Surface monitoring for pitting evolution into uniform corrosion on Cu-Ni-Zn ternary alloy in alkaline chloride solution: ex-situ LCM and in-situ SECM

NASA Astrophysics Data System (ADS)

Kong, Decheng; Dong, Chaofang; Zheng, Zhaoran; Mao, Feixiong; Xu, Aoni; Ni, Xiaoqing; Man, Cheng; Yao, Jizheng; Xiao, Kui; Li, Xiaogang

2018-05-01

The evolution of the corrosion process on Cu-Ni-Zn alloy in alkaline chloride solution was investigated by in-situ scanning electrochemical microscopy, X-ray photoelectron spectroscopy, and ex-situ laser confocal microscopy, and the effects of ambient temperature and polarization time were also discussed. The results demonstrated a higher pitting nucleation rate and lower pit growth rate at low temperature. The ratio of pit depth to mouth diameter decreased with increasing pit volume and temperature, indicating that pits preferentially propagate in the horizontal direction rather than the vertical direction owing to the presence of corrosion products and deposited copper. The surface current was uniform and stabilized at approximately 2.2 nA during the passive stage, whereas the current increased after the pits were formed with the maximum approaching 3 nA. Increasing the temperature led to an increase in porous corrosion products (CuO, Zn(OH)2, and Ni(OH)2) and significantly increased the rate of transition from pitting to uniform corrosion. Dezincification corrosion was detected by energy dispersive spectrometry, and a mechanism for pitting transition into uniform corrosion induced by dezincification at the grain boundaries is proposed.

Mechanism of strength degradation for hot corrosion of alpha-SiC

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Jacobson, N. S.

1984-01-01

Sintered alpha SiC was corroded by thin films of Na2SO4 and Na2CO3 molten salts at 1000%. This hot corrosion attack reduced room temperature strengths by as much as 50%. Strength degradation was porportional to the degree and uniformity of corrosion pitting attack as controlled by the chemistry of the molten salt. Extensive fractography identified corrosion pits as the most prevalent source of failure. A fracture mechanics treatment of the strength/pit depth relationship produced an average K sub IC equal to 2.6 MPa sub m 1/2, which is consistent with published values.

Mechanism of strength degradation for hot corrosion of alpha-SiC

NASA Technical Reports Server (NTRS)

Smialek, James L.; Jacobson, Nathan S.

1986-01-01

Sintered alpha SiC was corroded by thin films of Na2SO4 and Na2CO3 molten salts at 1000 percent. This hot corrosion attack reduced room temperature strengths by as much as 50 percent. Strength degradation was proportional to the degree and uniformity of corrosion pitting attack as controlled by the chemistry of the molten salt. Extensive fractography identified corrosion pits as the most prevalent source of failure. A fracture mechanics treatment of the strength/pit depth relationship produced an average K sub IC equal to 2.6 MPa sub m 1/2, which is cnsistent ith published values.

A Comprehensive Investigation of Copper Pitting Corrosion in a Drinking Water Distribution System

EPA Science Inventory

Copper pipe pitting is a complicated corrosion process for which exact causes and solutions are uncertain. This paper presents the findings of a comprehensive investigation of a cold water copper pitting corrosion problem in a drinking water distribution system, including a refi...

Neutralisation of an acidic pit lake by alkaline waste products.

PubMed

Allard, Bert; Bäckström, Mattias; Karlsson, Stefan; Grawunder, Anja

2014-01-01

A former open pit where black shale (alum shale) was excavated during 1942-1965 has been water filled since 1966. The water chemistry was dominated by calcium and sulphate and had a pH of 3.2-3.4 until 1997-1998, when pH was gradually increasing. This was due to the intrusion of leachates from alkaline cement waste deposited close to the lake. A stable pH of around 7.5 was obtained after 6-7 years. The chemistry of the pit lake has changed due to the neutralisation. Concentrations of some dissolved metals, notably zinc and nickel, have gone down, as a result of adsorption/co-precipitation on solid phases (most likely iron and aluminium hydroxides), while other metals, notably uranium and molybdenum, are present at elevated levels. Uranium concentration is reaching a minimum of around pH 6.5 and is increasing at higher pH, which may indicate a formation of neutral and anionic uranyl carbonate species at high pH (and total carbonate levels around 1 mM). Weathering of the water-exposed shale is still in progress.

DOUBLE SHELL TANK (DST) INTEGRITY PROJECT HIGH LEVEL WASTE CHEMISTRY OPTIMIZATION

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

WASHENFELDER DJ

2008-01-22

The U.S. Department of Energy's Office (DOE) of River Protection (ORP) has a continuing program for chemical optimization to better characterize corrosion behavior of High-Level Waste (HLW). The DOE controls the chemistry in its HLW to minimize the propensity of localized corrosion, such as pitting, and stress corrosion cracking (SCC) in nitrate-containing solutions. By improving the control of localized corrosion and SCC, the ORP can increase the life of the Double-Shell Tank (DST) carbon steel structural components and reduce overall mission costs. The carbon steel tanks at the Hanford Site are critical to the mission of safely managing stored HLWmore » until it can be treated for disposal. The DOE has historically used additions of sodium hydroxide to retard corrosion processes in HLW tanks. This also increases the amount of waste to be treated. The reactions with carbon dioxide from the air and solid chemical species in the tank continually deplete the hydroxide ion concentration, which then requires continued additions. The DOE can reduce overall costs for caustic addition and treatment of waste, and more effectively utilize waste storage capacity by minimizing these chemical additions. Hydroxide addition is a means to control localized and stress corrosion cracking in carbon steel by providing a passive environment. The exact mechanism that causes nitrate to drive the corrosion process is not yet clear. The SCC is less of a concern in the newer stress relieved double shell tanks due to reduced residual stress. The optimization of waste chemistry will further reduce the propensity for SCC. The corrosion testing performed to optimize waste chemistry included cyclic potentiodynamic volarization studies. slow strain rate tests. and stress intensity factor/crack growth rate determinations. Laboratory experimental evidence suggests that nitrite is a highly effective:inhibitor for pitting and SCC in alkaline nitrate environments. Revision of the corrosion control strategies to a nitrite-based control, where there is no constant depletion mechanism as with hydroxide, should greatly enhance tank lifetime, tank space availability, and reduce downstream reprocessing costs by reducing chemical addition to the tanks.« less

Pitting corrosion of titanium. The relationship between pitting potential and competitive anion adsorption at the oxide film/electrolyte interface

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

Basame, S.B.; White, H.S.

2000-04-01

The potential-dependent breakdown of the native oxide film ({approximately}20 {angstrom} thick) on titanium has been investigated in aqueous Br{sup {minus}} solutions and in solutions that contain a mixture of Br{sup {minus}} and anions that inhibit oxide breakdown (i.e., Cl{sup {minus}}, I{sup {minus}}, SO{sub 4}{sup 2{minus}}, Fe(CN){sub 6}{sup 4{minus}}, and Fe(CN){sub 6}{sup 3{minus}}). The oxide film is unstable in neutral pH solutions containing only Br{sup {minus}}, resulting in the formation of stable corrosion pits at relatively low potentials ({approximately}1.4 V vs. Ag/AgCl). The pitting potential, E{sub p}, is strongly dependent upon the concentration of Br{sup {minus}}, and can be modeled usingmore » a Langmuir isotherm to describe the adsorption of Br{sup {minus}} at the oxide film/electrolyte interface. Addition of a second anion inhibits oxide film breakdown, as indicated by a large positive shift in E{sub p} and a decrease in the number of stable corrosion pits. The dependence of E{sub p} on the relative concentrations of Br{sup {minus}} and the inhibitor anion is consistent with competitive adsorption of the anions. Equilibrium adsorption coefficients for I{sup {minus}}, Br{sup {minus}}, and Cl{sup {minus}} are estimated from the dependence of E{sub p} on anion concentration. The results are used to establish a physical basis for the anomalously low pitting potential for titanium in aqueous Br{sup {minus}} solutions.« less

Impact of Annealing Prior to Solution Treatment on Aging Precipitates and Intergranular Corrosion Behavior of Al-Cu-Li Alloy 2050

NASA Astrophysics Data System (ADS)

Ye, Zhi-hao; Cai, Wen-xin; Li, Jin-feng; Chen, Xiang-rong; Zhang, Rui-feng; Birbilis, Nick; Chen, Yong-lai; Zhang, Xu-hu; Ma, Peng-cheng; Zheng, Zi-qiao

2018-06-01

The influences of annealing prior to solution treatment on the grain structure, subsequent aging precipitates, and intergranular corrosion (IGC) of Al-Cu-Li alloy (AA2050) sheet with T6 aging at 448 K (175 °C) were investigated. Annealing impedes the full recrystallization during solution treatment, increasing the population density of T1 (Al2CuLi) precipitates, but decreasing that of θ' (Al2Cu) precipitates, of the aged alloy. Meanwhile, annealing leads to the heterogeneous distribution of T1 precipitates, increasing the alloy hardness, and decreasing the open-circuit potential of the aged alloy. With prolonged aging time, the corrosion mode of the aged AA2050 samples with and without annealing evolved in a similar manner. The corrosion mode as a function of aging may be summarized as local IGC with pitting and general IGC with pitting (following initial aging and under the underaged condition), pitting corrosion (later in the under-aging stage), pitting with slight IGC (near the peak-aged condition), and pitting with local IGC (under the overaging condition). The annealing treatment hinders IGC propagation on the rolling surface while accelerating the IGC on transverse surfaces.

Impact of Annealing Prior to Solution Treatment on Aging Precipitates and Intergranular Corrosion Behavior of Al-Cu-Li Alloy 2050

NASA Astrophysics Data System (ADS)

Ye, Zhi-hao; Cai, Wen-xin; Li, Jin-feng; Chen, Xiang-rong; Zhang, Rui-feng; Birbilis, Nick; Chen, Yong-lai; Zhang, Xu-hu; Ma, Peng-cheng; Zheng, Zi-qiao

2018-04-01

The influences of annealing prior to solution treatment on the grain structure, subsequent aging precipitates, and intergranular corrosion (IGC) of Al-Cu-Li alloy (AA2050) sheet with T6 aging at 448 K (175 °C) were investigated. Annealing impedes the full recrystallization during solution treatment, increasing the population density of T1 (Al2CuLi) precipitates, but decreasing that of θ' (Al2Cu) precipitates, of the aged alloy. Meanwhile, annealing leads to the heterogeneous distribution of T1 precipitates, increasing the alloy hardness, and decreasing the open-circuit potential of the aged alloy. With prolonged aging time, the corrosion mode of the aged AA2050 samples with and without annealing evolved in a similar manner. The corrosion mode as a function of aging may be summarized as local IGC with pitting and general IGC with pitting (following initial aging and under the underaged condition), pitting corrosion (later in the under-aging stage), pitting with slight IGC (near the peak-aged condition), and pitting with local IGC (under the overaging condition). The annealing treatment hinders IGC propagation on the rolling surface while accelerating the IGC on transverse surfaces.

Mine dewatering and impact assessment in an arid area: Case of Gulf region.

PubMed

Yihdego, Yohannes; Drury, Len

2016-11-01

Analytical and empirical solution coupled with water balance method were used to predict the ground water inflow to a mine pit excavated below the water table, final pit lake level/recovery and radius of influence, through long-term and time variant simulations. The solution considers the effect of decreased saturated thickness near the pit walls, distributed recharge to the water table and upward flow through the pit bottom. The approach is flexible to accommodate the anisotropy/heterogeneity of the real world. Final pit void water level was assessed through scenarios to know whether it will be consumed by evaporation and a shallow lake will form or not. The optimised radius of influence was estimated which is considered as crucial information in relation to the engineering aspects of mine planning and sustainable development of the mine area. Time-transient inflow over a period of time was estimated using solutions, including analytical element method (AEM). Their primary value is in providing estimates of pit inflow rates to be used in the mine dewatering. Inflow estimation and recovery helps whether there is water to supplement the demand and if there is any recovery issue to be dealt with in relation to surface and groundwater quality/eco-system, environmental evaluations and mitigation. Therefore, this method is good at informing decision makers in assessing the effects of mining operations and developing an appropriate water management strategy.

