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Sample records for modeling trihalomethane formation

  1. Investigating the role of biofilms in trihalomethane formation in water distribution systems with a multicomponent model.

    Science.gov (United States)

    Abokifa, Ahmed A; Yang, Y Jeffrey; Lo, Cynthia S; Biswas, Pratim

    2016-11-01

    Biofilms are ubiquitous in the pipes of drinking water distribution systems (DWDSs), and recent experimental studies revealed that the chlorination of the microbial carbon associated with the biofilm contributes to the total disinfection by-products (DBPs) formation with distinct mechanisms from those formed from precursors derived from natural organic matter (NOM). A multiple species reactive-transport model was developed to explain the role of biofilms in DBPs formation by accounting for the simultaneous transport and interactions of disinfectants, organic compounds, and biomass. Using parameter values from experimental studies in the literature, the model equations were solved to predict chlorine decay and microbial regrowth dynamics in an actual DWDS, and trihalomethanes (THMs) formation in a pilot-scale distribution system simulator. The model's capability of reproducing the measured concentrations of free chlorine, suspended biomass, and THMs under different hydrodynamic and temperature conditions was demonstrated. The contribution of bacteria-derived precursors to the total THMs production was found to have a significant dependence on the system's hydraulics, seasonal variables, and the quality of the treated drinking water. Under system conditions that promoted fast bacterial re-growth, the transformation of non-microbial into microbial carbon DBP precursors by the biofilms showed a noticeable effect on the kinetics of THMs formation, especially when a high initial chlorine dose was applied. These conditions included elevated water temperature and high concentrations of nutrients in the influent water. The fraction of THMs formed from microbial sources was found to reach a peak of 12% of the total produced THMs under the investigated scenarios. The results demonstrated the importance of integrating bacterial regrowth dynamics in predictive DBPs formation models. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Haloacetic acid and trihalomethane formation from the chlorination and bromination of aliphatic beta-dicarbonyl acid model compounds.

    Science.gov (United States)

    Dickenson, Eric R V; Summers, R Scott; Croué, Jean-Philippe; Gallard, Hervé

    2008-05-01

    While it is known that resorcinol- and phenol-type aromatic structures within natural organic matter (NOM) react during drinking water chlorination to form trihalomethanes (THMs), limited studies have examined aliphatic-type structures as THM and haloacetic acid (HAA) precursors. A suite of aliphatic acid model compounds were chlorinated and brominated separately in controlled laboratory-scale batch experiments. Four and two beta-dicarbonyl acid compounds were found to be important precursors for the formation of THMs (chloroform and bromoform (71-91% mol/mol)), and dihaloacetic acids (DXAAs) (dichloroacetic acid and dibromoacetic acid (5-68% mol/mol)), respectively, after 24 h at pH 8. Based upon adsorbable organic halide formation, THMs and DXAAs, and to a lesser extent mono and trihaloacetic acids, were the majority (> 80%) of the byproducts produced for most of the aliphatic beta-dicarbonyl acid compounds. Aliphatic beta-diketone-acid-type and beta-keto-acid-type structures could be possible fast- and slow-reacting THM precursors, respectively, and aliphatic beta-keto-acid-type structures are possible slow-reacting DXAA precursors. Aliphatic beta-dicarbonyl acid moieties in natural organic matter, particularly in the hydrophilic fraction, could contribute to the significant formation of THMs and DXAAs observed after chlorination of natural waters.

  3. Natural formation of trihalomethanes (THM) in soils

    Science.gov (United States)

    Huber, Stefan G.; Mulder, Ines; Kotte, Karsten; Williams, Jonathan; Schöler, Heinz F.

    2010-05-01

    The occurrence of organohalogens in the environment was initially attributed to anthropogenic processes; a natural formation seemed to be limited on a few number of compounds. To date, more than 3800 halocarbons are known and identified to be produced through natural reaction pathways. Trihalomethanes (THM), with chloroform being the most common, belong to these compounds and play an important role in photochemical processes of the lower atmosphere, but the current knowledge of the known sources and sinks of trichloromethane is still incomplete. The trichloromethane flux through the environment is estimated at ~660 kt year-1, and 90% of the emissions are of natural origin. Next to offshore seawater contributing ~360 kt year-1 unknown soil processes are the most prominent source (~20 kt year-1).This paper describes a new abiotic source of trichloromethane from the terrestrial environment induced through the oxidation of organic matter by iron(III) and hydrogen peroxide in the presence of chloride. Different organic-rich soils and a series of organic substances regarded as monomeric constituents of humus were investigated for their release of trichloromethane. The influence of iron (III), hydrogen peroxide, halide, and pH on its formation was assayed. The optimal reaction turnover for the representative compound catechol was 58.4 ng of CHCl3 from 1.8 mg of carbon applying chloride and 1.55 μg of CHBr3 from 1.8 mg of carbon applying bromide; resorcin and hydroquinone displayed similar numbers. Results presented in this paper pinpoint 1,2,4,5-tetrahydroxybenzene as playing a key role as intermediate in the formation pathway of the trihalomethanes. The highest THM yields were obtained when applying the oxidized form of 1,2,4,5-tetrahydroxybenzene as THM precursor. These findings are consistent with the well-known degradation pathway starting from resorcin-like dihydroxylated compounds proceeding via further hydroxylation and after halogenation finally ending up in

  4. Characterization of humic substances: implications for trihalomethane formation.

    Science.gov (United States)

    Uyguner, Ceyda Senem; Hellriegel, Christine; Otto, William; Larive, Cynthia K

    2004-03-01

    Humic substances are precursors of carcinogenic trihalomethanes (THMs) formed during disinfection by chlorination in water treatment processes. In an effort to understand the relationship between trihalomethane formation potential (THMFP) and physicochemical properties of humic substances, UV-visible absorbance, fluorescence in emission and synchronous scan modes, and NMR spectra were measured for several aquatic fulvic and humic acids. For comparison, a soil fulvic acid was also examined using these methods. The feasibility of the gradient modified spin-echo (GOSE) NMR experiment to selectively measure singlet resonances arising from isolated protons was examined. In addition, diffusion coefficients were measured for DMSO solutions of the fulvic acids using BPPLED and GOSE-edited pulse sequences. Although none of the methods tested produced results that correlated with THMFP, the GOSE intensities determined for different regions of the NMR spectra did reflect the relative abundance of different types of functional groups produced by lignin oxidation. In addition, the GOSE-edited diffusion results suggest that the isolated protons, those most reactive to chlorination, are more likely contained in the larger molecular weight fractions of fulvic acids.

  5. Second-order chlorine decay and trihalomethanes formation in a pilot-scale water distribution systems.

    Science.gov (United States)

    Li, Cong; Yang, Y Jeffrey; Yu, Jieze; Zhang, Tu-qiao; Mao, Xinwei; Shao, Weiyun

    2012-08-01

    It is well known that model-building of chlorine decay in real water distribution systems is difficult because chlorine decay is influenced by many factors (e.g., bulk water demand, pipe-wall demand, piping material, flow velocity, and residence time). In this paper, experiments were run to investigate the kinetic model of chlorine decay and the formation model of trihalomethanes (THMs) in pilot-scale water distribution systems. Experimental results show that the rate constants of chlorine decay, including wall decay and bulk decay, increasing with temperature. Moreover, the kinetic model of chlorine decay and the formation model of THMs describe experiment data of pilot-scale water distribution systems. The effect of different piping material on chlorine decay and THMs formation were also investigated. The rate constants of chlorine decay are ranked in order: stainless steel pipe, ductile iron pipe, and last, polyethelene pipe because wall decay is the largest in stainless steel pipe than that in other piping material. Correspondingly, the rate of THMs formation follows the order of stainless steel pipe, ductile iron pipe, and last, polyethelene pipe because of less chlorine in bulk water reacting with the trihalomethane formation potential (THMFP).

  6. Chlorine decay and trihalomethane formation following ferrate(VI) preoxidation and chlorination of drinking water.

    Science.gov (United States)

    Li, Cong; Luo, Feng; Dong, Feilong; Zhao, Jingguo; Zhang, Tuqiao; He, Guilin; Cizmas, Leslie; Sharma, Virender K

    2017-08-19

    This paper presents the effect of preoxidation with ferrate(VI) (Fe(VI)O4(2-), Fe(VI)) prior to chlorination on chlorine decay and formation of disinfection by-products in filtered raw water from a full-scale drinking water treatment plant. The rate of chlorine decay became significantly faster as the concentration of ferrate(VI) increased. Chlorine degradation followed two first-order decay reactions with rate constants k1 and k2 for fast and slow decay, respectively. Kinetic modeling established the relationships between k1 and k2 and varying dosages of chlorine and ferrate(VI). When ferrate(VI) was used as a pre-oxidant, the levels of trihalomethanes (trichloromethane (TCM), dichlorobromomethane (DCBM), dibromochloromethane (DBCM), and tribromomethane (TBM)) in water samples decreased as the ferrate(VI) concentration increased. The concentrations of these trihalomethanes followed the order TCM > DCBM ≈ DBCM > TBM. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Trihalomethane formation potential of organic fractions in secondary effluent

    Institute of Scientific and Technical Information of China (English)

    XUE Shuang; ZHAO Qingliang; WEI Liangliang; JIA Ting

    2008-01-01

    Organic matter is known to be the precursor of numerous chlorination by-products. Organic matter in the secondary effluent from the Wenchang Wastewater Treatment Plant(Harbin. China)was physically separated into the following fractions: particulate organic carbon(1. 2-0. 45un), colloidal organic carbon(0. 45-0. 1um), fine colloidal organic carbon(0. 1-0. 025um), and dissolved organic carbon(DOC)(<0. 025um). Moreover, <0. 45 um fraction was chemically separated into hydrophobic acid(HPO-A), hydrophobic neutral(HPO-N), transphilic acid(TPI-A), transphilic neutral(TPI-N), and hydrophilic fraction(HPI). The chlorine reactivity of these organic fractions obtained from both size and XAD fractionations were evaluated. The structural and chemical compositions of the HPO-A. HPO-N. TPI-A. and TPI-N isolates were characterized using elemental analysis(C, H, 0, and N), Fourier trailsform infrared spectroscopy(FT-IR), and proton nuclear magnetic resonance spectroscopy(1H-NMR). Results showed that Doe was dominant in terms of total concentration and trihalomethane formation potential(THMFP). and there was no statistical difference in both specific THMFP(STHMFP)and specific ultraviolet light absorbance among the 0. 45, 0. 1, and 0. 025 um filtrates. HPO-A had the highest STHMFP compared to other chemical fractions. HPO-A, HPO-N, TPI-A, and TPI-N contained 3. 02%-3. 52%of nitrogen. The molar Ratio of H/C increased in the order of HPO. A

  8. Variations in trihalomethane levels in three French water distribution systems and the development of a predictive model.

    Science.gov (United States)

    Mouly, Damien; Joulin, Eric; Rosin, Christophe; Beaudeau, Pascal; Zeghnoun, Abdelkrim; Olszewski-Ortar, Agnès; Munoz, Jean François; Welté, Bénédicte; Joyeux, Michel; Seux, René; Montiel, Antoine; Rodriguez, M J

    2010-10-01

    Epidemiological studies have demonstrated that chlorination by-products in drinking water may cause some types of cancer in humans. However, due to differences in methodology between the various studies, it is not possible to establish a dose-response relationship. This shortcoming is due primarily to uncertainties about how exposure is measured-made difficult by the great number of compounds present-the exposure routes involved and the variation in concentrations in water distribution systems. This is especially true for trihalomethanes for which concentrations can double between the water treatment plant and the consumer tap. The aim of this study is to describe the behaviour of trihalomethanes in three French water distribution systems and develop a mathematical model to predict concentrations in the water distribution system using data collected from treated water at the plant (i.e. the entrance of the distribution system). In 2006 and 2007, samples were taken successively from treated water at the plant and at several points in the water distribution system in three French cities. In addition to the concentrations of the four trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform), many other parameters involved in their formation that affect their concentration were also measured. The average trihalomethane concentration in the three water distribution systems ranged from 21.6 μg/L to 59.9 μg/L. The increase in trihalomethanes between the treated water at the plant and a given point in the water distribution system varied by a factor of 1.1-5.7 over all of the samples. A log-log linear regression model was constructed to predict THM concentrations in the water distribution system. The five variables used were trihalomethane concentration and free residual chlorine for treated water at the plant, two variables that characterize the reactivity of organic matter (specific UV absorbance (SUVA), an indicator developed for the free

  9. Comparison of three-dimensional fluorescence analysis methods for predicting formation of trihalomethanes and haloacetic acids

    Institute of Scientific and Technical Information of China (English)

    Nicolás M.Peleato; Robert C.Andrews

    2015-01-01

    This work investigated the application of several fluorescence excitation-emission matrix analysis methods as natural organic matter (NOM) indicators for use in predicting the formation of trihalomethanes (THMs) and haloacetic acids (HAAs).Waters from four different sources (two rivers and two lakes) were subjected to jar testing followed by 24 hr disinfection by-product formation tests using chlorine.NOM was quantified using three common measures:dissolved organic carbon,ultraviolet absorbance at 254 nm,and specific ultraviolet absorbance as well as by principal component analysis,peak picking,and parallel factor analysis of fluorescence spectra.Based on multi-linear modeling of THMs and HAAs,principle component (PC) scores resulted in the lowest mean squared prediction error of cross-folded test sets (THMs:43.7 (μg/L)2,HAAs:233.3 (μg/L)2).Inclusion of principle components representative of protein-like material significantly decreased prediction error for both THMs and HAAs.Parallel factor analysis did not identify a protein-like component and resulted in prediction errors similar to traditional NOM surrogates as well as fluorescence peak picking.These results support the value of fluorescence excitation-emission matrix-principal component analysis as a suitable NOM indicator in predicting the formation of THMs and HAAs for the water sources studied.

  10. Characterization of dissolved organic matter for prediction of trihalomethane formation potential in surface and sub-surface waters.

    Science.gov (United States)

    Awad, John; van Leeuwen, John; Chow, Christopher; Drikas, Mary; Smernik, Ronald J; Chittleborough, David J; Bestland, Erick

    2016-05-05

    Dissolved organic matter (DOM) in surface waters used for drinking purposes can vary markedly in character dependent on their sources within catchments. The character of DOM further influences the formation of disinfection by products when precursor DOM present in drinking water reacts with chlorine during disinfection. Here we report the development of models that describe the formation potential of trihalomethanes (THMFP) dependent on the character of DOM in waters from discrete catchments with specific land-use and soil textures. DOM was characterized based on UV absorbance at 254 nm, apparent molecular weight and relative abundances of protein-like and humic-like compounds. DOM character and Br concentration (up to 0.5 mg/L) were used as variables in models (R(2)>0.93) of THMFP, which ranged from 19 to 649 μg/L. Chloroform concentration (12-594 μg/L) and relative abundance (27-99%) were first modeled (R(2)>0.85) and from these, the abundances of bromodichloromethane and chlorodibromomethane estimated using power and exponential functions, respectively (R(2)>0.98). From these, the abundance of bromoform is calculated. The proposed model may be used in risk assessment of catchment factors on formation of trihalomethanes in drinking water, in context of treatment efficiency for removal of organic matter.

  11. Modeling Trihalomethane Formation Potential from Wastewater Chlorination

    Science.gov (United States)

    1994-09-01

    chemically with each other, and with living organisms, particularly bacteria ( Manahan , 1991:435). To ensure effective disinfection, to meet the CWA...halogens are strong oxidants and are highly reactive ( Manahan , 1991:504). Chlorine is never found uncombined in nature, it exists only as the...HOCI) according to the following reaction: Cl2 (gas) + H20 =• HOC1 + H+ + Cl The hydrogen is oxidized and the chlorine gas is reduced ( Manahan , 1991

  12. Trihalomethane formation during water disinfection in four water supplies in the Somes river basin in Romania.

    Science.gov (United States)

    Ristoiu, Dumitru; von Gunten, Urs; Mocan, Aurel; Chira, Romeo; Siegfried, Barbara; Haydee Kovacs, Melinda; Vancea, Sidonia

    2009-08-01

    MDLs for CHCl(3), CHBrCl(2), CHBr(2)Cl and CHBr(3) were 0.3, 0.2, 0.3 and 0.6 microg/L, respectively. All kinetic laboratory studies were carried out only with water from the WTP Gilau. The experiments were conducted under two conditions: baseline conditions (pH 7, 21 degrees C, 2.5 mg/L Cl(2)) to gain information about the change of the organic matter in the raw water and seasonally variable conditions to simulate the actual process at the treatment plant and the distribution system. This study shows that the current chlorination practice in the investigated plants complies with the THM drinking water standards of the EU. The THM concentrations in all samples taken in the four treatment plants and distributions systems were below the EU drinking water standard for TTHMs of 100 microg/L. Due to the low bromide levels in the raw waters, the main THM formed in the investigated plants is chloroform. It could also be seen that the THM levels were typically lower in water supplies with groundwater as their water resource. In one plant (Dej) with a pre-ozonation step, a significantly lower (50%) THM formation during post-chlorination was observed. Laboratory chlorination experiments revealed a good correlation between chloroform formation and the consumed chlorine dose. Also, these experiments allowed a semi-quantative prediction of the chloroform formation in the distribution system of Cluj-Napoca. CHCl(3) was the most important trihalomethane species observed after the chlorination of water in all of the sampled months. However, TTHM concentrations did not exceed the maximum permissible value of 100 microg/L (EU). The THM formation rates in the distribution system of Cluj-Napoca have a high seasonal variability. Kinetic laboratory experiments could be used to predict chloroform formation in the Cluj-Napoca distribution system. Furthermore, an empirical model allowed an estimation of the chloroform formation in the Gilau water treatment plant.

  13. Dissolved Organic Carbon and Optical Properties as Indicators of Trihalomethane Formation Potential in an Agricultural Watershed

    Science.gov (United States)

    Pellerin, B. A.; Bergamaschi, B. A.; Spencer, R. G.

    2006-12-01

    Elevated concentrations of dissolved organic carbon (DOC) in the Sacramento-San Joaquin Delta waters may result in the formation of high levels of carcinogenic disinfection byproducts such as trihalomethane during drinking water treatment. The importance of Central Valley agricultural lands as sources of DOC and THM- precursors upstream of the Delta is presently unknown. We are quantifying contributions of DOC and THM- precursors from the Willow Slough watershed, a 425 km2 agriculturally-dominated catchment. During 2006, water samples were collected weekly at the mouth of the watershed and analyzed for DOC concentrations, optical properties (UV absorbance and fluorescence), and trihalomethane formation potential (THMFP). Additional synoptic samples were collected seasonally (winter, spring, summer) from 16 watershed locations and analyzed for optical properties, DOC concentrations, and THMFP. DOC concentrations generally ranged from approximately 2 to 4 mg/L at the watershed outlet during winter and spring, but increased weekly to 8 mg/L following the onset of irrigation. The THMFP at the mouth of the water was correlated with DOC concentration (r2 = 0.87), with higher concentrations during high discharge events and lower concentrations during summer and prolonged rain-free periods. In addition, the species of THM varied between high and low-flow periods, with THM formation dominated by brominated species during low- flow periods and chlorinated species during rainfall-runoff events. Optical characterization of DOC via UV absorbance and fluorescence suggests changes in DOC composition between high- and low-flow periods, likely reflective of changing sources and flowpaths of runoff.

  14. Factors affecting the formation of iodo-trihalomethanes during oxidation with chlorine dioxide.

    Science.gov (United States)

    Guo, Wanhong; Shan, Yingchun; Yang, Xin

    2014-01-15

    Effects of water characteristics, reaction time, temperature, bromide and iodide ion concentrations, oxidant doses, and pH on formation of iodinated trihalomethanes (I-THM) during oxidation of iodide-containing water with chlorine dioxide (ClO2) were investigated. Among the water samples collected from ten water sources, iodoform (CHI3) was the predominant I-THM and trace amount of chlorodiiodomethane (CHClI2) was occasionally found. CHI3 yields correlated moderately with specific UV absorbance (SUVA) (R(2)=0.79), indicating that hydrophobic aromatic content were important precursors. Longer reaction time led to continued formation of CHI3. I-THM containing bromide was also found in waters containing both bromide and iodide, but CHI3 was dominant. The formation of CHI3 was higher at 25°C than 5°C and 35°C. CHI3 formation showed an increase followed by a decrease trend with increasing ClO2 doses and iodide concentrations and the highest yields occurred at iodide to ClO2 molar ratios of 1-2. pH 8 resulted in the highest CHI3 formation. It should be noted that a high iodide concentration was spiked to waters before adding ClO2 and the results may not reflect the formation yields of iodinated THMs in real conditions, but they provide information about formation trend of I-THM during oxidation of ClO2.

  15. Heavy Rainfall Impacts on Trihalomethane Formation in Contrasting Northwestern European Potable Waters.

    Science.gov (United States)

    Delpla, Ianis; Jones, Timothy G; Monteith, Don T; Hughes, David D; Baurès, Estelle; Jung, Aude-Valérie; Thomas, Olivier; Freeman, Chris

    2015-07-01

    There is emerging concern over the impact of extreme events such as heavy rainfall on the quality of water entering the drinking water supply from aboveground sources, as such events are expected to increase in magnitude and frequency in response to climate change. We compared the impact of rainfall events on streamwater quality in four contrasting upland (peatland and mineral soil) and lowland agricultural catchments used to supply drinking water in France (Brittany) and the United Kingdom (North Wales) by analyzing water samples collected before, during, and after specific events. At all four streams, heavy rainfall led to a considerable rise in organic matter concentration ranging from 48 to 158%. Dissolved organic carbon (DOC) quality, as determined using specific ultraviolet absorbance, changed consistently at all sites during rainfall events, with a greater proportion of aromatic and higher molecular weight compounds following the onset of rainfall. However, the change in DOC quality and quantity did not significantly alter the trihalomethane formation potential. We observed small increases in trihalomethane (THM) generation only at the Welsh peatland and agricultural sites and a small decrease at the Brittany agricultural site. The proportion of brominated THMs in chlorinated waters was positively correlated with bromide/DOC ratio in raw waters for all sites and hydrological conditions. These results provide a first indication of the potential implications for surface-based drinking water resources resulting from expected future increases in rainfall event intensity and extension of dry periods with climate changes. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  16. [Effects of bromide and ferric ions on formation of tri-halomethanes during disinfection of drinking water by chlorine].

    Science.gov (United States)

    Zhu, Zhi-Liang; Wang, Jing; Ge, Yuan-Xin; Ma, Hong-Mei; Zhao, Jian-Fu

    2007-06-01

    Effects of bromide and ferric ions on the formation and distribution of tri-halomethanes (THMs) have been investigated. As disinfection by-product (DBP) model precursors of natural water, humic acid solutions were used and a series of experiments were conducted. The results showed that bromide in this reaction system not only contributed to the increase of brominated species, but also the total tri-halomethanes. When the concentration of Br(-) was 1.0 mg/L, the total amount of produced THMs reached to 270% of that without bromide ions. In the presence of bromide, ferric ions decreased the production of THMs at pH 6, but increased the production of THMs at pH 8, especially for the amount of tri-bromomethanes. When the concentration of Fe3+ was 5 mg/L, the amount of produced tri-bromomethanes had an increment of 54% (from 51.7 microg/L to 79.4 microg/L), and the total amount of THMs increased from 113.49 microg/L to 162.09 microg/L. Bromide ions had a significant effect on carcinogenicity risk in disinfection of drinking water by chlorine, and the co-existence of ferric ion and bromide in alkalescent environment can result in the biggest challenge on carcinogenicity risk. Under the condition of 0.2 mg/L Br(-), 5 mg/L Fe3+ and pH 6, the carcinogenicity risk increased 2.5 times than that without Br(-) and Fe3+, and much higher increment of 5.1 times appeared when pH was 8.

  17. A comparison of iodinated trihalomethane formation from chlorine, chlorine dioxide and potassium permanganate oxidation processes.

    Science.gov (United States)

    Zhang, Tian-Yang; Xu, Bin; Hu, Chen-Yan; Lin, Yi-Li; Lin, Lin; Ye, Tao; Tian, Fu-Xiang

    2015-01-01

    This study compared the formation of iodinated trihalomethanes (I-THMs) from iodide-containing raw waters oxidized by chlorine, chlorine dioxide (ClO₂) and potassium permanganate (KMnO₄) at different oxidant concentrations, reaction times, pHs, initial iodide concentrations and bromide to iodide mass ratios. Among the six investigated I-THMs, iodoform was the major species formed during the oxidation using chlorine, ClO₂ and KMnO₄. When oxidant concentration increased from 0.1 to 3.0 mg/L, the formation of I-THMs increased and then decreased for chlorine and ClO₂, but kept increasing for KMnO₄. As the reaction time went by, I-THM concentration increased to a plateau within 10 h (ClO₂ within only 1 h, especially) for all the three oxidants. I-THM formation gradually increased from pH 3.0 to 9.0 and remained stable at pH values higher than 7.5 for chlorine; however, for ClO₂ and KMnO₄ the highest I-THM formation showed at pH 7.0 and 7.5, respectively. As initial iodide concentration increased from 20 to 800 μg/L, the total amount and species of I-THMs increased for the three oxidants. Iodide contributed to I-THM formation much more significantly than bromide.

  18. Trihalomethane formation potential of shrimp farm effluents in Chachoengsao Province, Thailand

    Directory of Open Access Journals (Sweden)

    Aweewan Mangmeechai

    2004-02-01

    Full Text Available Shrimp farm effluents along Bangpakong River in Chachoengsao Province, Thailand, were evaluated for their trihalomethane formation potential (THMFP, which were shown to be in the range of 810-3,100 µg/L. Samples from river locations, both upstream and downstream from these selected farms, were also tested for their existing THMFP. These river samples were illustrated to have notably lower level of THMFP than the shrimp farm effluents. The downstream concentration was, however, found to be significantly higher than the upstream (as much as 5 times. This indicated that the contamination of shrimp farm effluents could have increased the formation potential of THMs in the natural water source. The experimental results showed a positive correlation between salinity and THMFP. The formation of various THM species depended significantly on the level of salinity in the water sample. Low salinity (0-5 ppt often led to a high formation of chloroform and bromodichloromethane while high salinity (5-15 ppt resulted in a great quantity of dibromochloromethane and bromoform. FTIR spectra of the samples before and after chlorination suggested that the functional groups involved in the reaction were hydroxyl group, amines group, aromatic ring, aliphatic chloro compounds and aliphatic bromo compounds, whereas C-O was the product from the reaction.

  19. N-nitrosodimethylamine and trihalomethane formation and minimisation in Southeast Queensland drinking water.

    Science.gov (United States)

    Knight, Nicole; Watson, Kalinda; Farré, Maria José; Shaw, Glen

    2012-07-01

    This study assesses the prevalence of disinfection by-product (DBP) precursors in some Southeast Queensland drinking water sources by conducting formation potential experiments for the four regulated trihalomethanes (THMs), and the potent carcinogen, N-nitrosodimethylamine (NDMA). NDMA formation potentials were consistently low (Water Guideline (250 μg/L). NDMA concentration of finished drinking waters was also monitored and found to be UV/H(2)O(2) pre-treatment was effective in producing water with very low THMs concentrations, and UV irradiation was an effective method for NDMA degradation. H(2)O(2) was not required for the observed NDMA degradation to occur. Coagulation using alum, ferric chloride or poly(diallyldimethylammonium chloride) (polyDADMAC) was ineffective in removing DBPs precursors from the source water studied, irrespective of the low dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) attained. Rather, coagulation with polyDADMAC caused an increase in NDMA formation potential upon chloramination, and all coagulants led to an increased tTHM formation potential upon chlorination due to the high bromide concentration of the source water studied.

  20. Mechanisms and kinetics study on the trihalomethanes formation with carbon nanoparticle precursors.

    Science.gov (United States)

    Du, Tingting; Wang, Yingying; Yang, Xin; Wang, Wei; Guo, Haonan; Xiong, Xinyu; Gao, Rui; Wuli, Xiati; Adeleye, Adeyemi S; Li, Yao

    2016-07-01

    With lots of carbon nanoparticles (CNPs) applied in the industry, the possibilities of their environmental release have received much attention. As the CNPs may enter drinking water systems, and persist in water and wastewater treatment systems, their possible reaction with disinfectants should be studied. In this study, the formation of trihalomethanes (THMs) with 5 types of carbon nanotubes (CNTs), graphene oxide (GO) and reduced graphene oxide (rGO) was investigated. All CNPs could act as precursors of THMs in aqueous phase. Total concentrations of THMs formed with CNPs varied from 0.24 to 0.95 μM, much lower than that formed from chlorinated Suwannee River Natural Organic Matter (SRNOM) (approximately 9 μM). The kinetics of THMs formation with GO was 0.0814 M(-1) s(-1), which is higher than most of the chlorinated humic acid obtained from different natural waters. The study indicates that during chlorination, C-Cl bond could be formed on the surface of CNPs. However, carbon atoms at the middle of two meta-positioned OH groups on the benzene ring are more active and may prefer to form THMs with chlorine oxidation. The influences of pH and reactant doses on the formation of THMs were also discussed.

  1. Characterization of haloacetaldehyde and trihalomethane formation potentials during drinking water treatment.

    Science.gov (United States)

    Mao, Yu-Qin; Wang, Xiao-Mao; Guo, Xian-Fen; Yang, Hong-Wei; Xie, Yuefeng F

    2016-09-01

    Haloacetaldehydes (HAs) are the third prevalent group of disinfection by-products (DBPs) of great health concern. In this study, their formation and speciation during chlorination were investigated for raw and process waters collected at three O3-biological activated carbon (BAC) advanced drinking water treatment plants. The results showed that all HA formation potentials (HAFPs) were highly enhanced whenever ozone was applied before or after conventional treatment. Sand filtration and BAC filtration could substantially reduce HAFPs. Trihalomethanes (THMs) were also measured to better understand the role of HAs in DBPs. Very different from HAFPs, THMFPs kept decreasing with the progress of treatment steps, which was mainly attributed to the different precursors for HAs and THMs. Brominated HAs were detected in bromide-containing waters. Chloral hydrate (CH) contributed from 25% to 48% to the total HAs formed in waters containing 100-150 μg L(-1) bromide, indicating the wide existence of other HAs after chlorination besides CH production. In addition, bromide incorporation factor (BIF) in HAs and THMs increased with the progress of treatment steps and the BIF values of THMs were generally higher than those of HAs. The BAC filtration following ozonation could significantly reduce HA precursors produced from ozonation but without complete removal. The brominated HAFPs in the outflow of BAC were still higher than their levels in the raw water. As a result, O3-BAC combined treatment was effective at controlling the total HAs, whereas it should be cautious for waters with high bromide levels.

  2. Chlorination or monochloramination: Balancing the regulated trihalomethane formation and microbial inactivation in marine aquaculture waters

    KAUST Repository

    Sanawar, Huma

    2017-08-15

    Disinfection methods like chlorination are increasingly used to sanitize the water, equipment, tools and surfaces in aquaculture facilities. This is to improve water quality, and to maintain a hygienic environment for the well-being of aquatic organisms. However, chlorination can result in formation of regulated disinfection byproducts (DBPs) that can be carcinogenic and toxic. This study aims to evaluate if an optimal balance can be achieved between minimal regulated DBP formation and effective microbial inactivation with either chlorination or monochloramination for application in the Red Sea aquaculture waters. Upon chlorination, the concentration of total trihalomethanes (THMs), primarily bromoform, exceeded the regulatory limit of 80μg/L even at the lowest tested concentration of chlorine (1mg/L) and contact time (1h). Comparatively, regulated THMs concentration was only detectable at 30μg/L level in one of the three sets of monochloraminated marine aquaculture waters. The average log reduction of antibiotic-resistant bacteria (ARB) by chlorine ranged from 2.3-log to 3.2-log with different contact time. The average log reduction of ARB by monochloramine was comparatively lower at 1.9 to 2.9-log. Although viable Staphylococcus aureus was recovered from monochloraminated samples as opposed to chlorinated samples, the abundance of S. aureus was not high enough to result in any significant microbial risks. Both chlorination and monochloramination did not provide any significant improvement in the reduction of antibiotic resistance genes (ARGs). This study demonstrates that a systematic evaluation is needed to determine the optimal disinfectant required to balance both microbial and chemical risks. Compared to chlorine, monochloramine may be a more appropriate disinfection strategy for the treatment of aquaculture effluents prior to discharge or for recirculatory use in the aquaculture facility.

  3. Modeling daily variation of trihalomethane compounds in drinking water system, Houston, Texas.

    Science.gov (United States)

    Chaib, Embarka; Moschandreas, Demetrios

    2008-03-01

    Total trihalomethanes (TTHM) concentrations vary widely and periodically between 70 and 130 ppb. Data from the National Environmental Services Laboratory, Houston, Texas indicate that pH and free residual chlorine contribute minimally to the wide variability of TTHM levels. Temperature variation in drinking fluctuates from 11 to 27 degrees C. The objective of this research is to formulate a model that delineates more clearly the daily variations of the most prevalent volatile trihalomethane by-products: chloroform (CHCl3), bromodichloromethane (CHBr2Cl), and bromoform (CHBr3) levels from drinking water. This model simulates the daily fluctuation of THM at a single location and at any time during the day as a function of the water temperature and the average concentration of TTHM, which can be estimated. The hypothesis of this study is that observed daily fluctuations of TTHM, CHCl3, CHCl2Br, CHClBr2, and CHBr3 are periodic. This hypothesis is tested using autocorrelation functions and it is shown that for the series of pH the correlation coefficient is maximal at zero lags, rapidly decreases to zero, and increases again between 4- and 6-h period. Such pattern suggests random fluctuation unrelated to time. However, the series of free residual chlorine, temperature, TTHM, CHCl3, CHCl2Br, CHClBr2, and CHBr3 suggest a different pattern. The correlation coefficient increases when the time-shift approaches 24 h. These repetitions in fluctuation of content over a 24-h period are statistically significant. The model formulated in this study provides insights in TTHM variation and is a necessary tool to reduce the error when estimating potential risk from exposure to trihalomethane compounds in drinking water system. In general, calculation of potential risk by using a value measured early morning or late afternoon concentrations were found minimal lead to an underestimation of the population risk.

  4. Natural organic matter characterization by HPSEC and its contribution to trihalomethane formation in Athens water supply network.

    Science.gov (United States)

    Samios, Stelios A; Golfinopoulos, Spyros K; Andrzejewski, Przemyslaw; Świetlik, Joanna

    2017-08-24

    Samples from the two main watersheds that provide Athens Water Supply and Sewerage Company (AWSSC) with raw water were examined for Dissolved Organic Carbon (DOC) and for their molecular weight distribution (MWD). In addition, water samples from water treatment plants (WTPs) and from the water supply network were examined for trihalomethane (THMs) levels. The main purpose of this study was to reveal the molecular composition of natural organic matter (NOM) and identify the individual differences between NOM from the two main Athens watersheds. High-performance size exclusion chromatography (HPSEC), a relatively simple technique, was applied to determine different NOM fractions' composition according to molecular weight. Various THM levels in the supply network of Athens are illustrated as a result of the different reservoirs' water qualities, and a suggestion for a limited application of chlorine dioxide is made in order to minimize THM formation.

  5. Reduction of trihalomethane formation and detoxification of microcystins in tap water by ozonation.

    Science.gov (United States)

    Thapsingkaew, Orapin; Ruangyuttikarn, Werawan; Kijjanapanich, Vilailuck

    2008-06-01

    The efficiency of ozonation in comparison to chlorination for removal of microcystins and production of trihalomethanes (THMs) in water was investigated. One hundred and ninety water samples of ozone and chlorine treated water were collected at a water treatment plant between August 2004 and March 2005. The level of THMs, total organic carbon and residual chlorine were determined. Protein phosphatase 2A inhibition assay was used to detect microcystins and the presence of microcystins was confirmed by HPLC. The results show that 91.5% of the THM species in treated water was chloroform and 8.5% was bromodichloromethane. The mean THM level+/- standard error of mean in chlorinated water (CW) (45.1+/-3.0 microg/L) was higher than the mean of THM level in ozonated water (OW) (18.6+/-2.2 microg/L). In addition, no OW sample exceeded the first stage U.S. EPA maximum THM contaminant level for drinking water (80 microg/L) and only 8% of these samples exceeded the second stage level (40 microg/L). On the other hand, 3% of CW samples exceeded 80 microg/L and 68% exceeded the 40 microg/L level. The microcystin level in all water samples was below the WHO guideline value (1 microg/L) for drinking water.

  6. Iodinated trihalomethane formation during chloramination of iodate-containing waters in the presence of zero valent iron.

    Science.gov (United States)

    Xia, Ying; Lin, Yi-Li; Xu, Bin; Hu, Chen-Yan; Gao, Ze-Chen; Chu, Wen-Hai; Gao, Nai-Yun

    2017-11-01

    Iodide (I(-)) and iodinated X-ray contrast media (ICM) are the primary iodine sources for the formation of iodinated disinfection byproducts (I-DBPs), and iodate (IO3(-)) is believed to be a desired sink of iodine in water. This study found that highly cytotoxic iodinated trihalomethanes (I-THMs) also can be generated from iodate-containing waters (without any other iodine sources) in the presence of zero valent iron (ZVI) during chloramination, which could be a big issue in the wide usage of iron pipes. The effect of major factors including ZVI dosage, NH2Cl and IO3(-) concentrations, initial pH, Br(-)/IO3(-) molar ratio, phosphate concentration, iron corrosion scales (goethite and hematite) on the formation of I-THMs were investigated. Formation of I-THMs from IO3(-) increased with the increase of ZVI dosage, IO3(-) and NH2Cl concentrations. Chloramines can also remarkably accelerate the reduction of IO3(-) by ZVI. Peak I-THM formation was found at pH 8. As the Br(-)/IO3(-) molar ratio increased from 0 to 20, I-THM formation considerably enhanced, especially for the bromine-incorporated species. Goethite and hematite enhanced the formation of I-THMs in the presence of ZVI. Additionally, a significant suppression on I-THM formation was observed with the addition of phosphate. Considering that a large number of water distribution networks contain unlined cast iron pipes, transformation of IO3(-) in the presence of ZVI during chloramination may contribute to the formation of I-THMs in such systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. TiO2 photocatalysis of natural organic matter in surface water: impact on trihalomethane and haloacetic acid formation potential.

    Science.gov (United States)

    Liu, Sanly; Lim, May; Fabris, Rolando; Chow, Christopher; Drikas, Mary; Amal, Rose

    2008-08-15

    In this study, changes in the physical and structural properties of natural organic matter (NOM) during titanium dioxide photocatalytic oxidation process were investigated using several complementary analytical techniques. Potential of the treated water to form trihalomethanes (THMs) and haloacetic acids (HAAs) was also studied. High-performance size exclusion chromatography analysis showed that NOM with apparent molecular weights of 1-4 kDa were preferentially degraded, leading to the formation of lower molecular weight organic compounds. Resin fractionation of the treated water demonstrated that the photocatalytic oxidation changed the affinity of the bulk organic character from predominantly hydrophobic to more hydrophilic. Short chain aldehydes and ketones were identified by mass spectroscopy as one of the key degradation products. The addition of hydrogen peroxide to photocatalysis was found to increase the degradation kinetics but did not affect the reaction pathway, thus producing similar degradation end products. The amount of THMs normalized per dissolved organic carbon (specific THM) formed upon chlorination of NOM treated with photocatalytic oxidation was reduced from 56 to 10 microg/mg. In contrast, the specific HAAs formation potential of the treated water remained relatively unchanged from the initial value of 38 microg/mg, which could be due to the presence of hydrophilic precursor compounds that were formed as a result of the photocatalytic oxidation process.

  8. Modelling the regional variability of the probability of high trihalomethane occurrence in municipal drinking water.

    Science.gov (United States)

    Cool, Geneviève; Lebel, Alexandre; Sadiq, Rehan; Rodriguez, Manuel J

    2015-12-01

    The regional variability of the probability of occurrence of high total trihalomethane (TTHM) levels was assessed using multilevel logistic regression models that incorporate environmental and infrastructure characteristics. The models were structured in a three-level hierarchical configuration: samples (first level), drinking water utilities (DWUs, second level) and natural regions, an ecological hierarchical division from the Quebec ecological framework of reference (third level). They considered six independent variables: precipitation, temperature, source type, seasons, treatment type and pH. The average probability of TTHM concentrations exceeding the targeted threshold was 18.1%. The probability was influenced by seasons, treatment type, precipitations and temperature. The variance at all levels was significant, showing that the probability of TTHM concentrations exceeding the threshold is most likely to be similar if located within the same DWU and within the same natural region. However, most of the variance initially attributed to natural regions was explained by treatment types and clarified by spatial aggregation on treatment types. Nevertheless, even after controlling for treatment type, there was still significant regional variability of the probability of TTHM concentrations exceeding the threshold. Regional variability was particularly important for DWUs using chlorination alone since they lack the appropriate treatment required to reduce the amount of natural organic matter (NOM) in source water prior to disinfection. Results presented herein could be of interest to authorities in identifying regions with specific needs regarding drinking water quality and for epidemiological studies identifying geographical variations in population exposure to disinfection by-products (DBPs).

  9. Seasonal variation effects on the formation of trihalomethane during chlorination of water from Yangtze River and associated cancer risk assessment.

    Science.gov (United States)

    Liu, Shaogang; Zhu, Zhiliang; Fan, Chenfeng; Qiu, Yanling; Zhao, Jianfu

    2011-01-01

    For the system of water samples collected from Yangtze River, the effects of seasonal variation and Fe(III) concentrations on the formation and distribution of trihalomethanes (THMs) during chlorination have been investigated. The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA. The results indicated that the average concentration of THMs (100.81 microg/L) in spring was significantly higher than that in other seasons, which was related to the higher bromide ion concentration resulted from the intrusion of tidal saltwater. The total cancer risk in spring reached 8.23 x 10(-5) and 8.86 x 10(-5) for males and females, respectively, which were about two times of those in summer under the experimental conditions. Furthermore, it was found that the presence of Fe(III) resulted in the increased level of THMs and greater cancer risk from exposure to humans. Under weak basic conditions, about 10% of the increment of THMs from the water samples in spring was found in the presence of 0.5 mg/L Fe(III) compared with the situation without Fe(III). More attention should be given to the effect of the coexistence of Fe(III) and bromide ions on the risk assessment of human intake of THMs from drinking water should be paid more attention, especially in the coastland and estuaries.

  10. Seasonal variation effects on the formation of trihalomethane during chlorination of water from Yangtze River and associated cancer risk assessment

    Institute of Scientific and Technical Information of China (English)

    Shaogang Liu; Zhiliang Zhu; Chenfeng Fan; Yanling Qiu; Jianfu Zhao

    2011-01-01

    For the system of water samples collected from Yangtze River,the effects of seasonal variation and Fe(Ⅲ) concentrations on the formation and distribution of trihalomethanes (THMs) during chlorination have been investigated.The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA.The results indicated that the average concentration of THMs (100.81 μg/L) in spring was significantly higher than that in other seasons,which was related to the higher bromide ion concentration resulted from the intrusion of tidal saltwater.The total cancer risk in spring reached 8.23 × 10-5 and 8.86 × 10-5 for males and females,respectively,which were about two times of those in summer under the experimental conditions.Furthermore,it was found that the presence of Fe(Ⅲ) resulted in the increased level of THMs and greater cancer risk from exposure to humans.Under weak basic conditions,about 10% of the increment of THMs from the water samples in spring was found in the presence of 0.5 mg/L Fe(Ⅲ) compared with the situation without Fe(Ⅲ).More attention should be given to the effect of the coexistence of Fe(Ⅲ) and bromide ions on the risk assessment of human intake of THMs from drinking water should be paid more attention,especially in the coastland and estuaries.

  11. Phototransformation of iodate by UV irradiation: Kinetics and iodinated trihalomethane formation during subsequent chlor(am)ination

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Fu-Xiang [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Hu, Xiao-Jun, E-mail: hu-xj@mail.tsinghua.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Xu, Bin; Zhang, Tian-Yang; Gao, Yu-Qiong [State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China)

    2017-03-15

    Highlights: • IO{sub 3}{sup −} can be photodegraded by UV irradiation with pseudo-first order kinetics. • Solution pH has no remarkable influence on the photodegradation rate of IO{sub 3}{sup −}. • The I{sup −} and HOI derived from the photoreduction of IO{sub 3}{sup −} were determined. • The presence of NOM greatly enhanced the photolysis rate of IO{sub 3}{sup −}. • NOM sources can affect the formation of I-THMs in UV-chlor(am)ination of IO{sub 3}{sup −}. - Abstract: The photodegradation of IO{sub 3}{sup −} at 254 nm and the formation of iodinated trihalomethanes (I-THMs) during subsequent chlorination or chloramination in the presence of natural organic matter (NOM) were investigated in this study. The thermodynamically stable IO{sub 3}{sup −} can be degraded by UV irradiation with pseudo-first order kinetics and the quantum yield was calculated as 0.0591 mol einstein{sup −1}. Solution pH posed no remarkable influence on the photolysis rate of IO{sub 3}{sup −}. The UV phototransformation of IO{sub 3}{sup −} was evidenced by the determination of iodide (I{sup −}) and hypoiodous acid (HOI) in solution. NOM sources not only enhanced the photodegradation rate of IO{sub 3}{sup −} by photoejecting solvated electrons, but also greatly influenced the production I-THMs in subsequent chlor(am)ination processes. In UV irradiation and sequential oxidation processes by chlorine or chloramine, the I-THMs formation was susceptible to NOM sources, especially the two major fractions of aqueous humic substances (humic acid and fulvic acid). The toxicity of disinfected waters greatly increased in chloramination over chlorination of the UV photodecomposed IO{sub 3}{sup −}, as far more I-THMs especially CHI{sub 3}, were formed. As “the fourth iodine source” of iodinated disinfection by-products, the occurrence, transportation and fate of IO{sub 3}{sup −} in aquatic environment should be of concern instead of being considered a desired

  12. Second-Order Chlorine Decay and Trihalomethanes Formation in a Pilot-Scale Water Distribution Systems

    Science.gov (United States)

    It is well known that model-building of chlorine decay in real water distribution systems is difficult because chlorine decay is influenced by many factors (e.g., bulk water demand, pipe-wall demand, piping material, flow velocity, and residence time). In this paper, experiments ...

  13. [Human exposure to trihalomethanes in drinking water].

    Science.gov (United States)

    Tominaga, M Y; Midio, A F

    1999-08-01

    Halogenated hydrocarbon compounds, some of them recognized as carcinogenic to different animal species can be found in drinking water. Chloroform, bromodichloromethane, dibromochloromethane and bromoform are the most important trihalomethanes found in potable water. They are produced in natural waters during chlorinated desinfection by the halogenation of precursors, specially humic and fulvic compounds. The review, in the MEDLINE covers the period from 1974 to 1998, presents the general aspects of the formation of trihalomethanes, sources of human exposure and their toxicological meaning for exposed organisms: toxicokinetic disposition and spectrum of toxic effects (carcinogenic, mutagenic and teratogenic).

  14. The effect of chlorine dioxide on the formation of trihalomethanes; Dioxido de cloro y su efecto en la formacion de trihalometanos

    Energy Technology Data Exchange (ETDEWEB)

    Ciurana de Gay, C.

    2000-07-01

    The chlorine dioxide presents a high reactivity with certain organic and inorganic compounds. In the process of making water fit to drink, one of the most valued characteristics of the chlorine dioxide is the oxidation of the precursors of trihalomethanes, that allows their decrease in the drinking water. The generation of the chlorine dioxide is the oxidation of the precursors of trihalomethanes, that allows their decrease in the drinking water. The generation of the chlorine dioxide must be made at the dosage point. Both, the generation and its control can be made in an easy way. Since a few years ago, in the ETAP, in Montfulla, some researches are being carried out in order to decrease the concentration of trihalomethanes. In this work it is exposed the generation the dosage control and the reduction of trihalomethanes obtained through the dosage of the chlorine dioxide at different doses. (Author) 8 refs.

  15. Tracing dissolved organic carbon and trihalomethane formation potential between source water and finished drinking water at a lowland and an upland UK catchment.

    Science.gov (United States)

    Brooks, Emma; Freeman, Christopher; Gough, Rachel; Holliman, Peter J

    2015-12-15

    Rising dissolved organic carbon (DOC) concentrations in many upland UK catchments represents a challenge for drinking water companies, in particular due to the role of DOC as a precursor in the formation of trihalomethanes (THMs). Whereas traditionally, the response of drinking water companies has been focussed on treatment processes, increasingly, efforts have been made to better understanding the role of land use and catchment processes in affecting drinking water quality. In this study, water quality, including DOC and THM formation potential (THMFP) was assessed between the water source and finished drinking water at an upland and a lowland catchment. Surprisingly, the lowland catchment showed much higher reservoir DOC concentrations apparently due to the influence of a fen within the catchment from where a major reservoir inflow stream originated. Seasonal variations in water quality were observed, driving changes in THMFP. However, the reservoirs in both catchments appeared to dampen these temporal fluctuations. Treatment process applied in the 2 catchments were adapted to reservoir water quality with much higher DOC and THMFP removal rates observed at the lowland water treatment works where coagulation-flocculation was applied. However, selectivity during this DOC removal stage also appeared to increase the proportion of brominated THMs produced. Copyright © 2015. Published by Elsevier B.V.

  16. Assessing trihalomethanes (THMs) and N-nitrosodimethylamine (NDMA) formation potentials in drinking water treatment plants using fluorescence spectroscopy and parallel factor analysis.

    Science.gov (United States)

    Yang, Liyang; Kim, Daekyun; Uzun, Habibullah; Karanfil, Tanju; Hur, Jin

    2015-02-01

    The formation of disinfection byproducts (DBPs) is a major challenge in drinking water treatments. This study explored the applicability of fluorescence excitation-emission matrices and parallel factor analysis (EEM-PARAFAC) for assessing the formation potentials (FPs) of trihalomethanes (THMs) and N-nitrosodimethylamine (NDMA), and the treatability of THM and NDMA precursors in nine drinking water treatment plants. Two humic-like and one tryptophan-like components were identified for the samples using PARAFAC. The total THM FP (TTHM FP) correlated strongly with humic-like component C2 (r=0.874), while NDMA FP showed a moderate and significant correlation with the tryptophan-like component C3 (r=0.628). The reduction by conventional treatment was more effective for C2 than C3, and for TTHM FP than NDMA FP. The treatability of DOM and TTHM FP correlated negatively with the absorption spectral slope (S275-295) and biological index (BIX) of the raw water, but it correlated positively with humification index (HIX). Our results demonstrated that PARAFAC components were valuable for assessing DBPs FP in drinking water treatments, and also that the raw water quality could affect the treatment efficiency.

  17. Molecular size distribution of dissolved organic matter in water of the Pearl River and trihalomethane formation characteristics with chlorine and chlorine dioxide treatments.

    Science.gov (United States)

    Zhao, Zhen-Ye; Gu, Ji-Dong; Fan, Xiao-Jun; Li, Hai-Bo

    2006-06-30

    River water sample was collected from Guangzhou section of the Pearl River to investigate soluble organic fractions and formation of trihalomethane (THMs) after chlorine and chlorine dioxide treatments. The water sample was passed through Amicon YC-05, YM-1, YM-3, YM-10, YM-30, YM-100 and ZM-500 series membranes after a pre-treatment. The molecular weight distribution and the specific ultra-violet absorbance (SUVA(254)) of each fraction obtained from membrane were analyzed, and these fractions were further disinfected with chlorine and chlorine dioxide. The results showed that reverse osmosis (RO) fraction contained mainly dissolved organic matter (DOM) from the water sample, suggesting that the water has been highly contaminated by anthropogenic activities. Meanwhile, the THMs concentration and SUVA(254) increased gradually as the molecular weight of the obtained fractions reduced, indicating that the low molecular weight DOM was the major THMs precursor in the disinfection process with chlorine and chlorine dioxide. The results suggest that THMs in source water of Pearl River could be effectively reduced when pollution of human activity is greatly controlled. Between the two disinfection processes tested, chlorine dioxide produced less THMs than chlorine in this study.

  18. 氯胺消毒过程中碘代三卤甲烷生成的影响因素%Factors Affecting Iodo-trihalomethane Formation during Chloramination of Micro-polluted Raw Water

    Institute of Scientific and Technical Information of China (English)

    孙仲昊; 徐斌; 胡晨燕; 夏圣骥; 高乃云; 叶涛

    2013-01-01

    碘代消毒副产物的“三致”特性远高于氯代和溴代消毒副产物,是近年来饮用水领域颇受关注的一类新兴消毒副产物.以微污染原水为研究对象,系统研究了其在氯胺消毒条件下碘代三卤甲烷类消毒副产物生成的影响因素.研究发现,在原水中存在一定浓度碘离子的条件下,采用氯胺消毒可产生较高浓度的碘代三卤甲烷类消毒副产物,其中以三碘甲烷为主;碘代三卤甲烷的生成总量随着反应时间的增加而增加;碘代三卤甲烷的生成量和组成受氯胺投加量的影响较大,在氯胺投加量较低的情况下主要生成三碘甲烷和一溴二碘甲烷,在氯胺投加量较高的情况下生成一氯二碘甲烷、二氯一碘甲烷、一溴二碘甲烷和三碘甲烷四种碘代三卤甲烷;碘代三卤甲烷的生成总量以及三碘甲烷在总碘代三卤甲烷中的比例随着碘离子浓度的增加而提高;总体上,氯胺化过程中碘代三卤甲烷的生成总量随着pH值的升高而增加.%Iodinated disinfection byproducts contain higher mutagenesis, carcinogenesis and terat-ogenesis than chlorinated and brominated disinfection byproducts. Increasing attention is focused on these emerging byproducts in the drinking water field recently. The factors affecting iodo-trihalomethane formation during chloramination of micro-polluted raw water were investigated. The results showed that higher concentrations of iodo-trihalomethanes would be produced during chloramination in the presence of iodide in raw water, in which iodoform was predominant. The total amount of iodo-trihalomethanes increased with reaction time, and the total amount and species of iodo-trihalomethanes were influenced by chlora- mine dosage. Iodoform and bromodiiodomethane were generated by a relatively low chloramine dosage. With high chloramine dosage, four kinds of iodo-trihalomethanes including chlorodiiodomethane, di-chloroiodomethane, bromodiiodomethane

  19. Kinetic modeling and energy efficiency of UV/H₂O₂ treatment of iodinated trihalomethanes.

    Science.gov (United States)

    Xiao, Yongjun; Zhang, Lifeng; Yue, Junqi; Webster, Richard D; Lim, Teik-Thye

    2015-05-15

    Photodegradation of I-THMs including CHCl2I and CHI3 by the UV/H2O2 system was investigated in this study. CHCl2I and CHI3 react rapidly with hydroxyl radical (OH) produced by the UV/H2O2 system, with second-order rate constants of 8.0 × 10(9) and 8.9 × 10(9) M(-1) s(-1), respectively. A fraction of CHCl2I could be completely mineralized within 15 min and the remaining fraction was mainly converted to formic acid (HCO2H). Cl(-) and I(-) were identified as the predominant end-products. No ClO3(-) was observed during the photodegradation process, while IO3(-) was detected but at less than 2% of the total liberated iodine species at the end of the reaction. The effects of pH, H2O2 dose, and matrix species such as humic acid (HA), HCO3(-), SO4(2-), Cl(-), NO3(-) on the photodegradation kinetics were evaluated. The steady-state kinetic model has been proven to successfully predict the destruction of CHCl2I and CHI3 by UV/H2O2 in different water matrices. On this basis, the kinetic model combined with electrical energy per order (EE/O) concept was applied to evaluate the efficiency of the photodegradation process and to optimize the H2O2 dose for different scenarios. The optimal H2O2 doses in deionized (DI) water, model natural water, and surface water are estimated at 5, 12, and 16 mg L(-1), respectively, which correspond to the lowest total energy consumption (EE/Ototal) of 0.2, 0.31, and 0.45 kWhm(-3)order(-1). Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Feasibility Study of a Simple and Low-Cost Device for Monitoring Trihalomethanes Presence in Water Supply Systems Based on Statistical Models

    Directory of Open Access Journals (Sweden)

    Almudena Rivadeneyra

    2014-11-01

    Full Text Available This paper describes a new method for predicting trihalomethanes (THMs presence in networks of water supply systems, using a low-cost device that permits a fast monitoring of concentrations without need of complex analysis made in laboratories. This method, based on statistical models, allows the estimation of THM concentration by monitoring parameters whose determination is direct and easy, and therefore, THM presence can be carried out in real-time. These parameters values are introduced in a multiple regression model resulting in the concentration of THMs levels. This model has taken into account parameters compulsory in water quality analysis and it has been shown that six parameters are enough to determine accurately THM concentration. In addition, the feasibility of a low-cost device that directly gives THM concentration is demonstrated. This device can be easily designed to be transported to different points of the water supply network where it is intended to make control campaigns.

  1. Inhibition of trihalomethane formation in city water by radiation-ozone treatment and rapid composting of radiation disinfected sewage sludge

    Science.gov (United States)

    Takehisa, M.; Arai, H.; Arai, M.; Miyata, T.; Sakumoto, A.; Hashimoto, S.; Nishimura, K.; Watanabe, H.; Kawakami, W.; Kuriyama, I.

    Humic acid and Fulvic acid in natural water are precursors of carcinogenic THM which is formed during chlorine disinfection in city water processing. The radiation-oxidation process in the presence of ozone is effective to remove the precursors. The THM formation was reduced more than the decrease in TOC by the combination treatment. This is mainly due to a change in the chemical structure of the oxidation products. A composting of radiation disinfected sludge cake for agricultural reuse could be achieved within 3 days primary fermentation in a sewage plant. The rapid fermentation with use of radiation is effective to scale down of a fermentor of composting plant and the process reduces a health risk from the workers as well as final users.

  2. Formation of iodo-trihalomethanes, iodo-acetic acids, and iodo-acetamides during chloramination of iodide-containing waters: Factors influencing formation and reaction pathways

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shaogang [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085 (China); Guangxi Colleges and Universities Key Laboratory of Food Safety and Pharmaceutical Analytical Chemistry, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530006, Guangxi (China); Li, Zhenlin [Guangxi Colleges and Universities Key Laboratory of Food Safety and Pharmaceutical Analytical Chemistry, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530006, Guangxi (China); Dong, Huiyu [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085 (China); Goodman, Bernard A. [College of Physical Science and Engineering, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, 520004, Guangxi (China); Qiang, Zhimin, E-mail: qiangz@rcees.ac.cn [Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085 (China)

    2017-01-05

    This study investigated systematically the factors influencing the formation of iodinated disinfection by-products (I-DBPs) during chloramination of I{sup −}-containing waters, including reaction time, NH{sub 2}Cl dose, I{sup −} concentration, pH, natural organic matter (NOM) concentration, Br{sup −}/I{sup −} molar ratio, and water matrix. Among the I-DBPs detected, iodoform (CHI{sub 3}), iodoacetic acid (IAA), diiodoacetic acid (DIAA), triiodoacetic acid (TIAA), and diiodoacetamide (DIAcAm) were the major species produced from reactions between reactive iodine species (HOI/I{sub 2}) and NOM. A kinetic model involving the reactions of NH{sub 2}Cl auto-decomposition, iodine species transformation and NOM consumption was developed, which could well describe NH{sub 2}Cl decay and HOI/I{sub 2} evolution. Higher concentrations of CHI{sub 3}, IAA, DIAA, TIAA, and DIAcAm were observed in chloramination than in chlorination, whereas IO{sub 3}{sup −} was only formed significantly in chlorination. Maximum formation of I-DBPs occurred at pH 8.0, but acidic conditions favored the formation of iodinated haloacetic acids and DIAcAm. Increasing Br{sup −}/I{sup −} molar ratio from 1 to 10 did not increase the total amount of I-DBPs, but produced more bromine-substituting species. In addition, chloramination of 18 model compounds indicated that low-SUVA{sub 254} (specific ultraviolet absorbance at 254 nm) NOM generally favored the formation of I-DBPs compared to high-SUVA{sub 254} NOM. Finally, potential pathways for I-DBPs formation from chloramination of NOM were proposed.

  3. Effects of Ca(OH)2 assisted aluminum sulfate coagulation on the removal of humic acid and the formation potentials of tri-halomethanes and haloacetic acids in chlorination

    Institute of Scientific and Technical Information of China (English)

    Jinming Duan; Xiaoting Cao; Cheng Chen; Dongrui Shi; Genmao Li; Dennis Mulcahy

    2012-01-01

    The effects of addition of calcium hydroxide on aluminum sulphate (or alum) coagulation for removal of natural organic matter (NOM) and its subsequent effect on the formation potentials of two major types of regulated disinfection byproducts (DBPs),haloacetic acids (HAAs) and trihalomethanes (THMs),have been examined.The results revealed several noteworthy phenomena.At the optimal coagulation pH (i.e.6),the coagulation behavior of NOM water solutions versus alum dose,showed large variation and a consequent great change in the formation potentials of the DBPs at certain coagulant doses.However,with addition of a relatively small amount of Ca(OH)2,although the zeta potential of coagulated flocs remained almost the same,NOM removal became more consistent with alum dose.Importantly,also the detrimental effect of charge reversal on NOM removal at the low coagulant dose disappeared.This resulted in a steady decrease in the formation potentials of DBPs as a function of the coagulant dose.Moreover,the addition of Ca(OH)2 broadened the pH range of alum coagulation and promoted further reduction of the formation potentials of the DBPs.The enhancement effects of Ca(OH)2 assisted alum coagulation are especially pronounced at pH 7 and 8.Finally,synchronous fluorescence spectra showed that the reduction in DBPs formation potential by Ca(OH)2-assisted alum coagulation was connected to an enhanced removal of small hydrophobic and hydrophilic HA molecules.Ca(OH)2-assistance of alum coagulation appeared to increase substantially the removal of the hydrophilic HA fraction responsible for HAAs formation,prompting further reduction of HAA formation potentials.

  4. EFECTO DEL PUNTO DE PRECLORACIÓN SOBRE LA FORMACIÓN DE TRIHALOMETANOS EN PROCESOS CONVENCIONALES DE POTABILIZACIÓN DE AGUA EFFECT OF THE PRECHLORINATION POINT ON THE TRIHALOMETHANES FORMATION IN CONVENTIONAL WATER TREATMENT PROCESS

    Directory of Open Access Journals (Sweden)

    Sindy Arjona-Rodríguez

    2012-06-01

    Full Text Available En las plantas de potabilización es muy común el uso de cloro como desinfectante para controlar el riesgo microbiológico que presentan las aguas superficiales; sin embargo, este producto puede reaccionar con la materia orgánica natural (MON favoreciendo la formación de subproductos orgánicos no deseados. En la planta Puerto Mallarino de la ciudad de Cali (Colombia, se evaluó a escala real el efecto del punto de precloración sobre la formación de trihalometanos (THM analizando dos secuencias de tratamiento: 1. Precloración-Coagulación-Clarificación y 2. Coagulación-Clarificación-Precloración. En promedio, los resultados evidenciaron menor formación de THM en la secuencia 2 (0,71 µg/L comparado con la secuencia 1 (12,88 µg/L, representando una reducción del 94,5%. En ambas condiciones se redujo el riesgo químico sin comprometer la calidad microbiológica del agua clarificada.On the drinking water treatment plants is normal the use of chlorine as disinfectant to control the microbiological risk that the superficial waters present; however, this product can be reacts with the organic natural matter (MON favoring the formation of undesirable organics by-products. In Puerto Mallarino drinking water treatment plant based in Cali (Colombia, the effect of prechlorination point over the generation of trihalomethanes (THM was evaluated at full scale. Two treatment sequences were considered: 1. Prechlorination-Coagulation-Clarification and 2. Coagulation-Clarification-Prechlorination. In average, results show a lower THM formation in the sequence 2 (0,71 µg/L if compared with the sequence 1 (12,88 µg/L, which represents a 94,5% reduction. In both conditions, chemical risk was reduced without compromising the microbiological quality of clarified water.

