in a model of consumer search for differentiated products in which consumers have heterogeneous search costs. We provide conditions under which a pure-strategy symmetric Nash equilibrium exists and is unique. Search costs affect two margins-the intensive search margin (or

Unsaturated Zone Effects in Predicting Landslide and Debris-Flow Initiation

Science.gov (United States)

Baum, R. L.; Godt, J. W.; Savage, W. Z.

2006-12-01

Many destructive debris flows begin as shallow landslides induced by direct infiltration of intense rainfall and storm runoff into hillside materials. Predicting the timing and location of debris-flow initiation is needed to assess the debris-flow hazard of an area. Theoretical models and real-time monitoring of rainfall infiltration into unsaturated hillside materials provide useful insights into the mechanisms and timing of rainfall-induced landslides. We modeled the infiltration process using a two-layer system that consists of an unsaturated zone above a saturated zone, and then implemented this model in a GIS framework. The model couples analytical solutions for transient, unsaturated, vertical infiltration above the water table to pressure-diffusion solutions for pressure changes below the water table. The solutions are coupled through a transient water table that rises as water accumulates at the base of the unsaturated zone. This scheme, though limited to simplified soil- water characteristics and moist initial conditions, greatly improves computational efficiency over numerical models in spatially distributed modeling applications. Pore pressures computed by these coupled models are subsequently used in slope-stability computations to estimate the timing and locations of slope failures. Preliminary model results indicate that the unsaturated layer attenuates and delays the rainfall-induced pore- pressure response at depth, consistent with observations at an instrumented hillside near Edmonds, Washington. This attenuation reduces the area of false-positive predictions (when compared with results of linear models for suction-saturated initial conditions) in distributed application of the model over an area. Modeling indicates that initial wetness of the hillside materials affects the intensity and duration of rainfall required to trigger shallow landslides and consequently the timing of their occurrence, a result that is also consistent with observations of

Effects of Unsaturated Zones on Baseflow Recession: Analytical Solution and Application

Science.gov (United States)

Zhan, H.; Liang, X.; Zhang, Y. K.

2017-12-01

Unsaturated flow is an important process in baseflow recessions and its effect is rarely investigated. A mathematical model for a coupled unsaturated-saturated flow in a horizontally unconfined aquifer with time-dependent infiltrations is presented. Semi-analytical solutions for hydraulic heads and discharges are derived using Laplace transform and Cosine transform. The solutions are compared with solutions of the linearized Boussinesq equation (LB solution) and the linearized Laplace equation (LL solution), respectively. The result indicates that a larger dimensionless constitutive exponent κD of the unsaturated zone leads to a smaller discharge during the infiltration period and a larger discharge after the infiltration. The lateral discharge of the unsaturated zone is significant when κD≤1, and becomes negligible when κD≥100. For late times, the power index b of the recession curve-dQ/dt aQb, is 1 and independent of κD, where Q is the baseflow and a is a constant lumped aquifer parameter. For early times, b is approximately equal to 3 but it approaches infinity when t→1. The present solution is applied to synthetic and field cases. The present solution matched the synthetic data better than both the LL and LB solutions, with a minimum relative error of 16% for estimate of hydraulic conductivity. The present solution was applied to the observed streamflow discharge in Iowa, and the estimated values of the aquifer parameters were reasonable.

A study on in-situ measuring method and modeling technique of an unsaturated zone

Energy Technology Data Exchange (ETDEWEB)

Imai, Hisashi [Hazama Corp., Tsukuba, Ibaraki (Japan). Technical Research Inst.; Amemiya, Kiyoshi; Nishida, Kaoru; Lin, Weiren; Lei, Xinglin

1997-03-01

It is generally considered that an unsaturated zone is generated in the vicinity of a drift after excavation. In such a zone, invasion of air containing oxygen possibly changes geochemical environment (redox condition) of the rock mass. However, no measurement technique for quantitative understanding of this unsaturated zone is currently available. This study has been started to develop the measuring method in the several years. This year, fundamental information has been obtained through analysis, laboratory experiments using homogeneous rock samples and field measurement described below. (1) experiments on the mechanism of undersaturation in rock. (2) experiments on the measuring method of the extend of unsaturated zone. (author)

36Cl measurements of the unsaturated zone flux at Yucca Mountain

International Nuclear Information System (INIS)

Norris, A.E.; Wolfsberg, K.; Gifford, S.K.

1985-01-01

Determining the unsaturated zone percolation rate, or flux, is an extremely important site characterization issue for the proposed Yucca Mountain nuclear waste repository. A new technique that measures the 36 Cl content of tuff from the Exploratory Shaft will be used to calculate flux through the unsaturated zone over longer times than could be measured by the more conventional 14 C method. Measurements of the 36 Cl ''bomb pulse'' in soil samples from Yucca Mountain have been used to confirm that infiltration is not an important recharge mechanism. 5 refs., 3 figs

Gas breakthrough and emission through unsaturated compacted clay in landfill final cover

International Nuclear Information System (INIS)

Ng, C.W.W.; Chen, Z.K.; Coo, J.L.; Chen, R.; Zhou, C.

2015-01-01

Highlights: • Explore feasibility of unsaturated clay as a gas barrier in landfill cover. • Gas breakthrough pressure increases with clay thickness and degree of saturation. • Gas emission rate decreases with clay thickness and degree of saturation. • A 0.6 m-thick clay layer may be sufficient to meet gas emission rate limit. - Abstract: Determination of gas transport parameters in compacted clay plays a vital role for evaluating the effectiveness of soil barriers. The gas breakthrough pressure has been widely studied for saturated swelling clay buffer commonly used in high-level radioactive waste disposal facility where the generated gas pressure is very high (in the order of MPa). However, compacted clay in landfill cover is usually unsaturated and the generated landfill gas pressure is normally low (typically less than 10 kPa). Furthermore, effects of clay thickness and degree of saturation on gas breakthrough and emission rate in the context of unsaturated landfill cover has not been quantitatively investigated in previous studies. The feasibility of using unsaturated compacted clay as gas barrier in landfill covers is thus worthwhile to be explored over a wide range of landfill gas pressures under various degrees of saturation and clay thicknesses. In this study, to evaluate the effectiveness of unsaturated compacted clay to minimize gas emission, one-dimensional soil column tests were carried out on unsaturated compacted clay to determine gas breakthrough pressures at ultimate limit state (high pressure range) and gas emission rates at serviceability limit state (low pressure range). Various degrees of saturation and thicknesses of unsaturated clay sample were considered. Moreover, numerical simulations were carried out using a coupled gas–water flow finite element program (CODE-BRIGHT) to better understand the experimental results by extending the clay thickness and varying the degree of saturation to a broader range that is typical at different

Gas breakthrough and emission through unsaturated compacted clay in landfill final cover

Energy Technology Data Exchange (ETDEWEB)

Ng, C.W.W.; Chen, Z.K.; Coo, J.L. [Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Chen, R., E-mail: chenrui1005@hotmail.com [Shenzhen Key Laboratory of Urban and Civil Engineering for Disaster Prevention and Mitigation, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518055 (China); Zhou, C. [Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2015-10-15

Highlights: • Explore feasibility of unsaturated clay as a gas barrier in landfill cover. • Gas breakthrough pressure increases with clay thickness and degree of saturation. • Gas emission rate decreases with clay thickness and degree of saturation. • A 0.6 m-thick clay layer may be sufficient to meet gas emission rate limit. - Abstract: Determination of gas transport parameters in compacted clay plays a vital role for evaluating the effectiveness of soil barriers. The gas breakthrough pressure has been widely studied for saturated swelling clay buffer commonly used in high-level radioactive waste disposal facility where the generated gas pressure is very high (in the order of MPa). However, compacted clay in landfill cover is usually unsaturated and the generated landfill gas pressure is normally low (typically less than 10 kPa). Furthermore, effects of clay thickness and degree of saturation on gas breakthrough and emission rate in the context of unsaturated landfill cover has not been quantitatively investigated in previous studies. The feasibility of using unsaturated compacted clay as gas barrier in landfill covers is thus worthwhile to be explored over a wide range of landfill gas pressures under various degrees of saturation and clay thicknesses. In this study, to evaluate the effectiveness of unsaturated compacted clay to minimize gas emission, one-dimensional soil column tests were carried out on unsaturated compacted clay to determine gas breakthrough pressures at ultimate limit state (high pressure range) and gas emission rates at serviceability limit state (low pressure range). Various degrees of saturation and thicknesses of unsaturated clay sample were considered. Moreover, numerical simulations were carried out using a coupled gas–water flow finite element program (CODE-BRIGHT) to better understand the experimental results by extending the clay thickness and varying the degree of saturation to a broader range that is typical at different

Statistical Estimation of Heterogeneities: A New Frontier in Well Testing

Science.gov (United States)

Neuman, S. P.; Guadagnini, A.; Illman, W. A.; Riva, M.; Vesselinov, V. V.

2001-12-01

Well-testing methods have traditionally relied on analytical solutions of groundwater flow equations in relatively simple domains, consisting of one or at most a few units having uniform hydraulic properties. Recently, attention has been shifting toward methods and solutions that would allow one to characterize subsurface heterogeneities in greater detail. On one hand, geostatistical inverse methods are being used to assess the spatial variability of parameters, such as permeability and porosity, on the basis of multiple cross-hole pressure interference tests. On the other hand, analytical solutions are being developed to describe the mean and variance (first and second statistical moments) of flow to a well in a randomly heterogeneous medium. Geostatistical inverse interpretation of cross-hole tests yields a smoothed but detailed "tomographic" image of how parameters actually vary in three-dimensional space, together with corresponding measures of estimation uncertainty. Moment solutions may soon allow one to interpret well tests in terms of statistical parameters such as the mean and variance of log permeability, its spatial autocorrelation and statistical anisotropy. The idea of geostatistical cross-hole tomography is illustrated through pneumatic injection tests conducted in unsaturated fractured tuff at the Apache Leap Research Site near Superior, Arizona. The idea of using moment equations to interpret well-tests statistically is illustrated through a recently developed three-dimensional solution for steady state flow to a well in a bounded, randomly heterogeneous, statistically anisotropic aquifer.

Aquifer Recharge Estimation In Unsaturated Porous Rock Using Darcian And Geophysical Methods.

Science.gov (United States)

Nimmo, J. R.; De Carlo, L.; Masciale, R.; Turturro, A. C.; Perkins, K. S.; Caputo, M. C.

2016-12-01

Within the unsaturated zone a constant downward gravity-driven flux of water commonly exists at depths ranging from a few meters to tens of meters depending on climate, medium, and vegetation. In this case a steady-state application of Darcy's law can provide recharge rate estimates.We have applied an integrated approach that combines field geophysical measurements with laboratory hydraulic property measurements on core samples to produce accurate estimates of steady-state aquifer recharge, or, in cases where episodic recharge also occurs, the steady component of recharge. The method requires (1) measurement of the water content existing in the deep unsaturated zone at the location of a core sample retrieved for lab measurements, and (2) measurement of the core sample's unsaturated hydraulic conductivity over a range of water content that includes the value measured in situ. Both types of measurements must be done with high accuracy. Darcy's law applied with the measured unsaturated hydraulic conductivity and gravitational driving force provides recharge estimates.Aquifer recharge was estimated using Darcian and geophysical methods at a deep porous rock (calcarenite) experimental site in Canosa, southern Italy. Electrical Resistivity Tomography (ERT) and Vertical Electrical Sounding (VES) profiles were collected from the land surface to water table to provide data for Darcian recharge estimation. Volumetric water content was estimated from resistivity profiles using a laboratory-derived calibration function based on Archie's law for rock samples from the experimental site, where electrical conductivity of the rock was related to the porosity and water saturation. Multiple-depth core samples were evaluated using the Quasi-Steady Centrifuge (QSC) method to obtain hydraulic conductivity (K), matric potential (ψ), and water content (θ) estimates within this profile. Laboratory-determined unsaturated hydraulic conductivity ranged from 3.90 x 10-9 to 1.02 x 10-5 m

Role of unsaturated soil in a waste containment system

Energy Technology Data Exchange (ETDEWEB)

Lim, P.C.; Tay, J.H. [Nanyang Technological Univ. (Singapore)

1996-12-31

The role of the unsaturated properties of sand as a drainage layer in a composite liner system for landfills is investigated. The effect of the unsaturated properties of coarse-grained soil on contaminant migration was evaluated by means of a series of simulations using a one-dimensional model of a two- and a three-layer soil liner system for advection and diffusion, respectively. The results showed that under seepage conditions, the effect of an unsaturated sand layer on the advancement of the concentration front was quite insignificant. The arrival time of the C/C{sub o} = 0.5 concentration front increased from 651 days for the case with no sand layer to approximately 951 days for the case with a 1.0-m sand layer. A steady-state flow condition was ultimately established in the sand, and this fact suggests that the capillary action might not be effective. For diffusion, the arrival time of the concentration front increased nonlinearly with a decrease in the degree of saturation and linearly with increasing depths of the sand layer. At a residual degree of saturation, the arrival times of the C/C{sub o} = 0.01 and 0.5 concentration front at the base of the 1-m sand layer were 26.9 and 877.4 years as compared to 1.52 and 2.62 years by advection, respectively. 17 refs., 11 figs.

Discrete Element Method for Modeling the Mechanical Behavior of Unsaturated Granular Material

Directory of Open Access Journals (Sweden)

K. Tourani

2016-09-01

Full Text Available Although a significant portion of conditions encountered in geotechnical engineering, for investigating engineering behavior of soil, involves unsaturated soils; the traditional analysis and design approach has been to assume the limiting conditions of soils being either completely dry or completely saturated. In unsaturated soils the capillary force produce attractive forces between particles. Discrete Element Method (DEM is an appropriate tool to consider the capillary effects. The calculations performed in DEM is based on iterative application of Newton’s second law to the particles and force-displacement law at the contacts. In the present study, the behavior of unsaturated soils in pendular regime is simulated utilizing DEM. Triaxial  compression tests were modeled as two-dimensional, considering capillary force effects. Finally, capillary effects on Macro parameters of a simulated granular soil (stress, axial strain, volumetric strain and void ratio and Mohr Coulomb failure criteria parameters were studied.

Impact of bimodal textural heterogeneity and connectivity on flow and transport through unsaturated mine waste rock

Science.gov (United States)

Appels, Willemijn M.; Ireson, Andrew M.; Barbour, S. Lee

2018-02-01

Mine waste rock dumps have highly variable flowpaths caused by contrasting textures and geometry of materials laid down during the 'plug dumping' process. Numerical experiments were conducted to investigate how these characteristics control unsaturated zone flow and transport. Hypothetical profiles of inner-lift structure were generated with multiple point statistics and populated with hydraulic parameters of a finer and coarser material. Early arrival of water and solutes at the bottom of the lifts was observed after spring snowmelt. The leaching efficiency, a measure of the proportion of a resident solute that is flushed out of the rock via infiltrating snowmelt or rainfall, was consistently high, but modified by the structure and texture of the lift. Under high rates of net percolation during snowmelt, preferential flow was generated in coarse textured part of the rock, and solutes in the fine textured parts of the rock remained stagnant. Under lower rates of net percolation during the summer and fall, finer materialswere flushed too, and the spatial variability of solute concentration in the lift was reduced. Layering of lifts leads to lower flow rates at depth, minimizing preferential flow and increased leaching of resident solutes. These findings highlight the limited role of large scale connected geometries on focusing flow and transport under dynamic surface net percolation conditions. As such, our findings agree with recent numerical results from soil studies with Gaussian connected geometries as well as recent experimental findings, emphasizing the dominant role of matrix flow and high leaching efficiency in large waste rock dumps.

Geologic character of tuffs in the unsaturated zone at Yucca Mountain, southern Nevada

International Nuclear Information System (INIS)

Scott, R.B.; Spengler, R.W.; Diehl, S.; Lappin, A.R.; Chornack, M.P.

1982-01-01

At Yucca Mountain, a potential site for a high-level nuclear waste repository on the Nevada Test Site in southern Nevada, evaluation of the geologic setting and rock physical properties, along with previous regional hydrologic studies, has provided background that can be used for construction of a preliminary conceptual hydrologic model of the unsaturated zone. The 500-m-thick unsaturated portion of Yucca Mountain consists of alternating layers of two contrasting types of tuff. One type consists of highly fractured, densely welded, relatively nonporous but highly transmissive ash-flow tuffs. The other type consists of relatively unfractured, nonwelded, highly porous but relatively nontransmissive, argillic and zeolitic bedded tuffs and ash-flow tuffs. The contrast between these two sets of distinctive physical properties results in a stratified sequence best described as ''physical-property stratigraphy'' as opposed to traditional petrologic stratigraphy of volcanic rocks. The vast majority of recharge through the unsaturated zone is assumed to be vertical; the dominant migration may occur in fractures of densely welded tuffs and in the matrix of nonwelded tuff, but the mode of fluid flow in these unsaturated systems is undetermined. Limited lateral flow of recharge may occur at horizons where local perched water tables may exist above relatively nontransmissive zeolitized nonwelded tuffs. The pervasive north-northwest-striking fractures may control the direction of lateral flow of recharge, if any, in the unsaturated zone, and certainly that direction coincides closely with the observed southeasterly flow direction in the saturated zone under Yucca Mountain. Empirical evaluation of this conceptual hydrologic model has begun. 41 refs., 18 figs., 2 tabs

Geologic character of tuffs in the unsaturated zone at Yucca Mountain, southern Nevada

Energy Technology Data Exchange (ETDEWEB)

Scott, R.B.; Spengler, R.W.; Diehl, S.; Lappin, A.R.; Chornack, M.P.

1982-12-31

At Yucca Mountain, a potential site for a high-level nuclear waste repository on the Nevada Test Site in southern Nevada, evaluation of the geologic setting and rock physical properties, along with previous regional hydrologic studies, has provided background that can be used for construction of a preliminary conceptual hydrologic model of the unsaturated zone. The 500-m-thick unsaturated portion of Yucca Mountain consists of alternating layers of two contrasting types of tuff. One type consists of highly fractured, densely welded, relatively nonporous but highly transmissive ash-flow tuffs. The other type consists of relatively unfractured, nonwelded, highly porous but relatively nontransmissive, argillic and zeolitic bedded tuffs and ash-flow tuffs. The contrast between these two sets of distinctive physical properties results in a stratified sequence best described as "physical-property stratigraphy" as opposed to traditional petrologic stratigraphy of volcanic rocks. The vast majority of recharge through the unsaturated zone is assumed to be vertical; the dominant migration may occur in fractures of densely welded tuffs and in the matrix of nonwelded tuff, but the mode of fluid flow in these unsaturated systems is undetermined. Limited lateral flow of recharge may occur at horizons where local perched water tables may exist above relatively nontransmissive zeolitized nonwelded tuffs. The pervasive north-northwest-striking fractures may control the direction of lateral flow of recharge, if any, in the unsaturated zone, and certainly that direction coincides closely with the observed southeasterly flow direction in the saturated zone under Yucca Mountain. Empirical evaluation of this conceptual hydrologic model has begun. 41 refs., 18 figs., 2 tabs.

Rhodium-catalyzed asymmetric hydroboration of γ,δ-unsaturated amide derivatives: δ-borylated amides.

Science.gov (United States)

Hoang, G L; Zhang, S; Takacs, J M

2018-05-08

γ,δ-Unsaturated amides in which the alkene moiety bears an aryl or heteroaryl substituent undergo regioselective rhodium-catalyzed δ-borylation by pinacolborane to afford chiral secondary benzylic boronic esters. The results contrast the γ-borylation of γ,δ-unsaturated amides in which the disubstituted alkene moiety bears only alkyl substituents; the reversal in regiochemistry is coupled with a reversal in the sense of π-facial selectivity.

Application of Stochastic Unsaturated Flow Theory, Numerical Simulations, and Comparisons to Field Observations

DEFF Research Database (Denmark)

Jensen, Karsten Høgh; Mantoglou, Aristotelis

1992-01-01

unsaturated flow equation representing the mean system behavior is solved using a finite difference numerical solution technique. The effective parameters are evaluated from the stochastic theory formulas before entering them into the numerical solution for each iteration. The stochastic model is applied...... seems to offer a rational framework for modeling large-scale unsaturated flow and estimating areal averages of soil-hydrological processes in spatially variable soils....

Temperature Dependence in Homogeneous and Heterogeneous Nucleation

Energy Technology Data Exchange (ETDEWEB)

McGraw R. L.; Winkler, P. M.; Wagner, P. E.

2017-08-01

Heterogeneous nucleation on stable (sub-2 nm) nuclei aids the formation of atmospheric cloud condensation nuclei (CCN) by circumventing or reducing vapor pressure barriers that would otherwise limit condensation and new particle growth. Aerosol and cloud formation depend largely on the interaction between a condensing liquid and the nucleating site. A new paper published this year reports the first direct experimental determination of contact angles as well as contact line curvature and other geometric properties of a spherical cap nucleus at nanometer scale using measurements from the Vienna Size Analyzing Nucleus Counter (SANC) (Winkler et al., 2016). For water nucleating heterogeneously on silver oxide nanoparticles we find contact angles around 15 degrees compared to around 90 degrees for the macroscopically measured equilibrium angle for water on bulk silver. The small microscopic contact angles can be attributed via the generalized Young equation to a negative line tension that becomes increasingly dominant with increasing curvature of the contact line. These results enable a consistent theoretical description of heterogeneous nucleation and provide firm insight to the wetting of nanosized objects.

Hydrochemical investigations in characterizing the unsaturated zone at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Yang, I.C.; Rattray, G.W.; Ferarese, J.S.; Yu, P.; Ryan, J.N.

1998-01-01

Hydrochemical and isotopic investigations of ground water at Yucca Mountain, Nevada, site of a potential permanent national nuclear-waste repository, demonstrate that younger rocks are dominated by calcium-sulfate or calcium-chloride water and that older rocks contain sodium-carbonate or sodium-bicarbonate water. Furthermore, unsaturated-zone pore water has significantly larger concentrations of major ions and dissolved solids than does the saturated-zone water. Recharge of perched or saturated-zone water, therefore, requires rapid flow through fractures or permeable regions in the unsaturated zone to avoid mixing with the chemically concentrated water in the unsaturated zone. This conceptual model is consistent with observations of rapidly moved post-bomb (post-1954) tritium and chlorine-36 in the deep unsaturated zone at Yucca Mountain. Presence of post-bomb tritium in matrix water away from fracture zones further indicates that parts of the fast-flow water that moves through fractures have been diverted laterally into nonwelded units. Experimental data show that different lithologic units require specific water-extraction methods for stable-isotope analyses of hydrogen and oxygen to ensure accurate characterization. Vacuum-distillation and compression-extraction methods both can yield accurate data but must be used with specific lithologies. Column experiments demonstrate that percolating water can exchange with pore water of the core as well as water held in zeolite minerals in the core. Exchange rates range from days to months. Pore-water samples from core, therefore, reflect the most recently infiltrated water but do not reflect percolating water of the distant past

Model simulations with COSMO-SPECS: impact of heterogeneous freezing modes and ice nucleating particle types on ice formation and precipitation in a deep convective cloud

Directory of Open Access Journals (Sweden)

K. Diehl

2018-03-01

Full Text Available In deep convective clouds, heavy rain is often formed involving the ice phase. Simulations were performed using the 3-D cloud resolving model COSMO-SPECS with detailed spectral microphysics including parameterizations of homogeneous and three heterogeneous freezing modes. The initial conditions were selected to result in a deep convective cloud reaching 14 km of altitude with strong updrafts up to 40 m s−1. At such altitudes with corresponding temperatures below −40 °C the major fraction of liquid drops freezes homogeneously. The goal of the present model simulations was to investigate how additional heterogeneous freezing will affect ice formation and precipitation although its contribution to total ice formation may be rather low. In such a situation small perturbations that do not show significant effects at first sight may trigger cloud microphysical responses. Effects of the following small perturbations were studied: (1 additional ice formation via immersion, contact, and deposition modes in comparison to solely homogeneous freezing, (2 contact and deposition freezing in comparison to immersion freezing, and (3 small fractions of biological ice nucleating particles (INPs in comparison to higher fractions of mineral dust INP. The results indicate that the modification of precipitation proceeds via the formation of larger ice particles, which may be supported by direct freezing of larger drops, the growth of pristine ice particles by riming, and by nucleation of larger drops by collisions with pristine ice particles. In comparison to the reference case with homogeneous freezing only, such small perturbations due to additional heterogeneous freezing rather affect the total precipitation amount. It is more likely that the temporal development and the local distribution of precipitation are affected by such perturbations. This results in a gradual increase in precipitation at early cloud stages instead of a strong increase at

Fe-Catalyzed Oxidative Cleavage of Unsaturated Fatty Acids

NARCIS (Netherlands)

Spannring, P.

2013-01-01

The oxidative cleavage of unsaturated fatty acids into aldehydes or carboxylic acids gives access to valuable products. The products can be used as chemical building blocks, as emulsifiers or in the paint or polymer industry. Ozonolysis is applied industrially to cleave the fatty acid oleic acid

Quasi‐steady centrifuge method for unsaturated hydraulic properties

Science.gov (United States)

Caputo, Maria C.; Nimmo, John R.

2005-01-01

We have developed the quasi‐steady centrifuge (QSC) method as a variation of the steady state centrifuge method that can be implemented simply and inexpensively with greater versatility in terms of sample size and other features. It achieves these advantages by somewhat relaxing the criterion for steadiness of flow through the sample. This compromise entails an increase in measurement uncertainty but to a degree that is tolerable in most applications. We have tested this new approach with an easily constructed apparatus to establish a quasi‐steady flow of water in unsaturated porous rock samples spinning in a centrifuge, obtaining measurements of unsaturated hydraulic conductivity and water retention that agree with results of other methods. The QSC method is adaptable to essentially any centrifuge suitable for hydrogeologic applications, over a wide range of sizes and operating speeds. The simplified apparatus and greater adaptability of this method expands the potential for exploring situations that are common in nature but have been the subject of few laboratory investigations.

Quasi-steady centrifuge method for unsaturated hydraulic properties

Science.gov (United States)

Caputo, Maria C.; Nimmo, John R.

2005-11-01

We have developed the quasi-steady centrifuge (QSC) method as a variation of the steady state centrifuge method that can be implemented simply and inexpensively with greater versatility in terms of sample size and other features. It achieves these advantages by somewhat relaxing the criterion for steadiness of flow through the sample. This compromise entails an increase in measurement uncertainty but to a degree that is tolerable in most applications. We have tested this new approach with an easily constructed apparatus to establish a quasi-steady flow of water in unsaturated porous rock samples spinning in a centrifuge, obtaining measurements of unsaturated hydraulic conductivity and water retention that agree with results of other methods. The QSC method is adaptable to essentially any centrifuge suitable for hydrogeologic applications, over a wide range of sizes and operating speeds. The simplified apparatus and greater adaptability of this method expands the potential for exploring situations that are common in nature but have been the subject of few laboratory investigations.

Simulation of groundwater flows in unsaturated porous media

International Nuclear Information System (INIS)

Musy, A.

1976-01-01

Groundwater flow in unsaturated porous media is caused by a potential gradient where the total potential consists of the sum of a gravitational and a suction component. The partial differential equations which result from the general analysis of groundwater flow in unsaturated soil are solved by succesive approximations with the finite-element method. General boundary and initial conditions, linear or curvilinear shaped elements (isoparametric elements) and steady-state or transient flow can be introduced into the numerical computer program. The results of this mathematical model are compared with experimental data established in the laboratory with a physical groundwater model. This is a rectangular testing tank of dimension 3 x 1.5 x 0.15 m and contains a silty clay loam. The variation of the bulk density and the volumetric moisture of the soil as a function of time and space are measured by gamma absorption from a 137 Cs source with 300 mCi intensity

Heterogeneous seeding of HET-s(218–289) and the mutability of prion structures

Energy Technology Data Exchange (ETDEWEB)

Wan, William; Stubbs, Gerald

2014-02-18

One fundamental property of prions is the formation of strains—prions that have distinct biological effects, despite a common amino acid sequence. The strain phenomenon is thought to be caused by the formation of different molecular structures, each encoding for a particular biological activity. While the precise mechanism of the formation of strains is unknown, they tend to arise following environmental changes, such as passage between different species. One possible mechanism discussed here is heterogeneous seeding; the formation of a prion nucleated by a different molecular structure. While heterogeneous seeding is not the only mechanism of prion mutation, it is consistent with some observations on species adaptation and drug resistance. Heterogeneous seeding provides a useful framework to understand how prions can adapt to new environmental conditions and change biological phenotypes.

Unsaturated Fatty Acids Supplementation Reduces Blood Lead Level in Rats

Science.gov (United States)

Skoczyńska, Anna; Wojakowska, Anna; Nowacki, Dorian; Bobak, Łukasz; Turczyn, Barbara; Smyk, Beata; Szuba, Andrzej; Trziszka, Tadeusz

2015-01-01

Some dietary factors could inhibit lead toxicity. The aim of this study was to evaluate the effect of dietary compounds rich in unsaturated fatty acids (FA) on blood lead level, lipid metabolism, and vascular reactivity in rats. Serum metallothionein and organs' lead level were evaluated with the aim of assessing the possible mechanism of unsaturated FA impact on blood lead level. For three months, male Wistar rats that were receiving drinking water with (100 ppm Pb) or without lead acetate were supplemented per os daily with virgin olive oil or linseed oil (0.2 mL/kg b.w.) or egg derived lecithin fraction: “super lecithin” (50 g/kg b.w.). Mesenteric artery was stimulated ex vivo by norepinephrine (NE) administered at six different doses. Lecithin supplementation slightly reduced pressor responses of artery to NE. Lead administered to rats attenuated the beneficial effect of unsaturated FA on lipid metabolism and vascular reactivity to adrenergic stimulation. On the other hand, the super lecithin and linseed oil that were characterized by low omega-6 to omega-3 ratio (about 1) reduced the blood lead concentration. This effect was observed in lead poisoned rats (p < 0.0001) and also in rats nonpoisoned with lead (p < 0.05). PMID:26075218

Damping Effect of an Unsaturated-Saturated System on Tempospatial Variations of Pressure Head and Specific Flux

Science.gov (United States)

Yang, C.; Zhang, Y. K.; Liang, X.

2014-12-01

Damping effect of an unsaturated-saturated system on tempospatialvariations of pressurehead and specificflux was investigated. The variance and covariance of both pressure head and specific flux in such a system due to a white noise infiltration were obtained by solving the moment equations of water flow in the system and verified with Monte Carlo simulations. It was found that both the pressure head and specific flux in this case are temporally non-stationary. The variance is zero at early time due to a deterministic initial condition used, then increases with time, and approaches anasymptotic limit at late time.Both pressure head and specific flux arealso non-stationary in space since the variance decreases from source to sink. The unsaturated-saturated systembehavesasa noise filterand it damps both the pressure head and specific flux, i.e., reduces their variations and enhances their correlation. The effect is stronger in upper unsaturated zone than in lower unsaturated zone and saturated zone. As a noise filter, the unsaturated-saturated system is mainly a low pass filter, filtering out the high frequency components in the time series of hydrological variables. The damping effect is much stronger in the saturated zone than in the saturated zone.

Introduction of damage in an elasto-plastic model for unsaturated geo-materials

International Nuclear Information System (INIS)

Le Pense, S.; Pouya, A.; Gatmiri, B.

2012-01-01

Document available in extended abstract form only. During the excavation of nuclear waste repository galleries, the surrounding soil is suspected to undergo structural changes as well as modification of its stress state. The desaturation due to ventilation of galleries during this stage makes it necessary to consider the unsaturated state of the host geo-material. The decompression occurring after the excavation leads to a modification of the stress state. The purpose of our work is to develop a mechanical model to simulate the non-linear stress-strain behaviour of geo-materials which will have to contain radioactivity of nuclear waste for a very long time. Two irreversible phenomena can explain the non-linear behaviour of geo-materials. Plasticity leads to irrecoverable strains. Damage, linked to the appearance and extension of microcracks, results in a deterioration of elastic and hydraulic properties. We will present here the bases of a new model coupling damage and plasticity for the stress-strain behaviour of unsaturated geo-materials. This model should be thermodynamically consistent and use only a reasonable number of parameters. Based on the work of Houlsby, (Houlsby 1997), we choose to use as constitutive variables for unsaturated soils Bishop's stress and suction. This choice as the advantage to allow for continuity at the transition between saturated and unsaturated states. Damage is taken into account by defining a damaged constitutive stress, which is similar to the effective stress principle defined by Kachanov (Kachanov 1958). A simple damage criterion is proposed and an associative flow rule is assumed. We choose to follow the principle of strain equivalence defined by Lemaitre (Lemaitre 1996). This leads to the following elasticity law giving the damaged constitutive stress as a function of elastic strain. If non-linear elasticity is considered, a pressure-dependent bulk modulus and a constant shear modulus can be chosen in order to fit

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

OpenAIRE

Tourchi, Saeed; Hamidi, Amir

2015-01-01

A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existing model for saturated clays originally proposed by the authors. The saturated clays model was formulated in the framework of critical state soil mechanics and modified Cam-clay model. The existing model has been generalized to simulate the experimentally observed behavior of unsaturated clays by introducing Bishop's stress and suction as independent stress parameters and modifying the hardening rul...

The effect of ultralow temperature on olefin cation formation by ionic fragmentation in the radiolysis of 2,3-dimethylbutane

International Nuclear Information System (INIS)

Miyazaki, Tetsuo

1991-01-01

The formation of olefin cations in the radiolysis of 2,3-dimethylbutane (DMB) was studied by ESR at 4.2 and 77 K. When a DMB-SF 6 mixture is γ-irradiated at 77 K, tetramethylethylene (TME) cations are formed remarkably. The formation of the TME cations, however, is suppressed at 4.2 K. When the DMB-SF 6 mixture is γ-irradiated at 4.2 K and then warmed to 77 K, TME cations are formed by thermal annealing. The TME cations are not formed by a charge transfer to olefinic impurities or olefinic products in radiolysis, but by H 2 elimination from parent DMB cations in the ground state. The remarkable formation of olefin cations at 77 K corresponds to the large yields of unsaturated dimers in the radiolysis of DMB at 77 K. The suppression of olefin cation formation at 4.2 K corresponds to the low yields of unsaturated dimers in the radiolysis of DMB at 4.2 K. (author)

Structural Analysis of Unsaturated Glycosphingolipids Using Shotgun Ozone-Induced Dissociation Mass Spectrometry

Science.gov (United States)

Barrientos, Rodell C.; Vu, Ngoc; Zhang, Qibin

2017-08-01

Glycosphingolipids are essential biomolecules widely distributed across biological kingdoms yet remain relatively underexplored owing to both compositional and structural complexity. While the glycan head group has been the subject of most studies, there is paucity of reports on the lipid moiety, particularly the location of unsaturation. In this paper, ozone-induced dissociation mass spectrometry (OzID-MS) implemented in a traveling wave-based quadrupole time-of-flight (Q-ToF) mass spectrometer was applied to study unsaturated glycosphingolipids using shotgun approach. Resulting high resolution mass spectra facilitated the unambiguous identification of diagnostic OzID product ions. Using [M+Na]+ adducts of authentic standards, we observed that the long chain base and fatty acyl unsaturation had distinct reactivity with ozone. The reactivity of unsaturation in the fatty acyl chain was about 8-fold higher than that in the long chain base, which enables their straightforward differentiation. Influence of the head group, fatty acyl hydroxylation, and length of fatty acyl chain on the oxidative cleavage of double bonds was also observed. Application of this technique to bovine brain galactocerebrosides revealed co-isolated isobaric and regioisomeric species, which otherwise would be incompletely identified using contemporary collision-induced dissociation (CID) alone. These results highlight the potential of OzID-MS in glycosphingolipids research, which not only provides complementary structural information to existing CID technique but also facilitates de novo structural determination of these complex biomolecules. [Figure not available: see fulltext.