Light scattering from laser induced pit ensembles on high power laser optics

DOE PAGES

Feigenbaum, Eyal; Elhadj, Selim; Matthews, Manyalibo J.

2015-01-01

Far-field light scattering characteristics from randomly arranged shallow Gaussian-like shaped laser induced pits, found on optics exposed to high energy laser pulses, is studied. Closed-form expressions for the far-field intensity distribution and scattered power are derived for individual pits and validated using numerical calculations of both Fourier optics and FDTD solutions to Maxwell’s equations. It is found that the scattered power is proportional to the square of the pit width and approximately also to the square of the pit depth, with the proportionality factor scaling with pit depth. As a result, the power scattered from shallow pitted optics is expectedmore » to be substantially lower than assuming complete scattering from the total visible footprint of the pits.« less

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel.

PubMed

Yang, Zixuan; Kan, Bo; Li, Jinxu; Qiao, Lijie; Volinsky, Alex A; Su, Yanjing

2017-11-14

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance.

A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel

PubMed Central

Yang, Zixuan; Kan, Bo; Li, Jinxu; Su, Yanjing; Qiao, Lijie; Volinsky, Alex A.

2017-01-01

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance. PMID:29135912

On the Mathematical Modeling of Single and Multiple Scattering of Ultrasonic Guided Waves by Small Scatterers: A Structural Health Monitoring Measurement Model

NASA Astrophysics Data System (ADS)

Strom, Brandon William

In an effort to assist in the paradigm shift from schedule based maintenance to conditioned based maintenance, we derive measurement models to be used within structural health monitoring algorithms. Our models are physics based, and use scattered Lamb waves to detect and quantify pitting corrosion. After covering the basics of Lamb waves and the reciprocity theorem, we develop a technique for the scattered wave solution. The first application is two-dimensional, and is employed in two different ways. The first approach integrates a traction distribution and replaces it by an equivalent force. The second approach is higher order and uses the actual traction distribution. We find that the equivalent force version of the solution technique holds well for small pits at low frequencies. The second application is three-dimensional. The equivalent force caused by the scattered wave of an arbitrary equivalent force is calculated. We obtain functions for the scattered wave displacements as a function of equivalent forces, equivalent forces as a function of incident wave, and scattered wave amplitudes as a function of incident amplitude. The third application uses self-consistency to derive governing equations for the scattered waves due to multiple corrosion pits. We decouple the implicit set of equations and solve explicitly by using a recursive series solution. Alternatively, we solve via an undetermined coefficient method which results in an interaction operator and solution via matrix inversion. The general solution is given for N pits including mode conversion. We show that the two approaches are equivalent, and give a solution for three pits. Various approximations are advanced to simplify the problem while retaining the leading order physics. As a final application, we use the multiple scattering model to investigate resonance of Lamb waves. We begin with a one-dimensional problem and progress to a three-dimensional problem. A directed graph enables interpretation of the interaction operator, and we show that a series solution converges due to loss of energy in the system. We see that there are four causes of resonance and plot the modulation depth as a function of spacing between the pits.

Pitting corrosion resistance of a novel duplex alloy steel in alkali-activated slag extract in the presence of chloride ions

NASA Astrophysics Data System (ADS)

Shi, Jin-jie; Ming, Jing; Liu, Xin

2017-10-01

In this study, two types of reinforcing steels (conventional low-carbon steel and a novel duplex alloy steel with Cr and Mo) were exposed to chloride-contaminated extract solutions (ordinary Portland cement (OPC) extract and alkali-activated slag (AAS) extract) to investigate their pitting corrosion resistance. The results confirm that the pitting corrosion resistance of the alloy steel is much higher than that of the low-carbon steel in both extract solutions with various NaCl concentrations. Moreover, for each type of steel, the AAS extract contributes to a higher pitting corrosion resistance compared with the OPC extract in the presence of chloride ions, likely because of the formation of flocculent precipitates on the steel surface.

Stochastic theory of fatigue corrosion

NASA Astrophysics Data System (ADS)

Hu, Haiyun

1999-10-01

A stochastic theory of corrosion has been constructed. The stochastic equations are described giving the transportation corrosion rate and fluctuation corrosion coefficient. In addition the pit diameter distribution function, the average pit diameter and the most probable pit diameter including other related empirical formula have been derived. In order to clarify the effect of stress range on the initiation and growth behaviour of pitting corrosion, round smooth specimen were tested under cyclic loading in 3.5% NaCl solution.

Infrared nanospectroscopy reveals the chemical nature of pit membranes in water-conducting cells of the plant xylem.

PubMed

Pereira, Luciano; Flores-Borges, Denisele; Bittencourt, Paulo; Mayer, Juliana; Kiyota, Eduardo; Araújo, Pedro; Jansen, Steven; Freitas, Raul; Oliveira, Rafael; Mazzafera, Paulo

2018-06-05

In the xylem of angiosperm plants, microscopic pits through the secondary cell walls connect the water-conducting vessels. Cellulosic meshes originated from primary walls and middle lamella between adjacent vessels, called pit membrane, separates one conduit from another. The intricate structure of the nano-sized pores in pit membranes enables the passage of water under negative pressure without hydraulic failure due to obstruction by gas bubbles (i.e., embolism) under normal conditions or mild drought stress. Since the chemical composition of pit membranes affects embolism formation and bubble behavior, we directly measured pit membrane composition in Populus nigra wood. Here, we characterized the chemical composition of cell wall structures by synchrotron infrared nanospectroscopy and atomic force microscopy-infrared nanospectroscopy with high spatial resolution. Characteristic peaks of cellulose, phenolic compounds, and proteins were found in the intervessel pit membrane of P. nigra wood. In addition, vessel to parenchyma pit membranes and developing cell walls of the vascular cambium showed clear signals of cellulose, proteins, and pectin. We did not find a distinct peak of lignin and other compounds in these structures. Our investigation of the complex chemical composition of intervessel pit membranes furthers our understanding of the flow of water and bubbles between neighboring conduits. The advances presented here pave the way for further label-free studies related to the nano-chemistry of plant cell components. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.

Chemical, Physical, and Biological Factors Shape Littoral Invertebrate Community Structure in Coal-Mining End-Pit Lakes

NASA Astrophysics Data System (ADS)

Luek, Andreas; Rasmussen, Joseph B.

2017-04-01

Aquatic invertebrates form the base of the consumer food web in lakes. In coal-mining end-pit lakes, invertebrates are exposed to an environment with potentially challenging physical and chemical features. We hypothesized that the physical and chemical features of end-pit lakes reduce critical littoral habitat and thus reduce invertebrate diversity, thereby limiting the potential for these lakes to be naturalized. We used a multivariate approach using principle component analysis and redundancy analysis to study relationships between invertebrate community structure, habitat features, and water quality in five end-pit lakes and five natural lakes in the Rocky Mountain foothills of west-central Alberta, Canada. Results show a significantly different invertebrate community structure was present in end-pit lakes as compared with reference lakes in the same region, which could be accounted for by water hardness, conductivity, slope of the littoral zone, and phosphorus concentrations. Habitat diversity in end-pit lakes was also limited, cover provided by macrophytes was scarce, and basin slopes were significantly steeper in pit lakes. Although water chemistry is currently the strongest influencing factor on the invertebrate community, physical challenges of habitat homogeneity and steep slopes in the littoral zones were identified as major drivers of invertebrate community structure. The addition of floating wetlands to the littoral zone of existing pit lakes can add habitat complexity without the need for large-scale alterations to basing morphology, while impermeable capping of waste-rock and the inclusion of littoral habitat in the planning process of new pit lakes can improve the success of integrating new pit lakes into the landscape.

Chemical, Physical, and Biological Factors Shape Littoral Invertebrate Community Structure in Coal-Mining End-Pit Lakes.

PubMed

Luek, Andreas; Rasmussen, Joseph B

2017-04-01

Aquatic invertebrates form the base of the consumer food web in lakes. In coal-mining end-pit lakes, invertebrates are exposed to an environment with potentially challenging physical and chemical features. We hypothesized that the physical and chemical features of end-pit lakes reduce critical littoral habitat and thus reduce invertebrate diversity, thereby limiting the potential for these lakes to be naturalized. We used a multivariate approach using principle component analysis and redundancy analysis to study relationships between invertebrate community structure, habitat features, and water quality in five end-pit lakes and five natural lakes in the Rocky Mountain foothills of west-central Alberta, Canada. Results show a significantly different invertebrate community structure was present in end-pit lakes as compared with reference lakes in the same region, which could be accounted for by water hardness, conductivity, slope of the littoral zone, and phosphorus concentrations. Habitat diversity in end-pit lakes was also limited, cover provided by macrophytes was scarce, and basin slopes were significantly steeper in pit lakes. Although water chemistry is currently the strongest influencing factor on the invertebrate community, physical challenges of habitat homogeneity and steep slopes in the littoral zones were identified as major drivers of invertebrate community structure. The addition of floating wetlands to the littoral zone of existing pit lakes can add habitat complexity without the need for large-scale alterations to basing morphology, while impermeable capping of waste-rock and the inclusion of littoral habitat in the planning process of new pit lakes can improve the success of integrating new pit lakes into the landscape.

Screening Health Risk Assessment Burn Pit Exposures, Balad Air Base, Iraq and Addendum Report

DTIC Science & Technology

2008-05-01

risk uses principles drawn from many scientific disciplines including chemistry , toxicology, physics, mathematics, and statistics. Because the data...uses principles drawn from many scientific disciplines, including chemistry , toxicology, physics, mathematics, and statistics. Because the data...natural chemicals in plants (called flavonoids ) also act on the Ah-receptor and could potentially block the effects of dioxins. One more reason to

Electrochemical studies on zirconium and its biocompatible alloys Ti-50Zr at.% and Zr-2.5Nb wt.% in simulated physiologic media.

PubMed

Oliveira, Nilson T C; Biaggio, Sonia R; Rocha-Filho, Romeu C; Bocchi, Nerilso

2005-09-01

Different electrochemical studies were carried out for Zr and its biocompatible alloys Ti-50Zr at.% and Zr-2.5Nb wt.% in solutions simulating physiologic media, Ringer and PBS (phosphate buffered saline) solutions. The results from rest-potential measurements showed that the three materials are spontaneously passivated in both solutions and that the Ti-50Zr alloy has the greatest tendency for spontaneous oxide formation. Some corrosion parameters (such as the pitting and repassivation potentials) were obtained via cyclic voltammetry in both solutions, revealing that the Ti-50Zr has the best corrosion protection while Zr has the worst. On the other hand, the pre-anodization (up to 8 V vs. SCE) of the alloys in a 0.15 mol/L Na2SO4 solution led to a significant improvement in their protection against pitting corrosion when exposed to the Ringer solution. Elemental analyses by EDX showed that during pitting corrosion, there is no preferential corrosion of any of the alloying elements (Zr, Ti, Nb). Copyright (c) 2005 Wiley Periodicals, Inc.

Corrosion of carbon steels, stainless steels, and titanium in aqueous lithium bromide solution

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

Guinon, J.L.; Garcia-Anton, J.; Perez-Herranz, V.

1994-03-01

Effects of lithium bromide (LiBr) concentration, pH, temperature, exposure time, and the action of some inhibitors on corrosion of several carbon (C) steels, stainless steels (SS), and a titanium (Ti) alloy were studied. Corrosion rates were determined by the polarization resistance method and compared to rates determined by weight-loss measurements. Pitting potentials (E[sub p]) were evaluated in neutral LiBr solution and with different inhibitors. Pit density and average pit depth depended on the metal tested, with lowest values for Ti, the next lowest values for type 316 SS (UNS S31600), and the highest values for UNS G41350 tempered steel.

The effects of pitting on fatigue crack nucleation in 7075-T6 aluminum alloy

NASA Technical Reports Server (NTRS)

Ma, LI; Hoeppner, David W.