  5. Size and XAD fractionations of trihalomethane precursors from soils.

    Science.gov (United States)

    Chow, Alex T; Guo, Fengmao; Gao, Suduan; Breuer, Richard S

    2006-03-01

    Soil organic matter is an important source of allochthonous dissolved organic matter inputs to the Sacramento-San Joaquin Delta waterways, which is a drinking water source for 22 million people in California, USA. Knowledge of trihalomethane (THM) formation potential of soil-derived organic carbon is important for developing effective strategies for organic carbon removal in drinking water treatment. In this study, soil organic carbon was extracted with electrolytes (deionized H2O and Na- or Ca-based electrolytes) of electrical conductivity bracketing those found in Delta leaching and runoff conditions. The extracts were physically and chemically separated into different fractions: colloidal organic carbon (0.45-0.1 microm), fine colloidal organic carbon (0.1-0.025 microm), and dissolved organic carbon (DOC) (<0.025 microm); hydrophobic acid (HPOA), transphilic acid, and hydrophilic acid. Two representative Delta soils, Rindge Muck (a peat soil) and Scribner Clay Loam (a mineral soil) were examined. Results showed that less than 2% of soil organic carbon was electrolyte-extractable and heterogeneous organic fractions with distinct THM reactivity existed. Regardless of soil and electrolytes, DOC and HPOA fractions were dominant in terms of total concentration and THMFP. The amounts of extractable organic carbon and THMFP were dependent on the cation and to a lesser extent on electrical conductivity of electrolytes. Along with our previous study on temperature and moisture effects on DOC production, we propose a conceptual model to describe the impacts of agricultural practices on DOC production in the Delta. DOC is mainly produced in the surface peat soils during the summer and is immobilized by accumulated salt in the soils. DOC is leached from soils to drainage ditches and finally to the Delta channels during winter salt leaching practices.

  6. Potential presence of trihalomethanes in water intended for human consumption

    Directory of Open Access Journals (Sweden)

    C. Lasagna

    2011-01-01

    Full Text Available Since the 1970s it is well known that, though water for human consumption must generally be disinfected before being distributed along the network, the use of chemicals results in the formation of many different Disinfeection By-Products (DBPs. In the case of chlorine-based disinfectants, trihalomethanes (THMs are the most widely studied: the present work first compares some national and international regulations on this subject, then, in the experimental part, compares the results of a test carried out by disinfecting water of different origin collected in three different Italian regions with different amounts of chlorine. Samples were stored at ambient temperature for seven days, then the determination of THMs was carrried out by Purge and Trap extraction coupled with gas cromatography with Electron Capture Detection (ECD. The result obtained are finally compared and discussed.

  7. The impact of commercially treated oil and gas produced water discharges on bromide concentrations and modeled brominated trihalomethane disinfection byproducts at two downstream municipal drinking water plants in the upper Allegheny River, Pennsylvania, USA.

    Science.gov (United States)

    Landis, Matthew S; Kamal, Ali S; Kovalcik, Kasey D; Croghan, Carry; Norris, Gary A; Bergdale, Amy

    2016-01-15

    In 2010, a dramatic increase in the levels of total trihalomethane (THM) and the relative proportion of brominated species was observed in finished water at several Pennsylvania water utilities (PDW) using the Allegheny River as their raw water supply. An increase in bromide (Br(-)) concentrations in the Allegheny River was implicated to be the cause of the elevated water disinfection byproducts. This study focused on quantifying the contribution of Br(-) from a commercial wastewater treatment facility (CWTF) that solely treats wastes from oil and gas producers and discharges into the upper reaches of the Allegheny River, and impacts on two downstream PDWs. In 2012, automated daily integrated samples were collected on the Allegheny River at six sites during three seasonal two-week sampling campaigns to characterize Br(-) concentrations and river dispersion characteristics during periods of high and low river discharges. The CWTF discharges resulted in significant increases in Br(-) compared to upstream baseline values in PDW raw drinking water intakes during periods of low river discharge. During high river discharge, the assimilative dilution capacity of the river resulted in lower absolute halide concentrations, but significant elevations Br(-) concentrations were still observed at the nearest downstream PDW intake over baseline river levels. On days with active CWTF effluent discharge the magnitude of bromide impact increased by 39 ppb (53%) and 7 ppb (22%) for low and high river discharge campaigns, respectively. Despite a declining trend in Allegheny River Br(-) (2009-2014), significant impacts from CWTF and coal-fired power plant discharges to Br(-) concentrations during the low river discharge regime at downstream PDW intakes was observed, resulting in small modeled increases in total THM (3%), and estimated positive shifts (41-47%) to more toxic brominated THM analogs. The lack of available coincident measurements of THM, precursors, and physical parameters

  8. Formation and modeling of disinfection by-products in drinking water of six cities in China.

    Science.gov (United States)

    Ye, Bixiong; Wang, Wuyi; Yang, Linsheng; Wei, Jianrong; E, Xueli

    2011-05-01

    Water quality parameters including TOC, UV(254), pH, chlorine dosage, bromide concentration and disinfection by-products were measured in water samples from 41 water treatment plants of six selected cities in China. Chloroform, bromodichloromethane, dibromochloromethane, dichloroacetic acid and trichloroacetic acid were the major disinfection by-products in the drinking water of China. Bromoform and dibromoacetic acid were also detected in many water samples. Higher concentrations of trihalomethanes and haloacetic acids were measured in summer compared to winter. The geographical variations in DBPs showed that TTHM levels were higher in Zhengzhou and Tianjin than other selected cities. And the HAA5 levels were highest in Changsha and Tianjin. The modeling procedure that predicts disinfection by-products formation was studied and developed using artificial neural networks. The performance of the artificial neural networks model was excellent (r > 0.84).

  9. EFFICIENCY OF DOMESTIC REVERSE OSMOSIS IN REMOVAL OF TRIHALOMETHANES FROM DRINKING WATER

    Directory of Open Access Journals (Sweden)

    S. Mazloomi ، R. Nabizadeh ، S. Nasseri ، K. Naddafi ، S. Nazmara ، A. H. Mahvi

    2009-10-01

    Full Text Available The reaction of disinfectants with natural organic matters existing in water lead to the formation of Disinfection By-Products. Potentially hazardous and carcinogenic characteristics of trihalomethanes (THMs are recognized. Thus removal of THMs or its precursors are necessary for human health. The aim of this study was to study the efficiency of domestic reverse osmosis (RO in removal of trihalomethanes from drinking water. A pilot scale of RO system with Polyamide membrane as Spiral-Wound, Tape wrapping module was used. Feed solution was made by using of pure chloroform. The samples containing chloroform were analyzed using a gas chromatograph equipped with a flame ionization detector. By increasing the flow, the removal rate of chloroform decreased and with declining removal of EC, the removal of chloroform declined too. In this research, at the worst condition, the efficiency of the pilot scale reverse osmosis reached to 80 % removal of chloroform.

  10. O uso de cloro na desinfecção de águas, a formação de trihalometanos e os riscos potenciais à saúde pública Chlorine use in water disinfection, trihalomethane formation, and potential risks to public health

    Directory of Open Access Journals (Sweden)

    Sheila T. Meyer

    1994-03-01

    Full Text Available Antes do desenvolvimento da teoria dos microorganismos como causadores de doenças (1880, acreditava-se que estas eram transmitidas através de odores. A desinfecção, tanto da água de abastecimento como dos esgotos, surgiu como uma tentativa da eliminação desses odores. Existem muitos agentes desinfetantes, mas, em geral, o cloro é o principal produto utilizado na desinfecção de águas de abastecimento. A presença de compostos orgânicos em águas que sofrem o processo de cloração resulta na formação dos trihalometanos, compostos formados por um átomo de carbono, um de hidrogênio e três de halogênio (cloro, bromo, iôdo. Os trihalometanos são considerados compostos carcinogênicos e sua presença na água deve ser evitada. Levantamentos epidemiológicos relacionando a concentração dos trihalometanos com a morbidade e a mortalidade por câncer evidenciaram associações positivas em alguns casos de carcinomas. Entretanto, a substituição do cloro por outro desinfetante no tratamento da água pode trazer mais riscos do que benefícios, considerando-se que a diminuição da incidência de doenças transmissíveis pela água somente foi alcançada com a difusão do emprego da técnica de cloração.Before the development of the germ theory relating microorganisms with disease transmission (1880 people believed that diseases were transmitted by odours. Water and sewage disinfection emerged as a method for elimination of odours. There are many disinfecting agents, but chlorine is the main product used to disinfect water. Organic compounds present in water that is chlorinated can result in the formation of trihalomethanes. The latter are basically one atom of carbon, one of hydrogen, and three of a halogen (chlorine, bromine, or iodine. These are considered carcinogenic compounds and their presence in drinking water should therefore be avoided. Epidemiological research has shown an association between trihalomethane concentration

  11. TRIHALOMETHANES IN THE DRINKING WATER OF TEHRAN

    Directory of Open Access Journals (Sweden)

    F.Vaezi

    1992-06-01

    Full Text Available Natural sources of water contain some halogenated organic compounds after disinfection by chlorine. Trihalomethanes are one group of the chlorination by products that suspected of being carcinogenic inhuman unfortunately, these compounds are in finished water of all treatment plants that use chlorine as a disinfectant. In this study, the concentration of total THMS of water treated in the water treatment plant No.1 of Tehran had been measured by spectrophotometric method, along the month of June, 1371. Results of experiments have shown that organic contents of Tehran drinking water were not considerable in the period of survey. The mean concentration of TTHMS in water samples is estimated to be 28 micrograms per liter and none of the analyzed samples was considered polluted.

  12. Human health risk assessment from exposure to trihalomethanes in Canadian cities.

    Science.gov (United States)

    Chowdhury, Shakhawat; Hall, Kevin

    2010-07-01

    Lifetime exposure to trihalomethanes (THMs) through ingestion, inhalation and dermal contacts may pose risks to human health. Current approaches may under predict THMs exposure by using THMs in cold water during showering and bathing. Warming of chlorinated water during showering may increase THMs formation through reactions between organics and residual chlorine, which can increase human health risks. In this study, THMs concentrations in shower water were estimated using THMs rate increase model. Using cold water THMs, exposure through ingestion was estimated, while THMs exposure during showering was estimated using THMs in warm water. Human health cancer risks and additional expenses for 20 most populated Canadian cities from exposure to THMs were estimated. Inhalation and dermal contact during showering contributed 30% to 50% of total cancer risks, while risks from inhalation and dermal contacts were comparable for all cities. Overall cancer risks were estimated between 7.2 x 10(-6) and 6.4 x 10(-5) for these cities. Cancer incidents were estimated highest for Montreal (94/year) followed by Toronto (53/year), which may require additional medical expenses of 18.8 and 10.7 million dollars/year for Montreal and Toronto respectively. Cancer risks from exposure to THMs can be controlled by reducing THMs in water supply and varying shower stall volume, shower duration and air exchange rate in shower stall. Copyright 2010 Elsevier Ltd. All rights reserved.

  13. Characteristics of Trihalomethanes in Water Distribution System

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ming; ZHANG Jie; ZHANG Xin-yu; ZHENG Shuang-ying; LI Xin

    2008-01-01

    To investigate the characteristics of disinfection by-products (DBPs) in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes (THMs) formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part (83%89%) to the index for additive toxicity (ATI) and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs (TTHMs), especially during the summer (rainy season). This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TTHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.

  14. Risk from exposure to trihalomethanes during shower: probabilistic assessment and control.

    Science.gov (United States)

    Chowdhury, Shakhawat; Champagne, Pascale

    2009-02-15

    Exposure to trihalomethanes (THMs) through inhalation and dermal contact during showering and bathing may pose risks to human health. During showering and bathing, warm water (35 degrees C-45 degrees C) is generally used. Warming of chlorinated supply water may increase THMs formation through enhanced reactions between organics and residual chlorine. Exposure assessment using THMs concentrations in cold water may under-predict the possible risks to human health. In this study, THMs concentrations in warm water were estimated by developing a THMs formation rate model. Using THMs in warm water, cancer and non-cancer risks to human health were predicted for three major cities in Ontario (Canada). The parameters for risk assessments were characterized by statistical distributions. The total cancer risks from exposure to THMs during showering were predicted to be 7.6x10(-6), 6.3x10(-6) and 4.3x10(-6) for Ottawa, Hamilton and Toronto respectively. The cancer risks exceedance probabilities were estimated to be highest in Ottawa at different risk levels. The risks through inhalation exposure were found to be comparable (2.1x10(-6)-3.7x10(-6)) to those of the dermal contact (2.2x10(-6)-3.9x10(-6)) for the cities. This study predicted 36 cancer incidents from exposure to THMs during showering for these three cities, while Toronto contributed the highest number of possible cancer incidents (22), followed by Ottawa (10) and Hamilton (4). The sensitivity analyses showed that health risks could be controlled by varying shower stall volume and/or shower duration following the power law relationship.

  15. Coevolutionary modeling in network formation

    KAUST Repository

    Al-Shyoukh, Ibrahim

    2014-12-03

    Network coevolution, the process of network topology evolution in feedback with dynamical processes over the network nodes, is a common feature of many engineered and natural networks. In such settings, the change in network topology occurs at a comparable time scale to nodal dynamics. Coevolutionary modeling offers the possibility to better understand how and why network structures emerge. For example, social networks can exhibit a variety of structures, ranging from almost uniform to scale-free degree distributions. While current models of network formation can reproduce these structures, coevolutionary modeling can offer a better understanding of the underlying dynamics. This paper presents an overview of recent work on coevolutionary models of network formation, with an emphasis on the following three settings: (i) dynamic flow of benefits and costs, (ii) transient link establishment costs, and (iii) latent preferential attachment.

  16. Cosmological models of galaxy formation

    Science.gov (United States)

    Menci, N.

    I review the present status of galaxy formation models within a cosmological framework. I focus on semi-analytic models based on the Cold Dark Matter scenario, discussing the role of the different physical process involving dark matter and baryons in determining the observed statistical properties of galaxies and their dependence on cosmic time and on environment evolution. I will highlight some present problems and briefly present the main effects of assuming a Warm Dark Matter scenario.

  17. Climatic, Geographic and Operational Determinants of Trihalomethanes (THMs) in Drinking Water Systems

    Science.gov (United States)

    Valdivia-Garcia, Maria; Weir, Paul; Frogbrook, Zoe; Graham, David W.; Werner, David

    2016-01-01

    Trihalomethanes (THMs) are conditionally carcinogenic compounds formed during chlorine disinfection in water treatment processes around the world. THMs occur especially when source waters are subject to marine influences, high and-or regular precipitation, and elevated levels of organic matter. THMs formation is then rooted in geographic, operational and climatic factors, the relative importance of which can only be derived from large datasets and may change in the future. Ninety three full-scale Scottish water treatment plants (WTPs) were assessed from Jan 2011 to Jan 2013 to identify factors that promote THMs formation. Correlation analysis showed that ambient temperature was the primary THMs formation predictor in potable water (r2 = 0.66, p climatic factors are key to THMs formation. If ambient temperatures increase, THMs control will become more challenging, substantiating concerns about the impact of global warming on water quality. PMID:27762332

  18. Climatic, Geographic and Operational Determinants of Trihalomethanes (THMs) in Drinking Water Systems

    Science.gov (United States)

    Valdivia-Garcia, Maria; Weir, Paul; Frogbrook, Zoe; Graham, David W.; Werner, David

    2016-10-01

    Trihalomethanes (THMs) are conditionally carcinogenic compounds formed during chlorine disinfection in water treatment processes around the world. THMs occur especially when source waters are subject to marine influences, high and-or regular precipitation, and elevated levels of organic matter. THMs formation is then rooted in geographic, operational and climatic factors, the relative importance of which can only be derived from large datasets and may change in the future. Ninety three full-scale Scottish water treatment plants (WTPs) were assessed from Jan 2011 to Jan 2013 to identify factors that promote THMs formation. Correlation analysis showed that ambient temperature was the primary THMs formation predictor in potable water (r2 = 0.66, p real-world dataset confirms both geographic and climatic factors are key to THMs formation. If ambient temperatures increase, THMs control will become more challenging, substantiating concerns about the impact of global warming on water quality.

  19. Occurrence and simulation of trihalomethanes in swimming pool water: A simple prediction method based on DOC and mass balance.

    Science.gov (United States)

    Peng, Di; Saravia, Florencia; Abbt-Braun, Gudrun; Horn, Harald

    2016-01-01

    Trihalomethanes (THM) are the most typical disinfection by-products (DBPs) found in public swimming pool water. DBPs are produced when organic and inorganic matter in water reacts with chemical disinfectants. The irregular contribution of substances from pool visitors and long contact time with disinfectant make the forecast of THM in pool water a challenge. In this work occurrence of THM in a public indoor swimming pool was investigated and correlated with the dissolved organic carbon (DOC). Daily sampling of pool water for 26 days showed a positive correlation between DOC and THM with a time delay of about two days, while THM and DOC didn't directly correlate with the number of visitors. Based on the results and mass-balance in the pool water, a simple simulation model for estimating THM concentration in indoor swimming pool water was proposed. Formation of THM from DOC, volatilization into air and elimination by pool water treatment were included in the simulation. Formation ratio of THM gained from laboratory analysis using native pool water and information from field study in an indoor swimming pool reduced the uncertainty of the simulation. The simulation was validated by measurements in the swimming pool for 50 days. The simulated results were in good compliance with measured results. This work provides a useful and simple method for predicting THM concentration and its accumulation trend for long term in indoor swimming pool water.

  20. Technical Report for Water Circulation Pumping System for Trihalomethanes (THMs)

    Energy Technology Data Exchange (ETDEWEB)

    Bellah, W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-06-08

    The TSWWS was added as an active source of supply to the permit (No. 03-10-13P-003) in 2010, but has never been used due to the potential for formation of trihalomethanes (THMs) in the distribution system. THMs are formed as a by-product when chlorine is used to disinfect water for drinking. THMs are a group of chemicals generally referred to as disinfection by-products (DBPs). THMs result from the reaction of chlorine with organic matter that is present in the water. Some of the THMs are volatile and may easily vaporize into the air. This fact forms the basis of the design of the system discussed in this technical report. In addition, the design is based on the results of a study that has shown success using aeration as a means to reduce TTHMs to within allowable concentration levels with turn-over times as long as ten days. The Primary Drinking Water Standards of Regulated Contaminants Maximum Contaminant Level (MCL) for TTHMs is 80 parts per billion (ppb). No other changes to the existing drinking water distribution system and chlorination operations are anticipated before switching to the TSWWS as the primary drinking water source. The two groundwater wells (Wells 20 and 18) which are currently the primary and backup water sources for the system would be maintained for use as backup supply. In the future, one of the wells may be removed from the system. A permit amendment would be filed at that time if this modification was deemed appropriate.

  1. Analysis of Trihalomethanes in Soft Drinks: An Instrumental Analysis Experiment.

    Science.gov (United States)

    Graham, Richard C.; Robertson, John K.

    1988-01-01

    Describes an experimental procedure for determining trihalomethanes (THMs) in liquids by gas chromatography. Provides recommendations for reactants and supplies to obtain acceptable results. Discusses the analysis of water from various sources: pools, lakes, and drinking water; compares these to three cola drinks. (ML)

  2. Analysis of Trihalomethanes in Soft Drinks: An Instrumental Analysis Experiment.

    Science.gov (United States)

    Graham, Richard C.; Robertson, John K.

    1988-01-01

    Describes an experimental procedure for determining trihalomethanes (THMs) in liquids by gas chromatography. Provides recommendations for reactants and supplies to obtain acceptable results. Discusses the analysis of water from various sources: pools, lakes, and drinking water; compares these to three cola drinks. (ML)

  3. Trihalomethane, Dihaloacetonitrile, and Total N-nitrosamine Precursor Adsorption by Carbon Nanotubes: The Importance of Surface Oxides and Pore Volume

    Science.gov (United States)

    Needham, Erin Michelle

    As drinking water sources become increasingly impaired, enhanced removal of natural organic matter (NOM) may be required to curb formation of disinfection byproducts (DBPs) upon chlor(am)ination. While carbon nanotubes (CNTs) can adsorb NOM, their properties for DBP precursor adsorption have not been elucidated. Nine types of CNTs were assessed for trihalomethane (THM), dihaloacetonitrile (DHAN), and total N-nitrosamine (TONO) precursor adsorption. Batch isotherm experiments were completed with lake water and, to simulate an impaired condition, effluent from a wastewater treatment plant (WWTP). Adsorption varied with CNT type and dose, with TONO precursors having the highest percent removals from WWTP effluent (up to 97%). Physicochemical properties of CNTs were characterized by gas adsorption isotherms and x-ray photoelectron spectroscopy and numerical models were developed to identify CNT properties driving DBP precursor adsorption. The models fits were strong (R2 > 0.92) and indicated removal of the three precursor types increased with percent carboxyl groups (p adsorption of DBP precursors and demonstrate the potential of CNTs for TONO precursor removal.

  4. Removal of trihalomethane precursors in industrial wastewater; Sangyo haisui ni fukumareru trihalomethane zenku busshitsu no jokyo

    Energy Technology Data Exchange (ETDEWEB)

    Machida, K.; Tsuda, S. [Ebara Corp., Tokyo (Japan); Kiriyama, K.; Hidaka, T. [Ebara Research Co. Ltd., Kanagawa (Japan)

    1998-01-20

    As part of a study on `a technology to treat wastewater from tap water sources` commissioned from NEDO, operation research was carried out on a demonstration plant (50 m {sup 3}/d) built with an intention to remove trihalomethane precursors (abbreviated to THMFP) contained in wasterwater from a paper mill. As a result, the following findings were obtained: an activated sludge treatment can remove THMFP at a removal rate of 10%, succeeding precipitation treatment 37%, and a further activated charcoal treatment or a membrane (nano-filtration (NF)) treatment 84% to 93%, resulting in the remaining THMFP of 0.3 mg per liter or less. CHCl3 precursor materials can be removed well by any treatment process, but bromine-coordinated THMFP is removed well by the NF treatment. Because THMFP quantification of wastewater with high total organic carbon (TOC) concentration is largely affected by dilution rate, discussions were given on the dilution rate, whereas it was found adequate that test samples be diluted so that the TOC will be 1 to 3 mg per liter. 3 refs., 7 figs., 8 tabs.

  5. On the modelling of river delta formation

    NARCIS (Netherlands)

    Geleynse, N.

    2013-01-01

    This thesis presents approaches to the modelling of river delta formation. In particular, it provides results of numerical stratigraphic-morphodynamic modelling of river delta formation under various environmental forcings.

  6. Seasonal and spatial evolution of trihalomethanes in a drinking water distribution system according to the treatment process.

    Science.gov (United States)

    Domínguez-Tello, A; Arias-Borrego, A; García-Barrera, Tamara; Gómez-Ariza, J L

    2015-11-01

    This paper comparatively shows the influence of four water treatment processes on the formation of trihalomethanes (THMs) in a water distribution system. The study was performed from February 2005 to January 2012 with analytical data of 600 samples taken in Aljaraque water treatment plant (WTP) and 16 locations along the water distribution system (WDS) in the region of Andévalo and the coast of Huelva (southwest Spain), a region with significant seasonal and population changes. The comparison of results in the four different processes studied indicated a clear link of the treatment process with the formation of THM along the WDS. The most effective treatment process is preozonation and activated carbon filtration (P3), which is also the most stable under summer temperatures. Experiments also show low levels of THMs with the conventional process of preoxidation with potassium permanganate (P4), delaying the chlorination to the end of the WTP; however, this simple and economical treatment process is less effective and less stable than P3. In this study, strong seasonal variations were obtained (increase of THM from winter to summer of 1.17 to 1.85 times) and a strong spatial variation (1.1 to 1.7 times from WTP to end points of WDS) which largely depends on the treatment process applied. There was also a strong correlation between THM levels and water temperature, contact time and pH. On the other hand, it was found that THM formation is not proportional to the applied chlorine dose in the treatment process, but there is a direct relationship with the accumulated dose of chlorine. Finally, predictive models based on multiple linear regressions are proposed for each treatment process.

  7. Disinfection by-product formation following chlorination of drinking water: artificial neural network models and changes in speciation with treatment.

    Science.gov (United States)

    Kulkarni, Pranav; Chellam, Shankararaman

    2010-09-01

    Artificial neural network (ANN) models were developed to predict disinfection by-product (DBP) formation during municipal drinking water treatment using the Information Collection Rule Treatment Studies database complied by the United States Environmental Protection Agency. The formation of trihalomethanes (THMs), haloacetic acids (HAAs), and total organic halide (TOX) upon chlorination of untreated water, and after conventional treatment, granular activated carbon treatment, and nanofiltration were quantified using ANNs. Highly accurate predictions of DBP concentrations were possible using physically meaningful water quality parameters as ANN inputs including dissolved organic carbon (DOC) concentration, ultraviolet absorbance at 254nm and one cm path length (UV(254)), bromide ion concentration (Br(-)), chlorine dose, chlorination pH, contact time, and reaction temperature. This highlights the ability of ANNs to closely capture the highly complex and non-linear relationships underlying DBP formation. Accurate simulations suggest the potential use of ANNs for process control and optimization, comparison of treatment alternatives for DBP control prior to piloting, and even to reduce the number of experiments to evaluate water quality variations when operating conditions are changed. Changes in THM and HAA speciation and bromine substitution patterns following treatment are also discussed. Copyright 2010 Elsevier B.V. All rights reserved.

  8. CONCENTRATION OF TRIHALOMETHANES (THM AND PRECURSORS IN DRINKING WATER WITHIN DISTRIBUTION NETWORKS

    Directory of Open Access Journals (Sweden)

    CORNELIA DIANA ROMAN

    2012-03-01

    Full Text Available Concentration of trihalomethanes (THM and precursors in drinking water within distribution networks. Water chlorination is the disinfection method most widely used, having however the disadvantage of producing trihalomethanes (THM as secondary compounds, which are included in the list of priority hazardous substances in water. THM formation is influenced by the raw water composition and chlorine from the disinfection process. This paper intends to highlight the individual values of the chemical compounds precursors of THM in the water network in order to correlate them with the evolution of THM concentration. The cities of Targu Mures and Zalau were chosen as the study area having surface waters with different degrees of contamination as the water source. Pre-treatment with potassium permanganate is used at the water treatment plant in Targu Mures, while pre-chlorination is used at the water treatment plant in Zalau. Water sampling was performed weekly between March-May, 2011 in three sampling points of each city, maintained during the period of study. Total THM and their compounds as well as THM precursors (oxidability, ammonium content, nitrites and nitrates were measured. The water supplied in the distribution network corresponded integrally to the quality standards in terms of the analyzed indicators, including THM concentrations. The higher average THM concentrations in Zalau (52.01±14 μg/L compared to Targu Mures (36.43±9.14 μg/L were expected as a result of precursors concentration. In terms of THM compounds, they had similar proportions in the two localities, chloroform being clearly predominant, followed by dichlorobromoform and dibromochloroform, while bromoform was not identified. Statistical data analysis showed that the presence of THM precursors is correlated with the THM levels but not sufficient for their generation, even if they can be considered in general the basis of a valid prediction.

  9. H$_2$-based star formation laws in galaxy formation models

    CERN Document Server

    Xie, Lizhi; Hirschmann, Michaela; Fontanot, Fabio; Zoldan, Anna

    2016-01-01

    We update our recently published model for GAlaxy Evolution and Assembly (GAEA), to include a self-consistent treatment of the partition of cold gas in atomic and molecular hydrogen. Our model provides significant improvements with respect to previous ones used for similar studies. In particular, GAEA (i) includes a sophisticated chemical enrichment scheme accounting for non-instantaneous recycling of gas, metals, and energy; (ii) reproduces the measured evolution of the galaxy stellar mass function; (iii) reproduces the observed correlation between galaxy stellar mass and gas metallicity at different redshifts. These are important prerequisites for models considering a metallicity dependent efficiency of molecular gas formation. We also update our model for disk sizes and show that model predictions are in nice agreement with observational estimates for the gas, stellar and star forming disks at different cosmic epochs. We analyse the influence of different star formation laws including empirical relations b...

  10. Alveolar breath sampling and analysis to assess trihalomethane exposures during competitive swimming training.

    Science.gov (United States)

    Lindstrom, A B; Pleil, J D; Berkoff, D C

    1997-06-01

    Alveolar breath sampling was used to assess trihalomethane (THM) exposures encountered by collegiate swimmers during a typical 2-hr training period in an indoor natatorium. The breath samples were collected at regular intervals before, during, and for 3 hr after a moderately intense training workout. Integrated and grab whole-air samples were collected during the training period to help determine inhalation exposures, and pool water samples were collected to help assess dermal exposures. Resulting breath samples collected during the workout demonstrated a rapid uptake of two THMs (chloroform and bromodichloromethane), with chloroform concentrations exceeding the natatorium air levels within 8 min after the exposure began. Chloroform levels continued to rise steeply until they were more than two times the indoor levels, providing evidence that the dermal route of exposure was relatively rapid and ultimately more important than the inhalation route in this training scenario. Chloroform elimination after the exposure period was fitted to a three compartment model that allowed estimation of compartmental half-lives, resulting minimum bloodborne dose, and an approximation of the duration of elevated body burdens. We estimated the dermal exposure route to account for 80% of the blood chloroform concentration and the transdermal diffusion efficiency from the water to the blood to in excess of 2%. Bromodichloromethane elimination was fitted to a two compartment model which provided evidence of a small, but measurable, body burden of this THM resulting from vigorous swim training. These results suggest that trihalomethane exposures for competitive swimmers under prolonged, high-effort training are common and possibly higher than was previously thought and that the dermal exposure route is dominant. The exposures and potential risks associated with this common recreational activity should be more thoroughly investigated.

  11. Global Models of Planet Formation and Evolution

    CERN Document Server

    Mordasini, C; Dittkrist, K -M; Jin, S; Alibert, Y

    2014-01-01

    Despite the increase in observational data on exoplanets, the processes that lead to the formation of planets are still not well understood. But thanks to the high number of known exoplanets, it is now possible to look at them as a population that puts statistical constraints on theoretical models. A method that uses these constraints is planetary population synthesis. Its key element is a global model of planet formation and evolution that directly predicts observable planetary properties based on properties of the natal protoplanetary disk. To do so, global models build on many specialized models that address one specific physical process. We thoroughly review the physics of the sub-models included in global formation models. The sub-models can be classified as models describing the protoplanetary disk (gas and solids), the (proto)planet (solid core, gaseous envelope, and atmosphere), and finally the interactions (migration and N-body interaction). We compare the approaches in different global models and id...

  12. Secondary formation of disinfection by-products by UV treatment of swimming pool water

    Energy Technology Data Exchange (ETDEWEB)

    Spiliotopoulou, Aikaterini [Water ApS, Farum Gydevej 64, 3520 Farum (Denmark); Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Kongens Lyngby (Denmark); Hansen, Kamilla M.S., E-mail: kmsh@env.dtu.dk [Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Kongens Lyngby (Denmark); Andersen, Henrik R. [Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Building 113, 2800 Kongens Lyngby (Denmark)

    2015-07-01

    Formation of disinfection by-products (DBPs) during experimental UV treatment of pool water has previously been reported with little concurrence between laboratory studies, field studies and research groups. In the current study, changes in concentration of seven out of eleven investigated volatile DBPs were observed in experiments using medium pressure UV treatment, with and without chlorine and after post-UV chlorination. Results showed that post-UV chlorine consumption increased, dose-dependently, with UV treatment dose. A clear absence of trihalomethane formation by UV and UV with chlorine was observed, while small yet statistically significant increases in dichloroacetonitrile and dichloropropanone concentrations were detected. Results indicate that post-UV chlorination clearly induced secondary formation of several DBPs. However, the formation of total trihalomethanes was no greater than what could be replicated by performing the DBP formation assay with higher chlorine concentrations to simulate extended chlorination. Post-UV chlorination of water from a swimming pool that continuously uses UV treatment to control combined chlorine could not induce secondary formation for most DBPs. Concurrence for induction of trihalomethanes was identified between post-UV chlorination treatments and simulated extended chlorination time treatment. Trihalomethanes could not be induced by UV treatment of water from a continuously UV treated pool. This indicates that literature reports of experimentally induced trihalomethane formation by UV may be a result of kinetic increase in formation by UV. However, this does not imply that higher trihalomethane concentrations would occur in pools that apply continuous UV treatment. The bromine fraction of halogens in formed trihalomethanes increased with UV dose. This indicates that UV removes bromine atoms from larger molecules that participate in trihalomethane production during post-UV chlorination. Additionally, no significant

  13. Mechanisms and Geochemical Models of Core Formation

    CERN Document Server

    Rubie, David C

    2015-01-01

    The formation of the Earth's core is a consequence of planetary accretion and processes in the Earth's interior. The mechanical process of planetary differentiation is likely to occur in large, if not global, magma oceans created by the collisions of planetary embryos. Metal-silicate segregation in magma oceans occurs rapidly and efficiently unlike grain scale percolation according to laboratory experiments and calculations. Geochemical models of the core formation process as planetary accretion proceeds are becoming increasingly realistic. Single stage and continuous core formation models have evolved into multi-stage models that are couple to the output of dynamical models of the giant impact phase of planet formation. The models that are most successful in matching the chemical composition of the Earth's mantle, based on experimentally-derived element partition coefficients, show that the temperature and pressure of metal-silicate equilibration must increase as a function of time and mass accreted and so m...

  14. Stochastic Models of Molecule Formation on Dust

    Science.gov (United States)

    Charnley, Steven; Wirstroem, Eva

    2011-01-01

    We will present new theoretical models for the formation of molecules on dust. The growth of ice mantles and their layered structure is accounted for and compared directly to observations through simulation of the expected ice absorption spectra

  15. Observational Tests of Planet Formation Models

    CERN Document Server

    Sozzetti, A; Latham, D W; Carney, B W; Laird, J B; Stefanik, R P; Boss, A P; Charbonneau, D; O'Donovan, F T; Holman, M J; Winn, J N

    2007-01-01

    We summarize the results of two experiments to address important issues related to the correlation between planet frequencies and properties and the metallicity of the hosts. Our results can usefully inform formation, structural, and evolutionary models of gas giant planets.

  16. Cellular Automaton Modeling of Pattern Formation

    NARCIS (Netherlands)

    Boerlijst, M.C.

    2006-01-01

    Book review Andreas Deutsch and Sabine Dormann, Cellular Automaton Modeling of Biological Pattern Formation, Characterization, Applications, and Analysis, Birkhäuser (2005) ISBN 0-8176-4281-1 331pp..

  17. Kinetic exchange models for social opinion formation

    CERN Document Server

    Lallouache, Mehdi; Chakrabarti, Bikas K

    2010-01-01

    We propose a minimal model for the collective dynamics of opinion formation in the society, by modifying kinetic exchange dynamics studied in the context of income, money or wealth distributions in a society.

  18. Testing Models for Structure Formation

    CERN Document Server

    Kaiser, N

    1993-01-01

    I review a number of tests of theories for structure formation. Large-scale flows and IRAS galaxies indicate a high density parameter $\\Omega \\simeq 1$, in accord with inflationary predictions, but it is not clear how this meshes with the uniformly low values obtained from virial analysis on scales $\\sim$ 1Mpc. Gravitational distortion of faint galaxies behind clusters allows one to construct maps of the mass surface density, and this should shed some light on the large vs small-scale $\\Omega$ discrepancy. Power spectrum analysis reveals too red a spectrum (compared to standard CDM) on scales $\\lambda \\sim 10-100$ $h^{-1}$Mpc, but the gaussian fluctuation hypothesis appears to be in good shape. These results suggest that the problem for CDM lies not in the very early universe --- the inflationary predictions of $\\Omega = 1$ and gaussianity both seem to be OK; furthermore, the COBE result severely restricts modifications such as tilting the primordial spectrum --- but in the assumed matter content. The power s...

  19. Ammonia-Oxidizing Bacteria in Biofilters Removing Trihalomethanes Are Related to Nitrosomonas oligotropha

    Science.gov (United States)

    Nitrifying biofilters degrading the four regulated trihalomethanes (THMs) trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) -were analyzed for the presence and activity of ammonia-oxidizing bacteria (AOB). Biofilter perfor...

  20. Ammonia-Oxidizing Bacteria in Biofilters Removing Trihalomethanes Are Related to Nitrosomonas oligotropha

    Science.gov (United States)

    Nitrifying biofilters degrading the four regulated trihalomethanes (THMs) trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) -were analyzed for the presence and activity of ammonia-oxidizing bacteria (AOB). Biofilter perfor...

  1. Pyrosequencing Analysis of Bench-Scale Nitrifying BiofiltersRemoving Trihalomethanes

    Science.gov (United States)

    The bacterial biofilm communities in four nitrifying biofilters degrading regulated drinking water trihalomethanes were characterized by 454 pyrosequencing. The three most abundant phylotypes based on total diversity were Nitrosomonas (70%), Nitrobacter (14%), and Chitinophagace...

  2. INFLUENCE OF EXPOSURE ASSESSMENT METHOD IN AN EPIDEMIOLOGIC STUDY OF TRIHALOMETHANE EXPOSURE AND SPONTANEOUS ABORTION

    Science.gov (United States)

    Trihalomethanes are common contaminants of chlorinated drinking water. Studies of their health effects have been hampered by exposure misclassification, due in part to limitations inherent in using utility sampling records. We used two exposure assessment methods, one based on ut...

  3. INFLUENCE OF EXPOSURE ASSESSMENT METHOD IN AN EPIDEMIOLOGIC STUDY OF TRIHALOMETHANE EXPOSURE AND SPONTANEOUS ABORTION

    Science.gov (United States)

    Trihalomethanes are common contaminants of chlorinated drinking water. Studies of their health effects have been hampered by exposure misclassification, due in part to limitations inherent in using utility sampling records. We used two exposure assessment methods, one based on ut...

  4. Pattern formation and functionality in swarm models

    CERN Document Server

    Rauch, E M; Chialvo, D R; Rauch, Erik M; Millonas, Mark M; Chialvo, Dante R

    1995-01-01

    We explore a simplified class of models we call swarms, which are inspired by the collective behavior of social insects. We perform a mean-field stability analysis and perform numerical simulations of the model. Several interesting types of behavior emerge in the vicinity of a second-order phase transition in the model, including the formation of stable lines of traffic flow, and memory reconstitution and bootstrapping. In addition to providing an understanding of certain classes of biological behavior, these models bear a generic resemblance to a number of pattern formation processes in the physical sciences.

  5. Adsorption of trihalomethanes from water with carbon nanotubes.

    Science.gov (United States)

    Lu, Chungsying; Chung, Yao-Lei; Chang, Kuan-Foo

    2005-03-01

    Commercial carbon nanotubes (CNTs) were purified by acid solution and were employed as adsorbents to study adsorption of trihalomethanes (THMs) from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after acid treatment which made CNTs become more hydrophilic and suitable for adsorption of low molecular weight and relatively polar THM molecules. The adsorption of THMs onto CNTs fluctuates very little in the pH range 3-7, but decreases with pH value as pH exceeds 7. A comparative study between CNTs and powdered activated carbon (PAC) for adsorption of THMs from water was also conducted. The short time needed to reach equilibrium as well as the high adsorption capacity of CHCl3, which accounts for a significant portion of THMs in the chlorinated drinking water, suggests that CNTs possess highly potential applications for THMs removal from water.

  6. Disinfection by-product formation of UV treated swimming pool water

    DEFF Research Database (Denmark)

    Spiliotopoulou, Aikaterini; Hansen, Kamilla Marie Speht; Andersen, Henrik Rasmus

    2015-01-01

    -UV chlorine consumption increased, dose-dependently, with UV treatment dose. A clear absence of trihalomethane formation by UV and UV with chlorine was observed. The post-UV chlorination clearly induced formation of DBPs; however, for the total trihalomethanes (TTHM), the inductions were not more than what...... indicates that UV breaks bromine atoms from larger molecules participating in trihalomethane production during the post-UV chlorination. No significant effect on DBP formation was observed by the photo-inducible radical forming molecules NO3- and H2O2, which may either occur occasionally in high...

  7. Pattern Formation in a Bacterial Colony Model

    Directory of Open Access Journals (Sweden)

    Xinze Lian

    2014-01-01

    Full Text Available We investigate the spatiotemporal dynamics of a bacterial colony model. Based on the stability analysis, we derive the conditions for Hopf and Turing bifurcations. Furthermore, we present novel numerical evidence of time evolution of patterns controlled by parameters in the model and find that the model dynamics exhibit a diffusion controlled formation growth to spots, holes and stripes pattern replication, which show that the bacterial colony model is useful in revealing the spatial predation dynamics in the real world.

  8. [Risk Assessment of Trihalomethane Production Using the Beijiang River and the Pearl River, Guangzhou as Drinking Water Sources].

    Science.gov (United States)

    Zhong, Hui-zhou; Wei, Chao-hai

    2015-04-01

    In order to investigate the risk of trihalomethane formation potential (THMFP) in finished waters as drinking water sources, 70 samples, 114 samples, and 70 samples were collected in November 2013, April 2014 and July 2014, respectively from different locations in the Beijiang River and the Pearl River. After filtration by 0.45 μm filter membrane, a total of 254 samples were chlorinated using Uniform Formation Condition (UFC) method for determining their THM Formation Potential (THMFP). The cancer risk and non-cancer risk of THMs were estimated using USEPA risk assessment model while dominant factors for total risk potential were estimated using sensitivity analysis. Among four THM species, chloroform( CF) was the highest ranging from 101.92-2 590.85 μg x L(-1), followed by bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (BF). Chloroform, the major THMs speciation, accounted for 96.17% of total THMs. Non-cancer and cancer risk from ingesting THMs was estimated. The result indicated that non-cancer risk of THMs level ranged from 2.03 x 10(-7) to 1.00 x 10(-5) and was not more than 1.0 x 10(-5), the minimum or negligible non-cancer risk level defined by the USEPA. The average cancer risk of THMs was 2.91 x 10(-4) for male and 3.30 x 10(-4) for female in the two rivers, respectively, exceeding the minimum or negligible risk level defined by the USEPA (1. 0 x 10 ~6). The difference of cancer risk between the two rivers was that BDCM ranging from 2.50 x 10(-5) to 6.37 x 10(-4) was approximately twice that of CF in Beijing River. BDCM played an important role in the total risk in the Beijiang River while CF played an important role in the total risk in the Pearl River, Guangzhou. Sensitivity analysis showed that CF played an important role in the estimation of total risk potential, and that the direct utilization of water sources from Beijiang River and the Pearl River Guangzhou is dangerous, thus pretreatment is necessary before chlorination.

  9. Modelling Galaxy Formation at high z

    OpenAIRE

    1997-01-01

    I describe a semi-analytical model for the formation and evolution of galaxies in hierarchical clustering models, and its predictions for the properties of the galaxy population at high z. The predictions are found to agree well with the observed properties of the Lyman break galaxies found at z sim 3 by Steidel et al. The models predict that the star formation rate per comoving volume should have peaked at z sim 1-2, which also agrees well with recent observational data.

  10. A Model of Client Impression Formation.

    Science.gov (United States)

    Bodden, Jack L.; Winer, Jane L.

    1978-01-01

    The model describes the clients' impression-formation process, describes changes in client impressions as therapy progresses, and suggests the relevance of client impressions for therapy outcome. An attempt at empirical validation by using a clinical population lent some support to certain aspects of the proposed model. (Author)

  11. Secondary formation of disinfection by-products by UV treatment of swimming pool water

    DEFF Research Database (Denmark)

    Spiliotopoulou, Aikaterini; Hansen, Kamilla Marie Speht; Andersen, Henrik Rasmus

    2015-01-01

    was observed, while small yet statistically significant increases in dichloroacetonitrile and dichloropropanone concentrations were detected. Results indicate post-UV chlorination clearly induced secondary formation of several DBPs. However, formation of total trihalomethanes was no greater than what could...... that UV removes bromine atoms from larger molecules that participate in trihalomethane production during post-UV chlorination. Additionally, no significant effect on DBP formation was observed due to photoinducible radical forming molecules NO3 - (potentially present in high concentrations in pool water...

  12. Modeling Start Curves of Bainite Formation

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.

    2009-01-01

    It is demonstrated that calculations with a physically based model give an accurate description of the start curve of bainite formation in a wide range of steels. The temperature dependence of the overall kinetics, which determines the characteristic C shape of the start curve, is controlled by both

  13. Determination of trihalomethanes in water samples: A review

    Energy Technology Data Exchange (ETDEWEB)

    Perez Pavon, Jose Luis [Departamento de Quimica Analitica, Nutricion y Bromatologia, Facultad de Ciencias Quimicas, Universidad de Salamanca, 37008 Salamanca (Spain)], E-mail: jlpp@usal.es; Herrero Martin, Sara; Garcia Pinto, Carmelo; Moreno Cordero, Bernardo [Departamento de Quimica Analitica, Nutricion y Bromatologia, Facultad de Ciencias Quimicas, Universidad de Salamanca, 37008 Salamanca (Spain)

    2008-11-23

    This article reviews the most recent literature addressing the analytical methods applied for trihalomethanes (THMs) determination in water samples. This analysis is usually performed with gas chromatography (GC) combined with a preconcentration step. The detectors most widely used in this type of analyses are mass spectrometers (MS) and electron capture detectors (ECD). Here, we review the analytical characteristics, the time required for analysis, and the simplicity of the optimised methods. The main difference between these methods lies in the sample pretreatment step; therefore, special emphasis is placed on this aspect. The techniques covered are direct aqueous injection (DAI), liquid-liquid extraction (LLE), headspace (HS), and membrane-based techniques. We also review the main chromatographic columns employed and consider novel aspects of chromatographic analysis, such as the use of fast gas chromatography (FGC). Concerning the detection step, besides the common techniques, the use of uncommon detectors such as fluorescence detector, pulsed discharge photoionization detector (PDPID), dry electrolytic conductivity detector (DELCD), atomic emission detector (AED) and inductively coupled plasma-mass spectrometry (ICP-MS) for this type of analysis is described.

  14. Secondary formation of disinfection by-products by UV treatment of swimming pool water.

    Science.gov (United States)

    Spiliotopoulou, Aikaterini; Hansen, Kamilla M S; Andersen, Henrik R

    2015-07-01

    Formation of disinfection by-products (DBPs) during experimental UV treatment of pool water has previously been reported with little concurrence between laboratory studies, field studies and research groups. In the current study, changes in concentration of seven out of eleven investigated volatile DBPs were observed in experiments using medium pressure UV treatment, with and without chlorine and after post-UV chlorination. Results showed that post-UV chlorine consumption increased, dose-dependently, with UV treatment dose. A clear absence of trihalomethane formation by UV and UV with chlorine was observed, while small yet statistically significant increases in dichloroacetonitrile and dichloropropanone concentrations were detected. Results indicate that post-UV chlorination clearly induced secondary formation of several DBPs. However, the formation of total trihalomethanes was no greater than what could be replicated by performing the DBP formation assay with higher chlorine concentrations to simulate extended chlorination. Post-UV chlorination of water from a swimming pool that continuously uses UV treatment to control combined chlorine could not induce secondary formation for most DBPs. Concurrence for induction of trihalomethanes was identified between post-UV chlorination treatments and simulated extended chlorination time treatment. Trihalomethanes could not be induced by UV treatment of water from a continuously UV treated pool. This indicates that literature reports of experimentally induced trihalomethane formation by UV may be a result of kinetic increase in formation by UV. However, this does not imply that higher trihalomethane concentrations would occur in pools that apply continuous UV treatment. The bromine fraction of halogens in formed trihalomethanes increased with UV dose. This indicates that UV removes bromine atoms from larger molecules that participate in trihalomethane production during post-UV chlorination. Additionally, no significant

  15. Modeling Formation of Globular Clusters: Beacons of Galactic Star Formation

    CERN Document Server

    Gnedin, Oleg Y

    2010-01-01

    Modern hydrodynamic simulations of galaxy formation are able to predict accurately the rates and locations of the assembly of giant molecular clouds in early galaxies. These clouds could host star clusters with the masses and sizes of real globular clusters. I describe current state-of-the-art simulations aimed at understanding the origin of the cluster mass function and metallicity distribution. Metallicity bimodality of globular cluster systems appears to be a natural outcome of hierarchical formation and gradually declining fraction of cold gas in galaxies. Globular cluster formation was most prominent at redshifts z>3, when massive star clusters may have contributed as much as 20% of all galactic star formation.

  16. A unified multiwavelength model of galaxy formation

    Science.gov (United States)

    Lacey, Cedric G.; Baugh, Carlton M.; Frenk, Carlos S.; Benson, Andrew J.; Bower, Richard G.; Cole, Shaun; Gonzalez-Perez, Violeta; Helly, John C.; Lagos, Claudia D. P.; Mitchell, Peter D.

    2016-11-01

    We present a new version of the GALFORM semi-analytical model of galaxy formation. This brings together several previous developments of GALFORM into a single unified model, including a different initial mass function (IMF) in quiescent star formation and in starbursts, feedback from active galactic nuclei suppressing gas cooling in massive haloes, and a new empirical star formation law in galaxy discs based on their molecular gas content. In addition, we have updated the cosmology, introduced a more accurate treatment of dynamical friction acting on satellite galaxies, and updated the stellar population model. The new model is able to simultaneously explain both the observed evolution of the K-band luminosity function and stellar mass function, and the number counts and redshift distribution of sub-mm galaxies selected at 850 μm. This was not previously achieved by a single physical model within the Λcold dark matter framework, but requires having an IMF in starbursts that is somewhat top-heavy. The new model is tested against a wide variety of observational data covering wavelengths from the far-UV to sub-mm, and redshifts from z = 0 to 6, and is found to be generally successful. These observations include the optical and near-infrared (IR) luminosity functions, H I mass function, fraction of early type galaxies, Tully-Fisher, metallicity-luminosity and size-luminosity relations at z = 0, as well as far-IR number counts, and far-UV luminosity functions at z ˜ 3-6. Discrepancies are, however, found in galaxy sizes and metallicities at low luminosities, and in the abundance of low-mass galaxies at high-z, suggesting the need for a more sophisticated model of supernova feedback.

  17. A Network Formation Model Based on Subgraphs

    CERN Document Server

    Chandrasekhar, Arun

    2016-01-01

    We develop a new class of random-graph models for the statistical estimation of network formation that allow for substantial correlation in links. Various subgraphs (e.g., links, triangles, cliques, stars) are generated and their union results in a network. We provide estimation techniques for recovering the rates at which the underlying subgraphs were formed. We illustrate the models via a series of applications including testing for incentives to form cross-caste relationships in rural India, testing to see whether network structure is used to enforce risk-sharing, testing as to whether networks change in response to a community's exposure to microcredit, and show that these models significantly outperform stochastic block models in matching observed network characteristics. We also establish asymptotic properties of the models and various estimators, which requires proving a new Central Limit Theorem for correlated random variables.

  18. Opinion formation models on a gradient.

    Directory of Open Access Journals (Sweden)

    Michael T Gastner

    Full Text Available Statistical physicists have become interested in models of collective social behavior such as opinion formation, where individuals change their inherently preferred opinion if their friends disagree. Real preferences often depend on regional cultural differences, which we model here as a spatial gradient g in the initial opinion. The gradient does not only add reality to the model. It can also reveal that opinion clusters in two dimensions are typically in the standard (i.e., independent percolation universality class, thus settling a recent controversy about a non-consensus model. However, using analytical and numerical tools, we also present a model where the width of the transition between opinions scales proportional g(-1/4, not proportional g(-4/7 as in independent percolation, and the cluster size distribution is consistent with first-order percolation.

  19. Purge efficiency in the determination of trihalomethanes in water by purge-and-trap gas chromatography.

    Science.gov (United States)

    Ruiz-Bevia, Francisco; Fernandez-Torres, Maria J; Blasco-Alemany, Maria P

    2009-01-26

    Purge-and-trap gas chromatography-mass spectrometry (PT-GC-MS) has become an accepted method for the analysis of trihalomethanes (THMs) in water. The purge-and-trap technique is based on an efficient transfer of volatile organic compounds from the liquid (contained in the purge chamber) to the gaseous phase by bubbling with an inert gas. The aim of this work was to study the purge system's efficiency by means of several consecutive purge cycles lasting 11 min each of the same liquid sample. The concentration range chosen of THMs was very wide [5-200 microg L(-1)]. The inert gas flow rate was 40 mL min(-1), and experiments were performed at temperatures of 25, 35 and 50 degrees C. Bromoform (CHBr(3)), the least volatile compound, needed 19 cycles to be purged quantitatively at a concentration of 200 microg L(-1) and only 7 cycles at 5 microg L(-1) for a 25 mL sample at 25 degrees C. Chloroform (CHCl(3)), the most volatile compound, required 4 cycles to be fully extracted at 200 microg L(-1) and 2 at 5 microg L(-1). Finally, Novak's theoretical model, based on the distribution constant between gas and liquid phases, was used to correlate the THMs purging extraction data.

  20. Trihalomethanes in liver pathology: Mitochondrial dysfunction and oxidative stress in the mouse.

    Science.gov (United States)

    Faustino-Rocha, Ana I; Rodrigues, D; da Costa, R Gil; Diniz, C; Aragão, S; Talhada, D; Botelho, M; Colaço, A; Pires, M J; Peixoto, F; Oliveira, P A

    2016-08-01

    Trihalomethanes (THMs) are disinfection byproducts found in chlorinated water, and are associated with several different kinds of cancer in human populations and experimental animal models. Metabolism of THMs proceeds through enzymes such as GSTT1 and CYP2E1 and gives rise to reactive intermediates, which form the basis for their toxic activities. The aim of this study was to assess the mitochondrial dysfunction caused by THMs at low levels, and the resulting hepatic histological and biochemical changes in the mouse. Male ICR mice were administered with two THMs: dibromochloromethane (DBCM) and bromodichloromethane (BDCM); once daily, by gavage, to a total of four administrations. Animals were sacrificed four weeks after DBCM and BDCM administrations. Blood biochemistry was performed for alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total bilirubin (TB), albumin (Alb), total protein (TP), creatinine, and urea. Animals exposed to DBCM and BDCM showed elevated ALT and TB levels (p stress (glutathione S-transferase (GST)) in hepatic tissues (p stress in liver toxicity caused by DBCM and BDCM. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1009-1016, 2016.

  1. Dynamical Models of Terrestrial Planet Formation

    CERN Document Server

    Lunine, Jonathan I; Raymond, Sean N; Morbidelli, Alessandro; Quinn, Thomas; Graps, Amara

    2009-01-01

    We review the problem of the formation of terrestrial planets, with particular emphasis on the interaction of dynamical and geochemical models. The lifetime of gas around stars in the process of formation is limited to a few million years based on astronomical observations, while isotopic dating of meteorites and the Earth-Moon system suggest that perhaps 50-100 million years were required for the assembly of the Earth. Therefore, much of the growth of the terrestrial planets in our own system is presumed to have taken place under largely gas-free conditions, and the physics of terrestrial planet formation is dominated by gravitational interactions and collisions. The earliest phase of terrestrial-planet formation involve the growth of km-sized or larger planetesimals from dust grains, followed by the accumulations of these planetesimals into ~100 lunar- to Mars-mass bodies that are initially gravitationally isolated from one-another in a swarm of smaller planetesimals, but eventually grow to the point of sig...

  2. Continuum Modeling of Biological Network Formation

    KAUST Repository

    Albi, Giacomo

    2017-04-10

    We present an overview of recent analytical and numerical results for the elliptic–parabolic system of partial differential equations proposed by Hu and Cai, which models the formation of biological transportation networks. The model describes the pressure field using a Darcy type equation and the dynamics of the conductance network under pressure force effects. Randomness in the material structure is represented by a linear diffusion term and conductance relaxation by an algebraic decay term. We first introduce micro- and mesoscopic models and show how they are connected to the macroscopic PDE system. Then, we provide an overview of analytical results for the PDE model, focusing mainly on the existence of weak and mild solutions and analysis of the steady states. The analytical part is complemented by extensive numerical simulations. We propose a discretization based on finite elements and study the qualitative properties of network structures for various parameter values.

  3. Assessment of lifetime exposure to trihalomethanes through different routes.

    Science.gov (United States)

    Villanueva, C M; Cantor, K P; Grimalt, J O; Castaño-Vinyals, G; Malats, N; Silverman, D; Tardon, A; Garcia-Closas, R; Serra, C; Carrato, A; Rothman, N; Real, F X; Dosemeci, M; Kogevinas, M

    2006-04-01

    To evaluate lifetime exposure to trihalomethanes (THM) through ingestion, inhalation, and dermal absorption in a hospital based case-control study of bladder cancer conducted between 1998 and 2001 in five areas of Spain. The study base was comprised of subjects living in the catchment areas of the participating hospitals. Individual information on water related habits was obtained from personal interviews of 1219 cases and 1271 controls: residential and occupational history, drinking water source at each residence and job, amount of water consumption, frequency and duration of showering, bathing, and swimming pool attendance. THM levels, water source history, and year when chlorination started in study areas were ascertained through measurements in drinking water samples and questionnaires to water companies and local authorities. Estimates of THM levels covered 79% of the subjects' person-years of exposure. Current and historical average THM levels in water were correlated. Control subjects reported that drinking water source in the last residence was municipal for 63%, bottled for 22%, private well for 2%, and other sources for 13%. For the time window between age 15 and the time of interview, average residential THM level was 32.2 mug/l. THM exposure through ingestion was 23.7 mug/day on average, and was correlated with the ingestion THM level in the workplace. Overall, 79% usually took showers, 16% usually took baths, and 13% had ever attended a swimming pool. Between 21% and 45% of controls unexposed to THM through ingestion were evaluated as moderately or highly exposed through showering or bathing, and 5-10% were exposed through swimming in pools. The importance of evaluating different routes is underscored by findings from experimental studies showing substantial differences in THM uptake and internal distribution by route.

  4. Toy Models for Galaxy Formation versus Simulations

    CERN Document Server

    Dekel, A; Tweed, D; Cacciato, M; Ceverino, D; Primack, J R

    2013-01-01

    We describe simple useful toy models for key processes of galaxy formation in its most active phase, at z > 1, and test the approximate expressions against the typical behaviour in a suite of high-resolution hydro-cosmological simulations of massive galaxies at z = 4-1. We address in particular the evolution of (a) the total mass inflow rate from the cosmic web into galactic haloes based on the EPS approximation, (b) the penetration of baryonic streams into the inner galaxy, (c) the disc size, (d) the implied steady-state gas content and star-formation rate (SFR) in the galaxy subject to mass conservation and a universal star-formation law, (e) the inflow rate within the disc to a central bulge and black hole as derived using energy conservation and self-regulated Q ~ 1 violent disc instability (VDI), and (f) the implied steady state in the disc and bulge. The toy models provide useful approximations for the behaviour of the simulated galaxies. We find that (a) the inflow rate is proportional to mass and to (...

  5. Modeling generic aspects of ideal fibril formation

    CERN Document Server

    Michel, Denis

    2016-01-01

    Many different proteins self-aggregate into insoluble fibrils growing apically by reversible addition of elementary building blocks. But beyond this common principle, the modalities of fibril formation are very disparate, with various intermediate forms which can be reshuffled by minor modifications of physico-chemical conditions or amino-acid sequences. To bypass this complexity, the multifaceted phenomenon of fibril formation is reduced here to its most elementary principles defined for a linear prototype of fibril. Selected generic features, including nucleation, elongation and conformational recruitment, are modeled using minimalist hypotheses and tools, by separating equilibrium from kinetic aspects and in vitro from in vivo conditions. These reductionist approaches allow to bring out known and new rudiments, including the kinetic and equilibrium effects of nucleation, the dual influence of elongation on nucleation, the kinetic limitations on nucleation and fibril numbers and the accumulation of complexe...

  6. Numerical modeling of the first star's formation

    Science.gov (United States)

    Audit, E.; Chièe, J.-P.

    Although our knowledge in cosmology has considerably advanced in recent years, the z ≃5 - z ≃1000 period, or dark age, is largely unknown on the observational point of view, and theoretical as well. It is nevertheless a decisive step, where the first baryonic objects form (Pop III stars). These are likely to be responsible for the reionization of the universe at about z ≅10 and they synthesize the first heavy elements, fundamental for the next generation objects. I will first present the numerical model developed to study their formation. I will discuss the included physics (hydrodynamics of gas and dark matter, out of equilibrium thermochemistry, radiative transfer, convection...). Then I will present results from a cloud collapse to the formation of a proto-star, illustrating the influence of the physics. Finally, I will present the 1D to 3D perspectives of this work.

  7. A simple model of ostracism formation.

    Directory of Open Access Journals (Sweden)

    Pilwon Kim

    Full Text Available We study formation of ostracism in a society from a game theoretical perspective. The dynamics of group formation is complicated in that the choices of the individuals and the form of the groups mutually affect each other in the process. A suggested simple model shows that individual efforts to increase his/her own sense of belonging is responsible for both growth of groups and creation of an outcast. Once a person happens to get behind in synchronizing with others, tendency to alienate him may grow among others, possibly making him left out in the end. Alienating minority occurs even when there is a penalty for disliking and people are encouraged to favor others. Considering that the target is accidentally picked, we can understand ostracism as an inherent part of the group formation, rather than a result of specific discrepancy among people. Another finding is that a single individual who seeks for unconditional unification of the society ("philanthropist" likely invites his/her own isolation from the society, while the existence of such person generally promotes coalition of others.

  8. A simple model of ostracism formation.

    Science.gov (United States)

    Kim, Pilwon

    2014-01-01

    We study formation of ostracism in a society from a game theoretical perspective. The dynamics of group formation is complicated in that the choices of the individuals and the form of the groups mutually affect each other in the process. A suggested simple model shows that individual efforts to increase his/her own sense of belonging is responsible for both growth of groups and creation of an outcast. Once a person happens to get behind in synchronizing with others, tendency to alienate him may grow among others, possibly making him left out in the end. Alienating minority occurs even when there is a penalty for disliking and people are encouraged to favor others. Considering that the target is accidentally picked, we can understand ostracism as an inherent part of the group formation, rather than a result of specific discrepancy among people. Another finding is that a single individual who seeks for unconditional unification of the society ("philanthropist") likely invites his/her own isolation from the society, while the existence of such person generally promotes coalition of others.

  9. Microbial degradation of plant leachate alters lignin phenols and trihalomethane precursors

    Science.gov (United States)

    Pellerin, Brian A.; Hernes, Peter J.; Saraceno, John Franco; Spencer, Robert G.M.; Bergamaschi, Brian A.