Estimate of dispersion in an unsaturated aquifer

Science.gov (United States)

Stephenson, D.; De Jesus, A. S. M.

1985-10-01

The Nuclear Development Corporation of South Africa (Pty) Ltd. (NUCOR) is constructing a low-level radioactive waste disposal site near Springbok in Namaqualand, an arid region to the west of South Africa. A groundwater model was developed which required site-specific data and this work describes procedures developed to assess the dispersivity of the soil in the vicinity of the proposed site. Preliminary laboratory tests, carried out using a sodium chloride solution, indicated the order of magnitude of the dispersivity for saturated soil at various levels. This enabled site tests to be designed. The site tests were done by injecting a pulse of scandium-46 into a hole and monitoring the displacement of the radioactive cloud as it moved down under gravity and spread laterally. A mathematical model was developed to predict the behaviour of the cloud and calibration of the model yielded vertical and horizontal dispersivities. The dispersion of radioactivity at the cloud front was assumed to occur in unsaturated medium while the continuously injected water behind the radioactivity was assumed to disperse in a saturated medium. Thus monitoring the concentration of both yielded approximate values for the effective dispersivities in unsaturated and saturated media.

Saturated and unsaturated salt transport in peat from a constructed fen

Science.gov (United States)

Simhayov, Reuven B.; Weber, Tobias K. D.; Price, Jonathan S.

2018-02-01

The underlying processes governing solute transport in peat from an experimentally constructed fen peatland were analyzed by performing saturated and unsaturated solute breakthrough experiments using Na+ and Cl- as reactive and non-reactive solutes, respectively. We tested the performance of three solute transport models, including the classical equilibrium convection-dispersion equation (CDE), a chemical non-equilibrium one-site adsorption model (OSA) and a model to account for physical non-equilibrium, the mobile-immobile (MIM) phases. The selection was motivated by the fact that the applicability of the MIM in peat soils finds a wide consensus. However, results from inverse modeling and a robust statistical evaluation of this peat provide evidence that the measured breakthrough of the conservative tracer, Cl-, could be simulated well using the CDE. Furthermore, the very high Damköhler number (which approaches infinity) suggests instantaneous equilibration between the mobile and immobile phases underscoring the redundancy of the MIM approach for this particular peat. Scanning electron microscope images of the peat show the typical multi-pore size distribution structures have been homogenized sufficiently by decomposition, such that physical non-equilibrium solute transport no longer governs the transport process. This result is corroborated by the fact the soil hydraulic properties were adequately described using a unimodal van Genuchten-Mualem model between saturation and a pressure head of ˜ -1000 cm of water. Hence, MIM was not the most suitable choice, and the long tailing of the Na+ breakthrough curve was caused by chemical non-equilibrium. Successful description was possible using the OSA model. To test our results for the unsaturated case, we conducted an unsaturated steady-state evaporation experiment to drive Na+ and Cl- transport. Using the parameterized transport models from the saturated experiments, we could numerically simulate the unsaturated

Development and validation of mechanical model for saturated/unsaturated bentonite buffer

International Nuclear Information System (INIS)

Yamamoto, S.; Komine, H.; Kato, S.

2010-01-01

Document available in extended abstract form only. Development and validation of mechanical models for bentonite buffer and backfill materials are one of important subjects to appropriately evaluate long term behaviour or condition of the EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one of extensions of the modified Cam-Clay model for unsaturated and expansive soil, has been developed and widely applied to several problems by using the coupled THM code, Code B right. Advantage of the model is that mechanical characteristics of buffer and backfill materials under not only saturated condition but also unsaturated one are taken account as well as swelling characteristics due to wetting. In this study the BBM is compared with already existing experimental data and already developed another model in terms of swelling characteristics of Japanese bentonite Kunigel-V1, and is validated in terms of consolidation characteristics based on newly performed controlled-suction oedometer tests for the Kunigel-V1 bentonite. Komine et al. (2003) have proposed a model (set of equations) for predicting swelling characteristics based on the diffuse double layer concept and the van der Waals force concept etc. They performed a lot of swelling deformation tests of bentonite and sand-bentonite mixture to confirm the applicability of the model. The BBM well agrees with the model proposed by Komine et al. and the experimental data in terms of swelling characteristics. Compression index and swelling index depending on suction are introduced in the BBM. Controlled-suction consolidation tests (oedometer tests) were performed to confirm the applicability of the suction dependent indexes to unsaturated bentonite. Compacted bentonite with initial dry density of 1.0 Mg/m 3 was tested. Constant suction, 80 kPa, 280 kPa and 480 kPa was applied and kept during the consolidation tests. Applicability of the BBM to consolidation and swelling behaviour of saturated and

Continuum model for water movement in an unsaturated fractured rock mass

International Nuclear Information System (INIS)

Peters, R.R.; Klavetter, E.A.

1988-01-01

The movement of fluids in a fractured, porous medium has been the subject of considerable study. This paper presents a continuum model that may be used to evaluate the isothermal movement of water in an unsaturated, fractured, porous medium under slowly changing conditions. This continuum model was developed for use in evaluating the unsaturated zone at the Yucca Mountain site as a potential repository for high-level nuclear waste. Thus its development has been influenced by the conditions thought to be present at Yucca Mountain. A macroscopic approach and a microscopic approach are used to develop a continuum model to evaluate water movement in a fractured rock mass. Both approaches assume that the pressure head in the fractures and the matrix are identical in a plane perpendicular to flow. Both approaches lead to a single-flow equation for a fractured rock mass. The two approaches are used to calculate unsaturated hydrologic properties, i.e., relative permeability and saturation as a function of pressure head, for several types of tuff underlying Yucca Mountain, using the best available hydrologic data for the matrix and the fractures. Rock mass properties calculated by both approaches are similar

Synthesis and study of novel silicon-based unsaturated polymers

Energy Technology Data Exchange (ETDEWEB)

Lin, Jibing [Iowa State Univ., Ames, IA (United States)

1995-06-19

Novel unsaturated polymers have been synthesized and studied as precursors to silicon carbide and third order nonlinear optical materials. X ray structures were obtained. Kinetic and mechanistic studies of the unique thermal isomerization of dimethylenedisilacyclobutane to a carbene were conducted.

Coupled Geomechanical-Flow Assessment of CO2 Leakage through Heterogeneous Caprock during CCS

Directory of Open Access Journals (Sweden)

Guan Woo Kim

2018-01-01

Full Text Available The viability of carbon capture sequestration (CCS is dependent on the secure storage of CO2 in subsurface geologic formations. Geomechanical failure of caprock is one of the main reasons of CO2 leakage from the storage formations. Through comprehensive assessment on the petrophysical and geomechanical heterogeneities of caprock, it is possible to predict the risk of unexpected caprock failure. To describe the fracture reactivation, the modified Barton–Bandis model is applied. In order to generate hydro-geomechanically heterogeneous fields, the negative correlation between porosity and Young’s modulus/Poisson’s ratio is applied. In comparison with the homogeneous model, effects of heterogeneity are examined in terms of vertical deformation and the amount of leaked CO2. To compare the effects of heterogeneity, heterogeneous models for both geomechanical and petrophysical properties in coupled simulation are designed. After 10-year injection with petrophysically heterogeneous and geomechanically homogeneous caprock, CO2 leakage is larger than that of the homogeneous model. In contrast, heterogeneity of geomechanical properties is shown to mitigate additional escape of CO2. Vertical displacement of every heterogeneous model is larger than homogeneous model. The model with compressive tectonic stress shows much more stable trapping with heterogeneous caprock, but there is possibility of rapid leakage after homogeneous caprock failure.

Enantioselective desymmetrization of prochiral cyclohexanones by organocatalytic intramolecular Michael additions to α,β-unsaturated esters.

Science.gov (United States)

Gammack Yamagata, Adam D; Datta, Swarup; Jackson, Kelvin E; Stegbauer, Linus; Paton, Robert S; Dixon, Darren J

2015-04-13

A new catalytic asymmetric desymmetrization reaction for the synthesis of enantioenriched derivatives of 2-azabicyclo[3.3.1]nonane, a key motif common to many alkaloids, has been developed. Employing a cyclohexanediamine-derived primary amine organocatalyst, a range of prochiral cyclohexanone derivatives possessing an α,β-unsaturated ester moiety linked to the 4-position afforded the bicyclic products, which possess three stereogenic centers, as single diastereoisomers in high enantioselectivity (83-99% ee) and in good yields (60-90%). Calculations revealed that stepwise C-C bond formation and proton transfer via a chair-shaped transition state dictate the exclusive endo selectivity and enabled the development of a highly enantioselective primary amine catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Preliminary Design of a Calibration Chamber for Evaluating the Stability of Unsaturated Soil Slope

Science.gov (United States)

Hsu, H.-H.

2012-04-01

The unsaturated soil slopes, which have ground water tables and are easily failure caused by heavy rainfalls, are widely distributed in the arid and semi-arid areas. For analyzing the stability of slope, in situ tests are the direct methods to obtain the test site characteristics. The cone penetration test (CPT) is a popular in situ test method. Some of the CPT empirical equations established from calibration chamber tests. The CPT performed in calibration chamber was commonly used clean quartz sand as testing material in the past. The silty sand is observed in many actual slopes. Because silty sand is relatively compressible than quartz sand, it is not suitable to apply the correlations between soil properties and CPT results built from quartz sand to silty sand. The experience on CPT calibration in silty sand has been limited. CPT calibration tests were mostly performed in dry or saturated soils. The condition around cone tip during penetration is assumed to be fully drained or fully undrained, yet it was observed to be partially drained for unsaturated soils. Because of the suction matrix has a great effect on the characteristics of unsaturated soils, they are much sensitive to the water content than saturated soils. The design of an unsaturated calibration chamber is in progress. The air pressure is supplied from the top plate and the pore water pressure is provided through the high air entry value ceramic disks located at the bottom plate of chamber cell. To boost and uniform distribute the unsaturated effect, four perforated burettes are installed onto the ceramic disks and stretch upwards to the midheight of specimen. This paper describes design concepts, illustrates this unsaturated calibration chamber, and presents the preliminary test results.

Carbonate formation within a nickel dimer: synthesis of a coordinatively unsaturated bis(mu-hydroxo) dinickel complex and its reactivity toward carbon dioxide.

Science.gov (United States)

Wikstrom, Jeffrey P; Filatov, Alexander S; Mikhalyova, Elena A; Shatruk, Michael; Foxman, Bruce M; Rybak-Akimova, Elena V

2010-03-14

The tridentate aminopyridine ligand bearing a bulky tert-butyl substituent at the amine nitrogen, tert-butyl-dipicolylamine (tBuDPA), occupies three coordination sites in six-coordinate complexes of nickel(ii), leaving the remaining three sites available for additional ligand binding and activation. New crystallographically characterized complexes include two mononuclear species with 1:1 metal:ligand complexation: a trihydrate solvate (1.3H(2)O) and a monohydrate biacetonitrile solvate (1.H(2)O.2CH(3)CN). Complexation in the presence of sodium hydroxide results in a bis(mu-hydroxo) complex (2), the bridging hydroxide anions of which are labile and become displaced by methoxide anions in methanol solvent, affording bis-methoxo-bridged (4). Nickel(II) centers in 2 are five-coordinate and antiferromagnetically coupled (with J = -31.4(5) cm(-1), H = -2JS(1)S(2), in agreement with Ni-O-Ni angle of 103.7 degrees). Bridging hydroxide or alkoxide anions in coordinatively unsaturated dinuclear nickel(II) complexes with tBuDPA react as active nucleophiles. 2 readily performs carbon dioxide fixation, resulting in the formation of a bis(mu-carbonato) tetrameric complex (3), which features a novel binding geometry in the form of an inverted butterfly-type nickel-carbonate core. Temperature-dependent magnetic measurements of tetranuclear carbonato-bridged revealed relatively weak antiferromagnetic coupling (J(1) = -3.1(2) cm(-1)) between the two nickel centers in the core of the cluster, as well as weak antiferromagnetic pairwise interactions (J(2) = J(3) = -4.54(5) cm(-1)) between central and terminal nickel ions.

Time-lapse gravity data for monitoring and modeling artificial recharge through a thick unsaturated zone

Science.gov (United States)

Kennedy, Jeffrey R.; Ferre, Ty P.A.; Creutzfeldt, Benjamin

2016-01-01

Groundwater-level measurements in monitoring wells or piezometers are the most common, and often the only, hydrologic measurements made at artificial recharge facilities. Measurements of gravity change over time provide an additional source of information about changes in groundwater storage, infiltration, and for model calibration. We demonstrate that for an artificial recharge facility with a deep groundwater table, gravity data are more sensitive to movement of water through the unsaturated zone than are groundwater levels. Groundwater levels have a delayed response to infiltration, change in a similar manner at many potential monitoring locations, and are heavily influenced by high-frequency noise induced by pumping; in contrast, gravity changes start immediately at the onset of infiltration and are sensitive to water in the unsaturated zone. Continuous gravity data can determine infiltration rate, and the estimate is only minimally affected by uncertainty in water-content change. Gravity data are also useful for constraining parameters in a coupled groundwater-unsaturated zone model (Modflow-NWT model with the Unsaturated Zone Flow (UZF) package).

Heterogeneity of uranium host rocks in Zhiluo formation in Dongsheng area and its relation to uranium mineralization

International Nuclear Information System (INIS)

Yi Chao; Zheng Yunlong; Wang Mingtai

2013-01-01

Numbers of uranium deposits have be found in Dongsheng area. The major ore-bearing layer is the sub member of the lower member of the Zhiluo Formation, the heterogeneity of host rocks plays an important role during the process of uranium mineralization. This paper sorted and counted up the data of sand body and the impermeable bed in Dongsheng area to study the heterogeneity characteristic of host rock and its relationship to uranium mineralization in horizontal and vertical directions. The thickness of sand body in Dongsheng area decreases gradually from northwest to southeast. The uranium mineralization is mainly distributed in the place where the thickness of sand body changed from the thick to the thin. Statistics shows that the best uranium mineralization occurred in sand body thickness between 20 m to 40 m and the sand rate over 60% in the eastern part of Dongsheng area. And the best uranium mineralization in the western part occurred in area of sand body thickness between 60 m to 70 m and the sand rate over 70%. In vertical direction, the numbers and the thickness of the impermeable beds have negative relation to sand rate. Moreover, uranium deposits generally exist in the area of less number impermeable bed and small thickness. The uranium mineralization grade decreased with the increase of number and thickness of the impermeable beds. (authors)

MODELING COUPLED PROCESSES OF MULTIPHASE FLOW AND HEAT TRANSFER IN UNSATURATED FRACTURED ROCK

International Nuclear Information System (INIS)

Y. Wu; S. Mukhopadhyay; K. Zhang; G.S. Bodvarsson

2006-01-01

A mountain-scale, thermal-hydrologic (TH) numerical model is developed for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository at Yucca Mountain, Nevada, USA. The TH model, consisting of three-dimensional (3-D) representations of the unsaturated zone, is based on the current repository design, drift layout, and thermal loading scenario under estimated current and future climate conditions. More specifically, the TH model implements the current geological framework and hydrogeological conceptual models, and incorporates the most updated, best-estimated input parameters. This mountain-scale TH model simulates the coupled TH processes related to mountain-scale multiphase fluid flow, and evaluates the impact of radioactive waste heat on the hydrogeological system, including thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. For a better description of the ambient geothermal condition of the unsaturated zone system, the TH model is first calibrated against measured borehole temperature data. The ambient temperature calibration provides the necessary surface and water table boundary as well as initial conditions. Then, the TH model is used to obtain scientific understanding of TH processes in the Yucca Mountain unsaturated zone under the designed schedule of repository thermal load

Comparison of strongly heat-driven flow codes for unsaturated media

International Nuclear Information System (INIS)

Updegraff, C.D.

1989-08-01

Under the sponsorship of the US Nuclear Regulatory Commission, Sandia National Laboratories (SNL) is developing a performance assessment methodology for the analysis of long-term disposal of high-level radioactive waste (HLW) in unsaturated welded tuff. As part of this effort, SNL evaluated existing strongly heat-driven flow computer codes for simulating ground-water flow in unsaturated media. The three codes tested, NORIA, PETROS, and TOUGH, were compared against a suite of problems for which analytical and numerical solutions or experimental results exist. The problems were selected to test the abilities of the codes to simulate situations ranging from simple, uncoupled processes, such as two-phase flow or heat transfer, to fully coupled processes, such as vaporization caused by high temperatures. In general, all three codes were found to be difficult to use because of (1) built-in time stepping criteria, (2) the treatment of boundary conditions, and (3) handling of evaporation/condensation problems. A drawback of the study was that adequate problems related to expected repository conditions were not available in the literature. Nevertheless, the results of this study suggest the need for thorough investigations of the impact of heat on the flow field in the vicinity of an unsaturated HLW repository. Recommendations are to develop a new flow code combining the best features of these three codes and eliminating the worst ones. 19 refs., 49 figs

Dsc cure kinetics of an unsaturated polyester resin using empirical kinetic model

International Nuclear Information System (INIS)

Abdullah, I.

2015-01-01

In this paper, the kinetics of curing of unsaturated polyester resin initiated with benzoyl peroxide was studied. In case of unsaturated polyester (UP) resin, isothermal test alone could not predict correctly the curing time of UP resin. Therefore, isothermal kinetic analysis through isoconventional adjustment was used to correctly predict the curing time and temperature of UP resin. Isothermal kinetic analysis through isoconversional adjustment indicated that 97% of UP resin cures in 33 min at 120 degree C. Curing of UP resin through microwaves was also studied and found that 67% of UP resin cures in 1 min at 120 degree C. The crosslinking reaction of UP resin is so fast at 120 degree C that it becomes impossible to predict correctly the curing time of UP resin using isothermal test and the burial of C=C bonds in microgels makes it impossible to be fully cured by microwaves at 120 degree C. The rheological behaviour of unsaturated polyester resin was also studied to observe the change in viscosity with respect to time and temperature. (author)

Metal-Free Catalytic Enantioselective C–B Bond Formation: (Pinacolato)boron Conjugate Additions to α,β-Unsaturated Ketones, Esters, Weinreb Amides and Aldehydes Promoted by Chiral N-Heterocyclic Carbenes

Science.gov (United States)

Wu, Hao; Radomkit, Suttipol; O’Brien, Jeannette M.; Hoveyda, Amir H.

2012-01-01

The first broadly applicable metal-free enantioselective method for boron conjugate addition (BCA) to α,β-unsaturated carbonyls is presented. The C–B bond forming reactions are promoted in the presence of 2.5–7.5 mol % of a readily accessible C1-symmetric chiral imidazolinium salt, which is converted, in situ, to the catalytically active diastereo- and enantiomerically pure N-heterocyclic carbene (NHC) by the common organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu). In addition to the commercially available bis(pinacolato)diboron [B2(pin)2], and in contrast to reactions with the less sterically demanding achiral NHCs, the presence of MeOH is required for high efficiency. Acyclic and cyclic α,β-unsaturated ketones, as well as acyclic esters, Weinreb amides and aldehydes can serve as suitable substrates; the desired β-boryl carbonyls are isolated in up to 94% yield and >98:2 enantiomer ratio (er). Transformations are often carried out at ambient temperature. In certain cases, such as when the relatively less reactive unsaturated amides are used, elevated temperatures are required (50–66 °C); nonetheless, reactions remain highly enantioselective. The utility of the NHC-catalyzed method is demonstrated through comparison with the alternative Cu-catalyzed protocols; in cases involving a polyfunctional substrate, unique profiles in chemoselectivity are exhibited by the metal-free approach (e.g., conjugate addition vs reaction with an alkyne, allene or aldehyde). PMID:22559866

Determination of Matric Suction and Saturation Degree for Unsaturated Soils, Comparative Study - Numerical Method versus Analytical Method

Science.gov (United States)

Chiorean, Vasile-Florin

2017-10-01

Matric suction is a soil parameter which influences the behaviour of unsaturated soils in both terms of shear strength and permeability. It is a necessary aspect to know the variation of matric suction in unsaturated soil zone for solving geotechnical issues like unsaturated soil slopes stability or bearing capacity for unsaturated foundation ground. Mathematical expression of the dependency between soil moisture content and it’s matric suction (soil water characteristic curve) has a powerful character of nonlinearity. This paper presents two methods to determine the variation of matric suction along the depth included between groundwater level and soil level. First method is an analytical approach to emphasize one direction steady state unsaturated infiltration phenomenon that occurs between the groundwater level and the soil level. There were simulated three different situations in terms of border conditions: precipitations (inflow conditions on ground surface), evaporation (outflow conditions on ground surface), and perfect equilibrium (no flow on ground surface). Numerical method is finite element method used for steady state, two-dimensional, unsaturated infiltration calculus. Regarding boundary conditions there were simulated identical situations as in analytical approach. For both methods, was adopted the equation proposed by van Genuchten-Mualen (1980) for mathematical expression of soil water characteristic curve. Also for the unsaturated soil permeability prediction model was adopted the equation proposed by van Genuchten-Mualen. The fitting parameters of these models were adopted according to RETC 6.02 software in function of soil type. The analyses were performed in both methods for three major soil types: clay, silt and sand. For each soil type were concluded analyses for three situations in terms of border conditions applied on soil surface: inflow, outflow, and no flow. The obtained results are presented in order to highlight the differences

Biophysical studies of cholesterol in unsaturated phospholipid model membranes

Science.gov (United States)

Williams, Justin Adam

Cellular membranes contain a staggering diversity of lipids. The lipids are heterogeneously distributed to create regions, or domains, whose physical properties differ from the bulk membrane and play an essential role in modulating the function of resident proteins. Many basic questions pertaining to the formation of these lateral assemblies remain. This research employs model membranes of well-defined composition to focus on the potential role of polyunsaturated fatty acids (PUFAs) and their interaction with cholesterol (chol) in restructuring the membrane environment. Omega-3 (n-3) PUFAs are the main bioactive components of fish oil, whose consumption alleviates a variety of health problems by a molecular mechanism that is unclear. We hypothesize that the incorporation of PUFAs into membrane lipids and the effect they have on molecular organization may be, in part, responsible. Chol is a major constituent in the plasma membrane of mammals. It determines the arrangement and collective properties of neighboring lipids, driving the formation of domains via differential affinity for different lipids. The molecular organization of 1-[2H31]palmitoyl-2-eicosapentaenoylphosphatidylcholine (PEPC-d31) and 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylcholine (PDPC-d31) in membranes with sphingomyelin (SM) and chol (1:1:1 mol) was compared by solid-state 2H NMR spectroscopy. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are the two major n-3 PUFAs found in fish oil, while PEPC-d31 and PDPC-d31 are phospholipids containing the respective PUFAs at the sn-2 position and a perdeuterated palmitic acid at the sn-1 position. Analysis of spectra recorded as a function of temperature indicates that in both cases, formation of PUFA-rich (less ordered) and SM-rich (more ordered) domains occurred. A surprisingly substantial proportion of PUFA was found to infiltrate the more ordered domain. There was almost twice as much DHA (65%) as EPA (30%). The implication is that n-3

Unsaturated Zone and Saturated Zone Transport Properties (U0100)

Energy Technology Data Exchange (ETDEWEB)

J. Conca

2000-12-20

This Analysis/Model Report (AMR) summarizes transport properties for the lower unsaturated zone hydrogeologic units and the saturated zone at Yucca Mountain and provides a summary of data from the Busted Butte Unsaturated Zone Transport Test (UZTT). The purpose of this report is to summarize the sorption and transport knowledge relevant to flow and transport in the units below Yucca Mountain and to provide backup documentation for the sorption parameters decided upon for each rock type. Because of the complexity of processes such as sorption, and because of the lack of direct data for many conditions that may be relevant for Yucca Mountain, data from systems outside of Yucca Mountain are also included. The data reported in this AMR will be used in Total System Performance Assessment (TSPA) calculations and as general scientific support for various Process Model Reports (PMRs) requiring knowledge of the transport properties of different materials. This report provides, but is not limited to, sorption coefficients and other relevant thermodynamic and transport properties for the radioisotopes of concern, especially neptunium (Np), plutonium (Pu), Uranium (U), technetium (Tc), iodine (I), and selenium (Se). The unsaturated-zone (UZ) transport properties in the vitric Calico Hills (CHv) are discussed, as are colloidal transport data based on the Busted Butte UZTT, the saturated tuff, and alluvium. These values were determined through expert elicitation, direct measurements, and data analysis. The transport parameters include information on interactions of the fractures and matrix. In addition, core matrix permeability data from the Busted Butte UZTT are summarized by both percent alteration and dispersion.

Unsaturated Zone and Saturated Zone Transport Properties (U0100)

International Nuclear Information System (INIS)

Conca, J.

2000-01-01

This Analysis/Model Report (AMR) summarizes transport properties for the lower unsaturated zone hydrogeologic units and the saturated zone at Yucca Mountain and provides a summary of data from the Busted Butte Unsaturated Zone Transport Test (UZTT). The purpose of this report is to summarize the sorption and transport knowledge relevant to flow and transport in the units below Yucca Mountain and to provide backup documentation for the sorption parameters decided upon for each rock type. Because of the complexity of processes such as sorption, and because of the lack of direct data for many conditions that may be relevant for Yucca Mountain, data from systems outside of Yucca Mountain are also included. The data reported in this AMR will be used in Total System Performance Assessment (TSPA) calculations and as general scientific support for various Process Model Reports (PMRs) requiring knowledge of the transport properties of different materials. This report provides, but is not limited to, sorption coefficients and other relevant thermodynamic and transport properties for the radioisotopes of concern, especially neptunium (Np), plutonium (Pu), Uranium (U), technetium (Tc), iodine (I), and selenium (Se). The unsaturated-zone (UZ) transport properties in the vitric Calico Hills (CHv) are discussed, as are colloidal transport data based on the Busted Butte UZTT, the saturated tuff, and alluvium. These values were determined through expert elicitation, direct measurements, and data analysis. The transport parameters include information on interactions of the fractures and matrix. In addition, core matrix permeability data from the Busted Butte UZTT are summarized by both percent alteration and dispersion

The transport and behaviour of isoproturon in unsaturated chalk cores

Science.gov (United States)

Besien, T. J.; Williams, R. J.; Johnson, A. C.

2000-04-01

A batch sorption study, a microcosm degradation study, and two separate column leaching studies were used to investigate the transport and fate of isoproturon in unsaturated chalk. The column leaching studies used undisturbed core material obtained from the field by dry percussion drilling. Each column leaching study used 25 cm long, 10 cm wide unsaturated chalk cores through which a pulse of isoproturon and bromide was eluted. The cores were set-up to simulate conditions in the unsaturated zone of the UK Chalk aquifer by applying a suction of 1 kPa (0.1 m H 2O) to the base of each column, and eluting at a rate corresponding to an average recharge rate through the unsaturated Chalk. A dye tracer indicated that the flow was through the matrix under these conditions. The results from the first column study showed high recovery rates for both isoproturon (73-92%) and bromide (93-96%), and that isoproturon was retarded by a factor of about 1.23 relative to bromide. In the second column study, two of the four columns were eluted with non-sterile groundwater in place of the sterile groundwater used on all other columns, and this study showed high recovery rates for bromide (85-92%) and lower recovery rates for isoproturon (66-79% — sterile groundwater, 48-61% — non-sterile groundwater). The enhanced degradation in the columns eluted with non-sterile groundwater indicated that groundwater microorganisms had increased the degradation rate within these columns. Overall, the reduced isoproturon recovery in the second column study was attributed to increased microbial degradation as a result of the longer study duration (162 vs. 105 days). The breakthrough curves (BTCs) for bromide had a characteristic convection-dispersion shape and were accurately simulated with the minimum of calibration using a simple convection-dispersion model (LEACHP). However, the isoproturon BTCs had an unusual shape and could not be accurately simulated.

Pore-water extraction from unsaturated tuff by triaxial and one-dimensional compression methods, Nevada Test Site, Nevada

International Nuclear Information System (INIS)

Mower, T.E.; Higgins, J.D.; Yang, In C.; Peters, C.A.

1994-01-01

The hydrologic system in the unsaturated tuff at Yucca Mountain, Nevada, is being evaluated for the US Department of Energy by the Yucca Mountain Project Branch of the US Geological Survey as a potential site for a high-level radioactive-waste repository. Part of this investigation includes a hydrochemical study that is being made to assess characteristics of the hydrologic system such as: traveltime, direction of flow, recharge and source relations, and types and magnitudes of chemical reactions in the unsaturated tuff. In addition, this hydrochemical information will be used in the study of the dispersive and corrosive effects of unsaturated-zone water on the radioactive-waste storage canisters. This report describes the design and validation of laboratory experimental procedures for extracting representative samples of uncontaminated pore water from welded and nonwelded, unsaturated tuffs from the Nevada Test Site

Conceptual Model and Numerical Approaches for Unsaturated Zone Flow and Transport

International Nuclear Information System (INIS)

H.H. Liu

2004-01-01

The purpose of this model report is to document the conceptual and numerical models used for modeling unsaturated zone (UZ) fluid (water and air) flow and solute transport processes. This work was planned in ''Technical Work Plan for: Unsaturated Zone Flow Model and Analysis Report Integration'' (BSC 2004 [DIRS 169654], Sections 1.2.5, 2.1.1, 2.1.2 and 2.2.1). The conceptual and numerical modeling approaches described in this report are mainly used for models of UZ flow and transport in fractured, unsaturated rock under ambient conditions. Developments of these models are documented in the following model reports: (1) UZ Flow Model and Submodels; (2) Radionuclide Transport Models under Ambient Conditions. Conceptual models for flow and transport in unsaturated, fractured media are discussed in terms of their applicability to the UZ at Yucca Mountain. The rationale for selecting the conceptual models used for modeling of UZ flow and transport is documented. Numerical approaches for incorporating these conceptual models are evaluated in terms of their representation of the selected conceptual models and computational efficiency; and the rationales for selecting the numerical approaches used for modeling of UZ flow and transport are discussed. This report also documents activities to validate the active fracture model (AFM) based on experimental observations and theoretical developments. The AFM is a conceptual model that describes the fracture-matrix interaction in the UZ of Yucca Mountain. These validation activities are documented in Section 7 of this report regarding use of an independent line of evidence to provide additional confidence in the use of the AFM in the UZ models. The AFM has been used in UZ flow and transport models under both ambient and thermally disturbed conditions. Developments of these models are documented

Modification of unsaturated polyester resins using nano-size core ...

African Journals Online (AJOL)

Modification of unsaturated polyester resins using nano-size core-shell particles. MO Munyati, PA Lovell. Abstract. No Abstract Available Journal of Science and Technology Special Edition 2004: 24-31. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

Method of polymerizing ethylenically unsaturated materials by irradiation and composition for use therein

International Nuclear Information System (INIS)

Nemcek, J.; Heap, N.

1976-01-01

This patent concerns photopolymerizable compositions consisting essentially of at least one polymerizable ethylenically unsaturated material and a photosensitive catalyst comprising (a) from 0.5 to 5 percent based on the ethylenically unsaturated material of at least one photosensitizer having the structure Ph(CO)C 2 A(CO)Ph, where Ph is phenyl, halogen-substituted phenyl, phenylene or halogen-substituted phenylene and A is a cyclic hydrocarbyl group, a halogen-substituted cyclic hydrocarbyl group, or a group of the formula X(NR)COCONRY, where X and Y each is hydrogen, a hydrocarbyl, or a halogen-substituted hydrocarbyl group, and (b) from 1 to 5 percent by weight based on the ethylenically unsaturated material of a reducing agent capable of reducing the photosensitizer when the photosensitizer is in an excited state. Also described is a process of preparing polymeric materials by irradiating the foregoing polymerizable composition at a wavelength capable of exciting the photosensitizer to an excited state

Unsaturated compounds induce up-regulation of CD86 on dendritic cells in the in vitro sensitization assay LCSA.

Science.gov (United States)

Frohwein, Thomas Armin; Sonnenburg, Anna; Zuberbier, Torsten; Stahlmann, Ralf; Schreiner, Maximilian

2016-04-01

Unsaturated compounds are known to cause false-positive reactions in the local lymph node assay (LLNA) but not in the guinea pig maximization test. We have tested a panel of substances (succinic acid, undecylenic acid, 1-octyn-3-ol, fumaric acid, maleic acid, linoleic acid, oleic acid, alpha-linolenic acid, squalene, and arachidonic acid) in the loose-fit coculture-based sensitization assay (LCSA) to evaluate whether unspecific activation of dendritic cells is a confounder for sensitization testing in vitro. Eight out of 10 tested substances caused significant up-regulation of CD86 on dendritic cells cocultured with keratinocytes and would have been classified as sensitizers; only succinic acid was tested negative, and squalene had to be excluded from data analysis due to poor solubility in cell culture medium. Based on human data, only undecylenic acid can be considered a true sensitizer. The true sensitizing potential of 1-octyn-3-ol is uncertain. Fumaric acid and its isomer maleic acid are not known as sensitizers, but their esters are contact allergens. A group of 18- to 20-carbon chain unsaturated fatty acids (linoleic acid, oleic acid, alpha-linolenic acid, and arachidonic acid) elicited the strongest reaction in vitro. This is possibly due to the formation of pro-inflammatory lipid mediators in the cell culture causing nonspecific activation of dendritic cells. In conclusion, both the LLNA and the LCSA seem to provide false-positive results for unsaturated fatty acids. The inclusion of T cells in dendritic cell-based in vitro sensitization assays may help to eliminate false-positive results due to nonspecific dendritic cell activation. This would lead to more accurate prediction of sensitizers, which is paramount for consumer health protection and occupational safety.

Ammonia gas transport and reactions in unsaturated sediments: Implications for use as an amendment to immobilize inorganic contaminants

International Nuclear Information System (INIS)

Zhong, L.; Szecsody, J.E.; Truex, M.J.; Williams, M.D.; Liu, Y.