1994-01-01

A high-strength aluminum alloy, 7075-T6, was studied to quantitatively evaluate chemical pitting effects of its corrosion fatigue life. The study focused on pit nucleation, pit growth, and fatigue crack nucleation. Pitting corrosion fatigue experiments were conducted in 3.5 percent NaCl aqueous solution under constant amplitude sinusoidal loading at two frequencies, 5 and 20 Hz. Smooth and unnotched specimens were used in this investigation. A video recording system was developed to allow in situ observation of the surface changes of the specimens during testing. The results indicated that pitting corrosion considerably reduces the fatigue strength by accelerating fatigue crack nucleation. A metallographic examination was conducted on the specimens to evaluate the nature of corrosion pits. First, the actual shapes of the corrosion pits were evaluated by cross-sectioning the pits. Secondly, the relation between corrosion pits and microstructure was also investigated. Finally, the possibility of another corrosion mechanism that might be involved in pitting was explored in this investigation. The fractography of the tested specimens showed that corner corrosion pits were responsible for fatigue crack nucleation in the material due to the associated stress concentration. The pits exhibited variance of morphology. Fatigue life for the experimental conditions appeared to be strongly dependent on pitting kinetics and the crack nucleation stage.

The chemical identity of intervessel pit membranes in Acer challenges hydrogel control of xylem hydraulic conductivity

PubMed Central

Klepsch, Matthias M.; Schmitt, Marco; Paul Knox, J.; Jansen, Steven

2016-01-01

Ion-mediated enhancement of the hydraulic conductivity of xylem tissue (i.e. the ionic effect) has been reported for various angiosperm species. One explanation of the ionic effect is that it is caused by the swelling and shrinking of intervessel pit membranes due to the presence of pectins and/or other cell-wall matrix polymers such as heteroxylans or arabinogalactan–proteins (AGPs) that may contain acidic sugars. Here, we examined the ionic effect for six Acer species and their pit membrane chemistry using immunocytochemistry, including antibodies against glycoproteins. Moreover, anatomical features related to the bordered pit morphology and vessel dimensions were investigated using light and electron microscopy. The ionic effect varied from 18 % (± 9) to 32 % (± 13). Epitopes of homogalacturonan (LM18) and xylan (LM11) were not detected in intervessel pit membranes. Negative results were also obtained for glycoproteins (extensin: LM1, JIM20; AGP glycan: LM2), although AGP (JIM13)-related epitopes were detected in parenchyma cells. The mean vessel length was significantly correlated with the magnitude of the ionic effect, unlike other pit or vessel-related characteristics. Our results suggest that intervessel pit membranes of Acer are unlikely to contain pectic or other acidic polysaccharides. Therefore, alternative explanations should be tested to clarify the ionic effect. PMID:27354661

Influence of the Haizhou Open Pit Coal Mine on the atmospheric flow over Fuxin, China.

PubMed

Chen, He; Yang, Zhi-Feng; Wang, Xuan

2004-01-01

The influence of the Haizhou Open Pit Mine on the atmospheric flow in nearby Fuxin City in China was analyzed with the aid of the steady-state Navier-Stokes equations. The finite element method was used to obtain numerical solutions to these equations. The results showed that the Haizhou Open Pit Coal Mine contributes to the turbulent flow in the Fuxin City and its surroundings. However, when compared with the climatic effects, the open pit mine has a relatively small impact on the atmospheric flow over Fuxin.

Passivation and electrochemical behavior of 316L stainless steel in chlorinated simulated concrete pore solution

NASA Astrophysics Data System (ADS)

Luo, Hong; Su, Huaizhi; Dong, Chaofang; Li, Xiaogang

2017-04-01

In this paper, the passivation and electrochemical behavior of 316L stainless steel in chlorinated simulated concrete pore solutions at different pH was evaluated by potentiodynamic measurements, electrochemical impedance spectroscopy. The composition of the passive film and surface morphology were investigated by X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and scanning electron microscopy, respectively. The results reveal that metastable pitting susceptibility, stable pitting corrosion, and composition of the passive film are influenced by pH value. After long time immersion, a bilayer structure passive film can be formed in this environment. The appearance of molybdates on the outermost surface layer, further enhancing the stability of the passive film. Moreover, the good pitting corrosion resistance of 316L stainless steel in simulated concrete pore solution without carbonated is mainly due to the presence of high Cr/Fe ratio and molybdates ions within the passive film.

Effect of Minor Alloying Elements on Localized Corrosion Behavior of Aluminum-Copper-Magnesium based Solid Solution Alloys

NASA Astrophysics Data System (ADS)

Aburada, Tomohiro

2011-12-01

The effects and mechanistic roles of a minor alloying element, Ni, on the localized corrosion behavior were explored by studying (Al75Cu 17Mg8)97Ni3 and Al70Cu 18Mg12 amorphous alloys. To explore the minor alloying element limited to the outer surface layers, the corrosion behavior of Al70Cu 18Mg12 amorphous alloy in solutions with and without Ni 2+ was also studied. Both Ni alloying and Ni2+ in solution improved the localized corrosion resistance of the alloys by ennobling the pitting and repassivation potentials. Pit growth by the selective dissolution of Al and Mg was also suppressed by Ni alloying. Remaining Cu and Ni reorganized into a Cu-rich polycrystalline nanoporous structure with continuous ligaments in pits. The minor Ni alloying and Ni2+ in solution suppressed the coarsening of the ligaments in the dealloyed nanoporous structure. The presence of relatively immobile Ni atoms at the surface suppressed the surface diffusion of Cu, which reduced the coarsening of the nanoporous structure, resulting in the formation of 10 to 30 nm wide Cu ligaments. Two mechanistic roles of minor alloying elements in the improvement of the pitting corrosion resistance of the solid solution alloys are elucidated. The first role is the suppression of active dissolution by altering the atomic structure. Ni in solid solution formed stronger bonds with Al, and reduces the probability of weaker Al-Al bonds. The second role is to hinder dissolution by producing a greater negative shift of the true interfacial potential at the dissolution front under the dealloyed layer due to the greater Ohmic resistance through the finer porous structure. These effects contributed to the elevation of pitting potentials by ennobling the applied potential required to produce enough dissolution for the stabilization of pits. Scientifically, this thesis advances the state of understanding of alloy dissolution, particularly the role of minor alloying elements on preferential oxidation at the atomic, nanometer, and micrometer scales. Technological implementations of the findings of the research are also discussed, including a new route to synthesize nanoporous materials with tunable porosity and new corrosion mitigation strategies for commercial Al-based alloys containing the detrimental Al2CuMg phase.

The Effects of Alloy Chemistry on Localized Corrosion of Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Sapiro, David O.

This study investigated localized corrosion behavior of austenitic stainless steels under stressed and unstressed conditions, as well as corrosion of metallic thin films. While austenitic stainless steels are widely used in corrosive environments, they are vulnerable to pitting and stress corrosion cracking (SCC), particularly in chloride-containing environments. The corrosion resistance of austenitic stainless steels is closely tied to the alloying elements chromium, nickel, and molybdenum. Polarization curves were measured for five commercially available austenitic stainless steels of varying chromium, nickel, and molybdenum content in 3.5 wt.% and 25 wt.% NaCl solutions. The alloys were also tested in tension at slow strain rates in air and in a chloride environment under different polarization conditions to explore the relationship between the extent of pitting corrosion and SCC over a range of alloy content and environment. The influence of alloy composition on corrosion resistance was found to be consistent with the pitting resistance equivalent number (PREN) under some conditions, but there were also conditions under which the model did not hold for certain commercial alloy compositions. Monotonic loading was used to generate SCC in in 300 series stainless steels, and it was possible to control the failure mode through adjusting environmental and polarization conditions. Metallic thin film systems of thickness 10-200 nm are being investigated for use as corrosion sensors and protective coatings, however the corrosion properties of ferrous thin films have not been widely studied. The effects of film thickness and substrate conductivity were examined using potentiodynamic polarization and scanning vibrating electrode technique (SVET) on iron thin films. Thicker films undergo more corrosion than thinner films in the same environment, though the corrosion mechanism is the same. Conductive substrates encourage general corrosion, similar to that of bulk iron, while insulating substrates supported only localized corrosion.

10 CFR 1045.15 - Classification and declassification presumptions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... criteria in § 1045.16 indicates otherwise: (1) Basic science: mathematics, chemistry, theoretical and experimental physics, engineering, materials science, biology and medicine; (2) Magnetic confinement fusion...); (5) Fact of use of safety features (e.g., insensitive high explosives, fire resistant pits) to lower...

10 CFR 1045.15 - Classification and declassification presumptions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... criteria in § 1045.16 indicates otherwise: (1) Basic science: mathematics, chemistry, theoretical and experimental physics, engineering, materials science, biology and medicine; (2) Magnetic confinement fusion...); (5) Fact of use of safety features (e.g., insensitive high explosives, fire resistant pits) to lower...

In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g., corrosion) of a confined metal surface

PubMed Central

Merola, C.; Cheng, H.-W.; Schwenzfeier, K.; Kristiansen, K.; Chen, Y.-J.; Dobbs, H. A.; Valtiner, M.

2017-01-01

Reactivity in confinement is central to a wide range of applications and systems, yet it is notoriously difficult to probe reactions in confined spaces in real time. Using a modified electrochemical surface forces apparatus (EC-SFA) on confined metallic surfaces, we observe in situ nano- to microscale dissolution and pit formation (qualitatively similar to previous observation on nonmetallic surfaces, e.g., silica) in well-defined geometries in environments relevant to corrosion processes. We follow “crevice corrosion” processes in real time in different pH-neutral NaCl solutions and applied surface potentials of nickel (vs. Ag|AgCl electrode in solution) for the mica–nickel confined interface of total area ∼0.03 mm2. The initial corrosion proceeds as self-catalyzed pitting, visualized by the sudden appearance of circular pits with uniform diameters of 6–7 μm and depth ∼2–3 nm. At concentrations above 10 mM NaCl, pitting is initiated at the outer rim of the confined zone, while below 10 mM NaCl, pitting is initiated inside the confined zone. We compare statistical analysis of growth kinetics and shape evolution of individual nanoscale deep pits with estimates from macroscopic experiments to study initial pit growth and propagation. Our data and experimental techniques reveal a mechanism that suggests initial corrosion results in formation of an aggressive interfacial electrolyte that rapidly accelerates pitting, similar to crack initiation and propagation within the confined area. These results support a general mechanism for nanoscale material degradation and dissolution (e.g., crevice corrosion) of polycrystalline nonnoble metals, alloys, and inorganic materials within confined interfaces. PMID:28827338

Restoration of Secondary Containment in Double Shell Tank (DST) Pits

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

SHEN, E.J.

2000-10-05

Cracks found in many of the double-shell tank (DST) pump and valve pits bring into question the ability of the pits to provide secondary containment and remain in compliance with State and Federal regulations. This study was commissioned to identify viable options for maintain/restoring secondary containment capability in these pits. The basis for this study is the decision analysis process which identifies the requirements to be met and the desired goals (decision criteria) that each option will be weighed against. A facilitated workshop was convened with individuals knowledgeable of Tank Farms Operations, engineering practices, and safety/environmental requirements. The outcome ofmore » this workshop was the validation or identification of the critical requirements, definition of the current problem, identification and weighting of the desired goals, baselining of the current repair methods, and identification of potential alternate solutions. The workshop was followed up with further investigations into the potential solutions that were identified in the workshop and through other efforts. These solutions are identified in the body of this report. Each of the potential solutions were screened against the list of requirements and only those meeting the requirements were considered viable options. To expand the field of viable options, hybrid concepts that combine the strongest features of different individual approaches were also examined. Several were identified. The decision analysis process then ranked each of the viable options against the weighted decision criteria, which resulted in a recommended solution. The recommended approach is based upon installing a sprayed on coating system.« less

Effects of chloride ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel

NASA Astrophysics Data System (ADS)

Li, Hui-yan; Dong, Chao-fang; Xiao, Kui; Li, Xiao-gang; Zhong, Ping

2016-11-01

The effects of Cl- ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel (UHSMSS) were investigated by a series of electrochemical tests combined with observations by stereology microscopy and scanning electron microscopy. A critical Cl- ion concentration was found to exist (approximately 0.1wt%), above which pitting occurred. The pitting potential decreased with increasing Cl- ion concentration. A UHSMSS specimen tempered at 600°C exhibited a better pitting corrosion resistance than the one tempered at 400°C. The corrosion current density and passive current density of the UHSMSS tempered at 600°C decreased with increasing pH values of the corrosion solution. The pits developed a shallower dish geometry with increasing polarization potential. A lacy cover on the pits of the UHSMSS tempered at 400°C accelerated pitting, whereas corrosion products deposited in the pits of the UHSMSS tempered at 600°C hindered pitting.