    2010-01-01

    Although the importance of vascular plant-derived dissolved organic carbon (DOC) in freshwater systems has been studied, the role of leached DOC as precursors of disinfection byproducts (DBPs) during drinking water treatment is not well known. Here we measured the propensity of leachates from four crops and four aquatic macrophytes to form trihalomethanes (THMs)—a regulated class of DBPs—before and after 21 d of microbial degradation. We also measured lignin phenol content and specific UV absorbance (SUVA254) to test the assumption that aromatic compounds from vascular plants are resistant to microbial degradation and readily form DBPs. Leaching solubilized 9 to 26% of total plant carbon, which formed 1.93 to 6.72 mmol THM mol C-1 However, leachate DOC concentrations decreased by 85 to 92% over the 21-d incubation, with a concomitant decrease of 67 to 92% in total THM formation potential. Carbon-normalized THM yields in the residual DOC pool increased by 2.5 times on average, consistent with the preferential uptake of nonprecursor material. Lignin phenol concentrations decreased by 64 to 96% over 21 d, but a lack of correlation between lignin content and THM yields or SUVA254 suggested that lignin-derived compounds are not the source of increased THM precursor yields in the residual DOC pool. Our results indicate that microbial carbon utilization alters THM precursors in ecosystems with direct plant leaching, but more work is needed to identify the specific dissolved organic matter components with a greater propensity to form DBPs and affect watershed management, drinking water quality, and human health.

  10. Microbial degradation of plant leachate alters lignin phenols and trihalomethane precursors

    Science.gov (United States)

    Pellerin, Brian A.; Hernes, Peter J.; Saraceno, John Franco; Spencer, Robert G.M.; Bergamaschi, Brian A.

    2010-01-01

    Although the importance of vascular plant-derived dissolved organic carbon (DOC) in freshwater systems has been studied, the role of leached DOC as precursors of disinfection byproducts (DBPs) during drinking water treatment is not well known. Here we measured the propensity of leachates from four crops and four aquatic macrophytes to form trihalomethanes (THMs)—a regulated class of DBPs—before and after 21 d of microbial degradation. We also measured lignin phenol content and specific UV absorbance (SUVA254) to test the assumption that aromatic compounds from vascular plants are resistant to microbial degradation and readily form DBPs. Leaching solubilized 9 to 26% of total plant carbon, which formed 1.93 to 6.72 mmol THM mol C-1 However, leachate DOC concentrations decreased by 85 to 92% over the 21-d incubation, with a concomitant decrease of 67 to 92% in total THM formation potential. Carbon-normalized THM yields in the residual DOC pool increased by 2.5 times on average, consistent with the preferential uptake of nonprecursor material. Lignin phenol concentrations decreased by 64 to 96% over 21 d, but a lack of correlation between lignin content and THM yields or SUVA254 suggested that lignin-derived compounds are not the source of increased THM precursor yields in the residual DOC pool. Our results indicate that microbial carbon utilization alters THM precursors in ecosystems with direct plant leaching, but more work is needed to identify the specific dissolved organic matter components with a greater propensity to form DBPs and affect watershed management, drinking water quality, and human health.

  11. Microbial degradation of plant leachate alters lignin phenols and trihalomethane precursors.

    Science.gov (United States)

    Pellerin, Brian A; Hernes, Peter J; Saraceno, JohnFranco; Spencer, Robert G M; Bergamaschi, Brian A

    2010-01-01

    Although the importance of vascular plant-derived dissolved organic carbon (DOC) in freshwater systems has been studied, the role of leached DOC as precursors of disinfection byproducts (DBPs) during drinking water treatment is not well known. Here we measured the propensity of leachates from four crops and four aquatic macrophytes to form trihalomethanes (THMs)-a regulated class of DBPs-before and after 21 d of microbial degradation. We also measured lignin phenol content and specific UV absorbance (SUVA(254)) to test the assumption that aromatic compounds from vascular plants are resistant to microbial degradation and readily form DBPs. Leaching solubilized 9 to 26% of total plant carbon, which formed 1.93 to 6.72 mmol THM mol C(-1). However, leachate DOC concentrations decreased by 85 to 92% over the 21-d incubation, with a concomitant decrease of 67 to 92% in total THM formation potential. Carbon-normalized THM yields in the residual DOC pool increased by 2.5 times on average, consistent with the preferential uptake of nonprecursor material. Lignin phenol concentrations decreased by 64 to 96% over 21 d, but a lack of correlation between lignin content and THM yields or SUVA(254) suggested that lignin-derived compounds are not the source of increased THM precursor yields in the residual DOC pool. Our results indicate that microbial carbon utilization alters THM precursors in ecosystems with direct plant leaching, but more work is needed to identify the specific dissolved organic matter components with a greater propensity to form DBPs and affect watershed management, drinking water quality, and human health.

  12. Exposure assessment for trihalomethanes in municipal drinking water and risk reduction strategy.

    Science.gov (United States)

    Chowdhury, Shakhawat

    2013-10-01

    Lifetime exposure to disinfection byproducts (DBPs) in municipal water may pose risks to human health. Current approaches of exposure assessments use DBPs in cold water during showering, while warming of chlorinated water during showering may increase trihalomethane (THM) formation in the presence of free residual chlorine. Further, DBP exposure through dermal contact during showering is estimated using steady-state condition between the DBPs in shower water impacting on human skin and skin exposed to shower water. The lag times to achieve steady-state condition between DBPs in shower water and human skin can vary in the range of 9.8-391.2 min, while shower duration is often less than the lag times. Assessment of exposure without incorporating these factors might have misinterpreted DBP exposure in some previous studies. In this study, exposure to THMs through ingestion was estimated using cold water THMs, while THM exposure through inhalation and dermal contact during showering was estimated using THMs in warm water. Inhalation of THMs was estimated using THM partition into the shower air, while dermal uptake was estimated by incorporating lag times (e.g., unsteady and steady-state phases of exposure) during showering. Probabilistic approach was followed to incorporate uncertainty in the assessment. Inhalation and dermal contact during showering contributed 25-60% of total exposure. Exposure to THMs during showering can be controlled by varying shower stall volume, shower duration and air exchange rate following power law equations. The findings might be useful in understanding exposure to THMs, which can be extended to other volatile compounds in municipal water.

  13. A simple model for pediment formation.

    Science.gov (United States)

    Mercier, Jonathan; Braun, Jean; Guillocheau, François; Robin, Cecile; Simon, Brendan

    2016-04-01

    Pediments are very flat and smooth erosive surfaces, connected to higher relief by a scarp, that covers up to two thirds of the Earth's surface. A physical mechanism to explain their formation remains elusive. Commonly accepted hypotheses include: (1) the widening of an incised river network (lateral corrasion of Gilbert, 1877), (2) sheetflow erosion, (3) subsurface weathering and exhumation (Strudley et al, 2006) and (4) slope retreat, usually at the base of an escarpment (King, 1949), potentially helped by flexural isostatic rebound (Pelletier, 2010). Here we explore the third hypothesis, which we believe applies mostly in regions characterised by intense rainfall where deep weathering profiles are commonly observed. In this study, using a new coupled model of groundwater flow and surface erosion, we highlight the critical impact of the geometry of the water table and of the unsaturated zone within a weathering profile to explain its evolution through time. The model is calibrated and used to explain the formation of pediments as the product of a dynamical balance between weathering front propagation and surface erosion. We also explore the effects of abrupt changes in rainfall intensity and base level drop on the geometry of the predicted pediments.

  14. Modeling generic aspects of ideal fibril formation

    Energy Technology Data Exchange (ETDEWEB)

    Michel, D., E-mail: denis.michel@live.fr [Universite de Rennes1-IRSET, Campus de Beaulieu Bat. 13, 35042 Rennes (France)

    2016-01-21

    Many different proteins self-aggregate into insoluble fibrils growing apically by reversible addition of elementary building blocks. But beyond this common principle, the modalities of fibril formation are very disparate, with various intermediate forms which can be reshuffled by minor modifications of physico-chemical conditions or amino-acid sequences. To bypass this complexity, the multifaceted phenomenon of fibril formation is reduced here to its most elementary principles defined for a linear prototype of fibril. Selected generic features, including nucleation, elongation, and conformational recruitment, are modeled using minimalist hypotheses and tools, by separating equilibrium from kinetic aspects and in vitro from in vivo conditions. These reductionist approaches allow to bring out known and new rudiments, including the kinetic and equilibrium effects of nucleation, the dual influence of elongation on nucleation, the kinetic limitations on nucleation and fibril numbers, and the accumulation of complexes in vivo by rescue from degradation. Overlooked aspects of these processes are also pointed: the exponential distribution of fibril lengths can be recovered using various models because it is attributable to randomness only. It is also suggested that the same term “critical concentration” is used for different things, involved in either nucleation or elongation.

  15. Exposure to Brominated Trihalomethanes in Water During Pregnancy and Micronuclei Frequency in Maternal and Cord Blood Lymphocytes

    Science.gov (United States)

    Pedersen, Marie; Patelarou, Evridiki; Decordier, Ilse; Vande Loock, Kim; Chatzi, Leda; Espinosa, Ana; Fthenou, Eleni; Nieuwenhuijsen, Mark J.; Gracia-Lavedan, Esther; Stephanou, Euripides G.; Kirsch-Volders, Micheline; Kogevinas, Manolis

    2013-01-01

    Background: Water disinfection by-products have been associated with an increased cancer risk. Micronuclei (MN) frequency in lymphocytes is a marker of genomic damage and can predict adult cancer risk. Objective: We evaluated maternal exposure to drinking water brominated trihalomethanes (BTHM) in relation to MN frequency in maternal and cord blood lymphocytes. Methods: MN frequency was examined in 214 mothers and 223 newborns from the Rhea mother–child cohort in Crete, Greece, in 2007–2008. Residential BTHM water concentrations were estimated during pregnancy using tap water analyses and modeling. Questionnaires on water related habits were used to estimate BTHM exposure from all routes. Associations between BTHM and MN frequency were estimated using negative binomial regression. Results: BTHM concentrations in residential tap water during pregnancy ranged from 0.06 to 7.1 μg/L. MN frequency in maternal binucleated lymphocytes was found to increase with BTHM concentrations in residential water for exposure during the first [rate ratio (RR) for 1 μg/L = 1.05; 95% CI: 1.00, 1.11] and second trimesters (RR for 1 μg/L = 1.03; 95% CI: 1.00, 1.06), and through all routes of BTHM exposure during the first trimester (RR for 1 μg/week = 3.14; 95% CI: 1.16, 8.50). Conclusions: These findings suggest that exposure to BTHM may increase the frequency of MN in maternal binucleated lymphocytes. Citation: Stayner LT, Pedersen M, Patelarou E, Decordier I, Vande Loock K, Chatzi L, Espinosa A, Fthenou E, Nieuwenhuijsen MJ, Gracia-Lavedan E, Stephanou EG, Kirsch-Volders M, Kogevinas M. 2014. Exposure to brominated trihalomethanes in water during pregnancy and micronuclei frequency in maternal and cord blood lymphocytes. Environ Health Perspect 122:100–106; http://dx.doi.org/10.1289/ehp.1206434 PMID:24184846

  16. RISK ASSOCIATED WITH HUMAN EXPOSURE TO TRIHALOMETHANES (THMs IN THE WATER DISTRIBUTION NETWORK OF CLUJ-NAPOCA

    Directory of Open Access Journals (Sweden)

    CORNELIA DIANA ROMAN

    2013-03-01

    Full Text Available Trihalomethanes (THMs, as disinfection by-products resulted from water chlorination, can get into the body through ingestion of beverages, food or drinking water. This paper discusses the relationship between the use of drinking water from the public distribution network of Cluj-Napoca and exposure to trihalomethanes. To better characterize individual water consumption, at home and at work, we applied a questionnaire to a group of 211 subjects from Cluj-Napoca, while assessing their current exposure to THMs by collecting and analyzing water from different points of the distribution network. The data obtained were statistically processed and then used to calculate the exposure dose and cancer risk for both adults and children. The results showed that subjects consumed for drinking both bottled water and water from the distribution network, but for preparing food and beverages (tea, coffee they used only water from the public distribution network. The average daily consumption of drinking water from the distribution network, is 1.4 l/day for adults, including beverages prepared with treated water. The surveyed subjects declared that they consume coffee or tea, in percentage of 88%, 94.4% respectively. The calculation of the exposure dose, daily intake and risk of cancer was achieved by using a model developed by the Agency for Toxic Substances and Disease Registry (ATSDR from the USA to calculate the dose and assess the risk of cancer. Our study shows that the cancer risk to THMs is increasing related to the higher daily intake of the drinking water, being higher for chloroform compared to dibromochloroform. For the measured concentrations of chloroform and dibromochloroform in drinking water and the average daily consumption of 1.4 l water/day, the probability of new cancers occurrence is at least 2.4 additional cases for 25 years of exposure and maximum 4.61 cases for 35 years of exposure in the existing background of a 1 million people.

  17. Modeling of Astrochemistry during Star Formation

    Science.gov (United States)

    Hincelin, Ugo; Herbst, Eric; Chang, Qiang; Vasyunina, Tatiana; Aikawa, Yuri; Furuya, Kenji

    2014-06-01

    Interstellar matter is not inert, but is constantly evolving. On the one hand, its physical characteristics such as its density and its temperature, and on the other hand, its chemical characteristics such as the abundances of the species and their distribution, can change drastically. The phases of this evolution spread over different timescales, and this matter evolves to create very different objects such as molecular clouds (T ˜ 10 K, n ˜ 10^4 cm-3, t ˜ 10^6 years), collapsing prestellar cores (inner core : T ˜ 1000 K, n ˜ 1016 cm-3, t ˜ 10^4 years), protostellar cores (inner core : T ˜ 10^5 K, n ˜ 1024 cm-3, t ˜ 10^6 years), or protoplanetary disks (T ˜ 10-1000 K, n ˜ 109-1012 cm-3, t ˜ 10^7 years). These objects are the stages of the star formation process. Starting from the diffuse cloud, matter evolves to form molecular clouds. Then, matter can condense to form prestellar cores, which can collapse to form a protostar surrounded by a protoplanetary disk. The protostar can evolve in a star, and planets and comets can be formed in the disk. Thus, modeling of astrochemistry during star formation should consider chemical and physical evolution in parallel. We present a new gas-grain chemical network involving deuterated species, which takes into account ortho, para, and meta states of H_2, D_2, H_3^+, H_2D^+, D_2H^+, and D_3^+. It includes high temperature gas phase reactions, and some ternary reactions for high density, so that it should be able to simulate media with temperature equal to [10;800] K and density equal to [˜10^4;˜1012] cm-3. We apply this network to the modeling of low-mass and high-mass star formation, using a gas-grain chemical code coupled to a time dependent physical structure. Comparisons with observational constraints, such as the HDO/H_2O ratio in high mass star forming region, give good agreement which is promising. Besides, high density conditions have highlighted some limitations of our grain surface modeling. We present a

  18. An empirical behavioral model of price formation

    CERN Document Server

    Mike, S

    2005-01-01

    Although behavioral economics has demonstrated that there are many situations where rational choice is a poor empirical model, it has so far failed to provide quantitative models of economic problems such as price formation. We make a step in this direction by developing empirical models that capture behavioral regularities in trading order placement and cancellation using data from the London Stock Exchange. For order placement we show that the probability of placing an order at a given price is well approximated by a Student distribution with less than two degrees of freedom, centered on the best quoted price. This result is surprising because it implies that trading order placement is symmetric, independent of the bid-ask spread, and the same for buying and selling. We also develop a crude but simple cancellation model that depends on the position of an order relative to the best price and the imbalance between buying and selling orders in the limit order book. These results are combined to construct a sto...

  19. The simplest model of galaxy formation I: A formation history model of galaxy stellar mass growth

    CERN Document Server

    Mutch, Simon J; Poole, Gregory B

    2013-01-01

    We introduce a simple model to self-consistently connect the growth of galaxies to the formation history of their host dark matter halos. Our model is defined by two simple functions: the "baryonic growth function" which controls the rate at which new baryonic material is made available for star formation, and the "physics function" which controls the efficiency with which this material is converted into stars. Using simple, phenomenologically motivated forms for both functions that depend only on a single halo property, we demonstrate the model's ability to reproduce the z=0 red and blue stellar mass functions. Furthermore, by adding redshift as a second input variable to the physics function we show that the reproduction of the global stellar mass function out to z=3 is improved. We conclude by discussing the general utility of our new model, highlighting its usefulness for creating mock galaxy samples which have a number of key advantages over those generated by other techniques.

  20. Modeling Pancake Formation with a Coupled Wave-Ice Model

    Science.gov (United States)

    Veeramony, J.; Orzech, M.; Shi, F.; Bateman, S. P.; Calantoni, J.

    2016-12-01

    Recent results from the ONR-sponsored Arctic Sea State DRI cruise (Thomson et al., 2016, EOS, in press) suggest that small-scale pancake ice formation is an important process in the initial recovery and refreezing of the Arctic pack ice each autumn. Ocean surface waves and ambient temperature play significant roles in shaping and/or limiting the pancake growth patterns, which may either facilitate or delay the recovery of the ice pack. Here we apply a phase-resolving, coupled wave-ice system, consisting of a CFD wave model (NHWAVE) and a discrete-element ice model (LIGGGHTS), to investigate the formation processes of pancake ice under different conditions. A series of simulations is run, each beginning with a layer of disconnected ice particles floating on the ocean surface. Wave conditions and ice bonding properties are varied to examine the effects of mild versus stormy conditions, wind waves versus swell, and warmer versus colder temperatures. Model runs are limited to domains of O(1 sq km). Initial tests have shown some success in replicating qualitative results from the Sea State cruise, including the formation of irregularly shaped pancakes from the "frazil" ice layer, changes in formation processes caused by varying ambient temperature (represented through variations in ice bonding strength), occasional rafting of one pancake on top of another, and increased wave attenuation as pancakes grow larger.

  1. Pattern formation in superdiffusion Oregonator model

    Science.gov (United States)

    Feng, Fan; Yan, Jia; Liu, Fu-Cheng; He, Ya-Feng

    2016-10-01

    Pattern formations in an Oregonator model with superdiffusion are studied in two-dimensional (2D) numerical simulations. Stability analyses are performed by applying Fourier and Laplace transforms to the space fractional reaction-diffusion systems. Antispiral, stable turing patterns, and travelling patterns are observed by changing the diffusion index of the activator. Analyses of Floquet multipliers show that the limit cycle solution loses stability at the wave number of the primitive vector of the travelling hexagonal pattern. We also observed a transition between antispiral and spiral by changing the diffusion index of the inhibitor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11205044 and 11405042), the Research Foundation of Education Bureau of Hebei Province, China (Grant Nos. Y2012009 and ZD2015025), the Program for Young Principal Investigators of Hebei Province, China, and the Midwest Universities Comprehensive Strength Promotion Project.

  2. Structure formation in the DGP cosmological model

    CERN Document Server

    Koyama, K; Koyama, Kazuya; Maartens, Roy

    2006-01-01

    The DGP brane-world model provides an alternative to the standard LCDM cosmology, in which the late universe accelerates due to a modification of gravity rather than vacuum energy. The cosmological constant $\\Lambda$ in LCDM is replaced by a single parameter, the crossover scale $r_c$, in DGP. The Supernova redshift observations can be fitted by both models, with $\\Lambda\\sim H_0^2$ and $r_c \\sim H_0^{-1}$. This degeneracy is broken by structure formation, which is suppressed in different ways in the two models. There is some confusion in the literature about how the standard linear growth factor is modified in DGP. While the luminosity distance can be computed purely from the modified 4-dimensional Friedman equation, the evolution of density perturbations requires an analysis of the 5-dimensional gravitational field. We show that if the 5-dimensional effects are inappropriately neglected, then the 4-dimensional Bianchi identities are violated and the computed growth factor is incorrect. By using the 5-dimens...

  3. Investigation of Amount and Effective Factors on Trihalomethane Production in PotableWater of Yazd

    Directory of Open Access Journals (Sweden)

    Andalib A.H.

    2011-06-01

    Full Text Available Background and Objectives:Yazd province is located in the central desert part of Iran in which water scarcity was one of the most important problems. This has been recently solved to some extent, due to the approved channel project of water transferring from Isfahan to Yazd. Chlorination is usually used in the last stage of water treatment for disinfection in the networks, treatment plants, storages and channel stations. The possibility of carcinogen lateral composites formation is expected by tri-halo-methanes (THMs due to the reactions occurs between the natural organic materials and free chlorine available in water. Based on the established standard by the country, the permissible limit of THMs in water is 200 mg/L. In this research, in addition to the amount of THMs and their distribution in Yazd water transferring channel and the city water network system, the important parameters and their correlations with THMs formation were discussed.Materials and Methods: In a year of sampling period, the concentrations of THMs including the four major components of chloroform, bromoform, bromo di-chloro methane and di-bromo chloro methane during all seasons were measured using gas chromatograph and analyzed. This was done for 11 stations including Zayande-rood Basin River and Isfahan water treatment plant up to Yazd Shehneh storage, stations and inline equalization tanks and also five regions of Yazd city network.Results: According to the results, the maximum rate of THMs (51.14 mg/L during the sampling period in summer for Yazd city network and in ancient context of Jamea Mosque district was found. In addition, the minimum concentration of THMs was 1.60 mg/L in winter for the domestic network of the city which was related to Azad Shahr district. The Average total amount of THMs during sampling periods in all stations was 12.26 mg/L. Conclusion: SPSS and Excel softwares were used to analyze the research data in the descriptive and inferential manner

  4. Seasonal variations of chemical and physical characteristics of dissolved organic matter and trihalomethane precursors in a reservoir: a case study.

    Science.gov (United States)

    Wei, Qun-shan; Feng, Cheng-hong; Wang, Dong-sheng; Shi, Bao-you; Zhang, Li-tian; Wei, Qia; Tang, Hong-xiao

    2008-01-31

    Dissolved organic matter (DOM) and its potential to form disinfection by-products (DBPs) during water treatment are of great public health concern. Understanding the seasonal changes in DOM composition and their reactivity in DBP formation could lead to a better treatment of drinking water and a more consistent water quality. DOM from the East-Lake, a reservoir in the south-China, was fractionated and characterized by XAD resin adsorption (RA) and ultrafiltration (UF) techniques during different seasons within a year. The properties of chemical fractions (isolated by RA) appeared more stable than those of physical fractions (separated by UF) throughout the sampling period. The relative contribution of each chemical fraction to the total dissolved organic carbon (DOC), UV(254) absorbance and trihalomethane formation potential (THMFP) remained relatively constant across the sampling period. However, the physical (molecular weight) fractions of the DOM exhibited large seasonal changes in UV(254) and THMFP. Compared to the parameter of DOC, the THMFP and specific THMFP (STHMFP) of either chemical or physical fractions were more variable. In terms of DOC concentration, the hydrophobic acids (HoA) and hydrophilic matter (HiM) dominated in the DOM in most of the seasons; while the components with molecular weight of 10-30 kDa and less than 1 kDa were the predominant physical fractions.

  5. Formation and distribution of disinfection by-products during chlorine disinfection in the presence of bromide ion

    Institute of Scientific and Technical Information of China (English)

    LI Bo; QU JiuHui; LIU HuiJuan; ZHAO Xu

    2008-01-01

    The influences of contact time and pH value on the formation and distribution of four species of triha-lomethanes and five species of haloacetic acids during chlorination in the presence of bromine were investigated. Results showed that the distribution of molar fraction of trihalomethanes varied with contact time due to the change of bromide ion concentration during chlorination. Most of the triha-lomethanes comprising bromine-containing species and the favored products of the haloacetic acids were chlorine-containing species after 24 h of chlorination. The extent of bromine incorporation in tri-halomethanes and haloacetic acids both decreased with time. The contact time also had influence on the formation rate of different species of haloacetic acids. The formation and distribution of triha-lomethanes and haloacetic acids strongly depended on the chlorination pH value. All of the triha-lomethanes species formation increased with the increase of pH value except the bromoform that had not been detected. The molar fraction of bromodichloromethane and dibromochloromethane contain-ing bromine increased with pH value while chloroform without bromine decreased. Under the pH range studied in this experiment, the predominant haloacetic acids species were trichloroacetic acid and dichloroacetic acid which all decreased with the increase of pH value and the level of TCAA was higher than that of DCAA.

  6. Alveolar breath sampling and analysis to assess trihalomethane exposures during competitive swimming training.

    OpenAIRE

    Lindstrom, A B; Pleil, J D; Berkoff, D C

    1997-01-01

    Alveolar breath sampling was used to assess trihalomethane (THM) exposures encountered by collegiate swimmers during a typical 2-hr training period in an indoor natatorium. The breath samples were collected at regular intervals before, during, and for 3 hr after a moderately intense training workout. Integrated and grab whole-air samples were collected during the training period to help determine inhalation exposures, and pool water samples were collected to help assess dermal exposures. Resu...

  7. A simple analytic model of wormhole formations

    CERN Document Server

    Maeda, Hideki

    2008-01-01

    An explicit and simple solution representing the wormhole formation is presented. The spacetime is constructed by gluing the Minkowski and Roberts spacetimes at null hypersurfaces in a regular manner. The parameters in the Roberts solution are required to give the negative kinetic term for the massless scalar field. Although a curvature singularity appears at the moment of the wormhole formation, it disappears instantaneously. This instantaneous singularity is weak in the both senses of Tipler and Kr\\'{o}lak along radial causal geodesics.

  8. Passive exposures of children to volatile trihalomethanes during domestic cleaning activities of their parents

    Energy Technology Data Exchange (ETDEWEB)

    Andra, Syam S. [Water and Health Laboratory, Cyprus International Institute for Environmental and Public Health in association with Harvard School of Public Health, Cyprus University of Technology, Limassol (Cyprus); Harvard-Cyprus Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA (United States); Charisiadis, Pantelis [Water and Health Laboratory, Cyprus International Institute for Environmental and Public Health in association with Harvard School of Public Health, Cyprus University of Technology, Limassol (Cyprus); Karakitsios, Spyros; Sarigiannis, Denis A. [Environmental Engineering Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, University Campus, Bldg. D, Rm 318, 54124 Thessaloniki (Greece); Chemical Process and Energy Resources Institute, Centre for Research and Technology Hellas, 57001 Thessaloniki-Thermi (Greece); Makris, Konstantinos C., E-mail: konstantinos.makris@cut.ac.cy [Water and Health Laboratory, Cyprus International Institute for Environmental and Public Health in association with Harvard School of Public Health, Cyprus University of Technology, Limassol (Cyprus)

    2015-01-15

    Domestic cleaning has been proposed as a determinant of trihalomethanes (THMs) exposure in adult females. We hypothesized that parental housekeeping activities could influence children's passive exposures to THMs from their mere physical presence during domestic cleaning. In a recent cross-sectional study (n=382) in Cyprus [41 children (<18y) and 341 adults (≥18y)], we identified 29 children who met the study's inclusion criteria. Linear regression models were applied to understand the association between children sociodemographic variables, their individual practices influencing ingestion and noningestion exposures to ΣTHMs, and their urinary THMs levels. Among the children-specific variables, age alone showed a statistically significant inverse association with their creatinine-adjusted urinary ΣTHMs (r{sub S}=−0.59, p<0.001). A positive correlation was observed between urinary ΣTHMs (ng g{sup −1}) of children and matched-mothers (r{sub S}=0.52, p=0.014), but this was not the case for their matched-fathers (r{sub S}=0.39, p=0.112). Time spent daily by the matched-mothers for domestic mopping, toilet and other cleaning activities using chlorine-based cleaning products was associated with their children's urinary THMs levels (r{sub S}=0.56, p=0.007). This trend was not observed between children and their matched-fathers urinary ΣTHMs levels, because of minimum amount of time spent by the latter in performing domestic cleaning. The proportion of variance of creatinine-unadjusted and adjusted urinary ΣTHMs levels in children that was explained by the matched-mothers covariates was 76% and 74% (p<0.001), respectively. A physiologically-based pharmacokinetic model adequately predicted urinary chloroform excretion estimates, being consistent with the corresponding measured levels. Our findings highlighted the influence of mothers' domestic cleaning activities towards enhancing passive THMs exposures of their children. The duration of such

  9. A mathematical model of star formation in the Galaxy

    Directory of Open Access Journals (Sweden)

    M.A. Sharaf

    2012-06-01

    Full Text Available This paper is generally concerned with star formation in the Galaxy, especially blue stars. Blue stars are the most luminous, massive and the largest in radius. A simple mathematical model of the formation of the stars is established and put in computational algorithm. This algorithm enables us to know more about the formation of the star. Some real and artificial examples had been used to justify this model.

  10. SAM: A Simple Averaging Model of Impression Formation

    Science.gov (United States)

    Lewis, Robert A.

    1976-01-01

    Describes the Simple Averaging Model (SAM) which was developed to demonstrate impression-formation computer modeling with less complex and less expensive procedures than are required by most established programs. (RC)

  11. A Process Model of Family Formation and Development

    Science.gov (United States)

    Garland, Diana R.

    2012-01-01

    Theoretical models of family formation have assumed sexual coupling as the foundation of family life. This article proposes instead a model of family formation predicated on the processes of taking care of one another, eating together, and sharing life together. The interpersonal dynamics that distinguish a family from other close relationships…

  12. Mark formation modeling in optical rewritable recording

    NARCIS (Netherlands)

    Brusche, J.H.; Segal, A.; Vuik, C.; Urbach, H.P.

    2006-01-01

    In optical rewritable recording media, such as the Blu-ray Disc, amorphous marks are formed on a crystalline background of a phase-change layer, by means of short, high power laser pulses. In order to improve this data storage concept, it is of great importance to understand the mark formation

  13. Mark formation modeling in optical rewritable recording

    NARCIS (Netherlands)

    Brusche, J.H.; Segal, A.; Vuik, C.; Urbach, H.P.

    2006-01-01

    In optical rewritable recording media, such as the Blu-ray Disc, amorphous marks are formed on a crystalline background of a phase-change layer, by means of short, high power laser pulses. In order to improve this data storage concept, it is of great importance to understand the mark formation proce

  14. Cloud and Star Formation in Disk Galaxy Models with Feedback

    CERN Document Server

    Shetty, Rahul

    2008-01-01

    We include feedback in global hydrodynamic simulations in order to study the star formation properties, and gas structure and dynamics, in models of galactic disks. We extend previous models by implementing feedback in gravitationally bound clouds: momentum is injected at a rate proportional to the star formation rate. This mechanical energy disperses cloud gas back into the surrounding ISM, truncating star formation in a given cloud, and raising the overall level of ambient turbulence. Propagating star formation can however occur as expanding shells collide, enhancing the density and triggering new cloud and star formation. By controlling the momentum injection per massive star and the specific star formation rate in dense gas, we find that the negative effects of high turbulence outweigh the positive ones, and in net feedback reduces the fraction of dense gas and thus the overall star formation rate. The properties of the large clouds that form are not, however, very sensitive to feedback, with cutoff masse...

  15. Modeling of tethered satellite formations using graph theory

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Smith, Roy S; Blanke, Mogens

    2011-01-01

    satellite formation and proposes a method to deduce the equations of motion for the attitude dynamics of the formation in a compact form. The use of graph theory and Lagrange mechanics together allows a broad class of formations to be described using the same framework. A method is stated for finding...... could form stable formations in space are cumbersome when done at a case to case basis, and a common framework providing a basic model of the dynamics of tethered satellite formations can therefore be advantageous. This paper suggests the use of graph theoretical quantities to describe a tethered...

  16. The fate of haloacetic acids and trihalomethanes in an aquifer storage and recovery program, Las Vegas, Nevada

    Science.gov (United States)

    Thomas, J.M.; McKay, W.A.; Colec, E.; Landmeyer, J.E.; Bradley, P.M.

    2000-01-01

    The fate of disinfection byproducts during aquifer storage and recovery (ASR) is evaluated for aquifers in Southern Nevada. Rapid declines of haloacetic acid (HAA) concentrations during ASR, with associated little change in Cl concentration, indicate that HAAs decline primarily by in situ microbial oxidation. Dilution is only a minor contributor to HAA concentration declines during ASR. Trihalomethane (THM) concentrations generally increased during storage of artificial recharge (AR) water and then declined during recovery. The decline of THM concentrations during recovery was primarily from dilution of current season AR water with residual AR water remaining in the aquifer from previous ASR seasons and native ground water. In more recent ASR seasons, for wells with the longest history of ASR, brominated THMs declined during storage and recovery by processes in addition to dilution. These conclusions about THMs are indicated by THM/Cl values and supported by a comparison of measured and model predicted THM concentrations. Geochemical mixing models were constructed using major-ion chemistry of the three end-member waters to calculate predicted THM concentrations. The decline in brominated THM concentrations in addition to that from dilution may result from biotransformation processes.

  17. Physical Models of Galaxy Formation in a Cosmological Framework

    OpenAIRE

    Somerville, Rachel S.; Davé, Romeel

    2014-01-01

    Modeling galaxy formation in a cosmological context presents one of the greatest challenges in astrophysics today, due to the vast range of scales and numerous physical processes involved. Here we review the current status of models that employ two leading techniques to simulate the physics of galaxy formation: semi-analytic models and numerical hydrodynamic simulations. We focus on a set of observational targets that describe the evolution of the global and structural properties of galaxies ...

  18. Extrasolar planets: constraints for planet formation models.

    Science.gov (United States)

    Santos, Nuno C; Benz, Willy; Mayor, Michel

    2005-10-14

    Since 1995, more than 150 extrasolar planets have been discovered, most of them in orbits quite different from those of the giant planets in our own solar system. The number of discovered extrasolar planets demonstrates that planetary systems are common but also that they may possess a large variety of properties. As the number of detections grows, statistical studies of the properties of exoplanets and their host stars can be conducted to unravel some of the key physical and chemical processes leading to the formation of planetary systems.

  19. UAV Formation Flight Based on Nonlinear Model Predictive Control

    Directory of Open Access Journals (Sweden)

    Zhou Chao

    2012-01-01

    Full Text Available We designed a distributed collision-free formation flight control law in the framework of nonlinear model predictive control. Formation configuration is determined in the virtual reference point coordinate system. Obstacle avoidance is guaranteed by cost penalty, and intervehicle collision avoidance is guaranteed by cost penalty combined with a new priority strategy.

  20. Exposição humana a trialometanos presentes em água tratada Human exposure to trihalomethanes in drinking water

    Directory of Open Access Journals (Sweden)

    Maria Y Tominaga

    1999-08-01

    Full Text Available Realizou-se uma revisão bibliográfica do período de 1974-1998, no MEDLINE, sobre compostos orgânicos halogenados derivados de hidrocarbonetos denominados de trialometanos. Muitos deles, reconhecidamente carcinogênicos para diferentes espécies animais, podem ser encontrados freqüentemente, inclusive entre nós, em águas tratadas e enviadas à população urbana. É o caso de compostos como o clorofórmio, bromodiclorometano, clorodibromometano e bromofórmio, resultantes da halogenação de precursores, principalmente substâncias húmicas e fúlvicas presentes na água que será tratada (clorada. Assim, descreve-se sua formação, fontes de exposição humana bem como os aspectos toxicológicos de maior importância: disposição cinética e espectro dos efeitos tóxicos (carcinogênicos, mutagênicos e teratogênicos decorrentes de exposições a longo prazo e baixas concentrações. Níveis seguros de exposição propostos são também fornecidos.Halogenated hydrocarbon compounds, some of them recognized as carcinogenic to different animal species can be found in drinking water. Chloroform, bromodichloromethane, dibromochloromethane and bromoform are the most important trihalomethanes found in potable water. They are produced in natural waters during chlorinated desinfection by the halogenation of precursors, specially humic and fulvic compounds. The review, in the MEDLINE covers the period from 1974 to 1998, presents the general aspects of the formation of trihalomethanes, sources of human exposure and their toxicological meaning for exposed organisms: toxicokinetic disposition and spectrum of toxic effects (carcinogenic, mutagenic and teratogenic.

  1. Optimal pH in chlorinated swimming pools - balancing formation of by-products

    DEFF Research Database (Denmark)

    Hansen, Kamilla Marie Speht; Albrechtsen, Hans-Jørgen; Andersen, Henrik Rasmus

    2013-01-01

    In order to identify the optimal pH range for chlorinated swimming pools the formation of trihalomethanes, haloacetonitriles and trichloramine was investigated in the pH-range 6.5–7.5 in batch experiments. An artificial body fluid analogue was used to simulate bather load as the precursor for by......-products. The chlorine-to-precursor ratio used in the batch experiments influenced the amounts of by-products formed, but regardless of the ratio the same trends in the effect of pH were observed. Trihalomethane formation was reduced by decreasing pH but haloacetonitrile and trichloramine formation increased...

  2. Polaron Model of the Formation of Hydrated Electron States

    OpenAIRE

    2015-01-01

    A computer simulation of the formation of photoexcited electrons in water is performed within the framework of a dynamic model. The obtained results are discussed in comparison with experimental data and theoretical estimates.

  3. A recurrent connectionist model of person impression formation.

    Science.gov (United States)

    Van Overwalle, Frank; Labiouse, Christophe

    2004-01-01

    Major findings in impression formation are reviewed and modeled from a connectionist perspective. The findings are in the areas of primacy and recency in impression formation, asymmetric diagnosticity of ability- and morality-related traits, increased recall for trait-inconsistent information, assimilation and contrast in priming, and discounting of trait inferences by situational information. The majority of these phenomena are illustrated with well-known experiments and simulated with an autoassociative network architecture with linear activation update and using the delta learning algorithm for adjusting the connection weights. All of the simulations successfully reproduced the empirical findings. Moreover, the proposed model is shown to be consistent with earlier algebraic models of impression formation (Anderson, 1981; Busemeyer, 1991; Hogarth and Einhorn, 1992). The discussion centers on how our model compares to other connectionist approaches to impression formation and how it may contribute to a more parsimonious and unified theory of person perception.

  4. Parabolic Free Boundary Price Formation Models Under Market Size Fluctuations

    KAUST Repository

    Markowich, Peter A.

    2016-10-04

    In this paper we propose an extension of the Lasry-Lions price formation model which includes uctuations of the numbers of buyers and vendors. We analyze the model in the case of deterministic and stochastic market size uctuations and present results on the long time asymptotic behavior and numerical evidence and conjectures on periodic, almost periodic, and stochastic uctuations. The numerical simulations extend the theoretical statements and give further insights into price formation dynamics.

  5. Enhanced Tunnelling Models for Child Universe Formation

    CERN Document Server

    Ansoldi, S; Shilon, I

    2015-01-01

    Starting from a recently proposed model that allows for an enhanced rate of child universe production under generic conditions, we elaborate on refinements that may allow for non-singular initial configurations. A possibility to treat both, the initial state and the tunnelling beyond the semiclassical level will also be introduced.

  6. PageRank model of opinion formation on Ulam networks

    CERN Document Server

    Chakhmakhchyan, L

    2013-01-01

    We consider a PageRank model of opinion formation on Ulam networks, generated by the intermittency map and the typical Chirikov map. The Ulam networks generated by these maps have certain similarities with such scale-free networks as the World Wide Web (WWW), showing an algebraic decay of the PageRank probability. We find that the opinion formation process on Ulam networks have certain similarities but also distinct features comparing to the WWW. We attribute these distinctions to internal differences in network structure of the Ulam and WWW networks. We also analyze the process of opinion formation in the frame of generalized Sznajd model which protects opinion of small communities.

  7. Mathematical modeling of biomass fuels formation process.

    Science.gov (United States)

    Gaska, Krzysztof; Wandrasz, Andrzej J

    2008-01-01

    The increasing demand for thermal and electric energy in many branches of industry and municipal management accounts for a drastic diminishing of natural resources (fossil fuels). Meanwhile, in numerous technical processes, a huge mass of wastes is produced. A segregated and converted combustible fraction of the wastes, with relatively high calorific value, may be used as a component of formed fuels. The utilization of the formed fuel components from segregated groups of waste in associated processes of co-combustion with conventional fuels causes significant savings resulting from partial replacement of fossil fuels, and reduction of environmental pollution resulting directly from the limitation of waste migration to the environment (soil, atmospheric air, surface and underground water). The realization of technological processes with the utilization of formed fuel in associated thermal systems should be qualified by technical criteria, which means that elementary processes as well as factors of sustainable development, from a global viewpoint, must not be disturbed. The utilization of post-process waste should be preceded by detailed technical, ecological and economic analyses. In order to optimize the mixing process of fuel components, a mathematical model of the forming process was created. The model is defined as a group of data structures which uniquely identify a real process and conversion of this data in algorithms based on a problem of linear programming. The paper also presents the optimization of parameters in the process of forming fuels using a modified simplex algorithm with a polynomial worktime. This model is a datum-point in the numerical modeling of real processes, allowing a precise determination of the optimal elementary composition of formed fuels components, with assumed constraints and decision variables of the task.

  8. FORMATION OF A INNOVATION REGIONAL CLUSTER MODEL

    Directory of Open Access Journals (Sweden)

    G. S. Merzlikina

    2015-01-01

    Full Text Available Summary. As a result of investigation of science and methodical approaches related problems of building and development of innovation clusters there were some issues in functional assignments of innovation and production clusters. Because of those issues, article’s authors differ conceptions of innovation cluster and production cluster, as they explain notion of innovation-production cluster. The main goal of this article is to reveal existing organizational issues in cluster building and its successful development. Based on regional clusters building analysis carried out there was typical practical structure of cluster members interaction revealed. This structure also have its cons, as following: absence cluster orientation to marketing environment, lack of members’ prolonged relations’ building and development system, along with ineffective management of information, financial and material streams within cluster, narrow competence difference and responsibility zones between cluster members, lack of transparence of cluster’s action, low environment changes adaptivity, hard to use cluster members’ intellectual property, and commercialization of hi-tech products. When all those issues listed above come together, it reduces life activity of existing models of innovative cluster-building along with practical opportunity of cluster realization. Because of that, authors offer an upgraded innovative-productive cluster building model with more efficient business processes management system, which includes advanced innovative cluster structure, competence matrix and subcluster responsibility zone. Suggested model differs from other ones by using unified innovative product development control center, which also controls production and marketing realization.

  9. A mathematical model of aortic aneurysm formation

    Science.gov (United States)

    Hao, Wenrui; Gong, Shihua; Wu, Shuonan; Xu, Jinchao; Go, Michael R.; Friedman, Avner; Zhu, Dai

    2017-01-01

    Abdominal aortic aneurysm (AAA) is a localized enlargement of the abdominal aorta, such that the diameter exceeds 3 cm. The natural history of AAA is progressive growth leading to rupture, an event that carries up to 90% risk of mortality. Hence there is a need to predict the growth of the diameter of the aorta based on the diameter of a patient’s aneurysm at initial screening and aided by non-invasive biomarkers. IL-6 is overexpressed in AAA and was suggested as a prognostic marker for the risk in AAA. The present paper develops a mathematical model which relates the growth of the abdominal aorta to the serum concentration of IL-6. Given the initial diameter of the aorta and the serum concentration of IL-6, the model predicts the growth of the diameter at subsequent times. Such a prediction can provide guidance to how closely the patient’s abdominal aorta should be monitored. The mathematical model is represented by a system of partial differential equations taking place in the aortic wall, where the media is assumed to have the constituency of an hyperelastic material. PMID:28212412

  10. Novel multiscale modeling tool applied to Pseudomonas aeruginosa biofilm formation.

    Science.gov (United States)

    Biggs, Matthew B; Papin, Jason A

    2013-01-01

    Multiscale modeling is used to represent biological systems with increasing frequency and success. Multiscale models are often hybrids of different modeling frameworks and programming languages. We present the MATLAB-NetLogo extension (MatNet) as a novel tool for multiscale modeling. We demonstrate the utility of the tool with a multiscale model of Pseudomonas aeruginosa biofilm formation that incorporates both an agent-based model (ABM) and constraint-based metabolic modeling. The hybrid model correctly recapitulates oxygen-limited biofilm metabolic activity and predicts increased growth rate via anaerobic respiration with the addition of nitrate to the growth media. In addition, a genome-wide survey of metabolic mutants and biofilm formation exemplifies the powerful analyses that are enabled by this computational modeling tool.

  11. Novel multiscale modeling tool applied to Pseudomonas aeruginosa biofilm formation.

    Directory of Open Access Journals (Sweden)

    Matthew B Biggs

    Full Text Available Multiscale modeling is used to represent biological systems with increasing frequency and success. Multiscale models are often hybrids of different modeling frameworks and programming languages. We present the MATLAB-NetLogo extension (MatNet as a novel tool for multiscale modeling. We demonstrate the utility of the tool with a multiscale model of Pseudomonas aeruginosa biofilm formation that incorporates both an agent-based model (ABM and constraint-based metabolic modeling. The hybrid model correctly recapitulates oxygen-limited biofilm metabolic activity and predicts increased growth rate via anaerobic respiration with the addition of nitrate to the growth media. In addition, a genome-wide survey of metabolic mutants and biofilm formation exemplifies the powerful analyses that are enabled by this computational modeling tool.

  12. ANALYTICAL CHIP FORMATION MODEL OF MICRO-END-MILLING

    Institute of Scientific and Technical Information of China (English)

    LI Chengfeng; LAI Xinmin; LI Hongtao; PENG Linfa; NI Jun

    2008-01-01

    A new analytical chip formation model is proposed for micro-end-milling operations. The model calculates an instantaneous uncut chip thickness by considering the combination of exact trochoidal trajectory of the tool tip and tool run-out, while the simplified circular trajectory and the neglected run-out create negligible change in conventional-scale chip formation models. Newton-Raphson iterative method is employed during the calculation to obtain quadratic convergence. The proposed approach allows the calculation of instantaneous uncut chip thickness to be done accurately and rapidly, and the prediction accuracy of this model is also verified by comparing the simulation results to experimental cutting forces.

  13. PageRank model of opinion formation on social networks

    Science.gov (United States)

    Kandiah, Vivek; Shepelyansky, Dima L.

    2012-11-01

    We propose the PageRank model of opinion formation and investigate its rich properties on real directed networks of the Universities of Cambridge and Oxford, LiveJournal, and Twitter. In this model, the opinion formation of linked electors is weighted with their PageRank probability. Such a probability is used by the Google search engine for ranking of web pages. We find that the society elite, corresponding to the top PageRank nodes, can impose its opinion on a significant fraction of the society. However, for a homogeneous distribution of two opinions, there exists a bistability range of opinions which depends on a conformist parameter characterizing the opinion formation. We find that the LiveJournal and Twitter networks have a stronger tendency to a totalitarian opinion formation than the university networks. We also analyze the Sznajd model generalized for scale-free networks with the weighted PageRank vote of electors.

  14. PageRank model of opinion formation on social networks

    CERN Document Server

    Kandiah, Vivek

    2012-01-01

    We propose the PageRank model of opinion formation and investigate its rich properties on real directed networks of Universities of Cambridge and Oxford, LiveJournal and Twitter. In this model the opinion formation of linked electors is weighted with their PageRank probability. We find that the society elite, corresponding to the top PageRank nodes, can impose its opinion to a significant fraction of the society. However, for a homogeneous distribution of two opinions there exists a bistability range of opinions which depends on a conformist parameter characterizing the opinion formation. We find that LiveJournal and Twitter networks have a stronger tendency to a totalitar opinion formation. We also analyze the Sznajd model generalized for scale-free networks with the weighted PageRank vote of electors.

  15. Modeling pollution formation in diesel engines

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N. [Lawrence Berkeley National Lab., CA (United States)

    1997-12-31

    Modeling combustion under conditions that prevail in Diesel engine presents a great challenge. Lawrence Berkeley National Laboratory has invested Laboratory Directed Research and Development Funds to accelerate progress in this area. Research has been concerned with building a chemical mechanism to interface with a high fidelity fluid code to describe aspects of Diesel combustion. The complexity of these models requires implementation on massively parallel machines. The author will describe his efforts concerned with building such a complex mechanism. He begins with C and CO{sub 2} chemistry and adds sequentially higher hydrocarbon chemistry, aromatic production chemistry, soot chemistry, and chemistry describing NO{sub x} production. The metrics against which this chemistry is evaluated are flame velocities, induction times, ignition delay times, flammability limits, flame structure measurements, and light scattering. He assembles a set of elementary reactions, kinetic rate coefficients, and thermochemistry. He modifies existing Sandia codes to be able to investigate the behavior of the mechanism in well-stirred reactors, plug flow reactors, and one-dimensional flames. The modified combustion code with a chemical mechanism at the appropriate level of complexity is then interfaced with the high fidelity fluids code. The fluids code is distinguished by its ability to solve the requisite partial differential equations with adaptively refined grids necessary to describe the strong variation in spatial scales in combustion.

  16. nIFTy Cosmology: Comparison of Galaxy Formation Models

    CERN Document Server

    Knebe, Alexander; Thomas, Peter A; Benson, Andrew; Blaizot, Jeremy; Bower, Richard; Carretero, Jorge; Castander, Francisco J; Cattaneo, Andrea; Cora, Sofia A; Croton, Darren J; Cui, Weiguang; Cunnama, Daniel; De Lucia, Gabriella; Devriendt, Julien E; Elahi, Pascal J; Font, Andreea; Fontanot, Fabio; Garcia-Bellido, Juan; Gargiulo, Ignacio D; Gonzalez-Perez, Violeta; Helly, John; Henriques, Bruno; Hirschmann, Michaela; Lee, Jaehyun; Mamon, Gary A; Monaco, Pierluigi; Onions, Julian; Padilla, Nelson D; Power, Chris; Pujol, Arnau; Skibba, Ramin A; Somerville, Rachel S; Srisawat, Chaichalit; Vega-Martinez, Cristian A; Yi, Sukyoung K

    2015-01-01

    We present a comparison of 14 galaxy formation models: 12 different semi-analytical models and 2 halo-occupation distribution models for galaxy formation based upon the same cosmological simulation and merger tree information derived from it. The participating codes have proven to be very successful in their own right but they have all been calibrated independently using various observational data sets, stellar models, and merger trees. In this paper we apply them without recalibration and this leads to a wide variety of predictions for the stellar mass function, specific star formation rates, stellar-to- halo mass ratios, and the abundance of orphan galaxies. The scatter is much larger than seen in previous comparison studies primarily because the codes have been used outside of their native environment within which they are well tested and calibrated. The purpose of the `nIFTy comparison of galaxy formation models' is to bring together as many different galaxy formation modellers as possible and to investig...

  17. Processes Affecting the Trihalomethane Concentrations Associated with the Third Injection, Storage, and Recovery Test at Lancaster, Antelope Valley, California, March 1998 through April 1999

    Science.gov (United States)

    Fram, Miranda S.; Bergamaschi, Brian A.; Goodwin, Kelly D.; Fujii, Roger; Clark, Jordan F.

    2003-01-01

    The formation and fate of trihalomethanes (THM) during the third injection, storage, and recovery test at Lancaster, Antelope Valley, California, were investigated as part of a program to assess the long-term feasibility of using injection, storage, and recovery as a water-supply method and as a way to reduce water-level declines and land-subsidence in the Antelope Valley. The program was conducted by the U.S. Geological Survey in cooperation with the Los Angeles County Department of Public Works and the Antelope Valley-East Kern Water Agency. The water used for injection, storage, and recovery must be disinfected before injection and thus contains THMs and other disinfection by-products. THMs (chloroform, CHCl3, bromodichloromethane, CHCl2Br, dibromochloromethane, CHClBr2, and bromoform, CHBr3) are formed by reaction between natural dissolved organic carbon that is present in water and chlorine that is added during the disinfection step of the drinking water treatment process. THMs are carcinogenic compounds, and their concentrations in drinking water are regulated by the U.S. Environmental Protection Agency. During previous cycles of the Lancaster program, extracted water still contained measurable concentrations of THMs long after continuous pumping had extracted a greater volume of water than had been injected. This raised concerns about the potential long-term effect of injection, storage, and recovery cycles on ground-water quality in Antelope Valley aquifers. The primary objectives of this investigation were to determine (1) what controlled continued THM formation in the aquifer after injection, (2) what caused of the persistence of THMs in the extracted water, even after long periods of pumping, (3) what controlled the decrease of THM concentrations during the extraction period, and (4) the potential for natural attenuation of THMs in the aquifer. Laboratory experiments on biodegradation of THMs in microcosms of aquifer materials indicate that aquifer

  18. Characterization of exoplanets from their formation I: Models of combined planet formation and evolution

    CERN Document Server

    Mordasini, C; Klahr, H; Henning, T

    2012-01-01

    A first characterization of many exoplanets has recently been achieved by the observational determination of their radius. For some planets, a measurement of the luminosity has also been possible, with many more directly imaged planets expected in the future. The statistical characterization of exoplanets through their mass-radius and mass-luminosity diagram is thus becoming possible. This is for planet formation and evolution theory of similar importance as the mass-distance diagram. Our aim in this and a companion paper is to extend our formation model into a coupled formation and evolution model. We want to calculate in a self-consistent way all basic characteristics (M,a,R,L) of a planet and use the model for population synthesis calculations. Here we show how we solve the structure equations describing the gaseous envelope not only during the early formation phase, but also during gas runaway accretion, and during the evolutionary phase at constant mass on Gyr timescales. We then study the in situ format...

  19. Optimal schooling formations using a potential flow model

    Science.gov (United States)

    Tchieu, Andrew; Gazzola, Mattia; de Brauer, Alexia; Koumoutsakos, Petros

    2012-11-01

    A self-propelled, two-dimensional, potential flow model for agent-based swimmers is used to examine how fluid coupling affects schooling formation. The potential flow model accounts for fluid-mediated interactions between swimmers. The model is extended to include individual agent actions by means of modifying the circulation of each swimmer. A reinforcement algorithm is applied to allow the swimmers to learn how to school in specified lattice formations. Lastly, schooling lattice configurations are optimized by combining reinforcement learning and evolutionary optimization to minimize total control effort and energy expenditure.

  20. Physical Models of Galaxy Formation in a Cosmological Framework

    Science.gov (United States)

    Somerville, Rachel S.; Davé, Romeel

    2015-08-01

    Modeling galaxy formation in a cosmological context presents one of the greatest challenges in astrophysics today due to the vast range of scales and numerous physical processes involved. Here we review the current status of models that employ two leading techniques to simulate the physics of galaxy formation: semianalytic models and numerical hydrodynamic simulations. We focus on a set of observational targets that describe the evolution of the global and structural properties of galaxies from roughly cosmic high noon (z â¼ 2-3) to the present. Although minor discrepancies remain, overall, models show remarkable convergence among different methods and make predictions that are in qualitative agreement with observations. Modelers have converged on a core set of physical processes that are critical for shaping galaxy properties. This core set includes cosmological accretion, strong stellar-driven winds that are more efficient at low masses, black hole feedback that preferentially suppresses star formation at high masses, and structural and morphological evolution through merging and environmental processes. However, all cosmological models currently adopt phenomenological implementations of many of these core processes, which must be tuned to observations. Many details of how these diverse processes interact within a hierarchical structure formation setting remain poorly understood. Emerging multiscale simulations are helping to bridge the gap between stellar and cosmological scales, placing models on a firmer, more physically grounded footing. Concurrently, upcoming telescope facilities will provide new challenges and constraints for models, particularly by directly constraining inflows and outflows through observations of gas in and around galaxies.

  1. Model for the formation energies of alanates and boranates

    NARCIS (Netherlands)

    van Setten, Michiel J.; de Wijs, Gilles A.; Brocks, G.

    2007-01-01

    We develop a simple model for the formation energies (FEs) of alkali and alkaline earth alanates and boranates, based upon ionic bonding between metal cations and AlH4- or BH4- anions. The FEs agree well with values obtained from first principles calculations and with experimental FEs. The model

  2. Structure formation in modified gravity models alternative to dark energy

    CERN Document Server

    Koyama, K

    2006-01-01

    We study structure formation in phenomenological models in which the Friedmann equation receives a correction of the form $H^{\\alpha}/r_c^{2-\\alpha}$, which realize an accelerated expansion without dark energy. In order to address structure formation in these model, we construct simple covariant gravitational equations which give the modified Friedmann equation with $\\alpha=2/n$ where $n$ is an integer. For $n=2$, the underlying theory is known as a 5D braneworld model (the DGP model). Thus the models interpolate between the DGP model ($n=2, \\alpha=1$) and the LCDM model in general relativity ($n \\to \\infty, \\alpha \\to 0$). Using the covariant equations, cosmological perturbations are analyzed. It is shown that in order to satisfy the Bianchi identity at a perturbative level, we need to introduce a correction term $E_{\\mu \

  3. Exposure to brominated trihalomethanes in water during pregnancy and micronuclei frequency in maternal and cord blood lymphocytes

    DEFF Research Database (Denmark)

    Stayner, Leslie Thomas; Pedersen, Marie; Patelarou, Evridiki;

    2014-01-01

    BACKGROUND: Water disinfection by-products have been associated with an increased cancer risk. Micronuclei (MN) frequency in lymphocytes is a marker of genomic damage and can predict adult cancer risk. OBJECTIVE: We evaluated maternal exposure to drinking water brominated trihalomethanes (BTHM) i...

  4. A geomechanical model of a sinkhole formation

    Science.gov (United States)

    Danchiv, Alexandru; Zamfirescu, Florian; Mocuta, Marius; Popa, Iulian; Zlibut, Alexandru; Huggenberger, Peter; Zechner, Eric; Dresmann, Horst; Scheidler, Stefan; Wiesmeier, Stefan

    2016-04-01

    On December 2010 a sinkhole was suddenly formed close to the eastern flank of Ocna-Mures salt dome. Soon after the collapse the sinkhole was filled with brine forming a salt lake called Plus Lake. The total volume of sinkhole of about 100000 m3 remained constant since February 2011. The Ocna Mures salt dome is situated on the western border of the Transylvanian basin (Romania) and has been exploited for a long time. The ceilings of some shallow mine chambers are now collapsed and filled with brine. Along the eastern flank of the salt dome there is a disturbed zone due to diapirism. Its presence is suggested by the strong fragmentation of rock in the boreholes drilled along the salt-sterile contact, as it resulted from the low values of RQD index. The sinkhole is probably due to a pressure increase along the diapir flank. The causes of this sudden increase of pressure are not well known. Most probably it is due to the damage of the tubing of a flank borehole as mentioned in a technical report of the exploiting company. The injected fresh water expelled through the breaches of the damaged borehole and, due to the high pressure flushed up the crushed material of the disturbed zone. In order to better understand the setting up of the Plus Lake joint research efforts were performed by teams from Bucharest and Basel Universities since 2013. For the geomechanical approach a numerical model was performed using the Flac 7.0 code. In a first stage the creep behavior of salt was analyzed considering a Norton creep law. It resulted that after 100 years the salt reached equilibrium, the creep could be neglected and in a first approximation mechanical equilibrium could be analyzed considering only an elasto-plastic behavior of both the salt and the sterile. For both the salt and the surrounding sedimentary rocks the Mohr-Coulomb criterion was considered. The properties of sterile rocks were estimated following the GSI system. Due to poor rock quality the strength parameters have

  5. 20th Century trends and budget implications of trihalomethanes and dihalomethanes inferred from North GRIP firn air

    Directory of Open Access Journals (Sweden)

    D. R. Worton

    2006-01-01

    Full Text Available Four trihalomethane (THM; CHCl3, CHBrCl2, CHBr2Cl and CHBr3 and two dihalomethane (DHM; CH2BrCl and CH2Br2 trace gases have been measured in air extracted from polar firn collected at the North Greenland Icecore Project (NGRIP site. CHCl3 was also measured in firn air from Devon Island (DI, Canada, Dronning Maud Land (DML, Antarctica and Dome Concordia (Dome C, Antarctica. All of these species are believed to be almost entirely of natural origin except for CHCl3 where anthropogenic sources have been reported to contribute ~10% to the global burden. A 2-D atmospheric model was run for CHCl3 using reported emission estimates to produce historical atmospheric trends at the three firn sites, which were then input into a firn diffusion model to produce concentration depth profiles that were compared against the measurements. The anthropogenic emissions were modified in order to give the best model fit to the firn data at NGRIP, Dome C and DML. As a result, the contribution of CHCl3 from anthropogenic sources, mainly from pulp and paper manufacture, to the total chloroform budget appears to have been considerably underestimated and was likely to have been close to ~40% at the maximum in atmospheric CHCl3 concentrations around 1990, declining to ~19% at the beginning of the 21st Century. We also show that the atmospheric burden of the brominated THM's in the northern hemisphere have increased over the 20th Century while CH2Br2 has remained constant over time implying that it is entirely of natural origin.

  6. Modeling Tools for Drilling, Reservoir Navigation, and Formation Evaluation

    Directory of Open Access Journals (Sweden)

    Sushant Dutta

    2012-06-01

    Full Text Available The oil and gas industry routinely uses borehole tools for measuring or logging rock and fluid properties of geologic formations to locate hydrocarbons and maximize their production. Pore fluids in formations of interest are usually hydrocarbons or water. Resistivity logging is based on the fact that oil and gas have a substantially higher resistivity than water. The first resistivity log was acquired in 1927, and resistivity logging is still the foremost measurement used for drilling and evaluation. However, the acquisition and interpretation of resistivity logging data has grown in complexity over the years. Resistivity logging tools operate in a wide range of frequencies (from DC to GHz and encounter extremely high (several orders of magnitude conductivity contrast between the metal mandrel of the tool and the geologic formation. Typical challenges include arbitrary angles of tool inclination, full tensor electric and magnetic field measurements, and interpretation of complicated anisotropic formation properties. These challenges combine to form some of the most intractable computational electromagnetic problems in the world. Reliable, fast, and convenient numerical modeling of logging tool responses is critical for tool design, sensor optimization, virtual prototyping, and log data inversion. This spectrum of applications necessitates both depth and breadth of modeling software—from blazing fast one-dimensional (1-D modeling codes to advanced threedimensional (3-D modeling software, and from in-house developed codes to commercial modeling packages. In this paper, with the help of several examples, we demonstrate our approach for using different modeling software to address different drilling and evaluation applications. In one example, fast 1-D modeling provides proactive geosteering information from a deep-reading azimuthal propagation resistivity measurement. In the second example, a 3-D model with multiple vertical resistive fractures

  7. Modeling Tools for Drilling, Reservoir Navigation, and Formation Evaluation

    Directory of Open Access Journals (Sweden)

    Sushant Dutta

    2012-06-01

    Full Text Available The oil and gas industry routinely uses borehole tools for measuring or logging rock and fluid properties of geologic formations to locate hydrocarbons and maximize their production. Pore fluids in formations of interest are usually hydrocarbons or water. Resistivity logging is based on the fact that oil and gas have a substantially higher resistivity than water. The first resistivity log was acquired in 1927, and resistivity logging is still the foremost measurement used for drilling and evaluation. However, the acquisition and interpretation of resistivity logging data has grown in complexity over the years. Resistivity logging tools operate in a wide range of frequencies (from DC to GHz and encounter extremely high (several orders of magnitude conductivity contrast between the metal mandrel of the tool and the geologic formation. Typical challenges include arbitrary angles of tool inclination, full tensor electric and magnetic field measurements, and interpretation of complicated anisotropic formation properties. These challenges combine to form some of the most intractable computational electromagnetic problems in the world. Reliable, fast, and convenient numerical modeling of logging tool responses is critical for tool design, sensor optimization, virtual prototyping, and log data inversion. This spectrum of applications necessitates both depth and breadth of modeling software—from blazing fast one-dimensional (1-D modeling codes to advanced threedimensional (3-D modeling software, and from in-house developed codes to commercial modeling packages. In this paper, with the help of several examples, we demonstrate our approach for using different modeling software to address different drilling and evaluation applications. In one example, fast 1-D modeling provides proactive geosteering information from a deep-reading azimuthal propagation resistivity measurement. In the second example, a 3-D model with multiple vertical resistive fractures

  8. Modelling new particle formation events in the South African savannah

    Energy Technology Data Exchange (ETDEWEB)

    Gierens, Rosa; Laakso, Lauri; Mogensen, Ditte; Vakkari, Ville; Buekes, Johan P.; Van Zyl, Pieter; Hakola, H.; Guenther, Alex B.; Pienaar, J. J.; Boy, Michael

    2014-05-28

    Africa is one of the less studied continents with respect to atmospheric aerosols. Savannahs are complex dynamic systems sensitive to climate and land-use changes, but the interaction of these systems with the atmosphere is not well understood. Atmospheric particles, called aerosols, affect the climate on regional and global scales, and are an important factor in air quality. In this study, measurements from a relatively clean savannah environment in South Africa were used to model new particle formation and growth. There already are some combined long-term measurements of trace gas concentrations together with aerosol and meteorological variables available, but to our knowledge this is the first detailed simulation that includes all the main processes relevant to particle formation. The results show that both of the particle formation mechanisms investigated overestimated the dependency of the formation rates on sulphuric acid. From the two particle formation mechanisms tested in this work, the approach that included low volatile organic compounds to the particle formation process was more accurate in describing the nucleation events than the approach that did not. To obtain a reliable estimate of aerosol concentration in simulations for larger scales, nucleation mechanisms would need to include organic compounds, at least in southern Africa. This work is the first step in developing a more comprehensive new particle formation model applicable to the unique environment in southern Africa. Such a model will assist in better understanding and predicting new particle formation – knowledge which could ultimately be used to mitigate impacts of climate change and air quality.