2015-01-01

Highlights: • Ammonia transport can be predicted from gas movement and equilibrium partitioning. • Ammonia diffusion rate in unsaturated sediment is a function of water contents. • High pH induced by ammonia causes mineral dissolution and sequential precipitation. • Ammonia treatment effectively immobilized uranium from contaminated sediments. - Abstract: Use of gas-phase amendments for in situ remediation of inorganic contaminants in unsaturated sediments of the vadose zone may be advantageous, but there has been limited development and testing of gas remediation technologies. Treatment with ammonia gas has a potential for use in treating inorganic contaminants (such as uranium) because it induces a high pore-water pH, causing mineral dissolution and subsequent formation of stable precipitates that decrease the mobility of some contaminants. For field application of this treatment, further knowledge of ammonia transport in porous media and the geochemical reactions induced by ammonia treatment is needed. Laboratory studies were conducted to support calculations needed for field treatment design, to quantify advective and diffusive ammonia transport in unsaturated sediments, to evaluate inter-phase (gas/sediment/pore water) reactions, and to study reaction-induced pore-water chemistry changes as a function of ammonia delivery conditions, such as flow rate, gas concentration, and water content. Uranium-contaminated sediment was treated with ammonia gas to demonstrate U immobilization. Ammonia gas quickly partitions into sediment pore water and increases the pH up to 13.2. Injected ammonia gas advection front movement can be reasonably predicted by gas flow rate and equilibrium partitioning. The ammonia gas diffusion rate is a function of the water content in the sediment. Sodium, aluminum, and silica pore-water concentrations increase upon exposure to ammonia and then decline as aluminosilicates precipitate when the pH declines due to buffering. Up to 85% of

IgG particle formation during filling pump operation: a case study of heterogeneous nucleation on stainless steel nanoparticles.

Science.gov (United States)

Tyagi, Anil K; Randolph, Theodore W; Dong, Aichun; Maloney, Kevin M; Hitscherich, Carl; Carpenter, John F

2009-01-01

This study investigated factors associated with vial filling with a positive displacement piston pump leading to formation of protein particles in a formulation of an IgG. We hypothesized that nanoparticles shed from the pump's solution-contact surfaces nucleated protein aggregation and particle formation. Vials of IgG formulation filled at a clinical manufacturing site contained a few visible particles and about 100,000 particles (1.5-3 microm) per mL. In laboratory studies with the same model (National Instruments FUS-10) of pump, pumping of 20 mg/mL IgG formulation resulted in about 300,000 particles (1.5-3 microm) per mL. Pumping of protein-free formulation resulted in 13,000 particles (1.5-15 microm) per mL. More than 99% of the particles were 0.25-0.95 microm in size. Mixing of protein-free pumped solution with an equal volume of 40 mg/mL IgG resulted in 300,000 particles (1.5-15 microm) per mL. Also, mixing IgG formulation with 30,000/mL stainless steel nanoparticles resulted in formation of 30,000 protein microparticles (1.5-15 microm) per mL. Infrared spectroscopy showed that secondary structure of IgG in microparticles formed by pumping or mixing with steel nanoparticles was minimally perturbed. Our results document that nanoparticles of foreign materials shed by pumps can serve as heterogeneous nuclei for formation of protein microparticles. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

Review of Upscaling Methods for Describing Unsaturated Flow

Energy Technology Data Exchange (ETDEWEB)

Wood, Brian D.

2000-09-26

Representing samll-scale features can be a challenge when one wants to model unsaturated flow in large domains. In this report, the various upscaling techniques are reviewed. The following upscaling methods have been identified from the literature: stochastic methods, renormalization methods, volume averaging and homogenization methods. In addition, a final technique, full resolution numerical modeling, is also discussed.

Numerical convergence improvements for porflow unsaturated flow simulations

Energy Technology Data Exchange (ETDEWEB)

Flach, Greg [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-08-14

Section 3.6 of SRNL (2016) discusses various PORFLOW code improvements to increase modeling efficiency, in preparation for the next E-Area Performance Assessment (WSRC 2008) revision. This memorandum documents interaction with Analytic & Computational Research, Inc. (http://www.acricfd.com/default.htm) to improve numerical convergence efficiency using PORFLOW version 6.42 for unsaturated flow simulations.

Role of the unsaturated zone in radioactive and hazardous waste disposal

International Nuclear Information System (INIS)

Mercer, J.W.; Marine, I.W.; Rao, P.S.C.

1983-01-01

The problems of hazardous and low-level radioactive waste disposal caused by the physical and chemical processes active in the unsaturated zone are explored in this book. The focus is on the use of laboratory analyses, field observations, and numerical and analytical calculations to create a clear picture of both problems and potential solutions. Topics include policy modeling, statistical techniques, liners, and field applications. Contents include: Modeling of Moisture Movement through Layered Trench Covers; Role of Partially Saturated Soil in Liner Design for Hazardous Waste Disposal Sites; Field Experiments to Determine Saturated Hydraulic Conductivity in the Vadose Zone; Role of Desaturation on Transport through Fractured Rock; Nuclear Waste Isolation in the Unsaturated Zone of Arid Regions

The measurement of unsaturated hydraulic conductivity from one-step outflow method

International Nuclear Information System (INIS)

Lee, S. H.; Hwang, J. H.; Lee, J. M.; Kim, C. R.

2003-01-01

One of the most important parts in constructing radioactive waste repository may be its safety aspect. The fundamental function of the repository is to isolate completely and forever the radioactive wastes disposed of in it. However, since either normally or abnormally nuclides are to be released from the repository with a certain causes. The hydraulic conductivity is related to transportation of nuclide in soil. However, hydraulic characteristics research in unsaturated soil is not enough at present time. A fast and easy procedure for estimating unsaturated flow parameters is presented. The estimation is based on direct measurement of the retention characteristics combined with inverse estimation of the hydraulic conductivity characteristics from one-step outflow experiment

Advective and diffusive contributions to reactive gas transport during pyrite oxidation in the unsaturated zone

DEFF Research Database (Denmark)

Binning, Philip John; Postma, Diederik Jan; Russel, T.F.

2007-01-01

Pyrite oxidation in unsaturated mine waste rock dumps and soils is limited by the supply of oxygen from the atmosphere. In models, oxygen transport through the subsurface is often assumed to be driven by diffusion. However, oxygen comprises 23.2% by mass of dry air, and when oxygen is consumed at...... parameters; for example, the time to approach steady state depends exponentially on the distance between the soil surface and the subsurface reactive zone. Copyright 2007 by the American Geophysical Union....... at depth in the unsaturated zone, a pressure gradient is created between the reactive zone and the ground surface, causing a substantial advective air flow into the subsurface. To determine the balance between advective and diffusive transport, a one-dimensional multicomponent unsaturated zone gas...

Effect Of Intraruminal Infussion Of Saturated And Unsaturated Fatty ...

African Journals Online (AJOL)

This study describes the effect of intraruminal infusion of diferent proportions of palmitic (saturated fatty acid) and linolenic (unsaturated fatty acid) on rumen degradability of organic matter fraction of Pennisetium purpureum, total volatile fatty acid and total methane productions in West African Dwarf sheep. Five combination ...

NaturAnalogs for the Unsaturated Zone

Energy Technology Data Exchange (ETDEWEB)

A. Simmons; A. Unger; M. Murrell

2000-03-08

The purpose of this Analysis/Model Report (AMR) is to document natural and anthropogenic (human-induced) analog sites and processes that are applicable to flow and transport processes expected to occur at the potential Yucca Mountain repository in order to build increased confidence in modeling processes of Unsaturated Zone (UZ) flow and transport. This AMR was prepared in accordance with ''AMR Development Plan for U0135, Natural Analogs for the UZ'' (CRWMS 1999a). Knowledge from analog sites and processes is used as corroborating information to test and build confidence in flow and transport models of Yucca Mountain, Nevada. This AMR supports the Unsaturated Zone (UZ) Flow and Transport Process Model Report (PMR) and the Yucca Mountain Site Description. The objectives of this AMR are to test and build confidence in the representation of UZ processes in numerical models utilized in the UZ Flow and Transport Model. This is accomplished by: (1) applying data from Boxy Canyon, Idaho in simulations of UZ flow using the same methodologies incorporated in the Yucca Mountain UZ Flow and Transport Model to assess the fracture-matrix interaction conceptual model; (2) Providing a preliminary basis for analysis of radionuclide transport at Pena Blanca, Mexico as an analog of radionuclide transport at Yucca Mountain; and (3) Synthesizing existing information from natural analog studies to provide corroborating evidence for representation of ambient and thermally coupled UZ flow and transport processes in the UZ Model.

Natural Analogs for the Unsaturated Zone

International Nuclear Information System (INIS)

Simmons, A.; Unger, A.; Murrell, M.

2000-01-01

The purpose of this Analysis/Model Report (AMR) is to document natural and anthropogenic (human-induced) analog sites and processes that are applicable to flow and transport processes expected to occur at the potential Yucca Mountain repository in order to build increased confidence in modeling processes of Unsaturated Zone (UZ) flow and transport. This AMR was prepared in accordance with ''AMR Development Plan for U0135, Natural Analogs for the UZ'' (CRWMS 1999a). Knowledge from analog sites and processes is used as corroborating information to test and build confidence in flow and transport models of Yucca Mountain, Nevada. This AMR supports the Unsaturated Zone (UZ) Flow and Transport Process Model Report (PMR) and the Yucca Mountain Site Description. The objectives of this AMR are to test and build confidence in the representation of UZ processes in numerical models utilized in the UZ Flow and Transport Model. This is accomplished by: (1) applying data from Boxy Canyon, Idaho in simulations of UZ flow using the same methodologies incorporated in the Yucca Mountain UZ Flow and Transport Model to assess the fracture-matrix interaction conceptual model; (2) Providing a preliminary basis for analysis of radionuclide transport at Pena Blanca, Mexico as an analog of radionuclide transport at Yucca Mountain; and (3) Synthesizing existing information from natural analog studies to provide corroborating evidence for representation of ambient and thermally coupled UZ flow and transport processes in the UZ Model

Changes of the water isotopic composition in unsaturated soils

International Nuclear Information System (INIS)

Feurdean, Victor; Feurdean, Lucia

2001-01-01

Based on the spatial and temporal variations of the stable isotope content in precipitation - as input in subsurface - and the mixing processes, the deuterium content in the water that moves in unsaturated zones was used to determine the most conducive season to recharge, the mechanisms for infiltration of snow or rain precipitation in humid, semi-arid or arid conditions, the episodic cycles of infiltration water mixing with the already present soil water and water vapor and whether infiltration water is or is not from local precipitation. Oscillations in the isotopic profiles of soil moisture can be used to estimate the following aspects: where piston or diffusive flow is the dominant mechanisms of water infiltration; the average velocities of the water movement in vadose zone; the influence of vegetation cover, soil type and slope exposure on the dynamics of water movement in soil; the conditions required for infiltration such as: the matrix, gravity, pressure and osmotic potentials during drainage in unsaturated soil. (authors)

Unsaturated transport of inorganic cations in undisturbed soil columns

International Nuclear Information System (INIS)

Jardine, P.M.; Jacobs, G.K.

1990-01-01

The unsaturated transport of Sr, Co, and Ca were studied in undisturbed soil columns (14 x 40 cm) of saprolitic shale to evaluate the significance of time dependent mass transfer and multispecies competitive exchange during transport. Observed breakthrough curves (BTCs) for Sr and Co were delayed relative to nonreactive Br BTC indicating that the former tracers were adsorbed by the soil. Effluent concentrations of Sr and Co were modeled with the classical convective dispersive (CD) equation and nonequilibrium mass transfer considerations did not appear necessary. Cation exchange equilibria relationships obtained from both shake batch and miscible displacement methods adequately described the thermodynamic processes which were prevalent during transport. These results suggest that the preferential transport of a reactive tracer is negligible for the realistic unsaturated conditions used in the study, and that the massive saprolite within the soil is a chemically active constituent during transport of reactive solutes. The implications of these findings for modeling in-situ subsurface contaminant transport are discussed. 7 refs., 9 figs

AN ACTIVE FRACTURE MODEL FOR UNSATURATED FLOW AND TRANSPORT

International Nuclear Information System (INIS)

HUI-HAI LIU, GUDMUNDUR S. BODVARSSON AND CHRISTINE DOUGHTY

1999-01-01

Fracture/matrix (F/M) interaction is a key factor affecting flow and transport in unsaturated fractured rocks. In classic continuum approaches (Warren and Root, 1963), it is assumed that flow occurs through all the connected fractures and is uniformly distributed over the entire fracture area, which generally gives a relatively large F/M interaction. However, fractures seem to have limited interaction with the surrounding matrix at Yucca Mountain, Nevada, as suggested by geochemical nonequilibrium between the perched water (resulting mainly from fracture flow) and pore water in the rock matrix. Because of the importance of the F/M interaction and related issues, there is a critical need to develop new approaches to accurately consider the interaction reduction inferred from field data at the Yucca Mountain site. Motivated by this consideration, they have developed an active fracture model based on the hypothesis that not all connected fractures actively conduct water in unsaturated fractured rocks

MILLIMETER WAVE SPECTRUM AND ASTRONOMICAL SEARCH FOR VINYL FORMATE

Energy Technology Data Exchange (ETDEWEB)

Alonso, E. R.; Kolesniková, L.; Cabezas, C.; Alonso, J. L. [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Área de Química-Física, Laboratorios de Espectroscopia y Bioespectroscopia, Parque Científico UVa, Unidad Asociada CSIC, Universidad de Valladolid, E-47011 Valladolid (Spain); Tercero, B.; Cernicharo, J. [Grupo de Astrofísica Molecular, ICMM-CSIC, C/Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco (Spain); Guillemin, J.-C. [Institut des Sciences Chimiques de Rennes, École Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837, F-35708 Rennes Cedex 7 (France)

2016-11-20

Previous detections of methyl and ethyl formate make other small substituted formates potential candidates for observation in the interstellar medium. Among them, vinyl formate is one of the simplest unsaturated carboxylic ester. The aim of this work is to provide direct experimental frequencies of the ground vibrational state of vinyl formate in a large spectral range for astrophysical use. The room-temperature rotational spectrum of vinyl formate has been measured from 80 to 360 GHz and analyzed in terms of Watson’s semirigid rotor Hamiltonian. Two thousand six hundred transitions within J = 3–88 and K {sub a} = 0–28 were assigned to the most stable conformer of vinyl formate and a new set of spectroscopic constants was accurately determined. Spectral features of vinyl formate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of vinyl formate are provided.

Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

Directory of Open Access Journals (Sweden)

T. J. Bohn

2013-10-01

Full Text Available We used a process-based model to examine the role of spatial heterogeneity of surface and sub-surface water on the carbon budget of the wetlands of the West Siberian Lowland over the period 1948–2010. We found that, while surface heterogeneity (fractional saturated area had little overall effect on estimates of the region's carbon fluxes, sub-surface heterogeneity (spatial variations in water table depth played an important role in both the overall magnitude and spatial distribution of estimates of the region's carbon fluxes. In particular, to reproduce the spatial pattern of CH4 emissions recorded by intensive in situ observations across the domain, in which very little CH4 is emitted north of 60° N, it was necessary to (a account for CH4 emissions from unsaturated wetlands and (b use spatially varying methane model parameters that reduced estimated CH4 emissions in the northern (permafrost half of the domain (and/or account for lower CH4 emissions under inundated conditions. Our results suggest that previous estimates of the response of these wetlands to thawing permafrost may have overestimated future increases in methane emissions in the permafrost zone.

Analysis of gaseous-phase stable and radioactive isotopes in the unsaturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Yang, I.C.; Haas, H.H.; Weeks, E.P.; Thorstenson, D.C.

1985-01-01

The Nevada Nuclear Waste Storage Investigations Project of the US Department of Energy provides that agency with data for evaluating volcanic tuff beneath Yucca Mountain, Nevada, to determine its suitability for a potential repository of high-level radioactive waste. Thickness of the unsaturated zone, which consists of fractured, welded and nonwelded tuff, is about 1640 to 2460 feet (500 to 750 meters). One question to be resolved is an estimate of minimum ground-water traveltime from the disturbed zone of the potentail repository to the accessible environment. Another issue is the potential for diffusive or convective gaseous transport of radionuclides from an underground facility in the unsaturated zone to the accessible environment. Gas samples were collected at intervals to a depth of 1200 feet from the unsaturated zone at Yucca Mountain, Nevada. Samples were analyzed for major atmospheric gases; carbon dioxide in the samples was analyzed for carbon-14 activity and for delta 13 C; water vapor in the samples was analyzed for deuterium and oxygen-18. These data could provide insight into the nature of unsaturated zone transport processes. 15 refs., 4 figs., 4 tabs

Waves spontaneously generated by heterogeneity in oscillatory media

Science.gov (United States)

Cui, Xiaohua; Huang, Xiaodong; Hu, Gang

2016-05-01

Wave propagation is an important characteristic for pattern formation and pattern dynamics. To date, various waves in homogeneous media have been investigated extensively and have been understood to a great extent. However, the wave behaviors in heterogeneous media have been studied and understood much less. In this work, we investigate waves that are spontaneously generated in one-dimensional heterogeneous oscillatory media governed by complex Ginzburg-Landau equations; the heterogeneity is modeled by multiple interacting homogeneous media with different system control parameters. Rich behaviors can be observed by varying the control parameters of the systems, whereas the behavior is incomparably simple in the homogeneous cases. These diverse behaviors can be fully understood and physically explained well based on three aspects: dispersion relation curves, driving-response relations, and wave competition rules in homogeneous systems. Possible applications of heterogeneity-generated waves are anticipated.

The synthesis of some unsaturated 4-substituted-g-lactones

Directory of Open Access Journals (Sweden)

SUREN HUSINEC

2000-02-01

Full Text Available The synthesis of conjugated and nonconjugated unsaturated 4-substituted lactones of type 1 and 2 are described. The type 1 lactone was prepared by a two step procedure employing Bredereck's reagent. The type 2 lactone was synthesised by combining the Claisen-Ireland rearrangement and selenolactonisation.

Effect of water content on dispersion of transferred solute in unsaturated porous media

Energy Technology Data Exchange (ETDEWEB)

Latrille, C. [CEA Saclay, DEN/DANS/DPC/SECR/L3MR, 91191 Gif sur Yvette (France)

2013-07-01

Estimating contaminant migration in the context of waste disposal and/or environmental remediation of polluted soils requires a complete understanding of the underlying transport processes. In unsaturated porous media, water content impacts directly on porous solute transfer. Depending on the spatial distribution of water content, the flow pathway is more complex than in water saturated media. Dispersivity is consequently dependent on water content. Non-reactive tracer experiments performed using unsaturated sand columns confirm the dependence of dispersivity with pore velocity; moreover, a power law relationship between dispersivity and water content is evidenced. (authors)

Total synthesis of fluoxetine and duloxetine through an in situ imine formation/borylation/transimination and reduction approach.

Science.gov (United States)

Calow, Adam D J; Fernández, Elena; Whiting, Andrew

2014-08-28

We report efficient, catalytic, asymmetric total syntheses of both (R)-fluoxetine and (S)-duloxetine from α,β-unsaturated aldehydes conducting five sequential one-pot steps (imine formation/copper mediated β-borylation/transimination/reduction/oxidation) followed by the specific ether group formation which deliver the desired products (R)-fluoxetine in 45% yield (96% ee) and (S)-duloxetine in 47% yield (94% ee).

Quantifying the Effects of Biofilm on the Hydraulic Properties of Unsaturated Soils

Science.gov (United States)

Volk, E.; Iden, S.; Furman, A.; Durner, W.; Rosenzweig, R.

2017-12-01

Quantifying the effects of biofilms on hydraulic properties of unsaturated soils is necessary for predicting water and solute flow in soil with extensive microbial presence. This can be relevant to bioremediation processes, soil aquifer treatment and effluent irrigation. Previous works showed a reduction in the hydraulic conductivity and an increase in water content due to the addition of biofilm analogue materials. The objective of this research is to quantify soil hydraulic properties of unsaturated soil (water retention and hydraulic conductivity) using real soil biofilm. In this work, Hamra soil was incubated with Luria Broth (LB) and biofilm-producing bacteria (Pseudomonas Putida F1). Hydraulic conductivity and water retention were measured by the evaporation method, Dewpoint method and a constant head permeameter. Biofilm was quantified using viable counts and the deficit of TOC. The results show that the presence of biofilms increases soil retention in the `dry' range of the curve and reduces the hydraulic conductivity (see figure). This research shows that biofilms may have a non-negligible effect on flow and transport in unsaturated soils. These findings contribute to modeling water flow in biofilm amended soil.

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates.

Science.gov (United States)

Vero, S E; Ibrahim, T G; Creamer, R E; Grant, J; Healy, M G; Henry, T; Kramers, G; Richards, K G; Fenton, O

2014-12-01

The true efficacy of a programme of agricultural mitigation measures within a catchment to improve water quality can be determined only after a certain hydrologic time lag period (subsequent to implementation) has elapsed. As the biophysical response to policy is not synchronous, accurate estimates of total time lag (unsaturated and saturated) become critical to manage the expectations of policy makers. The estimation of the vertical unsaturated zone component of time lag is vital as it indicates early trends (initial breakthrough), bulk (centre of mass) and total (Exit) travel times. Typically, estimation of time lag through the unsaturated zone is poor, due to the lack of site specific soil physical data, or by assuming saturated conditions. Numerical models (e.g. Hydrus 1D) enable estimates of time lag with varied levels of input data. The current study examines the consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates using simulated and actual soil profiles. Results indicated that: greater temporal resolution (from daily to hourly) of meteorological data was more critical as the saturated hydraulic conductivity of the soil decreased; high clay content soils failed to converge reflecting prevalence of lateral component as a contaminant pathway; elucidation of soil hydraulic properties was influenced by the complexity of soil physical data employed (textural menu, ROSETTA, full and partial soil water characteristic curves), which consequently affected time lag ranges; as the importance of the unsaturated zone increases with respect to total travel times the requirements for high complexity/resolution input data become greater. The methodology presented herein demonstrates that decisions made regarding input data and landscape position will have consequences for the estimated range of vertical travel times. Insufficiencies or inaccuracies regarding such input data can therefore mislead policy makers regarding

Estimation of folate binding capacity (unsaturated and total) in normal human serum and in β-thalassaemia

International Nuclear Information System (INIS)

Moulopoulos, S.; Mantzos, J.; Gyftaki, E.; Kesse-Elias, M.; Alevizou-Terzaki, V.; Souli-Tsimili, E.

1978-01-01

A method is described for measuring the total serum folate binding capacity (TBC) after treating the serum with urea at pH5.5, the unsaturated serum folate binding capacity (UBC) being determined without treatment with urea. The method was applied to 50 normal controls and 20 patients with homozygous β-thalassaemia. The results show an increase in folate binding capacity after treating the serum with urea in all cases studied. There is no correlation between serum folic acid level and total or unsaturated folate binding capacity or per cent saturation. The method described is a simple and rapid one for screening the different groups studied for saturated and unsaturated specific folate-binding proteins. (author)

Stereodirection of an α-ketoester at sub-molecular sites on chirally modified Pt(111): Heterogeneous asymmetric catalysis

DEFF Research Database (Denmark)

Demers-Carpentier, V.; Rasmussen, A.M.H.; Goubert, G.

2013-01-01

Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3,3,3-triflu......Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3...

Migrations of 60-Co and 137-Cs in Saturated and unsaturated Soil at Serpong Nuclear Research Center

International Nuclear Information System (INIS)

Lubis, E; Untara

1996-01-01

The migrations of 60-Co and 137-Cs in saturated and unsaturated soil at Serpong Nuclear Research Center was investigated. The objectives of this investigation are to find the geological and hydrological parameters, especially for estimating the migrations of radionuclides in porous media with advection-dispersion equations. The result showed that the porosity (η) and density (ρ ) of saturated soil are 27.6% and 1.35 g/cm3, and in the unsaturated soil are 18.9% and 1.41 g/cm3. The coefficients distributions (Kd) of 60-Co and 137-Cs in saturated and unsaturated soil are 1.6 - 8.9 and 3.2 - 7.7 respectively. The hydrodinamic coefficients (Dx) and dispersivity (αx) of C0-60 in saturated and unsaturated soil are 0.85 cm2/second and 2.4 x 10-3 cm, and for 137-Cs are 0.91 cm2/second and 2.54 x 10E3 cm

A simple method to assess unsaturated zone time lag in the travel time from ground surface to receptor.

Science.gov (United States)

Sousa, Marcelo R; Jones, Jon P; Frind, Emil O; Rudolph, David L

2013-01-01

In contaminant travel from ground surface to groundwater receptors, the time taken in travelling through the unsaturated zone is known as the unsaturated zone time lag. Depending on the situation, this time lag may or may not be significant within the context of the overall problem. A method is presented for assessing the importance of the unsaturated zone in the travel time from source to receptor in terms of estimates of both the absolute and the relative advective times. A choice of different techniques for both unsaturated and saturated travel time estimation is provided. This method may be useful for practitioners to decide whether to incorporate unsaturated processes in conceptual and numerical models and can also be used to roughly estimate the total travel time between points near ground surface and a groundwater receptor. This method was applied to a field site located in a glacial aquifer system in Ontario, Canada. Advective travel times were estimated using techniques with different levels of sophistication. The application of the proposed method indicates that the time lag in the unsaturated zone is significant at this field site and should be taken into account. For this case, sophisticated and simplified techniques lead to similar assessments when the same knowledge of the hydraulic conductivity field is assumed. When there is significant uncertainty regarding the hydraulic conductivity, simplified calculations did not lead to a conclusive decision. Copyright © 2012 Elsevier B.V. All rights reserved.

Transient Point Infiltration In The Unsaturated Zone

Science.gov (United States)

Buecker-Gittel, M.; Mohrlok, U.

The risk assessment of leaking sewer pipes gets more and more important due to urban groundwater management and environmental as well as health safety. This requires the quantification and balancing of transport and transformation processes based on the water flow in the unsaturated zone. The water flow from a single sewer leakage could be described as a point infiltration with time varying hydraulic conditions externally and internally. External variations are caused by the discharge in the sewer pipe as well as the state of the leakage itself. Internal variations are the results of microbiological clogging effects associated with the transformation processes. Technical as well as small scale laboratory experiments were conducted in order to investigate the water transport from an transient point infiltration. From the technical scale experiment there was evidence that the water flow takes place under transient conditions when sewage infiltrates into an unsaturated soil. Whereas the small scale experiments investigated the hydraulics of the water transport and the associated so- lute and particle transport in unsaturated soils in detail. The small scale experiment was a two-dimensional representation of such a point infiltration source where the distributed water transport could be measured by several tensiometers in the soil as well as by a selective measurement of the discharge at the bottom of the experimental setup. Several series of experiments were conducted varying the boundary and initial con- ditions in order to derive the important parameters controlling the infiltration of pure water from the point source. The results showed that there is a significant difference between the infiltration rate in the point source and the discharge rate at the bottom, that could be explained by storage processes due to an outflow resistance at the bottom. This effect is overlayn by a decreasing water content decreases over time correlated with a decreasing infiltration

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

Directory of Open Access Journals (Sweden)

Valerij A. Nikolaev

2016-08-01

Full Text Available Rh(II-сatalyzed reactions of aroyldiazomethanes, diazoketoesters and diazodiketones with α,β-unsaturated δ-aminoesters, in contrast to reactions of diazomalonates and other diazoesters, give rise to the Wolff rearrangement and/or oxidative cleavage of the initially formed N–H-insertion products. These oxidation processes are mediated by Rh(II catalysts possessing perfluorinated ligands. The formation of pyrrolidine structures, characteristic for catalytic reactions of diazoesters, was not observed in these processes at all.

Antiprotozoal Activity of α,β-Unsaturated δ-Lactones: Promising ...

African Journals Online (AJOL)

The parasite resistance and side effects of drugs used to treat protozoal diseases have led to the search for new therapies, both natural and synthetic. Studies have shown that various α,β-unsaturated δ-lactones displayed high antiprotozoal activity and thus are promising compounds for new drug discovery and ...

Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction

DEFF Research Database (Denmark)

Taarning, Esben; Madsen, Robert

2008-01-01

A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes...

ENGINEERING ISSUE: IN SITU BIOREMEDIATION OF CONTAMINATED UNSATURATED SUBSURFACE SOILS

Science.gov (United States)

An emerging technology for the remediation of unsaturated subsurface soils involves the use of microorganisms to degrade contaminants which are present in such soils. Understanding the processes which drive in situ bioremediation, as well as the effectiveness and efficiency of th...

Proton-Transfer Polymerization by N-Heterocyclic Carbenes: Monomer and Catalyst Scopes and Mechanism for Converting Dimethacrylates into Unsaturated Polyesters

KAUST Repository

Hong, Miao

2016-01-18

This contribution presents a full account of experimental and theoretical/computational investigations into the N-heterocyclic carbene (NHC)-catalyzed proton-transfer polymerization (HTP) that converts common dimethacrylates (DMAs) containing no protic groups into unsaturated polyesters. This new HTP proceeds through the step-growth propagation cycles via enamine intermediates, consisting of the proposed conjugate addition–proton transfer–NHC release fundamental steps. This study examines the monomer and catalyst scopes as well as the fundamental steps involved in the overall HTP mechanism. DMAs having six different types of linkages connecting the two methacrylates have been polymerized into the corresponding unsaturated polyesters. The most intriguing unsaturated polyester of the series is that based on the biomass-derived furfuryl dimethacrylate, which showed a unique self-curing ability Four MeO– and Cl–substituted TPT (1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene) derivatives as methanol insertion products, RxTPT(MeO/H) (R = MeO, Cl; x = 2, 3), and two free carbenes (catalysts), OMe2TPT and OMe3TPT, have been synthesized, while OMe2TPT(MeO/H) and OMe2TPT have also been structurally characterized. The structure/reactivity relationship study revealed that OMe2TPT, being both a strong nucleophile and a good leaving group, exhibits the highest HTP activity and also produced the polyester with the highest Mn, while the Cl–substituted TPT derivatives are least active and efficient. Computational studies have provided mechanistic insights into the tail-to-tail dimerization coupling step as a suitable model for the propagation cycle of the HTP. The extensive energy profile was mapped out and the experimentally observed unicity of the TPT-based catalysts was satisfactorily explained with the thermodynamic formation of key spirocyclic species.

Solid waste leach characteristics and contaminant-sediment interactions Volume 2: Contaminant transport under unsaturated moisture contents

International Nuclear Information System (INIS)

Lindenmeier, C.W.; Serne, R.J.; Conca, J.L.

1995-09-01

The objectives of this report and subsequent volumes include describing progress on (1) development and optimization of experimental methods to quantify the release of contaminants from solid wastes and their subsequent interactions with unsaturated sediments and (2) the creation of empirical data that become input parameters to performance assessment (PA) analyses for future Hanford Site disposal units and baseline risk assessments for inactive and existing solid waste disposal units. For this report, efforts focused on developing methodologies to evaluate contaminant transport in Trench 8 (W-5 Burial Ground) sediments under unsaturated (vadose zone) conditions. To accomplish this task, a series of flow-through column tests were run using standard saturated column systems, Wierenga unsaturated column systems (both commercial and modified), and the Unsaturated Flow Apparatus (UFA). The reactants investigated were 85 Sr, 236 U, and 238 U as reactive tracers, and tritium as a non-reactive tracer. Results indicate that for moderately unsaturated conditions (volumetric water contents >50 % of saturation), the Wierenga system performed reasonably well such that long water residence times (50-147 h) were achieved, and reasonably good steady-state flow conditions were maintained. The major drawbacks in using this system for reactive tracer work included (1) the inability to achieve reproducible and constant moisture content below 50% of saturation, (2) the four to six month time required to complete a single test, and (3) the propensity for mechanical failure resulting from laboratory power outages during the prolonged testing period

Characterization of unsaturated zone hydrogeologic units using matrix properties and depositional history in a complex volcanic environment

Science.gov (United States)

Flint, Lorraine E.; Buesch, David C.; Flint, Alan L.

2006-01-01

Characterization of the physical and unsaturated hydrologic properties of subsurface materials is necessary to calculate flow and transport for land use practices and to evaluate subsurface processes such as perched water or lateral diversion of water, which are influenced by features such as faults, fractures, and abrupt changes in lithology. Input for numerical flow models typically includes parameters that describe hydrologic properties and the initial and boundary conditions for all materials in the unsaturated zone, such as bulk density, porosity, and particle density, saturated hydraulic conductivity, moisture-retention characteristics, and field water content. We describe an approach for systematically evaluating the site features that contribute to water flow, using physical and hydraulic data collected at the laboratory scale, to provide a representative set of physical and hydraulic parameters for numerically calculating flow of water through the materials at a site. An example case study from analyses done for the heterogeneous, layered, volcanic rocks at Yucca Mountain is presented, but the general approach for parameterization could be applied at any site where depositional processes follow deterministic patterns. Hydrogeologic units at this site were defined using (i) a database developed from 5320 rock samples collected from the coring of 23 shallow (deep (500–1000 m) boreholes, (ii) lithostratigraphic boundaries and corresponding relations to porosity, (iii) transition zones with pronounced changes in properties over short vertical distances, (iv) characterization of the influence of mineral alteration on hydrologic properties such as permeability and moisture-retention characteristics, and (v) a statistical analysis to evaluate where boundaries should be adjusted to minimize the variance within layers. Model parameters developed in this study, and the relation of flow properties to porosity, can be used to produce detailed and accurate

Stereoselective synthesis of unsaturated α-amino acids.

Science.gov (United States)

Fanelli, Roberto; Jeanne-Julien, Louis; René, Adeline; Martinez, Jean; Cavelier, Florine

2015-06-01

Stereoselective synthesis of unsaturated α-amino acids was performed by asymmetric alkylation. Two methods were investigated and their enantiomeric excess measured and compared. The first route consisted of an enantioselective approach induced by the Corey-Lygo catalyst under chiral phase transfer conditions while the second one involved the hydroxypinanone chiral auxiliary, both implicating Schiff bases as substrate. In all cases, the use of a prochiral Schiff base gave higher enantiomeric excess and yield in the final desired amino acid.

Review of Upscaling Methods for Describing Unsaturated Flow

Energy Technology Data Exchange (ETDEWEB)

BD Wood

2000-09-26

The representation of small-scale features can be a challenge when attempting to model unsaturated flow in large domains. Upscaling methods offer the possibility of reducing the amount of resolution required to adequately simulate such a problem. In this report, the various upscaling techniques that are discussed in the literature are reviewed. The following upscaling methods have been identified from the literature: (1) stochastic methods, (2) renormalization methods, and (3) volume averaging and homogenization methods; in addition, a final technique, full resolution numerical modeling, is also discussed. Each of these techniques has its advantages and disadvantages. The trade-off is a reduction in accuracy in favor of a method that is easier to employ. For practical applications, the most reasonable approach appears to be one in which any of the upscaling methods identified above maybe suitable for upscaling in regions where the variations in the parameter fields are small. For regions where the subsurface structure is more complex, only the homogenization and volume averaging methods are probably suitable. With the continual increases in computational capacity, fill-resolution numerical modeling may in many instances provide a tractable means of solving the flow problem in unsaturated systems.