Geochemistry and migration of contaminants at the Weldon Spring chemical plant site, St. Charles County, Missouri, 1989-91

USGS Publications Warehouse

Schumacher, John G.

1993-01-01

The geochemistry of the shallow aquifer and geochemical controls on the migration of uranium and other constituents from raffinate pits were determined at the Weldon Spring chemical plant site. Surface-water samples from the raffinate pits con- tained large concentrations of calcium, magnesium, sodium, potassium, sulfate, nitrite, lithium, moly- bdenum, strontium, vanadium, and uranium. Analyses of interstitial-water samples from raffinate pit 3 indicated that concentrations of most constituents increased with increasing depth below the water- sediment interface. Nitrate and uranium were not chemically reduced and attenuated within the raffinate pits and can be expected to migrate into the overburden. Laboratory sorption experiments were performed to evaluate the effect of pH value on the sorption of several raffinate constituents by the overburden. No sorption of calcium, sodium, sulfate, nitrate, or lithium was observed. Sorption of molybdenum was dependent on solution pH and sorption of uranium was dependent on solution pH and carbonate concentration. The sorption of uranium and molybdenum was consistent with sorption controlled by oxyhydroxides. The quality of water collected in overburden lysimeters near raffinate pit 4 can be modeled as a mixture of water from raffinate pits 3 and 4, and an uncontaminated com- ponent in a system at equilibrium with ferrihydrite and calcite. Increased constituent concentrations in a perennial spring north of the site were the result of a subsurface connection between the spring and several losing stream segments receiving runoff from the site, in addition to seepage from the raffinate pits.

Pit initiation on nitinol in simulated physiological solutions.

PubMed

Pound, Bruce G

2018-05-01

Inclusions appear to play a crucial role in the initiation of pitting on nitinol, but the reason remains unclear. Furthermore, it has not been established whether the type of inclusion is a central factor. In this study, potentiodynamic polarization together with scanning electron microscopy and energy dispersive X-ray spectroscopy were used to provide more insight into the initiation of pits on electropolished nitinol wire. Corrosion was limited to a single primary pit on each of the few wire samples that exhibited breakdown. The pit contained numerous Ti 2 NiO x inclusions, but secondary pits that developed within the primary pit provided evidence that these inclusions were the sites of pit initiation. Although several theories have been proposed to account for pit initiation at inclusions in mechanically polished and electropolished nitinol, titanium depletion in the adjacent alloy matrix appears to provide the most viable explanation. The key factor appears to be the size of the inclusion and therefore the extent of titanium depletion in the alloy matrix. The type of inclusion evidently plays a secondary role at most. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1605-1610, 2018. © 2017 Wiley Periodicals, Inc.

Evaluation of groundwater pollution in a mining area using analytical solution: a case study of the Yimin open-pit mine in China.

PubMed

Li, Tianxin; Li, Li; Song, Hongqing; Meng, Linglong; Zhang, Shuli; Huang, Gang

2016-01-01

This study focused on using analytical and numerical models to develop and manage groundwater resources, and predict the effects of management measurements in the groundwater system. Movement of contaminants can be studied based on groundwater flow characteristics. This study can be used for prediction of ion concentration and evaluation of groundwater pollution as the theoretical basis. The Yimin open-pit mine is located in the northern part of the Inner Mongolia Autonomous Region of China. High concentrations of iron and manganese are observed in Yimin open-pit mine because of exploitation and pumping that have increased the concentration of the ions in groundwater. In this study, iron was considered as an index of contamination, and the solute model was calibrated using concentration observations from 14 wells in 2014. The groundwater flow model and analytical solutions were used in this study to forecast pollution concentration and variation trend after calibration. With continuous pumping, contaminants will migrate, and become enriched, towards the wellhead in the flow direction. The concentration of the contaminants and the range of pollution increase with the flow rate increased. The suitable flow rate of single well should be <380 m/day at Yimin open-pit for the standard value of pollution concentration.

Use of Electrochemical Noise (EN) Technique to Study the Effect of sulfate and Chloride Ions on Passivation and Pitting Corrosion Behavior of 316 Stainless Steel

NASA Astrophysics Data System (ADS)

Pujar, M. G.; Anita, T.; Shaikh, H.; Dayal, R. K.; Khatak, H. S.

2007-08-01

In the present paper, studies were conducted on AISI Type 316 stainless steel (SS) in deaerated solutions of sodium sulfate as well as sodium chloride to establish the effect of sulfate and chloride ions on the electrochemical corrosion behavior of the material. The experiments were conducted in deaerated solutions of 0.5 M sodium sulfate as well as 0.5 M sodium chloride using electrochemical noise (EN) technique at open circuit potential (OCP) to collect the correlated current and potential signals. Visual records of the current and potential, analysis of data to arrive at the statistical parameters, spectral density estimation using the maximum entropy method (MEM) showed that sulfate ions were incorporated in the passive film to strengthen the same. However, the adsorption of chloride ions resulted in pitting corrosion thereby adversely affecting noise resistance ( R N). Distinct current and potential signals were observed for metastable pitting, stable pitting and passive film build-up. Distinct changes in the values of the statistical parameters like R N and the spectral noise resistance at zero frequency ( R°SN) revealed adsorption and incorporation of sulfate and chloride ions on the passive film/solution interface.

Shallow V-Shape Nanostructured Pit Arrays in Germanium Using Aqua Regia Electroless Chemical Etching

PubMed Central

Chaabane, Ibtihel; Banerjee, Debika; Touayar, Oualid; Cloutier, Sylvain G.

2017-01-01

Due to its high refractive index, reflectance is often a problem when using Germanium for optoelectronic devices integration. In this work, we propose an effective and low-cost nano-texturing method for considerably reducing the reflectance of bulk Germanium. To do so, uniform V-shape pit arrays are produced by wet electroless chemical etching in a 3:1 volume ratio of highly-concentrated hydrochloridric and nitric acids or so-called aqua regia bath using immersion times ranging from 5 to 60 min. The resulting pit morphology, the crystalline structure of the surface and the changes in surface chemistry after nano-patterning are all investigated. Finally, broadband near-infrared reflectance measurements confirm a significant reduction using this simple wet etching protocol, while maintaining a crystalline, dioxide-free, and hydrogen-passivated surface. It is important to mention that reflectance could be further reduced using deeper pits. However, most optoelectronic applications such as photodetectors and solar cells require relatively shallow patterning of the Germanium to allow formation of a pn-junction close to the surface. PMID:28773215

Prokaryotic communities in pit mud from different-aged cellars used for the production of Chinese strong-flavored liquor.

PubMed

Tao, Yong; Li, Jiabao; Rui, Junpeng; Xu, Zhancheng; Zhou, Yan; Hu, Xiaohong; Wang, Xiang; Liu, Menghua; Li, Daping; Li, Xiangzhen

2014-04-01

Chinese strong-flavored liquor (CSFL) accounts for more than 70% of all Chinese liquor production. Microbes in pit mud play key roles in the fermentation cellar for the CSFL production. However, microbial diversity, community structure, and cellar-age-related changes in pit mud are poorly understood. Here, we investigated the prokaryotic community structure and diversity in pit-mud samples with different cellar ages (1, 10, 25, and 50 years) using the pyrosequencing technique. Results indicated that prokaryotic diversity increased with cellar age until the age reached 25 years and that prokaryotic community structure changed significantly between three cellar ages (1, 10, and 25 years). Significant correlations between prokaryotic communities and environmental variables (pH, NH4(+), lactic acid, butyric acid, and caproic acid) were observed. Overall, our study results suggested that the long-term brewing operation shapes unique prokaryotic community structure and diversity as well as pit-mud chemistry. We have proposed a three-phase model to characterize the changes of pit-mud prokaryotic communities. (i) Phase I is an initial domestication period. Pit mud is characterized by abundant Lactobacillus and high lactic acid and low pH levels. (ii) Phase II is a transition period. While Lactobacillus abundance decreases dramatically, that of Bacteroidetes and methanogens increases. (iii) Phase III is a relative mature period. The prokaryotic community shows the highest diversity and capability to produce more caproic acid as a precursor for synthesis of ethyl caproate, the main flavor component in CSFL. This research provides scientific evidence to support the practical experience that old fermentation cellars produce high-quality liquor.

IMPACT OF WATER CHEMISTRY ON LOCALIZED CORROSION OF COPPER PITTING

EPA Science Inventory

This project will help identify what waters are problematic in causing the corrosion of copper pipes and improve understanding of how water distribution leads to corrosion. This project will also focus on the prevention of pinhole leaks and how to reverse them once they occur. ...

Effects of sulfate and nitrate anions on aluminum corrosion in slightly alkaline solution

NASA Astrophysics Data System (ADS)

Li, Shengyi; Church, Benjamin C.

2018-05-01

The corrosion mechanisms and kinetics of AA1085 in Li2SO4 and LiNO3 aqueous rechargeable lithium-ion battery electrolytes were investigated at pH 11 using chronoamperometry. The corrosion kinetics of AA1085 is controlled by the electrolyte concentration level and the anodic potentials. AA1085 is susceptible to crystallographic pitting corrosion in Li2SO4 electrolytes. The rates of pit nucleation and pit growth both decreased at higher Li2SO4 concentrations or at lower anodic potentials. AA1085 passivates against pitting corrosion in LiNO3 electrolytes due to the formation of a thick, uniform corrosion product layer. The growth rate of the passive film was slightly enhanced by increasing the electrolyte concentration and anodic potentials. X-ray photoelectron spectroscopy spectra showed the formation of a thin sulfate-incorporated passive film on the electrode, which comprises Al2(SO)418H2O, Al(OH)SO4 and Al(OH)3, before the occurrence of pitting growth in 2 M Li2SO4 electrolyte. The thick corrosion product layer formed in 5 M LiNO3 electrolyte was composed of Al(OH)3 and AlOOH. Raman spectroscopy on deionized water, LiOH solution, Li2SO4 and LiNO3 electrolytes depicted changes of solution structure with increasing electrolyte concentration. The influence of extrinsic and intrinsic factors on the corrosion kinetics of AA1085 in Li2SO4 and LiNO3 electrolytes at pH 11 are discussed in detail.

The efficiencies of cast blasting in wide pits

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

Martin, R.L.; King, M.G.

Blasting activities in all four pits at Thunder Basin Coal`s Black Thunder Mine are focused on cast blasting. With widths varying from 190 feet to 265 feet and bench heights varying from 90 feet to 175 feet, casting efficiencies vary with different geometry`s. For example, the percent cast to final in the 200 foot pit is on the average higher than the 270 foot pit. The powder factors are somewhat higher in the narrower pits, thus increasing the cost of blasting. This leads to a very detailed look at the actual benefit of cast blasting and the associated cost ofmore » these benefits. The simple solution would be to reduce the width of the pits, thereby increasing the percent cast to final. However, the lower rehandle and low coal loss associated with wide pits would be fortified. Upon further review it becomes obvious that the wider pits could not be compared to the narrow pits with the cast to final percent indices. The focus should be shifted to cubic yards cast to final per lineal foot of pit. This will allow for more accurate measures of the casting efficiency of the shot. When comparing the pits with these indices their performances were much closer than the percent cast to final indices. The powder factors being higher in the narrow pits drove up the cost per cubic yard cast to final. Therefore, even though the percent cast to final was higher, the cost per cubic yard was also higher.« less

Investigating pitting in X65 carbon steel using potentiostatic polarisation

NASA Astrophysics Data System (ADS)

Mohammed, Sikiru; Hua, Yong; Barker, R.; Neville, A.