  9. Nonlinear flow model for well production in an underground formation

    Directory of Open Access Journals (Sweden)

    J. C. Guo

    2013-05-01

    Full Text Available Fluid flow in underground formations is a nonlinear process. In this article we modelled the nonlinear transient flow behaviour of well production in an underground formation. Based on Darcy's law and material balance equations, we used quadratic pressure gradients to deduce diffusion equations and discuss the origins of nonlinear flow issues. By introducing an effective-well-radius approach that considers skin factor, we established a nonlinear flow model for both gas and liquid (oil or water. The liquid flow model was solved using a semi-analytical method, while the gas flow model was solved using numerical simulations because the diffusion equation of gas flow is a stealth function of pressure. For liquid flow, a series of standard log-log type curves of pressure transients were plotted and nonlinear transient flow characteristics were analyzed. Qualitative and quantitative analyses were used to compare the solutions of the linear and nonlinear models. The effect of nonlinearity upon pressure transients should not be ignored. For gas flow, pressure transients were simulated and compared with oil flow under the same formation and well conditions, resulting in the conclusion that, under the same volume rate production, oil wells demand larger pressure drops than gas wells. Comparisons between theoretical data and field data show that nonlinear models will describe fluid flow in underground formations realistically and accurately.

  10. Modelling of compound nucleus formation in fusion of heavy nuclei

    CERN Document Server

    Díaz-Torres, A

    2004-01-01

    A new model that includes the time-dependent dynamics of the single-particle (s.p.) motion in conjunction with the macroscopic evolution of the system is proposed for describing the compound nucleus (CN) formation in fusion of heavy nuclei. The diabaticity initially keeps the entrance system around its contact configuration, but the gradual transition from the diabatic to the adiabatic potential energy surface (PES) leads to fusion or quasifission. Direct measurements of the probability for CN formation are crucial to discriminate between the current models.

  11. Dynamic Cell Formation based on Multi-objective Optimization Model

    Directory of Open Access Journals (Sweden)

    Guozhu Jia

    2013-08-01

    Full Text Available In this paper, a multi-objective model is proposed to address the dynamic cellular manufacturing (DCM formation problem. This model considers four conflicting objectives: relocation cost, machine utilization, material handling cost and maintenance cost. The model also considers the situation that some machines could be shared by more than one cell at the same period. A genetic algorithm is applied to get the solution of this mathematical model. Three numerical examples are simulated to evaluate the validity of this model.  

  12. Modeling of Fume Formation from Shielded Metal Arc Welding Process

    Science.gov (United States)

    Sivapirakasam, S. P.; Mohan, Sreejith; Santhosh Kumar, M. C.; Surianarayanan, M.

    2017-04-01

    In this study, a semi-empirical model of fume formation rate (FFR) from a shielded metal arc welding (SMAW) process has been developed. The model was developed for a DC electrode positive (DCEP) operation and involves the calculations of droplet temperature, surface area of the droplet, and partial vapor pressures of the constituents of the droplet to predict the FFR. The model was further extended for predicting FFR from nano-coated electrodes. The model estimates the FFR for Fe and Mn assuming constant proportion of other elements in the electrode. Fe FFR was overestimated, while Mn FFR was underestimated. The contribution of spatters and other mechanism in the arc responsible for fume formation were neglected. A good positive correlation was obtained between the predicted and experimental FFR values which highlighted the usefulness of the model.

  13. Physical Models of Galaxy Formation in a Cosmological Framework

    CERN Document Server

    Somerville, Rachel S

    2014-01-01

    Modeling galaxy formation in a cosmological context presents one of the greatest challenges in astrophysics today, due to the vast range of scales and numerous physical processes involved. Here we review the current status of models that employ two leading techniques to simulate the physics of galaxy formation: semi-analytic models and numerical hydrodynamic simulations. We focus on a set of observational targets that describe the evolution of the global and structural properties of galaxies from roughly Cosmic High Noon ($z\\sim 2-3$) to the present. Although minor discrepancies remain, overall, models show remarkable convergence between different methods and make predictions that are in qualitative agreement with observations. Modelers seem to have converged on a core set of physical processes that are critical for shaping galaxy properties. This core set includes cosmological accretion, strong stellar-driven winds that are more efficient at low masses, black hole feedback that preferentially suppresses star...

  14. Modeling of Fume Formation from Shielded Metal Arc Welding Process

    Science.gov (United States)

    Sivapirakasam, S. P.; Mohan, Sreejith; Santhosh Kumar, M. C.; Surianarayanan, M.

    2017-01-01

    In this study, a semi-empirical model of fume formation rate (FFR) from a shielded metal arc welding (SMAW) process has been developed. The model was developed for a DC electrode positive (DCEP) operation and involves the calculations of droplet temperature, surface area of the droplet, and partial vapor pressures of the constituents of the droplet to predict the FFR. The model was further extended for predicting FFR from nano-coated electrodes. The model estimates the FFR for Fe and Mn assuming constant proportion of other elements in the electrode. Fe FFR was overestimated, while Mn FFR was underestimated. The contribution of spatters and other mechanism in the arc responsible for fume formation were neglected. A good positive correlation was obtained between the predicted and experimental FFR values which highlighted the usefulness of the model.

  15. Galaxy formation history through hod model from euclid mock catalogs

    CERN Document Server

    Sakr, Ziad

    2015-01-01

    Halo Occupation Distribution (HOD) is a model giving the average number of galaxies in a dark matter halo, function of its mass and other intrinsic properties, like distance from halo center, luminosity and redshift of its constituting galaxies. It is believed that these parameters could also be related to the galaxy history of formation. We want to investigate more this relation in order to test and better refine this model. To do that, we extract HOD indicators from EUCLID mock catalogs for different luminosity cuts and for redshifts ranges going from 0.1 < z < 3.0. We study and interpret the trends of indicators function of these variations and tried to retrace galaxy formation history following the idea that galaxy evolution is the combination rather than the conflict of the two main proposed ideas nowadays: the older hierarchical mass merger driven paradigm and the recent downsizing star formation driven approach.

  16. Testing galaxy formation models with galaxy stellar mass functions

    Science.gov (United States)

    Lim, S. H.; Mo, H. J.; Lan, Ting-Wen; Ménard, Brice

    2016-10-01

    We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions (CSMF) of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. The observational data clearly prefer a model in which star formation in low-mass halos changes behavior at a characteristic redshift zc ˜ 2. There is also tentative evidence that this characteristic redshift depends on environment, becoming zc ˜ 4 in regions that eventually evolve into rich clusters of galaxies. The constrained model is used to understand how galaxies form and evolve in dark matter halos, and to make predictions for other statistical properties of the galaxy population, such as the stellar mass functions of galaxies at high z, the star formation and stellar mass assembly histories in dark matter halos. A comparison of our model predictions with those of other empirical models shows that different models can make vastly different predictions, even though all of them are tuned to match the observed stellar mass functions of galaxies.

  17. Testing galaxy formation models with galaxy stellar mass functions

    Science.gov (United States)

    Lim, S. H.; Mo, H. J.; Lan, T.-W.; Ménard, B.

    2017-01-01

    We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. The observational data clearly prefer a model in which star formation in low-mass haloes changes behaviour at a characteristic redshift zc ˜ 2. There is also tentative evidence that this characteristic redshift depends on environment, becoming zc ˜ 4 in regions that eventually evolve into rich clusters of galaxies. The constrained model is used to understand how galaxies form and evolve in dark matter haloes, and to make predictions for other statistical properties of the galaxy population, such as the stellar mass functions of galaxies at high z, the star formation, and stellar mass assembly histories in dark matter haloes. A comparison of our model predictions with those of other empirical models shows that different models can make vastly different predictions, even though all of them are tuned to match the observed stellar mass functions of galaxies.

  18. A local PDE model of aggregation formation in bacterial colonies

    Science.gov (United States)

    Chavy-Waddy, Paul-Christopher; Kolokolnikov, Theodore

    2016-10-01

    We study pattern formation in a model of cyanobacteria motion recently proposed by Galante, Wisen, Bhaya and Levy. By taking a continuum limit of their model, we derive a novel fourth-order nonlinear parabolic PDE equation that governs the behaviour of the model. This PDE is {{u}t}=-{{u}xx}-{{u}xxxx}+α {{≤ft(\\frac{{{u}x}{{u}xx}}{u}\\right)}x} . We then derive the instability thresholds for the onset of pattern formation. We also compute analytically the spatial profiles of the steady state aggregation density. These profiles are shown to be of the form \\text{sec}{{\\text{h}}p} where the exponent p is related to the parameters of the model. Full numerical simulations give a favorable comparison between the continuum and the underlying discrete system, and show that the aggregation profiles are stable above the critical threshold.

  19. Determination of the odor threshold concentrations of iodinated trihalomethanes in drinking water.

    Science.gov (United States)

    Cancho, B; Fabrellas, C; Diaz, A; Ventura, F; Galceran, M T

    2001-04-01

    Iodinated trihalomethanes (ITHMs) have been usually considered the disinfection byproducts suspected of causing medicinal odor episodes in treated water around the world. The odor threshold concentration (OTC) of mixed ITHMs (bromochloroiodo-, bromodiiodo-, chlorodiiodo-, dibromoiodo-, and dichloroiodomethane) which were previously synthesized -- because commercial standards are not available-- were determined by using two sensory techniques: flavor profile analysis (FPA), performed by an experienced panel trained in identifying odors and tastes in water; and gas chromatography coupled with olfactometry (GCO). FPA results gave a theoretical OTCs range from 0.1 to 8.9 microg/L and ITHMs were described as sweet, solvent, and medicinal products. The lowest experimental value (OTC(exp)) obtained from the six ITHMs, 0.03 microg/L, corresponded to iodoform.

  20. Removal of trihalomethanes from aqueous solution through armchair carbon nanotubes: a molecular dynamics study.

    Science.gov (United States)

    Azamat, Jafar; Khataee, Alireza; Joo, Sang Woo; Yin, Binfeng

    2015-04-01

    Molecular dynamics simulations were performed to investigate the removal of trihalomethanes (THMs) including CH3Cl, CH2Cl2 and CHCl3 from aqueous solutions by armchair carbon nanotubes (CNTs) under induced pressure. The studied system involved the armchair CNTs embedded between two graphene sheets with an aqueous solution of THMs in the simulation box. An external pressure was applied to the system along the z-axis of the simulation box. Six types of armchair CNTs with different diameter were used in this work, included (4,4), (5,5), (6,6), (7,7), (8,8) and (9,9) CNTs. The results of molecular dynamics simulation display that the armchair CNTs behave differently relative to THMs and water molecules. The permeation of THMs and water molecules through the armchair CNTs was dependent on the diameter of CNTs and the applied pressure.

  1. Adsorption thermodynamic and kinetic studies of trihalomethanes on multiwalled carbon nanotubes.

    Science.gov (United States)

    Lu, Chungsying; Chung, Yao-Lei; Chang, Kuan-Foo

    2006-11-16

    Multiwalled carbon nanotubes (MWCNTs) were purified by mixed HNO3/H2SO4 solution and were employed as adsorbents to study adsorption kinetics and thermodynamics of trihalomethanes (THMs) from chlorinated drinking water. The amount of THMs adsorbed onto CNTs decreased with a rise in temperature and high adsorption capacities were found at 5 and 15 degrees C. Under the same conditions, the purified CNTs possess two to three times more adsorption capacities of CHCl3, which accounts for a major portion of THMs in the chlorinated drinking water, than the commercially available PAC suggesting that CNTs are efficient adsorbents. The thermodynamic analysis revealed that the adsorption of THMs onto CNTs is exothermic and spontaneous.

  2. Stochastic resonance in the Weidlich model of public opinion formation

    Science.gov (United States)

    Babinec, Peter

    1997-02-01

    As a prototypical nonlinear sociological system we study the Weidlich model of public opinion formation. At an optimal value of the collective climate parameter (which plays the role of noise for this system) we have found a maximal value of signal-to-noise ratio and a largest amplification of a periodic external preference factor which are the characteristics of stochastic resonance.

  3. Star-forming galaxy models: Blending star formation into TREESPH

    Science.gov (United States)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  4. Business Models, transparency and efficient stock price formation

    DEFF Research Database (Denmark)

    Nielsen, Christian; Vali, Edward; Hvidberg, Rene

    of this, our hypothesis is that if it is possible to improve, simplify and define the way a company communicates its business model to the market, then it must be possible for the company to create a more efficient price formation of its share. To begin with, we decided to investigate whether transparency...

  5. Impression Formation and Modifiability: Testing a Theoretical Model

    Science.gov (United States)

    Mrug, Sylvie; Hoza, Betsy

    2007-01-01

    This study proposed and tested a developmental model of impression formation based on observed behavior, prior expectancies, and additional incongruent information. Participants were 51 kindergartners, 53 second graders, and 104 college students who provided trait and liking judgments after watching a child actor engage in behaviors from three…

  6. Modelling Adaptive Learning Behaviours for Consensus Formation in Human Societies

    Science.gov (United States)

    Yu, Chao; Tan, Guozhen; Lv, Hongtao; Wang, Zhen; Meng, Jun; Hao, Jianye; Ren, Fenghui

    2016-06-01

    Learning is an important capability of humans and plays a vital role in human society for forming beliefs and opinions. In this paper, we investigate how learning affects the dynamics of opinion formation in social networks. A novel learning model is proposed, in which agents can dynamically adapt their learning behaviours in order to facilitate the formation of consensus among them, and thus establish a consistent social norm in the whole population more efficiently. In the model, agents adapt their opinions through trail-and-error interactions with others. By exploiting historical interaction experience, a guiding opinion, which is considered to be the most successful opinion in the neighbourhood, can be generated based on the principle of evolutionary game theory. Then, depending on the consistency between its own opinion and the guiding opinion, a focal agent can realize whether its opinion complies with the social norm (i.e., the majority opinion that has been adopted) in the population, and adapt its behaviours accordingly. The highlight of the model lies in that it captures the essential features of people’s adaptive learning behaviours during the evolution and formation of opinions. Experimental results show that the proposed model can facilitate the formation of consensus among agents, and some critical factors such as size of opinion space and network topology can have significant influences on opinion dynamics.

  7. Formation models of cometary ices in protoplanetary disks

    NARCIS (Netherlands)

    Chaparro Molano, G.; Kamp, I.

    2014-01-01

    We set out to constrain the chemical conditions in the early Solar System by analyzing chemical evolution models of protoplanetary disks and comparing them to our current knowledge of Solar System bodies, such as comets. We propose that the region located at 10 AU≤r≤30 AU is ideal for the formation

  8. On a Boltzmann-type price formation model

    KAUST Repository

    Burger, Martin

    2013-06-26

    In this paper, we present a Boltzmann-type price formation model, which is motivated by a parabolic free boundary model for the evolution of price presented by Lasry and Lions in 2007. We discuss the mathematical analysis of the Boltzmann-type model and show that its solutions converge to solutions of the model by Lasry and Lions as the transaction rate tends to infinity. Furthermore, we analyse the behaviour of the initial layer on the fast time scale and illustrate the price dynamics with various numerical experiments. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

  9. Testing models of triggered star formation: theory and observation

    CERN Document Server

    Haworth, Thomas J; Acreman, David M

    2012-01-01

    One of the main reasons that triggered star formation is contentious is the failure to accurately link the observations with models in a detailed, quantitative, way. It is therefore critical to continuously test and improve the model details and methods with which comparisons to observations are made. We use a Monte Carlo radiation transport and hydrodynamics code TORUS to show that the diffuse radiation field has a significant impact on the outcome of radiatively driven implosion (RDI) models. We also calculate SEDs and synthetic images from the models to test observational diagnostics that are used to determine bright rimmed cloud conditions and search for signs of RDI.

  10. On pattern formation in the Gray-Scott model

    Institute of Scientific and Technical Information of China (English)

    Rui PENG; Ming-xin WANG

    2007-01-01

    In the paper, we investigate an elliptic system well-known as the Gray-Scott model and present some further results for positive solutions of this model. More precisely, we give the refined a priori estimates of positive solutions, and improve some previous results for the non-existence and existence of positive non-constant solutions as the parameters are varied, which imply some certain conditions where the pattern formation occurs or not.

  11. Star Formation in Isolated Disk Galaxies. I. Models and Star Formation Characteristics

    CERN Document Server

    Li, Y; Klessen, R S; Li, Yuexing; Low, Mordecai-Mark Mac; Klessen, Ralf S.

    2005-01-01

    We model star formation in a wide range of isolated disk galaxies composed of a dark matter halo and a disk of stars and isothermal gas, using a three-dimensional smoothed particle hydrodynamics code. Absorbing sink particles are used to directly measure the mass of gravitationally collapsing gas. They reach masses characteristic of stellar clusters. In this paper, we describe our galaxy models and numerical methods, followed by an investigation of the gravitational instability in these galaxies. Gravitational collapse forms star clusters with correlated positions and ages, as observed in the Large Magellanic Cloud. Gravitational instability alone acting in unperturbed galaxies appears sufficient to produce flocculent spiral arms, though not more organized patterns. Unstable galaxies show collapse in thin layers in the galactic plane; associated dust will form thin dust lanes in those galaxies, in agreement with observations. We find an exponential relationship between the global star formation timescale and ...

  12. A unified multi-wavelength model of galaxy formation

    CERN Document Server

    Lacey, Cedric G; Frenk, Carlos S; Benson, Andrew J; Bower, Richard G; Cole, Shaun; Gonzalez-Perez, Violeta; Helly, John C; Lagos, Claudia D P; Mitchell, Peter D

    2015-01-01

    We present a new version of the GALFORM semi-analytical model of galaxy formation. This brings together several previous developments of GALFORM into a single unified model, including a different initial mass function (IMF) in quiescent star formation and in starbursts, feedback from active galactic nuclei supressing gas cooling in massive halos, and a new empirical star formation law in galaxy disks based on their molecular gas content. In addition, we have updated the cosmology, introduced a more accurate treatment of dynamical friction acting on satellite galaxies, and updated the stellar population model. The new model is able to simultaneously explain both the observed evolution of the K-band luminosity function and stellar mass function, and the number counts and redshift distribution of sub-mm galaxies selected at 850 mu. This was not previously achieved by a single physical model within the LambdaCDM framework, but requires having an IMF in starbursts that is somewhat top-heavy. The new model is teste...

  13. Star formation in semi-analytic galaxy formation models with multiphase gas

    Science.gov (United States)

    Somerville, Rachel S.; Popping, Gergö; Trager, Scott C.

    2015-11-01

    We implement physically motivated recipes for partitioning cold gas into different phases (atomic, molecular, and ionized) in galaxies within semi-analytic models of galaxy formation based on cosmological merger trees. We then model the conversion of molecular gas into stars using empirical recipes motivated by recent observations. We explore the impact of these new recipes on the evolution of fundamental galaxy properties such as stellar mass, star formation rate (SFR), and gas and stellar phase metallicity. We present predictions for stellar mass functions, stellar mass versus SFR relations, and cold gas phase and stellar mass-metallicity relations for our fiducial models, from redshift z ˜ 6 to the present day. In addition we present predictions for the global SFR, mass assembly history, and cosmic enrichment history. We find that the predicted stellar properties of galaxies (stellar mass, SFR, metallicity) are remarkably insensitive to the details of the recipes used for partitioning gas into H I and H2. We see significant sensitivity to the recipes for H2 formation only in very low mass haloes (M_h ≲ 10^{10.5} M_{⊙}), which host galaxies with stellar masses m_* ≲ 10^8 M_{⊙}. The properties of low-mass galaxies are also quite insensitive to the details of the recipe used for converting H2 into stars, while the formation epoch of massive galaxies does depend on this significantly. We argue that this behaviour can be interpreted within the framework of a simple equilibrium model for galaxy evolution, in which the conversion of cold gas into stars is balanced on average by inflows and outflows.

  14. Trihalomethanes (THMs) precursor fractions removal by coagulation and adsorption for bio-treated municipal wastewater: Molecular weight, hydrophobicity/hydrophily and fluorescence.

    Science.gov (United States)

    Han, Qi; Yan, Han; Zhang, Feng; Xue, Nan; Wang, Yan; Chu, Yongbao; Gao, Baoyu

    2015-10-30

    Due to concerns over health risk of disinfection byproducts (DBPs), removal of trihalomethanes (THMs) precursor from bio-treated wastewater by coagulation and adsorption was investigated in this study. Ultrafiltration (UF) membranes and nonionic resins were applied to fractionate THMs precursor into various molecular weight (MW) fractions and hydrophobic/hydrophilic fractions. Characteristics of coagulated water and adsorbed water were evaluated by the three-dimensional excitation and emission matrix (3DEEM) fluorescence spectroscopy. Results showed that coagulation and adsorption were suitable for removing different hydrophobic/hydrophilic and fluorescent fractions. Coagulation decreased THMs concentration in hydrophobic acids (HoA) fraction from 59 μg/L to 39 μg/L, while the lowest THMs concentration (9 μg/L) in hydrophilic substances (HiS) fraction was obtained in adsorbed water. However, both coagulation and adsorption were ineffective for removing fractions with MWadsorption processes could reduce THMs formation, some specific THMs formation potential (STHMFP) in residual dissolved organic matter (DOM) fractions increased in this study. Hydrophobic acid and hydrophilic fractions increased after coagulation treatment, and low MW and hydrophobic fractions increased after adsorption treatment. In addition, active carbon adsorbed more organic matter than coagulant, but brominated disinfection byproducts (Br-DBPs) in adsorbed water turned to the major THMs species after chlorination. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Comparing models of star formation simulating observed interacting galaxies

    Science.gov (United States)

    Quiroga, L. F.; Muñoz-Cuartas, J. C.; Rodrigues, I.

    2017-07-01

    In this work, we make a comparison between different models of star formation to reproduce observed interacting galaxies. We use observational data to model the evolution of a pair of galaxies undergoing a minor merger. Minor mergers represent situations weakly deviated from the equilibrium configuration but significant changes in star fomation (SF) efficiency can take place, then, minor mergers provide an unique scene to study SF in galaxies in a realistic but yet simple way. Reproducing observed systems also give us the opportunity to compare the results of the simulations with observations, which at the end can be used as probes to characterize the models of SF implemented in the comparison. In this work we compare two different star formation recipes implemented in Gadget3 and GIZMO codes. Both codes share the same numerical background, and differences arise mainly in the star formation recipe they use. We use observations from Pico dos Días and GEMINI telescopes and show how we use observational data of the interacting pair in AM2229-735 to characterize the interacting pair. Later we use this information to simulate the evolution of the system to finally reproduce the observations: Mass distribution, morphology and main features of the merger-induced star formation burst. We show that both methods manage to reproduce roughly the star formation activity. We show, through a careful study, that resolution plays a major role in the reproducibility of the system. In that sense, star formation recipe implemented in GIZMO code has shown a more robust performance. Acknowledgements: This work is supported by Colciencias, Doctorado Nacional - 617 program.

  16. Testing galaxy formation models with galaxy stellar mass functions

    CERN Document Server

    Lim, Seunghwan; Lan, Ting-Wen; Ménard, Brice

    2016-01-01

    We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions (CSMF) of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. Among all the models considered, only the model of Lu et al. can match the observational data; all other models fail to reproduce the faint-end upturn seen in the observation. The CSMFs are used to update the halo-based empirical model of Lu et al., and the model parameters obtained are very similar to those inferred by Lu et al. from a completely different set of observational constraints. The observational data clearly prefer a model in which star formation in low-mass halos changes behavior at a characteristic redshift $z_c \\sim 2$. There is also tentative evidence that this characteristic redshift depends on environments, becoming $z_c \\sim 4$ in regions that eventually evolve into rich clusters of galaxies. The constrained model ...

  17. A vertex model of Drosophila ventral furrow formation.

    Directory of Open Access Journals (Sweden)

    Philipp Spahn

    Full Text Available Ventral furrow formation in Drosophila is an outstanding model system to study the mechanisms involved in large-scale tissue rearrangements. Ventral cells accumulate myosin at their apical sides and, while being tightly coupled to each other via apical adherens junctions, execute actomyosin contractions that lead to reduction of their apical cell surface. Thereby, a band of constricted cells along the ventral epithelium emerges which will form a tissue indentation along the ventral midline (the ventral furrow. Here we adopt a 2D vertex model to simulate ventral furrow formation in a surface view allowing easy comparison with confocal live-recordings. We show that in order to reproduce furrow morphology seen in vivo, a gradient of contractility must be assumed in the ventral epithelium which renders cells more contractile the closer they lie to the ventral midline. The model predicts previous experimental findings, such as the gain of eccentric morphology of constricting cells and an incremental fashion of apical cell area reduction. Analysis of the model suggests that this incremental area reduction is caused by the dynamical interplay of cell elasticity and stochastic contractility as well as by the opposing forces from contracting neighbour cells. We underpin results from the model through in vivo analysis of ventral furrow formation in wildtype and twi mutant embryos. Our results show that ventral furrow formation can be accomplished as a "tug-of-war" between stochastically contracting, mechanically coupled cells and may require less rigorous regulation than previously thought.For the developmental biologist it is a fascinating question how cells can coordinate major tissue movements during embryonic development. The so-called ventral furrow of the Drosophila embryo is a well-studied example of such a process when cells from a ventral band, spanning nearly the entire length of the embryo, undergo dramatic shape change by contracting their

  18. Vibration acceleration promotes bone formation in rodent models

    Science.gov (United States)

    Uchida, Ryohei; Nakata, Ken; Kawano, Fuminori; Yonetani, Yasukazu; Ogasawara, Issei; Nakai, Naoya; Mae, Tatsuo; Matsuo, Tomohiko; Tachibana, Yuta; Yokoi, Hiroyuki; Yoshikawa, Hideki

    2017-01-01

    All living tissues and cells on Earth are subject to gravitational acceleration, but no reports have verified whether acceleration mode influences bone formation and healing. Therefore, this study was to compare the effects of two acceleration modes, vibration and constant (centrifugal) accelerations, on bone formation and healing in the trunk using BMP 2-induced ectopic bone formation (EBF) mouse model and a rib fracture healing (RFH) rat model. Additionally, we tried to verify the difference in mechanism of effect on bone formation by accelerations between these two models. Three groups (low- and high-magnitude vibration and control-VA groups) were evaluated in the vibration acceleration study, and two groups (centrifuge acceleration and control-CA groups) were used in the constant acceleration study. In each model, the intervention was applied for ten minutes per day from three days after surgery for eleven days (EBF model) or nine days (RFH model). All animals were sacrificed the day after the intervention ended. In the EBF model, ectopic bone was evaluated by macroscopic and histological observations, wet weight, radiography and microfocus computed tomography (micro-CT). In the RFH model, whole fracture-repaired ribs were excised with removal of soft tissue, and evaluated radiologically and histologically. Ectopic bones in the low-magnitude group (EBF model) had significantly greater wet weight and were significantly larger (macroscopically and radiographically) than those in the other two groups, whereas the size and wet weight of ectopic bones in the centrifuge acceleration group showed no significant difference compared those in control-CA group. All ectopic bones showed calcified trabeculae and maturated bone marrow. Micro-CT showed that bone volume (BV) in the low-magnitude group of EBF model was significantly higher than those in the other two groups (3.1±1.2mm3 v.s. 1.8±1.2mm3 in high-magnitude group and 1.3±0.9mm3 in control-VA group), but BV in the

  19. Modelling the formation of organic particles in the atmosphere

    Science.gov (United States)

    Anttila, T.; Kerminen, V.-M.; Kulmala, M.; Laaksonen, A.; O'Dowd, C.

    2003-12-01

    A modelling study investigating the formation of organic particles from inorganic, thermodynamically stable clusters was carried out. A recently-developed theory, the so-called nano-Köhler theory, which describes a thermodynamic equilibrium between a nanometer-size cluster, water and water-soluble organic compound, was implemented in a dynamical model along with a treatment of the appropriate aerosol and gas-phase processes. The obtained results suggest that both gaseous sulphuric acid and organic vapours contribute to organic particle formation. The initial growth of freshly-nucleated clusters having a diameter around 1 nm is driven by condensation of gaseous sulphuric acid and by a lesser extent cluster self-coagulation. After the clusters have reached sizes of around 2 nm in diameter, low-volatile organic vapours start to condense spontaneously into the clusters, thereby accelerating their growth to detectable sizes. A shortage of gaseous sulphuric acid or organic vapours limit, or suppress altogether, the particle formation, since freshly-nucleated clusters are rapidly coagulated away by pre-existing particles. The obtained modelling results were applied to explaining the observed seasonal cycle in the number of aerosol formation events in a continental forest site.

  20. A physical model for cosmological simulations of galaxy formation

    CERN Document Server

    Vogelsberger, Mark; Sijacki, Debora; Torrey, Paul; Springel, Volker; Hernquist, Lars; ),

    2013-01-01

    We present a new comprehensive model of the physics of galaxy formation designed for large-scale hydrodynamical simulations of structure formation using the moving mesh code AREPO. Our model includes primordial and metal line cooling with self-shielding corrections, stellar evolution and feedback processes, gas recycling, chemical enrichment, a novel subgrid model for the metal loading of outflows, black hole (BH) seeding, BH growth and merging procedures, quasar- and radio-mode feedback, and a prescription for radiative electro-magnetic (EM) feedback from active galactic nuclei (AGN). Stellar feedback is realised through kinetic outflows. The scaling of the mass loading of galactic winds can be set to be either energy or momentum driven, or a mixture of both. The metal mass loading of outflows can be adjusted independently of the wind mass loading. This is required to simultaneously reproduce the stellar mass content of low mass haloes and their gas oxygen abundances. Radiative EM AGN feedback is implemented...

  1. Theoretical model for ultracold molecule formation via adaptive feedback control

    CERN Document Server

    Poschinger, U; Wester, R; Weidemüller, M; Koch, C P; Kosloff, R; Poschinger, Ulrich; Salzmann, Wenzel; Wester, Roland; Weidemueller, Matthias; Koch, Christiane P.; Kosloff, Ronnie

    2006-01-01

    We investigate pump-dump photoassociation of ultracold molecules with amplitude- and phase-modulated femtosecond laser pulses. For this purpose a perturbative model for the light-matter interaction is developed and combined with a genetic algorithm for adaptive feedback control of the laser pulse shapes. The model is applied to the formation of 85Rb2 molecules in a magneto-optical trap. We find for optimized pulse shapes an improvement for the formation of ground state molecules by more than a factor of 10 compared to unshaped pulses at the same pump-dump delay time, and by 40% compared to unshaped pulses at the respective optimal pump-dump delay time. Since our model yields directly the spectral amplitudes and phases of the optimized pulses, the results are directly applicable in pulse shaping experiments.

  2. Star formation in Herschel's Monsters versus semi-analytic models

    Science.gov (United States)

    Gruppioni, C.; Calura, F.; Pozzi, F.; Delvecchio, I.; Berta, S.; De Lucia, G.; Fontanot, F.; Franceschini, A.; Marchetti, L.; Menci, N.; Monaco, P.; Vaccari, M.

    2015-08-01

    We present a direct comparison between the observed star formation rate functions (SFRFs) and the state-of-the-art predictions of semi-analytic models (SAMs) of galaxy formation and evolution. We use the PACS Evolutionary Probe Survey and Herschel Multi-tiered Extragalactic Survey data sets in the COSMOS and GOODS-South fields, combined with broad-band photometry from UV to sub-mm, to obtain total (IR+UV) instantaneous star formation rates (SFRs) for individual Herschel galaxies up to z ˜ 4, subtracted of possible active galactic nucleus (AGN) contamination. The comparison with model predictions shows that SAMs broadly reproduce the observed SFRFs up to z ˜ 2, when the observational errors on the SFR are taken into account. However, all the models seem to underpredict the bright end of the SFRF at z ≳ 2. The cause of this underprediction could lie in an improper modelling of several model ingredients, like too strong (AGN or stellar) feedback in the brighter objects or too low fallback of gas, caused by weak feedback and outflows at earlier epochs.

  3. Formation of Novae and Coronae on Venus. Tectonophysical Modeling Using Gravity Models

    Science.gov (United States)

    Krassilnikov, A. S.

    2001-03-01

    Novae and coronae formation was simulated using caoutchouc as a model of lower ductile part of lithosphere and dry flour as a model of upper brittle part of it. Distribution and character of the deformational structures is described.

  4. Disk galaxy formation and evolution models up to intermediate redshifts

    CERN Document Server

    Firmani, C

    1999-01-01

    Making use of a seminumerical method we develop a scenario of disk galaxy formation and evolution in the framework of inflationary cold dark matter (CDM) cosmologies. Within the virializing dark matter halos, disks in centrifugal equilibrium are built-up and their galactic evolution is followed through an approach which considers the gravitational interactions among the galaxy components, the turbulence and energy balance of the ISM, the star formation (SF) process due to disk gravitational instabilities, the stellar evolution and the secular formation of a bulge. We find that the main properties and correlations of disk galaxies are determined by the mass, the hierarchical mass aggregation history and the primordial angular momentum. The models follow the same trends across the Hubble sequence than the observed galaxies. The predicted TF relation is in good agreement with the observations except for the standart CDM. While the slope of this relation remains almost constant up to intermediate redshifts, its z...

  5. Structure formation in the Lemaitre-Tolman model I

    CERN Document Server

    Krasinski, A; Krasinski, Andrzej; Hellaby, Charles

    2002-01-01

    Structure formation within the Lemaitre-Tolman model is investigated in a general manner. We seek models such that the initial density perturbation within a homogeneous background has a smaller mass than the structure into which it will develop, and the perturbation then accretes more mass during evolution. This is a generalisation of the approach taken by Bonnor in 1956. It is proved that any two spherically symmetric density profiles specified on any two constant time slices can be joined by a Lemaitre-Tolman evolution, and exact implicit formulae for the arbitrary functions that determine the resulting L-T model are obtained. Examples of the process are investigated numerically.

  6. Boundary-layer model of pattern formation in solidification

    Science.gov (United States)

    Ben-Jacob, E.; Goldenfeld, N.; Langer, J. S.; Schon, G.

    1984-01-01

    A model of pattern formation in crystal growth is proposed, and its analytic properties are investigated. The principal dynamical variables in this model are the curvature of the solidification front and the thickness (or heat content) of a thermal boundary layer, both taken to be functions of position along the interface. This model is mathematically much more tractable than the realistic, fully nonlocal version of the free-boundary problem, and still recaptures many of the features that seem essential for studying dendritic behavior, for example. Preliminary numerical solutions produce snowflakelike patterns similar to those seen in nature.

  7. Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

    DEFF Research Database (Denmark)

    Hansen, Kamilla Marie Speht; Willach, Sarah; Antoniou, Maria

    2012-01-01

    This study investigated the formation and predicted toxicity of different groups of disinfection byproducts (DBPs) from human exudates in relation to chlorination of pool water at different pH values. Specifically, the formation of the DBP groups trihalomethanes (THMs), haloacetic acids (HAAs...

  8. Modelling New Particle Formation Events in the South African Savannah

    Energy Technology Data Exchange (ETDEWEB)

    Gierens, Rosa; Laakso, Lauri; Mogensen, Ditte; Vakkari, Ville; Beukes, J. P.; Van Zyl, Pieter; Hakola, H.; Guenther, Alex B.; Pienaar, J. J.; Boy, Michael

    2014-01-01

    Africa is one of the less studied continents with respect to atmospheric aerosols. Savannahs are complex dynamic systems sensitive to climate and land-use changes, but the interaction with the atmosphere is not well understood. Atmospheric particles, aka aerosols, affect the climate on regional and global scale, and are an important factor in air quality. In this study measurements from a relatively clean savannah environment in South Africa were used to model new particle formation and growth. There are already some combined long-term measurements of trace gas concentrations together with aerosol and meteorological variables available, but to our knowledge this is the first time detailed simulations, that include all the main processes relevant to particle formation, were done. The results show that both investigated particle formation mechanisms overestimated the formation rates dependency on sulphuric acid. The approach including low volatile organic compounds to the particle formation process was more accurate in describing the nucleation events. To get reliable estimation of aerosol concentration in simulations for larger scales, nucleation mechanisms would need to include organic compounds, at least in southern Africa.

  9. Social Networks and Choice Set Formation in Discrete Choice Models

    Directory of Open Access Journals (Sweden)

    Bruno Wichmann

    2016-10-01

    Full Text Available The discrete choice literature has evolved from the analysis of a choice of a single item from a fixed choice set to the incorporation of a vast array of more complex representations of preferences and choice set formation processes into choice models. Modern discrete choice models include rich specifications of heterogeneity, multi-stage processing for choice set determination, dynamics, and other elements. However, discrete choice models still largely represent socially isolated choice processes —individuals are not affected by the preferences of choices of other individuals. There is a developing literature on the impact of social networks on preferences or the utility function in a random utility model but little examination of such processes for choice set formation. There is also emerging evidence in the marketplace of the influence of friends on choice sets and choices. In this paper we develop discrete choice models that incorporate formal social network structures into the choice set formation process in a two-stage random utility framework. We assess models where peers may affect not only the alternatives that individuals consider or include in their choice sets, but also consumption choices. We explore the properties of our models and evaluate the extent of “errors” in assessment of preferences, economic welfare measures and market shares if network effects are present, but are not accounted for in the econometric model. Our results shed light on the importance of the evaluation of peer or network effects on inclusion/exclusion of alternatives in a random utility choice framework.

  10. Star Formation and Metallicity Gradients in Semi-analytic Models of Disk Galaxy Formation

    CERN Document Server

    Fu, Jian; Huang, Meiling; Yates, Robert M; Moran, Sean; Heckman, Timothy M; Davé, Romeel; Guo, Qi

    2013-01-01

    We updated our radially-resolved SAMs of galaxy formation to track the radial distribution of stars, metals, atomic and molecular gas in galactic disks. The models are run on both MS and MS II using the recipes outlined in Fu et al. (2010) and Guo et al. (2011), with 3 main changes: (1) We adopt a simple star formation law where \\Sigma_SFR \\propto \\Sigma_H2. (2) We inject the heavy elements produced by SNe directly into the halo, instead of first mixing them with the disk cold gas. (3) We include radial gas inflows in disks using a model of the form v_inflow=alpha r. The average \\Sigma_H2 profiles in L_* galaxies strongly constrains the inflow velocities, favoring models where v_inflow ~ 7 km/s at r=10 kpc. The radial inflow model has little influence on the gas and stellar metallicity gradients in the outer disks. Gas metallicity gradients are affected much more strongly by the fraction of metals that are directly injected into the halo gas, rather than mixed with the interstellar cold gas. Metals ejected ou...

  11. Modeling for Stellar Feedback in Galaxy Formation Simulations

    Science.gov (United States)

    Núñez, Alejandro; Ostriker, Jeremiah P.; Naab, Thorsten; Oser, Ludwig; Hu, Chia-Yu; Choi, Ena

    2017-02-01

    Various heuristic approaches to model unresolved supernova (SN) feedback in galaxy formation simulations exist to reproduce the formation of spiral galaxies and the overall inefficient conversion of gas into stars. Some models, however, require resolution-dependent scalings. We present a subresolution model representing the three major phases of supernova blast wave evolution—free expansion, energy-conserving Sedov–Taylor, and momentum-conserving snowplow—with energy scalings adopted from high-resolution interstellar-medium simulations in both uniform and multiphase media. We allow for the effects of significantly enhanced SN remnant propagation in a multiphase medium with the cooling radius scaling with the hot volume fraction, {f}{hot}, as {(1-{f}{hot})}-4/5. We also include winds from young massive stars and AGB stars, Strömgren sphere gas heating by massive stars, and a mechanism that limits gas cooling that is driven by radiative recombination of dense H ii regions. We present initial tests for isolated Milky Way-like systems simulated with the Gadget-based code SPHgal with improved SPH prescription. Compared to pure thermal SN input, the model significantly suppresses star formation at early epochs, with star formation extended both in time and space in better accord with observations. Compared to models with pure thermal SN feedback, the age at which half the stellar mass is assembled increases by a factor of 2.4, and the mass-loading parameter and gas outflow rate from the galactic disk increase by a factor of 2. Simulation results are converged for a variation of two orders of magnitude in particle mass in the range (1.3–130) × 104 solar masses.

  12. A dynamic model for tumour growth and metastasis formation.

    Science.gov (United States)

    Haustein, Volker; Schumacher, Udo

    2012-07-05

    A simple and fast computational model to describe the dynamics of tumour growth and metastasis formation is presented. The model is based on the calculation of successive generations of tumour cells and enables one to describe biologically important entities like tumour volume, time point of 1st metastatic growth or number of metastatic colonies at a given time. The model entirely relies on the chronology of these successive events of the metastatic cascade. The simulation calculations were performed for two embedded growth models to describe the Gompertzian like growth behaviour of tumours. The initial training of the models was carried out using an analytical solution for the size distribution of metastases of a hepatocellular carcinoma. We then show the applicability of our models to clinical data from the Munich Cancer Registry. Growth and dissemination characteristics of metastatic cells originating from cells in the primary breast cancer can be modelled thus showing its ability to perform systematic analyses relevant for clinical breast cancer research and treatment. In particular, our calculations show that generally metastases formation has already been initiated before the primary can be detected clinically.

  13. A quantitative model for integrating landscape evolution and soil formation

    Science.gov (United States)

    Vanwalleghem, T.; Stockmann, U.; Minasny, B.; McBratney, Alex B.

    2013-06-01

    evolution is closely related to soil formation. Quantitative modeling of the dynamics of soils and landscapes should therefore be integrated. This paper presents a model, named Model for Integrated Landscape Evolution and Soil Development (MILESD), which describes the interaction between pedogenetic and geomorphic processes. This mechanistic model includes the most significant soil formation processes, ranging from weathering to clay translocation, and combines these with the lateral redistribution of soil particles through erosion and deposition. The model is spatially explicit and simulates the vertical variation in soil horizon depth as well as basic soil properties such as texture and organic matter content. In addition, sediment export and its properties are recorded. This model is applied to a 6.25 km2 area in the Werrikimbe National Park, Australia, simulating soil development over a period of 60,000 years. Comparison with field observations shows how the model accurately predicts trends in total soil thickness along a catena. Soil texture and bulk density are predicted reasonably well, with errors of the order of 10%, however, field observations show a much higher organic carbon content than predicted. At the landscape scale, different scenarios with varying erosion intensity result only in small changes of landscape-averaged soil thickness, while the response of the total organic carbon stored in the system is higher. Rates of sediment export show a highly nonlinear response to soil development stage and the presence of a threshold, corresponding to the depletion of the soil reservoir, beyond which sediment export drops significantly.

  14. Constraining Galaxy Formation Models with Dwarf Ellipticals in Clusters

    CERN Document Server

    Conselice, C J

    2005-01-01

    Recent observations demonstrate that dwarf elliptical (dE) galaxies in clusters, despite their faintness, are likely a critical galaxy type for understanding the processes behind galaxy formation. Dwarf ellipticals are the most common galaxy type, and are particularly abundant in rich galaxy clusters. The dwarf to giant ratio is in fact highest in rich clusters of galaxies, suggesting that cluster dEs do not form in groups that later merge to form clusters. Dwarf ellipticals are potentially the only galaxy type whose formation is sensitive to global, rather than local, environment. The dominant idea for explaining the formation of these systems, through Cold Dark Matter models, is that dEs form early and within their present environments. Recent results suggest that some dwarfs appear in clusters after the bulk of massive galaxies form, a scenario not predicted in standard hierarchical structure formation models. Many dEs have younger and more metal rich stellar populations than dwarfs in lower density enviro...

  15. Morphogenesis and pattern formation in biological systems experiments and models

    CERN Document Server

    Noji, Sumihare; Ueno, Naoto; Maini, Philip

    2003-01-01

    A central goal of current biology is to decode the mechanisms that underlie the processes of morphogenesis and pattern formation. Concerned with the analysis of those phenomena, this book covers a broad range of research fields, including developmental biology, molecular biology, plant morphogenesis, ecology, epidemiology, medicine, paleontology, evolutionary biology, mathematical biology, and computational biology. In Morphogenesis and Pattern Formation in Biological Systems: Experiments and Models, experimental and theoretical aspects of biology are integrated for the construction and investigation of models of complex processes. This collection of articles on the latest advances by leading researchers not only brings together work from a wide spectrum of disciplines, but also provides a stepping-stone to the creation of new areas of discovery.

  16. A Thermodynamic Model for Argon Plasma Kernel Formation

    Directory of Open Access Journals (Sweden)

    James Keck

    2010-11-01

    Full Text Available Plasma kernel formation of argon is studied experimentally and theoretically. The experiments have been performed in a constant volume cylindrical vessel located in a shadowgraph system. The experiments have been done in constant pressure. The energy of plasma is supplied by an ignition system through two electrodes located in the vessel. The experiments have been done with two different spark energies to study the effect of input energy on kernel growth and its properties. A thermodynamic model employing mass and energy balance was developed to predict the experimental data. The agreement between experiments and model prediction is very good. The effect of various parameters such as initial temperature, initial radius of the kernel, and the radiation energy loss have been investigated and it has been concluded that initial condition is very important on formation and expansion of the kernel.

  17. Vegetation pattern formation of a water-biomass model

    Science.gov (United States)

    Wang, Xiaoli; Wang, Wendi; Zhang, Guohong

    2017-01-01

    In this paper, a mathematical model with diffusion and cross-diffusion is proposed to describe the interaction between the vegetation and the soil water. Based on the view of Turing pattern, we discuss the conditions of the diffusion-induced instability and the cross-diffusion-induced instability of a homogenous uniform steady state. We find that either a fast diffusion speed of water or a great hydraulic diffusivity due to the suction of roots may drive the instability of the homogenous steady state. Furthermore, we find that both the rain-fall rate and the infiltration feedback parameter can induce the transitions among the vegetation state, pattern formation and bare soil state. It is also found that the "terrain slope" may cause the instability of the homogenous steady state and drive the formation of periodic stripe pattern. Consequently, the diversity of dryland vegetation in reality can be explained as a result of pattern solutions of the model.

  18. A panoptic model for planetesimal formation and pebble delivery

    CERN Document Server

    Krijt, Sebastiaan; Dominik, Carsten; Tielens, Alexander G G M

    2016-01-01

    The journey from dust particle to planetesimal involves physical processes acting on scales ranging from micrometers (the sticking and restructuring of aggregates) to hundreds of astronomical units (the size of the turbulent protoplanetary nebula). Considering these processes simultaneously is essential when studying planetesimal formation. We develop a novel, global, semi-analytical model for the evolution of the mass-dominating dust particles in a turbulent protoplanetary disk that takes into account the evolution of the dust surface density while preserving the essential characteristics of the porous coagulation process. This panoptic model is used to study the growth from submicron to planetesimal sizes in disks around Sun-like stars. For highly porous ices, unaffected by collisional fragmentation and erosion, rapid growth to planetesimal sizes is possible in a zone stretching out to ${\\sim}10\\mathrm{~AU}$ for massive disks. When porous coagulation is limited by erosive collisions, the formation of planet...

  19. Crystal Structure Representations for Machine Learning Models of Formation Energies

    CERN Document Server

    Faber, Felix; von Lilienfeld, O Anatole; Armiento, Rickard

    2015-01-01

    We introduce and evaluate a set of feature vector representations of crystal structures for machine learning (ML) models of formation energies of solids. ML models of atomization energies of organic molecules have been successful using a Coulomb matrix representation of the molecule. We consider three ways to generalize such representations to periodic systems: (i) a matrix where each element is related to the Ewald sum of the electrostatic interaction between two different atoms in the unit cell repeated over the lattice; (ii) an extended Coulomb-like matrix that takes into account a number of neighboring unit cells; and (iii) an Ansatz that mimics the periodicity and the basic features of the elements in the Ewald sum matrix by using a sine function of the crystal coordinates of the atoms. The representations are compared for a Laplacian kernel with Manhattan norm, trained to reproduce formation energies using a data set of 3938 crystal structures obtained from the Materials Project. For training sets consi...

  20. Some observational tests of a minimal galaxy formation model

    CERN Document Server

    Cohn, J D

    2016-01-01

    Dark matter simulations can serve as a basis for creating galaxy histories via the galaxy-dark matter connection. Here, one such model by Becker (2015) is implemented with several variations on three different dark matter simulations. Stellar mass and star formation rates are assigned to all simulation subhalos at all times, using subhalo mass gain to determine stellar mass gain. The observational properties of the resulting galaxy distributions are compared to each other and observations for a range of redshifts from 0-2. Although many of the galaxy distributions seem reasonable, there are noticeable differences as simulations, subhalo mass gain definitions, or subhalo mass definitions are altered, suggesting that the model should change as these properties are varied. Agreement with observations may improve by including redshift dependence in the added-by-hand random contribution to star formation rate. There appears to be an excess of faint quiescent galaxies as well (perhaps due in part to differing defin...

  1. Recommendation systems in the scope of opinion formation: a model

    CERN Document Server

    Blattner, Marcel

    2012-01-01

    Aggregated data in real world recommender applications often feature fat-tailed distributions of the number of times individual items have been rated or favored. We propose a model to simulate such data. The model is mainly based on social interactions and opinion formation taking place on a complex network with a given topology. A threshold mechanism is used to govern the decision making process that determines whether a user is or is not interested in an item. We demonstrate the validity of the model by fitting attendance distributions from different real data sets. The model is mathematically analyzed by investigating its master equation. Our approach provides an attempt to understand recommender system's data as a social process. The model can serve as a starting point to generate artificial data sets useful for testing and evaluating recommender systems.

  2. Integrated modeling of nitrogen oxides formation in diesel engines

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To account for the effects of both chemistry and flow turbulence,the present study proposes an integrated NO sub-model that combines the extended Zel'dovich mechanism and engine CFD computations to simulate the NO histories in a diesel engine.NOx sub-model parameters and pollutant formation mechanisms can be more easily investigated by solving the NOx sub-model.The new NO formation model incorporating the effects of hoth chemical kinetics and turbulent mixing was applied to simulate a diesel engine with a quiescent combustion chamber,and one with a re-entrant combustion chamber;the premise of the model being the reaction rate is mainlv determined by a kinetic timescale and a turbulent timescale.The results indicate that the predicted NO formulation from the new model agrees well with the measured data.As the utilization of fossil fuels continues to increase,the control of NOx emissions is a worldwide concern;and it is imperative to understand fully the NOx reaction processes in combustion systems.This technology has the Dotential to enhance the application of various combustion techniques used to reduce NOx emissions from practical combustion systems.

  3. An analytic model with critical behavior in black hole formation

    CERN Document Server

    Koike, T; Koike, Tatsuhiko; Mishima, Takashi

    1995-01-01

    A simple analytic model is presented which exhibits a critical behavior in black hole formation, namely, collapse of a thin shell coupled with outgoing null fluid. It is seen that the critical behavior is caused by the gravitational nonlinearity near the event horizon. We calculate the value of the critical exponent analytically and find that it is very dependent on the coupling constants of the system.

  4. Modelling Global Pattern Formations for Collaborative Learning Environments

    DEFF Research Database (Denmark)

    Grappiolo, Corrado; Cheong, Yun-Gyung; Khaled, Rilla;

    2012-01-01

    We present our research towards the design of a computational framework capable of modelling the formation and evolution of global patterns (i.e. group structures) in a population of social individuals. The framework is intended to be used in collaborative environments, e.g. social serious games...... and computer simulations of artificial societies. The theoretical basis of our research, together with current state of the art and future work, are briefly introduced....

  5. Modelling sea ice formation in the Terra Nova Bay polynya

    Science.gov (United States)

    Sansiviero, M.; Morales Maqueda, M. Á.; Fusco, G.; Aulicino, G.; Flocco, D.; Budillon, G.

    2017-02-01

    Antarctic sea ice is constantly exported from the shore by strong near surface winds that open leads and large polynyas in the pack ice. The latter, known as wind-driven polynyas, are responsible for significant water mass modification due to the high salt flux into the ocean associated with enhanced ice growth. In this article, we focus on the wind-driven Terra Nova Bay (TNB) polynya, in the western Ross Sea. Brine rejected during sea ice formation processes that occur in the TNB polynya densifies the water column leading to the formation of the most characteristic water mass of the Ross Sea, the High Salinity Shelf Water (HSSW). This water mass, in turn, takes part in the formation of Antarctic Bottom Water (AABW), the densest water mass of the world ocean, which plays a major role in the global meridional overturning circulation, thus affecting the global climate system. A simple coupled sea ice-ocean model has been developed to simulate the seasonal cycle of sea ice formation and export within a polynya. The sea ice model accounts for both thermal and mechanical ice processes. The oceanic circulation is described by a one-and-a-half layer, reduced gravity model. The domain resolution is 1 km × 1 km, which is sufficient to represent the salient features of the coastline geometry, notably the Drygalski Ice Tongue. The model is forced by a combination of Era Interim reanalysis and in-situ data from automatic weather stations, and also by a climatological oceanic dataset developed from in situ hydrographic observations. The sensitivity of the polynya to the atmospheric forcing is well reproduced by the model when atmospheric in situ measurements are combined with reanalysis data. Merging the two datasets allows us to capture in detail the strength and the spatial distribution of the katabatic winds that often drive the opening of the polynya. The model resolves fairly accurately the sea ice drift and sea ice production rates in the TNB polynya, leading to

  6. The Relationship between MX [3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone], Routinely Monitored Trihalomethanes, and Other Characteristics in Drinking Water in a Long-Term Survey.

    Science.gov (United States)

    Smith, Rachel B; Bennett, James E; Rantakokko, Panu; Martinez, David; Nieuwenhuijsen, Mark J; Toledano, Mireille B

    2015-06-01

    MX (3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) is a drinking water disinfection byproduct (DBP). It is a potent mutagen and is of concern to public health. Data on MX levels in drinking water, especially in the UK, are limited. Our aim was to investigate factors associated with variability of MX concentrations at the tap, and to evaluate if routinely measured trihalomethanes (THMs) are an appropriate proxy measure for MX. We conducted quarterly water sampling at consumers' taps in eight water supply zones in and around Bradford, UK, between 2007 and 2010. We collected 79 samples which were analyzed for MX using GC-HRMS. Other parameters such as pH, temperature, UV-absorbance and free chlorine were measured concurrently, and total THMs were modeled from regulatory monitoring data. To our knowledge this is the longest MX measurement survey undertaken to date. Concentrations of MX varied between 8.9 and 45.5 ng/L with a median of 21.3 ng/L. MX demonstrated clear seasonality with concentrations peaking in late summer/early fall. Multivariate regression showed that MX levels were associated with total trihalomethanes, UV-absorbance and pH. However, the relationship between TTHM and MX may not be sufficiently consistent across time and location for TTHM to be used as a proxy measure for MX in exposure assessment.

  7. Core formation, evolution, and convection - A geophysical model

    Science.gov (United States)

    Ruff, L.; Anderson, D. L.

    1980-01-01

    A model for the formation and evolution of the earth's core, which provides an adequate energy source for maintaining the geodynamo, is proposed. A modified inhomogeneous accretion model is proposed which leads to initial iron and refractory enrichment at the center of the planet. The probable heat source for melting of the core is the decay of Al-26. The refractory material is emplaced irregularly in the lowermost mantle with uranium and thorium serving as a long-lived heat source. Fluid motions in the core are driven by the differential heating from above and the resulting cyclonic motions may be the source of the geodynamo.

  8. Core formation, evolution, and convection: A geophysical model

    Science.gov (United States)

    Ruff, L.; Anderson, D. L.

    1978-01-01

    A model is proposed for the formation and evolution of the Earth's core which provides an adequate energy source for maintaining the geodynamo. A modified inhomogeneous accretion model is proposed which leads to initial iron and refractory enrichment at the center of the planet. The probable heat source for melting of the core is the decay of Al. The refractory material is emplaced irregularly in the lowermost mantle with uranium and thorium serving as a long lived heat source. Fluid motions in the core are driven by the differential heating from above and the resulting cyclonic motions may be the source of the geodynamo.

  9. The use of technology in a model of formative assessment

    Directory of Open Access Journals (Sweden)

    Alfonsa García López

    2016-06-01

    Full Text Available This work describes a formative assessment model for the Mathematical Analysis course taken by engineering students. It includes online questionnaires with feedback, a portfolio with weekly assignments, exams involving the use of mathematical software and a project to be completed in small groups of two or three students. The model has been perfected since 2009, and during the 2014-15 academic year the creation of a pilot online learning community was added. Based on Google+, it has been used for a peer assessment experiment involving student projects, among other uses.

  10. Model for Formation of Dunes at the North Martian Pole

    Institute of Scientific and Technical Information of China (English)

    ZHU Jie; CHEN Chu-Xin

    2010-01-01

    @@ The Mars Global Surveyor Mars Orbiter Camera(MOC)took images of a series of strange horseshoe-shaped dunes at the North Martian pole in 2004.These dunes would be formed due to the strong Martian winds whose pattern is different from that on the Earth.We study the cause of the formation of these dunes and make a model for them.In this model,wind speed near the north Martian pole can be evaluated based on the shape of the dunes.We also estimate the surpassing speed of dunes of different sizes.

  11. The formation of adipocere in model aquatic environments.

    Science.gov (United States)

    Stuart, B H; Notter, S J; Dent, B; Selvalatchmanan, J; Fu, S

    2016-01-01

    An examination of the chemistry of adipocere formation in aquatic systems provides insight into how environmental factors affect the decomposition processes of human remains. Gas chromatography–mass spectrometry (GC-MS) and inductively coupled plasma–mass spectrometry (ICPMS) have been employed to monitor the changes to the chemistry of adipocere formed in aquatic environments used to model seawater, river and chlorinated water systems. Seawater was shown to inhibit adipocere formation, and a distinctively different elemental composition was produced in this environment due to the high concentrations of salts. By comparison, river water has been shown to accelerate the formation of adipocere. Chlorinated water appears to significantly enhance adipocere formation, based on a comparison with established fatty acid concentration values. However, a competing reaction to form chlorohydrins in chlorinated water is believed to be responsible for the unusual findings in this environment. The application of the chemical characterization of adipocere to an understanding of how this particular decomposition product forms in different water environments has been demonstrated, and there is potential to utilise this approach to identify the environment in which a body has been immersed.

  12. Modelling of frost formation and growth on microstuctured surface

    Science.gov (United States)

    Muntaha, Md. Ali; Haider, Md. Mushfique; Rahman, Md. Ashiqur

    2016-07-01

    Frost formation on heat exchangers is an undesirable phenomenon often encountered in different applications where the cold surface with a temperature below freezing point of water is exposed to humid air. The formation of frost on the heat transfer surface results in an increase in pressure drop and reduction in heat transfer, resulting in a reduction of the system efficiency. Many factors, including the temperature and moisture content of air, cold plate temperature, surface wettability etc., are known to affect frost formation and growth. In our present study, a model for frost growth on rectangular, periodic microgroove surfaces for a range of microgroove dimension (ten to hundreds of micron) is presented. The mathematical model is developed analytically by solving the governing heat and mass transfer equations with appropriate boundary conditions using the EES (Engineering Equation Solver) software. For temperature, a convective boundary condition at frost-air interface and a fixed cold plate surface temperature is used. Instead of considering the saturation or super-saturation models, density gradient at the surface is obtained by considering experimentally-found specified heat flux. The effect of surface wettability is incorporated by considering the distribution of condensed water droplets at the early stage of frost formation. Thickness, density and thermal conductivity of frost layer on the micro-grooved surfaces are found to vary with the dimension of the grooves. The variation of density and thickness of the frost layer on these micro-grooved surfaces under natural convection is numerally determined for a range of plate temperature and air temperature conditions and is compared with experimental results found in the open literature.

  13. Optimization Model of Subjectivity Formation in Educational Environment

    Directory of Open Access Journals (Sweden)

    I. V. Vorobyeva

    2012-01-01

    Full Text Available The paper is devoted to the issues of the subjectivity formation in the educational environment, as well as the application of the relative psycho-technologies of facilitation and optimization of the process. The correlation between the notions of personality and subject is considered, though their scientific and semantic distinctions still remain obscure. In the frame- work of the competence approach, based on the concepts of accepted in education and psychology functional paradigm, the above terms are widely spread. Therefore, finding out the specifics of their genesis is both relevant and up-to-date. The authors conclude that the personality and subject are not equivalents, the same as the personality growth is not equivalent to the subjectivity formation. By means of theoretical analyses of the domestic approaches to the phenomena of subject and subjectivity, the four-stage process of the subject-genesis in the educa- tional environment has been modeled. At every stage of subjectivity formation in the particular conditions, it is necessary to use psycho-technologies relating to the actual targets of subject-genesis, which makes it possible to optimize the educational process in the context of the competence approach. The level-based description of the given process is proposed along with the model of its optimization in implementing the target psycho-technologies. The model can be applied both as a methodology basis for the complex development and optimization of psycho-pedagogical facilitation of the sub- jectivity formation, and as a theoretical basis for the educational strategy development and correction in a particular educational establishment. 