Measurement of unsaturated hydraulic properties and evaluation of property-transfer models for deep sedimentary interbeds, Idaho National Laboratory, Idaho

Science.gov (United States)

Perkins, Kimberlie; Johnson, Brittany D.; Mirus, Benjamin B.

2014-01-01

Operations at the Idaho National Laboratory (INL) have the potential to contaminate the underlying Eastern Snake River Plain (ESRP) aquifer. Methods to quantitatively characterize unsaturated flow and recharge to the ESRP aquifer are needed to inform water-resources management decisions at INL. In particular, hydraulic properties are needed to parameterize distributed hydrologic models of unsaturated flow and transport at INL, but these properties are often difficult and costly to obtain for large areas. The unsaturated zone overlying the ESRP aquifer consists of alternating sequences of thick fractured volcanic rocks that can rapidly transmit water flow and thinner sedimentary interbeds that transmit water much more slowly. Consequently, the sedimentary interbeds are of considerable interest because they primarily restrict the vertical movement of water through the unsaturated zone. Previous efforts by the U.S. Geological Survey (USGS) have included extensive laboratory characterization of the sedimentary interbeds and regression analyses to develop property-transfer models, which relate readily available physical properties of the sedimentary interbeds (bulk density, median particle diameter, and uniformity coefficient) to water retention and unsaturated hydraulic conductivity curves.

Effects of low-level radioactive-waste disposal on water chemistry in the unsaturated zone at a site near Sheffield, Illinois, 1982-84

Science.gov (United States)

Peters, C.A.; Striegl, Robert G.; Mills, P.C.; Healy, R.W.

1992-01-01

A 1982-84 field study defined the chemistry of water collected from the unsaturated zone at a low-level radioactive-waste disposal site near Sheffield, Bureau County, Illinois. Chemical data were evaluated to determine the principal naturally occurring geochemical reactions in the unsaturated zone and to evaluate waste-induced effects on pore-water chemistry. Samples of precipitation, unsaturated-zone pore water, and saturated-zone water were analyzed for specific conductance, pH, alkalinity, major cations and anions, dissolved organic carbon, gross alpha and beta radiation, and tritium. Little change in concentration of most major constituents in the unsaturated-zone water was observed with respect to depth or distance from disposal trenches. Tritium and dissolved organic carbon concentrations were, however, dependent on proximity to trenches. The primary reactions, both on- site and off-site, were carbonate and clay dissolution, cation exchange, and the oxidation of pyrite. The major difference between on-site and off-site inorganic water chemistry resulted from the removal of the Roxana Silt and the Radnor Till Member of the Glasford Formation from on-site. Off-site, the Roxana Silt contributed substantial quantities of sodium to solution from montmorillonite dissolution and associated cation-exchange reactions. The Radnor Till Member provided exchange surfaces for magnesium. Precipitation at the site had an ionic composition of calcium zinc sulfate and an average pH of 4.6. Within 0.3 meter of the land surface, infiltrating rain water or snowmelt changed to an ionic canposition of calcium sulfate off-site and calcium bicarbonate on-site and had an average pH of 7.9; below that depth, pH averaged 7.5 and the ionic composition generally was calcium magnesium bicarbonate. Alkalinity and specific conductance differed primarily according to composition of geologic materials. Tritium concentrations ranged from 0.2 (detection limit) to 1,380 nanocuries per liter. The

{alpha},{beta}-Unsaturated Fischer carbene complexes as chemical multitalents

Energy Technology Data Exchange (ETDEWEB)

Meijere, A. de [Institut fuer Organische Chemie der George-August-Universitaet Goettingen (Germany)

1995-12-31

The well established reaction of {alpha},{beta}-unsaturated Fischer carbenechromium complexes 6(R{sup 1} = H) with alkynes normally proceeds with carbonyl insertion to yield 4-alkoxyphenols 9. Led by the incidental formation of a cyclopentadiene 3 from certain {beta}-aminosubstituted complexes 6(X = NR{sub 2}{sup 3}, R{sup 1} = cPr) the authors have studied the influences of the nature of substituents (R{sup 1}, X on 6; R{sub L}, R{sub S} in the alkyne; R{sup 3} in the amino group), solvents, and temperature on the outcome of the reaction. Imino substitution on complexes 6 leads to 2H-pyrroles 1, a free primary amino group (X = NH{sub 2}) to pyridines 5, and bulky substituents R{sup 1} to cyclopenta[b]pyrans 8 with double insertion of an alkyne. Eventually, appropriate conditions have been developed which permit to selectively prepare either 3-alkoxy-5-(dialkylamino)cyclopentadienes 3 (as synthetic equivalents of cyclopentenones 4), 5-(dialkylaminomethylene)cyclopent-2-enones 7, 3-alkoxy-2-(1{prime}-morpholino-1{prime}-alkenyl)cyclopent-2-enones 10, and 2-acyl-3-(dialkylamino)cyclopent-2-enones 11 from easily accessible carbene complexes 6 (X = NR{sub 2}{sup 3}) in high yields. Mechanistic aspects and implications of these novel transformations will be discussed.

Heterogeneous-catalytic redox reactions in nitrate - formate systems

International Nuclear Information System (INIS)

Ananiev, A.V.; Shilov, V.P.; Tananaev, I.G.; Brossard, Ph.; Broudic, J.Ch.

2000-01-01

It was found that an intensive destruction of various organic and mineral substances - usual components of aqueous waste solutions (oxalic acid, complexones, urea, hydrazine, ammonium nitrate, etc.) takes place under the conditions of catalytic denitration. Kinetics and mechanisms of urea and ammonium nitrate decomposition in the system HNO 3 - HCOOH - Pt/SiO 2 are comprehensively investigated. The behaviour of uranium, neptunium and plutonium under the conditions of catalytic denitration is studied. It is shown, that under the certain conditions the formic acid is an effective reducer of the uranium (VI), neptunium (VI, V) and plutonium (VI, IV) ions. Kinetics of heterogeneous-catalytic red-ox reactions of uranium (VI), neptunium (VI, V) and plutonium (VI, IV) with formic acid are investigated. The mechanisms of the appropriate reactions are evaluated. (authors)

(Bio-)remediation of VCHC contaminants in a Technosol under unsaturated conditions.

Science.gov (United States)

Baumgarten, W; Fleige, H; Peth, S; Horn, R

2013-07-01

The remediation of dense non-aqueous phase liquids has always been a concern of both public and scientific interest groups. In this research work a modified physical concept of (bio)remediation of a volatile chlorinated hydrocarbon (VCHC) contamination was elaborated under laboratory conditions and modeled with HYDRUS-2D. In field dechlorination is influenced by both physicochemical and hydraulic properties of the substrate, e.g. texture, pore size distribution, pore liquid characteristics, e.g. viscosity, pH, surface tension, and dependent on the degree of saturation of the vadose zone. Undisturbed soil cores (100 cm³) were sampled from a Spolic Technosol. Considering hydraulic properties and functions, unsaturated percolation was performed with vertically and horizontally structured samples. VCHC concentrations were calculated prior, during, and after each percolation cycle. According to laboratory findings, microemulsion showed the most efficient results with regard to flow behavior in the unsaturated porous media and its accessibility for bacteria as nutrient. The efficiency of VCHC remediation could be increased by the application of a modified pump-and-treat system: the injection of bacteria Dehalococcoides ethanogenes with microemulsion, and extraction at a constant matric potential level of -6 kPa. Achieved data was used for HYDRUS-2D simulations, modeling in situ conditions, demonstrating the practical relevance (field scale) of performed unsaturated percolation (core scale), and in order to exclude capillary barrier effects.

Low temperature irradiation of vitrifiable mixtures of unsaturated monomers

International Nuclear Information System (INIS)

Kaetsu, I.; Ito, A.; Hayashi, K.

1975-01-01

A specific mixture containing at least one polymerizable unsaturated monomer which is not vitrifiable by itself can advantageously be polymerized by irradiating the mixture at a temperature not higher than 100 0 C above glass transition temperature of the mixture with an ionizing radiation and/or a light. 12 claims, 6 drawings, figures

Movement of pentachlorophenol in unsaturated soil by electrokinetics

Energy Technology Data Exchange (ETDEWEB)

Harbottle, M.; Sills, G. [Dept. of Engineering Science, Oxford (United Kingdom); Jackman, S. [Dept. of Engineering Science, Oxford (United Kingdom)]|[NERC Centre for Ecology and Hydrology, Oxford (United Kingdom); Thompson, I. [NERC Centre for Ecology and Hydrology, Oxford (United Kingdom)

2001-07-01

Electrokinetic experiments have been performed on unsaturated natural soil specimens artificially contaminated with pentachlorophenol. Movement of pentachlorophenol within the soil mass has been demonstrated, but no contaminant was discovered in any effluent fluids. The results indicate that it may be possible to improve the bioavailability of the pollutant to degradative microorganisms using electrokinetics, by moving the chemical and microbes relative to each others. (orig.)

Screening of Chlorinated Paraffins and Unsaturated Analogues in Commercial Mixtures: Confirmation of Their Occurrences in the Atmosphere.

Science.gov (United States)

Li, Tong; Gao, Shixiong; Ben, Yujie; Zhang, Hong; Kang, Qiyue; Wan, Yi

2018-02-20

Characterizing the detailed compositions of chlorinated paraffins (CPs) commercial mixtures is crucial to understand their environmental sources, fates, and potential risks. In this study, dichloromethane (DCM)-enhanced UPLC-ESI-QTOFMS analysis combined with characteristic isotope chlorine peaks is applied to screen all CPs and their structural analogues in the three most commonly produced CP commercial mixtures (CP-42, CP-52, and CP-70). Mass fractions of total short-chain CPs (SCCPs), medium-chain CPs (MCCPs) and long-chain CPs (LCCPs) ranged from 0.64 to 31.9%, 0.64 to 21.8%, and 0.04 to 43.9%, respectively, in the three commercial mixtures. 113 unsaturated SCCPs, MCCPs, and LCCPs were identified in the commercial mixtures. The detailed mass percentages of saturated and unsaturated CPs with carbon numbers of 10-30, chlorine numbers of 5-28, and unsaturated degrees of 0-7 were characterized in all commercial mixtures. Occurrences of the predominant saturated and unsaturated CPs were further confirmed in air samples collected in Guangdong Province, one of the major CP production areas in China, over one year. The profiles of the detected compounds indicated that LCCPs in air samples might come mainly from the production and usage of CP-52, and unsaturated C 24-29 -LCCPs were specifically originated from CP-70 used in the area.

Electrokinetic remediation of anionic contamination from unsaturated soil: Field application

International Nuclear Information System (INIS)

Lindgren, E.R.; Mattson, E.D.

1995-01-01

Electrokinetic remediation is an in situ technique under development at Sandia National Laboratories for removal of ionic contaminants from soil. While to date most other studies of this technique have focused on saturated soils, usually clays, the work at Sandia has been to extend the process to unsaturated sandy soils typical of arid regions. The impetus for this study is a chromate plume located beneath an old Sandia chemical waste landfill. Working in unsaturated soils is complicated by moisture control requirements, both to prevent undesired hydraulic transport of contamination outside the treatment zone and to optimize soil properties for efficient electrokinetic remediation. Two field tests will be discussed. First, a field test in clean soil is in progress to demonstrate moisture control with the Sandia electrode system. The second field demonstration, planned to begin the Fall of 1995, involves chromate removal from a in a chemical waste landfill

Scaling properties of conduction velocity in heterogeneous excitable media

Science.gov (United States)

Shajahan, T. K.; Borek, Bartłomiej; Shrier, Alvin; Glass, Leon

2011-10-01

Waves of excitation through excitable media, such as cardiac tissue, can propagate as plane waves or break up to form reentrant spiral waves. In diseased hearts reentrant waves can be associated with fatal cardiac arrhythmias. In this paper we investigate the conditions that lead to wave break, reentry, and propagation failure in mathematical models of heterogeneous excitable media. Two types of heterogeneities are considered: sinks are regions in space in which the voltage is fixed at its rest value, and breaks are nonconducting regions with no-flux boundary conditions. We find that randomly distributed heterogeneities in the medium have a decremental effect on the velocity, and above a critical density of such heterogeneities the conduction fails. Using numerical and analytical methods we derive the general relationship among the conduction velocity, density of heterogeneities, diffusion coefficient, and the rise time of the excitation in both two and three dimensions. This work helps us understand the factors leading to reduced propagation velocity and the formation of spiral waves in heterogeneous excitable media.

Evidence for an unsaturated-zone origin of secondary minerals in Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Whelan, Joseph F.; Roedder, Edwin; Paces, James B.

2001-01-01

The unsaturated zone (UZ) in Miocene-age welded tuffs at Yucca Mountain, Nevada, is under consideration as a potential site for the construction of a high-level radioactive waste repository. Secondary calcite and silica minerals deposited on fractures and in cavities in the UZ tuffs are texturally, isotopically, and geochemically consistent with UZ deposition from meteoric water infiltrating at the surface and percolating through the UZ along fractures. Nonetheless, two-phase fluid inclusions with small and consistent vapor to liquid (V:L) ratios that yield consistent temperatures within samples and which range from about 35 to about 80 C between samples have led some to attribute these deposits to formation from upwelling hydrothermal waters. Geochronologic studies have shown that calcite and silica minerals began forming at least 10 Ma and continued to form into the Holocene. If their deposition were really from upwelling water flooding the UZ, it would draw into question the suitability of the site as a waste repository

48Ca HETEROGENEITY IN DIFFERENTIATED METEORITES

International Nuclear Information System (INIS)

Chen, Hsin-Wei; Lee, Typhoon; Lee, Der-Chuen; Shen, Jason Jiun-San; Chen, Jiang-Chang

2011-01-01

Isotopic heterogeneities of 48 Ca have been found in numerous bulk meteorites that are correlated with 50 Ti and 54 Cr anomalies among differentiated planetary bodies, and the results suggest that a rare subset of neutron-rich Type Ia supernova (nSN Ia) was responsible for contributing these neutron-rich iron-group isotopes into the solar system (SS). The heterogeneity of these isotopes found in differentiated meteorites indicates that the isotopic compositions of the bulk SS are not uniform, and there are significant amounts of nSNe Ia dust incompletely mixed with the rest of SS materials during planetary formation. Combined with the data of now-extinct short-lived nuclide 60 Fe, which can be produced more efficiently from an nSN Ia than a Type II supernova ejecta, the observed planetary-scale isotopic heterogeneity probably reflects a late input of stellar dust grains with neutron-rich nuclear statistical equilibrium nuclides into the early SS.

Spatial heterogeneity of soils of the Cerrado-Pantanal ecotone

OpenAIRE

Lucena, Isabela Codolo de; Amorim, Ricardo Santos Silva; Lobo, Francisco de Almeida; Baldoni, Raquel Negrão; Matos, Dalva Maria da Silva

2014-01-01

In areas of the Cerrado-Pantanal ecotone in Brazil, the soil displays features which are inherent to the processes of soil formation, both of the Central Plateau and the Pantanal Plain. Given this premise, the area should be noteworthy for its high level of edaphic heterogeneity. The present study aimed to determine the physical, chemical and physico-hydric attributes that best explain the heterogeneity of soils in areas of the Cerrado-Pantanal ecotone, and to assess whether these attributes ...

Relating shear strength of unsaturated soils with capillary water retention curve

Directory of Open Access Journals (Sweden)

Zhou Annan

2016-01-01

Full Text Available This paper proposes a new water retention model for unsaturated soils, which takes into account capillary condensation of adsorbed water. In the proposed water retention model, the degree of saturation of a soil is separated into that based on capillary water and that based on adsorbed water. Through the analysis of a partially saturated two-cylinder system, a new shear strength criterion for unsaturated soils is proposed, in which only the degree of saturation based on capillary water contributes to the variation of shear strength with suction. The proposed shear strength criterion is justified against thermodynamic principles. The proposed strength criterion is compared against existing criteria in the literature, which shows that it provides a much improved prediction of the experimental data, for a wide range of suction values.

Harvesting Information from Heterogeneous Sources

DEFF Research Database (Denmark)

Qureshi, Pir Abdul Rasool; Memon, Nasrullah; Wiil, Uffe Kock

2011-01-01

The abundance of information regarding any topic makes the Internet a very good resource. Even though searching the Internet is very easy, what remains difficult is to automate the process of information extraction from the available online information due to the lack of structure and the diversi...... with performance of our tool with respect to each format. Finally, the different potential applications of the proposed tool are discussed with special emphasis on open source intelligence....... in the sharing methods. Most of the times, information is stored in different proprietary formats, complying with different standards and protocols which makes tasks like data mining and information harvesting very difficult. In this paper, an information harvesting tool (heteroHarvest) is presented...... with objectives to address these problems by filtering the useful information and then normalizing the information in a singular non hypertext format. We also discuss state of the art tools along with the shortcomings and present the results of an analysis carried out over different heterogeneous formats along...

Total fatty acid content of the plasma membrane of Saccharomyces cerevisiae is more responsible for ethanol tolerance than the degree of unsaturation.

Science.gov (United States)

Kim, Hyun-Soo; Kim, Na-Rae; Choi, Wonja

2011-03-01

The effect of change in unsaturated fatty acid composition on ethanol tolerance in Saccharomyces cerevisiae overexpressing ScOLE1 (∆9 fatty acid desaturase gene of S. cerevisiae), CaFAD2 (∆12 fatty acid desaturase gene of Candida albicans), or CaFAD3 (ω3 fatty acid desaturase gene of C. albicans) was examined. ScOLE1 over-expression increased the total unsaturated fatty acid content and enhanced ethanol tolerance, compared with a control strain. In contrast, overexpression of CaFAD2 and CaFAD3, which led to production of linoleic acid (18:2) and α-linolenic acid (18:3), respectively, neither changed total unsaturated fatty acids nor enhanced ethanol tolerance. The total unsaturated fatty acid content rather than the degree of unsaturation is thus an important factor for ethanol tolerance.

Study of reactive solutes transport and PAH migration in unsaturated soils

International Nuclear Information System (INIS)

Gujisaite, V.; Simonnot, M.O.; Gujisaite, V.; Morel, J.L.; Ouvrard, S.; Simonnot, M.O.; Gaudet, J.P.

2005-01-01

Experimental studies about solute transport in soil have most of the time been conducted under saturated conditions, whereas studies with unsaturated media are usually limited to hydrodynamic analysis. Those are mainly concerning the prediction of water flow, which is the main vector for the transport of contaminants in soil. Only a few studies have made the link between unsaturated flow and physical, chemical and biological interactions, which are controlling the availability of pollutants. However, the presence of a gaseous phase in soil can modify not only the movement of soil solution, but also chemical interactions and exchanges between soil aggregates and solution. Study of reactive solute transport in the vadose zone seems thus to be a necessary stage to predict contaminant fate in natural soils, for risk assessment as well as for the design of effective processes for the remediation of contaminated soils. This question is the main objective of the present work developed in the frame of our French Scientific Interest Group Industrial Wastelands called 'GISFI' (www.gisfi.prd.fr), based around a scientific and technological project dedicated to acquisition of knowledge for sustainable requalification of degraded sites polluted by past industrial activities. We will focus here on Polycyclic Aromatic Hydrocarbons (PAH), which are among the most widely discussed environmental contaminants because of their toxicity for human health and ecosystems. They are present in large quantities in soils polluted by former industrial activities, especially in relation to the coal extraction, exploitation and treatment. An experimental system has been specifically designed at the laboratory scale to carry out experiments under controlled conditions, with an unsaturated steady-state flow. The first experiments are performed on model soils, in order to investigate unsaturated steady-state flow in relation to interactions mechanisms. We have thus chosen to use a sandy

Three-dimensional saturated-unsaturated flow with axial symmetry to a partially penetrating well in a compressible unconfined aquifer

Science.gov (United States)

Tartakovsky, Guzel D.; Neuman, Shlomo P.

2007-01-01

A new analytical solution is presented for the delayed response process characterizing flow to a partially penetrating well in an unconfined aquifer. The new solution generalizes that of Neuman (1972, 1974) by accounting for unsaturated flow above the water table. Three-dimensional, axially symmetric flow in the unsaturated zone is described by a linearized version of Richards' equation in which hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value (defining the interface between the saturated and unsaturated zones). Unsaturated soil properties are characterized by an exponent κ having the dimension of inverse length or, equivalently, a dimensionless exponent κD = κb, where b is initial saturated thickness. Our treatment of the unsaturated zone is similar to that of Kroszynski and Dagan (1975), who, however, have ignored internal (artesian) aquifer storage. According to Kroszynski and Dagan, aquifers that are not excessively shallow have values of κD (their parameter a) much greater than 10. We find that in such typical cases, unsaturated flow has little impact on early and late dimensionless time drawdown a short distance below the water table. Unsaturated flow causes drawdown to increase slightly at intermediate dimensionless time values that represent transition from an early artesian-dominated to a late water-table-dominated flow regime. Delayed drainage from the unsaturated zone becomes less and less important as κD increases; as κD → ∞, this effect dies out, and drawdown is controlled entirely by delayed decline in the water table as in the model of Neuman. The unsaturated zone has a major impact on drawdown at intermediate time and a significant impact at early and late times, in the atypical case of κD ≤ 1, becoming the dominant factor as κD approaches zero (the soil water retention capacity becomes very large and/or saturated thickness becomes insignificant). Our

Identification of secondary phases formed during unsaturated reaction of UO2 with EJ-13 water

International Nuclear Information System (INIS)

Bates, J.K.; Tani, B.S.; Veleckis, E.

1989-01-01

A set of experiments, wherein UO 2 has been contacted by dripping water, has been conducted over a period of 182.5 weeks. The experiments are being conducted to develop procedures to study spent fuel reaction under unsaturated conditions that are expected to exist over the lifetime of the proposed Yucca Mountain repository site. One half of the experiments have been terminated, while one half are ongoing. Analyses of solutions that have dripped from the reacted UO 2 have been performed for all experiments, while the reacted UO 2 surfaces have been examined for the terminated experiments. A pulse of uranium release from the UO 2 solid, combined with the formation of schoepite on the surface of the UO 2 , was observed between 39 and 96 weeks of reaction. Thereafter, the uranium release decreased and a second set of secondary phases was observed. The latter phases incorporated cations from the EJ-13 water and included boltwoodite, uranophane, sklodowskite, compreignacite, and schoepite. The experiments are continuing to monitor whether additional changes in solution chemistry or secondary phase formation occurs. 6 refs., 2 figs., 2 tabs

Development of sugar palm yarn/glass fibre reinforced unsaturated polyester hybrid composites

Science.gov (United States)

Nurazzi, N. Mohd; Khalina, A.; Sapuan, S. Mohd; Rahmah, M.

2018-04-01

This study investigates the effect of fibre hybridization for sugar palm yarn fibre with glass fibre reinforced with unsaturated polyester composites. In this work, unsaturated polyester resin are reinforced with fibre at a ratio of 70:30 wt% and 60:40 wt%. The hybrid composites were characterized in terms of physical (density and water absorption), mechanical (tensile, flexural and compression) and thermal properties through thermal gravimetry analysis (TGA). Density determination showed that density increased with higher wt% of glass fibre. The inherently higher density of glass fibre increased the density of hybrid composite. Resistance to water absorption is improved upon the incorporation of glass fibre and the hybrid composites were found to reach equilibrium absorption at days 4 and 5. As for mechanical performance, the highest tensile strength, tensile modulus, flexural strength, flexural modulus and compression strength were obtained from 40 wt% of fibres reinforcement with ratio of 50:50 wt% of sugar palm yarn fibre and glass fibre reinforced unsaturated polyester composites. The increase of glass fibre loading had a synergistic effect on the mechanical properties to the composites structure due to its superior strength and modulus. The thermal stability of hybrid composites was improved by the increase of onset temperature and the reduction of residues upon increase in temperature.

Pyrite oxidation in unsaturated aquifer sediments. Reaction stoichiometry and rate of oxidation

DEFF Research Database (Denmark)

Andersen, Martin Søgaard; Larsen, Flemming; Postma, Diederik Jan

2001-01-01

The oxidation of pyrite (FeS2) contained in unsaturated aquifer sediment was studied by sediment incubation in gas impermeable polymer laminate bags. Reaction progress was followed over a period of nearly 2 months by monitoring the gas composition within the laminate bag. The gas phase in the inc......The oxidation of pyrite (FeS2) contained in unsaturated aquifer sediment was studied by sediment incubation in gas impermeable polymer laminate bags. Reaction progress was followed over a period of nearly 2 months by monitoring the gas composition within the laminate bag. The gas phase...... in the incubation bags became depleted in O2 and enriched in CO2 and N2 and was interpreted as due to pyrite oxidation in combination with calcite dissolution. Sediment incubation provides a new method to estimate low rates of pyrite oxidation in unsaturated zone aquifer sediments. Oxidation rates of up to 9.4â10......-10 mol FeS2/gâs are measured, and the rates are only weakly correlated with the sediment pyrite content. The reactivity of pyrite, including the inhibition by FeOOH layers formed on its surface, apparently has a major effect on the rate of oxidation. The code PHREEQC 2.0 was used to calculate...

Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone

Science.gov (United States)

Green, Christopher T.; Walvoord, Michelle Ann; Andraski, Brian J.; Striegl, Robert G.; Stonestrom, David A.

2015-01-01

Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.

Numerical study of compositional compressible degenerate two-phase flow in saturated–unsaturated heterogeneous porous media

KAUST Repository

Saad, Ali S.; Saad, Bilal Mohammed; Saad, Mazen

2016-01-01

We study the convergence of a combined finite volume-nonconforming finite element scheme on general meshes for a partially miscible two-phase flow model in anisotropic porous media. This model includes capillary effects and exchange between the phases. The diffusion term, which can be anisotropic and heterogeneous, is discretized by piecewise linear nonconforming triangular finite elements. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh. The relative permeability of each phase is decentered according to the sign of the velocity at the dual interface. The convergence of the scheme is proved thanks to an estimate on the two pressures which allows to show estimates on the discrete time and compactness results in the case of degenerate relative permeabilities. A key point in the scheme is to use particular averaging formula for the dissolution function arising in the diffusion term. We show also a simulation of hydrogen production in nuclear waste management. Numerical results are obtained by in-house numerical code. © 2015 Elsevier Ltd.

Numerical study of compositional compressible degenerate two-phase flow in saturated–unsaturated heterogeneous porous media

KAUST Repository

Saad, Ali S.

2016-01-02

We study the convergence of a combined finite volume-nonconforming finite element scheme on general meshes for a partially miscible two-phase flow model in anisotropic porous media. This model includes capillary effects and exchange between the phases. The diffusion term, which can be anisotropic and heterogeneous, is discretized by piecewise linear nonconforming triangular finite elements. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh. The relative permeability of each phase is decentered according to the sign of the velocity at the dual interface. The convergence of the scheme is proved thanks to an estimate on the two pressures which allows to show estimates on the discrete time and compactness results in the case of degenerate relative permeabilities. A key point in the scheme is to use particular averaging formula for the dissolution function arising in the diffusion term. We show also a simulation of hydrogen production in nuclear waste management. Numerical results are obtained by in-house numerical code. © 2015 Elsevier Ltd.

Slope stability of bioreactor landfills during leachate injection: effects of heterogeneous and anisotropic municipal solid waste conditions.

Science.gov (United States)

Giri, Rajiv K; Reddy, Krishna R

2014-03-01

In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

SYNTHESIS OF 2,3-UNSATURATED FURANIC HEX- AND PENT ...

African Journals Online (AJOL)

a

[12] and reduction in two steps of 3-(2-furyl)-acrolein[13] in good yields. The reaction of alcohols 2a-e with glucal 1, carried out in presence of boron trifluoride [7]. (method A), ferric chloride [11] (method B) and CAN [10] (method C), afforded the corresponding 2,3-unsaturated glucopyranosides 3a-e (Table 1). Table 1.

Moditored unsaturated soil transport processes as a support for large scale soil and water management

Science.gov (United States)

Vanclooster, Marnik

2010-05-01

The current societal demand for sustainable soil and water management is very large. The drivers of global and climate change exert many pressures on the soil and water ecosystems, endangering appropriate ecosystem functioning. The unsaturated soil transport processes play a key role in soil-water system functioning as it controls the fluxes of water and nutrients from the soil to plants (the pedo-biosphere link), the infiltration flux of precipitated water to groundwater and the evaporative flux, and hence the feed back from the soil to the climate system. Yet, unsaturated soil transport processes are difficult to quantify since they are affected by huge variability of the governing properties at different space-time scales and the intrinsic non-linearity of the transport processes. The incompatibility of the scales between the scale at which processes reasonably can be characterized, the scale at which the theoretical process correctly can be described and the scale at which the soil and water system need to be managed, calls for further development of scaling procedures in unsaturated zone science. It also calls for a better integration of theoretical and modelling approaches to elucidate transport processes at the appropriate scales, compatible with the sustainable soil and water management objective. Moditoring science, i.e the interdisciplinary research domain where modelling and monitoring science are linked, is currently evolving significantly in the unsaturated zone hydrology area. In this presentation, a review of current moditoring strategies/techniques will be given and illustrated for solving large scale soil and water management problems. This will also allow identifying research needs in the interdisciplinary domain of modelling and monitoring and to improve the integration of unsaturated zone science in solving soil and water management issues. A focus will be given on examples of large scale soil and water management problems in Europe.

Production of highly unsaturated fatty acids using agro-processing by-products

CSIR Research Space (South Africa)

Jacobs, A

2008-11-01

Full Text Available The South African agro-processing industry generates millions of tons of cereal derived by-products annually. The by-products from biofuel production are expected to increase these volumes dramatically. Highly unsaturated fatty acids (HUFA...

The paleohydrology of unsaturated and saturated zones at Yucca Mountain, Nevada, and vicinity

Science.gov (United States)

Paces, James B.; Whelan, Joseph F.; Stuckless, John S.

2012-01-01

Surface, unsaturated-zone, and saturated-zone hydrologic conditions at Yucca Mountain responded to past climate variations and are at least partly preserved by sediment, fossil, and mineral records. Characterizing past hydrologic conditions in surface and subsurface environments helps to constrain hydrologic responses expected under future climate conditions and improve predictions of repository performance. Furthermore, these records provide a better understanding of hydrologic processes that operate at time scales not readily measured by other means. Pleistocene climates in southern Nevada were predominantly wetter and colder than the current interglacial period. Cyclic episodes of aggradation and incision in Fortymile Wash, which drains the eastern slope of Yucca Mountain, are closely linked to Pleistocene climate cycles. Formation of pedogenic cement is favored under wetter Pleistocene climates, consistent with increased soil moisture and vegetation, higher chemical solubility, and greater evapotranspiration relative to Holocene soil conditions. The distribution and geochemistry of secondary minerals in subsurface fractures and cavities reflect unsaturated-zone hydrologic conditions and the response of the hydrogeologic system to changes in temperature and percolation flux over the last 12.8 m.y. Physical and fluid-inclusion evidence indicates that secondary calcite and opal formed in air-filled cavities from fluids percolating downward through connected fracture pathways in the unsaturated zone. Oxygen, strontium, and carbon isotope data from calcite are consistent with a descending meteoric water source but also indicate that water compositions and temperatures evolved through time. Geochronological data indicate that secondary mineral growth rates are less than 1–5 mm/m.y., and have remained approximately uniform over the last 10 m.y. or longer. These data are interpreted as evidence for hydrological stability despite large differences in surface moisture

Duplex Heterogeneous Nucleation Behavior of Precipitates in C-Mn Steel Containing Sn

Science.gov (United States)

Sun, Guilin; Tao, Sufen

2018-04-01

The two successive heterogeneous nucleation behaviors of FeSn2-MnS-Al2O3 complex precipitates in ultrahigh Sn-bearing steel were investigated. First, Al2O3 was the nucleation site of the MnS at the end of solidification. Then, FeSn2 nucleated heterogeneously on the MnS particles that nucleated on the Al2O3 particles. The formation sequence of the precipitated phase caused the duplex heterogeneous nucleation to occur consecutively at most twice.

Lithological Effects on Evaporation and Direct Infiltration Through the Unsaturated Zone in Damascus Oasis (Syria)

International Nuclear Information System (INIS)

Abou zakhem, B.

2004-01-01

Soil water movement is directly affected by the lithology and texture of soil profile. The objective of this study is to determine water movement mechanism through the unsaturated zone, by estimating the direct infiltration rate and evaporation process in Damascus Oasis, using isotope techniques. Two soil profiles were drilled using a hand-auger. Soil samples were subjected to granulometry, mineralogy, chemical and isotopic analysis. Isotopic measurements indicate that the evaporation front is located at shallow depth between 0 and 2 m. Variations in isotopic content indicate to the alternation of wet and dry periods corresponding to infiltration and evaporation processes respectively. Results show considerable difference in isotopic content between the unsaturated zone and the groundwater, which is mainly attributed to limited recharge of the aquifer through the unsaturated. Whereas the indirect groundwater recharge is considered to be more predominant. Chloride concentration correspond to stable isotopes in the unsaturated zone, it increases proportionally with the evaporation rate. Using chemical balance of Chloride, it was possible to estimate the effective recharge average rate which is ranging between 1.8 mm/y and 0.45 mm/y. The calculated mean evaporation rate according to Barnes and Allison model is 18.1 mm/y at water table level of 3 m depth. This rate decreases to 2.4 mm/y at 6 m depth. (author)

Method of coupling 1-D unsaturated flow with 3-D saturated flow on large scale

Directory of Open Access Journals (Sweden)

Yan Zhu

2011-12-01

Full Text Available A coupled unsaturated-saturated water flow numerical model was developed. The water flow in the unsaturated zone is considered the one-dimensional vertical flow, which changes in the horizontal direction according to the groundwater table and the atmospheric boundary conditions. The groundwater flow is treated as the three-dimensional water flow. The recharge flux to groundwater from soil water is considered the bottom flux for the numerical simulation in the unsaturated zone, and the upper flux for the groundwater simulation. It connects and unites the two separated water flow systems. The soil water equation is solved based on the assumed groundwater table and the subsequent predicted recharge flux. Then, the groundwater equation is solved with the predicted recharge flux as the upper boundary condition. Iteration continues until the discrepancy between the assumed and calculated groundwater nodal heads have a certain accuracy. Illustrative examples with different water flow scenarios regarding the Dirichlet boundary condition, the Neumann boundary condition, the atmospheric boundary condition, and the source or sink term were calculated by the coupled model. The results are compared with those of other models, including Hydrus-1D, SWMS-2D, and FEFLOW, which demonstrate that the coupled model is effective and accurate and can significantly reduce the computational time for the large number of nodes in saturated-unsaturated water flow simulation.