2017-11-01

Although pitting corrosion in passive materials is generally well understood, the growth of surface pits in actively-corroding materials has received much less attention to date and remains poorly understood. One of the key challenges which exists is repeatedly and reliably generating surface pits in a practical time-frame in the absence of deformation and/or residual stress so that studies on pit propagation and healing can be performed. Another pertinent issue is how to evaluate pitting while addressing general corrosion in low carbon steel. In this work, potentiostatic polarisation was employed to induce corrosion pits (free from deformation or residual stress) on actively corroding X65 carbon steel. The influence of applied potential (50 mV, 100 mV and 150 mV vs open circuit potential) was investigated over 24 h in a CO2-saturated, 3.5 wt.% NaCl solution at 30 °C and pH 3.8. Scanning electron microscopy (SEM) was utilised to examine pits, while surface profilometry was conducted to measure pit depth as a function of applied potential over the range considered. Analyses of light pitting (up to 120 μm) revealed that pit depth increased linearly with increase in applied potential. This paper relates total pit volume (measured using white light interferometry) to dissipated charge or total mass loss (using the current response for potentiostatic polarisation in conjunction with Faraday's law). By controlling the potential of the surface (anodic) the extent of pitting and general corrosion could be controlled. This allowed pits to be evaluated for their ability to continue to propagate after the potentiostatic technique was employed. Linear growth from a depth of 70 μm at pH 3.8, 80 °C was demonstrated. The technique offers promise for the study of inhibition of pitting.

Adsorption mechanisms of removing heavy metals and dyes from aqueous solution using date pits solid adsorbent.

PubMed

Al-Ghouti, Mohammad A; Li, Juiki; Salamh, Yousef; Al-Laqtah, Nasir; Walker, Gavin; Ahmad, Mohammad N M

2010-04-15

A potential usefulness of raw date pits as an inexpensive solid adsorbent for methylene blue (MB), copper ion (Cu(2+)), and cadmium ion (Cd(2+)) has been demonstrated in this work. This work was conducted to provide fundamental information from the study of equilibrium adsorption isotherms and to investigate the adsorption mechanisms in the adsorption of MB, Cu(2+), and Cd(2+) onto raw date pits. The fit of two models, namely Langmuir and Freundlich models, to experimental data obtained from the adsorption isotherms was checked. The adsorption capacities of the raw date pits towards MB and both Cu(2+) and Cd(2+) ions obtained from Langmuir and Freundlich models were found to be 277.8, 35.9, and 39.5 mg g(-1), respectively. Surface functional groups on the raw date pits surface substantially influence the adsorption characteristics of MB, Cu(2+), and Cd(2+) onto the raw date pits. The Fourier transform infrared spectroscopy (FTIR) studies show clear differences in both absorbances and shapes of the bands and in their locations before and after solute adsorption. Two mechanisms were observed for MB adsorption, hydrogen bonding and electrostatic attraction, while other mechanisms were observed for Cu(2+) and Cd(2+). For Cu(2+), binding two cellulose/lignin units together is the predominant mechanism. For Cd(2+), the predominant mechanism is by binding itself using two hydroxyl groups in the cellulose/lignin unit. 2009 Elsevier B.V. All rights reserved.

Determination of precursor sites for pitting corrosion of polycrystalline titanium by using different techniques

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

Garfias-Mesias, L.F.; Alodan, M.; James, P.I.

1998-06-01

Scanning electrochemical microscopy (SECM) in ferrocyanide and bromide solutions was used to locate active sites (pitting precursors) on polycrystalline Ti where oxidation of Br{sup {minus}} and Fe(CN){sub 6}{sup 4{minus}} was possible. Analysis of the electrochemically active sites was done by using electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), and in situ confocal laser scanning microscopy (CLSM). In most cases, the active sites were found to be associated with particles (inclusions) which contained mainly Al and Si; however, some other areas not associated with particles were also found to be active. Although the size of themore » inclusions was normally smaller than 20 {micro}m, as revealed by SEM and AFM imaging, in some cases larger particles were also found. Pitting corrosion tests in bromide solution at potentials above 1.5 V{sub SCE} followed by EDX analysis inside the pits and in situ CLSM observation, confirmed that most of the localized attack started in the areas where particles had been located.« less

Electrochemical analysis of the corrosion inhibition effect of trypsin complex on the pitting corrosion of 420 martensitic stainless steel in 2M H2SO4 solution.

PubMed

Loto, Roland Tolulope

2018-01-01

Inhibition effect of trypsin complex (TC) on the pitting corrosion of martensitic stainless steel (type 420) in 1M H2SO4 solution was studied with potentiodynamic polarization, open circuit potential measurement and optical microscopy. TC reduced the corrosion rate of the steel with maximum inhibition efficiency of 80.75%. Corrosion potential shifted anodically due to the electrochemical action of TC. The pitting potential increased from 1.088VAg/AgCl (3M) at 0% TC to 1.365VAg/AgCl(3M) at 4% TC. TC shifts the open circuit corrosion potential from -0.270s at 0% TC concentration to -0.255V at 5% TC. The compound completely adsorbed onto the steel according to Langmuir, Frumkin and Temkin isotherms. ATF-FTIR spectroscopy confirmed the inhibition mode to be through surface coverage. Thermodynamic calculations showed physisorption molecular interaction. Corrosion pits are present on the uninhibited 420 morphology in comparison to TC inhibited surface which slightly deteriorated.

Electrochemical analysis of the corrosion inhibition effect of trypsin complex on the pitting corrosion of 420 martensitic stainless steel in 2M H2SO4 solution

PubMed Central

Loto, Roland Tolulope

2018-01-01

Inhibition effect of trypsin complex (TC) on the pitting corrosion of martensitic stainless steel (type 420) in 1M H2SO4 solution was studied with potentiodynamic polarization, open circuit potential measurement and optical microscopy. TC reduced the corrosion rate of the steel with maximum inhibition efficiency of 80.75%. Corrosion potential shifted anodically due to the electrochemical action of TC. The pitting potential increased from 1.088VAg/AgCl (3M) at 0% TC to 1.365VAg/AgCl(3M) at 4% TC. TC shifts the open circuit corrosion potential from -0.270s at 0% TC concentration to -0.255V at 5% TC. The compound completely adsorbed onto the steel according to Langmuir, Frumkin and Temkin isotherms. ATF-FTIR spectroscopy confirmed the inhibition mode to be through surface coverage. Thermodynamic calculations showed physisorption molecular interaction. Corrosion pits are present on the uninhibited 420 morphology in comparison to TC inhibited surface which slightly deteriorated. PMID:29672541

Influence of Step Annealing Temperature on the Microstructure and Pitting Corrosion Resistance of SDSS UNS S32760 Welds

NASA Astrophysics Data System (ADS)

Yousefieh, M.; Shamanian, M.; Saatchi, A.

2011-12-01

In the present work, the influence of step annealing heat treatment on the microstructure and pitting corrosion resistance of super duplex stainless steel UNS S32760 welds have been investigated. The pitting corrosion resistance in chloride solution was evaluated by potentiostatic measurements. The results showed that step annealing treatments in the temperature ranging from 550 to 1000 °C resulted in a precipitation of sigma phase and Cr2N along the ferrite/austenite and ferrite/ferrite boundaries. At this temperature range, the metastable pits mainly nucleated around the precipitates formed in the grain boundary and ferrite phase. Above 1050 °C, the microstructure contains only austenite and ferrite phases. At this condition, the critical pitting temperature of samples successfully arrived to the highest value obtained in this study.

The effect of tempering temperature on pitting corrosion resistance of 420 stainless steels

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

Anwar, Moch Syaiful, E-mail: moch026@lipi.go.id; Prifiharni, Siska, E-mail: sisk002@lipi.go.id; Mabruri, Efendi, E-mail: effe004@lipi.go.id

2016-04-19

The AISI Type 420 stainless steels are commonly used to steam generators, mixer blades, etc. These stainless steels are most prone to pitting in dissolved Cl{sup −} containing environments. In this paper, the effect of tempering temperature on pitting corrosion resistance of AISI Type 420 stainless steels was studied. The AISI Type 420 stainless steels specimens were heat treated at the temperature of 1050°C for 1 hour to reach austenite stabilization and then quench in the oil. After that, the specimens were tempered at the temperature of 150, 250, 350 and 450°C for 30 minutes and then air cooled tomore » the room temperature. The electrochemical potentiodynamic polarization test was conducted at 3.5% sodium chloride solution to evaluate corrosion rate and pitting corrosion behaviour. The Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) were used to evaluate the pitting corrosion product. The result have shown that highest pitting potential was found in the sample tempered at 250°C and corrosion pits were found to initiate preferentially around chromium carbides.« less

Numerical ages of Holocene tributary debris fans inferred from dissolution pitting on carbonate boulders in the Grand Canyon of Arizona

USGS Publications Warehouse

Hereford, R.; Thompson, K.S.; Burke, K.J.

1998-01-01

Carbonate boulders transported down steep tributary channels by debris flow came to rest on Holocene debris fans beside the Colorado River in Grand Canyon National Park. Weakly acidic rainfall and the metabolic activity of blue-green algae have produced roughly hemispheric dissolution pits as much as 2-cm deep on the initially smooth surfaces of the boulders. The average depth of dissolution pits increases with relative age of fan surfaces. The deepening rate averages 2.4 mm/1000 yr (standard error = 0.2 mm/1000 yr), as calculated from several radiometrically dated surfaces and an archeological structure. This linear rate, which appears constant over at least the past 3000 yr, is consistent with field relations limiting the maximum age of the fans and with the physical chemistry of limestone dissolution. Dissolution-pit measurements (n = 6973) were made on 617 boulders on 71 fan surfaces at the 26 largest debris fans in Grand Canyon. Among these fan surfaces, the average pit depth ranges from 1.2 to 17.4 mm, and the resulting pit dissolution ages range from 500 to 7300 cal yr B.P. Most (75%) surfaces are younger than 3000 yr, probably because of removal of older debris fans by the Colorado River. Many of the ages are close to 800, 1600, 2300, 3100, or 4300 cal yr B.P. If not the result of differential preservation of fan surfaces, this clustering implies periods of heightened debris-flow activity and increased precipitation.

Pitting corrosion of titanium. Interim report, June-December 1993

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

Casillas, N.; Charlebois, S.J.; Smyrl, W.H.

1994-01-20

The breakdown of native and anodically-grown oxide films on Ti electrodes is investigated by scanning electrochemical microscopy (SECM), video microscopy, transmission electron microscopy and voltammetry. SECM is used to demonstrate that the oxidation of Br- on Ti occurs at microscopic surface sites (10 - 50 micrometer diameter, 30 sites/sq cm) that are randomly positioned across the oxide surface. After determining the position of the active sites for Br- oxidation, breakdown of the oxide is initiated by increasing the electrode potential to more positive values. Direct correspondence is observed between the location of the electroactive sites and corrosion pits, indicating thatmore » oxide breakdown is associated with a localized site of high electrical conductivity. The potential at which pitting is observed in voltammetric experiments is found to be proportional to the average oxide thickness, for values ranging between 20 and 100 A, indicating that breakdown is determined either by the magnitude of the electric field within the oxide or by the interfacial potential at the oxide/Br- solution interface. Pitting occurs at significantly lower potentials in Br- solutions than in C 1- solutions, suggesting a strong chemical interaction between the TiO2 surface and Br-. A mechanism of oxide breakdown is proposed that is based on the potential-dependent chemical dissolution of the oxide at microscopic surface sites.« less

Prokaryotic Communities in Pit Mud from Different-Aged Cellars Used for the Production of Chinese Strong-Flavored Liquor

PubMed Central

Tao, Yong; Li, Jiabao; Rui, Junpeng; Xu, Zhancheng; Zhou, Yan; Hu, Xiaohong; Wang, Xiang; Liu, Menghua; Li, Daping

2014-01-01

Chinese strong-flavored liquor (CSFL) accounts for more than 70% of all Chinese liquor production. Microbes in pit mud play key roles in the fermentation cellar for the CSFL production. However, microbial diversity, community structure, and cellar-age-related changes in pit mud are poorly understood. Here, we investigated the prokaryotic community structure and diversity in pit-mud samples with different cellar ages (1, 10, 25, and 50 years) using the pyrosequencing technique. Results indicated that prokaryotic diversity increased with cellar age until the age reached 25 years and that prokaryotic community structure changed significantly between three cellar ages (1, 10, and 25 years). Significant correlations between prokaryotic communities and environmental variables (pH, NH4+, lactic acid, butyric acid, and caproic acid) were observed. Overall, our study results suggested that the long-term brewing operation shapes unique prokaryotic community structure and diversity as well as pit-mud chemistry. We have proposed a three-phase model to characterize the changes of pit-mud prokaryotic communities. (i) Phase I is an initial domestication period. Pit mud is characterized by abundant Lactobacillus and high lactic acid and low pH levels. (ii) Phase II is a transition period. While Lactobacillus abundance decreases dramatically, that of Bacteroidetes and methanogens increases. (iii) Phase III is a relative mature period. The prokaryotic community shows the highest diversity and capability to produce more caproic acid as a precursor for synthesis of ethyl caproate, the main flavor component in CSFL. This research provides scientific evidence to support the practical experience that old fermentation cellars produce high-quality liquor. PMID:24487528