  14. Optimization Model of Subjectivity Formation in Educational Environment

    Directory of Open Access Journals (Sweden)

    I. V. Vorobyeva

    2015-02-01

    Full Text Available The paper is devoted to the issues of the subjectivity formation in the educational environment, as well as the application of the relative psycho-technologies of facilitation and optimization of the process. The correlation between the notions of personality and subject is considered, though their scientific and semantic distinctions still remain obscure. In the frame- work of the competence approach, based on the concepts of accepted in education and psychology functional paradigm, the above terms are widely spread. Therefore, finding out the specifics of their genesis is both relevant and up-to-date. The authors conclude that the personality and subject are not equivalents, the same as the personality growth is not equivalent to the subjectivity formation. By means of theoretical analyses of the domestic approaches to the phenomena of subject and subjectivity, the four-stage process of the subject-genesis in the educa- tional environment has been modeled. At every stage of subjectivity formation in the particular conditions, it is necessary to use psycho-technologies relating to the actual targets of subject-genesis, which makes it possible to optimize the educational process in the context of the competence approach. The level-based description of the given process is proposed along with the model of its optimization in implementing the target psycho-technologies. The model can be applied both as a methodology basis for the complex development and optimization of psycho-pedagogical facilitation of the sub- jectivity formation, and as a theoretical basis for the educational strategy development and correction in a particular educational establishment. 

  15. Some observational tests of a minimal galaxy formation model

    Science.gov (United States)

    Cohn, J. D.

    2017-04-01

    Dark matter simulations can serve as a basis for creating galaxy histories via the galaxy-dark matter connection. Here, one such model by Becker is implemented with several variations on three different dark matter simulations. Stellar mass and star formation rates are assigned to all simulation subhaloes at all times, using subhalo mass gain to determine stellar mass gain. The observational properties of the resulting galaxy distributions are compared to each other and observations for a range of redshifts from 0 to 2. Although many of the galaxy distributions seem reasonable, there are noticeable differences as simulations, subhalo mass gain definitions or subhalo mass definitions are altered, suggesting that the model should change as these properties are varied. Agreement with observations may improve by including redshift dependence in the added-by-hand random contribution to star formation rate. There appears to be an excess of faint quiescent galaxies as well (perhaps due in part to differing definitions of quiescence). The ensemble of galaxy formation histories for these models tend to have more scatter around their average histories (for a fixed final stellar mass) than the two more predictive and elaborate semi-analytic models of Guo et al. and Henriques et al., and require more basis fluctuations (using principal component analysis) to capture 90 per cent of the scatter around their average histories. The codes to plot model predictions (in some cases alongside observational data) are publicly available to test other mock catalogues at https://github.com/jdcphysics/validation/. Information on how to use these codes is in Appendix A.

  16. Numerical modeling of batch formation in waste incineration plants

    Directory of Open Access Journals (Sweden)

    Obroučka Karel

    2015-03-01

    Full Text Available The aim of this paper is a mathematical description of algorithm for controlled assembly of incinerated batch of waste. The basis for formation of batch is selected parameters of incinerated waste as its calorific value or content of pollutants or the combination of both. The numerical model will allow, based on selected criteria, to compile batch of wastes which continuously follows the previous batch, which is a prerequisite for optimized operation of incinerator. The model was prepared as for waste storage in containers, as well as for waste storage in continuously refilled boxes. The mathematical model was developed into the computer program and its functionality was verified either by practical measurements or by numerical simulations. The proposed model can be used in incinerators for hazardous and municipal waste.

  17. A formative model for student nurse development and evaluation

    Directory of Open Access Journals (Sweden)

    A. S. van der Merwe

    1996-05-01

    Full Text Available Preparing student nurses for the profession is a complex task for nurse educators; especially when dealing with the development of personal and interpersonal skills, qualities and values held in high esteem by the nursing profession and the community they serve. These researchers developed a model for formative evaluation of students by using the principles of inductive and deductive reasoning. This model was implemented in clinical practice situations and evaluated for its usefulness. It seems that the model enhanced the standards of nursing care because it had a positive effect on the behaviour of students and they were better motivated; the model also improved interpersonal relationships and communication between practising nurses and students.

  18. The high redshift galaxy population in hierarchical galaxy formation models

    CERN Document Server

    Kitzbichler, M G; Kitzbichler, Manfred G.; White, Simon D. M.

    2006-01-01

    We compare observations of the high redshift galaxy population to the predictions of the galaxy formation model of Croton et al. (2006). This model, implemented on the Millennium Simulation of the concordance LCDM cosmogony, introduces "radio mode" feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the low redshift galaxy population. Here we compare the predictions of this same model to the observed counts and redshift distributions of faint galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment gives moderately good agreement with most of the data, although the predicted abundance of relatively massive (~M*) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this mo...

  19. Formation of Toxic Iodinated Disinfection By-Products from Compounds Used in Medical Imaging

    Science.gov (United States)

    Iodinated X-ray contrast media (ICM) were investigated as a source of iodine in the formation of iodo-trihalomethane (iodo-THM) and iodo-acid disinfection byproducts (DBPs), both of which are highly genotoxic and/or cytotoxic in mammalian cells. ICM are widely used at medical cen...

  20. Application of hollow fiber liquid phase microextraction for simultaneous determination of regulated and emerging iodinated trihalomethanes in drinking water.

    Science.gov (United States)

    Domínguez-Tello, A; Arias-Borrego, A; García-Barrera, T; Gómez-Ariza, J L

    2015-07-10

    Trihalomethanes (THMs) are regulated disinfection by-products (DBPs) most commonly analyzed in quality control water supply due to their harmful effects on health. However, few data exist about the content of emerging iodo-trihalomethanes (I-THMs) which are present in drinking water at very low concentrations (in the order of ngL(-1)). For this reason a two-phase hollow fiber liquid phase microextraction method for the simultaneous determination of four regulated trihalomethanes and six emerging iodo-trihalomethanes using GC-μECD and GC-MS with detection limits in the range of few ngL(-1) has been developed. A central composite design was used to optimize conditions for simultaneous extraction. The best extraction recovery was obtained with 19.2min at 27.1°C and 900rpm, without salt addition, using a supported hollow fiber membrane of 10.5cm (0.6mm id) and 1-octanol as acceptor phase. The limits of detection for the regulated THMs and I-THMs were 3-44ngL(-1) and 1-3ngL(-1), respectively. The calibration curves showed good linearity (R(2)>0.995) and good repeatibility (3-22%). The relative recoveries in water were between 96.5% and 105.2%. The method was applied for the simultaneous determination of trihalomethanes in supply water samples from seven water distribution systems (WDS) in the Huelva area, located at the southwest Spain, which use different water-treatment processes. The highest concentrations of I-THMs, particularly CHBrClI and CHCl2I, were detected in water treated with advanced treatment process using pre-ozonation, however these compounds were not detected or decreased along distribution system. In the samples of treated water with conventional treatment, using pre-oxidation by permanganate and distribution network, CHCl2I, CHBrClI, CHClI2, CHBrI2 and CHI3 were detected at very low concentrations (1-18ngL(-1)). Finally, in water samples from underground origin without oxidation treatment, in which only disinfection with sodium hypochlorite was

  1. Volatile particles formation during PartEmis: a modelling study

    Directory of Open Access Journals (Sweden)

    X. Vancassel

    2004-01-01

    Full Text Available A modelling study of the formation of volatile particles in a combustor exhaust has been carried out in the frame of the PartEmis European project. A kinetic model has been used in order to investigate nucleation efficiency of the H2O-H2SO4 binary mixture in the sampling system. A value for the fraction of the fuel sulphur S(IV converted into S(VI has been indirectly deduced from comparisons between model results and measurements. In the present study, ranges between roughly 2.5% and 6%, depending on the combustor settings and on the value assumed for the parameter describing sulphuric acid wall losses. Soot particles hygroscopicity has also been investigated as their activation is a key parameter for contrail formation. Growth factors of monodisperse particles exposed to high relative humidity (95% have been calculated and compared with experimental results. The modelling study confirms that the growth factor increases as the soot particle size decreases.

  2. Fractal model for simulation of frost formation and growth

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A planar fractal model for simulation of frost formation and growth was proposed based on diffusion limited aggregation(DLA)model and the computational simulation was carried out in this paper.By changing the times of program running circulation and the ratio of random particles generated,the simulation figures were gained under different conditions.A microscope is used to observe the shape and structure of frost layer and a digital camera with high resolution is used to record the pattern of frost layer at different time.Through comparing the simulation figures with the experimental images,we find that the simulation results agree well with the experimental images in shape and the fractal dimension of simulation figures is nearly equal to that of experimental images.The results indicate that it is reasonable to represent frost layer growth time with the program circulation times and to simulate the frost layer density variation during its growth process by reducing the random particle generation probability.The feasibility of using the suggested model to simulate the process of frost formation and growth was justified.The insufficiencies and its causes of this fractal model are also discussed.

  3. Dynamic Model Visualizing the Process of Viral Plaque Formation

    Directory of Open Access Journals (Sweden)

    Boriana Marintcheva

    2012-09-01

    Full Text Available In Microbiology and Virology courses, viral plaques are often presented to students as the way one can visualize viruses/bacteriophages. While students generally grasp the idea that counting plaques is essentially the same as counting viruses in their sample (assuming that one virus entering the cell is sufficient for productive infection, the process of plaque formation itself remains largely obscure. Many students fail to appreciate that viral plaques are actually a “laboratory-made” phenomenon allowing us to observe and study the growth of lytic viruses. The latter often presents a challenge for the interpretation of experimental data related to viral growth and drug discovery using plaque reduction assay. The hands-on model described here creates an opportunity for students to experience the process of viral plaque formation while engaging multiple senses and creating a lasting impression.  

  4. Mass Distribution and Bar Formation in Growing Disk Galaxy Models

    CERN Document Server

    Berrier, Joel C

    2016-01-01

    We report idealized simulations that mimic the growth of galaxy disks embedded in responsive halos and bulges. The disks manifested an almost overwhelming tendency to form strong bars that we found very difficult to prevent. We found that fresh bars formed in growing disks after we had destroyed the original, indicating that bar formation also afflicts continued galaxy evolution, and not just the early stages of disk formation. This behavior raises still more insistently the previously unsolved question of how some galaxies avoid bars. Since our simulations included only collisionless star and halo particles, our findings may apply to gas-poor galaxies only; however the conundrum persists for the substantial unbarred fraction of those galaxies. Our original objective was to study how internal dynamics rearranged the distribution of mass in the disk as a generalization of our earlier study with rigid spherical components. With difficulty, we were able to construct some models that were not strongly influenced ...

  5. Modeling biogenic gas bubbles formation and migration in coarse sand

    Science.gov (United States)

    Ye, S.

    2011-12-01

    Shujun Ye Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; sjye@nju.edu.cn Brent E. Sleep Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4 CANADA; sleep@ecf.utoronto.ca Methane gas generation in porous media was investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. Macroscopic invasion percolation (MIP) at near pore scale[Glass, et al., 2001; Kueper and McWhorter, 1992]was used to model gas bubbles growth in porous media. The nonwetting phase migration pathway can be yielded directly by MIP. MIP was adopted to simulate the expansion, fragmentation, and mobilization of gas clusters in the cell. The production of gas, and gas phash saturations were simulated by a continuum model - compositional simulator (COMPSIM) [Sleep and Sykes, 1993]. So a combination of a continuum model and a MIP model was used to simulate the formation, fragmentation and migration of biogenic gas bubbles. Key words: biogenic gas; two dimensional; porous media; MIP; COMPSIM

  6. Model of Layered Weld Formation Under Narrow Gap Pulse Welding

    Science.gov (United States)

    Krampit, A. G.

    2016-04-01

    The model parameters of narrow gap pulse welding can be divided into input, internal and output ones. The breadth of gap, that is, clearance breadth between upright edges is one of key parameters securing high quality of a weld joint. The paper presents theoretical outcomes for the model of layered weld formation under narrow gap pulse welding. Based on these studies is developed model of processes, which occur in the weld pool under pulse grove welding. It comprises the scheme of liquid metal motion in the weld pool, scheme of fusion with the side edge and in the bottom part, and the scheme of welding current impulse effect on the structure of a weld joint.

  7. Testing protostellar disk formation models with ALMA observations

    CERN Document Server

    Harsono, Daniel; Bruderer, Simon; Li, Zhi-Yun; Jorgensen, Jes

    2015-01-01

    Abridged: Recent simulations have explored different ways to form accretion disks around low-mass stars. We aim to present observables to differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded young stellar objects and infer their masses and sizes. Two 3D magnetohydrodynamics (MHD) formation simulations and 2D semi-analytical model are studied. The dust temperature structure is determined through continuum radiative transfer RADMC3D modelling. A simple temperature dependent CO abundance structure is adopted and synthetic spectrally resolved submm rotational molecular lines up to $J_{\\rm u} = 10$ are simulated. All models predict similar compact components in continuum if observed at the spatial resolutions of 0.5-1$"$ (70-140 AU) typical of the observations to date. A spatial resolution of $\\sim$14 AU and high dynamic range ($> 1000$) are required to differentiate between RSD and pseudo-disk in the continuum. The peak-position velocity diagrams indicate that the...

  8. A case study in modeling a nuclear formation evaluation sub

    Energy Technology Data Exchange (ETDEWEB)

    Locke, S. (Teleco Oilfield Services, Inc., Middletown, CT (United States))

    1992-08-01

    This paper reports that constructing an accurate Monte Carlo representation of a complex nuclear formation evaluation tool requires careful matching of computed values to the results of laboratory experiments. The availability of only finite computing resources forces restraint in the step by step addition of complexity to the model. Once confidence in the model has been established, it can be used to predict tool response to many situations not reproducible in a laboratory. High temperatures, high pressures, and pore fluids composed of liquid-gas mixtures are typical of conditions encountered in real oil wells that are difficult to reproduce in a laboratory. Tool design and the effects of design modifications can also be evaluated efficiently using the model.

  9. Modeling of microporosity formation in A356 aluminum alloy casting

    Science.gov (United States)

    Zhu, J. D.; Cockcroft, S. L.; Maijer, D. M.

    2006-03-01

    A numerical model for predicting microporosity formation in aluminum castings has been developed, which describes the redistribution of hydrogen between solid and liquid phases, the transport of hydrogen in liquid by diffusion, and Darcy flow in the mushy zone. For simulating the nucleation of hydrogen pores, the initial pore radius is assumed to be a function of the secondary dendrite arm spacing, whereas pore growth is based on the assumption that hydrogen activity within the pore and the liquid are in equilibrium. One of the key features of the model is that it uses a two-stage approach for porosity prediction. In the first stage, the volume fraction of porosity is calculated based on the reduced pressure, whereas, in the second stage, at fractions solid greater than the liquid encapsulation point, the fraction porosity is calculated based on the volume of liquid trapped within the continuous solid network, which is estimated using a correlation based on the Niyama parameter. The porosity model is used in conjunction with a thermal model solved using the commercial finite-element package ABAQUS. The parameters influencing the formation of microporosity are discussed including a means to describe the supersaturation of hydrogen necessary for pore nucleation. The model has been applied to examine the evolution of porosity in a series of experimental samples cast using unmodified A356 in which the initial hydrogen content was varied from 0.048 to 0.137 (cc/100 g). A comparison between the model predictions and the experimental measurements indicates good agreement in terms of the variation in porosity with distance from the chill and the variation resulting from initial hydrogen content.

  10. Cosmological Structure Formation in Decaying Dark Matter Models

    CERN Document Server

    Cheng, Dalong; Tang, Jiayu

    2015-01-01

    The standard cold dark matter (CDM) model predicts too many and too dense small structures. We consider an alternative model that the dark matter undergoes two-body decays with cosmological lifetime $\\tau$ into only one type of massive daughters with non-relativistic recoil velocity $V_k$. This decaying dark matter model (DDM) can suppress the structure formation below its free-streaming scale at time scale comparable to $\\tau$. Comparing with warm dark matter (WDM), DDM can better reduce the small structures while being consistent with high redshfit observations. We study the cosmological structure formation in DDM by performing self-consistent N-body simulations and point out that cosmological simulations are necessary to understand the DDM structures especially on non-linear scales. We propose empirical fitting functions for the DDM suppression of the mass function and the mass-concentration relation, which depend on the decay parameters lifetime $\\tau$ and recoil velocity $V_k$, and redshift. The fitting ...

  11. Formats

    Directory of Open Access Journals (Sweden)

    Gehmann, Ulrich

    2012-03-01

    Full Text Available In the following, a new conceptual framework for investigating nowadays’ “technical” phenomena shall be introduced, that of formats. The thesis is that processes of formatting account for our recent conditions of life, and will do so in the very next future. It are processes whose foundations have been laid in modernity and which will further unfold for the time being. These processes are embedded in the format of the value chain, a circumstance making them resilient to change. In addition, they are resilient in themselves since forming interconnected systems of reciprocal causal circuits.Which leads to an overall situation that our entire “Lebenswelt” became formatted to an extent we don’t fully realize, even influencing our very percep-tion of it.

  12. Micro versus macro solid phase extraction for monitoring water contaminants: a preliminary study using trihalomethanes.

    Science.gov (United States)

    Alexandrou, Lydon D; Spencer, Michelle J S; Morrison, Paul D; Meehan, Barry J; Jones, Oliver A H

    2015-04-15

    Solid phase extraction is one of the most commonly used pre-concentration and cleanup steps in environmental science. However, traditional methods need electrically powered pumps, can use large volumes of solvent (if multiple samples are run), and require several hours to filter a sample. Additionally, if the cartridge is open to the air volatile compounds may be lost and sample integrity compromised. In contrast, micro cartridge based solid phase extraction can be completed in less than 2 min by hand, uses only microlitres of solvent and provides comparable concentration factors to established methods. It is also an enclosed system so volatile components are not lost. The sample can also be eluted directly into a detector (e.g. a mass spectrometer) if required. However, the technology is new and has not been much used for environmental analysis. In this study we compare traditional (macro) and the new micro solid phase extraction for the analysis of four common volatile trihalomethanes (trichloromethane, bromodichloromethane, dibromochloromethane and tribromomethane). The results demonstrate that micro solid phase extraction is faster and cheaper than traditional methods with similar recovery rates for the target compounds. This method shows potential for further development in a range of applications.

  13. Simplified Modeling of Tropospheric Ozone Formation Considering Alternative Fuels Using

    Directory of Open Access Journals (Sweden)

    Leonardo Aragão Ferreira da Silva

    2014-07-01

    Full Text Available Brazilian cities have been constantly exposed to air quality episodes of high ozone concentrations (O3 . Known for not be emitted directly into the environment, O3 is a result of several chemical reactions of other pollutants emitted to atmosphere. The growth of vehicle fleet and government incentives for using alternative fuels like ethanol and Compressed Natural Gas (CNG are changing the Brazilian Metropolitan Areas in terms of acetaldehyde and formaldehyde emissions, Volatile Organic Compounds (VOC's present in the atmosphere and known to act on the kinetics of ozone. Driven by high concentrations of tropospheric ozone in urban/industry centers and its implications for environment and population health, the target of this work is understand the kinetics of ozone formation through the creation of a mathematical model in FORTRAN 90, describing a system of coupled ordinary differential equations able to represent a simplified mechanism of photochemical reactions in the Brazilian Metropolitan Area. Evaluating the concentration results of each pollutant were possible to observe the precursor’s influence on tropospheric ozone formation, which seasons were more conducive to this one and which are the influences of weather conditions on formation of photochemical smog.

  14. Cell Competition Drives the Formation of Metastatic Tumors in a Drosophila Model of Epithelial Tumor Formation

    DEFF Research Database (Denmark)

    Eichenlaub, Teresa; Cohen, Stephen M; Herranz, Héctor

    2016-01-01

    Cell competition is a homeostatic process in which proliferating cells compete for survival. Elimination of otherwise normal healthy cells through competition is important during development and has recently been shown to contribute to maintaining tissue health during organismal aging. The mechan......Cell competition is a homeostatic process in which proliferating cells compete for survival. Elimination of otherwise normal healthy cells through competition is important during development and has recently been shown to contribute to maintaining tissue health during organismal aging....... The mechanisms that allow for ongoing cell competition during adult life could, in principle, contribute to tumorigenesis. However, direct evidence supporting this hypothesis has been lacking. Here, we provide evidence that cell competition drives tumor formation in a Drosophila model of epithelial cancer. Cells...... of the Septin family protein Peanut. Cytokinesis failure due to downregulation of Peanut is required for tumorigenesis. This study provides evidence that the cellular mechanisms that drive cell competition during normal tissue growth can be co-opted to drive tumor formation and metastasis. Analogous mechanisms...

  15. Diffusion model of the formation of growth microdefects: A new approach to defect formation in crystals (Review)

    Science.gov (United States)

    Talanin, V. I.; Talanin, I. E.

    2016-03-01

    Theoretical studies of defect formation in semiconductor silicon play an important role in the creation of breakthrough ideas for next-generation technologies. A brief comparative analysis of modern theoretical approaches to the description of interaction of point defects and formation of the initial defect structure of dislocation-free silicon single crystals has been carried out. Foundations of the diffusion model of the formation of structural imperfections during the silicon growth have been presented. It has been shown that the diffusion model is based on high-temperature precipitation of impurities. The model of high-temperature precipitation of impurities describes processes of nucleation, growth, and coalescence of impurities during cooling of a crystal from 1683 to 300 K. It has been demonstrated that the diffusion model of defect formation provides a unified approach to the formation of a defect structure beginning with the crystal growth to the production of devices. The possibilities of using the diffusion model of defect formation for other semiconductor crystals and metals have been discussed. It has been shown that the diffusion model of defect formation is a platform for multifunctional solution of many key problems in modern solid state physics. Fundamentals of practical application of the diffusion model for engineering of defects in crystals with modern information technologies have been considered. An algorithm has been proposed for the calculation and analysis of a defect structure of crystals.

  16. A Model of Digital Payment Infrastructure Formation and Development

    DEFF Research Database (Denmark)

    Staykova, Kalina; Damsgaard, Jan

    2014-01-01

    in the regulatory environment and combining it with the disruptive and innovative nature of the mobile phone, the result is a market that is rapidly transforming from well-established structure into a state of flux. We build a model to understand and explain this transformation of the digital payment infrastructure....... The model captures the formation and development of the digital payment infrastructure with a particular emphasis on the regulator´s and innovator’s perspective. It consists of four stages characterized by slow incremental change which are followed by short and rapid bursts of discontinuity. Each stage...... is portrayed by its evolutionary dynamics, the nature of the payment platform, the legal implications, the level of competition, and what drives the discontinuity....

  17. Galacticus: A Semi-Analytic Model of Galaxy Formation

    Science.gov (United States)

    Benson, Andrew

    2011-08-01

    Galacticus is designed to solve the physics involved in the formation of galaxies within the current standard cosmological framework. It is of a type of model known as “semi-analytic” in which the numerous complex non-linear physics involved are solved using a combination of analytic approximations and empirical calibrations from more detailed, numerical solutions. Models of this type aim to begin with the initial state of the Universe (specified shortly after the Big Bang) and apply physical principles to determine the properties of galaxies in the Universe at later times, including the present day. Typical properties computed include the mass of stars and gas in each galaxy, broad structural properties (e.g. radii, rotation speeds, geometrical shape etc.), dark matter and black hole contents, and observable quantities such as luminosities, chemical composition etc.

  18. Formation, characterization and mathematical modeling of the aerobic granular sludge

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Bing-Jie [Queensland Univ., Brisbane, QLD (Australia). Advanced Water Management Centre

    2013-07-01

    Reports on successful aerobic granulation of sludge in pilot-scale reactor for treatment of low-strength municipal wastewater and identifies the key factors responsible for this process. Develops comprehensive models for sludge granulation, microbial interactions and microbial products formation to provide insights into the dynamics of all the soluble and solid components in aerobic granular sludge system. Demonstrates accelerated start-up and optimization of the anaerobic ammonia oxidation process by seeding the reactor with aerobic granules. Aerobic granular sludge technology will play an important role as an innovative technology alternative to the present activated sludge process in industrial and municipal wastewater treatment in the near future. Intended to fill the gaps in the studies of aerobic granular sludge, this thesis comprehensively investigates the formation, characterization and mathematical modeling of aerobic granular sludge, through integrating the process engineering tools and advanced molecular microbiology. The research results of this thesis contributed significantly to the advance of understanding and optimization of the bacterial granulation processes, the next generation of technology for cost-effective biological wastewater treatment.

  19. Numerical study on the perception-based network formation model

    CERN Document Server

    Jo, Hang-Hyun

    2015-01-01

    In order to understand the evolution of social networks in terms of perception-based strategic link formation, we numerically study a perception-based network formation model. Here each individual is assumed to have his/her own perception of the actual network, and use it to decide whether to create a link to other individual. An individual with the least perception accuracy can benefit from updating his/her perception using that of the most accurate individual via a new link. This benefit is compared to the cost of linking in decision making. Once a new link is created, it affects the accuracies of other individuals' perceptions, leading to a further evolution of the actual network. The initial actual network and initial perceptions are modeled by Erd\\H{o}s-R\\'enyi random networks but with different linking probabilities. Then the stable link density of the actual network is found to show discontinuous transitions or jumps according to the cost of linking. The effect of initial conditions on the complexity o...

  20. A Model of Filamentous Cyanobacteria Leading to Reticulate Pattern Formation

    Directory of Open Access Journals (Sweden)

    Carlos Tamulonis

    2014-09-01

    Full Text Available The filamentous cyanobacterium, Pseudanabaena, has been shown to produce reticulate patterns that are thought to be the result of its gliding motility. Similar fossilized structures found in the geological record constitute some of the earliest signs of life on Earth. It is difficult to tie these fossils, which are billions of years old, directly to the specific microorganisms that built them. Identifying the physicochemical conditions and microorganism properties that lead microbial mats to form macroscopic structures can lead to a better understanding of the conditions on Earth at the dawn of life. In this article, a cell-based model is used to simulate the formation of reticulate patterns in cultures of Pseudanabaena. A minimal system of long and flexible trichomes capable of gliding motility is shown to be sufficient to produce stable patterns consisting of a network of streams. Varying model parameters indicate that systems with little to no cohesion, high trichome density and persistent movement are conducive to reticulate pattern formation, in conformance with experimental observations.

  1. A General Shear-Dependent Model for Thrombus Formation.

    Science.gov (United States)

    Yazdani, Alireza; Li, He; Humphrey, Jay D; Karniadakis, George Em

    2017-01-01

    Modeling the transport, activation, and adhesion of platelets is crucial in predicting thrombus formation and growth following a thrombotic event in normal or pathological conditions. We propose a shear-dependent platelet adhesive model based on the Morse potential that is calibrated by existing in vivo and in vitro experimental data and can be used over a wide range of flow shear rates ([Formula: see text]). We introduce an Eulerian-Lagrangian model where hemodynamics is solved on a fixed Eulerian grid, while platelets are tracked using a Lagrangian framework. A force coupling method is introduced for bidirectional coupling of platelet motion with blood flow. Further, we couple the calibrated platelet aggregation model with a tissue-factor/contact pathway coagulation cascade, representing the relevant biology of thrombin generation and the subsequent fibrin deposition. The range of shear rates covered by the proposed model encompass venous and arterial thrombosis, ranging from low-shear-rate conditions in abdominal aortic aneurysms and thoracic aortic dissections to thrombosis in stenotic arteries following plaque rupture, where local shear rates are extremely high.

  2. A model for core formation in the early Earth

    Science.gov (United States)

    Jones, J. H.; Drake, M. J.

    1985-01-01

    Two basic types exogenous models were proposed to account for siderophile and chalcophile element abundances in the Earth's upper mantle. The first model requires that the Earth be depleted in volatiles and that, after a core formation event which extracted the most siderophile elements into the core, additional noble siderophile elements (Pt, Ir, Au) were added as a late veneer and mixed into the mantle. The second model postulates a reduced Earth with approximately CI elemental abundances in which a primary core forming event depleted all siderophile elements in the mantle. The plausibility of models which require fine scale mixing of chondritic material into the upper mantle is analyzed. Mixing in liquids is more efficient, but large degrees of silicate partial melting will facilitate the separation of magma from residual solids. Any external events affecting the upper mantle of the Earth should also be evident in the Moon; but siderophile and chalcophile element abundance patterns inferred for the mantles of the Earth and Moon differ. There appear to be significant physical difficulties associated with chondritic veneer models.

  3. Regional modeling of SOA formation under consideration of HOMs

    Science.gov (United States)

    Gatzsche, Kathrin; Iinuma, Yoshiteru; Tilgner, Andreas; Berndt, Torsten; Poulain, Laurent; Wolke, Ralf

    2017-04-01

    Secondary organic aerosol (SOA) is the major burden of the atmospheric organic particulate matter with about 140 - 910 TgC/yr (Hallquist et al., 2009). SOA particles are formed via the oxidation of volatile organic carbons (VOCs), where the volatility of the VOCs is lowered. Therefore, gaseous compounds can either nucleate to form new particles or condense on existing particles. The framework of SOA formation under natural conditions is very complex, because there are a variety of gas-phase precursors, atmospheric degradation pathways and formed oxidation products. Up to now, atmospheric models underpredict the SOA mass. Therefore, improved regional scale model implementations are necessary to achieve a better agreement between model predictions and field measurements. Recently, highly oxidized multifunctional organic compounds (HOMs) were found in the gas phase from laboratory and field studies (Jokinen et al., 2015, Mutzel et al., 2015, Berndt et al., 2016a,b). From box model studies, it is known that HOMs are important for the early aerosol growth, however they are not yet considered in mechanisms applied in regional models. The present study utilizes the state-of-the-art multiscale model system COSMO-MUSCAT (Wolke et al., 2012), which is qualified for process studies in local and regional areas. The established model system was enhanced by a kinetic partitioning approach (Zaveri et al., 2014) for the gas-to-particle transfer of oxidized VOCs. The framework of the partitioning approach and the gas-phase mechanism were tested in a box model and evaluated with chamber studies, before implementing in the 3D model system COSMO-MUSCAT. Moreover, HOMs are implemented in the same way for the regional SOA modeling. 3D simulations were performed with an equilibrium partitioning and diffusion dependent partitioning approach, respectively. The presentation will provide first 3D simulation results including comparisons with field measurements from the TROPOS field site

  4. Modeling of defect formation in silicon carbide during PVT growth

    Science.gov (United States)

    Drachev, Roman Victorovich

    2002-01-01

    The improvement of PVT grown SiC structural quality is crucial for the wide commercialization of SiC devices that feature superior characteristics for power conditioning and control. This is why, this dissertation is devoted to investigation and development of comprehensive models that can help to explain, understand and, then, suppress (eliminate) formation of various defects in SiC during PVT growth. The dissertation consists of six chapters. The first chapter is introductory. The second chapter considers in detail the general principles and physical bases of the SiC PVT growth technique along with the temperature dependence of pressure, composition and stoichiometry of the SiC gaseous phase. Questions related to the diffusive mass transport in the SiC growth cell are also discussed. The growth velocity as a function of the mass transport rate, the heat balance at the surface of crystallization and the growth front-crystal backside temperature difference is analyzed. Also the graphitization processes and instability of the sublimation temperature in the source material region are addressed. Chapter number three concerns generation of silicon and carbon second phase precipitates at the front of SiC crystallization. The comprehensive models concerning these phenomena are developed. The fourth chapter considers defect formation in SiC caused by the presence of carbon and/or silicon second phase particles at the growth front. Generation mechanisms of such structural defects as heterogeneous inclusions, point and planar defects, and filamentary voids are discussed in detail. Chapter number five deals with the defects caused by thermal stresses in the growing boule of SiC. Analytical estimations of the axially symmetric temperature field distribution and shear stress radial distribution in plane strain approximation are employed in order to estimate the extent to which such phenomena cause the generation of dislocations and micropipe formation in the growing ingot. The

  5. Modeling of formation of intraplate partial melting zones

    Science.gov (United States)

    Perepechko, Y. V.; Sorokin, K. E.

    2010-12-01

    This study suggests the mathematical model of dynamics of partial melting in lithosphere causing formation of magmatic systems. The intraplate magmatic systems can be formed at achievement of required thermodynamic conditions, which can be developed due to the following mechanisms: contact heating; decompression melting at mantle matter penetration into lithosphere; and heating by filtering mantle melts and fluids in the weakened lithosphere zones above the asthenospheric structure related to a hotspot. The most efficient mechanism from the point of time and heating degree is the latter one. It is heating of lithosphere matter by mantle melts and fluids, which is especially important for development of melting sites in these systems. At formation of intraplate magmatic systems the fluid is filtered in a porous medium, porous matrix melts partially, and finally a granulated medium is formed there. To decrease the processes of heat and mass transfer in this system, the equations of dynamics of multiphase multivelocity media are derived in this study. In contrast to the Darcy-type models used in previous studies, the suggested two-velocity hydrodynamics theory describing fluid motions in a porous medium with complex reology is the thermodynamically consistent one and allows the description of nonstationary nonlinear processes. The governing equations of the model describe both the process of filtration through the deformed porous matrix and hydrodynamics of heterophase granulated medium without pressure equilibrium in phases. The work was supported by the grants 08-05-00467, 09-05-00602, 09-05-01084 from the Russian Foundation for Basic Research.

  6. Stellar and HI Mass Functions Predicted by a Simple Preheating Galaxy Formation Model

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star formation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function.

  7. An improved ice cloud formation parameterization in the EMAC model

    Science.gov (United States)

    Bacer, Sara; Pozzer, Andrea; Karydis, Vlassis; Tsimpidi, Alexandra; Tost, Holger; Sullivan, Sylvia; Nenes, Athanasios; Barahona, Donifan; Lelieveld, Jos

    2017-04-01

    Cirrus clouds cover about 30% of the Earth's surface and are an important modulator of the radiative energy budget of the atmosphere. Despite their importance in the global climate system, there are still large uncertainties in understanding the microphysical properties and interactions with aerosols. Ice crystal formation is quite complex and a variety of mechanisms exists for ice nucleation, depending on aerosol characteristics and environmental conditions. Ice crystals can be formed via homogeneous nucleation or heterogeneous nucleation of ice-nucleating particles in different ways (contact, immersion, condensation, deposition). We have implemented the computationally efficient cirrus cloud formation parameterization by Barahona and Nenes (2009) into the EMAC (ECHAM5/MESSy Atmospheric Chemistry) model in order to improve the representation of ice clouds and aerosol-cloud interactions. The parameterization computes the ice crystal number concentration from precursor aerosols and ice-nucleating particles accounting for the competition between homogeneous and heterogeneous nucleation and among different freezing modes. Our work shows the differences and the improvements obtained after the implementation with respect to the previous version of EMAC.

  8. ON THE FORMATION OF DIPEPTIDES IN INTERSTELLAR MODEL ICES

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, R. I.; Kim, Y. S. [Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Stockton, A. M.; Jensen, E. C.; Mathies, R. A. [Department of Chemistry, University of California, Berkeley, CA 94720 (United States)

    2013-03-10

    The hypothesis of an exogenous origin and delivery of biologically important molecules to early Earth presents an alternative route to their terrestrial in situ formation. Dipeptides like Gly-Gly detected in the Murchison meteorite are considered as key molecules in prebiotic chemistry because biofunctional dipeptides present the vital link in the evolutionary transition from prebiotic amino acids to early proteins. However, the processes that could lead to the exogenous abiotic synthesis of dipeptides are unknown. Here, we report the identification of two proteinogenic dipeptides-Gly-Gly and Leu-Ala-formed via electron-irradiation of interstellar model ices followed by annealing the irradiated samples to 300 K. Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is facile. Once synthesized and incorporated into the ''building material'' of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the beginning of life as we know it.

  9. On the Formation of Dipeptides in Interstellar Model Ices

    Science.gov (United States)

    Kaiser, R. I.; Stockton, A. M.; Kim, Y. S.; Jensen, E. C.; Mathies, R. A.

    2013-03-01

    The hypothesis of an exogenous origin and delivery of biologically important molecules to early Earth presents an alternative route to their terrestrial in situ formation. Dipeptides like Gly-Gly detected in the Murchison meteorite are considered as key molecules in prebiotic chemistry because biofunctional dipeptides present the vital link in the evolutionary transition from prebiotic amino acids to early proteins. However, the processes that could lead to the exogenous abiotic synthesis of dipeptides are unknown. Here, we report the identification of two proteinogenic dipeptides—Gly-Gly and Leu-Ala—formed via electron-irradiation of interstellar model ices followed by annealing the irradiated samples to 300 K. Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is facile. Once synthesized and incorporated into the ''building material'' of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the beginning of life as we know it.

  10. The Formation of Molecular Clouds: Insights from Numerical Models

    Science.gov (United States)

    Heitsch, Fabian

    2010-10-01

    Galactic star formation occurs at a surprisingly low rate. Yet, recent large-scale surveys of dark clouds in the Galaxy show that one rarely finds molecular clouds without young stellar objects, suggesting that star formation should occur rapidly upon molecular cloud formation. This rapid onset challenges the traditional concept of ``slow'' star formation in long-lived molecular clouds. It also imposes strong constraints on the physical properties of the parental clouds, mandating that a cloud's structure and dynamics controlling stellar birth must arise during its formation. This requires a new approach to study initial conditions of star formation, namely addressing the formation of molecular clouds. Taking into account the observational constraints, I will outline the physics of flow-driven molecular cloud formation. I will discuss the relevance and the limitations of this scenario for setting the star formation efficiency in our Galaxy and beyond.

  11. Laboratory and Numerical Modeling of Smoke Characteristics for Superfog Formation

    Science.gov (United States)

    Bartolome, C.; Lu, V.; Tsui, K.; Princevac, M.; Venkatram, A.; Mahalingam, S.; Achtemeier, G.; Weise, D.

    2011-12-01

    Land management techniques in wildland areas include prescribed fires to promote biodiversity and reduce risk of severe wildfires across the United States. Several fatal car pileups have been associated with smoke-related visibility reduction from prescribed burns. Such events have occurred in year 2000 on the interstate highways I-10 and I-95, 2001 on the I-4, 2006 on the I-95, and 2008 on the I-4 causing numerous fatalities, injuries, and damage to property. In some of the cases visibility reduction caused by smoke and fog combinations traveling over roadways have been reported to be less than 3 meters, defined as superfog. Our research focuses on delineating the conditions that lead to formation of the rare phenomena of superfog and creating a tool to enable land managers to effectively plan prescribed burns and prevent tragic events. It is hypothesized that the water vapor from combustion, live fuels, soil moisture, and ambient air condense onto the cloud condensation nuclei (CCN) particles emitted from low intensity smoldering fires. Physical and numerical modeling has been used to investigate these interactions. A physical model in the laboratory has been developed to characterize the properties of smoke resulting from smoldering pine needle litters at the PSW Forest Service in Riverside, CA. Temporal measurements of temperature, relative humidity, sensible heat flux, radiation heat flux, convective heat flux, particulate matter concentrations and visibilities have been measured for specific cases. The size distribution and number concentrations of the fog droplets formed inside the chamber by mixing cool dry and moist warm air masses to produce near superfog visibilities were measured by a Phase Doppler Particle Analyzer. Thermodynamic modeling of smoke and ambient air was conducted to estimate liquid water contents (LWC) available to condense into droplets and form significant reductions in visibility. The results show that LWC of less than 2 g m-3 can be

  12. Modelling opinion formation driven communities in social networks

    CERN Document Server

    Iñiguez, Gerardo; Kertész, János; Kaski, Kimmo K

    2010-01-01

    In a previous paper we proposed a model to study the dynamics of opinion formation in human societies by a co-evolution process involving two distinct time scales of fast transaction and slower network evolution dynamics. In the transaction dynamics we take into account short range interactions as discussions between individuals and long range interactions to describe the attitude to the overall mood of society. The latter is handled by a uniformly distributed parameter $\\alpha$, assigned randomly to each individual, as quenched personal bias. The network evolution dynamics is realized by rewiring the societal network due to state variable changes as a result of transaction dynamics. The main consequence of this complex dynamics is that communities emerge in the social network for a range of values in the ratio between time scales. In this paper we focus our attention on the attitude parameter $\\alpha$ and its influence on the conformation of opinion and the size of the resulting communities. We present numer...

  13. Thermodynamic model of coherent island formation on vicinal substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xu, E-mail: zhangxubetter@gmail.com; Sun, Xiao-Hong [Henan Key Laboratory of Laser and Opto-electric Information Technology, School of Information Engineering, Zhengzhou University, Zhengzhou 450052 (China); Yu, Yanguang [School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Northfields Ave, Wollongong, New South Wales 2522 (Australia); Ren, Xiaomin [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2014-04-28

    A thermodynamic model has been proposed to address the formation of coherent island on the vicinal substrate. The morphological transition from square based island to elongated based one with various substrate misorientations is described. The initial stage of nucleation and growth process of islands in Stranski–Krastanow system is studied by taking into account the elastic deformations and the change of energy in the case of two-dimensional growth mode. The theoretical analysis shows the minimum nucleation barrier of island is on the decrease with increment of substrate misorientation, which means the nucleation of island on vicinal substrate is more favorable than that on flat substrate. By using the fitting data of experimental results done by Persichetti et al., [Phys. Rev. Lett. 104, 036104 (2010) and Phys. Rev. B 82, 121309(R) (2010)], we provide a meaningful explanation of the experimental observations.

  14. Occurrence and variability of iodinated trihalomethanes concentrations within two drinking-water distribution networks.

    Science.gov (United States)

    Ioannou, Panagiotis; Charisiadis, Pantelis; Andra, Syam S; Makris, Konstantinos C

    2016-02-01

    Non-iodo-containing trihalomethanes (TTHM) are frequently detected in chlorinated tap water and currently regulated against their carcinogenic potential. Iodinated THM (ITHM) may also form in disinfected with chlorine waters that are high in iodine content, but little is known about their magnitude and variability within the drinking-water pipe distribution network of urban areas. The main objective of this study was to determine the magnitude and variability of ITHM and TTHM levels and their corresponding daily intake estimates within the drinking water distribution systems of Limassol and Nicosia cities of Cyprus, using tap samples collected from individual households (n=37). In Limassol, mean household tap water ITHM and TTHM levels was 0.58 and 38 μg L(-1), respectively. Dichloroiodomethane (DCIM) was the dominant species of the two measured ITHM compounds accounting for 77% of total ITHM and in the range of 0.032 and 1.65 μg L(-1). The range of DCIM concentrations in Nicosia tap water samples was narrower (0.032 - 0.848 μg L(-1)). Mean total iodine concentration in tap water samples from the seaside city of Limassol was 15 μg L(-1) and approximately twice to those observed in samples from the mainland Nicosia city. However, iodine concentrations did not correlate with the ITHM levels. The calculated chronic daily intake rates of ITHM were low when compared with those of TTHM, but because of their widespread occurrence in tap water and their enhanced mammalian cell toxicity, additional research is warranted to assess the magnitude and variability of human ITHM exposures.

  15. Parameterization of Cloud Droplet Formation in Global Climate Models

    Science.gov (United States)

    Nenes, A.; Seinfeld, J.H.

    2003-01-01

    An aerosol activation parameterization has been developed based on a generalized representation of aerosol size and composition within the framework of an ascending adiabatic parcel; this allows for parameterizing the activation of chemically complex aerosol with an arbitrary size distribution and mixing state. The new parameterization introduces the concept of"population splitting", in which the cloud condensation nuclei (CCN) that form droplets are treated as two separate populations; those that have a size close to their critical diameter and those that do not.Explicit consideration of kinetic limitations of droplet growth is introduced. Our treatment of the activation process unravels much of its complexity. As a result of this, a substantial number of conditions of droplet formation can be treated completely free of empirical information or correlations; there are, however, some conditions of droplet activation for which an empirically derived correlation is utilized. Predictions of the parameterization are compared against extensive cloud parcel model simu;lations for a variety of aerosol activation conditions that cover a wide range of chemical variability and CCN concentrations. The parameterization tracks the parcel model simulations closely and robustly. The parameterization presented here is intended to allow for a comprehensive assessment of the aerosol indirect effect in general circulation models.

  16. Dynamical complexity in the perception-based network formation model

    Science.gov (United States)

    Jo, Hang-Hyun; Moon, Eunyoung

    2016-12-01

    Many link formation mechanisms for the evolution of social networks have been successful to reproduce various empirical findings in social networks. However, they have largely ignored the fact that individuals make decisions on whether to create links to other individuals based on cost and benefit of linking, and the fact that individuals may use perception of the network in their decision making. In this paper, we study the evolution of social networks in terms of perception-based strategic link formation. Here each individual has her own perception of the actual network, and uses it to decide whether to create a link to another individual. An individual with the least perception accuracy can benefit from updating her perception using that of the most accurate individual via a new link. This benefit is compared to the cost of linking in decision making. Once a new link is created, it affects the accuracies of other individuals' perceptions, leading to a further evolution of the actual network. As for initial actual networks, we consider both homogeneous and heterogeneous cases. The homogeneous initial actual network is modeled by Erdős-Rényi (ER) random networks, while we take a star network for the heterogeneous case. In any cases, individual perceptions of the actual network are modeled by ER random networks with controllable linking probability. Then the stable link density of the actual network is found to show discontinuous transitions or jumps according to the cost of linking. As the number of jumps is the consequence of the dynamical complexity, we discuss the effect of initial conditions on the number of jumps to find that the dynamical complexity strongly depends on how much individuals initially overestimate or underestimate the link density of the actual network. For the heterogeneous case, the role of the highly connected individual as an information spreader is also discussed.

  17. Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hui-Hai; Rutqvist, Jonny; Zheng, Liange; Sonnenthal, Eric; Houseworth, Jim; Birkholzer, Jens

    2010-08-31

    As a result of the termination of the Yucca Mountain Project, the United States Department of Energy (DOE) has started to explore various alternative avenues for the disposition of used nuclear fuel and nuclear waste. The overall scope of the investigation includes temporary storage, transportation issues, permanent disposal, various nuclear fuel types, processing alternatives, and resulting waste streams. Although geologic disposal is not the only alternative, it is still the leading candidate for permanent disposal. The realm of geologic disposal also offers a range of geologic environments that may be considered, among those clay shale formations. Figure 1-1 presents the distribution of clay/shale formations within the USA. Clay rock/shale has been considered as potential host rock for geological disposal of high-level nuclear waste throughout the world, because of its low permeability, low diffusion coefficient, high retention capacity for radionuclides, and capability to self-seal fractures induced by tunnel excavation. For example, Callovo-Oxfordian argillites at the Bure site, France (Fouche et al., 2004), Toarcian argillites at the Tournemire site, France (Patriarche et al., 2004), Opalinus clay at the Mont Terri site, Switzerland (Meier et al., 2000), and Boom clay at Mol site, Belgium (Barnichon et al., 2005) have all been under intensive scientific investigations (at both field and laboratory scales) for understanding a variety of rock properties and their relations with flow and transport processes associated with geological disposal of nuclear waste. Clay/shale formations may be generally classified as indurated and plastic clays (Tsang et al., 2005). The latter (including Boom clay) is a softer material without high cohesion; its deformation is dominantly plastic. For both clay rocks, coupled thermal, hydrological, mechanical and chemical (THMC) processes are expected to have a significant impact on the long-term safety of a clay repository. For

  18. Evaluation of the relationship between bulk organic precursors and disinfection byproduct formation for advanced oxidation processes.

    Science.gov (United States)

    Mayer, Brooke K; Daugherty, Erin; Abbaszadegan, Morteza

    2015-02-01

    Advanced oxidation processes (AOPs) are gaining traction as they offer mineralization potential rather than transferring contaminants between media. However, AOPs operated with limited energy and/or chemical inputs can exacerbate disinfection byproduct (DBP) formation, even as precursors such as dissolved organic carbon, UV254, and specific UV absorbance (SUVA) decrease. This study examined the relationship between DBP precursors and formation using TiO2 photocatalysis experiments, external AOP and non-AOP data, and predictive DBP models. The top-performing indicator, SUVA, generally correlated positively with trihalomethanes and haloacetic acids, but limited-energy photocatalysis yielded contrasting negative correlations. The accuracy of predicted DBP values from models based on bulk parameters was generally poor, regardless of use and extent of AOP treatment and type of source water. Though performance improved for scenarios bounded by conditions used in model development, only 0.5% of the model/dataset pairings satisfied all measured parameter boundary conditions, thereby introducing skepticism toward model usefulness. Study findings suggest that caution should be employed when using bulk indicators and/or models as a metric for AOP mitigation of DBP formation potential, particularly for limited-energy/chemical inputs.

  19. Model for Formation of Martian Residual Cap Depressions (Swiss Cheese)

    Science.gov (United States)

    Byrne, S.; Ingersoll, A. P.

    2001-12-01

    In an effort for explain the formation of the `Swiss-cheese' terrain visible on the southern residual cap of Mars (Thomas et al., Nature, 404,2000); we have developed a radiative model to follow the growth/decay of an initial depression due to sublimation/condensation of carbon dioxide. The pits making up this terrain have many distinctive features; they are shallow (~10m deep), with steep walls and flat floors and contain an interior moat that runs along the bottom of the walls. Their diameters range from a few 10's of meters to a kilometer. The model accounts for incident sunlight, emitted thermal radiation, and scattered short and long wave radiation. We have included the effects of a layer of water ice placed under the carbon dioxide at adjustable depth. The water ice layer is free to store heat during the summer (when the carbon dioxide has been removed) through subsurface diffusion of heat. Release of this heat at the end of the summer can inhibit frost formation. We have investigated many cases involving pure dry ice with constant albedo, albedo as a function of insolation, and differing albedo for fresh and residual frost (the latter has lower albedo). In most cases the initial depressions heal themselves and disappear into the surrounding terrain. Cases involving the layer of water ice provide a much closer approximation to the shape of the observed features (especially the flat bottoms). A problem arises of how much exposed water ice we can have during the summer season and still have temperatures averaged over the footprint of the Thermal Emission Spectrometer be close to the carbon dioxide sublimation temperatures. The depth to the water ice layer is a strong controlling factor of the evolution of depression shape and depth in our model. Matching this shape with observations yields important information regarding the depth to any putative water ice layer within the residual cap itself. It is known from laboratory measurements that carbon dioxide is too

  20. Modelling Collective Opinion Formation by Means of Active Brownian Particles

    CERN Document Server

    Schweitzer, F; Schweitzer, Frank; Holyst, Janusz

    1999-01-01

    The concept of active Brownian particles is used to model a collective opinion formation process. It is assumed that individuals in community create a two-component communication field that influences the change of opinions of other persons and/or can induce their migration. The communication field is described by a reaction-diffusion equation, meaning that it has a certain lifetime, which models memory effects, further it can spread out in the community. Within our stochastic approach, the opinion change of the individuals is described by a master equation, while the migration is described by a set of Langevin equations, coupled by the communication field. In the mean-field limit which holds for fast communication, we derive a critical population size, above which the community separates into a majority and a minority with opposite opinions. The existence of external support (e.g. from mass media) can change the ratio between minority and majority, until above a critical external support the supported subpop...

  1. Mathematical Modelling of Melt Lake Formation On An Ice Shelf

    Science.gov (United States)

    Buzzard, Sammie; Feltham, Daniel; Flocco, Daniela

    2016-04-01

    The accumulation of surface meltwater on ice shelves can lead to the formation of melt lakes. These structures have been implicated in crevasse propagation and ice-shelf collapse; the Larsen B ice shelf was observed to have a large amount of melt lakes present on its surface just before its collapse in 2002. Through modelling the transport of heat through the surface of the Larsen C ice shelf, where melt lakes have also been observed, this work aims to provide new insights into the ways in which melt lakes are forming and the effect that meltwater filling crevasses on the ice shelf will have. This will enable an assessment of the role of meltwater in triggering ice-shelf collapse. The Antarctic Peninsula, where Larsen C is situated, has warmed several times the global average over the last century and this ice shelf has been suggested as a candidate for becoming fully saturated with meltwater by the end of the current century. Here we present results of a 1-D mathematical model of heat transfer through an idealized ice shelf. When forced with automatic weather station data from Larsen C, surface melting and the subsequent meltwater accumulation, melt lake development and refreezing are demonstrated through the modelled results. Furthermore, the effect of lateral meltwater transport upon melt lakes and the effect of the lakes upon the surface energy balance are examined. Investigating the role of meltwater in ice-shelf stability is key as collapse can affect ocean circulation and temperature, and cause a loss of habitat. Additionally, it can cause a loss of the buttressing effect that ice shelves can have on their tributary glaciers, thus allowing the glaciers to accelerate, contributing to sea-level rise.

  2. Effects of ozone as a stand-alone and coagulation-aid treatment on the reduction of trihalomethanes precursors from high DOC and hardness water.

    Science.gov (United States)

    Sadrnourmohamadi, Mehrnaz; Gorczyca, Beata

    2015-04-15

    This study investigates the effect of ozone as a stand-alone and coagulation aid on the removal of dissolved organic carbon (DOC) from the water with a high level of DOC (13.8 mgL(-1)) and calcium hardness (270 mgL(-1)) CaCO3. Natural water collected from the Assiniboine River (Manitoba, Canada) was used in this study. Effectiveness of ozone treatment was evaluated by measurement of DOC, DOC fractions, UV254, and trihalomethane formation potential (THMFP). Additionally, zeta potential and dissolved calcium concentration were measured to discern the mechanism of ozone reactions. Results indicated that 0.8 mg O3/mg DOC ozone stand-alone can cause up to 86% UV254 reduction and up to 27% DOC reduction. DOC fractionation results showed that ozone can change the composition of DOC in the water samples, converting the hydrophobic fractions into hydrophilic ones and resulting in the reduction of THMFP. Also, ozone caused a decrease in particle stability and dissolved calcium concentration. These simultaneous ozonation effects caused improved water flocculation and enhanced removal of DOC. This resulted in reduction of the coagulant dosage when ozone doses higher than 0.2 mg O3/mg DOC were applied prior to coagulation with ferric sulfate. Also, pre-ozonation-coagulation process achieved preferential THMFP removal for all of the ozone doses tested (0-0.8 mg O3/mg DOC), leading to a lower specific THMFP in pre-ozonated-coagulated waters than in the corresponding ozonated waters.

  3. The Effects of Presentation Format for Behavior Modeling of Interpersonal Skills in Online Instruction

    Science.gov (United States)

    Doo, Min Young

    2005-01-01

    The purpose of this study was to identify the most effective model presentation format in behavior modeling to teach interpersonal skills in online learning environments. Four model presentation formats were compared; video, pictures plus audio, audio only, and text-script only. The effects of the model presentation were investigated in terms of…

  4. HFC-134a refrigerant gas hydrate formation process and RIN model

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, the macroscopic visualization experiments of HFC-134a refrigerant gas hydrate formation are investigated. According to the macroscopic photos and Mori's microscopic photos of HFC-134a hydrate formation process, the mechanism of gas hydrate formation is analyzed.A random inducement nucleation model is presented to describe the hydrate formation process. The factors affecting the fractal growth dimension in the model, such as step,branch increment and angle, are discussed.``

  5. A Model of Electron-Positron Pair Formation

    Directory of Open Access Journals (Sweden)

    Lehnert B.

    2008-01-01

    Full Text Available The elementary electron-positron pair formation process is consideredin terms of a revised quantum electrodynamic theory, with specialattention to the conservation of energy, spin, and electric charge.The theory leads to a wave-packet photon model of narrow line widthand needle-radiation properties, not being available from conventionalquantum electrodynamics which is based on Maxwell's equations. Themodel appears to be consistent with the observed pair productionprocess, in which the created electron and positron form two raysthat start within a very small region and have original directionsalong the path of the incoming photon. Conservation of angular momentum requires the photon to possess a spin, as given by the present theory but not by the conventional one. The nonzero electric field divergence further gives rise to a local intrinsic electric charge density within the photon body, whereas there is a vanishing total charge of the latter. This may explain the observed fact that the photon decays on account of the impact from an external electric field. Such a behaviour should not become possible for a photon having zero local electric charge density.

  6. A Model For Halo Formation With Axion Mixed Dark Matter

    CERN Document Server

    Marsh, David J E

    2013-01-01

    There are several issues to do with dwarf galaxy predictions in the standard $\\Lambda$CDM cosmology that have suscitated much recent debate about the possible modification of the nature of dark matter as providing a solution. We explore a novel solution involving ultra-light axions that can potentially resolve the missing satellites problem, the cusp-core problem, and the `too big to fail' problem. We discuss approximations to non-linear structure formation in dark matter models containing a component of ultra-light axions across four orders of magnitude in mass, $10^{-24}\\lesssim m_a \\lesssim 10^{-20}$, a range too heavy to be well constrained by linear cosmological probes such as the CMB and matter power spectrum, and too light for other astrophysical or terrestrial axion searches. We find that an axion of mass $m_a\\approx 10^{-21}\\text{eV}$ contributing $\\Omega_a/\\Omega_d \\gtrsim 0.85$ of the total dark matter can introduce a significant kpc scale core in a typical Milky Way satellite galaxy in sharp contr...

  7. Analysis of in vivo and in vitro DNA strand breaks from trihalomethane exposure

    Directory of Open Access Journals (Sweden)

    DeAngelo Anthony

    2004-01-01

    Full Text Available Abstract Background Epidemiological studies have linked the consumption of chlorinated surface waters to an increased risk of two major causes of human mortality, colorectal and bladder cancer. Trihalomethanes (THMs are by-products formed when chlorine is used to disinfect drinking water. The purpose of this study was to examine the ability of the THMs, trichloromethane (TCM, bromodichloromethane (BDCM, dibromochloromethane (DBCM, and tribromomethane (TBM, to induce DNA strand breaks (SB in (1 CCRF-CEM human lymphoblastic leukemia cells, (2 primary rat hepatocytes (PRH exposed in vitro, and (3 rats exposed by gavage or drinking water. Methods DNA SB were measured by the DNA alkaline unwinding assay (DAUA. CCRF-CEM cells were exposed to individual THMs for 2 hr. Half of the cells were immediately analyzed for DNA SB and half were transferred into fresh culture medium and incubated for an additional 22 hr before testing for DNA SB. PRH were exposed to individual THMs for 4 hr then assayed for DNA SB. F344/N rats were exposed to individual THMs for 4 hr, 2 weeks, and to BDCM for 5 wk then tested for DNA SB. Results CCRF-CEM cells exposed to 5- or 10-mM brominated THMs for 2 hr produced DNA SB. The order of activity was TBM>DBCM>BDCM; TCM was inactive. Following a 22-hr recovery period, all groups had fewer SB except 10-mM DBCM and 1-mM TBM. CCRF-CEM cells were found to be positive for the GSTT1-1 gene, however no activity was detected. No DNA SB, unassociated with cytotoxicity, were observed in PRH or F344/N rats exposed to individual THMs. Conclusion CCRF-CEM cells exposed to the brominated THMs at 5 or 10 mM for 2 hr showed a significant increase in DNA SB when compared to control cells. Additionally, CCRF-CEM cells exposed to DBCM and TBM appeared to have compromised DNA repair capacity as demonstrated by an increased amount of DNA SB at 22 hr following exposure. CCRF-CEM cells were found to be positive for the GSTT1-1 gene, however no activity

  8. Cancer risk assessment from exposure to trihalomethanes in tap water and swimming pool water

    Institute of Scientific and Technical Information of China (English)

    PANYAKAPO Mallika; SOONTORNCHAI Sarisak; PAOPUREE Pongsri

    2008-01-01

    We investigated the concentration of trihalomethanes (THMs) in tap water and swimming pool water in the area of the Nakhon Path-om Municipality during the period April 2005-March 2006.The concentrations of total THMs,chloroform,bromodichloromethane,dibromochloromethane and bromoform in tap water were 12.70-41.74,6.72-29.19,1.12-11.75,0.63-3.55 and 0.08-3.40 μg/L,respectively,whereas those in swimming pool water were 26.15-65.09,9.50-36.97,8.90-18.01,5.19-22.78 and ND-6.56 μg/L,respectively.It implied that the concentration of THMs in swimming pool water was higher than those in tap water,particularly,brominated-THMs.Both tap water and swimming pool water contained concentrations of total THMs below the standards of the World Health Organization (WHO),European Union (EU) and the United States Environmental Protection Agency (USEPA) phase Ⅰ,but 1 out of 60 tap water samples and 60 out of 72 swimming pool water samples contained those over the Standard of the USEPA phase Ⅱ.From the two cases of cancer risk assessment including Case Ⅰ Non-Swimmer and Case Ⅱ Swimmer,assessment of cancer risk of non-swimmers from exposure to THMs at the highest and the average concentrations was 4.43×10-5 and 2.19×10-5,respectively,which can be classified as acceptable risk according to the Standard of USEPA.Assessment of cancer risk of swimmers from exposure to THMs at the highest and the average concentrations was 1.47×10-3 and 7.99×10-4,respectively,which can be classified as unacceptable risk and needs to be improved.Risk of THMs exposure from swimming was 93.9%-94.2% of the total risk.Cancer risk of THMs concluded from various routes in descending order was:skin exposure while swimming,gastro-intestinal exposure from tap water intake,and skin exposure to tap water and gastro-intestinal exposure while swimming.Cancer risk from skin exposure while swimming was 94.18% of the total cancer risk.

  9. Disc instabilities and semi-analytic modelling of galaxy formation

    CERN Document Server

    Athanassoula, E

    2008-01-01

    The Efstathiou, Lake and Negroponte (1982) criterion can not distinguish bar stable from bar unstable discs and thus should not be used in semi-analytic galaxy formation simulations. I discuss the reasons for this, illustrate it with examples and point out shortcomings in the recipes used for spheroid formation. I propose an alternative, although much less straightforward, possibility.

  10. Dark-ages reionization and galaxy formation simulation - III. Modelling galaxy formation and the epoch of reionization

    Science.gov (United States)

    Mutch, Simon J.; Geil, Paul M.; Poole, Gregory B.; Angel, Paul W.; Duffy, Alan R.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2016-10-01

    We introduce MERAXES, a new, purpose-built semi-analytic galaxy formation model designed for studying galaxy growth during reionization. MERAXES is the first model of its type to include a temporally and spatially coupled treatment of reionization and is built upon a custom (100 Mpc)3 N-body simulation with high temporal and mass resolution, allowing us to resolve the galaxy and star formation physics relevant to early galaxy formation. Our fiducial model with supernova feedback reproduces the observed optical depth to electron scattering and evolution of the galaxy stellar mass function between z = 5 and 7, predicting that a broad range of halo masses contribute to reionization. Using a constant escape fraction and global recombination rate, our model is unable to simultaneously match the observed ionizing emissivity at z ≲ 6. However, the use of an evolving escape fraction of 0.05-0.1 at z ˜ 6, increasing towards higher redshift, is able to satisfy these three constraints. We also demonstrate that photoionization suppression of low-mass galaxy formation during reionization has only a small effect on the ionization history of the intergalactic medium. This lack of `self-regulation' arises due to the already efficient quenching of star formation by supernova feedback. It is only in models with gas supply-limited star formation that reionization feedback is effective at regulating galaxy growth. We similarly find that reionization has only a small effect on the stellar mass function, with no observationally detectable imprint at M* > 107.5 M⊙. However, patchy reionization has significant effects on individual galaxy masses, with variations of factors of 2-3 at z = 5 that correlate with environment.

  11. Molecular dynamical modelling of endohedral fullerenes formation in plasma

    Science.gov (United States)

    Fedorov, A. S.; Kovaleva, E. A.; Lubkova, T. A.; Popov, Z. I.; Kuzubov, A. A.; Visotin, M. A.; Irle, S.