Isotopic constraints on heterogeneous sulfate production in Beijing haze

Science.gov (United States)

He, Pengzhen; Alexander, Becky; Geng, Lei; Chi, Xiyuan; Fan, Shidong; Zhan, Haicong; Kang, Hui; Zheng, Guangjie; Cheng, Yafang; Su, Hang; Liu, Cheng; Xie, Zhouqing

2018-04-01

Discerning mechanisms of sulfate formation during fine-particle pollution (referred to as haze hereafter) in Beijing is important for understanding the rapid evolution of haze and for developing cost-effective air pollution mitigation strategies. Here we present observations of the oxygen-17 excess of PM2.5 sulfate (Δ17O(SO42-)) collected in Beijing haze from October 2014 to January 2015 to constrain possible sulfate formation pathways. Throughout the sampling campaign, the 12-hourly averaged PM2.5 concentrations ranged from 16 to 323 µg m-3 with a mean of (141 ± 88 (1σ)) µg m-3, with SO42- representing 8-25 % of PM2.5 mass. The observed Δ17O(SO42-) varied from 0.1 to 1.6 ‰ with a mean of (0.9 ± 0.3) ‰. Δ17O(SO42-) increased with PM2.5 levels in October 2014 while the opposite trend was observed from November 2014 to January 2015. Our estimate suggested that in-cloud reactions dominated sulfate production on polluted days (PDs, PM2.5 ≥ 75 µg m-3) of Case II in October 2014 due to the relatively high cloud liquid water content, with a fractional contribution of up to 68 %. During PDs of Cases I and III-V, heterogeneous sulfate production (Phet) was estimated to contribute 41-54 % to total sulfate formation with a mean of (48 ± 5) %. For the specific mechanisms of heterogeneous oxidation of SO2, chemical reaction kinetics calculations suggested S(IV) ( = SO2 ⚫ H2O + HSO3- + SO32-) oxidation by H2O2 in aerosol water accounted for 5-13 % of Phet. The relative importance of heterogeneous sulfate production by other mechanisms was constrained by our observed Δ17O(SO42-). Heterogeneous sulfate production via S(IV) oxidation by O3 was estimated to contribute 21-22 % of Phet on average. Heterogeneous sulfate production pathways that result in zero-Δ17O(SO42-), such as S(IV) oxidation by NO2 in aerosol water and/or by O2 via a radical chain mechanism, contributed the remaining 66-73 % of Phet. The assumption about the thermodynamic state of aerosols

XML-based approaches for the integration of heterogeneous bio-molecular data.

Science.gov (United States)

Mesiti, Marco; Jiménez-Ruiz, Ernesto; Sanz, Ismael; Berlanga-Llavori, Rafael; Perlasca, Paolo; Valentini, Giorgio; Manset, David

2009-10-15

The today's public database infrastructure spans a very large collection of heterogeneous biological data, opening new opportunities for molecular biology, bio-medical and bioinformatics research, but raising also new problems for their integration and computational processing. In this paper we survey the most interesting and novel approaches for the representation, integration and management of different kinds of biological data by exploiting XML and the related recommendations and approaches. Moreover, we present new and interesting cutting edge approaches for the appropriate management of heterogeneous biological data represented through XML. XML has succeeded in the integration of heterogeneous biomolecular information, and has established itself as the syntactic glue for biological data sources. Nevertheless, a large variety of XML-based data formats have been proposed, thus resulting in a difficult effective integration of bioinformatics data schemes. The adoption of a few semantic-rich standard formats is urgent to achieve a seamless integration of the current biological resources.

Particle tracking for unsaturated-zone groundwater travel time analysis at Yucca Mountain

International Nuclear Information System (INIS)

Arnold, B.W.; Skinner, L.H.; Zieman, N.B.

1995-01-01

A particle tracking code developed to link numerical modeling of groundwater flow in the unsaturated zone to the analysis of groundwater travel times was used to produce preliminary estimates of the distribution of groundwater-travel time from a potential repository at Yucca Mountain, Nevada to the water table. Compliance with 10CFR960 requires the demonstration that pre-waste-emplacement groundwater travel time from the disturbed zone to the accessible environment is expected to exceed 1,000 years along any path of likely and significant radionuclide travel. The use of multiple particles and multiple realizations of the geology and parameter distributions in the unsaturated zone allows a probabilistic analysis of groundwater travel times that may be applied for evaluating compliance

Transient well flow in vertically heterogeneous aquifers

Science.gov (United States)

Hemker, C. J.

1999-11-01

A solution for the general problem of computing well flow in vertically heterogeneous aquifers is found by an integration of both analytical and numerical techniques. The radial component of flow is treated analytically; the drawdown is a continuous function of the distance to the well. The finite-difference technique is used for the vertical flow component only. The aquifer is discretized in the vertical dimension and the heterogeneous aquifer is considered to be a layered (stratified) formation with a finite number of homogeneous sublayers, where each sublayer may have different properties. The transient part of the differential equation is solved with Stehfest's algorithm, a numerical inversion technique of the Laplace transform. The well is of constant discharge and penetrates one or more of the sublayers. The effect of wellbore storage on early drawdown data is taken into account. In this way drawdowns are found for a finite number of sublayers as a continuous function of radial distance to the well and of time since the pumping started. The model is verified by comparing results with published analytical and numerical solutions for well flow in homogeneous and heterogeneous, confined and unconfined aquifers. Instantaneous and delayed drainage of water from above the water table are considered, combined with the effects of partially penetrating and finite-diameter wells. The model is applied to demonstrate that the transient effects of wellbore storage in unconfined aquifers are less pronounced than previous numerical experiments suggest. Other applications of the presented solution technique are given for partially penetrating wells in heterogeneous formations, including a demonstration of the effect of decreasing specific storage values with depth in an otherwise homogeneous aquifer. The presented solution can be a powerful tool for the analysis of drawdown from pumping tests, because hydraulic properties of layered heterogeneous aquifer systems with

Population dynamics on heterogeneous bacterial substrates

Science.gov (United States)

Mobius, Wolfram; Murray, Andrew W.; Nelson, David R.

2012-02-01

How species invade new territories and how these range expansions influence the population's genotypes are important questions in the field of population genetics. The majority of work addressing these questions focuses on homogeneous environments. Much less is known about the population dynamics and population genetics when the environmental conditions are heterogeneous in space. To better understand range expansions in two-dimensional heterogeneous environments, we employ a system of bacteria and bacteriophage, the viruses of bacteria. Thereby, the bacteria constitute the environment in which a population of bacteriophages expands. The spread of phage constitutes itself in lysis of bacteria and thus formation of clear regions on bacterial lawns, called plaques. We study the population dynamics and genetics of the expanding page for various patterns of environments.

Barriers to bacterial motility on unsaturated surfaces

DEFF Research Database (Denmark)

Dechesne, Arnaud; Smets, Barth F.

2013-01-01

Our knowledge of the spatial organization and spatial dynamics of microbial populations in soil at a scale close to that of the microorganisms is scarce. While passive dispersal via water ow or soil biota is probably a major dispersal route, it is reasonable to consider that active dispersal also...... and their isogenic mutants unable to express various type of motility we aimed to quantify the physical limits of bacterial motility. Our results demonstrate how hydration controls bacterial motility under unsaturated conditions. They can form the base of improved biodegradation models that include microbial...

Amino-functionalized metal-organic frameworks as tunable heterogeneous basic catalysts

Energy Technology Data Exchange (ETDEWEB)

Fischer, M.; Hartmann, M. [Erlangen-Nuernberg Univ., Erlangen (Germany). Erlangen Catalysis Resource Center

2011-07-01

Metal-organic framework (MOF) materials have been explored for applications in heterogeneous catalysis in recent years. In addition to the use of MOFs as supports for the deposition of highly dispersed metal particles, the incorporation of active centers such as coordinatively unsaturated metal sites and the functionalization of the organic linkers with acidic or basic groups seems to be most promising. In our contribution, three different MOFs carrying amino groups at their organic linkers, namely Fe-MIL-101-NH{sub 2} (S{sub BET} = 3438 m{sup 2}g{sup -1}), Al-MIL-101-NH{sub 2} (S{sub BET} = 3099 m{sup 2}g{sup -1}) and CAU-1 (S{sub BET} = 1492 m{sup 2}g{sup -1}), were synthesized and tested in the Knoevenagel condensation of benzaldehyde with malononitrile and with ethyl cyanoacetate, respectively. It is shown that the expected products benzylidenemalononitrile (BzMN) and ethyl a-cyanocinnamate (EtCC) are formed with selectivities of more than 99 % and yields of 90 to 95 % after 3 h (for BzMN). Due to the very small pore windows of CAU-1 (0.3 to 0.4 nm) the reaction proceeds much slower over this catalyst in comparison to the amino-MIL-101 derivatives, which possess open pore windows of up to 1.6 nm. Finally, leaching tests confirm that the reaction is heterogeneously catalyzed. Moreover, the catalysts are recyclable without significant loss of activity. (orig.)

Tensile Properties of Unsaturated Polyester and Epoxy Resin Reinforced with Recycled Carbon-Fiber-Reinforced Plastic

Science.gov (United States)

Okayasu, Mitsuhiro; Kondo, Yuta

2018-06-01

To better understand the mechanical properties of recycled carbon-fiber-reinforced plastic (rCFRP), CFRP crushed into small pieces was mixed randomly in different proportions (0-30 wt%) with two different resins: unsaturated polyester and epoxy resin. Two different sizes of crushed CFRP were used: 0.1 mm × 0.007 mm (milled CFRP) and 30 mm × 2 mm (chopped CFRP). The tensile strength of rCFRP was found to depend on both the proportion and the size of the CFRP pieces. It increased with increasing proportion of chopped CFRP, but decreased with increasing proportion of milled CFRP. There was no clear dependence of the tensile strength on the resin that was used. A low fracture strain was found for rCFRP samples made with chopped CFRP, in contrast to those made with milled CFRP. The fracture strain was found to increase with increasing content of milled CFRP up to 20 wt%, at which point, coalescence of existing microvoids occurred. However, there was a reduction in fracture strain for rCFRP with 30 wt% of milled CFRP, owing to the formation of defects (blow holes). Overall, the fracture strain was higher for rCFRPs based on epoxy resin than for those based on unsaturated polyester with the same CFRP content, because of the high ductility of the epoxy resin. The different tensile properties reflected different failure characteristics, with the use of chopped CFRP leading to a complicated rough fracture surface and with milled CFRP causing ductile failure through the presence of tiny dimple-like fractures. However, for a high content of milled CFRP (30 wt%), large blow holes were observed, leading to low ductility.

Numerical Simulation of Natural Convection in Heterogeneous Porous media for CO2 Geological Storage

NARCIS (Netherlands)

Ranganathan, P.; Farajzadeh, R.; Bruining, J.; Zitha, P.L.J.

2012-01-01

We report a modeling and numerical simulation study of density-driven natural convection during geological CO2 storage in heterogeneous formations. We consider an aquifer or depleted oilfield overlain by gaseous CO2, where the water density increases due to CO2 dissolution. The heterogeneity of the

The Role of Surface Infiltration in Hydromechanical Coupling Effects in an Unsaturated Porous Medium of Semi-Infinite Extent

Directory of Open Access Journals (Sweden)

L. Z. Wu

2017-01-01

Full Text Available Rainfall infiltration into an unsaturated region of the earth’s surface is a pervasive natural phenomenon. During the rainfall-induced seepage process, the soil skeleton can deform and the permeability can change with the water content in the unsaturated porous medium. A coupled water infiltration and deformation formulation is used to examine a problem related to the mechanics of a two-dimensional region of semi-infinite extent. The van Genuchten model is used to represent the soil-water characteristic curve. The model, incorporating coupled infiltration and deformation, was developed to resolve the coupled problem in a semi-infinite domain based on numerical methods. The numerical solution is verified by the analytical solution when the coupled effects in an unsaturated medium of semi-infinite extent are considered. The computational results show that a numerical procedure can be employed to examine the semi-infinite unsaturated seepage incorporating coupled water infiltration and deformation. The analysis indicates that the coupling effect is significantly influenced by the boundary conditions of the problem and varies with the duration of water infiltration.

Effects from Unsaturated Zone Flow during Oscillatory Hydraulic Testing

Science.gov (United States)

Lim, D.; Zhou, Y.; Cardiff, M. A.; Barrash, W.

2014-12-01

In analyzing pumping tests on unconfined aquifers, the impact of the unsaturated zone is often neglected. Instead, desaturation at the water table is often treated as a free-surface boundary, which is simple and allows for relatively fast computation. Richards' equation models, which account for unsaturated flow, can be compared with saturated flow models to validate the use of Darcy's Law. In this presentation, we examine the appropriateness of using fast linear steady-periodic models based on linearized water table conditions in order to simulate oscillatory pumping tests in phreatic aquifers. We compare oscillatory pumping test models including: 1) a 2-D radially-symmetric phreatic aquifer model with a partially penetrating well, simulated using both Darcy's Law and Richards' Equation in COMSOL; and 2) a linear phase-domain numerical model developed in MATLAB. Both COMSOL and MATLAB models are calibrated to match oscillatory pumping test data collected in the summer of 2013 at the Boise Hydrogeophysical Research Site (BHRS), and we examine the effect of model type on the associated parameter estimates. The results of this research will aid unconfined aquifer characterization efforts and help to constrain the impact of the simplifying physical assumptions often employed during test analysis.

Estimating the timing and location of shallow rainfall-induced landslides using a model for transient, unsaturated infiltration

Science.gov (United States)

Baum, Rex L.; Godt, Jonathan W.; Savage, William Z.

2010-01-01

Shallow rainfall-induced landslides commonly occur under conditions of transient infiltration into initially unsaturated soils. In an effort to predict the timing and location of such landslides, we developed a model of the infiltration process using a two-layer system that consists of an unsaturated zone above a saturated zone and implemented this model in a geographic information system (GIS) framework. The model links analytical solutions for transient, unsaturated, vertical infiltration above the water table to pressure-diffusion solutions for pressure changes below the water table. The solutions are coupled through a transient water table that rises as water accumulates at the base of the unsaturated zone. This scheme, though limited to simplified soil-water characteristics and moist initial conditions, greatly improves computational efficiency over numerical models in spatially distributed modeling applications. Pore pressures computed by these coupled models are subsequently used in one-dimensional slope-stability computations to estimate the timing and locations of slope failures. Applied over a digital landscape near Seattle, Washington, for an hourly rainfall history known to trigger shallow landslides, the model computes a factor of safety for each grid cell at any time during a rainstorm. The unsaturated layer attenuates and delays the rainfall-induced pore-pressure response of the model at depth, consistent with observations at an instrumented hillside near Edmonds, Washington. This attenuation results in realistic estimates of timing for the onset of slope instability (7 h earlier than observed landslides, on average). By considering the spatial distribution of physical properties, the model predicts the primary source areas of landslides.

Synopsis of some preliminary computational studies related to unsaturated zone transport at Area G

International Nuclear Information System (INIS)

Vold, E.

1998-03-01

Computational transport models are described with applications in three problem areas related to unsaturated zone moisture movement beneath Area G. These studies may be used to support the ongoing maintenance of the site Performance Assessment. The three areas include: a 1-D transient analysis with average tuff hydraulic properties in the near surface region with computed results compared to field data; the influence on near surface transient moisture percolation due to realistic distributions in hydraulic properties derived statistically from the observed variance in the field data; and the west to east moisture flow in a 2-D steady geometry approximation of the Pajarito Plateau. Results indicate that a simple transient model for transport of moisture volume fraction fits field data well compared to a moisture pulse observed in the active disposal unit, pit 37. Using realistic infiltration boundary conditions for summer showers and for spring snow melt conditions, the computed moisture pulses show significant propagation to less than 10-ft depth. Next, the hydraulic properties were varied on a 2-D grid using statistical distributions based on the field data means and variances for the hydraulic parameters. Near surface transient percolation in these conditions shows a qualitatively realistic percolation with a spatially variable wave front moving into the tuff; however, the flow does not channel into preferred paths and suggests there is no formation of fast paths which could enhance transportation of contaminants. Finally, moisture transport is modeled through an unsaturated 2-D slice representing the upper stratigraphic layers beneath Area G and a west-to-east cut of several miles to examine possible lateral movement from the west where percolation is assumed to be greater than at Area G. Results show some west-to-east moisture flux consistent with the assumed profile for the percolation boundary conditions

New Class of Solutions for Water Infiltration Problems in Unsaturated Soils

DEFF Research Database (Denmark)

Barari, Amin; Omidvar, M; Momeni, M

2010-01-01

This paper presents the results of approximate analytical solutions to Richards’ equation, which governs the problem of unsaturated flow in porous media. The existing methods generally fall within the category of numerical and analytical methods, often having many restrictions for practical situa...

Geochemical modelling of hydrogen gas migration in an unsaturated bentonite buffer

NARCIS (Netherlands)

Sedighi, M.; Thomas, H.R.; Al Masum, S.; Vardon, P.J.; Nicholson, D.; Chen, Q.

2014-01-01

This paper presents an investigation of the transport and fate of hydrogen gas through compacted bentonite buffer. Various geochemical reactions that may occur in the multiphase and multicomponent system of the unsaturated bentonite buffer are considered. A reactive gas transport model, developed

Development of methods to evaluate uranium distribution coefficients in unsaturated media

International Nuclear Information System (INIS)

Sautman, M.T.; Simonson, S.A.

1993-01-01

To date, batch sorption and dynamic column experiments have been performed for many elements as part of site characterization programs. These experiments were often conducted with samples having relatively high liquid/solid ratios (in some cases the solid volume was much smaller than the solution volume). The development of methods for measuring sorption parameters at low liquid/solid ratios was undertaken to attempt to judge whether or not results of saturated experiments are valid for use in performance assessments of sites located in unsaturated rocks. The amount of hydrologic saturation can affect the ionic strength, pH, and redox potential which can in turn affect sorption. In addition, the presence of the gas phase may affect the amount of wetting occurring on the solid's surface. This paper describes experimental procedures which were developed to evaluate the sorption of uranium by silica sand at predetermined levels of unsaturation

Steady state method to determine unsaturated hydraulic conductivity at the ambient water potential

Science.gov (United States)

HUbbell, Joel M.

2014-08-19

The present invention relates to a new laboratory apparatus for measuring the unsaturated hydraulic conductivity at a single water potential. One or more embodiments of the invented apparatus can be used over a wide range of water potential values within the tensiometric range, requires minimal laboratory preparation, and operates unattended for extended periods with minimal supervision. The present invention relates to a new laboratory apparatus for measuring the unsaturated hydraulic conductivity at a single water potential. One or more embodiments of the invented apparatus can be used over a wide range of water potential values within the tensiometric range, requires minimal laboratory preparation, and operates unattended for extended periods with minimal supervision.

Studies of reaction difference between γ-ray and glow discharge on hydrogenation of unsaturated fatty acid esters

International Nuclear Information System (INIS)

Sakoda, Tatsuya; Nieda, Hiroshi; Kitahara, Kazuta; Ando, Kiyomi

2000-01-01

Hydrogenation of unsaturated fatty acid esters using an inductively coupled plasma at low pressure was performed, and electron temperature and density were measured using a double-probe in order to investigate the reaction difference between γ-ray and glow discharge on hydrogenation. In this experiment, unsaturated fatty acid esters were partly hydrogenated by the hydrogen plasma that had electron temperature of 3.5 eV, which was more efficient than γ-ray irradiation method. As a result, it was found that the plasma can effectively supply electrons that had the optimum energy for hydrogenation at the interface of fatty acids as well as excited atoms and ions. Also, the plasma generated at low pressure would be possible to convert unsaturated fatty acids into saturated fatty acids without breaking the starting monomer. (author)

Going greener: Synthesis of fully biobased unsaturated polyesters for styrene crosslinked resins with enhanced thermomechanical properties

Directory of Open Access Journals (Sweden)

C. S. M. F. Costa

2017-11-01

Full Text Available The main goal of this work was the development of fully biobased unsaturated polyesters (UPs that upon crosslinking with unsaturated monomers (UM could lead to greener unsaturated polyester resins (UPRs with similar thermomechanical properties to commercial fossil based UPR. After the successful synthesis of the biobased UPs, those were crosslinked with styrene (Sty, the most commonly used monomer, and the influence of the chemical structure of the UPs on the thermomechanical characteristics of UPRs were evaluated. The properties were compared with those of a commercial resin (Resipur 9837©. The BioUPRs presented high gel contents and contact angles that are similar to the commercial resin. The thermomechanical properties were evaluated by dynamic mechanical thermal analysis (DMTA and it was found that the UPR synthesized using propylene glycol (PG, succinic acid (SuAc and itaconic acid (ItAc presented very close thermomechanical properties compared to the commercial resin.

A free boundary problem describing the saturated-unsaturated flow in a porous medium

Directory of Open Access Journals (Sweden)

Gabriela Marinoschi

2004-01-01

Full Text Available This paper presents a functional approach to a nonlinear model describing the complete physical process of water infiltration into an unsaturated soil, including the saturation occurrence and the advance of the wetting front. The model introduced in this paper involves a multivalued operator covering the simultaneous saturated and unsaturated flow behaviors and enhances the study of the displacement of the free boundary between these two flow regimes. The model resides in Richards' equation written in pressure form with an initial condition and boundary conditions which in this work express the inflow due to the rain on the soil surface on the one hand, and characterize a certain permeability corresponding to the underground boundary, on the other hand. Existence, uniqueness, and regularity results for the transformed model in diffusive form, that is, for the moisture of the soil, and the existence of the weak solution for the pressure form are proved in the 3D case. The main part of the paper focuses on the existence of the free boundary between the saturated and unsaturated parts of the soil, and this is proved, in the 1D case, for certain stronger assumptions on the initial data and boundary conditions.

The Effect of Intra-Ruminal Infusion of Saturated and Unsaturated ...

African Journals Online (AJOL)

This study investigated the effect of different proportional combinations of a saturated fatty acid (Palmitic acid, PA) and unsaturated fatty acid (Linolenic acid, LA) on rumen outflow rate (r) in West African dwarf (WAD) sheep. A 5x5 Latin square experimental model of five sheep and five combination proportions of palmitic and ...

A statistical approach for water movement in the unsaturated zone

International Nuclear Information System (INIS)

Tielin Zang.

1991-01-01

This thesis presents a statistical approach for estimating and analyzing the downward transport pattern and distribution of soil water by the use of pattern analysis of space-time correlation structures. This approach, called the Space-time-Correlation Field, is mainly based on the analyses of correlation functions simultaneously in the space and time domain. The overall purpose of this work is to derive an alternative statistical procedure in soil moisture analysis without involving detailed information on hydraulic parameters and to visualize the dynamics of soil water variability in the space and time domains. A numerical model using method of characteristics is employed to provide hypothetical time series to use in the statistical method, which is, after the verification and calibration, applied to the field measured time series. The results of the application show that the space-time correlation fields reveal effects of soil layers with different hydraulic properties and boundaries between them. It is concluded that the approach poses special advantages when visualizing time and space dependent properties simultaneously. It can be used to investigate the hydrological response of soil water dynamics and characteristics in different dimensions (space and time) and scales. This approach can be used to identify the dominant component in unsaturated flow systems. It is possible to estimate the pattern and the propagation rate downwards of moisture movement in the soil profile. Small-scale soil heterogeneities can be identified by the correlation field. Since the correlation field technique give a statistical measure of the dependent property that varies within the space-time field, it is possible to interpolate the fields to points where observations are not available, estimating spatial or temporal averages from discrete observations. (au)

Secondary organic aerosol formation by limonene ozonolysis: Parameterizing multi-generational chemistry in ozone- and residence time-limited indoor environments

Science.gov (United States)

Waring, Michael S.

2016-11-01

Terpene ozonolysis reactions can be a strong source of secondary organic aerosol (SOA) indoors. SOA formation can be parameterized and predicted using the aerosol mass fraction (AMF), also known as the SOA yield, which quantifies the mass ratio of generated SOA to oxidized terpene. Limonene is a monoterpene that is at sufficient concentrations such that it reacts meaningfully with ozone indoors. It has two unsaturated bonds, and the magnitude of the limonene ozonolysis AMF varies by a factor of ∼4 depending on whether one or both of its unsaturated bonds are ozonated, which depends on whether ozone is in excess compared to limonene as well as the available time for reactions indoors. Hence, this study developed a framework to predict the limonene AMF as a function of the ozone [O3] and limonene [lim] concentrations and the air exchange rate (AER, h-1), which is the inverse of the residence time. Empirical AMF data were used to calculate a mixing coefficient, β, that would yield a 'resultant AMF' as the combination of the AMFs due to ozonolysis of one or both of limonene's unsaturated bonds, within the volatility basis set (VBS) organic aerosol framework. Then, β was regressed against predictors of log10([O3]/[lim]) and AER (R2 = 0.74). The β increased as the log10([O3]/[lim]) increased and as AER decreased, having the physical meaning of driving the resultant AMF to the upper AMF condition when both unsaturated bonds of limonene are ozonated. Modeling demonstrates that using the correct resultant AMF to simulate SOA formation owing to limonene ozonolysis is crucial for accurate indoor prediction.

Heterogeneous self-assembled media for biopolymerization

DEFF Research Database (Denmark)

Monnard, Pierre-Alain

2011-01-01

Heterogeneous media, such as micro-structured aqueous environments, could offer an alternative approach to the synthesis of biopolymers with novel functions. Structured media are here defined as specialized, self-assembled structures that are formed, e.g, by amphiphiles, such as liposomes, emulsion...... polymerization, the initial elongation rates clearly depended on the complementarity of the monomers with the templating nucleobases3. However, metal-ion catalyzed reactions deliver RNA analogs with heterogeneous linkages. Moreover, the usefulness of this medium in the form of quasi-compartmentalization extends...... beyond metal-ion catalysis reactions, as we have recently demonstrated the catalytic power of a dipeptide, SerHis, for the regioselective formation of phosphodiester bonds. These results in conjonction with the synthesis of nucleobases at -78˚C, the demonstration of ribozyme activity (RNA ligase ribozyme...

Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

Science.gov (United States)

Langenbruch, C.; Shapiro, S. A.

2014-12-01

For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding

An exploration of unsaturated zone during in-situ heating test in sedimentary soft rocks

International Nuclear Information System (INIS)

Kubota, Kenji; Suzuki, Koichi; Ikenoya, Takafumi; Takakura, Nozomu; Tani, Kazuo

2011-01-01

In-situ heating test has been conducted to evaluate the influence of high temperature in an underground facility at a depth of 50 m. Resistivity monitoring is thought to be effective to map the extent of the high temperature and unsaturated zone. So we have conducted resistivity tomography during the heating test. As a result, the resistivity of the rock mass around the heating well was decreased and this area was gradually expanded from the heated area during the heating. This suggests that high temperature zone is detected by resistivity tomography. The results also suggested that resistivity was increased by unsaturation of rock mass around the heating well. (author)

Role of heterogeneity of lipids in predicting risk of atheroma formation in metabolic syndrome

International Nuclear Information System (INIS)

Asim, M.; Ahmad, M.; Hasan, S.

2013-01-01

Objective: Assessing impact of heterogeneous lipids in predisposing cardiovascular (CV) atheroma formation in adolescents with metabolic syndrome (MS). Study Design: Cross-sectional analytical. Place and Duration of Study: Educational Institutes of Lahore. Six months Material and Methods: A total of 193, 17-25 year old subjects, 106 males and 87 females were recruited. A record regarding each subject's personal, socioeconomic, educational, dietary and family histories was taken. They underwent the following anthropometric measurements: waist circumference/WC (cm), hip circumference/HC (cm), height (inches), weight (kg), waist hip ratio/WHR, body mass index/BMI and blood pressure. Laboratory investigations included fasting blood samples for glucose and lipids; including total cholesterol (TC), high density lipoprotein-cholesterol (HDL-c), low density lipoprotein-cholesterol (LDL-c) and triglycerides (TG). Calculations for TG/HDL ratio and TC/HDL ratio were made. Results: Metabolic syndrome (MS) was present in 26 (13.5%) individuals. Male to female ratio was 3:1. Values of waist circumference, blood pressure, fasting plasma glucose, triglyceride and HDL-c, were all high. On comparison of fasting lipid profile, TC/HDL ratio and TG/HDL ratio, it was observed that the average total cholesterol, HDL cholesterol, TCL/HDL ratio were insignificant. The average triglyceride level and TG/HDL ratio were all high. The ROC curve for total cholesterol, HDL-c, TG, TC/HDL and TG/HDL ratio yielded 0.555, 0.526, 0.912, 0.548 and 0.913 areas under the curve. Plasma TG, TG/HDL ratio produced significant p-values < 0.001. Abnormal triglycerides and TG/HDL ratio at a cutoff of 3.98 was diagnosed with high sensitivity and specificity. Conclusion: Fasting triglyceride and HDL-c play a major role in the pathogenesis of MS at an early age. Triglyceride level and TG/HDL ratio as opposed to HDL-c and TC/HDL-c clearly define the risk for development of atheroma formation in our adolescent

Reduction of , -Unsaturated Ketones Using a Zn/NiCl System in ...

African Journals Online (AJOL)

NJD

Reduction of , -Unsaturated Ketones Using a Zn/NiCl. 2. System in Aqueous Media in the Presence of Anionic and. Cationic Surfactants. Hocine Ilikti*, Tayeb Benabdallah, Kamel Bentayeb, Adil A. Othman and Zoubir Derriche. Organic Chemistry and Electrochemistry Laboratory, Department of Chemistry, Faculty of Science, ...

Elastoplastic model for unsaturated, quasi-saturated and fully saturated fine soils

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Lai Ba Tien

2016-01-01

Full Text Available In unsaturated soils, the gaseous phase is commonly assumed to be continuous. This assumption is no more valid at high saturation ratio. In that case, air bubbles and pockets can be trapped in the porous network by the liquid phase and the gas phase becomes discontinuous. This trapped air reduces the apparent compressibility of the pore fluid and affect the mechanical behavior of the soil. Although it is trapped in the pores, its dissolution can take place. Dissolved air can migrate through the pore space, either by following the flow of the fluid or by diffusion. In this context, this paper present a hydro mechanical model that separately considers the kinematics and the mechanical behavior of each fluid species (eg liquid water, dissolved air, gaseous air and the solid matrix. This new model was implemented in a C++ code. Some numerical simulations are performed to demonstrate the ability of this model to reproduce a continuous transition of unsaturated to saturated states.

Prediction of unsaturated flow and water backfill during infiltration in layered soils

Science.gov (United States)

Cui, Guotao; Zhu, Jianting

2018-02-01

We develop a new analytical infiltration model to determine water flow dynamics around layer interfaces during infiltration process in layered soils. The model mainly involves the analytical solutions to quadratic equations to determine the flux rates around the interfaces. Active water content profile behind the wetting front is developed based on the solution of steady state flow to dynamically update active parameters in sharp wetting front infiltration equations and to predict unsaturated flow in coarse layers before the front reaches an impeding fine layer. The effect of water backfill to saturate the coarse layers after the wetting front encounters the impeding fine layer is analytically expressed based on the active water content profiles. Comparison to the numerical solutions of the Richards equation shows that the new model can well capture water dynamics in relation to the arrangement of soil layers. The steady state active water content profile can be used to predict the saturation state of all layers when the wetting front first passes through these layers during the unsteady infiltration process. Water backfill effect may occur when the unsaturated wetting front encounters a fine layer underlying a coarse layer. Sensitivity analysis shows that saturated hydraulic conductivity is the parameter dictating the occurrence of unsaturated flow and water backfill and can be used to represent the coarseness of soil layers. Water backfill effect occurs in coarse layers between upper and lower fine layers when the lower layer is not significantly coarser than the upper layer.

Solutes transport in unsaturated double-porosity medium. Modelling by homogenization and applications

International Nuclear Information System (INIS)

Tran Ngoc, T.D.

2008-07-01

This Ph.D thesis presents the development of the solute transport models in unsaturated double-porosity medium, by using the asymptotic homogenization method. The obtained macroscopic models concern diffusion, diffusion-convection and dispersion-convection, according to the transport regime which is characterized by the non-dimensional numbers. The models consist of two coupled equations that show the local non-equilibrium of concentrations. The double-porosity transport models were numerically implemented using the code COMSOL Multiphysics (finite elements method), and compared with the solution of the same problem at the fine scale. The implementation allows solving the coupled equations in the macro- and micro-porosity domains (two-scale computations). The calculations of the dispersion tensor as a solution of the local boundary value problems, were also conducted. It was shown that the dispersivity depends on the saturation, the physical properties of the macro-porosity domain and the internal structure of the double-porosity medium. Finally, two series of experiments were performed on a physical model of double-porosity that is composed of a periodic assemblage of sintered clay spheres in Hostun sand HN38. The first experiment was a drainage experiment, which was conducted in order to validate the unsaturated flow model. The second series was a dispersion experiment in permanent unsaturated water flow condition (water content measured by gamma ray attenuation technique). A good agreement between the numerical simulations and the experimental observations allows the validation of the developed models. (author)

Electro-chemistry of soil formation. VI. Atmospheric salts in relation to soil and peat formation and plant composition

Energy Technology Data Exchange (ETDEWEB)

Mattson, S; Sandberg, G; Terning, P E

1944-01-01

The Ca/Mg ratios have been determined in the Ramna bog, in the Unden and Annerstad podzol profile series, and in the Dala brown earth series. A number of plant species from each locality have been included. The more ombrogenic the formation, the lower the Ca/Mg ratios. An application of the Donnan equilibrium leads to the conclusion that the saturation with bases may be considerable in ombrogenic peat, whereas the saturation of excessively leached mineral soils must be very small. The latter must, like all weak or unsaturated soil acidoids in general, contain a relatively high proportion of exchangeable alkali cations.