Directed self-assembly of metal oxide quantum dots: Copper oxide on strontium titanium trioxide

NASA Astrophysics Data System (ADS)

Du, Yingge

2007-12-01

This dissertation explores the use of focused ion-beams (FIB) to direct the self-assembly of Cu2O quantum dots (QDs) on SrTiO3 (100) substrates via point implants of Ga+ at 30 keV After Ga+ implant and subsequent chemical and thermal surface preparation, oxygen plasma-assisted molecular beam-epitaxy (OPA-MBE) is used to grow Cu 2O QDs. The research of this dissertation finds that, for high FIB implant dose (5.6x1018 ions/cm2) and large interdot spacing (1000 nm), multiple QDs can be formed preferentially on the edges of FIB modified pits. For lower doses and/or smaller interdot spacings (8.8x1014 ions/cm2 and lower, 130 or 167 nm), individual QDs nucleate first within the pits. Under carefully controlled conditions, the separation and arrangement of the Cu2O QDs follows the FIB patterned template. This study finds that the FIB directed self-assembly technique works for different FIB doses, FIB interdot spacings and OPA-MBE deposition thicknesses, suggesting that this method is robust and flexible. Examination of QD growth on low-dose implant surfaces revealed a multi-step growth process. Initial deposition filled the pits just to the level of the original unmodified crystal growth surface. Following a pause in QD growth and the deposition of additional material, QD growth resumed on top of these perfectly filled pits. As growth continued, the dots reached a self-limiting size such that additional material deposition generated more QDs of similar size rather than continued growth of the large dots. This dissertation also seeks to increase understanding of the relative rolls played in the directed self-assembly process by local substrate chemistry, surface morphology, crystal-linity, and stress/strain. Experimental results revealed that although Ga concentration was noticeably higher on modified regions after FIB implant, no measurable Ga was found on the surface after high temperature annealing performed prior to QD growth. Thus Ga related chemistry/reactivity changes appear unlikely to be primary motivators of directed self-assembly. Low dose implant patterning created local depressions on the surface. This pit shape topography appears to be a strong contributor to the preferred nucleation within the pits, as the sidewalls of those surface pits could contain a high density of surface steps, which are known to decrease the adatom diffusion length and act as sinks to absorb the diffusing species. To further interpret the low dose implant results, calculations of total free-energy changes have been performed to study the differences between nucleation on a flat substrate surface and nucleation within a surface pit. This analysis shows that nucleation within a pit is almost always energetically favorable. In some special cases, assuming the pits have an inverted pyramidal shape, calculations show that island formation within the pits lowers the system total free-energy from the beginning of growth, i.e. there is no critical radius or energy barrier before a stable nucleus can be formed. The major geometric difference between high and low dose implantation area was revealed by AFM studies, which showed that pits generated by high implantation dose were still rounded after annealing and before growth, while pits from lower doses patterning had developed square edges oriented along the <100> directions of the substrate. These geometric differences suggest differences in crystalline or strain/stress states, either/both of which could have caused the subsequent different island growth characteristics. Continued study of directed self-assembly of metal oxide quantum dots should lead to better understanding of the creation of well ordered, precisely controlled, high density QD arrays, ultimately contributing to the development of next generation nanoelectronic, magnetic, and optical devices.

Pitting corrosion resistance of nickel-titanium rotary instruments with different surface treatments in seventeen percent ethylenediaminetetraacetic Acid and sodium chloride solutions.

PubMed

Bonaccorso, Antonio; Tripi, Teresa Roberta; Rondelli, Gianni; Condorelli, Guglielmo Guido; Cantatore, Giuseppe; Schäfer, Edgar

2008-02-01

This study evaluated the pitting corrosion resistance of nickel-titanium (NiTi) rotary instruments with different surface treatments in 17% ethylenediaminetetraacetic acid (EDTA) and NaCl solutions. Electropolished RaCe instruments were allocated to group A, non-electropolished RaCe instruments to group B, and physical vapor deposition (PVD)-coated Alpha files to group C (10 instruments per group). Electrochemical measurements were carried out by using a potentiostat for galvanic current measurements. On the basis of electrochemical tests, no localized corrosion problems are to be expected in EDTA. In NaCl, pitting potential occurred at higher values for the electropolished and PVD instruments, indicating an increased corrosion resistance. There appears to be a risk of corrosion for NiTi instruments without surface treatments in contact with NaCl. NiTi files with PVD and electropolishing surface treatments showed an increase corrosion resistance.

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

Caporuscio, Florie Andre; Norskog, Katherine Elizabeth; Maner, James

Over the past five years the Used Fuel Campaign has investigated Engineered Barrier Systems (EBS) at higher heat loads (up to 300°C) and pressure (150 bar). This past year experimental work was hindered due to a revamping of the hydrothermal lab. Regardless, two experiments were run this past year, EBS-18 and EBS-19. EBS-18 was run using Low Carbon Steel (LCS) and opalinus clay in addition to the bentonite and opalinus brine. Many of the past results were confirmed in EBS-18, such as the restriction of illite formation due to the bulk chemistry, pyrite degradation, and zeolite formation dependent on themore » bentonite and opalinus clay. The LCS show vast amounts of pit corrosion (over 100μm of corrosion in six weeks), leading a corrosion rate of 1083 μm/year. In addition, a mineral goethite, an iron-bearing hydroxide, formed in the pits of the LCS. Preliminary results from EBS-19 water chemistry are included but SEM imaging, micro probe and XRD are still needed for further results. Copper corrosion was investigated further and over 850 measurements were taken. It was concluded that pitting and pyrite degradation drastically increase the corrosion rate from 0.12 to 0.39 μm/day. However, the growth of a layer of the mineral chalcocite is thought to subdue the corrosion rate to 0.024 μm/day as observed in the EBS-13, a sixth month experiment. This document presents the findings of this past year.« less

Direct observation of pitting corrosion evolutions on carbon steel surfaces at the nano-to-micro- scales.

PubMed

Guo, Peng; La Plante, Erika Callagon; Wang, Bu; Chen, Xin; Balonis, Magdalena; Bauchy, Mathieu; Sant, Gaurav

2018-05-22

The Cl - -induced corrosion of metals and alloys is of relevance to a wide range of engineered materials, structures, and systems. Because of the challenges in studying pitting corrosion in a quantitative and statistically significant manner, its kinetics remain poorly understood. Herein, by direct, nano- to micro-scale observations using vertical scanning interferometry (VSI), we examine the temporal evolution of pitting corrosion on AISI 1045 carbon steel over large surface areas in Cl - -free, and Cl - -enriched solutions. Special focus is paid to examine the nucleation and growth of pits, and the associated formation of roughened regions on steel surfaces. By statistical analysis of hundreds of individual pits, three stages of pitting corrosion, namely, induction, propagation, and saturation, are quantitatively distinguished. By quantifying the kinetics of these processes, we contextualize our current understanding of electrochemical corrosion within a framework that considers spatial dynamics and morphology evolutions. In the presence of Cl - ions, corrosion is highly accelerated due to multiple autocatalytic factors including destabilization of protective surface oxide films and preservation of aggressive microenvironments within the pits, both of which promote continued pit nucleation and growth. These findings offer new insights into predicting and modeling steel corrosion processes in mid-pH aqueous environments.

Computational fluid dynamics models of conifer bordered pits show how pit structure affects flow.

PubMed

Schulte, Paul J

2012-02-01

• The flow of xylem sap through conifer bordered pits, particularly through the pores in the pit membrane, is not well understood, but is critical for an understanding of water transport through trees. • Models solving the Navier-Stokes equation governing fluid flow were based on the geometry of bordered pits in black spruce (Picea mariana) and scanning electron microscopy images showing details of the pores in the margo of the pit membrane. • Solutions showed that the pit canals contributed a relatively small fraction of resistance to flow, whereas the torus and margo pores formed a large fraction, which depended on the structure of the individual pit. The flow through individual pores in the margo was strongly dependent on pore area, but also on the radial location of the pore with respect to the edge of the torus. • Model results suggest that only a few per cent of the pores in the margo account for nearly half of the flow and these pores tend to be located in the inner region of the margo where their contribution will be maximized. A high density of strands in outer portions of the margo (hence narrower pores) may be more significant for mechanical support of the torus. © 2011 The Author. New Phytologist © 2011 New Phytologist Trust.

Corrosion behavior of stainless steel weldments in physiological solutions

NASA Astrophysics Data System (ADS)

Farooq, A.; Azam, M.; Deen, K. M.

2018-01-01

In this study corrosion behavior of TIG welded 316L stainless steel plates in simulated biological solutions is investigated. The mechanical testing results showed slight decrease in ductility after welding and the fracture surface represented mixed cleavage and inclusions containing dimple structure. The heat affected and weld zone (WZ) demonstrated higher corrosion potential and relatively large pitting tendency than base metal (BM) in both Hank’s and Ringer’s solution. The formation of delta (δ) ferrite in the heat affected and WZ decreased the corrosion resistance as confirmed from potentiodynamic Tafel scans. The decrease in pitting resistance and lower protection tendency of the WZ compared to BM and heat affected zone was also quantified from the cyclic polarization trends.

The effect of oxide film properties on the corrosion behavior of SiC/Al metal-matrix composites

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

Golledge, S.L.

1991-01-01

Oxide growth on pure aluminum, aluminum alloy 6061, and the aluminum-based metal matrix composite SiC/AA6061 was studied, and the properties of the oxides related to the pit-initiation behavior of the materials. The objectives of the work were to identify the effect of alloying elements and SiC reinforcement on the oxide film, and to better understand how the oxide properties control pit initiation behavior. To this end, electrochemical and optical studies of the materials were carried out in a buffered sodium/boric acid solution at pH values of 8.4 and 7.2. The alloy and metal-matrix composite showed a slightly lesser tendency tomore » pit than pure aluminum, as measured by the pitting potential. The oxide on the composite was less resistant to pit initiation, and was found to exhibit slower repassivation rates than the other materials. The repassivation behavior and resistance to pit initiation were quite similar in the case of the alloy and the pure aluminum. Induction times for pit initiation were consistent with the predictions of Heusler's model for the breakdown of passivity.« less

Numerical modelling of the groundwater inflow to an advancing open pit mine: Kolahdarvazeh pit, Central Iran.

PubMed

Bahrami, Saeed; Doulati Ardejani, Faramarz; Aslani, Soheyla; Baafi, Ernest

2014-12-01

The groundwater inflow into a mine during its life and after ceasing operations is one of the most important concerns of the mining industry. This paper presents a hydrogeological assessment of the Irankuh Zn-Pb mine at 20 km south of Esfahan and 1 km northeast of Abnil in west-Central Iran. During mine excavation, the upper impervious bed of a confined aquifer was broken and water at high-pressure flowed into an open pit mine associated with the Kolahdarvazeh deposit. The inflow rates were 6.7 and 1.4 m(3)/s at the maximum and minimum quantities, respectively. Permeability, storage coefficient, thickness and initial head of the fully saturated confined aquifer were 3.5 × 10(-4) m/s, 0.2, 30 m and 60 m, respectively. The hydraulic heads as a function of time were monitored at four observation wells in the vicinity of the pit over 19 weeks and at an observation well near a test well over 21 h. In addition, by measuring the rate of pumping out from the pit sump, at a constant head (usually equal to height of the pit floor), the real inflow rates to the pit were monitored. The main innovations of this work were to make comparison between numerical modelling using a finite element software called SEEP/W and actual data related to inflow and extend the applicability of the numerical model. This model was further used to estimate the hydraulic heads at the observation wells around the pit over 19 weeks during mining operations. Data from a pump-out test and observation wells were used for model calibration and verification. In order to evaluate the model efficiency, the modelling results of inflow quantity and hydraulic heads were compared to those from analytical solutions, as well as the field data. The mean percent error in relation to field data for the inflow quantity was 0.108. It varied between 1.16 and 1.46 for hydraulic head predictions, which are much lower values than the mean percent errors resulted from the analytical solutions (from 1.8 to 5.3 for inflow and from 2.16 to 3.5 for hydraulic head predictions). The analytical solutions underestimated the inflow compared to the numerical model for the time period of 2-19 weeks. The results presented in this paper can be used for developing an effective dewatering program.