    2016-02-01

    The initial stages of fullerene and endohedral metallofullerene (EMF) synthesis in carbon-helium plasma at 1500 K and 2500 K have been simulated with quantum chemical molecular dynamics (MD) based on density-functional tight-binding (DFTB). The cases of formation of large (>100 atoms) sp2-carbon clusters with scandium atoms inside were observed. These clusters are considered as precursors of fullerenes or EMFs, and thus it is shown that formation of EMFs can be explained within the framework of "shrinking hot giant" mechanism. Also, the dependence of formation rates on plasma parameters, including temperature, buffer gas and metal atoms concentrations, has been studied.

  12. Numerical modeling of experimental observations on gas formation and multi-phase flow of carbon dioxide in subsurface formations

    Science.gov (United States)

    Pawar, R.; Dash, Z.; Sakaki, T.; Plampin, M. R.; Lassen, R. N.; Illangasekare, T. H.; Zyvoloski, G.

    2011-12-01

    One of the concerns related to geologic CO2 sequestration is potential leakage of CO2 and its subsequent migration to shallow groundwater resources leading to geochemical impacts. Developing approaches to monitor CO2 migration in shallow aquifer and mitigate leakage impacts will require improving our understanding of gas phase formation and multi-phase flow subsequent to CO2 leakage in shallow aquifers. We are utilizing an integrated approach combining laboratory experiments and numerical simulations to characterize the multi-phase flow of CO2 in shallow aquifers. The laboratory experiments involve a series of highly controlled experiments in which CO2 dissolved water is injected in homogeneous and heterogeneous soil columns and tanks. The experimental results are used to study the effects of soil properties, temperature, pressure gradients and heterogeneities on gas formation and migration. We utilize the Finite Element Heat and Mass (FEHM) simulator (Zyvoloski et al, 2010) to numerically model the experimental results. The numerical models capture the physics of CO2 exsolution, multi-phase fluid flow as well as sand heterogeneity. Experimental observations of pressure, temperature and gas saturations are used to develop and constrain conceptual models for CO2 gas-phase formation and multi-phase CO2 flow in porous media. This talk will provide details of development of conceptual models based on experimental observation, development of numerical models for laboratory experiments and modelling results.

  13. Planet formation in transition disks: Modeling, spectroscopy, and theory

    Science.gov (United States)

    Liskowsky, Joseph Paul

    due to either a massive planet accreting the material onto it or via a photoevaporation process whereby the central star's radiation field ejects material from the inner disk out of the bound system in the the interstellar medium. It is presumed that this phase is the last gasp of the planetary disk's evolution before the debris disk stage and before a fully formed solar system evolves. Our work specifically focuses on one object of this transition disk class: HD100546. We add to the understanding of transition disks by showing that a model where ro-vibrational OH emission in the NIR is preferentially emitted along the 'wall' of the disk is consistent with observations, and furthermore that adding an eccentricity to this `wall' component is required to generate the necessary observed line shape. In conjunction with this observation we present supporting material which motivates the usage of such an eccentric wall component in light of predictions of the influence of giant planet formation occurring within the disk.

  14. Networking the seceder model: Group formation in social and economic systems

    Science.gov (United States)

    Grönlund, Andreas; Holme, Petter

    2004-09-01

    The seceder model illustrates how the desire to be different from the average can lead to formation of groups in a population. We turn the original, agent based, seceder model into a model of network evolution. We find that the structural characteristics of our model closely match empirical social networks. Statistics for the dynamics of group formation are also given. Extensions of the model to networks of companies are also discussed.

  15. Networking the seceder model: Group formation in social and economic systems

    CERN Document Server

    Grönlund, A

    2004-01-01

    The seceder model illustrates how the desire to be different than the average can lead to formation of groups in a population. We turn the original, agent based, seceder model into a model of network evolution. We find that the structural characteristics our model closely matches empirical social networks. Statistics for the dynamics of group formation are also given. Extensions of the model to networks of companies are also discussed.

  16. Modeling and Decentralized Control for the Multiple UAVs Formation based on Lyapunov design and redesign

    OpenAIRE

    Hou, Zhicheng; Fantoni, Isabelle; Zavala-Río, Arturo

    2013-01-01

    International audience; This paper concerns the leader-follower multiple agent formation with nonlinear and coupled individual dynamics. We address the problem of multi-agent formation control by proposing a decentralized control strategy. The agents in the formation are quad-rotors UAVs. By attributing the high-order nonlinear and unmodelled dynamics as uncertainties, we propose a switching singular system model to represent the formation of the multiple UAVs system with switching topology. ...

  17. Betting for Integral Formation through the Models of Arts Education

    Directory of Open Access Journals (Sweden)

    Julia Margarita Barco Rodríguez

    2016-06-01

    Full Text Available For a long time integral formation has been a main purpose of educational curricula. But even though it proves necessary on the ground of the benefits education may bring to human development, its outcomes are not always visible and many times it actually does not exist beyond the speech. In the field of arts teaching, the wholeness of human expressions seems to be one of the main goals in the formative purposes for young people and children. Such a commitment demands serious reflection on how and what artistic practices may bring to the formation of integral citizens, be it from the perspective of free expression or from a cognitivist or cultural one. Tracking the curricula in art education will allow us to understand the movement and whereabouts of such a high view, bringing together the conceptual and methodological arguments for it to match contemporaneity, so underlining the pertinence of art practices in education.

  18. Stochastic model for photoinduced surface relief grating formation through molecular transport in polymer films.

    Energy Technology Data Exchange (ETDEWEB)

    Juan, M.; Plain, J.; Bachelot, R.; Royer, P.; Gray, S. K.; Wiederrecht, G. P.; Univ. de Technologie de Troyes

    2008-09-01

    We use a stochastic model to study photoinduced surface relief grating (SRG) formation due to molecular transport in azobenzene polymer films. The model is shown to reproduce the essential experimental features of SRG formation. In particular, it predicts SRG formation under both p and s polarizations, and the double peaked topographies that can occur at early times of the process. The evolving molecular positions and orientations during exposure are also followed, providing a useful mechanistic picture of SRG dynamics.

  19. Blood clot formation does not affect metastasis formation or tumor growth in a murine model of breast cancer.

    Directory of Open Access Journals (Sweden)

    Stephanie Rossnagl

    Full Text Available Cancer is associated with increased fracture risk, due either to metastasis or associated osteoporosis. After a fracture, blood clots form. Because proteins of the coagulation cascade and activated platelets promote cancer development, a fracture in patients with cancer often raises the question whether it is a pathologic fracture or whether the fracture itself might promote the formation of metastatic lesions. We therefore examined whether blood clot formation results in increased metastasis in a murine model of experimental breast cancer metastasis. For this purpose, a clot was surgically induced in the bone marrow of the left tibia of immundeficient mice. Either one minute prior to or five minutes after clot induction, human cancer cells were introduced in the circulation by intracardiac injection. The number of cancer cells that homed to the intervention site was determined by quantitative real-time PCR and flow cytometry. Metastasis formation and longitudinal growth were evaluated by bioluminescence imaging. The number of cancer cells that homed to the intervention site after 24 hours was similar to the number of cells in the opposite tibia that did not undergo clot induction. This effect was confirmed using two more cancer cell lines. Furthermore, no difference in the number of macroscopic lesions or their growth could be detected. In the control group 72% developed a lesion in the left tibia. In the experimental groups with clot formation 79% and 65% developed lesions in the left tibia (p = ns when comparing each experimental group with the controls. Survival was similar too. In summary, the growth factors accumulating in a clot/hematoma are neither enough to promote cancer cell homing nor support growth in an experimental model of breast cancer bone metastasis. This suggests that blood clot formation, as occurs in traumatic fractures, surgical interventions, and bruises, does not increase the risk of metastasis formation.

  20. Comparison and Evaluation of Current Animal Models for Perineural Scar Formation in Rat

    Directory of Open Access Journals (Sweden)

    Leila O Zanjani

    2013-07-01

    Our study suggests that none of the applied animal models reproduce all essential features of clinical perineural scar formation. Therefore, more studies are needed to develop optimal animal models for translating preclinical investigations

  1. Elemental abundances in Milky Way-like galaxies from a hierarchical galaxy formation model

    NARCIS (Netherlands)

    De Lucia, Gabriella; Tornatore, Luca; Frenk, Carlos S.; Helmi, Amina; Navarro, Julio F.; White, Simon D. M.

    2014-01-01

    We develop a new method to account for the finite lifetimes of stars and trace individual abundances within a semi-analytic model of galaxy formation. At variance with previous methods, based on the storage of the (binned) past star formation history of model galaxies, our method projects the inform

  2. Soot Formation Modeling of n-dodecane and Diesel Sprays under Engine-Like Conditions

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Poon, Hiew Mun; Ng, Hoon Kiat

    2015-01-01

    This work concerns the modelling of soot formation process in diesel spray combustion under engine-like conditions. The key aim is to investigate the soot formation characteristics at different ambient temperatures. Prior to simulating the diesel combustion, numerical models including a revised m...

  3. Representing hybrid compensatory non-compensatory choice set formation in semi-compensatory models

    DEFF Research Database (Denmark)

    Kaplan, Sigal; Bekhor, Shlomo; Shigtan, Yoram

    2012-01-01

    Semi-compensatory models represent a choice process consisting of an elimination-based choice set formation upon satisfying criteria thresholds and a utility-based choice. Current semi-compensatory models assume a purely non-compensatory choice set formation and hence do not support multinomial c...

  4. Dark-ages reionization and galaxy formation simulation III: Modelling galaxy formation and the Epoch of Reionization

    CERN Document Server

    Mutch, Simon J; Poole, Gregory B; Angel, Paul W; Duffy, Alan R; Mesinger, Andrei; Wyithe, J Stuart B

    2015-01-01

    We introduce Meraxes, a new, purpose-built semi-analytic galaxy formation model designed for studying galaxy growth during reionization. Meraxes is the first model of its type to include a temporally- and spatially-coupled treatment of reionization and is built upon a custom (100 Mpc)$^3$ N-body simulation with high temporal and mass resolution, allowing us to resolve the galaxy and star formation physics relevant to early galaxy formation. Our fiducial model with supernova feedback reproduces the observed optical depth to electron scattering and evolution of the galaxy stellar mass function between $z$=5-7, predicting that a broad range of halo masses contribute to reionization. Using a constant escape fraction and global recombination rate, our model is unable to simultaneously match the observed ionizing emissivity at $z{\\lesssim}6$. However, the use of an evolving escape fraction of 0.05-0.1 at $z{\\sim}6$, increasing towards higher redshift, is able to satisfy these three constraints. We also demonstrate ...

  5. Modeling the formation of soluble microbial products (SMP) in drinking water biofiltration

    Institute of Scientific and Technical Information of China (English)

    Yu Xin; Ye Lin; Wei Gu

    2008-01-01

    Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products (SMP) during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.

  6. Modeling the formation of soluble microbial products (SMP in drinking water biofiltration

    Directory of Open Access Journals (Sweden)

    Xin YU

    2008-09-01

    Full Text Available Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products (SMP during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.

  7. Ovule development, a new model for lateral organ formation.

    Science.gov (United States)

    Cucinotta, Mara; Colombo, Lucia; Roig-Villanova, Irma

    2014-01-01

    In spermatophytes the ovules upon fertilization give rise to the seeds. It is essential to understand the mechanisms that control ovule number and development as they ultimately determine the final number of seeds and, thereby, the yield in crop plants. In Arabidopsis thaliana, ovules arise laterally from a meristematic tissue within the carpel referred to as placenta. For a correct determination of the number of ovules, a precise establishment of the positions where ovule primordia emerge is needed, and a tight definition of the boundaries between ovules is therefore also required. In the last decades, few factors have been identified to be involved in the determination of ovule number. Recently, plant hormones have also been revealed as fundamental players in the control of the initiation of ovule formation. In this review we summarize the current knowledge about both the molecular and hormonal mechanisms that control ovule formation in Arabidopsis thaliana.

  8. Ovule development, a new model for lateral organ formation

    Directory of Open Access Journals (Sweden)

    Mara eCucinotta

    2014-03-01

    Full Text Available In spermatophytes the ovules upon fertilization give rise to the seeds. It is essential to understand the mechanisms that control ovule number and development as they ultimately determine the final number of seeds and, thereby, the yield in crop plants. In Arabidopsis thaliana, ovules arise laterally from a meristematic tissue within the carpel referred to as placenta. For a correct determination of the number of ovules, a precise establishment of the positions where ovule primordia emerge is needed, and a tight definition of the boundaries between ovules is therefore also required. In the last decades, few factors have been identified to be involved in the determination of ovule number. Recently, plant hormones have also been revealed as fundamental players in the control of the initiation of ovule formation. In this review we summarize the current knowledge about both the molecular and hormonal mechanisms that control ovule formation in Arabidopsis thaliana.

  9. Characterization of Natural Organic Matter and Disinfection Byproducts Formation Potential in Pilot-Scale Coagulation-Ultrafiltration Membrane Combined Process in Winter

    Institute of Scientific and Technical Information of China (English)

    张耀宗; 王启山; 何凤华; 丁莎莎

    2010-01-01

    A pilot-scale ultrafiltration membrane plant was set up for treating Luanhe River water with flocculating and precipitation process of waterworks.The aim is to investigate the variation and characteristics of natural organic matter and disinfection byproducts formation potential in the whole process in winter.The results show that dissolved organic matter(DOM),UV254,trihalomethanes formation potential(THMsFP) and haloacetic acids formation potential(HAAsFP) of Luanhe River water were mainly distributed in t...

  10. Toy models of ice formation in turbulent overcooled water

    CERN Document Server

    De Santi, Francesca

    2016-01-01

    A study of ice formation in stationary turbulent conditions is carried out in various limit regimes with regard to crystal growth rate, overcooling and ice entrainment at the water surface. Analytical expressions of the temperature, salinity and ice concentration mean profiles are provided, and the role of fluctuations in ice production is numerically quantified. A lower bound on the ratio of sensible heat flux to latent heat flux to the atmosphere is derived.

  11. A depositional model for organic-rich Duvernay Formation mudstones

    Science.gov (United States)

    Knapp, Levi J.; McMillan, Julia M.; Harris, Nicholas B.

    2017-01-01

    The Upper Devonian Duvernay Formation of western Canada is an organic-rich shale formation now targeted as a hydrocarbon reservoir. We present a detailed sedimentological analysis of the Duvernay Formation in order to better understand organic-rich mudstone depositional processes and conditions and to characterize the vertical and lateral heterogeneity of mudstone lithofacies that affect petrophysical and geomechanical rock properties. Organic-rich mudstone facies of the Duvernay Formation were deposited in a dynamic depositional environment by a variety of sediment transport mechanisms, including suspension settling, turbidity currents, and bottom water currents in variably oxygenated bottom waters. Suspension settling dominated in distal relatively deep areas of the basin, but evidence for weak turbidity currents and bottom water currents was observed in the form of graded beds and thin grain-supported siltstone laminae. Organic enrichment primarily occurred in distal areas as a result of bottom water anoxia and low depositional rates of inorganic sediment. In deep water locations near platform margins, alternating silty-sandy contourite beds and organic-rich mudstone beds are present, the former interpreted to have been deposited and reworked by bottom water currents flowing parallel to slope. In shallower, more oxygenated settings, mudstone lithologies vary from calcareous to argillaceous. These sediments were deposited from suspension settling, turbidity currents, and bottom water currents, although primary sedimentary structures are often obscured by extensive bioturbation. Locally, organic enrichment in dysoxic rather than anoxic bottom waters was driven by a slightly increased sedimentation rate and possibly also by aggregation of sedimentary particles in the water column due to interaction between organic matter and clay minerals. Large variations observed in sediment composition, from siliceous to calcareous to argillaceous, reflect multiple biogenic

  12. Effect of pH on the formation of disinfection byproducts in swimming pool water – Is less THM better?

    OpenAIRE

    Hansen, Kamilla Marie Speht; Willach, Sarah; Antoniou, Maria; Mosbæk, Hans; Albrechtsen, Hans-Jørgen; Andersen, Henrik Rasmus

    2012-01-01

    This study investigated the formation and predicted toxicity of different groups of disinfection byproducts (DBPs) from human exudates in relation to chlorination of pool water at different pH values. Specifically, the formation of the DBP groups trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs) and trichloramine (NCl3), resulting from the chlorination of body fluid analog, were investigated at 6.0 ≤ pH ≤ 8.0. Either the initial concentration of active chorine or free ...

  13. Halogen Bonding or Hydrogen Bonding between 2,2,6,6-Tetramethyl-piperidine-noxyl Radical and Trihalomethanes CHX3 (X=Cl, Br, I)

    Institute of Scientific and Technical Information of China (English)

    Xiao-ran Zhao; Xue Pang; Xiao-qing Yan; Wei-jun Jin

    2013-01-01

    The halogen and hydrogen bonding complexes between 2,2,6,6-tetramethylpiperidine-noxyl and trihalomethanes (CHX3,X=Cl,Br,I) are simulated by computational quantum chemistry.The molecular electrostatic potentials,geometrical parameters and interaction energy of halogen and hydrogen bonding complexes combined with natural bond orbital analysis are obtained.The results indicate that both halogen and hydrogen bonding interactions obey the order Cl<Br<I,and hydrogen bonding is stronger than the corresponding halogen bond ing.So,hydrogen bonding complexes should be dominant in trihalomethanes.However,it is possible that halogen bonding complex is competitive,even preponderant,in triiodomethane due to the similar interaction energy.This work might provide useful information on specific solvent effects as well as for understanding the mechanism of nitroxide radicals as a bioprobe to interact with the halogenated compounds in biological and biochemical fields.

  14. Linear approximation model network and its formation via evolutionary computation

    Indian Academy of Sciences (India)

    Yun Li; Kay Chen Tan

    2000-04-01

    To overcome the deficiency of `local model network' (LMN) techniques, an alternative `linear approximation model' (LAM) network approach is proposed. Such a network models a nonlinear or practical system with multiple linear models fitted along operating trajectories, where individual models are simply networked through output or parameter interpolation. The linear models are valid for the entire operating trajectory and hence overcome the local validity of LMN models, which impose the predetermination of a scheduling variable that predicts characteristic changes of the nonlinear system. LAMs can be evolved fromsampled step response data directly, eliminating the need forlocal linearisation upon a pre-model using derivatives of the nonlinear system. The structural difference between a LAM network and an LMN isthat the overall model of the latteris a parameter-varying system and hence nonlinear,while the formerremains linear time-invariant (LTI). Hence, existing LTI and transfer function theory applies to a LAM network, which is therefore easy to use for control system design. Validation results show that the proposed method offers a simple, transparent and accurate multivariable modelling technique for nonlinear systems.

  15. Consensus Formation in Science Modeled by Aggregated Bibliographic Coupling

    DEFF Research Database (Denmark)

    Nicolaisen, Jeppe; Frandsen, Tove Faber

    2012-01-01

    Abstract: The level of consensus in science has traditionally been measured by a number of different methods. The variety is important as each method measures different aspects of science and consensus. Citation analytical studies have previously measured the level of consensus using the scientific...... journal as their unit of analysis. To produce a more fine grained citation analysis one needs to study consensus formation on an even more detailed level – i.e. the scientific document or article. To do so, we have developed a new technique that measures consensus by aggregated bibliographic couplings...

  16. Models of Opinion Formation: Influence of Opinion Leaders

    CERN Document Server

    Boccara, Nino

    2007-01-01

    This paper studies the evolution of the distribution of opinions in a population of individuals in which there exist two distinct subgroups of highly-committed, well-connected opinion leaders endowed with a strong convincing power. Each individual, located at a vertex of a directed graph, is characterized by her name, the list of people she is interacting with, her level of awareness, and her opinion. Various temporal evolutions according to different local rules are compared in order to find under which conditions the formation of strongly polarized subgroups, each adopting the opinion of one of the two groups of opinion leaders, is favored.

  17. ON A PARABOLIC FREE BOUNDARY EQUATION MODELING PRICE FORMATION

    KAUST Repository

    MARKOWICH, P. A.

    2009-10-01

    We discuss existence and uniqueness of solutions for a one-dimensional parabolic evolution equation with a free boundary. This problem was introduced by Lasry and Lions as description of the dynamical formation of the price of a trading good. Short time existence and uniqueness is established by a contraction argument. Then we discuss the issue of global-in-time-extension of the local solution which is closely related to the regularity of the free boundary. We also present numerical results. © 2009 World Scientific Publishing Company.

  18. The Impact of Varied Discrimination Parameters on Mixed-Format Item Response Theory Model Selection

    Science.gov (United States)

    Whittaker, Tiffany A.; Chang, Wanchen; Dodd, Barbara G.

    2013-01-01

    Whittaker, Chang, and Dodd compared the performance of model selection criteria when selecting among mixed-format IRT models and found that the criteria did not perform adequately when selecting the more parameterized models. It was suggested by M. S. Johnson that the problems when selecting the more parameterized models may be because of the low…

  19. Particles in swimming pool filters – Does pH determine the DBP formation?

    DEFF Research Database (Denmark)

    Hansen, Kamilla Marie Speht; Willach, Sarah; Mosbæk, Hans

    2012-01-01

    The formation was investigated for different groups of disinfection byproducts (DBPs) during chlorination of filter particles from swimming pools at different pH-values and the toxicity was estimated. Specifically, the formation of the DBP group trihalomethanes (THMs), which is regulated in many...... or initial free chlorine concentrations the particles were chlorinated at different pH-values in the relevant range for swimming pools. THM and HAA formations were reduced by decreasing pH while HAN formation increased with decreasing pH. Based on the organic content the relative DBP formation from...

  20. Structure formation in a nonlocally modified gravity model

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sohyun; Dodelson, Scott

    2013-01-01

    We study a nonlocally modified gravity model proposed by Deser and Woodard which gives an explanation for current cosmic acceleration. By deriving and solving the equations governing the evolution of the structure in the Universe, we show that this model predicts a pattern of growth that differs from standard general relativity (+dark energy) at the 10-30% level. These differences will be easily probed by the next generation of galaxy surveys, so the model should be tested shortly.

  1. Flexible Virtual Structure Consideration in Dynamic Modeling of Mobile Robots Formation

    Science.gov (United States)

    El Kamel, A. Essghaier; Beji, L.; Lerbet, J.; Abichou, A.

    2009-03-01

    In cooperative mobile robotics, we look for formation keeping and maintenance of a geometric configuration during movement. As a solution to these problems, the concept of a virtual structure is considered. Based on this idea, we have developed an efficient flexible virtual structure, describing the dynamic model of n vehicles in formation and where the whole formation is kept dependant. Notes that, for 2D and 3D space navigation, only a rigid virtual structure was proposed in the literature. Further, the problem was limited to a kinematic behavior of the structure. Hence, the flexible virtual structure in dynamic modeling of mobile robots formation presented in this paper, gives more capabilities to the formation to avoid obstacles in hostile environment while keeping formation and avoiding inter-agent collision.

  2. Fuzzy social choice models explaining the government formation process

    CERN Document Server

    C Casey, Peter; A Goodman, Carly; Pook, Kelly Nelson; N Mordeson, John; J Wierman, Mark; D Clark, Terry

    2014-01-01

    This book explores the extent to which fuzzy set logic can overcome some of the shortcomings of public choice theory, particularly its inability to provide adequate predictive power in empirical studies. Especially in the case of social preferences, public choice theory has failed to produce the set of alternatives from which collective choices are made.  The book presents empirical findings achieved by the authors in their efforts to predict the outcome of government formation processes in European parliamentary and semi-presidential systems.  Using data from the Comparative Manifesto Project (CMP), the authors propose a new approach that reinterprets error in the coding of CMP data as ambiguity in the actual political positions of parties on the policy dimensions being coded. The range of this error establishes parties’ fuzzy preferences. The set of possible outcomes in the process of government formation is then calculated on the basis of both the fuzzy Pareto set and the fuzzy maximal set, and the pre...

  3. Modeling ant foraging: A chemotaxis approach with pheromones and trail formation.

    Science.gov (United States)

    Amorim, Paulo

    2015-11-21

    We consider a continuous mathematical description of a population of ants and simulate numerically their foraging behavior using a system of partial differential equations of chemotaxis type. We show that this system accurately reproduces observed foraging behavior, especially spontaneous trail formation and efficient removal of food sources. We show through numerical experiments that trail formation is correlated with efficient food removal. Our results illustrate the emergence of trail formation from simple modeling principles. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. An Investigation of Model Catalyzed Hydrocarbon Formation Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Tysoe, W. T.

    2001-05-02

    Work was focused on two areas aimed at understanding the chemistry of realistic catalytic systems: (1) The synthesis and characterization of model supported olefin metathesis catalysts. (2) Understanding the role of the carbonaceous layer present on Pd(111) single crystal model catalysts during reaction.

  5. Modeling quantitative phase image formation under tilted illuminations.

    Science.gov (United States)

    Bon, Pierre; Wattellier, Benoit; Monneret, Serge

    2012-05-15

    A generalized product-of-convolution model for simulation of quantitative phase microscopy of thick heterogeneous specimen under tilted plane-wave illumination is presented. Actual simulations are checked against a much more time-consuming commercial finite-difference time-domain method. Then modeled data are compared with experimental measurements that were made with a quadriwave lateral shearing interferometer.

  6. Two-Dimensional Numerical Modeling of Intracontinental Extension: A Case Study Of the Baikal Rift Formation

    DEFF Research Database (Denmark)

    Yang, H.; Chemia, Zurab; Artemieva, Irina

    and geophysical studies, the geodynamic origin and evolution of the BRZ is still debated. We applytwo-dimensional finite difference code to model the lithosphere-scale de-formation in several locations across the strike of the Baikal Rift zone. The model se-tup takes an advantage of regional geophysical models...... to determinethe set of parameters that may define regional li-thosphere evolution towards the present lithosphere structure, which we further con-trol by gravity data, regional volcanism, and the age of the BRZ formation. We dem-onstrate the roleof pre-existing faults on the BRZ evolution and on formation of "off...

  7. Experimental and Modeling Studies on the Prediction of Gas Hydrate Formation

    Directory of Open Access Journals (Sweden)

    Jian-Yi Liu

    2015-01-01

    Full Text Available On the base of some kinetics model analysis and kinetic observation of hydrate formation process, a new prediction model of gas hydrate formation is proposed. The analysis of the present model shows that the formation of gas hydrate not only relevant with gas composition and free water content but also relevant with temperature and pressure. Through contrast experiment, the predicted result of the new prediction method of gas hydrate crystallization kinetics is close to measured result, it means that the prediction method can reflect the hydrate crystallization accurately.

  8. Theoretical Model for the Formation of Caveolae and Similar Membrane Invaginations

    Science.gov (United States)

    Sens, Pierre; Turner, Matthew S.

    2004-01-01

    We study a physical model for the formation of bud-like invaginations on fluid lipid membranes under tension, and apply this model to caveolae formation. We demonstrate that budding can be driven by membrane-bound proteins, provided that they exert asymmetric forces on the membrane that give rise to bending moments. In particular, caveolae formation does not necessarily require forces to be applied by the cytoskeleton. Our theoretical model is able to explain several features observed experimentally in caveolae, where proteins in the caveolin family are known to play a crucial role in the formation of caveolae buds. These include 1), the formation of caveolae buds with sizes in the 100-nm range and 2), that certain N- and C-termini deletion mutants result in vesicles that are an order-of-magnitude larger. Finally, we discuss the possible origin of the morphological striations that are observed on the surfaces of the caveolae. PMID:15041647

  9. Formation of an Integrated Stock Price Forecast Model in Lithuania

    Directory of Open Access Journals (Sweden)

    Audrius Dzikevičius

    2016-12-01

    Full Text Available Technical and fundamental analyses are widely used to forecast stock prices due to lack of knowledge of other modern models and methods such as Residual Income Model, ANN-APGARCH, Support Vector Machine, Probabilistic Neural Network and Genetic Fuzzy Systems. Although stock price forecast models integrating both technical and fundamental analyses are currently used widely, their integration is not justified comprehensively enough. This paper discusses theoretical one-factor and multi-factor stock price forecast models already applied by investors at a global level and determines possibility to create and apply practically a stock price forecast model which integrates fundamental and technical analysis with the reference to the Lithuanian stock market. The research is aimed to determine the relationship between stock prices of the 14 Lithuanian companies listed in the Main List by the Nasdaq OMX Baltic and various fundamental variables. Based on correlation and regression analysis results and application of c-Squared Test, ANOVA method, a general stock price forecast model is generated. This paper discusses practical implications how the developed model can be used to forecast stock prices by individual investors and suggests additional check measures.

  10. Stochastic delay models for molecular clocks and somite formation

    Science.gov (United States)

    Burrage, Kevin; Burrage, Pamela; Leier, André; Marquez-Lago, Tatiana T.

    2007-12-01

    Delays are an important feature in temporal models of genetic regulation due to slow biochemical processes such as transcription and translation. In this paper we show how to model intrinsic noise effects in a delayed setting by either using a delay stochastic simulation algorithm (DSSA) or, for larger and more complex systems, a generalized Binomial tau-leap method (Bt-DSSA). As a particular application we apply these ideas to modeling somite segmentation in zebrafish across a number of cells in which two linked oscillatory genes her1 and her7 are synchronized via Notch signaling between the cells.

  11. Jamming and pattern formation in models of segregation

    Science.gov (United States)

    Rogers, Tim; McKane, Alan J.

    2012-04-01

    We investigate the Schelling model of social segregation, formulated as an intrinsically nonequilibrium system, in which the agents occupy districts (or patches) rather than sites on a grid. We show that this allows the equations governing the dynamical behavior of the model to be derived. Analysis of these equations reveals a jamming transition in the regime of low-vacancy density, and inclusion of a spatial dimension in the model leads to a pattern forming instability. Both of these phenomena exhibit unusual characteristics which may be studied through our approach.

  12. Mouse models for studying the formation and propagation of prions.

    Science.gov (United States)

    Watts, Joel C; Prusiner, Stanley B

    2014-07-18

    Prions are self-propagating protein conformers that cause a variety of neurodegenerative disorders in humans and animals. Mouse models have played key roles in deciphering the biology of prions and in assessing candidate therapeutics. The development of transgenic mice that form prions spontaneously in the brain has advanced our understanding of sporadic and genetic prion diseases. Furthermore, the realization that many proteins can become prions has necessitated the development of mouse models for assessing the potential transmissibility of common neurodegenerative diseases. As the universe of prion diseases continues to expand, mouse models will remain crucial for interrogating these devastating illnesses.

  13. Validation of a Model for Ice Formation around Finned Tubes

    Directory of Open Access Journals (Sweden)

    Kamal A. R. Ismai

    2016-09-01

    Full Text Available Phase change materials although attaractive option for thermal storage applications its main drawback is the slow thermal response during charging and discharging processes due to their low thermal conductivity. The present study validates a model developed by the authors some years ago on radial fins as a method to meliorate the thermal performance of PCM in horizontal storage system. The developed model for the radial finned tube is based on pure conduction, the enthalpy approach and was discretized by the finite difference method. Experiments were realized specifically to validate the model and its numerical predictions.

  14. Hydrostatic Pressure Promotes Domain Formation in Model Lipid Raft Membranes.

    Science.gov (United States)

    Worcester, David L; Weinrich, Michael

    2015-11-01

    Neutron diffraction measurements demonstrate that hydrostatic pressure promotes liquid-ordered (Lo) domain formation in lipid membranes prepared as both oriented multilayers and unilamellar vesicles made of a canonical ternary lipid mixture for which demixing transitions have been extensively studied. The results demonstrate an unusually large dependence of the mixing transition on hydrostatic pressure. Additionally, data at 28 °C show that the magnitude of increase in Lo caused by 10 MPa pressure is much the same as the decrease in Lo produced by twice minimum alveolar concentrations (MAC) of general anesthetics such as halothane, nitrous oxide, and xenon. Therefore, the results may provide a plausible explanation for the reversal of general anesthesia by hydrostatic pressure.

  15. How to build transcriptional network models of mammalian pattern formation.

    Directory of Open Access Journals (Sweden)

    Chrissa Kioussi

    Full Text Available BACKGROUND: Genetic regulatory networks of sequence specific transcription factors underlie pattern formation in multicellular organisms. Deciphering and representing the mammalian networks is a central problem in development, neurobiology, and regenerative medicine. Transcriptional networks specify intermingled embryonic cell populations during pattern formation in the vertebrate neural tube. Each embryonic population gives rise to a distinct type of adult neuron. The homeodomain transcription factor Lbx1 is expressed in five such populations and loss of Lbx1 leads to distinct respecifications in each of the five populations. METHODOLOGY/PRINCIPAL FINDINGS: We have purified normal and respecified pools of these five populations from embryos bearing one or two copies of the null Lbx1(GFP allele, respectively. Microarrays were used to show that expression levels of 8% of all transcription factor genes were altered in the respecified pool. These transcription factor genes constitute 20-30% of the active nodes of the transcriptional network that governs neural tube patterning. Half of the 141 regulated nodes were located in the top 150 clusters of ultraconserved non-coding regions. Generally, Lbx1 repressed genes that have expression patterns outside of the Lbx1-expressing domain and activated genes that have expression patterns inside the Lbx1-expressing domain. CONCLUSIONS/SIGNIFICANCE: Constraining epistasis analysis of Lbx1 to only those cells that normally express Lbx1 allowed unprecedented sensitivity in identifying Lbx1 network interactions and allowed the interactions to be assigned to a specific set of cell populations. We call this method ANCEA, or active node constrained epistasis analysis, and think that it will be generally useful in discovering and assigning network interactions to specific populations. We discuss how ANCEA, coupled with population partitioning analysis, can greatly facilitate the systematic dissection of

  16. Are We There Yet? Using Rubrics to Support Progress toward Proficiency and Model Formative Assessment

    Science.gov (United States)

    Kinne, Lenore J.; Hasenbank, Jon F.; Coffey, David

    2014-01-01

    Classroom assessment, especially formative assessment, is one of the most challenging areas for new teachers, so it is imperative that teacher educators model effective classroom assessment practices. This article describes the use of rubrics in formative assessment, to support candidates in their progress toward mastery of course outcomes and to…

  17. Predictive Modeling of Flavor Compound Formation in the Maillard Reaction: A SWOT Analysis

    NARCIS (Netherlands)

    Boekel, van M.A.J.S.

    2010-01-01

    The importance of Maillard flavor compounds for food quality is undisputed, but we are far from being able to control such formation quantitatively in food processing. Kinetic models attempt to predict rates of formation as a function of temperature, pH, water activity/content, and chemical reactivi

  18. Mathematical models for the trimethylamine (TMA) formation on packed cod fish fillets at different temperatures

    NARCIS (Netherlands)

    Heising, J.K.; Boekel, van M.A.J.S.; Dekker, M.

    2014-01-01

    The microbial formation of trimethylamine (TMA) can be used as a quality indicator compound to predict the freshness of fish during its shelf life. In a supply chain with fluctuating temperatures, mathematical models will be valuable tools to simulate this formation as a function of temperature and

  19. MODEL OF STAFFING FORMATION IN THE STATE STATISTICS SERVICE OF UKRAINE

    Directory of Open Access Journals (Sweden)

    V. Gontiuk

    2014-09-01

    Full Text Available The paper developed a model of staffing formation in the organization. Author analyzed the gender, age and education staff characteristics, work experience, job categories, staff training, staff movement and enrollment personnel reserve in the State Statistics Service of Ukraine. This study provides the measures to implement a plan of staffing formation in the State Statistics Service of Ukraine.

  20. MODEL OF STAFFING FORMATION IN THE STATE STATISTICS SERVICE OF UKRAINE

    OpenAIRE

    V. Gontiuk

    2014-01-01

    The paper developed a model of staffing formation in the organization. Author analyzed the gender, age and education staff characteristics, work experience, job categories, staff training, staff movement and enrollment personnel reserve in the State Statistics Service of Ukraine. This study provides the measures to implement a plan of staffing formation in the State Statistics Service of Ukraine.

  1. Predictive Modeling of Flavor Compound Formation in the Maillard Reaction: A SWOT Analysis

    NARCIS (Netherlands)

    Boekel, van M.A.J.S.

    2010-01-01

    The importance of Maillard flavor compounds for food quality is undisputed, but we are far from being able to control such formation quantitatively in food processing. Kinetic models attempt to predict rates of formation as a function of temperature, pH, water activity/content, and chemical

  2. 2D numerical modelling of meandering channel formation

    Indian Academy of Sciences (India)

    Y Xiao; G Zhou; F S Yang

    2016-03-01

    A 2D depth-averaged model for hydrodynamic sediment transport and river morphological adjustment was established. The sediment transport submodel takes into account the influence of non-uniform sediment with bed surface armoring and considers the impact of secondary flow in the direction of bed-loadtransport and transverse slope of the river bed. The bank erosion submodel incorporates a simple simulation method for updating bank geometry during either degradational or aggradational bed evolution. Comparison of the results obtained by the extended model with experimental and field data, and numericalpredictions validate that the proposed model can simulate grain sorting in river bends and duplicate the characteristics of meandering river and its development. The results illustrate that by using its control factors, the improved numerical model can be applied to simulate channel evolution under differentscenarios and improve understanding of patterning processes.

  3. Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation.

    Science.gov (United States)

    Le Roux, Julien; Gallard, Hervé; Croué, Jean-Philippe

    2011-05-01

    Disinfection with chloramines is often used to reduce the production of regulated disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The reactivity of these molecules with monochloramine (NH(2)Cl) is studied through the formation of NDMA, and other halogenated DBPs such as haloacetonitriles (HANs) and AOX (Adsorbable Organic Halides). Several compounds investigated formed NDMA in greater amounts than DMA, revealing the importance of structural characteristics of tertiary amines for NDMA formation. Among these compounds, the pharmaceutical ranitidine showed the highest molar conversion to NDMA. The pH and dissolved oxygen content of the solution were found to play a major role for the formation of NDMA from ranitidine. NDMA was formed in higher amounts at pH around pH 8 and a lower concentration of dissolved oxygen dramatically decreased NDMA yields. These findings seem to indicate that dichloramine (NHCl(2)) is not the major oxidant involved in the formation of NDMA from ranitidine, results in contradiction with the reaction mechanisms proposed in the literature. Dissolved oxygen was also found to influence the formation of other oxygen-containing DBPs (i.e. trichloronitromethane and haloketones). The results of this study identify several anthropogenic precursors of NDMA, indicating that chloramination of waters impacted by these tertiary amines could lead to the formation of significant amounts of NDMA and other non-regulated DBPs of potential health concern (e

  4. Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation

    KAUST Repository

    Le Roux, Julien

    2011-05-01

    Disinfection with chloramines is often used to reduce the production of regulated disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The reactivity of these molecules with monochloramine (NH2Cl) is studied through the formation of NDMA, and other halogenated DBPs such as haloacetonitriles (HANs) and AOX (Adsorbable Organic Halides). Several compounds investigated formed NDMA in greater amounts than DMA, revealing the importance of structural characteristics of tertiary amines for NDMA formation. Among these compounds, the pharmaceutical ranitidine showed the highest molar conversion to NDMA. The pH and dissolved oxygen content of the solution were found to play a major role for the formation of NDMA from ranitidine. NDMA was formed in higher amounts at pH around pH 8 and a lower concentration of dissolved oxygen dramatically decreased NDMA yields. These findings seem to indicate that dichloramine (NHCl2) is not the major oxidant involved in the formation of NDMA from ranitidine, results in contradiction with the reaction mechanisms proposed in the literature. Dissolved oxygen was also found to influence the formation of other oxygen-containing DBPs (i.e. trichloronitromethane and haloketones). The results of this study identify several anthropogenic precursors of NDMA, indicating that chloramination of waters impacted by these tertiary amines could lead to the formation of significant amounts of NDMA and other non-regulated DBPs of potential health concern (e

  5. Validation of a Model for Ice Formation around Finned Tubes

    OpenAIRE

    Kamal A. R. Ismai; Fatima A. M. Lino

    2016-01-01

    Phase change materials although attaractive option for thermal storage applications its main drawback is the slow thermal response during charging and discharging processes due to their low thermal conductivity. The present study validates a model developed by the authors some years ago on radial fins as a method to meliorate the thermal performance of PCM in horizontal storage system. The developed model for the radial finned tube is based on pure conduction, the enthalpy approach and was di...

  6. Knowledge in formation: The machine-modeled frame of mind

    Energy Technology Data Exchange (ETDEWEB)

    Shore, B.

    1996-12-31

    Artificial Intelligence researchers have used the digital computer as a model for the human mind in two different ways. Most obviously, the computer has been used as a tool on which simulations of thinking-as-programs are developed and tested. Less obvious, but of great significance, is the use of the computer as a conceptual model for the human mind. This essay traces the sources of this machine-modeled conception of cognition in a great variety of social institutions and everyday experienced treating them as {open_quotes}cultural models{close_quotes} which have contributed to the naturalness of The mine-as-machine paradigm for many Americans. The roots of these models antedate the actual development of modern computers, and take the form of a {open_quotes}modularity schema{close_quotes} that has shaped the cultural and cognitive landscape of modernity. The essay concludes with a consideration of some of the cognitive consequences of this extension of machine logic into modern life, and proposes an important distinction between information processing models of thought and meaning-making in how human cognition is conceptualized.

  7. FROM CAD MODEL TO 3D PRINT VIA “STL” FILE FORMAT

    Directory of Open Access Journals (Sweden)

    Cătălin IANCU

    2010-06-01

    Full Text Available The paper work presents the STL file format, which is now used for transferring information from CAD software to a 3D printer, for obtaining the solid model in Rapid prototyping and Computer Aided Manufacturing. It’s presented also the STL format structure, its history, limitations and further development, as well as its new version to arrive and other similar file formats. As a conclusion, STL files used to transfer data from CAD package to 3D printers has a series of limitations and therefore new formats will replace it soon.

  8. Mathematical Modelling of Fluid Flow in Cone and Cavitation Formation

    Directory of Open Access Journals (Sweden)

    Milada KOZUBKOVÁ

    2011-06-01

    Full Text Available Problem of cavitation is the undesirable phenomena occuring in the fluid flow in many hydraulic application (pumps, turbines, valves, etc.. Therefore this is in the focus of interest using experimental and mathematical methods. Based on cavitation modelling in Laval nozzle results and experience [1], [2], [4], following problem described as the water flow at the outlet from turbine blade wheel was solved. Primarily the problem is simplified into modelling of water flow in cone. Profiles of axial, radial and tangential velocity are defined on inlet zone. The value of pressure is defined on the outlet. Boundary conditions were defined by main investigator of the grant project – Energy Institute, Victor Kaplan’s Department of Fluid Engineering, Faculty of Mechanical Engineering, Brno University of Technology. The value of air volume was insignificant. Cavitation was solved by Singhal model of cavitation.

  9. A Broad Dynamical Model for Pattern Formation by Lateral Inhibition

    CERN Document Server

    Arcak, Murat

    2012-01-01

    Many patterning events in multi-cellular organisms rely on cell-to-cell contact signaling, such as the Notch pathway in metazoans. A particularly interesting phenomenon in this form of communication is lateral inhibition where a cell that adopts a particular fate inhibits its immediate neighbors from doing the same. Dynamical models are of great interest for understanding the circuit topologies involved in lateral inhibition and for predicting the associated patterns. Several simplified models have been employed for Notch signalling pathways in the literature. The objective of this paper is to present an abstract dynamical model that captures the essential features of lateral inhibition and to demonstrate with dynamical systems techniques that these features indeed lead to patterning.

  10. FROM CAD MODEL TO 3D PRINT VIA “STL” FILE FORMAT

    National Research Council Canada - National Science Library

    Cătălin IANCU; Daniela IANCU; Alin STĂNCIOIU

    2010-01-01

    The paper work presents the STL file format, which is now used for transferring information from CAD software to a 3D printer, for obtaining the solid model in Rapid prototyping and Computer Aided Manufacturing...

  11. Pizza or Pancake? Formation Models of Gas Escape Biosignatures in Terrestrial and Martian Sediments

    Science.gov (United States)

    Bonaccorsi, R.; Fairen, A. G.; Baker, L.; McKay, C. P.; Willson, D.

    2016-05-01

    Fine-grained sedimentary hollowed structures were imaged in Gale Crater, but no biomarkers identified to support biology. Our observation-based (gas escape) terrestrial model could inform on possible martian paleoenvironments at time of formation.

  12. Kinetic modelling: A tool to predict the formation of acrylamide in potato crisps

    NARCIS (Netherlands)

    Knol, J.J.; Viklund, G.Å.I.; Linssen, J.P.H.; Sjöholm, I.M.; Skog, K.I.; Boekel, van M.A.J.S.

    2009-01-01

    Three empirical models were used to fit the formation of acrylamide in crisps of three different cold-sweetened potato genotypes, fried under the same experimental conditions. Statistical methods were used to compare the performance of the models, with the 'Logistic-Exponential' model performing the

  13. Political economy models and agricultural policy formation: empirical applicability and relevance for the CAP.

    NARCIS (Netherlands)

    Zee, van der F.A.

    1997-01-01

    This study explores the relevance and applicability of political economy models for the explanation of agricultural policies. Part I (chapters 4-7) takes a general perspective and evaluates the empirical applicability of voting models and interest group models to agricultural policy formation in ind

  14. Nonlinear structure formation in the Cubic Galileon gravity model

    CERN Document Server

    Barreira, Alexandre; Hellwing, Wojciech A; Baugh, Carlton M; Pascoli, Silvia

    2013-01-01

    We model the linear and nonlinear growth of large scale structure in the Cubic Galileon gravity model, by running a suite of N-body cosmological simulations using the {\\tt ECOSMOG} code. Our simulations include the Vainshtein screening effect, which reconciles the Cubic Galileon model with local tests of gravity. In the linear regime, the amplitude of the matter power spectrum increases by $\\sim 25%$ with respect to the standard $\\Lambda$CDM model today. The modified expansion rate accounts for $\\sim 20%$ of this enhancement, while the fifth force is responsible for only $\\sim 5%$. This is because the effective unscreened gravitational strength deviates from standard gravity only at late times, even though it can be twice as large today. In the nonlinear regime ($k \\gtrsim 0.1 h\\rm{Mpc}^{-1}$), the fifth force leads to only a modest increase ($\\lesssim 8%$) in the clustering power on all scales due to the very efficient operation of the Vainshtein mechanism. Such a strong effect is typically not seen in other...

  15. Formation of algae growth constitutive relations for improved algae modeling.

    Energy Technology Data Exchange (ETDEWEB)

    Gharagozloo, Patricia E.; Drewry, Jessica Louise.

    2013-01-01

    This SAND report summarizes research conducted as a part of a two year Laboratory Directed Research and Development (LDRD) project to improve our abilities to model algal cultivation. Algae-based biofuels have generated much excitement due to their potentially large oil yield from relatively small land use and without interfering with the food or water supply. Algae mitigate atmospheric CO2 through metabolism. Efficient production of algal biofuels could reduce dependence on foreign oil by providing a domestic renewable energy source. Important factors controlling algal productivity include temperature, nutrient concentrations, salinity, pH, and the light-to-biomass conversion rate. Computational models allow for inexpensive predictions of algae growth kinetics in these non-ideal conditions for various bioreactor sizes and geometries without the need for multiple expensive measurement setups. However, these models need to be calibrated for each algal strain. In this work, we conduct a parametric study of key marine algae strains and apply the findings to a computational model.

  16. An apparent permeability model of shale gas under formation conditions

    Science.gov (United States)

    Chen, Peng; Jiang, Shan; Chen, Yan; Wang, Shanshan

    2017-08-01

    There are various types of pores in shale, mainly consisting of nanopores and micropores, causing flow regime variations and apparent permeability changes during the development of the reservoir. In this paper, a Knudsen number calculation model is proposed with the actual conditions of gas in a shale reservoir. Then, based on the distribution of pores in shale, an apparent permeability model is established using hydrodynamics, and a calculation method is put forward for the actual permeability of a reservoir. Finally, the Knudsen number model and the permeability correction coefficient model are used to analyze the flow regime and permeability correction coefficients in pores during the development of the shale gas reservoir. Results show that with a decreasing of pressure, the Knudsen number increases, the flow regime changes from continuous flow and slip flow to transition flow or free molecular flow. When the Knudsen number is Kn > 0.1, and with a further increasing of Kn, gas molecule slippage greatly intensifies and the permeability correction coefficient K app/Kd significantly increases. While the Knudsen number increases, the permeability correction coefficient significantly increases in the micropores and the small pores, but this does not appear in the macropores and the mesopores. These results can be used to guide flow regime analysis and production forecasting in shale gas reservoirs.

  17. A thermodynamic model to predict wax formation in petroleum fluids

    Energy Technology Data Exchange (ETDEWEB)

    Coutinho, J.A.P. [Universidade de Aveiro (Portugal). Dept. de Quimica. Centro de Investigacao em Quimica]. E-mail: jcoutinho@dq.ua.pt; Pauly, J.; Daridon, J.L. [Universite de Pau et des Pays de l' Adour, Pau (France). Lab. des Fluides Complexes

    2001-12-01

    Some years ago the authors proposed a model for the non-ideality of the solid phase, based on the Predictive Local Composition concept. This was first applied to the Wilson equation and latter extended to NRTL and UNIQUAC models. Predictive UNIQUAC proved to be extraordinarily successful in predicting the behaviour of both model and real hydrocarbon fluids at low temperatures. This work illustrates the ability of Predictive UNIQUAC in the description of the low temperature behaviour of petroleum fluids. It will be shown that using Predictive UNIQUAC in the description of the solid phase non-ideality a complete prediction of the low temperature behaviour of synthetic paraffin solutions, fuels and crude oils is achieved. The composition of both liquid and solid phases, the amount of crystals formed and the cloud points are predicted within the accuracy of the experimental data. The extension of Predictive UNIQUAC to high pressures, by coupling it with an EOS/G{sup E} model based on the SRK EOS used with the LCVM mixing rule, is proposed and predictions of phase envelopes for live oils are compared with experimental data. (author)

  18. A THERMODYNAMIC MODEL TO PREDICT WAX FORMATION IN PETROLEUM FLUIDS

    Directory of Open Access Journals (Sweden)

    J.A.P. Coutinho

    2001-12-01

    Full Text Available Some years ago the authors proposed a model for the non-ideality of the solid phase, based on the Predictive Local Composition concept. This was first applied to the Wilson equation and latter extended to NRTL and UNIQUAC models. Predictive UNIQUAC proved to be extraordinarily successful in predicting the behaviour of both model and real hydrocarbon fluids at low temperatures. This work illustrates the ability of Predictive UNIQUAC in the description of the low temperature behaviour of petroleum fluids. It will be shown that using Predictive UNIQUAC in the description of the solid phase non-ideality a complete prediction of the low temperature behaviour of synthetic paraffin solutions, fuels and crude oils is achieved. The composition of both liquid and solid phases, the amount of crystals formed and the cloud points are predicted within the accuracy of the experimental data. The extension of Predictive UNIQUAC to high pressures, by coupling it with an EOS/G E model based on the SRK EOS used with the LCVM mixing rule, is proposed and predictions of phase envelopes for live oils are compared with experimental data.

  19. Formation of a vesicovaginal fistula in a pig model

    DEFF Research Database (Denmark)

    Lindberg, Jennifer; Rickardsson, Emilie; Andersen, Margrethe

    2015-01-01

    Objective: To establish an animal model of a vesicovaginal fistula that can later be used in the development of new treatment modalities. Materials and methods: Six female pigs of Landrace/Yorkshire breed were used. Vesicotomy was performed through open surgery. An standardized incision between t...

  20. Formation Models and Distribution of Oil and Gas Pools in Tarim Basin,China

    Institute of Scientific and Technical Information of China (English)

    Long Shengxiang

    2008-01-01

    This article reports the main formation models and distribution of the oil and gas pools in Tarim basin,China,including (I) occurrence of the found oil and gas pools,(2) main formation models of oil and gas pools,and (3) distribution law of oil/gas pools.Petroleum is distributed widely in the strata of Tarim basin from the Sinian at the bottom to the Neogene at the top.However,the found oil and gas fields are mainly distributed in Shaya (沙雅) uplift,Tazhong (塔中) uplift,and Kuche (库车)depression.This article presents 4 main formation models,namely,early formation and long-term preservation,early formation and late reformation,middle-late multiphase-multisource formation,late single-stage formation.Tarim basin is very rich in petroleum resources.Long-term inherited intrabasinal paleohighs and slope zones are the most favorable areas for accumulation of hydrocarbons,but the types of oil and gas pools are different from area to area.The control of unconformities and faults on hydrocarbon accumulating is prominent in Tarim basin.Preservation conditions are of utmost importance.Formation of some oil and gas pools is the result of reforming and re-accumulating of early accumulated hydrocarbons.

  1. What is the right way to quench star formation in semi-analytic model of galaxy formation?

    CERN Document Server

    Luo, Yu

    2016-01-01

    Semi-analytic models of galaxy formation are powerful tools to study the evolution of galaxy population in a cosmological context. However, most models over-predict the number of low-mass galaxies at high redshifts and the color of model galaxies are not right in the sense that low-mass satellite galaxies are too red and centrals are too blue. The recent version of the L-Galaxies model by Henriques et al.(H15) is a step forward to solve these problems by reproducing the evolution of stellar mass function and the overall fraction of red galaxies. In this paper we compare the two model predictions of L-Galaxies (the other is Guo et al. , G13) to the SDSS data in detail. We find that in the H15 model the red fraction of central galaxies now agrees with the data due to their implementation of strong AGN feedback, but the stellar mass of centrals in massive haloes is now slightly lower than the data. For satellite galaxies, the red fraction of low-mass galaxies ($\\log M_{*}/M_{\\odot} < 10$) also agrees with the...

  2. Experimental and Modeling Study of Kinetics for Methane Hydrate Formation with Tetrahydrofuran as Promoter

    Institute of Scientific and Technical Information of China (English)

    Ning Zhengfu; Zhang Shixi; Zhang Qin; Zhen Shuangyi; Chen Guangjin

    2007-01-01

    The kinetics behavior of methane hydrate formation in the presence of tetrahydrofuran (THF) as promoter was studied. A set of experimental equipment was designed and constructed. A series of kinetics data for the formation of methane hydrate in the presence of THF were measured with the isochoric method. The influences of temperature,pressure and liquid flow rate on the methane consumption rate were studied respectively. Based on the Chen-Guo hydrate formation mechanism,a kinetics model for the formation of methane hydrate in the presence of THF by using the dimensionless Gibbs free energy difference of quasi-chemical reaction of basic hydrate formation,,as the driving force was proposed. The model was used to calculate the rate of methane consumption and it was shown that the calculated results were in good agreement with the experimental results.

  3. Effects of fruit extracts on the formation of acrylamide in model reactions and fried potato crisps.

    Science.gov (United States)

    Cheng, Ka-Wing; Shi, Jian-Jun; Ou, Shi-Yi; Wang, Mingfu; Jiang, Yue

    2010-01-13

    Natural products extracted from plants and fruits have attracted increasing attention for the development of effective inhibitors against the formation of acrylamide during food processing. In this study, six fruit extracts (apple, blueberry, mangosteen, longan, dragon fruit with white flesh, and dragon fruit with red flesh) were compared for their activities against acrylamide formation in chemical models containing equal molar quantities of glucose and asparagine in distilled water (160 degrees C for 30 min). Apple extract demonstrated potent inhibition on acrylamide formation. Blueberry, mangosteen, and longan extracts did not have significant impact, whereas dragon fruit extracts enhanced acrylamide formation. Column chromatography guided by chemical model analysis showed that the proanthocyanidin-rich subfraction played a key role in mediating the inhibitory activity. The inhibitory activity was finally corroborated in fried potato crisps. The present study identified some natural products that might have important applications in the food industry to inhibit acrylamide formation.

  4. Experimental and modeling study of de novo formation of PCDD/PCDF on MSW fly ash

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-dong; ZHANG Ji; YAN Jian-hua; CEN Ke-fa; RYAN Shawn P; GULLETT Brian K; LEE Chunwai

    2007-01-01

    The effect of sulfur dioxide (SO2) on formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) has been studied in an entrained-flow reactor (EFR) under simulated waste combustion conditions. A chlorination model based on conditional probability was employed to evaluate the homologue patterns of PCDDs and PCDFs. Results revealed that the presence of SO2 did not change the formation pathway although SO2 suppressed PCDD/F formation. The model prediction of PCDF showed good agreement with the experimental data (R=0.95) while the prediction for PCDDs was not as good. This may be explained because potential chlorination pathways play a significant role in PCDF formation, while PCDDs are mainly formed through condensation reactions. Furthermore, the result indicated that the steric hindrance during formation has more effects on PCDD than on PCDF due to the symmetric molecule structures of PCDDs.

  5. On the Interface Formation Model for Dynamic Triple Lines

    CERN Document Server

    Bothe, Dieter

    2015-01-01

    This paper revisits the theory of Y. Shikhmurzaev on forming interfaces as a continuum thermodynamical model for dynamic triple lines. We start with the derivation of the balances for mass, momentum, energy and entropy in a three-phase fluid system with full interfacial physics, including a brief review of the relevant transport theorems on interfaces and triple lines. Employing the entropy principle in the form given in [Bothe & Dreyer, Acta Mechanica, doi:10.1007/s00707-014-1275-1] but extended to this more general case, we arrive at the entropy production and perform a linear closure, except for a nonlinear closure for the sorption processes. Specialized to the isothermal case, we obtain a thermodynamically consistent mathematical model for dynamic triple lines and show that the total available energy is a strict Lyapunov function for this system.

  6. Formation of Modularity in a Model of Evolving Networks

    CERN Document Server

    Li, Menghui; Lai, Choy-Heng

    2011-01-01

    Modularity structures are common in various social and biological networks. However, its dynamical origin remains an open question. In this work, we set up a toy dynamical model describing the evolution of a social network. Based on the observations of real social networks, we introduced a strategy of link-creating/deleting according to the local dynamics in the model. Thus the coevolution of the dynamics and topology naturally determines the network properties. It is found that for a small coupling strength, the networked system cannot reach any synchronization and the network topology is homogeneous. Interestingly, when the coupling strength is large enough, the networked system spontaneously forms communities with different dynamical states. Meanwhile, the network topology becomes heterogeneous with modular structures. It is further shown that in certain parameter regime, both the degree and the community size in the formed network follow power-law distribution. These results are consistent with the charac...

  7. Barrier traversal times using a phenomenological track formation model

    CERN Document Server

    Palao, J P; Brouard, S; Jadczyk, A

    1997-01-01

    A phenomenological model for a measurement of barrier traversal times for particles is proposed. Two idealized detectors for passage and arrival provide entrance and exit times for the barrier traversal. The averaged traversal time is computed over the ensemble of particles detected twice, before and after the barrier. The Hartman effect can still be found when passage detectors that conserve the momentum distribution of the incident packet are used.

  8. Valores de trihalometanos en agua de consumo de la provincia de Granada, España Trihalomethane levels in drinking water in the province of Granada (Spain

    Directory of Open Access Journals (Sweden)

    Carmen Freire

    2008-12-01

    Full Text Available Objetivos: La cloración del agua da lugar a la formación de subproductos potencialmente dañinos para la salud, entre ellos los trihalometanos, que se han hallado elevados en algunas zonas de España. En este estudio se investigan los valores de trihalometanos en el agua de consumo suministrada por varios sistemas de abastecimiento de la provincia de Granada, en el área de actuación de la cohorte madres-hijos de la Red INMA (Infancia y Medio Ambiente. Métodos: Se analizaron 82 muestras de agua de consumo en dos campañas de muestreo en invierno y verano de 2006. Se determinó la concentración de cloroformo, bromodiclorometano, dibromoclorometano y bromoformo, siguiendo un procedimiento optimizado basado en cromatografía de gases y espectrometría de masas. Resultados: El rango de concentración de trihalometanos totales se situó entre 0,14 y 18,75 μg/l en la campaña de invierno y entre 0,01 y 31,87 μg/l en la de verano. El compuesto mayoritario fue cloroformo. La concentración media de trihalometanos en agua de origen superficial y subterráneo fue de 10,13 y 1,41 μg/l, respectivamente. Conclusiones: Los valores de trihalometanos encontrados son muy inferiores a la concentración máxima admisible (100 μg/l establecida por la Uniσn Europea para estos compuestos. Estos valores varνan significativamente segϊn el origen del agua, con mayores concentraciones en αreas urbana y semiurbana, donde el agua es mayoritariamente de origen superficial. La presencia de trihalometanos en la zona es menor a la descrita en otras regiones espaρolas.Objectives: Drinking water chlorination generates potentially harmful by-products, such as trihalomethanes. Trihalomethane levels are high in some parts of Spain. The aim of the present study was to investigate trihalomethane concentrations in drinking water from distinct water supplies in the province of Granada, within the framework of the Childhood and Environment (INMA study. Methods: Eighty

  9. Modeling the photoacoustic signal during the porous silicon formation

    Science.gov (United States)

    Ramirez-Gutierrez, C. F.; Castaño-Yepes, J. D.; Rodriguez-García, M. E.

    2017-01-01

    Within this work, the kinetics of the growing stage of porous silicon (PS) during the etching process was studied using the photoacoustic technique. A p-type Si with low resistivity was used as a substrate. An extension of the Rosencwaig and Gersho model is proposed in order to analyze the temporary changes that take place in the amplitude of the photoacoustic signal during the PS growth. The solution of the heat equation takes into account the modulated laser beam, the changes in the reflectance of the PS-backing heterostructure, the electrochemical reaction, and the Joule effect as thermal sources. The model includes the time-dependence of the sample thickness during the electrochemical etching of PS. The changes in the reflectance are identified as the laser reflections in the internal layers of the system. The reflectance is modeled by an additional sinusoidal-monochromatic light source and its modulated frequency is related to the velocity of the PS growth. The chemical reaction and the DC components of the heat sources are taken as an average value from the experimental data. The theoretical results are in agreement with the experimental data and hence provided a method to determine variables of the PS growth, such as the etching velocity and the thickness of the porous layer during the growing process.

  10. Modeling of Fine-Particle Formation in Turbulent Flames

    Science.gov (United States)

    Raman, Venkat; Fox, Rodney O.

    2016-01-01

    The generation of nanostructured particles in high-temperature flames is important both for the control of emissions from combustion devices and for the synthesis of high-value chemicals for a variety of applications. The physiochemical processes that lead to the production of fine particles in turbulent flames are highly sensitive to the flow physics and, in particular, the history of thermochemical compositions and turbulent features they encounter. Consequently, it is possible to change the characteristic size, structure, composition, and yield of the fine particles by altering the flow configuration. This review describes the complex multiscale interactions among turbulent fluid flow, gas-phase chemical reactions, and solid-phase particle evolution. The focus is on modeling the generation of soot particles, an unwanted pollutant from automobile and aircraft engines, as well as metal oxides, a class of high-value chemicals sought for specialized applications, including emissions control. Issues arising due to the numerical methods used to approximate the particle number density function, the modeling of turbulence-chemistry interactions, and model validation are also discussed.