In-situ arsenic removal during groundwater recharge through unsaturated alluvium

Science.gov (United States)

O'Leary, David; Izbicki, John; T.J. Kim,; Clark Ajawani,; Suarez, Donald; Barnes, Thomas; Thomas Kulp,; Burgess, Matthew K.; Tseng, Iwen

2015-01-01

OBJECTIVES The purpose of this study was to determine the feasibility and sustainability of in-situ removal of arsenic from water infiltrated through unsaturated alluvium. BACKGROUND Arsenic is naturally present in aquifers throughout the southwestern United States and elsewhere. In January 2006, the U.S. Environmental Protection Agency (EPA) lowered the Maximum Contaminant Level (MCL) for arsenic from 50 to 10 micrograms per liter (g/L). This raised concerns about naturally-occurring arsenic in groundwater. Although commercially available systems using sorbent iron or aluminum oxide resins are available to treat high-arsenic water, these systems are expensive to build and operate, and may generate hazardous waste. Iron and aluminum oxides occur naturally on the surfaces of mineral grains that compose alluvial aquifers. In areas where alluvial deposits are unsaturated, these oxides may sorb arsenic in the same manner as commercial resins, potentially providing an effective low-cost alternative to commercially engineered treatment systems. APPROACH The Antelope Valley within the Mojave Desert of southern California contains a shallow water-table aquifer with arsenic concentrations of 5 g/L, and a deeper aquifer with arsenic concentrations of 30 g/L. Water was pumped from the deep aquifer into a pond and infiltrated through an 80 m-thick unsaturated zone as part of field-scale and laboratory experiments to treat high-arsenic groundwater and recharge the shallow water table aquifer at the site. The field-scale recharge experiment included the following steps: 1) construction of a recharge pond 2) test drilling for sample collection and instrument installation adjacent to the pond 3) monitoring downward migration of water infiltrated from the pond 4) monitoring changes in selected trace-element concentrations as water infiltrated through the unsaturated zone Data from instruments within the borehole adjacent to the pond were supplemented with borehole and

Supplementation with bypass fat in silvopastoral systems diminishes the ratio of milk saturated/unsaturated fatty acids.

Science.gov (United States)

Mahecha, L; Angulo, J; Salazar, B; Cerón, M; Gallo, J; Molina, C H; Molina, E J; Suárez, J F; Lopera, J J; Olivera, M

2008-04-01

This study was conducted to evaluate if supplementing bypass fat to cows under silvopastoral systems, increases the concentration of unsaturated fatty acids in milk, thus improving the saturated/ unsaturated ratio without a negative effect on total milk yield in fat or protein. Two concentrations of two different sources of bypass fat were evaluated for 40 days, each in a group of 24 multiparous Lucerna (Colombian breed) cows. A cross-over design of 8 Latin squares 3 x 3 was used. The variables submitted to analysis were body condition, daily milk production and milk composition. Body condition, milk yield and milk quality were not different but there was a significant decrease in the amount of saturated fatty acid in both experiments while the unsaturated fat increased significantly in experiment 1 and remained stable in experiment 2. Results, such as these have as far as we know, not been reported previously and they provide an approach for the improvement of milk as a "functional food".

Effects of heterogeneity on recrystallization kinetics of nanocrystalline copper prepared by dynamic plastic deformation

DEFF Research Database (Denmark)

Lin, Fengxiang; Zhang, Yubin; Tao, Nairong

2014-01-01

to develop a heterogeneous structure, consisting of regions with different textures and microstructures. This heterogeneity within the deformed structure leads to the formation of severely clustered grains in partially recrystallized samples. The recrystallization kinetic curve shows an Avrami exponent less...... recrystallization kinetics. The hardness of the two samples was measured, and the mechanical properties before and after partial recrystallization of both samples are discussed based on the presence of structural heterogeneities on the macroscopic and the microscopic scale....

Freezing process in unsaturated packed beds; Fuhowa ryushi sonai ni okeru suibun toketsu

Energy Technology Data Exchange (ETDEWEB)

Akahori, M; Aoki, K; Hattori, M [Nagaoka University of Technology, Niigata (Japan); Tani, T [Oji Paper Co. Ltd., Tokyo (Japan)

1998-04-25

The freezing process in unsaturated packed beds has been investigated experimentally and theoretically. Water transport to the frozen front plays an important part on freezing. The rate of the absorption of water into frozen layer depended on the freezing heat flux and the water saturation at the freezing front. As a result, ice content in the frozen layer was related to the rate of the absorption of water and the freezing heat flux. A one-dimensional freezing model in unsaturated packed beds has been presented, accounting for the water transport. The predicted water saturation and temperature distributions in the body and the thickness of frozen layer were compared with the experimental results using a porous bed composed of glass beads. 12 refs., 10 figs., 1 tab.

Effect of Structure Change on Radiation Crosslinking of Unsaturated Polyesters

International Nuclear Information System (INIS)

Ranogajec, F.

2006-01-01

During the course of crosslinking of unsaturated polyesters reacting system, that was liquid prior to reaction, gels, and becomes solid. Crosslinking reaction begins to be controlled by the change of the physical state of the system at an early stage of reaction. The kinetics can not be studied by the usual kinetical methods. In-source 60 C o gamma rays induced crosslinking of unsaturated polyester with styrene was followed directly and continuously by measuring electrical conductivity change. The results of extraction analysis proved good correlation between the change of electrical conductivity and the extent of curing. The gel content was inversely proportional to conductivity and free styrene content directly proportional to conductivity. DC-electrical conductivity has shown high sensitivity toward structural changes and enabled us to detect liquid-liquid transitions in unsaturated polyester. The upper liquid-liquid transition (T l ρ) is less known transition caused by a stepwise decrease of intramolecular short-range local order that remains above the glass and lower liquid-liquid transitions. The local order is based on secondary valent interactions and is enhanced by hydrogen bonding. The linear temperature dependence of the viscosity and dc electrical conductivity of unsaturated polyesters showed a change of slope caused by the (T l ρ). Those changes were the result of the diminishing of the local order (which includes several bond lengths) caused by breaking of the intramolecular interactions. The intramolecular nature of the (T l ρ) in the polyesters under consideration was proved by its insensitivity to crosslinking and dilution with solvents. In the corresponding temperature range, DSC thermograms shoved expected endothermic changes. The structure changes related to the (T l ρ) in the investigated polyesters were determined by 1 H NMR and NIR spectroscopy. The proton NMR indicated that the stepwise change in hydrogen bonding occurred in the

Effects of crude oil on water and tracer movement in the unsaturated and saturated zones.

Science.gov (United States)

Delin, Geoffrey N; Herkelrath, William N

2017-05-01

A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the periphery of the oil. Preferential flow resulted in reduced tracer interaction with the soil, adsorption, and dispersion and faster tracer movement in the oily zone than expected. Tracers were freely transported through the oily zone to the water table. Recharge calculations support the idea that the oil does not substantially affect recharge in the oily zone. This is an important result indicating that previous model-based assumptions of decreased recharge beneath the oil were incorrect. Results have important implications for modeling the fate and transport of dissolved contaminants at hydrocarbon spill sites. Published by Elsevier B.V.

Stable and radioactive isotopes in the study of the unsaturated soil zone

International Nuclear Information System (INIS)

1985-11-01

This publication brings together the main results with conclusions and recommendations on the usefulness of studies of the oxygen 18, deuterium and tritium in water in the unsaturated zone. A separate abstract was prepared for each of the 9 papers

Processing of Unsaturated Organic Acid Aerosols by Ozone

Science.gov (United States)

Aloisio, S.; Donaldson, D. J.; Eliason, T. L.; Cziczo, D.; Vaida, V.

2002-05-01

We present results of in-situ studies of the oxidative "processing" of organic aerosols composed of unsaturated organic compounds. Aerosol samples of 2-octenoic acid and undecylenic acid were exposed to approx. 10 mbar ozone in a room temperature, atmospheric pressure flow tube reactor. In-situ spectroscopic probing of the reaction mixture, as well as GC-MS analysis of the flow tube effluent, shows evidence of efficient oxidation of double bonds in the organic species, with production of gas-phase and aerosol phase ozonolysis products.

Unsuitability of using the DNPH-coated solid sorbent cartridge for determination of airborne unsaturated carbonyls

Science.gov (United States)

Ho, Steven Sai Hang; Ho, K. F.; Liu, W. D.; Lee, S. C.; Dai, W. T.; Cao, J. J.; Ip, H. S. S.

2011-01-01

Measurements of aldehydes and ketones are typically conducted by derivatization using sorbent cartridges coated with 2,4-dinitrophenylhydrazine (DNPH). The collected samples are eluted with acetonitrile and analyzed by high-pressure liquid chromatography coupled with an ultra-violet detector (HPLC/UV). This paper intends to examine artifacts about its suitability in identification of unsaturated carbonyls. Kinetic tests for acrolein, crotonaldehyde, methacrolein and methyl vinyl ketone (MVK) showed formations of carbonyl-DNP-hydrazone during sampling, which could further react with DNPH, resulting in undesired UV absorption products [e.g., carbonyl-DNP-hydrazone-DNPH (dimer) and 2(carbonyl-DNP-hydrazone)-DNPH (trimer)]. The dimerization and trimerization occurred for acrolein and MVK whereas only dimerization for crotonaldehyde and methacrolein. The polymerization products undoubtedly affect the integrity of the chromatogram, leading to misidentification and inaccurate quantification. Whether precautions taken during sampling and/or sample treatment could avoid or minimize this artifact has not been thoughtfully investigated. More often, such artifacts are usually overlooked by scientists when the data are reported.

Chemical and Isotopes study of pollutants transport through unsaturated zone in Damascus oasis (Syria)

International Nuclear Information System (INIS)

Abou Zakhem, B.; Hafez, R.

2011-08-01

The primary objectives of this study were to determine the hydrochemical and isotopic characteristics of groundwater and to study vertical transport processes for trace elements through the unsaturated zone, from the surface water into the groundwater system. A third objective is to identifying the importance of the unsaturated zone in protecting groundwater from contamination. Distribution of trace elements, including Cu, Pb, Cr, Cd, Zn and As in the soil with depth were studied. Mineralogy was investigated using X-Ray diffraction techniques and granulometry in three drilled soil profile (KA, KB and KS) in Damascus Oasis, which indicated that the soil consists mainly of calcite, a mineral that has the ability to bind some of the trace elements. Measurement of nitrate concentrations in groundwater permitted an investigation of the urban, industrial and agricultural pollution in the Oasis, in particular, in the eastern part of Damascus city and in the north of Oasis where the irrigation by treated wastewater is applied. Depending on the chemical characteristics of the studied trace elements and soil conditions, these elements have high concentrations in the upper part of the soil (20-30 cm depth), due to absorption by clay minerals and organic matter. These high concentrations represent pollution by leather industries (tannery) in the area. The trace element concentrations decrease towards the east in parallel with river flow direction. The lower part of profiles show low trace element concentrations, below the international permitted limit. The low concentrations of trace elements in groundwater which are also below the international limit, indicates no pollution is presented. The isotopic composition of shallow groundwater indicates the underground recharge, originated from the Anti-Lebanon Mountain, is more significant than the direct recharge through unsaturated zone. It is concluded the unsaturated zone and the decrease of groundwater levels have played an

Effects of thermal vapor diffusion on seasonal dynamics of water in the unsaturated zone

Science.gov (United States)

Milly, Paul C.D.

1996-01-01

The response of water in the unsaturated zone to seasonal changes of temperature (T) is determined analytically using the theory of nonisothermal water transport in porous media, and the solutions are tested against field observations of moisture potential and bomb fallout isotopic (36Cl and 3H) concentrations. Seasonally varying land surface temperatures and the resulting subsurface temperature gradients induce thermal vapor diffusion. The annual mean vertical temperature gradient is close to zero; however, the annual mean thermal vapor flux is downward, because the temperature‐dependent vapor diffusion coefficient is larger, on average, during downward diffusion (occurring at high T) than during upward diffusion (low T). The annual mean thermal vapor flux is shown to decay exponentially with depth; the depth (about 1 m) at which it decays to e−1of its surface value is one half of the corresponding decay depth for the amplitude of seasonal temperature changes. This depth‐dependent annual mean flux is effectively a source of water, which must be balanced by a flux divergence associated with other transport processes. In a relatively humid environment the liquid fluxes greatly exceed the thermal vapor fluxes, so such a balance is readily achieved without measurable effect on the dynamics of water in the unsaturated zone. However, if the mean vertical water flux through the unsaturated zone is very small (theoretical prediction is supported by long‐term field measurements in the Chihuahuan Desert. The analysis also makes predictions, confirmed by the field observations, regarding the seasonal variations of matric potential at a given depth. The conceptual model of unsaturated zone water transport developed here implies the possibility of near‐surface trapping of any aqueous constituent introduced at the surface.

Heterogeneous IP Ecosystem enabling Reuse (HIER)

Science.gov (United States)

2017-03-22

HIER project, DARPA also established additional concepts in the formation of the Common Heterogeneous Integration and IP Reuse Strategies (CHIPS...would need a major change to  business model to offer  Hard  or Soft IP – So CHIPS program can be a better fit to these firms • DoD‐Contractor IP pricing

Novel α, β-Unsaturated Sophoridinic Derivatives: Design, Synthesis, Molecular Docking and Anti-Cancer Activities

Directory of Open Access Journals (Sweden)

Yiming Xu

2017-11-01

Full Text Available Using sophoridine 1 and chalcone 3 as the lead compounds, a series of novel α, β-unsaturated sophoridinic derivatives were designed, synthesized, and evaluated for their in vitro cytotoxicity. Structure-activity relationship (SAR analysis indicated that introduction of α, β-unsaturated ketone moiety and heterocyclic group might significantly enhance anticancer activity. Among the compounds, 2f and 2m exhibited potential effects against HepG-2 and CNE-2 human cancer cell lines. Furthermore, molecular docking studies were performed to understand possible docking sites of the molecules on the target proteins and the mode of binding. This work provides a theoretical basis for structural optimizations and exploring anticancer pathways of this kind of compound.

Predicting unsaturated zone nitrogen mass balances in agricultural settings of the United States

Science.gov (United States)

Nolan, Bernard T.; Puckett, Larry J.; Ma, Liwang; Green, Christopher T.; Bayless, E. Randall; Malone, Robert W.

2009-01-01

Unsaturated zone N fate and transport were evaluated at four sites to identify the predominant pathways of N cycling: an almond [Prunus dulcis (Mill.) D.A. Webb] orchard and cornfield (Zea mays L.) in the lower Merced River study basin, California; and corn–soybean [Glycine max (L.) Merr.] rotations in study basins at Maple Creek, Nebraska, and at Morgan Creek, Maryland. We used inverse modeling with a new version of the Root Zone Water Quality Model (RZWQM2) to estimate soil hydraulic and nitrogen transformation parameters throughout the unsaturated zone; previous versions were limited to 3-m depth and relied on manual calibration. The overall goal of the modeling was to derive unsaturated zone N mass balances for the four sites. RZWQM2 showed promise for deeper simulation profiles. Relative root mean square error (RRMSE) values for predicted and observed nitrate concentrations in lysimeters were 0.40 and 0.52 for California (6.5 m depth) and Nebraska (10 m), respectively, and index of agreement (d) values were 0.60 and 0.71 (d varies between 0 and 1, with higher values indicating better agreement). For the shallow simulation profile (1 m) in Maryland, RRMSE and d for nitrate were 0.22 and 0.86, respectively. Except for Nebraska, predictions of average nitrate concentration at the bottom of the simulation profile agreed reasonably well with measured concentrations in monitoring wells. The largest additions of N were predicted to come from inorganic fertilizer (153–195 kg N ha−1 yr−1 in California) and N fixation (99 and 131 kg N ha−1 yr−1 in Maryland and Nebraska, respectively). Predicted N losses occurred primarily through plant uptake (144–237 kg N ha−1 yr−1) and deep seepage out of the profile (56–102 kg N ha−1 yr−1). Large reservoirs of organic N (up to 17,500 kg N ha−1 m−1 at Nebraska) were predicted to reside in the unsaturated zone, which has implications for potential future transfer of nitrate to groundwater.

Quantifying water flow and retention in an unsaturated fracture-facial domain

Science.gov (United States)

Nimmo, John R.; Malek-Mohammadi, Siamak

2015-01-01

Hydrologically significant flow and storage of water occur in macropores and fractures that are only partially filled. To accommodate such processes in flow models, we propose a three-domain framework. Two of the domains correspond to water flow and water storage in a fracture-facial region, in addition to the third domain of matrix water. The fracture-facial region, typically within a fraction of a millimeter of the fracture wall, includes a flowing phase whose fullness is determined by the availability and flux of preferentially flowing water, and a static storage portion whose fullness is determined by the local matric potential. The flow domain can be modeled with the source-responsive preferential flow model, and the roughness-storage domain can be modeled with capillary relations applied on the fracture-facial area. The matrix domain is treated using traditional unsaturated flow theory. We tested the model with application to the hydrology of the Chalk formation in southern England, coherently linking hydrologic information including recharge estimates, streamflow, water table fluctuation, imaging by electron microscopy, and surface roughness. The quantitative consistency of the three-domain matrix-microcavity-film model with this body of diverse data supports the hypothesized distinctions and active mechanisms of the three domains and establishes the usefulness of this framework.

Dissipative particle dynamics simulation of fluid motion through an unsaturated fracture and fracture junction

International Nuclear Information System (INIS)

Liu Moubin; Meakin, Paul; Huang Hai

2007-01-01

Multiphase fluid motion in unsaturated fractures and fracture networks involves complicated fluid dynamics, which is difficult to model using grid-based continuum methods. In this paper, the application of dissipative particle dynamics (DPD), a relatively new mesoscale method to simulate fluid motion in unsaturated fractures is described. Unlike the conventional DPD method that employs a purely repulsive conservative (non-dissipative) particle-particle interaction to simulate the behavior of gases, we used conservative particle-particle interactions that combine short-range repulsive and long-range attractive interactions. This new conservative particle-particle interaction allows the behavior of multiphase systems consisting of gases, liquids and solids to be simulated. Our simulation results demonstrate that, for a fracture with flat parallel walls, the DPD method with the new interaction potential function is able to reproduce the hydrodynamic behavior of fully saturated flow, and various unsaturated flow modes including thin film flow, wetting and non-wetting flow. During simulations of flow through a fracture junction, the fracture junction can be fully or partially saturated depending on the wetting property of the fluid, the injection rate and the geometry of the fracture junction. Flow mode switching from a fully saturated flow to a thin film flow can also be observed in the fracture junction

Graphene oxide-facilitated transport of levofloxacin and ciprofloxacin in saturated and unsaturated porous media.

Science.gov (United States)

Sun, Kaixuan; Dong, Shunan; Sun, Yuanyuan; Gao, Bin; Du, Wenchao; Xu, Hongxia; Wu, Jichun

2018-04-15

In this work, effects of graphene oxide (GO) on the co-transport of the two typical Fluoroquinolones (FQs) - levofloxacin (LEV) and ciprofloxacin (CIP) in saturated and unsaturated quartz sand media were studied. The adsorption isotherms showed that GO had much larger sorption capacities to LEV and CIP than sand with the largest Langmuir adsorption capacity of 409 mg g -1 (CIP-GO); while the sorption affinity of the two FQs onto the two adsorbents might follow the order of CIP-sand > LEV-sand > LEV-GO > CIP-GO. GO promoted the mobility of the two FQs in both saturated and unsaturated porous media due to its strong mobility and sorption capacity. The GO-bound LEV/CIP was responsible for the LEV/CIP transport in the porous media, and transport of GO-bound FQs increased with the increasing of initial GO concentration. Under unsaturated conditions, moisture showed little effect on the transport of GO-bound CIP; however, the mobility of GO-bound LEV reduced with the decreasing of moisture content, suggesting the transport of adsorbed LEV from GO to air-water interface. GO sorption reduced the antibacterial ability of the two FQs, but they were still effective in inhibiting E. coli growth. Copyright © 2018 Elsevier B.V. All rights reserved.

The Impact of Organo-Mineral Complexation on Mineral Weathering in the Soil Zone under Unsaturated Conditions

Science.gov (United States)

Michael, H. A.; Tan, F.; Yoo, K.; Imhoff, P. T.

2017-12-01

While organo-mineral complexes can protect organic matter (OM) from biodegradation, their impact on soil mineral weathering is not clear. Previous bench-scale experiments that focused on specific OM and minerals showed that the adsorption of OM to mineral surfaces accelerates the dissolution of some minerals. However, the impact of natural organo-mineral complexes on mineral dissolution under unsaturated conditions is not well known. In this study, soil samples prepared from an undisturbed forest site were used to determine mineral weathering rates under differing conditions of OM sorption to minerals. Two types of soil samples were generated: 1) soil with OM (C horizon soil from 84-100cm depth), and 2) soil without OM (the same soil as in 1) but with OM removed by heating to 350°for 24 h). Soil samples were column-packed and subjected to intermittent infiltration and drainage to mimic natural rainfall events. Each soil sample type was run in duplicate. The unsaturated condition was created by applying gas pressure to the column, and the unsaturated chemical weathering rates during each cycle were calculated from the effluent concentrations. During a single cycle, when applying the same gas pressure, soils with OM retained more moisture than OM-removed media, indicating increased water retention capacity under the impact of OM. This is consistent with the water retention data measured by evaporation experiments (HYPROP) and the dew point method (WP4C Potential Meter). Correspondingly, silicon (Si) denudation rates indicated that dissolution of silicate minerals was 2-4 times higher in OM soils, suggesting that organo-mineral complexes accelerate mineral dissolution under unsaturated conditions. When combining data from all cycles, the results showed that Si denudation rates were positively related to soil water content: denundation rate increased with increasing water content. Therefore, natural mineral chemical weathering under unsaturated conditions, while

Isotopic constraints on heterogeneous sulfate production in Beijing haze

Directory of Open Access Journals (Sweden)

P. He

2018-04-01

Full Text Available Discerning mechanisms of sulfate formation during fine-particle pollution (referred to as haze hereafter in Beijing is important for understanding the rapid evolution of haze and for developing cost-effective air pollution mitigation strategies. Here we present observations of the oxygen-17 excess of PM2.5 sulfate (Δ17O(SO42− collected in Beijing haze from October 2014 to January 2015 to constrain possible sulfate formation pathways. Throughout the sampling campaign, the 12-hourly averaged PM2.5 concentrations ranged from 16 to 323 µg m−3 with a mean of (141  ±  88 (1σ µg m−3, with SO42− representing 8–25 % of PM2.5 mass. The observed Δ17O(SO42− varied from 0.1 to 1.6 ‰ with a mean of (0.9  ±  0.3 ‰. Δ17O(SO42− increased with PM2.5 levels in October 2014 while the opposite trend was observed from November 2014 to January 2015. Our estimate suggested that in-cloud reactions dominated sulfate production on polluted days (PDs, PM2.5  ≥  75 µg m−3 of Case II in October 2014 due to the relatively high cloud liquid water content, with a fractional contribution of up to 68 %. During PDs of Cases I and III–V, heterogeneous sulfate production (Phet was estimated to contribute 41–54 % to total sulfate formation with a mean of (48  ±  5 %. For the specific mechanisms of heterogeneous oxidation of SO2, chemical reaction kinetics calculations suggested S(IV ( =  SO2 ⚫ H2O + HSO3−  +  SO32− oxidation by H2O2 in aerosol water accounted for 5–13 % of Phet. The relative importance of heterogeneous sulfate production by other mechanisms was constrained by our observed Δ17O(SO42−. Heterogeneous sulfate production via S(IV oxidation by O3 was estimated to contribute 21–22 % of Phet on average. Heterogeneous sulfate production pathways that result in zero-Δ17O(SO42−, such as S(IV oxidation by NO2 in aerosol water and/or by O2 via a

Numerical study of damage in unsaturated Geological and Engineered barriers

International Nuclear Information System (INIS)

Arson, C.; Gatmiri, B.

2011-01-01

The theoretical framework of a damage model dedicated to non-isothermal unsaturated porous media is presented. The damage variable is a second-order tensor, and the model is formulated in independent state variables. The behavior laws are derived from a postulated expression of Helmholtz free energy. The damaged rigidities are computed by applying the Principle of Equivalent Elastic Energy (PEEE). Internal length parameters are introduced in the expressions of liquid water and vapor conductivities, to account for cracking effects on fluid flows. The damage model has been implemented in Θ-Stock Finite Element program. The mechanical aspect of the damage model is validated by simulating a triaxial compression test on a dry isothermal brittle material. Then, a sophisticated model of nuclear waste disposal, involving two non-isothermal unsaturated porous media, is reproduced. The results obtained in elasticity are in good agreement with the results presented in the corresponding reference article. A parametric study on initial damage is then performed to assess the influence of the Excavated Damaged Zone (EDZ) on the response of the nuclear waste repository during the heating phase. The trends meet the theoretical expectations. (authors)

Adaptive probabilistic collocation based Kalman filter for unsaturated flow problem

Science.gov (United States)

Man, J.; Li, W.; Zeng, L.; Wu, L.

2015-12-01

The ensemble Kalman filter (EnKF) has gained popularity in hydrological data assimilation problems. As a Monte Carlo based method, a relatively large ensemble size is usually required to guarantee the accuracy. As an alternative approach, the probabilistic collocation based Kalman filter (PCKF) employs the Polynomial Chaos to approximate the original system. In this way, the sampling error can be reduced. However, PCKF suffers from the so called "cure of dimensionality". When the system nonlinearity is strong and number of parameters is large, PCKF is even more computationally expensive than EnKF. Motivated by recent developments in uncertainty quantification, we propose a restart adaptive probabilistic collocation based Kalman filter (RAPCKF) for data assimilation in unsaturated flow problem. During the implementation of RAPCKF, the important parameters are identified and active PCE basis functions are adaptively selected. The "restart" technology is used to alleviate the inconsistency between model parameters and states. The performance of RAPCKF is tested by unsaturated flow numerical cases. It is shown that RAPCKF is more efficient than EnKF with the same computational cost. Compared with the traditional PCKF, the RAPCKF is more applicable in strongly nonlinear and high dimensional problems.

Nuclear-waste isolation in the unsaturated zone of arid regions

International Nuclear Information System (INIS)

Wollenberg, H.A.; Wang, J.S.Y.; Korbin, G.

1982-05-01

The vadose zone in arid regions is considered as a possible environment for geologic isolation of nuclear waste. There are several topographic and lithologic combinations in the vadose zone of arid regions that may lend themselves to waste isolation considerations. In some cases, topographic highs such as mesas and interbasin ranges - comprised of several rock types, may contain essentially dry or partially saturated conditions favorable for isolation. The adjacent basins, especially in the far western and southwestern US, may have no surface or subsurface hydrologic connections with systems ultimately leading to the ocean. Some rock types may have the favorable characteristics of very low permeability and contain appropriate minerals for the strong chemical retardation of radionuclides. Environments exhibiting these hydrologic and geochemical attributes are the areas underlain by tuffaceous rocks, relatively common in the Basin and Range geomorphic province. Adjacent valley areas, where tuffaceous debris makes up a significant component of valley fill alluvium, may also contain thick zones of unsaturated material, and as such also lend themselves to strong consideration as respository environments. This paper summarizes the aspects of nuclear waste isolation in unsaturated regimes in alluvial-filled valleys and tuffaceous rocks of the Basin and Range province

A borehole instrumentation program for characterization of unsaturated-zone percolation

International Nuclear Information System (INIS)

Kume, J.; Rousseau, J.P.

1994-01-01

A borehole instrumentation and monitoring program has been designed by the US Geological Survey to support site characterization of unsaturated-zone percolation at Yucca Mountain, Nye County, Nevada. This program provides a means of defining the unsaturated-zone fluid flow (liquid and gas) potential field in a setting that incorporates large-scale stratigraphic and structural features, and the influences of geothermal heat flow and atmospheric pressure changes. Data derived from this program will be used to evaluate the suitability of Yucca Mountain as a mined geologic-repository for the storage of high-level, radioactive waste. These data include in-situ temperature, pneumatic pressure, and water potential. In addition, the instrumentation program provides facilities for gas-sampling, gas-tracer diffusion testing, water-injection testing, water-level monitoring, neutron moisture-meter monitoring, temperature profiling, and in-situ recalibration of the downhole sensors. The program included testing and development of: (1) precision sensors for measurement; (2) a downhole instrumentation-station-apparatus to house the sensors, recalibrate sensors in-situ, and allow access to instrument stations for other testing purposes; and (3) surface-based support and instrumentation facilities

Natural Length Scales Shape Liquid Phase Continuity in Unsaturated Flows

Science.gov (United States)

Assouline, S.; Lehmann, P. G.; Or, D.

2015-12-01

Unsaturated flows supporting soil evaporation and internal drainage play an important role in various hydrologic and climatic processes manifested at a wide range of scales. We study inherent natural length scales that govern these flow processes and constrain the spatial range of their representation by continuum models. These inherent length scales reflect interactions between intrinsic porous medium properties that affect liquid phase continuity, and the interplay among forces that drive and resist unsaturated flow. We have defined an intrinsic length scale for hydraulic continuity based on pore size distribution that controls soil evaporation dynamics (i.e., stage 1 to stage 2 transition). This simple metric may be used to delineate upper bounds for regional evaporative losses or the depth of soil-atmosphere interactions (in the absence of plants). A similar length scale governs the dynamics of internal redistribution towards attainment of field capacity, again through its effect on hydraulic continuity in the draining porous medium. The study provides a framework for guiding numerical and mathematical models for capillary flows across different scales considering the necessary conditions for coexistence of stationarity (REV), hydraulic continuity and intrinsic capillary gradients.

Water Drainage from Unsaturated Soils in a Centrifuge Permeameter

Science.gov (United States)

Ornelas, G.; McCartney, J.; Zhang, M.

2013-12-01

This study involves an analysis of water drainage from an initially saturated silt layer in a centrifuge permeameter to evaluate the hydraulic properties of the soil layer in unsaturated conditions up to the point where the water phase becomes discontinuous. These properties include the soil water retention curve (SWRC) and the hydraulic conductivity function (HCF). The hydraulic properties of unsaturated silt are used in soil-atmosphere interaction models that take into account the role of infiltration and evaporation of water from soils due to atmospheric interaction. These models are often applied in slope stability analyses, landfill cover design, aquifer recharge analyses, and agricultural engineering. The hydraulic properties are also relevant to recent research concerning geothermal heating and cooling, as they can be used to assess the insulating effects of soil around underground heat exchangers. This study employs a high-speed geotechnical centrifuge to increase the self-weight of a compacted silt specimen atop a filter plate. Under a centrifuge acceleration of N times earth's gravity, the concept of geometric similitude indicates that the water flow process in a small-scale soil layer will be similar to those in a soil layer in the field that is N times thicker. The centrifuge acceleration also results in an increase in the hydraulic gradient across the silt specimen, which causes water to flow out of the pores following Darcy's law. The drainage test was performed until the rate of liquid water flow out of the soil layer slowed to a negligible level, which corresponds to the transition point at which further water flow can only occur due to water vapor diffusion following Fick's law. The data from the drainage test in the centrifuge were used to determine the SWRC and HCF at different depths in the silt specimen, which compared well with similar properties defined using other laboratory tests. The transition point at which liquid water flow stopped (and

Modeling one-dimensional unsaturated flow at the Rocky Flats Environmental Technology Site near Golden, Colorado

International Nuclear Information System (INIS)

Thompson, J.S.; Zeiler, R.M.

1995-01-01

A field investigation characterizing contamination at the Rocky Flats Plant (Rocky Flats Environmental Technology Site) near Golden, Colorado revealed unexpectedly high moisture contents in the unsaturated soil column (vadose zone) beneath several of the Plant's Waste Water Treatment Plant (WWTP) sludge drying beds. Because these beds were seldom in use, researchers had hypothesized that the water required to maintain the saturated conditions observed beneath several of the sludge drying beds was coming from sources other than the beds themselves. In an effort to substantiate this hypothesis, a one-dimensional physically-based unsaturated flow model was utilized to simulate the vertical movement of moisture from the sludge drying beds into the unsaturated soil column below. The model was run to simulate vertical flow over a two-year period and results indicated that no significant changes from initial conditions were apparent. This evidence supports the hypothesis that the high moisture contents found beneath the sludge drying beds are being fed by sources other than infiltration of sludge applied to the beds themselves. This paper presents the details of the simulation and provides further evidence of the hypothesized flow regime

A novel definition of the overall hyper-wiener index for unsaturated hydrocarbons.

Science.gov (United States)

Li, Xinhua; Hu, Maolin; Xiao, Hongping

2004-01-01

By replacing the distances between pairs of vertices with the relative distances, we define a novel overall hyper-Wiener index (NOR); the novel overall hyper-Wiener index extends the usefulness of the hyper-Wiener index and the overall hyper-Wiener index to unsaturated hydrocarbons.

TRPA1-dependent reversible opening of tight junction by natural compounds with an α,β-unsaturated moiety and capsaicin.

Science.gov (United States)

Kanda, Yusuke; Yamasaki, Youhei; Sasaki-Yamaguchi, Yoshie; Ida-Koga, Noriko; Kamisuki, Shinji; Sugawara, Fumio; Nagumo, Yoko; Usui, Takeo

2018-02-02

The delivery of hydrophilic macromolecules runs into difficulties such as penetration of the cell membrane lipid bilayer. Our prior experiment demonstrated that capsaicin induces the reversible opening of tight junctions (TJs) and enhances the delivery of hydrophilic macromolecules through a paracellular route. Herein, we screened paracellular permeability enhancers other than capsaicin. As TJ opening by capsaicin is associated with Ca 2+ influx, we first screened the compounds that induce Ca 2+ influx in layered MDCK II cells, and then we determined the compounds' abilities to open TJs. Our results identified several natural compounds with α,β-unsaturated moiety. A structure-activity relationship (SAR) analysis and the results of pretreatment with reducing reagent DTT suggested the importance of α,β-unsaturated moiety. We also examined the underlying mechanisms, and our findings suggest that the actin reorganization seen in capsaicin treatment is important for the reversibility of TJ opening. Furthermore, our analyses revealed that TRPA1 is involved in the Ca 2+ influx and TJ permeability increase not only by an α,β-unsaturated compound but also by capsaicin. Our results indicate that the α,β-unsaturated moiety can be a potent pharmacophore for TJ opening.

Characterisation, quantification and modelling of CO2 transport and interactions in a carbonate vadose zone: application to a CO2 diffusive leakage in a geological sequestration context

International Nuclear Information System (INIS)

Cohen, Gregory

2013-01-01

Global warming is related to atmospheric greenhouse gas concentration increase and especially anthropogenic CO 2 emissions. Geologic sequestration has the potential capacity and the longevity to significantly diminish anthropogenic CO 2 emissions. This sequestration in deep geological formation induces leakage risks from the geological reservoir. Several leakage scenarios have been imagined. Since it could continue for a long period, inducing environmental issues and risks for human, the scenario of a diffusive leakage is the most worrying. Thus, monitoring tools and protocols are needed to set up a near-surface monitoring plan. The present thesis deals with this problematic. The aims are the characterisation, the quantification and the modelling of transport and interactions of CO 2 in a carbonate unsaturated zone. This was achieved following an experimental approach on a natural pilot site in Saint-Emilion (Gironde, France), where diffusive gas leakage experiments were set up in a carbonate unsaturated zone. Different aspects were investigated during the study: natural pilot site description and instrumentation; the physical and chemical characterisation of carbonate reservoir heterogeneity; the natural functioning of the carbonate unsaturated zone and especially the set-up of a CO 2 concentrations baseline; the characterisation of gas plume extension following induced diffusive leakage in the carbonate unsaturated zone and the study of gas-water-rock interactions during a CO 2 diffusive leakage in a carbonate unsaturated zone through numerical simulations. The results show the importance of the carbonate reservoir heterogeneity characterisation as well as the sampling and analysing methods for the different phases. The baseline set-up is of main interest since it allows discrimination between the induced and the natural CO 2 concentrations variations. The transfer of CO 2 in a carbonate unsaturated zone is varying in function of physical and chemical properties

Sample size choices for XRCT scanning of highly unsaturated soil mixtures

Directory of Open Access Journals (Sweden)

Smith Jonathan C.