Bacterial community composition in the water column of a lake formed by a former uranium open pit mine.

PubMed

Edberg, Frida; Andersson, Anders F; Holmström, Sara J M

2012-11-01

Mining of pyrite minerals is a major environmental issue involving both biological and geochemical processes. Here we present a study of an artificial lake of a former uranium open pit mine with the aim to connect the chemistry and bacterial community composition (454-pyrosequencing of 16S rRNA genes) in the stratified water column. A shift in the water chemistry from oxic conditions in the epilimnion to anoxic, alkaline, and metal and sulfide-rich conditions in the hypolimnion was corresponded by a strong shift in the bacterial community, with few shared operational taxonomic units (OTU) between the water layers. The epilimnetic bacterial community of the lake (~20 years old) showed similarities to other temperate freshwater lakes, while the hypolimnetic bacterial community showed similarity to extreme chemical environments. The epilimnetic bacterial community had dominance of Actinobacteria and Betaproteobacteria. The hypolimnion displayed a higher bacterial diversity and was dominated by the phototrophic green sulphur bacterium of the genus Chlorobium (ca. 40 % of the total community). Deltaproteobacteria were only represented in the hypolimnion and the most abundant OTUs were affiliated with ferric iron and sulfate reducers of the genus Geobacter and Desulfobulbus, respectively. The chemistry is clearly controlling, especially the hypolimnetic, bacterial community but the community composition also indicates that the bacteria are involved in metal cycling in the lake.

Seasonal variations in the sources of natural and anthropogenic lead deposited at the East Rongbuk Glacier in the high-altitude Himalayas.

PubMed

Burn-Nunes, Laurie; Vallelonga, Paul; Lee, Khanghyun; Hong, Sungmin; Burton, Graeme; Hou, Shugui; Moy, Andrew; Edwards, Ross; Loss, Robert; Rosman, Kevin

2014-07-15

Lead (Pb) isotopic compositions and concentrations, and barium (Ba) and indium (In) concentrations have been analysed at sub-annual resolution in three sections from a <110 m ice core dated to the 18th and 20th centuries, as well as snow pit samples dated to 2004/2005, recovered from the East Rongbuk Glacier in the high-altitude Himalayas. Ice core sections indicate that atmospheric chemistry prior to ~1,953 was controlled by mineral dust inputs, with no discernible volcanic or anthropogenic contributions. Eighteenth century monsoon ice core chemistry is indicative of dominant contributions from local Himalayan sources; non-monsoon ice core chemistry is linked to contributions from local (Himalayan), regional (Indian/Thar Desert) and long-range (North Africa, Central Asia) sources. Twentieth century monsoon and non-monsoon ice core data demonstrate similar seasonal sources of mineral dust, however with a transition to less-radiogenic isotopic signatures that suggests local and regional climate/environmental change. The snow pit record demonstrates natural and anthropogenic contributions during both seasons, with increased anthropogenic influence during non-monsoon times. Monsoon anthropogenic inputs are most likely sourced to South/South-East Asia and/or India, whereas non-monsoon anthropogenic inputs are most likely sourced to India and Central Asia. Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical weathering in a tropical watershed, Luquillo Mountains, Puerto Rico III: Quartz dissolution rates

USGS Publications Warehouse

Schulz, M.S.; White, A.F.

1999-01-01

The paucity of weathering rates for quartz in the natural environment stems both from the slow rate at which quartz dissolves and the difficulty in differentiating solute Si contributed by quartz from that derived from other silicate minerals. This study, a first effort in quantifying natural rates of quartz dissolution, takes advantage of extremely rapid tropical weathering, simple regolith mineralogy, and detailed information on hydrologic and chemical transport. Quartz abundances and grain sizes are relatively constant with depth in a thick saprolite. Limited quartz dissolution is indicated by solution rounding of primary angularity and by the formation of etch pits. A low correlation of surface area (0.14 and 0.42 m2 g-1) with grain size indicates that internal microfractures and pitting are the principal contributors to total surface area. Pore water silica concentration increases linearly with depth. On a molar basis, between one and three quarters of pore water silica is derived from quartz with the remainder contributed from biotite weathering. Average solute Si remains thermodynamically undersaturated with respect to recently revised estimates of quartz solubility (17-81 ??M). Etch pitting is more abundant on grains in the upper saprolite and is associated with pore waters lower in dissolved silica. Rate constants describing quartz dissolution increase with decreasing depth (from 10-14.5-10-15.1 mol m-2 s-1), which correlate with both greater thermodynamic undersaturation and increasing etch pit densities. Unlike for many aluminosilicates, the calculated natural weathering rates of quartz fall slightly below the rate constants previously reported for experimental studies (10-12.4-10-14.2 mol m-2 s-1). This agreement reflects the structural simplicity of quartz, dilute solutes, and near-hydrologic saturation.

The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

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

Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com; Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id

The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observedmore » on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.« less

Chemical milling solution produces smooth surface finish on aluminum

NASA Technical Reports Server (NTRS)

Lorenzen, H. C.

1966-01-01

Elementary sulfur mixed into a solution of caustic soda and salts produces an etchant which will chemically mill end-grain surfaces on aluminum plate. This composition results in the least amount of thickness variation and pitting.

Synthesis of a fluorine-free polymeric water-repellent agent for creation of superhydrophobic fabrics

NASA Astrophysics Data System (ADS)

Shen, Keke; Yu, Miao; Li, Qianqian; Sun, Wei; Zhang, Xiting; Quan, Miao; Liu, Zhengtang; Shi, Suqing; Gong, Yongkuan

2017-12-01

A non-fluorinated polymeric alkylsilane, poly(isobutyl methacrylate-co-3-methacryloxypropyltrimethoxysilane) (PIT), is designed and synthesized to replace the commercial long-chain perfluoroalkylsilane (FAS) water-repellent agent. The superhydrophobic polyester fabrics are prepared by anchoring sol-gel derived silica nanoparticles onto alkali-treated polyester fabric surfaces and subsequently hydrophobilizing with PIT, using FAS as control. The surface chemical composition, surface morphology, wetting behavior and durability of the modified polyester fabrics are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrophotometer (XPS) and video-based contact angle goniometer, respectively. The results show that a porous silica layer could be successfully fabricated onto the surface of polyester fabric through base-catalyzed sol-gel process with tetraethoxysilane (TEOS) as precursor, incorporating additional nanostructured roughness essential for superhydrophobicity. At the same time, such a silica primer layer could provide both secondary reactive moieties (-Si - OH) for the subsequent surface hydrophobization and acceptable adhesion at the silica-polyester fabric interface. When silica modified polyester fabric (SiO2@ fabric) is hydrophobized by PIT solution (10 mg/mL), excellent water-repellency could be obtained. The water contact angle is up to 154° and the sliding angle is about 5°. Compared with small molecule water-repellent agent FAS, PIT modified SiO2@ fabric exhibits greatly improved solvent resistance under ultra-sonication, abrasion and simulated laundering durability. The anti-stain property of PIT-modified SiO2@ fabric is also evaluated by using different aqueous colored solutions.

In-Situ Atomic Force Microscope Imaging of Calcite Etch Pit Morphology Changes in Undersaturated and 1-Hydroxyethylidene-1,1-diphosphonic Acid Poisoned Solutions

PubMed Central

Britt, David W.

2012-01-01

Morphology changes in etch pits formed on the (1014) cleavage plane of calcite were induced by varying the ratio of [Ca2+] to [CO32−] in the bulk solution as well as through the addition of the crystal poison 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP). Three distinct morphologies were noted: symmetric rhombic, asymmetric rhombic, and triangular with a rough curved hypotenuse. The latter represents a transient morphology which is only observed during the actual dissolution process, while the former morphologies persist after dissolution is halted. PMID:25125794

A study on chloride induced depassivation of Fe-P-C-Si and Fe-P-C-Si-N steels in simulated concrete pore solution

NASA Astrophysics Data System (ADS)

Mehta, Yashwant; Chaudhari, Gajanan P.; Dabhade, Vikram V.

2018-03-01

The corrosion behaviour of high phosphorous steels containing varying amounts of silicon and nitrogen was studied by potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. The morphology of a steel specimen tested in chloride containing concrete pore solution was studied using scanning electron microscope (SEM) and the elemental distribution at the pitting corrosion area was investigated using electron dispersive spectroscopy (EDS). The results showed that the capacitance increased and resistance declined with immersion time in Ca(OH)2 solution containing 0.1% chloride for plain carbon steel. The opposite was observed in the case of the high phosphorous steels. The potentiodynamic polarization and LPR results complement the EIS findings. Corrosion behaviour could be described with an equivalent circuit having two time constants. The creation, expansion and degradation of the passive layer were discussed with the help of the equivalent circuit elements. The SEM-EDS studies revealed that MnS inclusions at the surface could have a role in the initiation and growth of pits and that phosphorous was present at the pit free surface of the steel.

Study on the corrosion residual strength of the 1.0 wt.% Ce modified AZ91 magnesium alloy

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

Li Chunfang; Liu Yaohui, E-mail: liuyaohui2005@yahoo.com; Wang Qiang

2010-01-15

The effect of corrosion on the tensile behaviour of the 1.0 wt.% Ce modified AZ91 magnesium alloy was investigated by the immersion of the test bar in 3.5 wt.% NaCl aqueous solution for 0, 12, 40, 108, 204, 372 and 468 h with the subsequent tensile tests in this paper. The fractography was analyzed by scanning electron microscopy. The results show that pitting corrosion should be responsible for the drop of the corrosion residual strength within the testing time. The depth of the corrosion pits was statistically and quantitatively obtained by an optical microscopy and the maximal value was recordedmore » as the extreme depth of the corrosion pit. Furthermore, the corrosion residual strength is linearly dependent on the extreme depth of the corrosion pit, which can be attributed to the loss of cross-sectional area and the emergence of stress concentration caused by the initiation and development of corrosion pits.« less

[Investigation on the phenomena of bacteria exceeding standards in rural pit water treated by ultrafiltration membrane].

PubMed

Yue, Yinling; Zhang, Lan; Ling, Bo

2011-11-01

To investigate the phenomenon of bacteria exceeding standards in rural pit water, which was intermittently operated by water pump equipped with ultrafiltration membrane, and to explore the solutions. Polyvinyl chloride (PVC) alloy capillary membranes combined with UV, disinfectant, one-way valve, water-seal, high water level-water tank and direct outlet were tested. The operation on water treatment was intermittent, simulating the ways of treating pit water in the rural. The combination modes of ultrafiltration membrane with UV, disinfectant and high water level-water tank are valid in solving the problem of high turbidity and microorganism of pit water stored in cellars, the quality of effluents was consistent with the requirements of the national standards. While the combination modes of ultrafiltration membrane with one-way valve or water-seal were less desirable, more bacteria in treated water than raw water were observed because of bacteria breeding on the membrane component. In order to avoid excessive bacteria in filtered pit water caused by intermittent operation, it is recommended that for the pit water in high water level water tanks, the ultrafiltration membranes should be cleaned with disinfectants on a regular basis. The effluent pit water from underground cellars should be disinfected with UV after ultrafiltration.

Chemical etching of stainless steel 301 for improving performance of electrochemical capacitors in aqueous electrolyte

NASA Astrophysics Data System (ADS)

Jeżowski, P.; Nowicki, M.; Grzeszkowiak, M.; Czajka, R.; Béguin, F.