  11. A Thermodynamic Approach to Predict Formation Enthalpies of Ternary Systems Based on Miedema's Model

    Science.gov (United States)

    Mousavi, Mahbubeh Sadat; Abbasi, Roozbeh; Kashani-Bozorg, Seyed Farshid

    2016-07-01

    A novel modification to the thermodynamic semi-empirical Miedema's model has been made in order to provide more precise estimations of formation enthalpy in ternary alloys. The original Miedema's model was modified for ternary systems based on surface concentration function revisions. The results predicted by the present model were found to be in excellent agreement with the available experimental data of over 150 ternary intermetallic compounds. The novel proposed model is capable of predicting formation enthalpies of ternary intermetallics with small discrepancies of ≤20 kJ/mol as well as providing reliable enthalpy variations.

  12. Thermodynamic model of heterochromatin formation through epigenetic regulation

    Science.gov (United States)

    Mulligan, Peter J.; Koslover, Elena F.; Spakowitz, Andrew J.

    2015-02-01

    Gene regulation in eukaryotes requires the segregation of silenced genomic regions into densely packed heterochromatin, leaving the active genes in euchromatin regions more accessible. We introduce a model that connects the presence of epigenetically inherited histone marks, methylation at histone 3 lysine-9, to the physical compaction of chromatin fibers via the binding of heterochromatin protein 1 (HP1). Our model demonstrates some of the key physical features that are necessary to explain experimental observations. In particular, we demonstrate that strong cooperative interactions among the HP1 proteins are necessary to see the phase segregation of heterochromatin and euchromatin regions. We also explore how the cell can use the concentration of HP1 to control condensation and under what circumstances there is a threshold of methylation over which the fibers will compact. Finally, we consider how different potential in vivo fiber structures as well as the flexibility of the histone 3 tail can affect the bridging of HP1. Many of the observations that we make about the HP1 system are guided by general thermodynamics principles and thus could play a role in other DNA organizational processes such as the binding of linker histones.

  13. Dynamic behavior of a social model for opinion formation

    Science.gov (United States)

    Bordogna, Clelia M.; Albano, Ezequiel V.

    2007-12-01

    The dynamic behavior of a social group influenced by both a strong leader and the mass media, which is modeled according to the social impact theory, is studied under two situations: (i) The strong leader changes his/her state of opinion periodically while the mass media are not considered. In this case, the leader is capable of driving the group between a dynamically ordered state with a weak leader-group coupling (high-frequency regime) and a dynamically disordered state where the group follows the opinion of the leader (low-frequency regime). (ii) The mass-media change periodically their message and have to compete with a strong leader that keeps his/her state of opinion unchanged. In this case, the mass media require an amplitude threshold in order to overcome the influence of the leader and drive the system into a dynamically disordered state. The dynamic behavior characteristic of the studied social opinion model shares many features of physical systems that are relevant in the fields of statistical mechanics and condensed matter.

  14. Factors associated with sources, transport, and fate of chloroform and three other trihalomethanes in untreated groundwater used for drinking water

    Science.gov (United States)

    Carter, Janet M.; Moran, Michael J.; Zogorski, John S.; Price, Curtis V.

    2012-01-01

    Multiple lines of evidence for indicating factors associated with the sources, transport, and fate of chloroform and three other trihalomethanes (THMs) in untreated groundwater were revealed by evaluating low-level analytical results and logistic regression results for THMs. Samples of untreated groundwater from wells used for drinking water were collected from 1996-2007 from 2492 wells across the United States and analyzed for chloroform, bromodichloromethane, dibromochloromethane, and bromoform by a low-level analytical method implemented in April 1996. Using an assessment level of 0.02 μg/L, chloroform was detected in 36.5% of public-well samples and 17.6% of domestic-well samples, with most concentrations less than 1 μg/L. Brominated THMs occurred less frequently than chloroform but more frequently in public-well samples than domestic-well samples. For both public and domestic wells, THMs occurred most frequently in urban areas. Logistic regression analyses showed that the occurrence of THMs was related to nonpoint sources such as urban land use and to point sources like septic systems. The frequent occurrence and concentration distribution pattern of THMs, as well as their frequent co-occurrence with other organic compounds and nitrate, all known to have anthropogenic sources, and the positive associations between THM occurrence and dissolved oxygen and recharge indicate the recycling of water that contains THMs and other anthropogenic contaminants.

  15. Static headspace-gas chromatography-mass spectrometry for the simultaneous determination of trihalomethanes and haloacetic acids in canned vegetables.

    Science.gov (United States)

    Cardador, Maria Jose; Gallego, Mercedes

    2016-07-08

    Canned vegetables appear to be a possible exposure pathway for hazardous disinfection by-products due to the use of sanitizers and treated water by the canning industry in the preparation of these foods. This work reports on two static headspace-gas chromatography-mass spectrometry methods for the simultaneous determination of 10 trihalomethanes (THMs) and 13 haloacetic acids (HAAs) in both solid and liquid phases of the canned vegetables. Both methods carry out the whole process (including the leaching of target analytes from the vegetable), derivatization of HAAs and volatilization of THMs and HAA esters, in a single step within a static headspace unit. The methods proposed provide an efficient and simple tool for the determination of regulated disinfection by-products in canned vegetables. Average limits of detection for THMs and HAAs were 0.19 and 0.45μg/kg, respectively, in the solid phase of canned vegetables, and 0.05 and 0.09μg/L, respectively, in the liquid phase. Satisfactory recoveries (90-99%) and precision, calculated as relative standard deviations (RSD≤10%), were obtained in both phases of canned vegetables. The methods proposed were applied for the analysis of frequently-used canned vegetables and confirmed the presence of up to 3 THMs and 5 HAAs at microgram per kilogram or liter levels in both phases of the samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Evaluation of exposure to trihalomethanes in tap water and semen quality: a prospective study in Wuhan, China.

    Science.gov (United States)

    Zeng, Qiang; Chen, Yong-Zhe; Xu, Liang; Chen, Hai-Xia; Luo, Yan; Li, Min; Yue, Jing; Liu, Ai-Lin; Li, Yu-Feng; Lu, Wen-Qing

    2014-07-01

    Trihalomethanes (THMs) have been demonstrated to adversely affect male reproductive health in animals, but the evidence in humans is limited. The study aimed to examine the association between THM exposure and semen quality in a Chinese population. We recruited 324 men from the same water supply district in Wuhan, China between April 2011 and May 2012. Exposure to THMs was evaluated based on their concentrations in tap water measured within 90 days preceding semen collection, the uptake factors of THMs and personal information on ingestion and showering/bathing. We found that TTHM [sum of chloroform (TCM) and brominated THMs (Br-THMs)], TCM and Br-THM uptakes via ingestion were associated with significant or suggestive decreasing trends in sperm concentration (P for trend=0.01, 0.03 and 0.05, respectively) and sperm count (P for trend=0.02, 0.05 and 0.09, respectively). Our results suggest that THM exposure via ingestion may adversely affect semen quality.

  17. Trihalomethanes in drinking water and the risk of death from kidney cancer: does hardness in drinking water matter?

    Science.gov (United States)

    Liao, Yen-Hsiung; Chen, Chih-Cheng; Chang, Chih-Ching; Peng, Chiung-Yu; Chiu, Hui-Fen; Wu, Trong-Neng; Yang, Chun-Yuh

    2012-01-01

    The objectives of this study were to (1) examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of development of kidney cancer and (2) determine whether hardness levels in drinking water modify the effects of TTHM on risk of kidney cancer induction. A matched case-control study was used to investigate the relationship between the risk of death attributed to kidney cancer and exposure to TTHM in drinking water in 53 municipalities in Taiwan. All kidney cancer deaths in the 53 municipalities from 1998 through 2007 were obtained. Controls were deaths from other causes and were pair-matched to the cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on TTHM levels and levels of hardness in drinking water were also collected. The municipality of residence for cancer cases and controls was presumed to be the source of the subject's TTHM and hardness exposure via drinking water. Relative to individuals whose TTHM exposure level was water with a TTHM exposure ≥4.9 ppb. However, evidence of an interaction was noted between the use of soft water and drinking water TTHM concentrations. Increased knowledge of the interaction between hardness and TTHM levels in reducing risk of kidney cancer development will aid in public policy decision and establishing standards to prevent disease occurrence.

  18. Larcform 1 - single column model intercomparison of Arctic air formation, link to model results in NetCDF format

    NARCIS (Netherlands)

    Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, G.J.

    2016-01-01

    Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, not least because they lack or misrepresent physical processes that are specific to high latitudes. The Arctic boundary layer in winter has been observed to be i

  19. Numerical Modeling of Flat Slab Formation in Central Chile

    Science.gov (United States)

    Manea, M.; Perez-Gussinye, M.; Manea, V.; Fernandez, M.

    2009-12-01

    Subduction of oceanic plates beneath large continental masses is a rare process and at present it occurs only along western South America and Central Mexico. Likewise, flat subduction, understood here as where the slab enters at a normal angle and reverses its curvature to flatten at ~70-120 km depth, only occurs at present beneath South America. In general, the angle at which subduction occurs in the depth range of ~100 to ~200 km reflects the balance between negative buoyancy of the slab, elastic resistance of the slab to change the angle of subduction, and non-hydrostatic pressure forces induced by subduction-driven flow within the asthenosphere. The latter force, known as suction force, acts to prevent the slab from sinking into the mantle, and its magnitude increases with increasing subduction velocity, narrowness and viscosity decrease of the mantle wedge [Manea and Gurnis, 2007]. Recent observations show that the upper plate structure varies along the Andean margin, indicating that it is thicker and stronger above flat subduction zones and suggesting a correlation between upper plate structure and subduction angle [Pérez-Gussinyé et al., 2008; Booker et al., 2004]. In this study we use numerical models to explore the extent to which upper plate structure, through its influence on asthenospheric wedge shape and viscosity, can affect the angle of subduction. We test for which upper plate thickness and asthenospheric viscosity repeated cycles of steep and flat subduction are reproduced and compare our results to estimations of lithospheric thickness and the duration of flat and steep subduction cycles hypothesized along the Andean margin. Our models are constrained by realistic plate velocities in hot spot reference frame for both Nazca and South American plates [Muller et al., 2008], the Miocene-Present shortening for the Andes [Schelart et al., 2007] and realistic Nazca plate age distribution [Sdrolias and Muller, 2006]. Using the finite element package

  20. CERIF: The Common European Research Information Format Model

    Directory of Open Access Journals (Sweden)

    Brigitte Jörg

    2010-09-01

    Full Text Available With increased computing power more data than ever are being and will be produced, stored and (re- used. Data are collected in databases, computed and annotated, or transformed by specific tools. The knowledge from data is documented in research publications, reports, presentations, or other types of files. The management of data and knowledge is difficult, and even more complicated is their re-use, exchange, or integration. To allow for quality analysis or integration across data sets and to ensure access to scientific knowledge, additional information - Research Information - has to be assigned to data and knowledge entities. We present the metadata model CERIF to add information to entities such as Publication, Project, Organisation, Person, Product, Patent, Service, Equipment, and Facility and to manage the semantically enhanced relationships between these entities in a formalized way. CERIF has been released as an EC Recommendation to European Member States in 2000. Here, we refer to the latest version CERIF 2008-1.0.

  1. What is the right way to quench star formation in semi-analytic models of galaxy formation?

    Science.gov (United States)

    Luo, Yu; Kang, Xi

    2017-02-01

    Semi-analytic models of galaxy formation are powerful tools to study the evolution of a galaxy population in a cosmological context. However, most models overpredict the number of low-mass galaxies at high redshifts and the colors of model galaxies are not right in the sense that low-mass satellite galaxies are too red and centrals are too blue. The recent version of the L-Galaxies model by Henriques et al. (H15) is a step forward to solve these problems by reproducing the evolution of stellar mass function and the overall fraction of red galaxies. In this paper we compare the two model predictions of L-Galaxies (the other is Guo et al., G13) to SDSS data in detail. We find that in the H15 model the red fraction of central galaxies now agrees with the data due to their implementation of strong AGN feedback, but the stellar mass of centrals in massive halos is now slightly lower than what is indicated by the data. For satellite galaxies, the red fraction of low-mass galaxies (log M*/Mȯ log M*/Mȯ < 11) is slightly bluer. The correct color of centrals and the bluer color of massive satellites indicate that quenching in massive satellites is not strong enough. We also find that there are too many red spirals and less bulge-dominated galaxies in both H15 and G13 models. Our results suggest that additional mechanisms, such as more minor mergers or disk instability, are needed to slightly increase the stellar mass of the central galaxy in massive galaxies, mainly in the bulge component, and bulge dominated galaxies will be quenched not only by minor mergers, but also by some other mechanisms

  2. An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity. II. Mass Dependence of the Star Formation Rate

    CERN Document Server

    Zamora-Avilés, Manuel

    2013-01-01

    In a previous study, we presented a semi-analytical model for the regulation of the star formation rate (SFR) and efficiency (SFE) in which the molecular clouds (MCs) were assumed to be in gravitational collapse, and the SFR was instantaneously controlled by evaporation of the cloud material by massive-star ionization feedback. In this model, the main parameter controlling the evolution of the clouds was found to be the gas mass involved in the process and here we discuss various properties of the SFR and SFE as a function of the cloud masses, that can be compared with observations and implemented in numerical models of galactic evolution. Because the model neglects magnetic fields, supernova explosions, and radiation pressure, the results presented are upper limits. We find that $\\SFRavg$ and $\\SFEavg$ are well represented as functions of the maximum cloud mass by the fits $\\SFRavg \\approx 100 (1+\\Mmax/2 \\times 10^5 ~ \\Msun)^{2} ~ \\Msun \\Myr^{-1}$ and $\\SFEavg \\approx 0.024 (\\Mmax/10^5 ~ \\Msun)^{0.28}$, resp...

  3. Modelling the structural controls of primary kaolinite formation

    Science.gov (United States)

    Tierney, R. L.; Glass, H. J.

    2016-09-01

    An abundance of kaolinite was formed within the St. Austell outcrop of the Cornubian batholith in Cornwall, southwest England, by the hydrous dissolution of feldspar crystals. The permeability of Cornish granites is low and alteration acts pervasively from discontinuity features, with montmorillonite recognised as an intermediate assemblage in partially kaolinised material. Structural features allowed fluids to channel through the impermeable granite and pervade deep into the rock. Areas of high structural control are hypothesised to link well with areas of advanced alteration. As kaolinisation results in a loss of competence, we present a method of utilising discontinuity orientations from nearby unaltered granites alongside the local tectonic history to calculate strain rates and delineate a discrete fracture network. Simulation of the discrete fracture network is demonstrated through a case study at Higher Moor, where kaolinite is actively extracted from a pit. Reconciliation of fracture connectivity and permeability against measured subsurface data show that higher values of modelled properties match with advanced kaolinisation observed in the field. This suggests that the technique may be applicable across various industries and disciplines.

  4. High-Density Spot Seeding for Tissue Model Formation

    Science.gov (United States)

    Marquette, Michele L. (Inventor); Sognier, Marguerite A. (Inventor)

    2016-01-01

    A model of tissue is produced by steps comprising seeding cells at a selected concentration on a support to form a cell spot, incubating the cells to allow the cells to partially attach, rinsing the cells to remove any cells that have not partially attached, adding culture medium to enable the cells to proliferate at a periphery of the cell spot and to differentiate toward a center of the cell spot, and further incubating the cells to form the tissue. The cells may be C2C12 cells or other subclones of the C2 cell line, H9c2(2-1) cells, L6 cells, L8 cells, QM7 cells, Sol8 cells, G-7 cells, G-8 cells, other myoblast cells, cells from other tissues, or stem cells. The selected concentration is in a range from about 1 x 10(exp 5) cells/ml to about 1 x 10(exp 6) cells/ml. The tissue formed may be a muscle tissue or other tissue depending on the cells seeded.

  5. Dividing Streamline Formation Channel Confluences by Physical Modeling

    Directory of Open Access Journals (Sweden)

    Minarni Nur Trilita

    2010-02-01

    Full Text Available Confluence channels are often found in open channel network system and is the most important element. The incoming flow from the branch channel to the main cause various forms and cause vortex flow. Phenomenon can cause erosion of the side wall of the channel, the bed channel scour and sedimentation in the downstream confluence channel. To control these problems needed research into the current width of the branch channel. The incoming flow from the branch channel to the main channel flow bounded by a line distributors (dividing streamline. In this paper, the wide dividing streamline observed in the laboratory using a physical model of two open channels, a square that formed an angle of 30º. Observations were made with a variety of flow coming from each channel. The results obtained in the laboratory observation that the width of dividing streamline flow is influenced by the discharge ratio between the channel branch with the main channel. While the results of a comparison with previous studies showing that the observation in the laboratory is smaller than the results of previous research.

  6. Introducing a more realistic model for opinion formation considering instability in social structure

    Science.gov (United States)

    Salehi, Sajjad; Taghiyareh, Fattaneh

    2016-06-01

    Opinion formation is a process through which interactions of individuals and dynamism of their opinions in effect of neighbors are modeled. In this paper, in an effort to model the opinion formation more realistically, we have introduced a model that considers the role of network structure in opinion dynamics. In this model, each individual changes his opinion in a way so as to decrease its difference with the opinion of trusted neighbors while he intensifies his dissention with the untrusted ones. Considering trust/distrust relations as a signed network, we have defined a structural indicator which shows the degree of instability in social structure and is calculated based on the structural balance theory. It is also applied as feedback to the opinion formation process affecting its dynamics. Our simulation results show formation of a set of clusters containing individuals holding opinions having similar values. Also, the opinion value of each individual is far from the ones of distrusted neighbors. Since this model considers distrust and instability of relations in society, it can offer a more realistic model of opinion formation.

  7. De novo actin polymerization is required for model Hirano body formation in Dictyostelium

    Directory of Open Access Journals (Sweden)

    Yun Dong

    2016-06-01

    Full Text Available Hirano bodies are eosinophilic, actin-rich inclusions found in autopsied brains in numerous neurodegenerative diseases. The mechanism of Hirano body formation is unknown. Mass spectrometry analysis was performed to identify proteins from partially purified model Hirano bodies from Dictyostelium. This analysis identified proteins primarily belonging to ribosomes, proteasomes, mitochondria and cytoskeleton. Profilin, Arp/2/3 and WASH identified by mass spectrometry were found to colocalise with model Hirano bodies. Due to their roles in actin regulation, we selected these proteins for further investigation. Inhibition of the Arp2/3 complex by CK666 prevented formation of model Hirano bodies. Since Arp2/3 activation occurs via the WASH or WAVE complex, we next investigated how these proteins affect Hirano body formation. Whereas model Hirano bodies could form in WASH-deficient cells, they failed to form in cells lacking HSPC300, a member of the WAVE complex. We identified other proteins required for Hirano body formation that include profilin and VASP, an actin nucleation factor. In the case of VASP, both its G- and F-actin binding domains were required for model Hirano body formation. Collectively, our results indicate that de novo actin polymerization is required to form model Hirano bodies.

  8. The Star Formation and AGN luminosity relation: Predictions from a semi-analytical model

    CERN Document Server

    Gutcke, Thales A; Maccio`, Andrea V; Lacey, Cedric

    2015-01-01

    In a Universe where AGN feedback regulates star formation in massive galaxies, a strong correlation between these two quantities is expected. If the gas causing star formation is also responsible for feeding the central black hole, then a positive correlation is expected. If powerful AGNs are responsible for the star formation quenching, then a negative correlation is expected. Observations so far have mainly found a mild correlation or no correlation at all (i.e. a flat relation between star formation rate (SFR) and AGN luminosity), raising questions about the whole paradigm of "AGN feedback". In this paper, we report the predictions of the GALFORM semi-analytical model, which has a very strong coupling between AGN activity and quenching of star formation. The predicted SFR-AGN luminosity correlation appears negative in the low AGN luminosity regime, where AGN feedback acts, but becomes strongly positive in the regime of the brightest AGN. Our predictions reproduce reasonably well recent observations by Rosa...

  9. The Properties of Spiral Galaxies in Semi-Analytic Galaxy Formation Models

    OpenAIRE

    2000-01-01

    We examine the present-day galaxy disk colors and star formation rates (SFRs) in the semi-analytic model of Cole et al. (2000). We find that the fiducial model is a good match to Kennicutt's (1998) observed global star formation law, the color-based metallicity-magnitude correlation and the colors of low-luminosity galaxies. The main limitation of the model, from the point of view of present-day spirals, is that the optical colors of the disks of very luminous spiral galaxies are too blue, ev...

  10. Pattern Formation in Predator-Prey Model with Delay and Cross Diffusion

    Directory of Open Access Journals (Sweden)

    Xinze Lian

    2013-01-01

    Full Text Available We consider the effect of time delay and cross diffusion on the dynamics of a modified Leslie-Gower predator-prey model incorporating a prey refuge. Based on the stability analysis, we demonstrate that delayed feedback may generate Hopf and Turing instability under some conditions, resulting in spatial patterns. One of the most interesting findings is that the model exhibits complex pattern replication: the model dynamics exhibits a delay and diffusion controlled formation growth not only to spots, stripes, and holes, but also to spiral pattern self-replication. The results indicate that time delay and cross diffusion play important roles in pattern formation.

  11. A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells.

    Science.gov (United States)

    Higaki, Takumi; Kutsuna, Natsumaro; Akita, Kae; Takigawa-Imamura, Hisako; Yoshimura, Kenji; Miura, Takashi

    2016-04-01

    Plant leaf epidermal cells exhibit a jigsaw puzzle-like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.

  12. A Model for Ferrite/Pearlite Band Formation and Prevention in Steels

    NARCIS (Netherlands)

    Rivera-Diaz-Del-Castillo, P.E.J.; Sietsma, J.; Van der Zwaag, S.

    2004-01-01

    A model for predicting the conditions under which ferrite/pearlite band formation occurs, and therefore the conditions in which it can be avoided in steels, has been developed. The model requires as input the alloy composition and microchemical segregation wavelength, and provides in turn the homoge

  13. Empirical modeling of soot formation in shock-tube pyrolysis of aromatic hydrocarbons

    Science.gov (United States)

    Frenklach, M.; Clary, D. W.; Matula, R. A.

    1986-01-01

    A method for empirical modeling of soot formation during shock-tube pyrolysis of aromatic hydrocarbons is developed. The method is demonstrated using data obtained in pyrolysis of argon-diluted mixtures of toluene behind reflected shock waves. The developed model is in good agreement with experiment.

  14. A fermented meat model system for studies of microbial aroma formation

    DEFF Research Database (Denmark)

    Tjener, Karsten; Stahnke, Louise Heller; Andersen, L.

    2003-01-01

    A fermented meat model system was developed, by which microbial formation of volatiles could be examined The model was evaluated against dry, fermented sausages with respect to microbial growth, pH and volatile profiles. Fast and slowly acidified sausages and models were produced using the starter......H, microbial growth and volatile profiles was similar to sausage production. Based on these findings, the model system was considered valid for studies of aroma formation of meat cultures for fermented sausage....... for multivariate data analysis. Growth of lactic acid bacteria was comparable for model and sausages, whereas survival of S. xylosus was better in the model. Multivariate analysis of volatiles showed that differences between fast and slowly acidified samples were identical for model and sausage. For both sausage...

  15. Ice Formation in Model Biological Membranes in the Presence of Cryoprotectors

    CERN Document Server

    Kiselev, M A; Kisselev, A M; Ollivon, M

    2000-01-01

    Ice formation in model biological membranes is studied by SAXS and WAXS in the presence of cryoprotectors: dimethyl sulfoxide and glycerol. Three types of phospholipid membranes: DPPC, DMPC, DSPC are chosen for the investigation as well-studied model biological membranes. A special cryostat is used for sample cooling from 14.1C to -55.4C. The ice formation is only detected by WAXS in binary phospholipid/water and ternary phospholipid/cryoprotector/water systems in the condition of excess solvent. Ice formation in a binary phospholipid/water system creates an abrupt decrease of the membrane repeat distance by delta-d, so-called ice-induced dehydration of intermembrane space. The value of delta-d decreases as the cryoprotector concentration increases. The formation of ice does not influence the membrane structure (delta-d = 0) for cryoprotector mole fractions higher than 0.05.

  16. Analytical modeling of gas production rate in tight channel sand formation and optimization of artificial fracture.

    Science.gov (United States)

    Wang, Ruifei; Song, Hongqing; Tang, Hewei; Wang, Yuhe; Killough, John; Huang, Gang

    2016-01-01

    Permeability variation in tight channel sand formation makes an important role in gas production. Based on the features of channel sand formation, a mathematical model has been established considering anisotropy of permeability. The analytical solutions were derived for productivity of both vertical wells and vertically fractured wells. Simulation results show that, gas production rate of anisotropic channel sand formation is less than that of isotropic formation. For vertically fractured well, artificial fracture direction, drainage radius, permeability ratio and fracture half-length have considerable influence on production rate. The optimum fracture direction should be deviated less than π/8 from the maximum permeability direction (or the channel direction). In addition, the analytical model was verified by in situ measured data. The research provides theoretical basis for the development of tight channel sand gas reservoirs.

  17. Semi-numerical simulation of reionization with semi-analytical modeling of galaxy formation

    Institute of Scientific and Technical Information of China (English)

    Jie Zhou; Qi Guo; Gao-Chao Liu; Bin Yue; Yi-Dong Xu; Xue-Lei Chen

    2013-01-01

    In a semi-numerical model of reionization,the evolution of ionization fraction is approximately simulated by the criterion of ionizing photon to baryon ratio.We incorporate a semi-analytical model of galaxy formation based on the Millennium II N-body simulation into the semi-numerical modeling of reionization.The semianalytical model is used to predict the production of ionizing photons,then we use the semi-numerical method to model the reionization process.Such an approach allows more detailed modeling of the reionization,and also connects observations of galaxies at low and high redshifts to the reionization history.The galaxy formation model we use was designed to match the low-z observations,and it also fits the high redshift luminosity function reasonably well,but its prediction about star formation falls below the observed value,and we find that it also underpredicts the stellar ionizing photon production rate,hence the reionization cannot be completed at z ~ 6.We also consider simple modifications of the model with more top heavy initial mass functions,which can allow the reionization to occur at earlier epochs.The incorporation of the semi-analytical model may also affect the topology of the HI regions during the epoch of reionization,and the neutral regions produced by our simulations with the semi-analytical model,which appeared less poriferous than the simple halo-based models.

  18. Natural abiotic formation of oxalic acid in soils: results from aromatic model compounds and soil samples.

    Science.gov (United States)

    Studenroth, Sabine; Huber, Stefan G; Kotte, Karsten; Schöler, Heinz F

    2013-02-05

    Oxalic acid is the smallest dicarboxylic acid and plays an important role in soil processes (e.g., mineral weathering and metal detoxification in plants). We have first proven its abiotic formation in soils and investigated natural abiotic degradation processes based on the oxidation of soil organic matter, enhanced by Fe(3+) and H(2)O(2) as hydroxyl radical suppliers. Experiments with the model compound catechol and further hydroxylated benzenes were performed to examine a common degradation pathway and to presume a general formation mechanism of oxalic acid. Two soil samples were tested for the release of oxalic acid and the potential effects of various soil parameters on oxalic acid formation. Additionally, the soil samples were treated with different soil sterilization methods to prove the oxalic acid formation under abiotic soil conditions. Different series of model experiments were conducted to determine a range of factors including Fe(3+), H(2)O(2), reaction time, pH, and chloride concentration on oxalic acid formation. Under certain conditions, catechol is degraded up to 65.6% to oxalic acid referring to carbon. In serial experiments with two soil samples, oxalic acid was produced, and the obtained results are suggestive of an abiotic degradation process. In conclusion, Fenton-like conditions with low Fe(3+) concentrations and an excess of H(2)O(2) as well as acidic conditions were required for an optimal oxalic acid formation. The presence of chloride reduced oxalic acid formation.

  19. On line contribution functions and examining spectral line formation in 3D model stellar atmospheres

    CERN Document Server

    Amarsi, Anish Mayur

    2015-01-01

    Line contribution functions are useful diagnostics for studying spectral line formation in stellar atmospheres. I derive an expression for the contribution function to the abso- lute flux depression that emerges from three-dimensional box-in-a-star model stellar atmospheres. I illustrate the result by comparing the local thermodynamic equilibrium (LTE) spectral line formation of the high-excitation permitted OI777nm lines with the non-LTE case.

  20. Formation and growth model of B-Al permeation layer of Steel 45

    Institute of Scientific and Technical Information of China (English)

    吉泽升; 李庆芬; 李冬华

    2002-01-01

    The B-Al permeation layers of Steel 45 were studied by means of SEM, TEM and XRD. The formation and growth model of permeation layer was proposed. The layer formation, growth and the migration behaviors of B were discussed. It is suggested that the diffusion of Al is deferred when the surface was covered by borides and aluminize compounds are surrounded by borides with the further growing of borides.

  1. HABIT FORMATION AND PREFERENCE CHANGE IN A TWOSECTOR GROWTH MODEL WITH ELASTIC LABOR SUPPLY

    OpenAIRE

    Zhang, Wei-Bin

    2013-01-01

    The purpose of this study is to develop a two sector growth model with elastic labor supply and preference change. The preference change is influenced by the ideas of time preference and habit formation in the Ramsey-type growth theory. This study deals with interactions among capital accumulation, economic structure, labor supply, labor and capital distribution, habit formation and time preference in an integrated framework. The paper simulates the three autonomous nonlinear differential equ...

  2. Equilibrium Star Formation In A Constant Q Disk: Model Optimisation and Initial Tests

    CERN Document Server

    Zheng, Zheng; Heckman, Timothy; Thilker, David; Zwaan, Martin

    2013-01-01

    We develop a model for the distribution of the ISM and star formation in galaxies based on recent studies that indicate that galactic disks stabilise to a constant stability parameter, which we combine with prescriptions of how the phases of the ISM are determined and for the Star Formation Law (SFL). The model predicts the gas surface mass density and star formation intensity of a galaxy given its rotation curve, stellar surface mass density and the gas velocity dispersion. This model is tested on radial profiles of neutral and molecular ISM surface mass density and star formation intensity of 12 galaxies selected from the THINGS sample. Our tests focus on intermediate radii. Nevertheless, the model produces reasonable agreement with ISM mass and star formation rate integrated over the central region in all but one case. To optimise the model, we evaluate four recipes for the stability parameter, three recipes for apportioning the ISM into molecular and neutral components, and eight versions of the SFL. We f...

  3. A Simple Model for the Relationship Between Star Formation and Surface Density

    CERN Document Server

    Dobbs, C L

    2009-01-01

    We investigate the relationship between the star formation rate per unit area and the surface density of the ISM (the local Kennicutt-Schmitt law) using a simplified model of the ISM and a simple estimate of the star formation rate based on the mass of gas in bound clumps, the local dynamical timescales of the clumps, and an efficiency parameter of around 5 per cent. Despite the simplicity of the approach, we are able to reproduce the observed linear relation between star formation rate and surface density of dense (molecular) gas. We use a simple model for the dependence of H_2 fraction on total surface density to argue why neither total surface density nor the HI surface density are good local indicators of star formation rate. We also investigate the dependence of the star formation rate on the depth of the spiral potential. Our model indicates that the mean star formation rate does not depend significantly on the strength of the spiral potential, but that a stronger spiral potential, for a given mean surf...

  4. Group impressions as dynamic configurations: the tensor product model of group impression formation and change.

    Science.gov (United States)

    Kashima, Y; Woolcock, J; Kashima, E S

    2000-10-01

    Group impressions are dynamic configurations. The tensor product model (TPM), a connectionist model of memory and learning, is used to describe the process of group impression formation and change, emphasizing the structured and contextualized nature of group impressions and the dynamic evolution of group impressions over time. TPM is first shown to be consistent with algebraic models of social judgment (the weighted averaging model; N. Anderson, 1981) and exemplar-based social category learning (the context model; E. R. Smith & M. A. Zárate, 1992), providing a theoretical reduction of the algebraic models to the present connectionist framework. TPM is then shown to describe a common process that underlies both formation and change of group impressions despite the often-made assumption that they constitute different psychological processes. In particular, various time-dependent properties of both group impression formation (e.g., time variability, response dependency, and order effects in impression judgments) and change (e.g., stereotype change and group accentuation) are explained, demonstrating a hidden unity beneath the diverse array of empirical findings. Implications of the model for conceptualizing stereotype formation and change are discussed.

  5. A Bayesian approach to the semi-analytic model of galaxy formation: methodology

    Science.gov (United States)

    Lu, Yu; Mo, H. J.; Weinberg, Martin D.; Katz, Neal

    2011-09-01

    We believe that a wide range of physical processes conspire to shape the observed galaxy population, but we remain unsure of their detailed interactions. The semi-analytic model (SAM) of galaxy formation uses multidimensional parametrizations of the physical processes of galaxy formation and provides a tool to constrain these underlying physical interactions. Because of the high dimensionality, the parametric problem of galaxy formation may be profitably tackled with a Bayesian-inference-based approach, which allows one to constrain theory with data in a statistically rigorous way. In this paper, we develop a SAM in the framework of Bayesian inference. We show that, with a parallel implementation of an advanced Markov chain Monte Carlo algorithm, it is now possible to rigorously sample the posterior distribution of the high-dimensional parameter space of typical SAMs. As an example, we characterize galaxy formation in the current Λ cold dark matter cosmology using the stellar mass function of galaxies as an observational constraint. We find that the posterior probability distribution is both topologically complex and degenerate in some important model parameters, suggesting that thorough explorations of the parameter space are needed to understand the models. We also demonstrate that because of the model degeneracy, adopting a narrow prior strongly restricts the model. Therefore, the inferences based on SAMs are conditional to the model adopted. Using synthetic data to mimic systematic errors in the stellar mass function, we demonstrate that an accurate observational error model is essential to meaningful inference.

  6. Toward a Reduced Complexity Channel Resolving Model for Sedimentary Delta Formation

    Science.gov (United States)

    Liang, M.; Voller, V. R.; Edmonds, D. A.; Paola, C.

    2010-12-01

    Predicting styles of delta growth in restoration areas is a challenge as we try to restore impacted coastlines. Cellular and rule-based reduced complexity models offer a worthwhile means of uncovering key dynamics in delta morphodynamics without the need to fully solve the governing transport equations. In terms of modeling sedimentary delta building processes a critical ingredients is accounting for the formation and bifurcation of channels; phenomena that can be related to the formation of levees and mouth-bars. To that end, we have developed a reduced complexity model that uses a simplified shallow-water solver to study channel formation, mouth bar deposition, and delta development under different forcings. Under the assumption that the flow has a very low Froude Number (Fr2jet. We test the reduced model against flow over Gaussian-shaped bumps of various heights. Comparison of results from this model with results from a full scale commercial code (Delft3D) show a satisfactory agreement on the critical mouth bar height needed to divert flow around the bar. Based on the same diffusive equation, we develop a low-Froude water-routing method for reduced complexity morphodynamics models. The preliminary results show that the method is capable of producing reasonable channel forms and mouth bar formation, and provides a good starting point for development of a channel resolving delta building model.

  7. Including crystal structure attributes in machine learning models of formation energies via Voronoi tessellations

    Science.gov (United States)

    Ward, Logan; Liu, Ruoqian; Krishna, Amar; Hegde, Vinay I.; Agrawal, Ankit; Choudhary, Alok; Wolverton, Chris

    2017-07-01

    While high-throughput density functional theory (DFT) has become a prevalent tool for materials discovery, it is limited by the relatively large computational cost. In this paper, we explore using DFT data from high-throughput calculations to create faster, surrogate models with machine learning (ML) that can be used to guide new searches. Our method works by using decision tree models to map DFT-calculated formation enthalpies to a set of attributes consisting of two distinct types: (i) composition-dependent attributes of elemental properties (as have been used in previous ML models of DFT formation energies), combined with (ii) attributes derived from the Voronoi tessellation of the compound's crystal structure. The ML models created using this method have half the cross-validation error and similar training and evaluation speeds to models created with the Coulomb matrix and partial radial distribution function methods. For a dataset of 435 000 formation energies taken from the Open Quantum Materials Database (OQMD), our model achieves a mean absolute error of 80 meV/atom in cross validation, which is lower than the approximate error between DFT-computed and experimentally measured formation enthalpies and below 15% of the mean absolute deviation of the training set. We also demonstrate that our method can accurately estimate the formation energy of materials outside of the training set and be used to identify materials with especially large formation enthalpies. We propose that our models can be used to accelerate the discovery of new materials by identifying the most promising materials to study with DFT at little additional computational cost.

  8. Constraints on galaxy formation models from the galaxy stellar mass function and its evolution

    CERN Document Server

    Rodrigues, Luiz Felippe S; Bower, Richard

    2016-01-01

    We explore the parameter space of the semi-analytic galaxy formation model GALFORM, studying the constraints imposed by measurements of the galaxy stellar mass function (GSMF) and its evolution. We use the Bayesian Emulator method to quickly eliminate vast implausible volumes of the parameter space and zoom in on the most interesting regions, allowing us to identify a set of models that match the observational data within the model uncertainties. We find that the GSMF strongly constrains parameters related to the quiescent star formation in discs, stellar and AGN feedback and the threshold for disc instabilities, but more weakly restricts other parameters. Constraining the model using the local data alone does not usually select models that match the evolution of the mass function well. Nevertheless, we show that a small subset of models provides an acceptable match to GSMF data out to redshift 1.5, without introducing an explicit redshift dependence of feedback parameters. We explore the physical significanc...

  9. SIMULATION OF NOx FORMATION IN TURBULENT SWIRLING COMBUSTION USING A USM TURBULENCE-CHEMISTRY MODEL

    Institute of Scientific and Technical Information of China (English)

    周力行; 乔丽; 张健

    2003-01-01

    A unified second-order moment (USM) turbulence-chemistry model for simulating NOx formation in turbulent combustion is proposed.All of correlations,including the correlation of the reaction-rate coefficient fluctuation with the concentration fluctuation,are closed by the transport equations in the same form.This model discards the approximation of series expansion of the exponential function or the approximation of using the product of several 1-D PDF's instead of a joint PDF.It is much simpler than other refined models,such as the PDF transport equation model and the conditional moment closure model.The proposed model is used to simulate methane-air swirling turbulent combustion and NOx formation.The prediction results are in good agreement with the experimental results.

  10. A new methodology to test galaxy formation models using the dependence of clustering on stellar mass

    CERN Document Server

    Campbell, David J R; Mitchell, Peter D; Helly, John C; Gonzalez-Perez, Violeta; Lacey, Cedric G; Lagos, Claudia del P; Simha, Vimal; Farrow, Daniel J

    2014-01-01

    We present predictions for the two-point correlation function of galaxy clustering as a function of stellar mass, computed using two new versions of the GALFORM semi-analytic galaxy formation model. These models make use of a new high resolution, large volume N-body simulation, set in the WMAP7 cosmology. One model uses a universal stellar initial mass function (IMF), while the other assumes different IMFs for quiescent star formation and bursts. Particular consideration is given to how the assumptions required to estimate the stellar masses of observed galaxies (such as the choice of IMF, stellar population synthesis model and dust extinction) influence the perceived dependence of galaxy clustering on stellar mass. Broad-band spectral energy distribution fitting is carried out to estimate stellar masses for the model galaxies in the same manner as in observational studies. We show clear differences between the clustering signals computed using the true and estimated model stellar masses. As such, we highligh...

  11. The Romulus Cosmological Simulations: A Physical Approach to the Formation, Dynamics and Accretion Models of SMBHs

    CERN Document Server

    Tremmel, Michael; Governato, Fabio; Volonteri, Marta; Quinn, Tom; Pontzen, Andrew; Anderson, Lauren

    2016-01-01

    We present a novel implementation of supermassive black hole (SMBH) formation, dynamics, and accretion in the massively parallel tree+SPH code, ChaNGa. This approach improves the modeling of SMBHs in fully cosmological simulations, allowing for a more detailed analysis of SMBH-galaxy co-evolution throughout cosmic time. Our scheme includes novel, physically motivated models for SMBH formation, dynamics and sinking timescales within galaxies, and SMBH accretion of rotationally supported gas. The sub-grid parameters that regulate star formation (SF) and feedback from SMBHs and SNe are optimized against a comprehensive set of z = 0 galaxy scaling relations using a novel, multi-dimensional parameter search. We have incorporated our new SMBH implementation and parameter optimization onto a new set of high resolution, large-scale cosmological simulations called Romulus. We present initial results from our flagship simulation, Romulus25, showing that our SMBH model results in SF efficiency, SMBH masses, and global c...

  12. Tundish Open Eye Formation in Inert Gas-Shrouded Tundishes: A Macroscopic Model from First Principles

    Science.gov (United States)

    Chatterjee, Saikat; Chattopadhyay, Kinnor

    2016-10-01

    Open eye formation in tundishes can result in reoxidation of liquid steel leading to the formation of harmful inclusions. Moreover, it is also a site for heat loss, gas absorption, and slag emulsification. All these factors make it necessary to understand the fundamentals of open eye formation, which in turn will allow us to prevent or control its harmful effects. In the present study, the bubble plume regions in a ladle and tundish were compared, and it was observed that there are significant differences between the two. Moreover, a simplistic model for predicting the open eye area in tundishes for `thin slag' practices was derived using the principles of conservation of mass and momentum. The proposed model was able to predict open eye areas in tundish reasonably well and was compared with other models, and experimental results.

  13. Testing anthropic reasoning for the cosmological constant with a realistic galaxy formation model

    CERN Document Server

    Sudoh, Takahiro; Makiya, Ryu; Nagashima, Masahiro

    2016-01-01

    The anthropic principle is one of the possible explanations for the cosmological constant ($\\Lambda$) problem. In previous studies, a dark halo mass threshold comparable with our Galaxy must be assumed in galaxy formation to get a reasonably large probability of finding the observed small value, $P(<$$\\Lambda_{\\rm obs})$, though stars are found in much smaller galaxies as well. Here we examine the anthropic argument by using a semi-analytic model of cosmological galaxy formation, which can reproduce many observations such as galaxy luminosity functions. We calculate the probability distribution of $\\Lambda$ by running the model code for a wide range of $\\Lambda$, while other cosmological parameters and model parameters for baryonic processes of galaxy formation are kept constant. Assuming that the prior probability distribution is flat per unit $\\Lambda$, and that the number of observers is proportional to stellar mass, we find $P(<$$\\Lambda_{\\rm obs}) = 6.7 \\%$ without introducing any galaxy mass thres...

  14. A functional group oxidation model (FGOM for SOA formation and aging

    Directory of Open Access Journals (Sweden)

    X. Zhang

    2013-06-01

    Full Text Available Secondary organic aerosol (SOA formation from a volatile organic compound (VOC involves multiple generations of oxidation that include functionalization and fragmentation of the parent carbon backbone and likely particle-phase oxidation and/or accretion reactions. Despite the typical complexity of the detailed molecular mechanism of SOA formation and aging, a relatively small number of functional groups characterize the oxidized molecules that constitute SOA. Given the carbon number and set of functional groups, the volatility of the molecule can be estimated. We present here a functional group oxidation model (FGOM that represents the process of SOA formation and aging. The FGOM contains a set of parameters that are to be determined by fitting of the model to laboratory chamber data: total organic aerosol concentration, and O : C and H : C atomic ratios. The sensitivity of the model prediction to variation of the adjustable parameters allows one to assess the relative importance of various pathways involved in SOA formation. An analysis of SOA formation from the high- and low-NOx photooxidation of four C12 alkanes (n-dodecane, 2-methylundecane, hexylcyclohexane, and cyclododecane using the FGOM is presented, and comparison with the statistical oxidation model (SOM of Cappa et al. (2013 is discussed.

  15. A Functional Group Oxidation Model (FGOM for SOA formation and aging

    Directory of Open Access Journals (Sweden)

    X. Zhang

    2012-12-01

    Full Text Available Secondary organic aerosol (SOA formation from a volatile organic compound (VOC involves multiple generations of oxidation that include functionalization and fragmentation of the parent carbon backbone and, likely, particle-phase oxidation and/or accretion reactions. Despite the typical complexity of the detailed molecular mechanism of SOA formation and aging, a relatively small number of functional groups characterize the oxidized molecules that constitute SOA. Given the carbon number and set of functional groups, the volatility of the molecule can be estimated. We present here a Functional Group Oxidation Model (FGOM that represents the process of SOA formation and aging. The FGOM contains a set of parameters that are to be determined by fitting of the model to laboratory chamber data: total organic aerosol concentration, and O:C and H:C atomic ratios. The sensitivity of the model prediction to variation of the adjustable parameters allows one to assess the relative importance of various pathways involved in SOA formation. An analysis of SOA formation from the high- and low-NOx photooxidation of four C12 alkanes (n-dodecane, 2-methylundecane, hexylcyclohexane, and cyclododecane using the FGOM is presented, and comparison with the Statistical Oxidation Model (SOM of Cappa et al. (2012 is discussed.

  16. Family support and acceptance, gay male identity formation, and psychological adjustment: a path model.

    Science.gov (United States)

    Elizur, Y; Ziv, M

    2001-01-01

    While heterosexist family undermining has been demonstrated to be a developmental risk factor in the life of persons with same-gender orientation, the issue of protective family factors is both controversial and relatively neglected. In this study of Israeli gay males (N = 114), we focused on the interrelations of family support, family acceptance and family knowledge of gay orientation, and gay male identity formation, and their effects on mental health and self-esteem. A path model was proposed based on the hypotheses that family support, family acceptance, family knowledge, and gay identity formation have an impact on psychological adjustment, and that family support has an effect on gay identity formation that is mediated by family acceptance. The assessment of gay identity formation was based on an established stage model that was streamlined for cross-cultural practice by defining three basic processes of same-gender identity formation: self-definition, self-acceptance, and disclosure (Elizur & Mintzer, 2001). The testing of our conceptual path model demonstrated an excellent fit with the data. An alternative model that hypothesized effects of gay male identity on family acceptance and family knowledge did not fit the data. Interpreting these results, we propose that the main effect of family support/acceptance on gay identity is related to the process of disclosure, and that both general family support and family acceptance of same-gender orientation play a significant role in the psychological adjustment of gay men.

  17. Robust optimization of a mathematical model to design a dynamic cell formation problem considering labor utilization

    Science.gov (United States)

    Vafaeinezhad, Moghadaseh; Kia, Reza; Shahnazari-Shahrezaei, Parisa

    2016-11-01

    Cell formation (CF) problem is one of the most important decision problems in designing a cellular manufacturing system includes grouping machines into machine cells and parts into part families. Several factors should be considered in a cell formation problem. In this work, robust optimization of a mathematical model of a dynamic cell formation problem integrating CF, production planning and worker assignment is implemented with uncertain scenario-based data. The robust approach is used to reduce the effects of fluctuations of the uncertain parameters with regards to all possible future scenarios. In this research, miscellaneous cost parameters of the cell formation and demand fluctuations are subject to uncertainty and a mixed-integer nonlinear programming model is developed to formulate the related robust dynamic cell formation problem. The objective function seeks to minimize total costs including machine constant, machine procurement, machine relocation, machine operation, inter-cell and intra-cell movement, overtime, shifting labors between cells and inventory holding. Finally, a case study is carried out to display the robustness and effectiveness of the proposed model. The tradeoff between solution robustness and model robustness is also analyzed in the obtained results.

  18. New simulation model for bone formation markers in osteoporosis patients treated with once-weekly teriparatide

    Institute of Scientific and Technical Information of China (English)

    Sakae Tanaka; Taiji Adachi; Tatsuhiko Kuroda; Toshitaka Nakamura; Masataka Shiraki; Toshitsugu Sugimoto; Yasuhiro Takeuchi; Mitsuru Saito; John P Bilezikian

    2014-01-01

    Daily 20-mg and once-weekly 56.5-mg teriparatide (parathyroid hormone 1–34) treatment regimens increase bone mineral density (BMD) and prevent fractures, but changes in bone turnover markers differ between the two regimens. The aim of the present study was to explain changes in bone turnover markers using once-weekly teriparatide with a simulation model. Temporary increases in bone formation markers and subsequent decreases were observed during once-weekly teriparatide treatment for 72 weeks. These observations support the hypothesis that repeated weekly teriparatide administration stimulates bone remodeling, replacing old bone with new bone and leading to a reduction in the active remodeling surface. A simulation model was developed based on the iterative remodeling cycle that occurs on residual old bone. An increase in bone formation and a subsequent decrease were observed in the preliminary simulation. For each fitted time point, the predicted value was compared to the absolute values of the bone formation and resorption markers and lumbar BMD. The simulation model strongly matched actual changes in bone turnover markers and BMD. This simulation model indicates increased bone formation marker levels in the early stage and a subsequent decrease. It is therefore concluded that remodeling-based bone formation persisted during the entire treatment period with once-weekly teriparatide.

  19. Influence of roasting on the antioxidant activity and HMF formation of a cocoa bean model systems.

    Science.gov (United States)

    Oliviero, Teresa; Capuano, Edoardo; Cämmerer, Bettina; Fogliano, Vincenzo

    2009-01-14

    During the roasting of cocoa beans chemical reactions lead to the formation of Maillard reaction (MR) products and to the degradation of catechin-containing compounds, which are very abundant in these seeds. To study the modifications occurring during thermal treatment of fat and antioxidant rich foods, such as cocoa, a dry model system was set up and roasted at 180 degrees C for different times. The role played in the formation of MR products and in the antioxidant activity of the system by proteins, catechin, and cocoa butter was investigated by varying the model system formulation. Results showed that the antioxidant activity decreased during roasting, paralleling catechin concentration, thus suggesting that this compound is mainly responsible for the antioxidant activity of roasted cocoa beans. Model system browning was significantly higher in the presence of catechin, which contributed to the formation of water-insoluble melanoidins, which are mainly responsible for browning. HMF concentration was higher in casein-containing systems, and its formation was strongly inhibited in the presence of catechin. No effects related to the degree of lipid oxidation could be observed. Data from model systems obtained by replacing fat with water showed a much lower rate of MR development and catechin degradation but the same inhibitory effect of catechin on HMF formation.

  20. Modeling Mycobacterium tuberculosis early granuloma formation in experimental human lung tissue

    Directory of Open Access Journals (Sweden)

    Venkata Ramanarao Parasa

    2014-02-01

    Full Text Available The widely used animal models for tuberculosis (TB display fundamental differences from human TB. Therefore, a validated model that recapitulates human lung TB is attractive for TB research. Here, we describe a unique method for establishment of TB infection in an experimental human lung tissue model. The model is based on cell lines derived from human lungs and primary macrophages from peripheral blood, and displays characteristics of human lung tissue, including evenly integrated macrophages throughout the epithelium, production of extracellular matrix, stratified epithelia and mucus secretion. Establishment of experimental infection in the model tissue with Mycobacterium tuberculosis, the bacterium that causes TB, resulted in clustering of macrophages at the site of infection, reminiscent of early TB granuloma formation. We quantitated the extent of granuloma formation induced by different strains of mycobacteria and validated our model against findings in other TB models. We found that early granuloma formation is dependent on ESAT-6, which is secreted via the type VII secretion machinery of virulent mycobacteria. Our model, which can facilitate the discovery of the interactions between mycobacteria and host cells in a physiological environment, is the first lung tissue model described for TB.

  1. EPANET water quality model

    Energy Technology Data Exchange (ETDEWEB)

    Rossman, L.A.

    1993-01-01

    EPANET represents a third generation of water quality modeling software developed by the U.S. EPA's Drinking Water Research Division, offering significant advances in the state of the art for network water quality analysis. EPANET performs extended period simulation of hydraulic and water quality behavior within water distribution systems. In addition to substance concentration, water age and source tracing can also be simulated. EPANET includes a full featured hydraulic simulation model that can handle various types of pumps, valves, and their control rules. The water quality module is equipped to handle constituent reactions within the bulk pipe flow and at the pipe wall. It also features an efficient computational scheme that automatically determines optimal time steps and pipe segmentation for accurate tracking of material transport over time. EPANET is currently being used in the US to study such issues as loss of chlorine residual, source blending and trihalomethane (THM) formation, how altered tank operation affects water age, and total dissolved solids (TDS) control for an irrigation network.

  2. Soot formation in a blast furnace - Prediction via a parametric study, using detailed kinetic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Nordstroem, T.; Kilpinen, P.; Hupa, M. [Aabo Akademi, Turku (Finland). Combustion Chemistry Group

    1996-12-31

    The objective of this work has been to investigate the soot formation in a blast furnace fired with heavy fuel oil, using detailed kinetic modelling. This work has been concentrated on parameter studies that could explain under which conditions soot is formed and how that formation could be avoided. The parameters investigated were temperature, pressure, stoichiometric ratio, pyrolysis gas composition and reactor model. The calculations were based on a reaction mechanism that consists of 100 species and 446 reactions including polyaromatic hydrocarbons (PAM) up to 7 aromatic rings SULA 2 Research Programme; 4 refs.

  3. Disinfection by-products of chlorine dioxide (chlorite, chlorate, and trihalomethanes): Occurrence in drinking water in Qatar.

    Science.gov (United States)

    Al-Otoum, Fatima; Al-Ghouti, Mohammad A; Ahmed, Talaat A; Abu-Dieyeh, Mohammed; Ali, Mohammed

    2016-12-01

    The occurrence of chlorine dioxide (ClO2) disinfection by-products (DBPs) in drinking water, namely, chlorite, chlorate, and trihalomethanes (THMs), was investigated. Two-hundred-ninety-four drinking water samples were collected from seven desalination plants (DPs), four reservoirs (R), and eight mosques (M) distributed within various locations in southern and northern Qatar. The ClO2 concentration levels ranged from 0.38 to <0.02 mg L(-1), with mean values of 0.17, 0.12, and 0.04 mg L(-1) for the DPs, Rs, and Ms, respectively. The chlorite levels varied from 13 μg L(-1) to 440 μg L(-1), with median values varying from 13 to 230 μg L(-1), 77-320 μg L(-1), and 85-440 μg L(-1) for the DPs, Rs, and Ms, respectively. The chlorate levels varied from 11 μg L(-1) to 280 μg L(-1), with mean values varying from 36 to 280 μg L(-1), 11-200 μg L(-1), and 11-150 μg L(-1) in the DPs, Rs, and Ms, respectively. The average concentration of THMs was 5 μg L(-1), and the maximum value reached 77 μg L(-1) However, all of the DBP concentrations fell within the range of the regulatory limits set by GSO 149/2009, the World Health Organization (WHO), and Kahramaa (KM).

  4. Occupational Exposure to Trichloramine and Trihalomethanes in Swedish Indoor Swimming Pools: Evaluation of Personal and Stationary Monitoring

    Science.gov (United States)

    Westerlund, Jessica; Graff, Pål; Bryngelsson, Ing-Liss; Westberg, Håkan; Eriksson, Kåre; Löfstedt, Håkan

    2015-01-01

    Introduction: Chlorination is a method commonly used to keep indoor swimming pool water free from pathogens. However, chlorination of swimming pools produces several potentially hazardous by-products as the chlorine reacts with nitrogen containing organic matter. Up till now, exposure assessments in indoor swimming pools have relied on stationary measurements at the poolside, used as a proxy for personal exposure. However, measurements at fixed locations are known to differ from personal exposure. Methods: Eight public swimming pool facilities in four Swedish cities were included in this survey. Personal and stationary sampling was performed during day or evening shift. Samplers were placed at different fixed positions around the pool facilities, at ~1.5 m above the floor level and 0–1 m from the poolside. In total, 52 personal and 110 stationary samples of trichloramine and 51 personal and 109 stationary samples of trihalomethanes, were collected. Results: The average concentration of trichloramine for personal sampling was 71 µg m−3, ranging from 1 to 240 µg m−3 and for stationary samples 179 µg m−3, ranging from 1 to 640 µg m−3. The air concentrations of chloroform were well below the occupational exposure limit (OEL). For the linear regression analysis and prediction of personal exposure to trichloramine from stationary sampling, only data from personal that spent >50% of their workday in the pool area were included. The linear regression analysis showed a correlation coefficient (r 2) of 0.693 and a significant regression coefficient β of 0.621; (95% CI = 0.329–0.912, P = 0.001). Conclusion: The trichloramine exposure levels determined in this study were well below the recommended air concentration level of 500 µg m−3; a WHO reference value based on stationary sampling. Our regression data suggest a relation between personal exposure and area sampling of 1:2, implying an OEL of 250 µg m−3 based on personal sampling. PMID:26155991

  5. Comparison of Spot and Time Weighted Averaging (TWA Sampling with SPME-GC/MS Methods for Trihalomethane (THM Analysis

    Directory of Open Access Journals (Sweden)

    Don-Roger Parkinson

    2016-02-01

    Full Text Available Water samples were collected and analyzed for conductivity, pH, temperature and trihalomethanes (THMs during the fall of 2014 at two monitored municipal drinking water source ponds. Both spot (or grab and time weighted average (TWA sampling methods were assessed over the same two day sampling time period. For spot sampling, replicate samples were taken at each site and analyzed within 12 h of sampling by both Headspace (HS- and direct (DI- solid phase microextraction (SPME sampling/extraction methods followed by Gas Chromatography/Mass Spectrometry (GC/MS. For TWA, a two day passive on-site TWA sampling was carried out at the same sampling points in the ponds. All SPME sampling methods undertaken used a 65-µm PDMS/DVB SPME fiber, which was found optimal for THM sampling. Sampling conditions were optimized in the laboratory using calibration standards of chloroform, bromoform, bromodichloromethane, dibromochloromethane, 1,2-dibromoethane and 1,2-dichloroethane, prepared in aqueous solutions from analytical grade samples. Calibration curves for all methods with R2 values ranging from 0.985–0.998 (N = 5 over the quantitation linear range of 3–800 ppb were achieved. The different sampling methods were compared for quantification of the water samples, and results showed that DI- and TWA- sampling methods gave better data and analytical metrics. Addition of 10% wt./vol. of (NH42SO4 salt to the sampling vial was found to aid extraction of THMs by increasing GC peaks areas by about 10%, which resulted in lower detection limits for all techniques studied. However, for on-site TWA analysis of THMs in natural waters, the calibration standard(s ionic strength conditions, must be carefully matched to natural water conditions to properly quantitate THM concentrations. The data obtained from the TWA method may better reflect actual natural water conditions.

  6. Effect modification of the association between trihalomethanes and pancreatic cancer by drinking water hardness: evidence from an ecological study.

    Science.gov (United States)

    Chiu, Hui-Fen; Tsai, Shang-Shyue; Wu, Trong-Neng; Yang, Chun-Yuh

    2010-07-01

    The objective of this study was to examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of pancreatic cancer and to determine whether calcium (Ca) and magnesium (Mg) levels in drinking water modify the effects of TTHM on risk to develop pancreatic cancer. A matched case-control study was used to investigate the relationship between the risk of death attributed to pancreatic cancer and exposure to TTHM in drinking water in 53 municipalities in Taiwan. All pancreatic cancer deaths in the 53 municipalities from 1998 through 2007 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair matched to the cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on TTHM levels in drinking water were collected from Taiwan Environmental Protection Administration. Information on the levels of Ca and Mg in drinking water was obtained from the Taiwan Water Supply Corporation. The municipality of residence for cancer cases and controls was presumed to be the source of the subject's TTHM, Ca, and Mg exposure via drinking water. Relative to individuals whose TTHM exposure level water with a TTHM exposure > 4.9ppb. There was no evidence of an interaction of drinking water TTHM levels with low Ca intake via drinking water. However, we observed evidence of an interaction between drinking water TTHM concentrations and Mg intake via drinking water. Our findings showed that the correlation between TTHM exposure and risk of pancreatic cancer is influenced by Mg in drinking water. Increased knowledge of the interaction between Mg and TTHM in reducing pancreatic cancer risk will aid in public policy making and standard setting. 2010 Elsevier Inc. All rights reserved.

  7. Trihalomethanes in drinking water and the risk of death from rectal cancer: does hardness in drinking water matter?

    Science.gov (United States)

    Kuo, Hsin-Wei; Chen, Pei-Shih; Ho, Shu-Chen; Wang, Li-Yu; Yang, Chun-Yuh

    2010-01-01

    The objectives of this study were (1) to examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of rectal cancer development and (2) to determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of TTHM on risk of developing rectal cancer. A matched cancer case-control study was used to investigate the relationship between the risk of death attributed to rectal cancer and exposure to TTHM in drinking water in 53 municipalities in Taiwan. All rectal cancer deaths in the 53 municipalities from 1998 through 2007 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on TTHM levels in drinking water were collected from the Taiwan Environmental Protection Administration. Information on the levels of Ca and Mg in drinking water was obtained from the Taiwan Water Supply Corporation. The municipality of residence for cancer cases and controls was presumed to be the source of the subject's TTHM, Ca, and Mg exposure via drinking water. Relative to individuals whose TTHM exposure level was water with a TTHM exposure >or=4.9 ppb. There was no evidence of an interaction of drinking-water TTHM levels with low Ca intake via drinking water. However, evidence of an interaction was noted between drinking-water TTHM concentrations and Mg intake via drinking water. Our findings showed that the correlation between TTHM exposure and risk of rectal cancer is influenced by Mg in drinking water. Increased knowledge of the interaction between Mg and TTHM in reducing rectal cancer risk will aid in public policymaking and standard setting.

  8. Trihalomethanes in drinking water and the risk of death from esophageal cancer: does hardness in drinking water matter?

    Science.gov (United States)

    Tsai, Shang-Shyue; Chiu, Hui-Fen; Yang, Chun-Yuh

    2013-01-01

    The objectives of this study were to (1) examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of esophageal cancer occurrence and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water modify the effects of TTHM on risk to develop esophageal cancer. A matched case-control study was used to investigate the relationship between the risk of death attributed to esophageal cancer and exposure to TTHM in drinking water in 53 municipalities in Taiwan. All esophageal cancer deaths in the 53 municipalities from 2006 through 2010 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on TTHM levels in drinking water were collected from Taiwan Environmental Protection Administration. Information on the levels of Ca and Mg in drinking water was obtained from the Taiwan Water Supply Corporation. The municipality of residence for cancer cases and controls was presumed to be the source of the subject's TTHM, Ca, and Mg exposure via drinking water. Relative to individuals whose TTHM exposure level water with a TTHM exposure ≥4.9 ppb. There was evidence of an interaction between drinking-water TTHM levels and low Ca and Mg intake. Our findings showed that the correlation between TTHM exposure and risk of esophageal cancer development was influenced by Ca and Mg levels in drinking water. This is the first study to report effect modification by Ca and Mg intake from drinking water on the correlation between TTHM exposure and risk of esophageal cancer occurrence. Increased knowledge of the interaction between Ca, Mg, and TTHM in reducing risk of esophageal cancer development will aid in public policymaking and standard setting for drinking

  9. Formation of disinfection byproducts in typical Chinese drinking water

    Institute of Scientific and Technical Information of China (English)

    Wenbo Liu; Yanmei Zhao; Christopher WK Chow; Dongsheng Wang

    2011-01-01

    Eight typical drinking water supplies in China were selected in this study.Both source and tap water were used to investigate the occurrence of chlorinated disinfection byproducts (DBPs), and seasonal variation in the concentrations of trihalomethanes (THMs) of seven water sources was compared.The results showed that the pollution level for source water in China, as shown by DBP formation potential, was low.The most encountered DBPs were chloroform, dichloroacetic acid, trichloroacetic acid, and chiorodibromoacetic acid.The concentration of every THMs and haloacetic acid (HAA) compound was under the limit of standards for drinking water quality.The highest total THMs concentrations were detected in spring.