2016-01-01

Full Text Available Highly unsaturated soil mixtures (clay, sand and gravel are used as building materials in many parts of the world, and there is increasing interest in understanding their mechanical and hydraulic behaviour. In the laboratory, x-ray computed tomography (XRCT is becoming more widely used to investigate the microstructures of soils, however a crucial issue for such investigations is the choice of sample size, especially concerning the scanning of soil mixtures where there will be a range of particle and void sizes. In this paper we present a discussion (centred around a new set of XRCT scans on sample sizing for scanning of samples comprising soil mixtures, where a balance has to be made between realistic representation of the soil components and the desire for high resolution scanning, We also comment on the appropriateness of differing sample sizes in comparison to sample sizes used for other geotechnical testing. Void size distributions for the samples are presented and from these some hypotheses are made as to the roles of inter- and intra-aggregate voids in the mechanical behaviour of highly unsaturated soils.

Fully Biobased Unsaturated Aliphatic Polyesters from Renewable Resources : Enzymatic Synthesis, Characterization, and Properties

NARCIS (Netherlands)

Jiang, Yi; Alberda van Ekenstein, Gerhard; Woortman, Albert J. J.; Loos, Katja

2014-01-01

Fully biobased saturated and unsaturated aliphatic polyesters and oligoesters are successfully prepared by Candida antarctica lipase B (CALB)-catalyzed polycondensations of succinate, itaconate, and 1,4-butanediol. The effects of monomer substrates and polymerization methods on enzymatic

An evaluation of the active fracture concept with modeling unsaturated flow and transport in a fractured meter-sized block of rock

International Nuclear Information System (INIS)

Seol, Yongkoo; Kneafsey, Timothy J.; Ito, Kazumasa

2003-01-01

Numerical simulation is an effective and economical tool for optimally designing laboratory experiments and deriving practical experimental conditions. We executed a detailed numerical simulation study to examine the active fracture concept (AFC, Liu et al., 1998) using a cubic meter-sized block model. The numerical simulations for this study were performed by applying various experimental conditions, including different bottom flow boundaries, varying injection rates, and different fracture-matrix interaction (by increasing absolute matrix permeability at the fracture matrix boundary) for a larger fracture interaction under transient or balanced-state flow regimes. Two conceptual block models were developed based on different numerical approaches: a two-dimensional discrete-fracture-network model (DFNM) and a one-dimensional dual continuum model (DCM). The DFNM was used as a surrogate for a natural block to produce synthetic breakthrough curves of water and tracer concentration under transient or balanced-state conditions. The DCM is the approach typically used for the Yucca Mountain Project because of its computational efficiency. The AFC was incorporated into the DCM to capture heterogeneous flow patterns that occur in unsaturated fractured rocks. The simulation results from the DCM were compared with the results from the DFNM to determine whether the DCM could predict the water flow and tracer transport observed in the DFNM at the scale of the experiment. It was found that implementing the AFC in the DCM improved the prediction of unsaturated flow and that the flow and transport experiments with low injection rates in the DFNM were compared better with the AFC implemented DCM at the meter scale. However, the estimated AFC parameter varied from 0.38 to 1.0 with different flow conditions, suggesting that the AFC parameter was not a sufficient to fully capture the complexity of the flow processes in a one meter sized discrete fracture network

Formation of equiaxed crystal structures in directionally solidified Al-Si alloys using Nb-based heterogeneous nuclei

Science.gov (United States)

Bolzoni, Leandro; Xia, Mingxu; Babu, Nadendla Hari

2016-01-01

The design of chemical compositions containing potent nuclei for the enhancement of heterogeneous nucleation in aluminium, especially cast alloys such as Al-Si alloys, is a matter of importance in order to achieve homogeneous properties in castings with complex geometries. We identified that Al3Nb/NbB2 compounds are effective heterogeneous nuclei and are successfully produced in the form of Al-2Nb-xB (x = 0.5, 1 and 2) master alloys. Our study shows that the inoculation of Al-10Si braze alloy with these compounds effectively promotes the heterogeneous nucleation of primary α-Al crystals and reduces the undercooling needed for solidification to take place. Moreover, we present evidences that these Nb-based compounds prevent the growth of columnar crystals and permit to obtain, for the first time, fine and equiaxed crystals in directionally solidified Al-10Si braze alloy. As a consequence of the potent heterogeneous particles, the size of the α-Al crystals was found to be less dependent on the processing conditions, especially the thermal gradient. Finally, we also demonstrate that the enhanced nucleation leads to the refinement of secondary phases such as eutectic silicon and primary silicon particles. PMID:28008967

Nanoscale-Agglomerate-Mediated Heterogeneous Nucleation.

Science.gov (United States)

Cha, Hyeongyun; Wu, Alex; Kim, Moon-Kyung; Saigusa, Kosuke; Liu, Aihua; Miljkovic, Nenad

2017-12-13

Water vapor condensation on hydrophobic surfaces has received much attention due to its ability to rapidly shed water droplets and enhance heat transfer, anti-icing, water harvesting, energy harvesting, and self-cleaning performance. However, the mechanism of heterogeneous nucleation on hydrophobic surfaces remains poorly understood and is attributed to defects in the hydrophobic coating exposing the high surface energy substrate. Here, we observe the formation of high surface energy nanoscale agglomerates on hydrophobic coatings after condensation/evaporation cycles in ambient conditions. To investigate the deposition dynamics, we studied the nanoscale agglomerates as a function of condensation/evaporation cycles via optical and field emission scanning electron microscopy (FESEM), microgoniometric contact angle measurements, nucleation statistics, and energy dispersive X-ray spectroscopy (EDS). The FESEM and EDS results indicated that the nanoscale agglomerates stem from absorption of sulfuric acid based aerosol particles inside the droplet and adsorption of volatile organic compounds such as methanethiol (CH 3 SH), dimethyl disulfide (CH 3 SSCH), and dimethyl trisulfide (CH 3 SSSCH 3 ) on the liquid-vapor interface during water vapor condensation, which act as preferential sites for heterogeneous nucleation after evaporation. The insights gained from this study elucidate fundamental aspects governing the behavior of both short- and long-term heterogeneous nucleation on hydrophobic surfaces, suggest previously unexplored microfabrication and air purification techniques, and present insights into the challenges facing the development of durable dropwise condensing surfaces.

A Mass Conservative Numerical Solution for Two-Phase Flow in Porous Media With Application to Unsaturated Flow

DEFF Research Database (Denmark)

Celia, Michael A.; Binning, Philip John

1992-01-01

that the algorithm produces solutions that are essentially mass conservative and oscillation free, even in the presence of steep infiltrating fronts. When the algorithm is applied to the case of air and water flow in unsaturated soils, numerical results confirm the conditions under which Richards's equation is valid....... Numerical results also demonstrate the potential importance of air phase advection when considering contaminant transport in unsaturated soils. Comparison to several other numerical algorithms shows that the modified Picard approach offers robust, mass conservative solutions to the general equations...

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

Directory of Open Access Journals (Sweden)

Saeed Tourchi

2015-04-01

Full Text Available A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existing model for saturated clays originally proposed by the authors. The saturated clays model was formulated in the framework of critical state soil mechanics and modified Cam-clay model. The existing model has been generalized to simulate the experimentally observed behavior of unsaturated clays by introducing Bishop's stress and suction as independent stress parameters and modifying the hardening rule and yield criterion to take into account the role of suction. Also, according to previous studies, an increase in temperature causes a reduction in specific volume. A reduction in suction (wetting for a given confining stress may induce an irreversible volumetric compression (collapse. Thus an increase in suction (drying raises a specific volume i.e. the movement of normal consolidation line (NCL to higher values of void ratio. However, some experimental data confirm the assumption that this reduction is dependent on the stress level of soil element. A generalized approach considering the effect of stress level on the magnitude of clays thermal dependency in compression plane is proposed in this study. The number of modeling parameters is kept to a minimum, and they all have clear physical interpretations, to facilitate the usefulness of model for practical applications. A step-by-step procedure used for parameter calibration is also described. The model is finally evaluated using a comprehensive set of experimental data for the thermo-mechanical behavior of unsaturated soils.

α,β-Unsaturated imines via Ru-catalyzed coupling of allylic alcohols and amines.

Science.gov (United States)

Rigoli, Jared W; Moyer, Sara A; Pearce, Simon D; Schomaker, Jennifer M

2012-03-07

A convenient synthesis of α,β-unsaturated imines requiring only an allylic alcohol, an amine and a Ru catalyst has been developed. The use of large excesses of oxidant and the purification of sensitive intermediates can be avoided.

Phase behavior and reactive transport of partial melt in heterogeneous mantle model

Science.gov (United States)

Jordan, J.; Hesse, M. A.

2013-12-01

The reactive transport of partial melt is the key process that leads to the chemical and physical differentiation of terrestrial planets and smaller celestial bodies. The essential role of the lithological heterogeneities during partial melting of the mantle is increasingly recognized. How far can enriched melts propagate while interacting with the ambient mantle? Can the melt flow emanating from a fertile heterogeneity be localized through a reactive infiltration feedback in a model without exogenous factors or contrived initial conditions? A full understanding of the role of heterogeneities requires reactive melt transport models that account for the phase behavior of major elements. Previous work on reactive transport in the mantle focuses on trace element partitioning; we present the first nonlinear chromatographic analysis of reactive melt transport in systems with binary solid solution. Our analysis shows that reactive melt transport in systems with binary solid solution leads to the formation of two separate reaction fronts: a slow melting/freezing front along which enthalpy change is dominant and a fast dissolution/precipitation front along which compositional changes are dominated by an ion-exchange process over enthalpy change. An intermediate state forms between these two fronts with a bulk-rock composition and enthalpy that are not necessarily bounded by the bulk-rock composition and enthalpy of either the enriched heterogeneity or the depleted ambient mantle. The formation of this intermediate state makes it difficult to anticipate the porosity changes and hence the stability of reaction fronts. Therefore, we develop a graphical representation for the solution that allows identification of the intermediate state by inspection, for all possible bulk-rock compositions and enthalpies of the heterogeneity and the ambient mantle. We apply the analysis to the partial melting of an enriched heterogeneity. This leads to the formation of moving precipitation

Leaching action of EJ-13 water on unirradiated UO2 surfaces under unsaturated conditions at 90 degree C: Interim report

International Nuclear Information System (INIS)

Wronkiewicz, D.J.; Bates, J.K.; Gerding, T.J.; Veleckis, E.; Tani, B.S.

1991-07-01

A set of experiments, based on the application of the Unsaturated Test method to the reaction of UO 2 with EJ-13 water, has been conducted over a period of 182.5 weeks. One half of the experiments have been terminated, while one half are still ongoing. Solutions that have dripped from UO 2 specimens have been analyzed for all experiments, while the reacted UO 2 surfaces have been examined for only the terminated experiments. A pulse of uranium release from the UO 2 solid, in conjunction with the formation of dehydrated schoepite on the surface of the UO 2 , was observed during the 39- to 96-week period. Thereafter, the uranium release decreased and a second set of secondary phases was observed. The latter phases incorporate cations from the EJ-13 water and include boltwoodite, uranophane, sklodowskite, compreignacite, and schoepite. The experiments are being continued to monitor for additional changes in solution composition and secondary phase formation, and have now reached the 319-week period. 9 refs., 17 figs., 25 tabs

Film thinning in unsaturated superfluid 4He films during persistent flow

International Nuclear Information System (INIS)

Ekholm, D.T.; Hallock, R.B.

1979-01-01

We report measurements of the thickness of unsaturated superfluid 4 He films in persistent flow as a function of persistent current velocity. Our results are in quantitative agreement with the predictions of Kontorovich, and thus disagree with the conclusion of Rudnick and coworkers that rho/sub s//rho has an enhanced velocity dependence in these films

Permeable barrier materials for strontium immobilization: Unsaturated flow apparatus determination of hydraulic conductivity -- Column sorption experiments

International Nuclear Information System (INIS)

Moody, T.E.; Conca, J.

1996-09-01

Selected materials were tested to emulate a permeable barrier and to examine the (1) capture efficiency of these materials relating to the immobilization of strontium-90 and hexavalent chromium (Cr 6+ ) in Hanford Site groundwater; and (2) hydraulic conductivity of the barrier material relative to the surrounding area. The emplacement method investigated was a permeable reactive barrier to treat contaminated groundwater as it passes through the barrier. The hydraulic conductivity function was measured for each material, and retardation column experiments were performed for each material. Measurements determining the hydraulic conductivity at unsaturated through saturated water content were executed using the Unsaturated Flow Apparatus

Hydrologic evaluation methodology for estimating water movement through the unsaturated zone at commercial low-level radioactive waste disposal site

Science.gov (United States)

Meyer, P.D.; Rockhold, M.L.; Nichols, W.E.; Gee, G.W.

1996-01-01

. Several computer simulation codes that were used in the examples (Chapter 6) are discussed with respect to this checklist. The codes used include HELP, UNSAT-H, and VAM3DCG.To provide a defensible estimate of water flow in a LLW disposal facility, the uncertainty associated with model predictions must be considered. Uncertainty arises because of the highly heterogeneous nature of most subsurface environments and the long time frame required in the analysis. Sources of uncertainty in hydrologic evaluation of the unsaturated zone and several approaches for analysis are discussed in Chapter 5. The methods of analysis discussed include a bounding approach, sensitivity analysis, and Monte Carlo simulation.To illustrate the application of the discussion in Chapters 2 through 5, two examples are presented in Chapter 6. The first example is of a below ground vault located in a humid environment. The second example looks at a shallow land burial facility located in an arid environment. The examples utilize actual site-specific data and realistic facility designs. The two examples illustrate the issues unique to humid and arid sites as well as the issues common to all LLW sites. Strategies for addressing the analytical difficulties arising in any complex hydrologic evaluation of the unsaturated zone are demonstrated.The report concludes with some final observations and recommendations.

In-situ fabrication of halloysite nanotubes/silica nano hybrid and its application in unsaturated polyester resin

Science.gov (United States)

Lin, Jing; Zhong, Bangchao; Jia, Zhixin; Hu, Dechao; Ding, Yong; Luo, Yuanfang; Jia, Demin

2017-06-01

Silica nanoparticles was in-situ grown on the surface of halloysite nanotubes (HNTs) by a facile one-step approach to prepare a unique nano-structured hybrid (HNTs-g-Silica). The structure, morphology and composition of HNTs-g-Silica were investigated. It was confirmed that silica nanoparticles with the diameter of 10-20 nm were chemically grafted through Sisbnd O bonds and uniformly dispersed onto the surface of HNTs, leading to the formation of nano-protrusions on the nanotube surface. Due to the significantly improved interface strength between HNTs-g-Silica and polymer matrix, HNTs-g-Silica effectively toughened unsaturated polyester resin (UPE) and endowed UPE with superior thermal stability compared to HNTs. Based on the unique hybrid architecture and the improved properties of UPE nanocomposites, it is envisioned that HNTs-g-Silica may be a promising filler for more high performance and functional polymers composites and the fabrication method may have implications in the synthesis of nano hybrid materials.

Three-dimensional cluster formation and structure in heterogeneous dose distribution of intensity modulated radiation therapy.

Science.gov (United States)

Chao, Ming; Wei, Jie; Narayanasamy, Ganesh; Yuan, Yading; Lo, Yeh-Chi; Peñagarícano, José A

2018-05-01

To investigate three-dimensional cluster structure and its correlation to clinical endpoint in heterogeneous dose distributions from intensity modulated radiation therapy. Twenty-five clinical plans from twenty-one head and neck (HN) patients were used for a phenomenological study of the cluster structure formed from the dose distributions of organs at risks (OARs) close to the planning target volumes (PTVs). Initially, OAR clusters were searched to examine the pattern consistence among ten HN patients and five clinically similar plans from another HN patient. Second, clusters of the esophagus from another ten HN patients were scrutinized to correlate their sizes to radiobiological parameters. Finally, an extensive Monte Carlo (MC) procedure was implemented to gain deeper insights into the behavioral properties of the cluster formation. Clinical studies showed that OAR clusters had drastic differences despite similar PTV coverage among different patients, and the radiobiological parameters failed to positively correlate with the cluster sizes. MC study demonstrated the inverse relationship between the cluster size and the cluster connectivity, and the nonlinear changes in cluster size with dose thresholds. In addition, the clusters were insensitive to the shape of OARs. The results demonstrated that the cluster size could serve as an insightful index of normal tissue damage. The clinical outcome of the same dose-volume might be potentially different. Copyright © 2018 Elsevier B.V. All rights reserved.

heteroHarvest: Harvesting Information from Heterogeneous Sources

DEFF Research Database (Denmark)

Qureshi, Pir Abdul Rasool; Memon, Nasrullah; Wiil, Uffe Kock

2011-01-01

The abundance of information regarding any topic makes the Internet a very good resource. Even though searching the Internet is very easy, what remains difficult is to automate the process of information extraction from the available online information due to the lack of structure and the diversity...... in the sharing methods. Most of the times, information is stored in different proprietary formats, complying with different standards and protocols which makes tasks like data mining and information harvesting very difficult. In this paper, an information harvesting tool (heteroHarvest) is presented...... with objectives to address these problems by filtering the useful information and then normalizing the information in a singular non hypertext format. Finally we describe the results of experimental evaluation. The results are found promising with an overall error rate equal to 6.5% across heterogeneous formats....

The porous surface model, a novel experimental system for online quantitative observation of microbial processes under unsaturated conditions

DEFF Research Database (Denmark)

Dechesne, Arnaud; Or, D.; Gulez, Gamze

2008-01-01

Water is arguably the most important constituent of microbial microhabitats due to its control of physical and physiological processes critical to microbial activity. In natural environments, bacteria often live on unsaturated surfaces, in thin (micrometric) liquid films. Nevertheless, no experim....... The PSM constitutes a tool uniquely adapted to study the influence of liquid film geometry on microbial processes. It should therefore contribute to uncovering mechanisms of microbial adaptation to unsaturated environments.......Water is arguably the most important constituent of microbial microhabitats due to its control of physical and physiological processes critical to microbial activity. In natural environments, bacteria often live on unsaturated surfaces, in thin (micrometric) liquid films. Nevertheless......, no experimental systems are available that allow real-time observation of bacterial processes in liquid films of controlled thickness. We propose a novel, inexpensive, easily operated experimental platform, termed the porous surface model (PSM) that enables quantitative real-time microscopic observations...

Quantifying geological uncertainty for flow and transport modeling in multi-modal heterogeneous formations

Science.gov (United States)

Feyen, Luc; Caers, Jef

2006-06-01

In this work, we address the problem of characterizing the heterogeneity and uncertainty of hydraulic properties for complex geological settings. Hereby, we distinguish between two scales of heterogeneity, namely the hydrofacies structure and the intrafacies variability of the hydraulic properties. We employ multiple-point geostatistics to characterize the hydrofacies architecture. The multiple-point statistics are borrowed from a training image that is designed to reflect the prior geological conceptualization. The intrafacies variability of the hydraulic properties is represented using conventional two-point correlation methods, more precisely, spatial covariance models under a multi-Gaussian spatial law. We address the different levels and sources of uncertainty in characterizing the subsurface heterogeneity, and explore their effect on groundwater flow and transport predictions. Typically, uncertainty is assessed by way of many images, termed realizations, of a fixed statistical model. However, in many cases, sampling from a fixed stochastic model does not adequately represent the space of uncertainty. It neglects the uncertainty related to the selection of the stochastic model and the estimation of its input parameters. We acknowledge the uncertainty inherent in the definition of the prior conceptual model of aquifer architecture and in the estimation of global statistics, anisotropy, and correlation scales. Spatial bootstrap is used to assess the uncertainty of the unknown statistical parameters. As an illustrative example, we employ a synthetic field that represents a fluvial setting consisting of an interconnected network of channel sands embedded within finer-grained floodplain material. For this highly non-stationary setting we quantify the groundwater flow and transport model prediction uncertainty for various levels of hydrogeological uncertainty. Results indicate the importance of accurately describing the facies geometry, especially for transport

Hydrogenation of the alpha,beta-Unsaturated Aldehydes Acrolein, Crotonaldehyde, and Prenal over Pt Single Crystals: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

Energy Technology Data Exchange (ETDEWEB)

Kliewer, C.J.; Somorjai, G.A.

2008-11-26

Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three {alpha},{beta}-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr aldehyde, 100 Torr hydrogen) in the temperature range of 295K to 415K. SFG-VS data showed that acrolein has mixed adsorption species of {eta}{sub 2}-di-{sigma}(CC)-trans, {eta}{sub 2}-di-{sigma}(CC)-cis as well as highly coordinated {eta}{sub 3} or {eta}{sub 4} species. Crotonaldehyde adsorbed to Pt(111) as {eta}{sub 2} surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the {eta}{sub 2} adsorption species, and became more highly coordinated as the temperature was raised to 415K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation 'cracking' product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotylalcohol.

Natural weathering in dry disposed ash dump: Insight from chemical, mineralogical and geochemical analysis of fresh and unsaturated drilled cores.

Science.gov (United States)

Akinyemi, S A; Akinlua, A; Gitari, W M; Khuse, N; Eze, P; Akinyeye, R O; Petrik, L F

2012-07-15

Some existing alternative applications of coal fly ash such as cement manufacturing; road construction; landfill; and concrete and waste stabilisation use fresh ash directly collected from coal-fired power generating stations. Thus, if the rate of usage continues, the demand for fresh ash for various applications will exceed supply and use of weathered dry disposed ash will become necessary alternative. As a result it's imperative to understand the chemistry and pH behaviour of some metals inherent in dry disposed fly ash. The bulk chemical composition as determined by XRF analysis showed that SiO2, Al2O3 and Fe2O3 were the major oxides in fresh ash and unsaturated weathered ashes. The unsaturated weathered ashes are relatively depleted in CaO, Fe2O3, TiO2, SiO2, Na2O and P2O5 due to dissolution and hydrolysis caused by chemical interaction with ingressing CO2 from the atmosphere and infiltrating rain water. Observed accumulations of Fe2O3, TiO2, CaO, K2O, Na2O and SO3 and Zn, Zr, Sr, Pb, Ni, Cr and Co in the lower layers indicate progressive downward movement through the ash dump though at a slow rate. The bulk mineralogy of unsaturated weathered dry disposed ash, as determined by XRD analysis, revealed quartz and mullite as the major crystalline phases; while anorthite, hematite, enstatite, lime, calcite, and mica were present as minor mineral phases. Pore water chemistry revealed a low concentration of readily soluble metals in unsaturated weathered ashes in comparison with fresh ash, which shows high leachability. This suggests that over time the precipitation of transient minor secondary mineral phases; such as calcite and mica might retard residual metal release from unsaturated weathered ash. Chloride and sulphate species of the water soluble extracts of weathered ash are at equilibrium with Na+ and K+; these demonstrate progressive leaching over time and become supersaturated at the base of unsaturated weathered ash. This suggests that the ash dump does not

Optimality and Conductivity for Water Flow: From Landscapes, to Unsaturated Soils, to Plant Leaves

Energy Technology Data Exchange (ETDEWEB)

Liu, H.H.

2012-02-23

Optimality principles have been widely used in many areas. Based on an optimality principle that any flow field will tend toward a minimum in the energy dissipation rate, this work shows that there exists a unified form of conductivity relationship for three different flow systems: landscapes, unsaturated soils and plant leaves. The conductivity, the ratio of water flux to energy gradient, is a power function of water flux although the power value is system dependent. This relationship indicates that to minimize energy dissipation rate for a whole system, water flow has a small resistance (or a large conductivity) at a location of large water flux. Empirical evidence supports validity of the relationship for landscape and unsaturated soils (under gravity dominated conditions). Numerical simulation results also show that the relationship can capture the key features of hydraulic structure for a plant leaf, although more studies are needed to further confirm its validity. Especially, it is of interest that according to this relationship, hydraulic conductivity for gravity-dominated unsaturated flow, unlike that defined in the classic theories, depends on not only capillary pressure (or saturation), but also the water flux. Use of the optimality principle allows for determining useful results that are applicable to a broad range of areas involving highly non-linear processes and may not be possible to obtain from classic theories describing water flow processes.

Evolution of strain localization in variable-width three-dimensional unsaturated laboratory-scale cut slopes

Science.gov (United States)

Morse, Michael S.; Lu, Ning; Wayllace, Alexandra; Godt, Jonathan W.

2017-01-01

To experimentally validate a recently developed theory for predicting the stability of cut slopes under unsaturated conditions, the authors measured increasing strain localization in unsaturated slope cuts prior to abrupt failure. Cut slope width and moisture content were controlled and varied in a laboratory, and a sliding door that extended the height of the free face of the slope was lowered until the cut slope failed. A particle image velocimetry tool was used to quantify soil displacement in the x-y">x-y (horizontal) and x-z">x-z (vertical) planes, and strain was calculated from the displacement. Areas of maximum strain localization prior to failure were shown to coincide with the location of the eventual failure plane. Experimental failure heights agreed with the recently developed stability theory for unsaturated cut slopes (within 14.3% relative error) for a range of saturation and cut slope widths. A theoretical threshold for sidewall influence on cut slope failures was also proposed to quantify the relationship between normalized sidewall width and critical height. The proposed relationship was consistent with the cut slope experiment results, and is intended for consideration in future geotechnical experiment design. The experimental data of evolution of strain localization presented herein provide a physical basis from which future numerical models of strain localization can be validated.

Evidence for magnesium isotope heterogeneity in the solar protoplanetary disk

DEFF Research Database (Denmark)

Larsen, Kirsten Kolbjørn; Trinquier, Anne Marie-Pierre Emilie; Paton, Chad

2011-01-01

With a half-life of 0.73 Myr, the 26Al-to-26Mg decay system is the most widely used short-lived chronometer for understanding the formation and earliest evolution of the solar protoplanetary disk. However, the validity of 26Al–26Mg ages of meteorites and their components relies on the critical......, and planets demonstrating the existence of widespread heterogeneity in the mass-independent 26Mg composition (µ26Mg*) of bulk solar system reservoirs with solar or near-solar Al/Mg ratios. This variability may represent heterogeneity in the initial abundance of 26Al across the solar protoplanetary disk...

Can Electrical Resistance Tomography be used for imaging unsaturated moisture flow in cement-based materials with discrete cracks?

International Nuclear Information System (INIS)

Smyl, Danny; Rashetnia, Reza; Seppänen, Aku; Pour-Ghaz, Mohammad

2017-01-01

Previously, it has been shown that Electrical Resistance Tomography (ERT) can be used for monitoring moisture flow in undamaged cement-based materials. In this work, we investigate whether ERT could be used for imaging three-dimensional (3D) unsaturated moisture flow in cement-based materials that contain discrete cracks. Novel computational methods based on the so-called absolute imaging framework are developed and used in ERT image reconstructions, aiming at a better tolerance of the reconstructed images with respect to the complexity of the conductivity distribution in cracked material. ERT is first tested using specimens with physically simulated cracks of known geometries, and corroborated with numerical simulations of unsaturated moisture flow. Next, specimens with loading-induced cracks are imaged; here, ERT reconstructions are evaluated qualitatively based on visual observations and known properties of unsaturated moisture flow. Results indicate that ERT is a viable method of visualizing 3D unsaturated moisture flow in cement-based materials with discrete cracks. - Highlights: • 3D EIT is developed to visualize water ingress in cracked mortar. • Mortar with different size discrete cracks are used. • The EIT results are corroborated with numerical simulations. • EIT results accurately show the temporal and spatial variation of water content. • EIT is shown to be a viable method to monitor flow in cracks and matrix.

Superheating in nucleate boiling calculated by the heterogeneous nucleation theory

International Nuclear Information System (INIS)

Gerum, E.; Straub, J.; Grigull, U.

1979-01-01

With the heterogeneous nucleation theory the superheating of the liquid boundary layer in nucleate boiling is described not only for the onset of nuclear boiling but also for the boiling crisis. The rate of superheat depends on the thermodynamic stability of the metastable liquid, which is influenced by the statistical fluctuations in the liquid and the nucleation at the solid surface. Because of the fact that the cavities acting as nuclei are too small for microscopic observation, the size and distribution function of the nuclei on the surface necessary for the determination of the probability of bubble formation cannot be detected by measuring techniques. The work of bubble formation reduced by the nuclei can be represented by a simple empirical function whose coefficients are determined from boiling experiments. Using this the heterogeneous nucleation theory describes the superheating of the liquid. Several fluids including refrigerants, liquid gases, organic liquids and water were used to check the theory. (author)

Saturated-unsaturated flow to a well with storage in a compressible unconfined aquifer

Science.gov (United States)

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2011-05-01

Mishra and Neuman (2010) developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or unsaturated zones. Their solution accounts for horizontal as well as vertical flows in each zone. It represents unsaturated zone constitutive properties in a manner that is at once mathematically tractable and sufficiently flexible to provide much improved fits to standard constitutive models. In this paper we extend the solution of [2010] to the case of a finite diameter pumping well with storage; investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the [1980]- [1976] model; use our solution to analyze 11 transducer-measured drawdown records from a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; validate our parameter estimates against manually-measured drawdown records in 14 other piezometers at Borden; and compare (a) our estimates of aquifer parameters with those obtained on the basis of all these records by [2008], (b) on the basis of 11 transducer-measured drawdown records by [2007], (c) our estimates of van Genuchten-Mualem parameters with those obtained on the basis of laboratory drainage data from the site by [1992], and (d) our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well. We also use our solution to analyze 11 transducer-measured drawdown

Organic aerosol formation in citronella candle plumes.

Science.gov (United States)

Bothe, Melanie; Donahue, Neil McPherson

2010-09-01

Citronella candles are widely used as insect repellants, especially outdoors in the evening. Because these essential oils are unsaturated, they have a unique potential to form secondary organic aerosol (SOA) via reaction with ozone, which is also commonly elevated on summer evenings when the candles are often in use. We investigated this process, along with primary aerosol emissions, by briefly placing a citronella tealight candle in a smog chamber and then adding ozone to the chamber. In repeated experiments, we observed rapid and substantial SOA formation after ozone addition; this process must therefore be considered when assessing the risks and benefits of using citronella candle to repel insects.

Kinetic study of the degradation of C5 and C6 unsaturated aldehydes and alcohols by ozone

Science.gov (United States)

Kalalian, Carmen; Roth, Estelle; Chakir, Abdelkhaleq

2017-04-01

Emissions of biogenic volatile organic compounds (VOCs) are higher than those from anthropogenic sources. They are therefore likely to have a great influence on atmospheric chemistry both locally and regionally, through their impact on the HOx balance (HOx = HO + HO2), ozone production and ability to form secondary organic aerosols (SOA). Among the volatile organic compounds of biogenic origin are the family of C5 and C6 unsaturated aldehydes and alcohols. Few information exist regarding the fate of these compounds in the atmosphere especially there reaction with ozone. In this work, we studied the kinetics of the reaction of three unsaturated aldehydes (trans-2-pentenal, trans-2-hexenal and 2-methyl-2-pentenal) and three unsaturated alcohols (1-penten-3-ol, cis-2-penten-1-ol and trans-3-hexen-1-ol) with ozone O3 in a rigid atmospheric simulation chamber coupled to an FTIR spectrometer at four different temperatures (273, 298, 333 and 353 K) and at atmospheric pressure. The rate constants of the ozonolysis reaction of the unsaturated aldehydes and the unsaturated alcohols studied were determined and the following Arrhenius expression was obtained (cm3 molecule -1 s -1): k (Trans -2-pentenal)= (3.83 ± 3.71) x 10-16 exp (- (1706 ± 295) / T) k (Trans-2-hexenal)= (1.43 ± 0.67) x 10-16 exp (- (1369 ± 141) / T) k(2-Methyl-2-pentenal)= (3.62± 0.22) x 10-18 exp (- (121 ± 20) / T) k(1-penten-3-ol) = (1.42 ± 1.24) x 10-16 exp (- (642 ± 250) / T) k(Cis-2-penten-1-ol)= (3.14 ± 0.45) x 10-15 exp (- (1045 ± 40) / T) k(Trans-3-hexen-1-ol)= (6.38 ± 1.75) x 10-16 exp (- (686 ± 89) / T) The obtained data will be discussed in terms of structure-reactivity relationship and compared with the reported reactivity with OH radicals. The atmospheric implications derived from this study are discussed as well.

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-01

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes.

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-21

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Unsaturated water flow and tracer transport modeling with Alliances

Energy Technology Data Exchange (ETDEWEB)

Constantin, Alina, E-mail: alina.constantin@nuclear.ro [Institute for Nuclear Research, Campului Str, No. 1, PO Box 78, Postal Code 115400 Mioveni, Arges County (Romania); Genty, Alain, E-mail: alain.genty@cea.fr [CEA Saclay, DM2S/SFME/LSE, Gif-sur-Yvette 91191 cedex (France); Diaconu, Daniela; Bucur, Crina [Institute for Nuclear Research, Campului Str, No. 1, PO Box 78, Postal Code 115400 Mioveni, Arges County (Romania)

2013-12-15

Highlights: • Simulation of water flow and solute transport at Saligny site, Romania was done. • Computation was based on the available experimental data with Alliances platform. • Very good results were obtained for the saturation profile in steady state. • Close fit to experimental data for saturation profile at 3 m in transient state. • Large dispersivity coefficients were fitted to match tracer experiment. - Abstract: Understanding water flow and solute transport in porous media is of central importance in predicting the radionuclide fate in the geological environment, a topic of interest for the performance and safety assessment studies for nuclear waste disposal. However, it is not easy to predict transport properties in real systems because they are geologically heterogeneous from the pore scale upwards. This paper addresses the simulation of water flow and solute transport in the unsaturated zone of the Saligny site, the potential location for the Romanian low and intermediate level waste (LILW) disposal. Computation was based on the current available experimental data for this zone and was performed within Alliances, a software platform initially jointly developed by French organizations CEA, ANDRA and EDF. The output of the model developed was compared with the measured values in terms of saturation profile of the soil for water movement, in both steady and transient state. Very good results were obtained for the saturation profile in steady state and a close fit of the simulation over experimental data for the water saturation profile at a depth of 3 m in transient state. In order to obtain information regarding the solute migration in depth and the solute lateral dispersion, a tracer test was launched on site and dispersivity coefficients of the solute were fitted in order to match the experimental concentration determined on samples from different locations of the site. Results much close to the experiment were obtained for a longitudinal

Investigation of isotopic signals in the unsaturated zone with the use of direct push technology and azaeotropic distillation

Directory of Open Access Journals (Sweden)

Andreas Kallioras

2012-09-01

Full Text Available This paper contributes to the investigation of the unsaturated zone, through the application of combined field and lab techniques. The results show that direct push methods, which are considered ideal for multilevel sampling of undisturbed soil in the unsaturated zone, proved to be effective also for the consequent extraction of the pore water for further isotopic determination. This ultimate goal can be achieved thank to the application of azaetropic distillation, which has the least isotopic fractionation effects on groundwater samples.