  10. Formation of disinfection byproducts in typical Chinese drinking water.

    Science.gov (United States)

    Liu, Wenbo; Zhao, Yanmei; Chow, Christopher W K; Wang, Dongsheng

    2011-01-01

    Eight typical drinking water supplies in China were selected in this study. Both source and tap water were used to investigate the occurrence of chlorinated disinfection byproducts (DBPs), and seasonal variation in the concentrations of trihalomethanes (THMs) of seven water sources was compared. The results showed that the pollution level for source water in China, as shown by DBP formation potential, was low. The most encountered DBPs were chloroform, dichloroacetic acid, trichloroacetic acid, and chlorodibromoacetic acid. The concentration of every THMs and haloacetic acid (HAA) compound was under the limit of standards for drinking water quality. The highest total THMs concentrations were detected in spring.

  11. Evolution Methods of Formation of Neuronet Models of Complex Economic Systems

    Directory of Open Access Journals (Sweden)

    Khemelyov Oleksandr H.

    2014-01-01

    Full Text Available The article analyses principles of formation of neuronet models of complex economic systems. It justifies prospectiveness of use of artificial intellect methods when modelling complex economic systems. It shows a possibility of use of evolution methods when forming neuronet models of complex economic systems for ensuring invariance of their generalising properties. It offers an algorithm with a genome from operons of fixed length. It considers all operons from the point of view of functional positions. It notes a specific feature of the algorithm, which allows excluding anthropogenic factors when selecting the neuronet models architecture. It proves adequacy of the formed neuronet models of complex economic systems.

  12. A Morphologically Structured Model for Mycelial Growth and Secondary Metabolite Formation

    Institute of Scientific and Technical Information of China (English)

    刘刚; 徐志南; 岑沛霖

    2000-01-01

    A morphologically structured model is proposed to describe the batch fermentation of lovastatin according to the growth kinetics of filamentous microorganisms. Three kinds of hyphae are considered in the model:actively growing hyphae, non-growing hyphae and deactivated hyphae. Furthermore, actively growing hyphae consist of three morphological compartments: apical compartment which gives rise to hyphal tip extension; subapical compartment which is related to hyphal branching; and hyphal compartment which is only responsible for secondary metabolite formation. The kinetics of mycelial growth mechanism is summarized and applied in modeling lovastatin fermentation. A Michaelis-Menten kinetic model with substrate inhibition is proposed for product formation. As expected, the model simulations fit well with experimental data obtained either from a laboratory scale 10 L fermenter or from a vilot-vlant scale fermenter.

  13. A Bayesian approach to the semi-analytic model of galaxy formation: methodology

    CERN Document Server

    Lu, Yu; Weinberg, Martin D; Katz, Neal S

    2010-01-01

    We believe that a wide range of physical processes conspire to shape the observed galaxy population but we remain unsure of their detailed interactions. The semi-analytic model (SAM) of galaxy formation uses multi-dimensional parameterizations of the physical processes of galaxy formation and provides a tool to constrain these underlying physical interactions. Because of the high dimensionality, the parametric problem of galaxy formation may be profitably tackled with a Bayesian-inference based approach, which allows one to constrain theory with data in a statistically rigorous way. In this paper, we develop a generalized SAM using the framework of Bayesian inference. We show that, with a parallel implementation of an advanced Markov-Chain Monte-Carlo algorithm, it is now possible to rigorously sample the posterior distribution of the high-dimensional parameter space of typical SAMs. As an example, we characterize galaxy formation in the current $\\Lambda$CDM cosmology using stellar mass function of galaxies a...

  14. Formation and Inhibition of Nε-(Carboxymethyllysine in Saccharide-Lysine Model Systems during Microwave Heating

    Directory of Open Access Journals (Sweden)

    Bing Li

    2012-10-01

    Full Text Available  Nε-(carboxymethyl lysine (CML is the most abundant advanced glycation end product (AGE, and frequently selected as an AGEs marker in laboratory studies. In this paper, the formation and inhibition of Nε-(carboxymethyllysine in saccharide-lysine model systems during microwave heating have been studied. The microwave heating treatment significantly promoted the formation of CML during Maillard reactions, which was related to the reaction temperature, time and type of saccharide. The order of CML formation for different saccharides was lactose > glucose > sucrose. Then, the inhibition effect on CML by five inhibitors was further examined. According to the results, ascorbic acid and tocopherol did not affect inhibition of CML, in contrast, thiamin, rutin and quercetin inhibited CML formation, and the inhibitory effects were concentration dependent.

  15. Advanced air quality modeling system for the simulation of photochemical ozone formation over North Carolina

    Energy Technology Data Exchange (ETDEWEB)

    Jang, C.; Wheeler, N.; Dolwick, P.; Olerud, D.; Houyoux, M. [MCNC-North Carolina Supercomputing Center, Research Triangle Park, NC (United States); Timin, B.; Lawrimore, J.; Holman, S. [North Carolina Dept. of Environment and Natural Resources, Raleigh, NC (United States). Div. of Air Quality; Jeffries, H. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Environmental Sciences and Engineering

    1998-12-31

    An advanced air quality modeling system is used to simulate the formation of photochemical oxidants, mainly ozone, over North Carolina. The objective of this modeling study is to successfully model the formation processes of ozone in North Carolina to lead to effective ozone control strategy developments for both 1-hour and 8-hour standards and eventually to address the particulate matter issue. The modeling system selected for this ongoing project is the North Carolina Supercomputing Center`s Environmental Decision Support System (EDSS), which evolved from a working prototype of EPA`s Third Generation Modeling System, or Models-3. The EDSS consists of three major modeling components : the Multiscale Air Quality SImulation Platform (MAQSIP) for chemistry/transport modeling, Mesoscale Model Version 5 (MM5) for meteorological modeling, and Sparse Matrix Operator Kernel Emissions (SMOKE) system for emission modeling. Two inner subdomains at 12-km and 4-km grid resolutions centered over Charlotte are nested inside a coarse domain at a 36-km resolution. Sixteen vertical layers with a denser grid at lower altitude are used to better resolve the mixing layer. The CB-IV chemistry mechanism with updated isoprene chemistry and radical-radical reactions is used to simulate the chemical transformations of reacting species. Preliminary results show that the MAQSIP has reasonably simulated the temporal and spatial distribution of ozone as compared to observations in the first 6-day episode during July 10--15, 1995. Improved ozone predictions are shown in the model using finer grid resolution. Various ozone sensitivity studies on the model inputs such as initial and boundary conditions and the existence of clouds are under testing. An innovative analysis tool for model evaluation and error detection, the Process Analysis method, is also applied to help understand the regulating processes that lead to formation of ozone.

  16. MODELING OF 'BANDING' MICROSTRUCTURE FORMATION IN CENTRIFUGALLY SOLIDIFIED Ti-6Al-4V ALLOY

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Numerical investigations of the 'banding' microstructure formation during solidifica-tion of Ti-6Al-4V alloy in the centrifugal casting are conducted using a multi-scale model, which combines the finite difference method (FDM) at the macroscale with a cellular automaton (CA) model at the microscale. The macro model is used to simu-late the fluid flow and heat transfer throughout the casting. The micro model is used to predict the nucleation and growth of microstructures. With the proposed model,numerical simulations are performed to study the influences of the nucleation density,mould rotation speed, and casting size upon the 'banding' microstructure formation. It is noted that changing the nucleation density has a minor effect on the microstructure formation. The rotation speed promotes the formation of 'banding' microstructure,which is more noticeable for larger size castings. The major mechanism responsi-ble for this 'banding' phenomenon is the spatial variation in cooling rates created by centrifugal force.

  17. Rodent animal models of delayed bone healing and non-union formation: a comprehensive review

    Directory of Open Access Journals (Sweden)

    P Garcia

    2013-07-01

    Full Text Available Despite the growing knowledge on the mechanisms of fracture healing, delayed healing and non-union formation remain a major clinical challenge. Animal models are needed to study the complex process of normal and impaired fracture healing and to develop new therapeutic strategies. Whereas in the past mainly large animals have been used to study normal and impaired fracture healing, nowadays rodent models are of increasing interest. New osteosynthesis techniques for rat and mice have been developed during the last years, which allowed for the first time stable osteosynthesis in these animals comparable to the standards in large animals and humans. Based on these new implants, different models in rat and mice have been established to study delayed healing and non-union formation. Although in humans the terms delayed union and non-union are well defined, in rodents definitions are lacking. However, especially in scientific studies clear definitions are necessary to develop a uniform scientific language and allow comparison of the results between different studies. In this consensus report, we define the basic terms “union”, “delayed healing” and “non-union” in rodent animal models. Based on a review of the literature and our own experience, we further provide an overview on available models of delayed healing and non-union formation in rats and mice. We further summarise the value of different approaches to study normal and delayed fracture healing as well as non-union formation, and discuss different methods of data evaluation.

  18. Application of Thermal Modelling for Geochemical Characterization of Gadvan Formation, Persian Gulf, Iran

    Directory of Open Access Journals (Sweden)

    Ahmad Vaezian

    2014-12-01

    Full Text Available In the this research, the hydrocarbon generation potential of the Gadvan Formation as a probable source rock was investigated in the central part of the Persian Gulf at the borders of Iran. Type and maturity level of kerogen were investigated in six wells using the results of Rock-Eval pyrolysis and compared with results yielded by the modelling software program known as Pars Basin Modeler (PBM. The cross-plot of hydrogen index (HI versus maximum temperature suggests that the Gadvan Formation reached early to mid-maturity stages in the studied area, which means that it could act as a gas prone source rock. Furthermore, the burial and thermal history of the Gadvan Formation was determined in one well. Two methods, Easy %Ro and time-temperature index (TTI were used for the reconstruction of thermal modelling and studying the thermal maturity level in all of the drilled wells reaching the Gadvan Formation. The results of the TTI and Easy %Ro methods were in good agreement and both of confirmed the results of Rock Eval analysis. An integrated approach using different techniques showed that the Gadvan Formation can be classified as a poor gas bearing source rock in the studied area, while its maturity increases towards the southern parts of the Persian Gulf.

  19. Parametric studies of contrail ice particle formation in jet regime using microphysical parcel modeling

    Directory of Open Access Journals (Sweden)

    H.-W. Wong

    2010-04-01

    Full Text Available Condensation trails (contrails formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age <5 s, systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a microphysical parcel modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index >1×1015 (kg-fuel−1 at cruise. The effects of dilution history, ion-mediated nucleation, ambient relative humidity, fuel sulfur contents, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles in the soot-rich regime, and the effect of fuel sulfur contents is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles. Further modeling and experimental studies are needed to verify if our findings can provide a possible approach for contrail mitigation.

  20. A review of mathematical models for the formation of vascular networks

    KAUST Repository

    Scianna, M.

    2013-09-01

    Two major mechanisms are involved in the formation of blood vasculature: vasculogenesis and angiogenesis. The former term describes the formation of a capillary-like network from either a dispersed or a monolayered population of endothelial cells, reproducible also in vitro by specific experimental assays. The latter term describes the sprouting of new vessels from an existing capillary or post-capillary venule. Similar mechanisms are also involved in the formation of the lymphatic system through a process generally called lymphangiogenesis. A number of mathematical approaches have been used to analyze these phenomena. In this paper, we review the different types of models, with special emphasis on their ability to reproduce different biological systems and to predict measurable quantities which describe the overall processes. Finally, we highlight the advantages specific to each of the different modelling approaches. © 2013 Elsevier Ltd.

  1. Automata networks model for alignment and least effort on vocabulary formation

    CERN Document Server

    Vera, Javier; Goles, Eric

    2015-01-01

    Can artificial communities of agents develop language with scaling relations close to the Zipf law? As a preliminary answer to this question, we propose an Automata Networks model of the formation of a vocabulary on a population of individuals, under two in principle opposite strategies: the alignment and the least effort principle. Within the previous account to the emergence of linguistic conventions (specially, the Naming Game), we focus on modeling speaker and hearer efforts as actions over their vocabularies and we study the impact of these actions on the formation of a shared language. The numerical simulations are essentially based on an energy function, that measures the amount of local agreement between the vocabularies. The results suggests that on one dimensional lattices the best strategy to the formation of shared languages is the one that minimizes the efforts of speakers on communicative tasks.

  2. A semi-analytical model for exploring Galilean satellites formation from a massive disk

    CERN Document Server

    Miguel, Yamila

    2015-01-01

    A better knowledge of Jovian satellites' origins will bring light on the environment that surrounded Jupiter during its formation and can help us to understand the characteristics of this unique satellite system. We developed a semi-analytical model to investigate Jupiter's regular satellite formation and present the results of our population synthesis calculations. We performed simulations adopting a massive, static, low-viscosity circumplanetary disk model, in agreement with a current study of magnetorotational instability in a circum-planetary disk. We find that the high gas density leads to very rapid migration of satellitesimals due to gas drag and type II migration of satellites in a faster disk-dominated mode. A large concentration of solids, large building blocks and longer type II migration time-scales favor formation and survival of large satellites. However, bodies as massive as Ganymede and those located far away from Jupiter, such as Callisto, are difficult to form with this scenario.

  3. A fermented meat model system for studies of microbial aroma formation

    DEFF Research Database (Denmark)

    Tjener, Karsten; Stahnke, Louise Heller; Andersen, L.

    2003-01-01

    A fermented meat model system was developed, by which microbial formation of volatiles could be examined The model was evaluated against dry, fermented sausages with respect to microbial growth, pH and volatile profiles. Fast and slowly acidified sausages and models were produced using the starte......H, microbial growth and volatile profiles was similar to sausage production. Based on these findings, the model system was considered valid for studies of aroma formation of meat cultures for fermented sausage.......A fermented meat model system was developed, by which microbial formation of volatiles could be examined The model was evaluated against dry, fermented sausages with respect to microbial growth, pH and volatile profiles. Fast and slowly acidified sausages and models were produced using the starter...... cultures Pediococcus pentosaceus and Staphylococcus xylosus. Volatiles were collected and analysed by dynamic headspace sampling and GC MS. The analysis was primarily focused on volatiles arising from amino acid degradation and a total of 24 compounds, of which 19 were quantified, were used...

  4. Study of Swarm Behavior in Modeling and Simulation of Cluster Formation in Nanofluids

    Directory of Open Access Journals (Sweden)

    Mohammad Pirani

    2013-01-01

    Full Text Available Modeling the multiagents cooperative systems inspired from biological self-organized systems in the context of swarm model has been under great considerations especially in the field of the cooperation of multi robots. These models are trying to optimize the behavior of artificial multiagent systems by introducing a consensus, which is a mathematical model between the agents as an intelligence property for each member of the swarm set. The application of this novel approach in the modeling of nonintelligent multi agents systems in the field of cohesion and cluster formation of nanoparticles in nanofluids has been investigated in this study. This goal can be obtained by applying the basic swarm model for agents that are more mechanistic by considering their physical properties such as their mass, diameter, as well as the physical properties of the flow. Clustering in nanofluids is one of the major issues in the study of its effects on heat transfer. Study of the cluster formation dynamics in nanofluids using the swarm model can be useful in controlling the size and formation time of the clusters as well as designing appropriate microchannels, which the nanoparticles are plunged into.

  5. Analysis of Computational Models of Shaped Charges for Jet Formation and Penetration

    Science.gov (United States)

    Haefner, Jonah; Ferguson, Jim

    2016-11-01

    Shaped charges came into use during the Second World War demonstrating the immense penetration power of explosively formed projectiles and since has become a tool used by nearly every nation in the world. Penetration is critically dependent on how the metal liner is collapsed into a jet. The theory of jet formation has been studied in depth since the late 1940s, based on simple models that neglect the strength and compressibility of the metal liner. Although attempts have been made to improve these models, simplifying assumptions limit the understanding of how the material properties affect the jet formation. With a wide range of material and strength models available for simulation, a validation study was necessary to guide code users in choosing models for shaped charge simulations. Using PAGOSA, a finite-volume Eulerian hydrocode designed to model hypervelocity materials and strong shock waves developed by Los Alamos National Laboratory, and experimental data, we investigated the effects of various equations of state and material strength models on jet formation and penetration of a steel target. Comparing PAGOSA simulations against modern experimental data, we analyzed the strengths and weaknesses of available computational models. LA-UR-16-25639 Los Alamos National Laboratory.

  6. Antioxidants Inhibit Formation of 3-Monochloropropane-1,2-diol Esters in Model Reactions.

    Science.gov (United States)

    Li, Chang; Jia, Hanbing; Shen, Mingyue; Wang, Yuting; Nie, Shaoping; Chen, Yi; Zhou, Yongqiang; Wang, Yuanxing; Xie, Mingyong

    2015-11-11

    The capacities of six antioxidants to inhibit the formation of 3-monochloropropane-1,2 diol (3-MCPD) esters were examined in this study. Inhibitory capacities of the antioxidants were investigated both in chemical models containing the precursors (tripalmitoyl glycerol, 1,2-dipalmitoyl-sn-glycerol, monopalmitoyl glycerol, and sodium chloride) of 3-MCPD esters and in oil models (rapeseed oil and sodium chloride). Six antioxidants, butylated hydroxytoluene (BHT), butylated hydroxy anisole (BHA), tert-butyl hydroquinone (TBHQ), propyl gallate (PG), L-ascorbyl palmitate (AP), and α-tocopherol (VE), were found to exhibit inhibiting capacities on 3-MCPD ester formation both in chemical models and in oil models. TBHQ provided the highest inhibitory capacity both in chemical models and in oil models; 44% of 3-MCPD ester formation was inhibited in the presence of TBHQ (66 mg/kg of oil) after heating of rapeseed oil at 230 °C for 30 min, followed by PG and AP. BHT, BHA, and VE appeared to have weaker inhibitory abilities in both models. VE exhibited the lowest inhibition rate; 22% of 3-MCPD esters were inhibited in the presence of VE (172 mg/kg of oil) after heating of rapeseed oil at 230 °C for 30 min. In addition, the inhibition rates of PG and VE decreased dramatically with an increase in temperature or heating time. The results suggested that some antioxidants, such as TBHQ, PG, and AP, could be the potential inhibitors of 3-MCPD esters in practice.

  7. Investigación de trihalometanos en agua potable del Estado Carabobo, Venezuela Trihalomethanes in the drinking water of Carabobo State, Venezuela

    Directory of Open Access Journals (Sweden)

    A. Sarmiento

    2003-04-01

    Full Text Available Objetivo: La desinfección del agua con cloro en las plantas de potabilización da lugar a la formación de trihalometanos (THM. Estos compuestos están asociados a efectos adversos para la salud. En este estudio se determinó la concentración de THM en el agua para consumo humano suministrada por las redes de distribución de los dos principales sistemas de potabilización de agua del Estado Carabobo, la planta Alejo Zuloaga y el embalse Pao-Cachinche que forman el Sistema Regional del Centro I (SRC-I y la planta Lucio Baldo Soules y el embalse Pao-La Balsa que forman el Sistema Regional del Centro II (SRC-II. Métodos: Se analizaron un total de 144 muestras recolectadas durante 6 muestreos que se realizaron durante los años 2000 y 2001. La concentración de THM se determinó por cromatografía de gases, mediante la técnica de headspace. Se determinaron las concentraciones para los siguientes THM: cloroformo (CHCl3, bromoformo (CHBr3, dibromoclorometano (CHBr2Cl y diclorobromometano (CHCl2Br. Resultados: La concentración de THM totales estuvo entre 47,84 y 93,23 μg/l. El CHCl3 fue el compuesto predominante, representando el 83% de total de THM para el SRC-I y el 82% en el SRC-II. Se encontró que las concentraciones de THM totales en el SRC-I (Red Baja y Red San Diego son significativamente superiores (p Objective: Disinfection of water with chlorine in water treatment plants leads to the formation of trihalomethanes (THMs. These compounds are associated with adverse health effects. The aim of this study was to analyze THM concentrations in the water provided for human consumption in the two main water treatment systems of Carabobo State: the Alejo Zuloaga plant and the Pao-Cachinche reservoir, which form the Central Regional System I (CRS I, and the Lucio Baldo Soules plant and the Pao-La Balsa reservoir, which form the Central Regional System II (CRS II. Methods: We analyzed 144 water samples collected in 6 samplings carried out in 2000

  8. Modeling secondary organic aerosol formation through cloud processing of organic compounds

    Directory of Open Access Journals (Sweden)

    J. Chen

    2007-06-01

    Full Text Available Interest in the potential formation of secondary organic aerosol (SOA through reactions of organic compounds in condensed aqueous phases is growing. In this study, the potential formation of SOA from irreversible aqueous-phase reactions of organic species in clouds was investigated. A new proposed aqueous-phase chemistry mechanism (AqChem is coupled with the existing gas-phase Caltech Atmospheric Chemistry Mechanism (CACM and the Model to Predict the Multiphase Partitioning of Organics (MPMPO that simulate SOA formation. AqChem treats irreversible organic reactions that lead mainly to the formation of carboxylic acids, which are usually less volatile than the corresponding aldehydic compounds. Zero-dimensional model simulations were performed for tropospheric conditions with clouds present for three consecutive hours per day. Zero-dimensional model simulations show that 48-h averaged SOA formation are increased by 27% for a rural scenario with strong monoterpene emissions and 7% for an urban scenario with strong emissions of aromatic compounds, respectively, when irreversible organic reactions in clouds are considered. AqChem was also incorporated into the Community Multiscale Air Quality Model (CMAQ version 4.4 with CACM/MPMPO and applied to a previously studied photochemical episode (3–4 August 2004 focusing on the eastern United States. The CMAQ study indicates that the maximum contribution of SOA formation from irreversible reactions of organics in clouds is 0.28 μg m−3 for 24-h average concentrations and 0.60 μg m−3 for one-hour average concentrations at certain locations. On average, domain-wide surface SOA predictions for the episode are increased by 8.6% when irreversible, in-cloud processing of organics is considered.

  9. Opinion formation model for markets with a social temperature and fear.

    Science.gov (United States)

    Krause, Sebastian M; Bornholdt, Stefan

    2012-11-01

    In the spirit of behavioral finance, we study the process of opinion formation among investors using a variant of the two-dimensional voter model with a tunable social temperature. Further, a feedback acting on the temperature is introduced, such that social temperature reacts to market imbalances and thus becomes time dependent. In this toy market model, social temperature represents nervousness of agents toward market imbalances representing speculative risk. We use the knowledge about the discontinuous generalized voter model phase transition to determine critical fixed points. The system exhibits metastable phases around these fixed points characterized by structured lattice states, with intermittent excursions away from the fixed points. The statistical mechanics of the model is characterized, and its relation to dynamics of opinion formation among investors in real markets is discussed.

  10. Opinion formation model for markets with a social temperature and fear

    Science.gov (United States)

    Krause, Sebastian M.; Bornholdt, Stefan

    2012-11-01

    In the spirit of behavioral finance, we study the process of opinion formation among investors using a variant of the two-dimensional voter model with a tunable social temperature. Further, a feedback acting on the temperature is introduced, such that social temperature reacts to market imbalances and thus becomes time dependent. In this toy market model, social temperature represents nervousness of agents toward market imbalances representing speculative risk. We use the knowledge about the discontinuous generalized voter model phase transition to determine critical fixed points. The system exhibits metastable phases around these fixed points characterized by structured lattice states, with intermittent excursions away from the fixed points. The statistical mechanics of the model is characterized, and its relation to dynamics of opinion formation among investors in real markets is discussed.

  11. Opinion formation model for markets with a social temperature and fear

    CERN Document Server

    Krause, Sebastian M; 10.1103/PhysRevE.86.056106

    2012-01-01

    In the spirit of behavioral finance, we study the process of opinion formation among investors using a variant of the 2D Voter Model with a tunable social temperature. Further, a feedback acting on the temperature is introduced, such that social temperature reacts to market imbalances and thus becomes time dependent. In this toy market model, social temperature represents nervousness of agents towards market imbalances representing speculative risk. We use the knowledge about the discontinuous Generalized Voter Model phase transition to determine critical fixed points. The system exhibits metastable phases around these fixed points characterized by structured lattice states, with intermittent excursions away from the fixed points. The statistical mechanics of the model is characterized and its relation to dynamics of opinion formation among investors in real markets is discussed.

  12. A collective opinion formation model under Bayesian updating and confirmation bias

    CERN Document Server

    Nishi, Ryosuke

    2013-01-01

    We propose a collective opinion formation model with a so-called confirmation bias. The confirmation bias is a psychological effect with which, in the context of opinion formation, an individual in favor of an opinion is prone to misperceive new incoming information as supporting the current belief of the individual. Our model modifies a Bayesian decision-making model for single individuals (Rabin and Schrag, Q. J. Econ. 114, 37 (1999)) to the case of a well-mixed population of interacting individuals in the absence of the external input. We numerically simulate the model to show that all the agents eventually agree on one of the two opinions only when the confirmation bias is weak. Otherwise, the stochastic population dynamics ends up creating a disagreement configuration (also called polarization), particularly for large system sizes. A strong confirmation bias allows various final disagreement configurations with different fractions of the individuals in favor of the opposite opinions.

  13. Dynamic WTA optimization model of air defense operation of warships' formation

    Institute of Scientific and Technical Information of China (English)

    Li Jinjun; Cong Rong; Xiong Jiguang

    2006-01-01

    WTA (weapon-target allocation) of air defense operation is a very complicated problem and current models focus on static and restricted WTA problem mostly. Based on the dynamic characteristics of air defense operational command and decision of warships' formation, a dynamic WTA model is established. Simulation results show that switch fire and repetition fire of anti-air weapon systems affect the result of the air defense operation remarkably and the dynamic model is more satisfying than static ones. Related results are gained based on the analysis of the simulation results and the results are accordant with the intuitionistic tactical judgment. The model is some reference for the research of air defense C3I system of warships' formation.

  14. LES study of intermittency in soot formation in a model aircraft combustor

    Science.gov (United States)

    Koo, Heeseok; Raman, Venkat; Mueller, Michael; Geigle, Klaus Peter

    2015-11-01

    Intermittent soot formation is one of the modeling challenges that prevent accurate predictions of soot concentration in a turbulent reacting flow. Due to the highly unsteady and irregular sooting behavior, formation of soot is acutely sensitive to the flow and gas phase history. Therefore, we need to accurately capture interactions between soot chemistry, particle dynamics, and turbulent flame as well as the turbulent reacting flow. In this study, large eddy simulation (LES) is used to understand the model sensitivity to the soot prediction. Hybrid method of moment (HMOM) soot model is used that accommodates detailed process of soot particle and soot precursor evolution. Gas phase chemistry uses flamelet progress variable approach with an additional enthalpy dimension to include soot radiation effect. The developed numerical model is tested on the DLR swirl combustor that emulates the rich-quench-lean (RQL) configuration using secondary oxidation air injection.

  15. Asymptotic Analysis in a Gas-Solid Combustion Model with Pattern Formation

    Institute of Scientific and Technical Information of China (English)

    Claude-Michel BRAUNER; Lina HU; Luca LORENZI

    2013-01-01

    The authors consider a free interface problem which stems from a gas-solid model in combustion with pattern formation.A third-order,fully nonlinear,self-consistent equation for the flame front is derived.Asymptotic methods reveal that the interface approaches a solution to the Kuramoto-Sivashinsky equation.Numerical results which illustrate the dynamics are presented.

  16. A new model for the computation of the formation factor of core rocks

    Science.gov (United States)

    Beltrán, A.; Chávez, O.; Zaldivar, J.; Godínez, F. A.; García, A.; Zenit, R.

    2017-04-01

    Among all the rock parameters measured by modern well logging tools, the formation factor is essential because it can be used to calculate the volume of oil- and/or gas in wellsite. A new mathematical model to calculate the formation factor is analytically derived from first principles. Given the electrical properties of both rock and brine (resistivities) and tortuosity (a key parameter of the model), it is possible to calculate the dependence of the formation factor with porosity with good accuracy. When the cementation exponent ceases to remain constant with porosity; the new model is capable of capturing both: the non-linear behavior (for small porosity values) and the typical linear one in log-log plots for the formation factor vs. porosity. Comparisons with experimental data from four different conventional core rock lithologies: sands, sandstone, limestone and volcanic are shown, for all of them a good agreement is observed. This new model is robust, simple and of easy implementation for practical applications. In some cases, it could substitute Archie's law replacing its empirical nature.

  17. Comment on Self-Consistent Model of Black Hole Formation and Evaporation

    CERN Document Server

    Ho, Pei-Ming

    2015-01-01

    In an earlier work, Kawai et al proposed a model of black-hole formation and evaporation, in which the geometry of a collapsing shell of null dust is studied, including consistently the back reaction of its Hawking radiation. In this note, we illuminate the implications of their work, focusing on the resolution of the information loss paradox and the problem of the firewall.

  18. Thunderstorm formation and intensity determined from a three-dimensional subsynoptic-scale trajectory model

    Science.gov (United States)

    Wilson, G. S.

    1979-01-01

    A diagnostic trajectory model was used to provide a better understanding of the interrelationships between synoptic and convective-scale systems. Results indicate that synoptic scale systems exert a strong controlling influence over the formation and intensity of small mesoscale convective circulations.

  19. A mathematical model for the formation of beaded fibers in electrospinning

    Directory of Open Access Journals (Sweden)

    Liu Zhi

    2015-01-01

    Full Text Available Beaded fibers are often observed in electrospinning. However, its formation mechanism is not well understood. A mathematical model for pulsation of the charged jets during spinning is proposed to reveal the phenomenon of beaded fibers, and the main factors for beaded fibers are elucidated.

  20. Comment on self-consistent model of black hole formation and evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Pei-Ming [Department of Physics and Center for Theoretical Sciences, Center for Advanced Study in Theoretical Sciences,National Taiwan University, Taipei 106, Taiwan, R.O.C. (China)

    2015-08-18

    In an earlier work, Kawai et al. proposed a model of black-hole formation and evaporation, in which the geometry of a collapsing shell of null dust is studied, including consistently the back reaction of its Hawking radiation. In this note, we illuminate the implications of their work, focusing on the resolution of the information loss paradox and the problem of the firewall.

  1. C-elegans model identifies genetic modifiers of alpha-synuclein inclusion formation during aging

    NARCIS (Netherlands)

    van Ham, Tjakko J.; Thijssen, Karen L.; Breitling, Rainer; Hofstra, Robert M. W.; Plasterk, Ronald H. A.; Nollen, Ellen A. A.

    2008-01-01

    Inclusions in the brain containing alpha-synuclein are the pathological hallmark of Parkinson's disease, but how these inclusions are formed and how this links to disease is poorly understood. We have developed a C. elegans model that makes it possible to monitor, in living animals, the formation of

  2. Model studies of volatile diesel exhaust particle formation: organic vapours involved in nucleation and growth?

    Science.gov (United States)

    Pirjola, L.; Karl, M.; Rönkkö, T.; Arnold, F.

    2015-02-01

    High concentration of volatile nucleation mode particles (NUP) formed in the atmosphere during exhaust cools and dilutes have hazardous health effects and impair visibility in urban areas. Nucleation mechanisms in diesel exhaust are only poorly understood. We performed model studies using two sectional aerosol dynamics process models AEROFOR and MAFOR on the formation of particles in the exhaust of a diesel engine, equipped with an oxidative after-treatment system and running with low fuel sulphur content (FSC), under laboratory sampling conditions where the dilution system mimics real-world conditions. Different nucleation mechanisms were tested; based on the measured gaseous sulphuric acid (GSA) and non-volatile core and soot particle number concentrations of the raw exhaust, the model simulations showed that the best agreement between model predictions and measurements in terms of particle number size distribution was obtained by barrierless heteromolecular homogeneous nucleation between GSA and semi-volatile organic vapour (for example adipic acid) combined with the homogeneous nucleation of GSA alone. Major growth of the particles was predicted to occur by the same organic vapour at concentrations of (1-2) ×1012cm-3. The pre-existing core and soot mode concentrations had opposite trend on the NUP formation, and maximum NUP formation was predicted if a diesel particle filter (DPF) was used. On the other hand, NUP formation was ceased if the GSA concentration was less than 1010cm-3 which suggests, based on the measurements, the usage of biofuel to prevent volatile particles in diesel exhaust.

  3. On the internal model principle in formation control and in output synchronization of nonlinear systems

    NARCIS (Netherlands)

    Persis, Claudio De; Jayawardhana, Bayu

    2012-01-01

    The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution o

  4. Droplet formation in microfluidic T-junction generators operating in the transitional regime. II. Modeling.

    Science.gov (United States)

    Glawdel, Tomasz; Elbuken, Caglar; Ren, Carolyn L

    2012-01-01

    This is the second part of a two-part study on the generation of droplets at a microfluidic T-junction operating in the transition regime. In the preceding paper [Phys. Rev. E 85, 016322 (2012)], we presented our experimental observations of droplet formation and decomposed the process into three sequential stages defined as the lag, filling, and necking stages. Here we develop a model that describes the performance of microfluidic T-junction generators working in the squeezing to transition regimes where confinement of the droplet dominates the formation process. The model incorporates a detailed geometric description of the drop shape during the formation process combined with a force balance and necking criteria to define the droplet size, production rate, and spacing. The model inherently captures the influence of the intersection geometry, including the channel width ratio and height-to-width ratio, capillary number, and flow ratio, on the performance of the generator. The model is validated by comparing it to speed videos of the formation process for several T-junction geometries across a range of capillary numbers and viscosity ratios.

  5. Phase-field modeling of microstructural pattern formation in alloys and geological veins

    OpenAIRE

    Ankit, Kumar

    2016-01-01

    With the advent of high performance computing, the application areas of the phase-field method, traditionally used to numerically model the phase transformation in metals and alloys, have now spanned into geoscience. A systematic investigation of the two distinct scientific problems in consideration suggest a strong influence of interfacial energy on the natural and induced pattern formation in diffusion-controlled regime.

  6. Computer-Mediated Impression Formation: A Test of the Sticky Cues Model Using Facebook

    Science.gov (United States)

    Van Der Heide, Brandon Lee

    2009-01-01

    This research offers a model of online impression formation that explains how different impression-bearing cues may carry more or less informational value. This research considers the possibility that impression-bearing cues have greater informational value when those cues are distinctive and are task-relevant. This research refers to such cues as…

  7. On the internal model principle in formation control and in output synchronization of nonlinear systems

    NARCIS (Netherlands)

    Persis, Claudio De; Jayawardhana, Bayu

    2012-01-01

    The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution o

  8. On the internal model principle in formation control and in output synchronization of nonlinear systems

    NARCIS (Netherlands)

    Persis, Claudio De; Jayawardhana, Bayu

    2012-01-01

    The role of internal model principle is investigated in this paper in the context of collective synchronization and formation control problems. In the collective synchronization problem for nonlinear systems, we propose distributed control laws for passive systems which synchronize to the solution

  9. Droplet formation in a T-shaped microchannel junction: A model system for membrane emulsification

    NARCIS (Netherlands)

    Graaf, van der S.; Steegmans, M.L.J.; Sman, van der R.G.M.; Schroën, C.G.P.H.; Boom, R.M.

    2005-01-01

    Droplet formation was studied in a glass microchip with a small channel containing to-be-dispersed phase perpendicular to a large channel with a cross-flowing continuous phase. This resembles the situation during cross-flow membrane emulsification. In this model system, droplets are formed at a

  10. Toward a Kinetic Model for Acrylamide Formation in a Glucose-Asparagine Reaction System

    NARCIS (Netherlands)

    Knol, J.J.; Loon, W.A.M.; Linssen, J.P.H.; Ruck, A.L.; Boekel, van M.A.J.S.

    2005-01-01

    A kinetic model for the formation of acrylamide in a glucose-asparagine reaction system is pro-posed. Equimolar solutions (0.2 M) of glucose and asparagine were heated at different tempera-tures (120-200 C) at pH 6.8. Besides the reactants, acrylamide, fructose, and melanoidins were quantified after

  11. Combined Rock-physical Modelling and Seismic Inversion Techniques for Characterisation of the Posidonia Shale Formation

    NARCIS (Netherlands)

    Justiniano, A.; Jaya, M.; Diephuis, G.

    2015-01-01

    The objective of this study is to characterise the Jurassic Posidonia Shale Formation at Block Q16 located in the West Netherlands Basin. The characterisation was carried out through combining rock-physics modelling and seismic inversion techniques. The results show that the Posidonia Shale Formatio

  12. Numerical modeling of gas-phase kinetics in formation of secondary aerosol

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Three basic modules of gas-phase photochemical reactions involved in the formation of secondary aerosol are developed for modeling the concentration variation of precursors of aerosol, including ketone (RCOx), aldehyde (ALD), peroxyacetylnitrate (PAN), NO2, and SO2, followed by numerical solution for each of the modules. Reasonable trends of concentration variation of the precursors can be obtained from the proposed modules.

  13. Model Building to Facilitate Understanding of Holliday Junction and Heteroduplex Formation, and Holliday Junction Resolution

    Science.gov (United States)

    Selvarajah, Geeta; Selvarajah, Susila

    2016-01-01

    Students frequently expressed difficulty in understanding the molecular mechanisms involved in chromosomal recombination. Therefore, we explored alternative methods for presenting the two concepts of the double-strand break model: Holliday junction and heteroduplex formation, and Holliday junction resolution. In addition to a lecture and…

  14. A Connectionist Model of Stimulus Class Formation with a Yes/No Procedure and Compound Stimuli

    Science.gov (United States)

    Tovar, Angel E.; Chavez, Alvaro Torres

    2012-01-01

    We analyzed stimulus class formation in a human study and in a connectionist model (CM) with a yes/no procedure, using compound stimuli. In the human study, the participants were six female undergraduate students; the CM was a feed-forward back-propagation network. Two 3-member stimulus classes were trained with a similar procedure in both the…

  15. A Formative Evaluation of the Children, Youth, and Families at Risk Coaching Model

    Science.gov (United States)

    Olson, Jonathan R.; Smith, Burgess; Hawkey, Kyle R.; Perkins, Daniel F.; Borden, Lynne M.

    2016-01-01

    In this article, we describe the results of a formative evaluation of a coaching model designed to support recipients of funding through the Children, Youth, and Families at Risk (CYFAR) initiative. Results indicate that CYFAR coaches draw from a variety of types of coaching and that CYFAR principle investigators (PIs) are generally satisfied with…

  16. A standardised and reproducible model of intra-abdominal infection and abscess formation in rats

    NARCIS (Netherlands)

    Bosscha, K; Nieuwenhuijs, VB; Gooszen, AW; van Duijvenbode-Beumer, H; Visser, MR; Verweij, Willem; Akkermans, LMA

    2000-01-01

    Objective: To develop a standardised and reproducible model of intra-abdominal infection and abscess formation in rats. Design: Experimental study. Setting: University hospital, The Netherlands. Subjects: 36 adult male Wistar rats. Interventions: In 32 rats, peritonitis was produced using two differ

  17. Formation and fate of haloacetic acids (HAAs) within the water treatment plant.

    Science.gov (United States)

    Rodriguez, Manuel J; Serodes, Jean; Roy, Danielle

    2007-10-01

    Most research on the occurrence of chlorinated disinfection by-products (DBPs) in drinking water has focused on trihalomethane (THM) formation and evolution, in particular within distribution systems. In this research, we investigated the variability of the occurrence of haloacetic acids (HAAs) during the treatment process in two facilities where surface water is pre-chlorinated before being treated by conventional physico-chemical processes. The investigation focused on both seasonal and point-to-point fluctuations of HAAs. In both facilities, samples were collected weekly during 1 complete year at four points in order to generate robust data on HAAs and on complementary parameters. The results showed that the initial formation of HAAs was the highest and the most variable in the plant where levels of DBP precursor indicators and the pre-chlorination dose were both higher and more variable. Subsequent formation of HAAs from the pre-chlorination point until the settled water occurred due to remaining levels of residual chlorine and DBP precursors. However, HAA levels and in particular dichloroacetic acid (DCAA) (the preponderant HAA species in the waters under study) decreased dramatically during filtration, very probably because of biodegradation within the filter. The effect of filtration on DCAA fate was season-dependant, with the highest degradation in warm water periods and practically no variation during winter. Statistical modeling was applied to empirically identify the operational factors responsible for HAA formation and fate. Model performance to identify HAA variability in waters following pre-chlorination was much better than for water following filtration, which is due to the lack of information on mechanisms and conditions favoring DCAA degradation.

  18. Pattern Formation in a Predator-Prey Model with Both Cross Diffusion and Time Delay

    Directory of Open Access Journals (Sweden)

    Boli Xie

    2014-01-01

    Full Text Available A predator-prey model with both cross diffusion and time delay is considered. We give the conditions for emerging Turing instability in detail. Furthermore, we illustrate the spatial patterns via numerical simulations, which show that the model dynamics exhibits a delay and diffusion controlled formation growth not only of spots and stripe-like patterns, but also of the two coexist. The obtained results show that this system has rich dynamics; these patterns show that it is useful for the diffusive predation model with a delay effect to reveal the spatial dynamics in the real model.

  19. Methodology for construction of Vulcan model of the Saltby Volcanic Formation, DGSM Nottingham-Melton project

    OpenAIRE

    2005-01-01

    The object of constructing the Vulcan model was to create a quantitative 3-D visualisation of the concealed Saltby Volcanic Formation (SVF) (Carboniferous) within the area covered by the Nottingham and Melton Mobray 1:50 000 scale geological sheets (Nos. 126 and 142) which forms part of the current (2003) DGSM Nottingham-Melton Project. The model was not intended to be a structural geological representation; rather, a lithostratigraphic visualisation 'normalised' to an arbitrar...

  20. Modelling the Formation of Liver Zones within the Scope of Fractional Order Derivative

    Directory of Open Access Journals (Sweden)

    Abdon Atangana

    2014-01-01

    Full Text Available We develop and extend earlier results related to mathematical modelling of the liver formation zone by the adoption of noninteger order derivative. The hidden uncertainties in the model are captured and controlled thanks to the Caputo derivative. The stationary states are investigated and the time-dependent solution is approximated using two recent iteration methods. In particular, we discuss the convergence of these methods by constructing a suitable Hilbert space.

  1. Modelling the Formation of Liver Zones within the Scope of Fractional Order Derivative

    Science.gov (United States)

    Atangana, Abdon; Oukouomi Noutchie, Suares Clovis

    2014-01-01

    We develop and extend earlier results related to mathematical modelling of the liver formation zone by the adoption of noninteger order derivative. The hidden uncertainties in the model are captured and controlled thanks to the Caputo derivative. The stationary states are investigated and the time-dependent solution is approximated using two recent iteration methods. In particular, we discuss the convergence of these methods by constructing a suitable Hilbert space. PMID:25276791

  2. Rosuvastatin reduces neointima formation in a rat model of balloon injury

    Directory of Open Access Journals (Sweden)

    Preusch MR

    2010-11-01

    Full Text Available Abstract Background Processes of restenosis, following arterial injury, are complex involving different cell types producing various cytokines and enzymes. Among those enzymes, smooth muscle cell-derived matrix metalloproteinases (MMPs are thought to take part in cell migration, degrading of extracellular matrix, and neointima formation. MMP-9, also known as gelatinase B, is expressed immediately after vascular injury and its expression and activity can be inhibited by statins. Using an established in vivo model of vascular injury, we investigated the effect of the HMG-CoA reductase inhibitor rosuvastatin on MMP-9 expression and neointima formation. Materials and methods 14-week old male Sprague Dawley rats underwent balloon injury of the common carotid artery. Half of the animals received rosuvastatin (20 mg/kg body weight/day via oral gavage, beginning 3 days prior to injury. Gelatinase activity and neointima formation were analyzed 3 days and 14 days after balloon injury, respectively. 14 days after vascular injury, proliferative activity was assessed by staining for Ki67. Results After 14 days, animals in the rosuvastatin group showed a decrease in total neointima formation (0.194 ± 0.01 mm2 versus 0.124 ± 0.02 mm2, p Conclusions Rosuvastatin attenuates neointima formation without affecting early MMP-9 activity in a rat model of vascular injury.

  3. Modeling gas formation and mineral precipitation in a granular iron column.

    Science.gov (United States)

    Jeen, Sung-Wook; Amos, Richard T; Blowes, David W

    2012-06-19

    In granular iron permeable reactive barriers (PRBs), hydrogen gas formation, entrapment and release of gas bubbles, and secondary mineral precipitation have been known to affect the permeability and reactivity. The multicomponent reactive transport model MIN3P was enhanced to couple gas formation and release, secondary mineral precipitation, and the effects of these processes on hydraulic properties and iron reactivity. The enhanced model was applied to a granular iron column, which was studied for the treatment of trichloroethene (TCE) in the presence of dissolved CaCO(3). The simulation reasonably reproduced trends in gas formation, secondary mineral precipitation, permeability changes, and reactivity changes observed over time. The simulation showed that the accumulation of secondary minerals reduced the reactivity of the granular iron over time, which in turn decreased the rate of mineral accumulation, and also resulted in a gradual decrease in gas formation over time. This study provides a quantitative assessment of the evolving nature of geochemistry and permeability, resulting from coupled processes of gas formation and mineral precipitation, which leads to a better understanding of the processes controlling the granular iron reactivity, and represents an improved method for incorporating these factors into the design of granular iron PRBs.

  4. Elemental Abundances in Milky Way-like Galaxies from a Hierarchical Galaxy Formation Model

    CERN Document Server

    De Lucia, Gabriella; Frenk, Carlos S; Helmi, Amina; Navarro, Julio F; White, Simon D M

    2014-01-01

    We develop a new method to account for the finite lifetimes of stars and trace individual abundances within a semi-analytic model of galaxy formation. At variance with previous methods, based on the storage of the (binned) past star formation history of model galaxies, our method projects the information about the metals produced by each simple stellar population (SSP) in the future. Using this approach, an accurate accounting of the timings and properties of the individual SSPs composing model galaxies is possible. We analyse the dependence of our chemical model on various ingredients, and apply it to six simulated haloes of roughly Milky Way mass and with no massive close neighbour at z=0. For all models considered, the [Fe/H] distributions of the stars in the disc component are in good agreement with Milky Way data, while for the spheroid component (whose formation we model only through mergers) these are offset low with respect to observational measurements for the Milky Way bulge. This is a consequence o...

  5. Parametric studies of contrail ice particle formation in jet regime using one-dimensional microphysical modeling

    Directory of Open Access Journals (Sweden)

    H.-W. Wong

    2009-10-01

    Full Text Available Condensation trails (contrails formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age <5 s, systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a one-dimensional modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index >1×1015 (kg-fuel−1 at cruise. The effects of ion-mediated nucleation, ambient relative humidity, fuel sulfur content, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles, and the effect of fuel sulfur content is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles, providing a possible approach for contrail mitigation.

  6. Pesticide nonextractable residue formation in soil: insights from inverse modeling of degradation time series.

    Science.gov (United States)

    Loos, Martin; Krauss, Martin; Fenner, Kathrin

    2012-09-18

    Formation of soil nonextractable residues (NER) is central to the fate and persistence of pesticides. To investigate pools and extent of NER formation, an established inverse modeling approach for pesticide soil degradation time series was evaluated with a Monte Carlo Markov Chain (MCMC) sampling procedure. It was found that only half of 73 pesticide degradation time series from a homogeneous soil source allowed for well-behaved identification of kinetic parameters with a four-pool model containing a parent compound, a metabolite, a volatile, and a NER pool. A subsequent simulation indeed confirmed distinct parameter combinations of low identifiability. Taking the resulting uncertainties into account, several conclusions regarding NER formation and its impact on persistence assessment could nonetheless be drawn. First, rate constants for transformation of parent compounds to metabolites were correlated to those for transformation of parent compounds to NER, leading to degradation half-lives (DegT50) typically not being larger than disappearance half-lives (DT50) by more than a factor of 2. Second, estimated rate constants were used to evaluate NER formation over time. This showed that NER formation, particularly through the metabolite pool, may be grossly underestimated when using standard incubation periods. It further showed that amounts and uncertainties in (i) total NER, (ii) NER formed from the parent pool, and (iii) NER formed from the metabolite pool vary considerably among data sets at t→∞, with no clear dominance between (ii) and (iii). However, compounds containing aromatic amine moieties were found to form significantly more total NER when extrapolating to t→∞ than the other compounds studied. Overall, our study stresses the general need for assessing uncertainties, identifiability issues, and resulting biases when using inverse modeling of degradation time series for evaluating persistence and NER formation.

  7. nIFTy cosmology: the clustering consistency of galaxy formation models

    Science.gov (United States)

    Pujol, Arnau; Skibba, Ramin A.; Gaztañaga, Enrique; Benson, Andrew; Blaizot, Jeremy; Bower, Richard; Carretero, Jorge; Castander, Francisco J.; Cattaneo, Andrea; Cora, Sofia A.; Croton, Darren J.; Cui, Weiguang; Cunnama, Daniel; De Lucia, Gabriella; Devriendt, Julien E.; Elahi, Pascal J.; Font, Andreea; Fontanot, Fabio; Garcia-Bellido, Juan; Gargiulo, Ignacio D.; Gonzalez-Perez, Violeta; Helly, John; Henriques, Bruno M. B.; Hirschmann, Michaela; Knebe, Alexander; Lee, Jaehyun; Mamon, Gary A.; Monaco, Pierluigi; Onions, Julian; Padilla, Nelson D.; Pearce, Frazer R.; Power, Chris; Somerville, Rachel S.; Srisawat, Chaichalit; Thomas, Peter A.; Tollet, Edouard; Vega-Martínez, Cristian A.; Yi, Sukyoung K.

    2017-07-01

    We present a clustering comparison of 12 galaxy formation models [including semi-analytic models (SAMs) and halo occupation distribution (HOD) models] all run on halo catalogues and merger trees extracted from a single Λ cold dark matter N-body simulation. We compare the results of the measurements of the mean halo occupation numbers, the radial distribution of galaxies in haloes and the two-point correlation functions (2PCF). We also study the implications of the different treatments of orphan (galaxies not assigned to any dark matter subhalo) and non-orphan galaxies in these measurements. Our main result is that the galaxy formation models generally agree in their clustering predictions but they disagree significantly between HOD and SAMs for the orphan satellites. Although there is a very good agreement between the models on the 2PCF of central galaxies, the scatter between the models when orphan satellites are included can be larger than a factor of 2 for scales smaller than 1 h-1 Mpc. We also show that galaxy formation models that do not include orphan satellite galaxies have a significantly lower 2PCF on small scales, consistent with previous studies. Finally, we show that the 2PCF of orphan satellites is remarkably different between SAMs and HOD models. Orphan satellites in SAMs present a higher clustering than in HOD models because they tend to occupy more massive haloes. We conclude that orphan satellites have an important role on galaxy clustering and they are the main cause of the differences in the clustering between HOD models and SAMs.

  8. A model of relative translation and rotation in leader-follower spacecraft formations

    Directory of Open Access Journals (Sweden)

    Raymond Kristiansen

    2007-01-01

    Full Text Available In this paper, a model of a leader-follower spacecraft formation in six degrees of freedom is derived and presented. The nonlinear model describes the relative translational and rotationalmotion of the spacecraft, and extends previous work by providing a more complete factorization, together with detailed information about the matrices in the model. The resulting model shows many similarities with models for systems such as robot manipulators and marine vehicles. In addition, mathematical models of orbital perturbations due to gravitational variations, atmospheric drag, solar radiation and third-body effects are presented for completeness. Results from simulations are presented to visualize the properties of the model and to show the impact of the different orbital perturbations on the flight path.

  9. Modeling secondary organic aerosol formation through cloud processing of organic compounds

    Directory of Open Access Journals (Sweden)

    J. Chen

    2007-10-01

    Full Text Available Interest in the potential formation of secondary organic aerosol (SOA through reactions of organic compounds in condensed aqueous phases is growing. In this study, the potential formation of SOA from irreversible aqueous-phase reactions of organic species in clouds was investigated. A new proposed aqueous-phase chemistry mechanism (AqChem is coupled with the existing gas-phase Caltech Atmospheric Chemistry Mechanism (CACM and the Model to Predict the Multiphase Partitioning of Organics (MPMPO that simulate SOA formation. AqChem treats irreversible organic reactions that lead mainly to the formation of carboxylic acids, which are usually less volatile than the corresponding aldehydic compounds. Zero-dimensional model simulations were performed for tropospheric conditions with clouds present for three consecutive hours per day. Zero-dimensional model simulations show that 48-h average SOA formation is increased by 27% for a rural scenario with strong monoterpene emissions and 7% for an urban scenario with strong emissions of aromatic compounds, respectively, when irreversible organic reactions in clouds are considered. AqChem was also incorporated into the Community Multiscale Air Quality Model (CMAQ version 4.4 with CACM/MPMPO and applied to a previously studied photochemical episode (3–4 August 2004 focusing on the eastern United States. The CMAQ study indicates that the maximum contribution of SOA formation from irreversible reactions of organics in clouds is 0.28 μg m−3 for 24-h average concentrations and 0.60 μg m−3 for one-hour average concentrations at certain locations. On average, domain-wide surface SOA predictions for the episode are increased by 9% when irreversible, in-cloud processing of organics is considered. Because aldehydes of carbon number greater than four are assumed to convert fully to the corresponding carboxylic acids upon reaction with OH in cloud droplets and this assumption may overestimate

  10. [A mathematical model of hemodynamic processes for distal pulse wave formation].

    Science.gov (United States)

    Fedotov, A A

    2015-01-01

    A mathematical model of the formation of distal arterial pulse wave signal in the blood vessels of the upper limbs was considered. The formation of distal arterial pulse wave is represented as a composition of forward and reverse pulse waves propagating along the human arterial system. The system of formal analogy between pulse waves propagation along the human arterial system and the propagation of electrical oscillations in electrical transmission lines with distributed parameters was proposed. Dependencies of pulse wave propagation along the human arterial system were obtained by solving the one-dimensional Navier-Stokes equations for a few special cases.

  11. A reduced thermodynamic model on the formation of the Nansha warm water

    Institute of Scientific and Technical Information of China (English)

    CAI Shuqun; GAN Zijun; LI Chiwai; LONG Xiaomin; DONG Danpeng

    2004-01-01

    A reduced vertically integrated upper mixed layer model is set up to numerically study the thermodynamic process of the formation of the "Nansha warm water"(NWW) in the Nansha Islands sea areas in spring. According to the numerical experiments, it is shown that, in spring, the formation of the NWW is mainly due to the sea surface net heat flux and the local weak current strength; the contribution from temperature advection transport and warm water exchange with the outer seas (Sulu Sea or south of Sunda shelf) is very little. In the sea areas where the current is strong, the advection may also play an important role in the temperature field.

  12. Giant planet formation in the framework of the core instability model

    CERN Document Server

    Fortier, Andrea

    2010-01-01

    In this Thesis I studied the formation of the four giant planets of the Solar System in the framework of the nucleated instability hypothesis. The model considers that solids and gas accretion are coupled in an interactive fashion, taking into account detailed constitutive physics for the envelope. The accretion rate of the core corresponds to the oligarchic growth regime. I also considered that accreted planetesimals follow a size distribution. One of the main results of this Thesis is that I was able to compute the formation of Jupiter, Saturn, Uranus and Neptune in less than 10 million years, which is considered to be the protoplanetary disk mean lifetime.

  13. Modeling and experimental validation of TCE abatement and ozone formation with non thermal plasma

    OpenAIRE

    Vandenbroucke, Arne; Aerts, Robby; Morent, Rino; De Geyter, Nathalie; Bogaerts, Annemie; Leys, Christophe

    2012-01-01

    In this study, the formation of ozone and the abatement of trichloroethylene (TCE) with non thermal plasma was experimentally and theoretically investigated. The model predicts that the ozone formation increases with the energy deposition and decreases with the relative humidity (RH) of the air, which is qualitatively in agreement with experimental data. For an energy deposition of 0.136 J/cm³, the abatement of 1000 ppm TCE in air with 5 % RH is dominated by atomic oxygen and to a lesser exte...

  14. Modeling and experimental validation of TCE abatement and ozone formation with non thermal plasma

    OpenAIRE

    Vandenbroucke, Arne; Aerts, Robby; Morent, Rino; De Geyter, Nathalie; Bogaerts, Annemie; Leys, Christophe

    2012-01-01

    In this study, the formation of ozone and the abatement of trichloroethylene (TCE) with non thermal plasma was experimentally and theoretically investigated. The model predicts that the ozone formation increases with the energy deposition and decreases with the relative humidity (RH) of the air, which is qualitatively in agreement with experimental data. For an energy deposition of 0.136 J/cm³, the abatement of 1000 ppm TCE in air with 5 % RH is dominated by atomic oxygen and to a lesser exte...

  15. The Many Manifestations of Downsizing: Hierarchical Galaxy Formation Models confront Observations

    CERN Document Server

    Fontanot, Fabio; Monaco, Pierluigi; Somerville, Rachel S; Santini, Paola

    2009-01-01

    [abridged] It has been widely claimed that several lines of observational evidence point towards a "downsizing" (DS) of the process of galaxy formation over cosmic time. This behavior is sometimes termed "anti-hierarchical", and contrasted with the "bottom-up" assembly of the dark matter structures in Cold Dark Matter models. In this paper we address three different kinds of observational evidence that have been described as DS: the stellar mass assembly, star formation rate and the ages of the stellar populations in local galaxies. We compare a broad compilation of available data-sets with the predictions of three different semi-analytic models of galaxy formation within the Lambda-CDM framework. In the data, we see only weak evidence at best of DS in stellar mass and in star formation rate. We find that, when observational errors on stellar mass and SFR are taken into account, the models acceptably reproduce the evolution of massive galaxies, over the entire redshift range that we consider. However, lower m...

  16. Modeling SOA formation from the oxidation of intermediate volatility n-alkanes

    Directory of Open Access Journals (Sweden)

    J. Lee-Taylor

    2012-06-01

    Full Text Available The chemical mechanism leading to SOA formation and ageing is expected to be a multigenerational process, i.e. a successive formation of organic compounds with higher oxidation degree and lower vapor pressure. This process is here investigated with the explicit oxidation model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere. Gas phase oxidation schemes are generated for the C8–C24 series of n-alkanes. Simulations are conducted to explore the time evolution of organic compounds and the behavior of secondary organic aerosol (SOA formation for various preexisting organic aerosol concentration (COA. As expected, simulation results show that (i SOA yield increases with the carbon chain length of the parent hydrocarbon, (ii SOA yield decreases with decreasing COA, (iii SOA production rates increase with increasing COA and (iv the number of oxidation steps (i.e. generations needed to describe SOA formation and evolution grows when COA decreases. The simulated oxidative trajectories are examined in a two dimensional space defined by the mean carbon oxidation state and the volatility. Most SOA contributors are not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA, suggesting that OOA may underestimate SOA. Results show that the model is unable to produce highly oxygenated aerosols (OOA with large yields. The limitations of the model are discussed.

  17. Modeling SOA formation from the oxidation of intermediate volatility n-alkanes

    Directory of Open Access Journals (Sweden)

    J. Lee-Taylor

    2012-08-01

    Full Text Available The chemical mechanism leading to SOA formation and ageing is expected to be a multigenerational process, i.e. a successive formation of organic compounds with higher oxidation degree and lower vapor pressure. This process is here investigated with the explicit oxidation model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere. Gas phase oxidation schemes are generated for the C8–C24 series of n-alkanes. Simulations are conducted to explore the time evolution of organic compounds and the behavior of secondary organic aerosol (SOA formation for various preexisting organic aerosol concentration (COA. As expected, simulation results show that (i SOA yield increases with the carbon chain length of the parent hydrocarbon, (ii SOA yield decreases with decreasing COA, (iii SOA production rates increase with increasing COA and (iv the number of oxidation steps (i.e. generations needed to describe SOA formation and evolution grows when COA decreases. The simulated oxidative trajectories are examined in a two dimensional space defined by the mean carbon oxidation state and the volatility. Most SOA contributors are not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA, suggesting that OOA may underestimate SOA. Results show that the model is unable to produce highly oxygenated aerosols (OOA with large yields. The limitations of the model are discussed.

  18. An agent-based model for queue formation of powered two-wheelers in heterogeneous traffic

    Science.gov (United States)

    Lee, Tzu-Chang; Wong, K. I.

    2016-11-01

    This paper presents an agent-based model (ABM) for simulating the queue formation of powered two-wheelers (PTWs) in heterogeneous traffic at a signalized intersection. The main novelty is that the proposed interaction rule describing the position choice behavior of PTWs when queuing in heterogeneous traffic can capture the stochastic nature of the decision making process. The interaction rule is formulated as a multinomial logit model, which is calibrated by using a microscopic traffic trajectory dataset obtained from video footage. The ABM is validated against the survey data for the vehicular trajectory patterns, queuing patterns, queue lengths, and discharge rates. The results demonstrate that the proposed model is capable of replicating the observed queue formation process for heterogeneous traffic.

  19. An improved model for nucleation-limited ice formation in living cells during freezing.

    Directory of Open Access Journals (Sweden)

    Jingru Yi

    Full Text Available Ice formation in living cells is a lethal event during freezing and its characterization is important to the development of optimal protocols for not only cryopreservation but also cryotherapy applications. Although the model for probability of ice formation (PIF in cells developed by Toner et al. has been widely used to predict nucleation-limited intracellular ice formation (IIF, our data of freezing Hela cells suggest that this model could give misleading prediction of PIF when the maximum PIF in cells during freezing is less than 1 (PIF ranges from 0 to 1. We introduce a new model to overcome this problem by incorporating a critical cell volume to modify the Toner's original model. We further reveal that this critical cell volume is dependent on the mechanisms of ice nucleation in cells during freezing, i.e., surface-catalyzed nucleation (SCN and volume-catalyzed nucleation (VCN. Taken together, the improved PIF model may be valuable for better understanding of the mechanisms of ice nucleation in cells during freezing and more accurate prediction of PIF for cryopreservation and cryotherapy applications.

  20. Modeling and interpreting speckle pattern formation in swept-source optical coherence tomography (Conference Presentation)

    Science.gov (United States)

    Demidov, Valentin; Vitkin, I. Alex; Doronin, Alexander; Meglinski, Igor

    2017-03-01

    We report on the development of a unified Monte-Carlo based computational model for exploring speckle pattern formation in swept-source optical coherence tomography (OCT). OCT is a well-established optical imaging modality capable of acquiring cross-sectional images of turbid media, including biological tissues, utilizing back scattered low coherence light. The obtained OCT images include characteristic features known as speckles. Currently, there is a growing interest to the OCT speckle patterns due to their potential application for quantitative analysis of medium's optical properties. Here we consider the mechanisms of OCT speckle patterns formation for swept-source OCT approaches and introduce further developments of a Monte-Carlo based model for simulation of OCT signals and images. The model takes into account polarization and coherent properties of light, mutual interference of back-scattering waves, and their interference with the reference waves. We present a corresponding detailed description of the algorithm for modeling these light-medium interactions. The developed model is employed for generation of swept-source OCT images, analysis of OCT speckle formation and interpretation of the experimental results. The obtained simulation results are compared with selected analytical solutions and experimental studies utilizing various sizes / concentrations of scattering microspheres.