Kinetics study of heterogeneous reactions of ozone with erucic acid using an ATR-IR flow reactor.

Science.gov (United States)

Leng, Chunbo; Hiltner, Joseph; Pham, Hai; Kelley, Judas; Mach, Mindy; Zhang, Yunhong; Liu, Yong

2014-03-07

The ozone initiated heterogeneous oxidation of erucic acid (EA) thin film was investigated using a flow system combined with attenuated total reflection infrared spectroscopy (ATR-IR) over wide ranges of ozone concentrations (0.25-60 ppm), thin film thickness (0.1-1.0 μm), temperatures (263-298 K), and relative humidities (0-80% RH) for the first time. Pseudo-first-order rate constants, kapp, and overall reactive uptake coefficients, γ, were obtained through changes in the absorbance of C[double bond, length as m-dash]O stretching bands at 1695 cm(-1), which is assigned to the carbonyl group in carboxylic acid. Results showed that the reaction followed the Langmuir-Hinshelwood mechanism and kapp was largely dominated by surface reaction over bulk phase reaction. In addition, both the kapp and the γ values showed very strong temperature dependences (∼two orders of magnitude) over the temperature range; in contrast, they only slightly increased with increasing RH values from 0-80%. According to the kapp values as a function of temperature, the activation energy for the heterogeneous reaction was estimated to be 80.6 kJ mol(-1). Our results have suggested that heterogeneous reactions between ozone and unsaturated solid surfaces likely have a substantially greater temperature dependence than liquid ones. Moreover, the hygroscopic properties of EA thin films before and after exposure to ozone were also studied by measurement of water uptake. Based on the hygroscopicity data, the insignificant RH effect on reaction kinetics was probably due to the relatively weak water uptake by the unreacted and reacted EA thin films.

The study of the migration of the radionuclide Am-241 in unsaturated soil from in Saligny area

International Nuclear Information System (INIS)

Toma, Alexandru Dan

2005-01-01

The functioning of the Cernavoda Nuclear Power Plant will generate low and medium radioactive waste contaminated with long-lived fission products (from U, Pu, Np, Am fission or decay), radioactive carbon (C-14) and tritium (H-3), which by their radiochemical characteristics and their influence upon the environment and people, request special attention regarding their storage and disposal. Based on the geological and mineralogical researches regarding the location of a repository for low and medium active waste, Saligny area near the Cernavoda Nuclear Power Plant was chosen. The repository will be located in loess, seated on sedimentary formations with insertions of clay patches. The main target of the research is to obtain some experimental data necessary for the evaluation of the migration of the radionuclide Am-241 (resulted from Cernavoda Nuclear Power Plant) in unsaturated soils in Saligny area, which will be the host of the Final Repository for Low and Medium Active Waste. The analysis of the test data obtained in the laboratory for the determination of the migration parameters of the radionuclide Am-241 in the material of the geological formation of Saligny area showed that there is a direct correlation between the values of these parameters and the basic mineralogical component - clay - of the soil sample. (author)

Influence of chemical heterogeneity of solid solutions on brittleness in chromium steels

International Nuclear Information System (INIS)

Madyanov, S.A.; Sedov, V.K.; Apaev, B.A.

1985-01-01

The role of chemical heterogeneity of solid solutions in formation of mechanical properties of Kh09, Kh15, Kh20, Kh19N2G5T chromium steels has been investigated. It is established that besides the known regioA of chemical heterogeneity in the vicinity of 475 deg C exists a high-temperature region (1000-1050 deg C), where maximum heteroge=- neity of chromium distribution in solid solution, is observed. Both types of chemical heterogeneity cause essential hardening of alloys, which becomes apparent in abrupt change of capability to microplastic deformation The mechanism of occurrence of the given temper brittleness consists in carbon diffusion into microvolunes enriched in carbide-forming elements

Unsaturated fatty acids lactose esters: cytotoxicity, permeability enhancement and antimicrobial activity

OpenAIRE

Lucarini, Simone; Fagioli, Laura; Campana, Raffaella; Cole, Hannah; Duranti, Andrea; Baffone, Wally; Vllasaliu, Driton; Casettari, Luca

2016-01-01

Sugar based surfactants conjugated with fatty acid chains are an emerging broad group of highly biocompatible and biodegradable compounds with established and potential future applications in the pharmaceutical, cosmetic and food industries. In this work, we investigated absorption enhancing and antimicrobial properties of disaccharide lactose, mono-esterified with unsaturated fatty acids through an enzymatic synthetic approach. After chemical and cytotoxicity characterizations, their permeab...

Solution of AntiSeepage for Mengxi River Based on Numerical Simulation of Unsaturated Seepage

Science.gov (United States)

Ji, Youjun; Zhang, Linzhi; Yue, Jiannan

2014-01-01

Lessening the leakage of surface water can reduce the waste of water resources and ground water pollution. To solve the problem that Mengxi River could not store water enduringly, geology investigation, theoretical analysis, experiment research, and numerical simulation analysis were carried out. Firstly, the seepage mathematical model was established based on unsaturated seepage theory; secondly, the experimental equipment for testing hydraulic conductivity of unsaturated soil was developed to obtain the curve of two-phase flow. The numerical simulation of leakage in natural conditions proves the previous inference and leakage mechanism of river. At last, the seepage control capacities of different impervious materials were compared by numerical simulations. According to the engineering actuality, the impervious material was selected. The impervious measure in this paper has been proved to be effectible by hydrogeological research today. PMID:24707199

Plant adaptation to frequent alterations between high and low temperatures: remodeling of membrane lipids and maintenance of unsaturation levels

OpenAIRE

Zheng, Guowei; Tian, Bo; Zhang, Fujuan; Tao, Faqing; Li, Weiqi

2011-01-01

One major strategy by which plants adapt to temperature change is to decrease the degree of unsaturation of membrane lipids under high temperature and increase it under low temperature. We hypothesize that this strategy cannot be adopted by plants in ecosystems and environments with frequent alterations between high and low temperatures, because changes in lipid unsaturation are complex and require large energy inputs. To test this hypothesis, we used a lipidomics approach to profile changes ...

Effects of Unsaturated Fat Dietary Supplements on Blood Lipids, and on Markers of Malnutrition and Inflammation in Hemodialysis Patients

DEFF Research Database (Denmark)

Ewers, Bettina; Riserus, Ulf; Marckmann, Peter

2009-01-01

OBJECTIVE: We examined the effects of commercially available unsaturated fat dietary supplements on blood lipids, and on markers of malnutrition and inflammation, in an adult population of hemodialysis (HD) patients. DESIGN: This was a restricted, randomized (equal blocks), investigator-blinded 2x6...... as assessed according to C-reactive protein serum concentrations. Adding unsaturated fat to the diet seems to be a safe and effective way to prevent and treat malnutrition in hemodialysis patients....

Hydrogeology of the unsaturated zone, North Ramp area of the Exploratory Studies Facility, Yucca Mountain, Nevada

Energy Technology Data Exchange (ETDEWEB)

Rousseau, J.P.; Kwicklis, E.M.; Gillies, D.C. [eds.

1999-03-01

Yucca Mountain, in southern Nevada, is being investigated by the US Department of Energy as a potential site for a repository for high-level radioactive waste. This report documents the results of surface-based geologic, pneumatic, hydrologic, and geochemical studies conducted during 1992 to 1996 by the US Geological Survey in the vicinity of the North Ramp of the Exploratory Studies Facility (ESF) that are pertinent to understanding multiphase fluid flow within the deep unsaturated zone. Detailed stratigraphic and structural characteristics of the study area provided the hydrogeologic framework for these investigations. Shallow infiltration is not discussed in detail in this report because the focus in on three major aspects of the deep unsaturated-zone system: geologic framework, the gaseous-phase system, and the aqueous-phase system. However, because the relation between shallow infiltration and deep percolation is important to an overall understanding of the unsaturated-zone flow system, a summary of infiltration studies conducted to date at Yucca Mountain is provided in the section titled Shallow Infiltration. This report describes results of several Site Characterization Plan studies that were ongoing at the time excavation of the ESF North Ramp began and that continued as excavation proceeded.

Highly Functionalised Cyclopentanes by Radical Cyclisation of Unsaturated Bromolactones III. Preparation of Carbaaldohexofuranoses. - Determination of the Relative Configuration at C-4/C-5 of 2,3-Unsaturated heptono-1,4-lactones by Means of 1-H NMR Spectroscopy

DEFF Research Database (Denmark)

Lundt, Inge; Horneman, Anne Marie

1999-01-01

Two new carbaaldohexofuranoses, carba--D-glucofuranose and carba--L-mannofuranose have been prepared using 5,6-O-isopropylidene-D-glycero-L-galacto-heptono-1,4-lactone (6) as the starting material. The key step was a highly stereoselective intramolecular 5-exo-trig radical cyclisation of C-2......-substituted 2,3-unsaturated 7-bromo-7-deoxy-heptono-1,4-lactones promoted by tributyltin hydride. Assignment of the configuration of the unsaturated lactones was based upon NMR data of related compounds. The starting material, compound 6, was obtained by chain elongation of D-gulose, and a facile method...

Anomalous Fe and Mn heterogeneity observed in microscopic inclusions in diamond using nuclear microscopy

International Nuclear Information System (INIS)

Sideras-Haddad, E.; Hart, R.J.; Connell, S.H.; Sellschop, J.P.F.; Tredoux, M.

1999-01-01

A Fe and Mn heterogeneity effect was observed in microscopic garnet inclusion in diamond using micro-PIXE. Results are presented and the implications of these disequilibrium element distributions during growth of garnets are discussed. The occurrence of zoning or any type of chemical inhomogeneity within inclusions encapsulated within diamond has implications on the age of formation of the inclusion and the diamond. It is believed that the age of the inclusion is that of the diamond formation itself, with subsequent isolation of the inclusion from the mantle by the diamond. The significance of the chemical heterogeneity or zoning is that it should not exist given the high temperature and long time of encapsulation

HeNCE: A Heterogeneous Network Computing Environment

Directory of Open Access Journals (Sweden)

Adam Beguelin

1994-01-01

Full Text Available Network computing seeks to utilize the aggregate resources of many networked computers to solve a single problem. In so doing it is often possible to obtain supercomputer performance from an inexpensive local area network. The drawback is that network computing is complicated and error prone when done by hand, especially if the computers have different operating systems and data formats and are thus heterogeneous. The heterogeneous network computing environment (HeNCE is an integrated graphical environment for creating and running parallel programs over a heterogeneous collection of computers. It is built on a lower level package called parallel virtual machine (PVM. The HeNCE philosophy of parallel programming is to have the programmer graphically specify the parallelism of a computation and to automate, as much as possible, the tasks of writing, compiling, executing, debugging, and tracing the network computation. Key to HeNCE is a graphical language based on directed graphs that describe the parallelism and data dependencies of an application. Nodes in the graphs represent conventional Fortran or C subroutines and the arcs represent data and control flow. This article describes the present state of HeNCE, its capabilities, limitations, and areas of future research.

FORMATION OF CALCITE AND SILICA FROM PERCOLATION IN A HYDROLOGICALLY UNSATURATED SETTING, YUCCA MOUNTAIN, NEVADA

International Nuclear Information System (INIS)

Paces, J.B.; Whelan, J.F.; Peterman, Z.E.; Marshall, B.D.

2000-01-01

Geological, mineralogical, chemical, and isotopic evidence from coatings of calcite and silica on open fractures and lithophysal cavities within welded tuffs at Yucca Mountain indicate an origin from meteoric water percolating through a thick (500 to 700 m) unsaturated zone (UZ) rather than from pulses of ascending ground water. Geologic evidence for a UZ setting includes the presence of coatings in only a small percentage of cavities, the restriction of coatings to fracture footwalls and cavity floors, and an absence of mineral high-water marks indicative of water ponding. Systematic mineral sequences (early calcite, followed by chalcedony with minor quartz and fluorite, and finally calcite with intercalated opal forming the bulk of the coatings) indicate progressive changes in UZ conditions through time, rather than repeated saturation by flooding. Percolation under the influence of gravity also results in mineral textures that vary between steeply dipping sites (thinner coatings of blocky calcite) and shallowly dipping sites (thicker coatings of coarse, commonly bladed calcite, with globules and sheets of opal). Micrometer-scale growth banding in both calcite and opal reflects slow average growth rates (scale of mm/m.y.) over millions of years rather than only a few rapidly deposited growth episodes. Isotopic compositions of C, O, Sr, and U from calcite and opal indicate a percolation-modified meteoric water source, and collectively refute a deeper ground-water source. Chemical and isotopic variations in coatings also indicate long-term evolution of water compositions. Although some compositional changes are related to shifts in climate, growth rates in the deeper UZ are buffered from large changes in meteoric input. Coatings most likely formed from films of water flowing down connected fracture pathways. Mineral precipitation is consistent with water vapor and carbon dioxide loss from films at very slow rates. Data collectively indicate that mineral coatings

Semantic Interoperability in Heterogeneous IoT Infrastructure for Healthcare

Directory of Open Access Journals (Sweden)

Sohail Jabbar

2017-01-01

Full Text Available Interoperability remains a significant burden to the developers of Internet of Things’ Systems. This is due to the fact that the IoT devices are highly heterogeneous in terms of underlying communication protocols, data formats, and technologies. Secondly due to lack of worldwide acceptable standards, interoperability tools remain limited. In this paper, we proposed an IoT based Semantic Interoperability Model (IoT-SIM to provide Semantic Interoperability among heterogeneous IoT devices in healthcare domain. Physicians communicate their patients with heterogeneous IoT devices to monitor their current health status. Information between physician and patient is semantically annotated and communicated in a meaningful way. A lightweight model for semantic annotation of data using heterogeneous devices in IoT is proposed to provide annotations for data. Resource Description Framework (RDF is a semantic web framework that is used to relate things using triples to make it semantically meaningful. RDF annotated patients’ data has made it semantically interoperable. SPARQL query is used to extract records from RDF graph. For simulation of system, we used Tableau, Gruff-6.2.0, and Mysql tools.

Possible preparation of wood-plastic composites based on unsaturated polyester resins and styrene by radiation and chemical methods in combination

International Nuclear Information System (INIS)

Pesek, M.; Pultar, F.; Jarkovsky, J.; Andr, J.

1983-01-01

Using the radiation chemical method it is possible to prepare wood-plastic composites using doses of 1 to 2.5 kGy. The impregnation mixture in the wood gelatinates and subsequent curing using chemical initiators takes place without outflow of the mixture from the wood and without formation of incrustations. The basic components of the impregnation mixtures used were unsaturated polyester resins; styrene or methyl methacrylate was used as the thinner. The proven initiator of polymerization was 2,2'-azobisisobutyronitrile. The technology is described of wood impregnation and radiation or chemical curing. The effects were monitored of viscosity, temperature, radiation dose and the concentrations of the individual components of the impregnation mixtures and initiators of polymerization on the process of the preparation of wood-plastic composites. (M.D.)

Research program to develop and validate conceptual models for flow and transport through unsaturated, fractured rock

International Nuclear Information System (INIS)

Glass, R.J.; Tidwell, V.C.

1991-01-01

As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicated on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction. 43 refs

Research program to develop and validate conceptual models for flow and transport through unsaturated, fractured rock

International Nuclear Information System (INIS)

Glass, R.J.; Tidwell, V.C.

1991-09-01

As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicted on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction

Research program to develop and validate conceptual models for flow and transport through unsaturated, fractured rock

International Nuclear Information System (INIS)

Glass, R.J.; Tidwell, V.C.

1991-01-01

As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicted on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction

Nitrogen fluxes through unsaturated zones in five agricultural settings across the United States

Science.gov (United States)

Green, C.T.; Fisher, L.H.; Bekins, B.A.

2008-01-01

The main physical and chemical controls on nitrogen (N) fluxes between the root zone and the water table were determined for agricultural sites in California, Indiana, Maryland, Nebraska, and Washington from 2004 to 2005. Sites included irrigated and nonirrigated fields; soil textures ranging from clay to sand; crops including corn, soybeans, almonds, and pasture; and unsaturated zone thicknesses ranging from 1 to 22 m. Chemical analyses of water from lysimeters and shallow wells indicate that advective transport of nitrate is the dominant process affecting the flux of N below the root zone. Vertical profiles of (i) nitrogen species, (ii) stable isotopes of nitrogen and oxygen, and (iii) oxygen, N, and argon in unsaturated zone air and correlations between N and other agricultural chemicals indicate that reactions do not greatly affect N concentrations between the root zone and the capillary fringe. As a result, physical factors, such as N application rate, water inputs, and evapotranspiration, control the differences in concentrations among the sites. Concentrations of N in shallow lysimeters exhibit seasonal variation, whereas concentrations in lysimeters deeper than a few meters are relatively stable. Based on concentration and recharge estimates, fluxes of N through the deep unsaturated zone range from 7 to 99 kg ha-1 yr-1. Vertical fluxes of N in ground water are lower due to spatial and historical changes in N inputs. High N fluxes are associated with coarse sediments and high N application rates. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Phenomenological studies of two-phase flow processes for nuclear waste isolation

International Nuclear Information System (INIS)

Pruess, K.; Finsterle, S.; Persoff, P.; Oldenburg, C.

1994-01-01

The US civilian radioactive waste management program is unique in its focus on a site in the unsaturated zone, at Yucca Mountain, Nevada. Two-phase flow phenomena can also play an important role in repositories beneath the water table where gas is generated by corrosion, hydrolysis, and biological degradation of the waste packages. An integrated program has been initiated to enhance our understanding of two-phase flow behavior in fractured rock masses. The studies include two-phase (gas-liquid) flow experiments in laboratory specimens of natural rock fractures, analysis and modeling of heterogeneity and instability effects in two-phase flow, and design and interpretation of field experiments by means of numerical simulation. We present results that identify important aspects of two-phase flow behavior on different space and time scales which are relevant to nuclear waste disposal in both unsaturated and saturated formations

Nitrate transport and transformation processes in unsaturated porous media

Science.gov (United States)

Tindall, James A.; Petrusak, Robin L.; McMahon, Peter B.

1995-01-01

A series of experiments was conducted on two contrasting agricultural soils to observe the influence of soil texture, preferential flow, and plants on nitrate transport and denitrification under unsaturated conditions. Calcium nitrate fertilizer was applied to the surface of four large undisturbed soil cores (30 cm diameter by 40 cm height). Two of the cores were a structured clay obtained from central Missouri and two were an unstructured fine sand obtained from central Florida. The cores were irrigated daily and maintained at a matric potential of -20 kPa, representative of soil tension in the rooting zone of irrigated agricultural fields. Volumetric water content (θ), concentration of nitrate-N in the soil solution, and nitrous oxide flux at the surface, 10, 20, and 30 cm were monitored daily. Leaching loss of surface-applied N03− -N was significant in both the sand and the clay. In unplanted sand cores, almost all of the applied nitrate was leached below 30 cm within 10 days. Gaseous N loss owing to denitrification was no greater than 2% of the nitrate-N applied to the unplanted sand cores and, in general, was less than 1 %. Although leaching was somewhat retarded in the clay cores, about 60% of the applied nitrate-N was leached from the unplanted clay soil in 5–6 weeks. Under unsaturated conditions, the clay had little to no tendency to denitrify despite the greater moisture content of the clay and retarded leaching of nitrate in the clay. The planted sand cores had surprisingly large gaseous N loss owing to denitrification, as much as 17% of the nitrate-N. Results from both the clay and sand experiments show that the dynamics of nitrate transport and transformation in unsaturated soils are affected by small, localized variations in the soil moisture content profile, the gaseous diffusion coefficient of the soil, the rate at which the nitrate pulse passes through the soil, the solubility of N2O and N2 and the diffusion of the gasses through the soil

Improved success of sparse matrix protein crystallization screening with heterogeneous nucleating agents.

Directory of Open Access Journals (Sweden)

Anil S Thakur

2007-10-01

Full Text Available Crystallization is a major bottleneck in the process of macromolecular structure determination by X-ray crystallography. Successful crystallization requires the formation of nuclei and their subsequent growth to crystals of suitable size. Crystal growth generally occurs spontaneously in a supersaturated solution as a result of homogenous nucleation. However, in a typical sparse matrix screening experiment, precipitant and protein concentration are not sampled extensively, and supersaturation conditions suitable for nucleation are often missed.We tested the effect of nine potential heterogenous nucleating agents on crystallization of ten test proteins in a sparse matrix screen. Several nucleating agents induced crystal formation under conditions where no crystallization occurred in the absence of the nucleating agent. Four nucleating agents: dried seaweed; horse hair; cellulose and hydroxyapatite, had a considerable overall positive effect on crystallization success. This effect was further enhanced when these nucleating agents were used in combination with each other.Our results suggest that the addition of heterogeneous nucleating agents increases the chances of crystal formation when using sparse matrix screens.

Field determination of vertical permeability to air in the unsaturated zone

Science.gov (United States)

Weeks, Edwin P.

1978-01-01

The vertical permeability to air of layered materials in the unsaturated zone may be determined from air pressure data obtained at depth during a period when air pressure is changing at land surface. Such data may be obtained by monitoring barometric pressure with a microbarograph or surveying altimeter and simultaneously measuring down-hole pneumatic head differences in specially constructed piezometers. These data, coupled with air-filled porosity data from other sources, may be compared with the results of electric-analog or numerical solution of the one-dimensional diffusion equation to make a trial-and-error determination of the air permeability for each layer. The permeabilities to air may in turn be converted to equivalent hydraulic conductivity values if the materials are well drained, are permeable enough that the Klinkenberg effect is small, and are structurally unaffected by wetting. The method offers potential advantages over present methods to evaluate sites for artificial recharge by spreading; to evaluate ground-water pollution hazards from feedlots, sanitary landfills , and land irrigated with sewage effluent; and to evaluate sites for temporary storage of gas in the unsaturated zone. (Woodard-USGS)

Colloid suspension stability and transport through unsaturated porous media

International Nuclear Information System (INIS)

McGraw, M.A.; Kaplan, D.I.

1997-04-01

Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media

Impacts of heterogeneous reactions to atmospheric peroxides: Observations and budget analysis study

Science.gov (United States)

Qin, Mengru; Chen, Zhongming; Shen, Hengqing; Li, Huan; Wu, Huihui; Wang, Yin

2018-06-01

Atmospheric peroxides play important roles in atmospheric chemistry, acting as reactive oxidants and reservoirs of HOX and ROX radicals. Field measurements of atmospheric peroxides were conducted over urban Beijing from 2015 to 2016, including dust storm days, haze days and different seasons. We employed a box model based on RACM2 mechanism to conduct concentration simulation and budget analysis of hydrogen peroxide (H2O2) and peroxyacetic acid (PAA). In this study, heterogeneous reaction is found to be a significant sink for atmospheric H2O2 and PAA in urban Beijing. Here, we recommend a suitable uptake coefficient formula considering the water effect for model research of peroxides. It is found that H2O2 and PAA unexpectedly maintained considerable concentrations on haze days, even higher than that on non-haze days. This phenomenon is mainly ascribed to relatively high levels of volatile organic compounds and ozone on haze days. In addition, high levels of water vapor in pollution episode can promote not only the heterogeneous uptake to aerosol phase but also the production of H2O2. Atmospheric PAA formation is suggested to be sensitive to alkenes and NOX in urban Beijing. In particular, with the help of peroxides, sulfate formation rate from heterogeneous uptake could increase by ∼4 times on haze days, indicating the potential effect of peroxides on enhancement of aerosol oxidative property and secondary sulfate formation.

Collective Identity Formation in Hybrid Organizations

DEFF Research Database (Denmark)

Boulongne, Romain; Boxenbaum, Eva

The present article examines the process of collective identity formation in the context of hybrid organizing. Empirically, we investigate hybrid organizing in a collaborative structure at the interface of two heterogeneous organizations in the domain of new renewable energies. We draw...... on the literature on knowledge sharing across organizational boundaries, particularly the notions of transfer, translation and transformation, to examine in real time how knowledge sharing in a hybrid setting contributes (or not) to the emergence of a new collective identity at the interface of two heterogeneous...... organizations. Our findings point to two factors that limit knowledge sharing and hence to new collective identity formation in a hybrid space: 1) ambiguous or multiple organizational roles and 2) strong identities of the collaborating organizations. These findings contribute to illuminating the initial...

Reactions of carbonyl compounds with α,β-unsaturated nitriles as a convenient pathway to carbo- and heterocycles

International Nuclear Information System (INIS)

Sharanin, Yu A; Goncharenko, M P; Litvinov, Victor P

1998-01-01

Published data on the methods for synthesis of carbo- and heterocyclic compounds based on reactions of α,β-unsaturated nitriles with carbonyl compounds and activated phenols are surveyed. It is demonstrated that all these reactions occur via nucleophilic addition of the carbanion generated from a carbonyl compound to the double bond of an unsaturated nitrile (the Michael reaction). The main routes of transformation of the adducts into carbo- and heterocyclic compounds are considered. The methods for regioselective preparation of fused 4H-pyrans or 1,4-dihydropyridines by varying conditions of cyclisation of Michael adducts are discussed. The bibliography includes 249 references.

A Modeling Study of Flow Diversion and Focusing in unsaturated Fractured Rocks

International Nuclear Information System (INIS)

Pan, Lehua; Wu, Yu-Shu; Zhang, Keni

2002-01-01

This study presents a systematic approach to analyze the flow diversion and flow focusing caused by the natural flow-barrier system in the unsaturated zone (UZ) of Yucca Mountain, Nevada, under ambient steady-state flow conditions. An existing analytical solution for analyzing capillary barrier in porous media has been extended to apply to the fractured porous rock. The new analytical solutions are used to identify the critical layers and to provide the guidance for generation of a proper three-dimensional (3-D), site-scale numerical grid. A large-scale 3-D numerical model (with more than a million grid blocks) has been developed with site-specific data to analyze the major flow patterns in the mountain. Our analyses show that large-scale lateral flow could take place in the UZ under ambient conditions, as a result of capillary barriers formed at the contacts of heterogeneous rock layers. This lateral flow runs generally toward the east (in the southern part) or southeast (in the northern part), which is consistent with the dip of the layer contacts. About 90 percent of the total lateral flow is found to be conducted by only a few critical rock layers. Faults that penetrate these rock layers act as vertical capillary barriers that stop the lateral flow. The combined effect of horizontal and vertical capillary barriers resulted in reduced percolation flow through repository horizon in general but focused downward flow along those penetrating faults. The model results were found to be consistent with the field water saturation. The findings of this study are consistent with a previously published two-dimensional (2-D) analysis and recent published modeling results using field-observed Cl-data

Estimating unsaturated hydraulic conductivity from soil moisture-tim function

International Nuclear Information System (INIS)

El Gendy, R.W.

2002-01-01

The unsaturated hydraulic conductivity for soil can be estimated from o(t) function, and the dimensionless soil water content parameter (Se)Se (β - βr)/ (φ - θ)), where θ, is the soil water content at any time (from soil moisture depletion curve l; θ is the residual water content and θ, is the total soil porosity (equals saturation point). Se can be represented as a time function (Se = a t b ), where t, is the measurement time and (a and b) are the regression constants. The recommended equation in this method is given by

Network formation under heterogeneous costs: The multiple group model

NARCIS (Netherlands)

Kamphorst, J.J.A.; van der Laan, G.

2007-01-01

It is widely recognized that the shape of networks influences both individual and aggregate behavior. This raises the question which types of networks are likely to arise. In this paper we investigate a model of network formation, where players are divided into groups and the costs of a link between

Products and mechanism of the reaction of Cl atoms with unsaturated alcohols

Science.gov (United States)

Rodríguez, Ana; Rodríguez, Diana; Soto, Amparo; Bravo, Iván; Diaz-de-Mera, Yolanda; Notario, Alberto; Aranda, Alfonso

2012-04-01

The products of the chlorine atom initiated oxidation of different unsaturated alcohols were determined at atmospheric pressure and ambient temperature, in a 400 L teflon reaction chamber using GC-FID and GC-MS for the analysis. The major products detected (with molar yields in brackets) are: chloroacetaldehyde (50 ± 8%) and acrolein (27 ± 2%) from allyl alcohol; acetaldehyde (77 ± 11%), chloroacetaldehyde (75 ± 18%), and methyl vinyl ketone (17 ± 2%) from 3-buten-2-ol; acetone (55 ± 4%) and chloroacetaldehyde (59 ± 8%) from 2-methyl-3-buten-2-ol; chloroacetone (18 ± 1%) and methacrolein (8 ± 1%) from 2-methyl-2-propen-1-ol; acetaldehyde (20 ± 1%), crotonaldehyde (6 ± 3%), 3-choloro-4-hydroxy-2-butanone (2 ± 2%) and 2-chloro-propanal (4 ± 5%) from crotyl alcohol; and acetone (24 ± 3%) from 3-methyl-2-buten-1-ol. The experimental data suggests that addition of Cl to the double bond of the unsaturated alcohol is the dominant reaction pathway compared to the H-abstraction channel.

Application of TOUGH to hydrologic problems related to the unsaturated zone site investigation at Yucca Mountain, Nevada

Energy Technology Data Exchange (ETDEWEB)

Kwicklis, E.M.; Healy, R.W. [Geological Survey, Lakewood, CO (United States); Bodvarsson, G.S. [Lawrence Berkeley Laboratory, CA (United States)] [and others

1995-03-01

To date, TOUGH and TOUGH2 have been the principal codes used by the U.S. Geological Survey in their investigation of the hydrology of the unsaturated zone at Yucca Mountain. Examples of some applications of the TOUGH and TOUGH2 codes to flow and transport problems related to the Yucca Mountain site investigation are presented, and the slight modifications made to the codes to implement them are discussed. These examples include: (1) The use of TOUGH in a simple fracture network model, with a discussion of an approach to calculate directional relative permeabilities at computational cells located at fracture intersections. These simulations illustrated that, under unsaturated conditions, the locations of dominant pathways for flow through fracture networks are sensitive to imposed boundary conditions; (2) The application of TOUGH to investigate the possible hydrothermal effects of waste-generated heat at Yucca Mountain using a dual-porosity, dual-permeability treatment to better characterize fracture-matrix interactions. Associated modifications to TOUGH for this application included implementation of a lookup table that can express relative permeabilities parallel and transverse to the fracture plane independently. These simulations support the continued use of an effective media approach in analyses of the hydrologic effects of waste-generated heat; and (3) An investigation of flow and tracer movement beneath a wash at Yucca Mountain in which a particle tracker was used as a post-processor. As part of this study, TOUGH2 was modified to calculate and output the x-,y- and z- sequence of tuffs overlying the potential repository site will result in the formation of capillary barriers that locally promote considerable lateral flow, thereby significantly decreasing the magnitude of fluxes form peak values at the ground surface and delaying the arrival of surface-derived moisture at the potential repository horizon.

Acetic Acid Formation by Selective Aerobic Oxidation of Aqueous Ethanol over Heterogeneous Ruthenium Catalysts

DEFF Research Database (Denmark)

Gorbanev, Yury; Kegnæs, Søren; Hanning, Christopher William

2012-01-01

Heterogeneous catalyst systems comprising ruthenium hydroxide supported on different carrier materials, titania, alumina, ceria, and spinel (MgAl2O4), were applied in selective aerobic oxidation ethanol to form acetic acid, an important bulk chemical and food ingredient. The catalysts were...

The role of unsaturations in the Gamma irradiation of crosslinkable polymers

International Nuclear Information System (INIS)

Satti, Angel J.; Ciolino, Andrés E.; Andreucetti, Noemí A.; Vallés, Enrique M.

2015-01-01

Nowadays, the understanding of the interaction of ionizing radiations with polymeric materials is becoming increasingly important. It is well known that many parameters regarding the synthesis of the polymers noticeably affect the irradiation process. In this work, an analysis of the effect of the type and the position of unsaturations in the molecular structure of crosslinkable polymers is performed. For such purpose, two solid semycristalline metallocenic ethylene 1-olefin copolymers (mEOC) which contain a low concentration of unsaturations from the synthesis, and their hydrogenated samples, were irradiated along with liquid poly(dimethylsiloxane) (PDMS) homo and copolymers containing different location and concentration of vinyl groups, which were structurally tailored through anionic synthesis. The source of irradiation was 60 Co, under vacuum at room temperature, in all the cases. The results indicated that terminal vinyls drastically accelerate the crosslinking to lower doses, even at much lower concentrations than other type and location of unsaturations for both, mEOC and PDMS, type of polymers. - Graphical abstract: Irradiated PEX # (ethylene copolymers with an # amount of 1-hexene -H- or 1-octadecene -OD) and their non-vinyl containing hidrogenated samples (PEX #h), along with irradiated vinyl functionalized siloxane polymers. Numbers within parentheses correspond to the number of vinyl groups per polymer chain for each irradiated polymer. Note that PDVi have been crosslinked with the lower dose of irradiation, although it has only one vinyl group. However, that is a terminal vinyl, while for the other polydimethylsiloxane derivatives, vinyls are within the main chain. - Highlights: • Terminal vinyls from metallocenic synthesis accelerate radioinduced crosslinking. • Trans vinyl structures are generated during irradiation, but vinyldenes are reluctant to react. • The position of the vinyl groups noticeably affects the irradiation process. �

Solution of AntiSeepage for Mengxi River Based on Numerical Simulation of Unsaturated Seepage

Directory of Open Access Journals (Sweden)

Youjun Ji

2014-01-01

Full Text Available Lessening the leakage of surface water can reduce the waste of water resources and ground water pollution. To solve the problem that Mengxi River could not store water enduringly, geology investigation, theoretical analysis, experiment research, and numerical simulation analysis were carried out. Firstly, the seepage mathematical model was established based on unsaturated seepage theory; secondly, the experimental equipment for testing hydraulic conductivity of unsaturated soil was developed to obtain the curve of two-phase flow. The numerical simulation of leakage in natural conditions proves the previous inference and leakage mechanism of river. At last, the seepage control capacities of different impervious materials were compared by numerical simulations. According to the engineering actuality, the impervious material was selected. The impervious measure in this paper has been proved to be effectible by hydrogeological research today.