2015-04-01

The main purpose of the study was to increase the surface roughness of stainless steel 301 current collectors by etching, in order to improve the electrochemical performance of electrical double-layer capacitors (EDLC) in 1 mol L-1 lithium sulphate electrolyte. Etching was realized in 1:3:30 (HNO3:HCl:H2O) solution with times varying up to 10 min. For the considered 15 μm thick foil and a mass loss around 0.4 wt.%, pitting was uniform, with diameter of pits ranging from 100 to 300 nm. Atomic force microscopy (AFM) showed an increase of average surface roughness (Ra) from 5 nm for the as-received stainless steel foil to 24 nm for the pitted material. Electrochemical impedance spectroscopy realized on EDLCs with coated electrodes either on as-received or pitted foil in 1 mol L-1 Li2SO4 gave equivalent distributed resistance (EDR) of 8 Ω and 2 Ω, respectively, demonstrating a substantial improvement of collector/electrode interface after pitting. Correlatively, the EDLCs with pitted collector displayed a better charge propagation and low ohmic losses even at relatively high current of 20 A g-1. Hence, chemical pitting of stainless steel current collectors is an appropriate method for optimising the performance of EDLCs in neutral aqueous electrolyte.

Types and analysis of defects in welding junctions of the header to steam generator shells on power-generating units with VVER-1000

NASA Astrophysics Data System (ADS)

Ozhigov, L. S.; Voevodin, V. N.; Mitrofanov, A. S.; Vasilenko, R. L.

2016-10-01

Investigation objects were metal templates, which were cut during the repair of welding junction no. 111 (header to the steam generator shell) on a power-generating unit with VVER-1000 of the South-Ukraine NPP, and substances of mud depositions collected from walls of this junction. Investigations were carried out using metallography, optical microscopy, and scanning electron microscopy with energy dispersion microanalysis by an MMO-1600-AT metallurgical microscope and a JEOL JSM-7001F scanning electron microscope with the Shottky cathode. As a result of investigations in corrosion pits and mud depositions in the area of welding junction no. 111, iron and copper-enriched particles were revealed. It is shown that, when contacting with the steel header surface, these particles can form microgalvanic cells causing reactions of iron dissolution and the pit corrosion of metal. Nearby corrosion pits in metal are microcracks, which can be effect of the stress state of metal under corrosion pits along with revealed effects of twinning. The hypothesis is expressed that pitting corrosion of metal occurred during the first operation period of the power-generating unit in the ammonia water chemistry conditions (WCC). The formation of corrosion pits and nucleating cracks from them was stopped with the further operation under morpholine WCC. The absence of macrocracks in metal of templates verifies that, during operation, welding junction no. 111 operated under load conditions not exceeding the permissible ones by design requirements. The durability of the welding junction of the header to the steam generator shell significantly depends on the technological schedule of chemical cleaning and steam generator shut-down cooling.

Studying localized corrosion using liquid cell transmission electron microscopy

DOE PAGES

Chee, See Wee; Pratt, Sarah H.; Hattar, Khalid; ...

2014-11-07

Using liquid cell transmission electron microscopy (LCTEM), localized corrosion of Cu and Al thin films immersed in aqueous NaCl solutions was studied. We demonstrate that potentiostatic control can be used to initiate pitting and that local compositional changes, due to focused ion beam implantation of Au + ions, can modify the corrosion susceptibility of Al films. Likewise, a discussion on strategies to control the onset of pitting is also presented.

Influences of Cr/Ni equivalent ratios of filler wires on pitting corrosion and ductility-dip cracking of AISI 316L weld metals

NASA Astrophysics Data System (ADS)

Kim, Y. H.; Kim, D. G.; Sung, J. H.; Kim, I. S.; Ko, D. E.; Kang, N. H.; Hong, H. U.; Park, J. H.; Lee, H. W.

2011-02-01

To study the pitting corrosion of AISI 316L weld metals according to the chromium/nickel equivalent ratio (Creq/Nieq ratio), three filler wires were newly designed for the flux-cored arc welding process. The weld metal with delta-ferrite at less than 3 vol.%, was observed for ductility-dip cracking (DDC) in the reheated region after multi-pass welding. The tensile strength and yield strength increased with increasing Creq/Nieq ratio. The result of anodic polarization tests in a 0.1 M NaCl solution at the room temperature (25) for 45 min, revealed that the base metal and weld metals have a similar corrosion potential of -0.34 VSCE. The weld metal with the highest content of Cr had the highest pitting potential (0.39 VSCE) and the passivation range (0.64 VSCE) was higher than the base metal (0.21 VSCE and 0.46 VSCE, respectively). Adding 0.001 M Na2S to the 0.1M NaCl solution, the corrosion occurred more severely by H2S. The corrosion potentials of the base metal and three weld metals decreased to -1.0 VSCE. DDC caused the decrease of the pitting potential by inducing a locally intense corrosion attack around the crack openings.

Microbiologically Influenced Corrosion: Causative Organisms and Mechanisms

DTIC Science & Technology

2012-01-31

corrosion is both predictable and complex. In aquatic environments and under some atmospheric conditions . microorganisms settle on surfaces and alter the...some atmospheric conditions , microorganisms settle on sin laces and alter the surface chemistry controlling the rates of corrosion or shifting the...pitting corrosion of some allO) S continues under deposits of iron-oxidizing bacteria independent of bacterial activity. Similarly, microbiologicall

STABLE ISOTOPE STUDIES ON THE USE OF MARINE-DERIVED NUTRIENTS BY COHO SALMON JUVENILES IN AN OREGON COAST RANGE STREAM

EPA Science Inventory

We are using stable isotopes (13C, 15N, 34S) to study the use of salmon carcasses, eggs and fry by over-wintering coho juveniles in two streams of the Oregon Coast Range. Our work is paired with detailed data gathering on stream habitat condition, temperature, chemistry and PIT-t...

New insights into the mechanisms of water-stress-induced cavitation in conifers.

PubMed

Cochard, Hervé; Hölttä, Teemu; Herbette, Stéphane; Delzon, Sylvain; Mencuccini, Maurizio

2009-10-01

Cavitation resistance is a key parameter to understand tree drought tolerance but little is known about the mechanisms of air entry into xylem conduits. For conifers three mechanisms have been proposed: (1) a rupture of pit margo microfibrils, (2) a displacement of the pit torus from its normal sealing position over the pit aperture, and (3) a rupture of an air-water menisci in a pore of the pit margo. In this article, we report experimental results on three coniferous species suggesting additional mechanisms. First, when xylem segments were injected with a fluid at a pressure sufficient to aspirate pit tori and well above the pressure for cavitation induction we failed to detect the increase in sample conductance that should have been caused by torus displacement from blocking the pit aperture or by membrane rupture. Second, by injecting xylem samples with different surfactant solutions, we found a linear relation between sample vulnerability to cavitation and fluid surface tension. This suggests that cavitation in conifers could also be provoked by the capillary failure of an air-water meniscus in coherence with the prediction of Young-Laplace's equation. Within the bordered pit membrane, the exact position of this capillary seeding is unknown. The possible Achilles' heel could be the seal between tori and pit walls or holes in the torus. The mechanism of water-stress-induced cavitation in conifers could then be relatively similar to the one currently proposed for angiosperms.

Groundwater and surface water interaction in flow-through gravel pit lakes.

NASA Astrophysics Data System (ADS)

Nella Mollema, Pauline; Antonellini, Marco

2015-04-01

Gravel pits are excavated in aquifers to fulfill the need for construction materials. Flow-through lakes form when the gravel pits are below the water table and fill with groundwater. In certain areas there are more than 60 of these lakes close together and their presence changes the drainage patterns and water- and hydrochemical budgets of a watershed. In flow-through gravel pit lakes, groundwater mixes with surface water and interacts with the atmosphere; outflow occurs only via groundwater. The lifespan of gravel pit lakes may be up to thousands of years as their depth to surface ratio is typically large and sedimentation rates are low. We have studied two gravel pit lake systems, a fluvial freshwater system in the Netherlands and a coastal brackish lake system in Italy. One Dutch gravel pit lake studied in detail is in part artificially replenished with Meuse River water for drinking water production that occurs downstream of the lake by water pumps. The Italian gravel pit lakes are fed by brackish groundwater that is a mix of freshwater from precipitation, Apennine Rivers and brackish (Holocene) Adriatic Sea water. Here, the drainage system of the low lying land enhances groundwater flow into the lake. Surface water evaporation is larger in temperate and Mediterranean climates than the actual evapotranspiration of pre-existing grassland and forests. The lakes, therefore, cause a loss of freshwater. The creation of water surfaces allows algae and other flora and fauna to develop. In general, water becomes gradually enriched in certain chemical constituents on its way through the hydrological cycle, especially as groundwater due to water-rock interactions. When groundwater ex-filtrates into gravel pit lakes, the natural flow of solutes towards the sea is interrupted. Hydrochemical analysis of ground- and surface waters, as well as chemical analysis of lake bottom sediments and stable H and O isotope data, show that gravel pit lake water is characterized (among others) by a higher pH, O2 and alkalinity and lower dissolved metal and certain trace concentrations than natural lakes and groundwater. In both settings, groundwater rich in dissolved elements (e.g. Al, As, Fe, Mn, Ni and PO43) flows into the gravel pit lakes where the pH and DO are high, which enhances the (co)precipitation of Fe, Mn and Al oxides that include trace elements. Metal concentrations in the Dutch lake's bottom sediments have increased over a 10 year period. Redox reactions caused by water table lowering and farmland fertilization upstream from the lake explain the metals mobilization and subsequent transport with groundwater towards the lakes. The gravel pit lakes, especially if there are many close together, influence so the cycle of water metals, nutrients as well as other trace elements of a watershed by incorporating them into biomass and bottom sediments or creating an environment where they can remain in concentrated solution.

Characterization of Etch Pit Formation via the Everson-Etching Method on CdZnTe Crystal Surfaces from the Bulk to the Nano-Scale

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

Teague, L.; Duff, M.; Cadieux, J.

2010-09-24

A combination of atomic force microscopy, optical microscopy, and mass spectrometry was employed to study CdZnTe crystal surface and used etchant solution following exposure of the CdZnTe crystal to the Everson etch solution. We discuss the results of these studies in relationship to the initial surface preparation methods, the performance of the crystals as radiation spectrometers, the observed etch pit densities, and the chemical mechanism of surface etching. Our results show that the surface features that are exposed to etchants result from interactions with the chemical components of the etchants as well as pre-existing mechanical polishing.

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments

PubMed Central

Yang, Zixuan; Kan, Bo; Li, Jinxu; Su, Yanjing; Qiao, Lijie; Volinsky, Alex A.

2017-01-01

Inclusion-induced pitting initiation mechanisms in X70 steel were investigated by scanning electron microscopy, scanning Kelvin probe force microscopy (SKPFM), immersion and electrochemical polarization tests in chloride-containing ion solutions. There are three inclusion types in the X70 steel. Corrosion test results indicated that pitting corrosion resistance of type A inclusion < type C inclusion < type B inclusion, i.e., (Mn, Ca)S < matrix < (Al, Ca)O. SKPFM test results show that the type A inclusion exhibited both lower and higher potentials than the matrix, while the type B inclusion exhibited higher potential than the matrix. The corrosion test and the SKPFM potential test results are consistent. Potentiodynamic polarization results indicate that the type A and C are active inclusions, while the type B is an inactive inclusion. Three kinds of possible mechanisms of inclusion-induced pitting corrosion are established for the X70 steel. PMID:28902156

Group traction drive as means to increase energy efficiency of lokomotives of open-pit transport

NASA Astrophysics Data System (ADS)

Antipin, D. Ya; Izmerov, O. V.; Bishutin, S. G.; Kobishchanov, V. V.

2017-10-01

Questions of possible use of a group drive for locomotives of an open-pit transport are considered. The possibility of a significant reduction of traction costs in the case of a combination of a group traction drive with devices for the non-inertial regulation of the coefficient of friction between the wheel and the rail has been shown, and new patentable solutions have been proposed.

[Study on electrochemical mechanism of coronary stent used austenitic stainless steel in flowing artificial body fluid].

PubMed

Liang, Chenghao; Guo, Liang; Chen, Wan; Wang, Hua

2005-08-01

The electrochemical mechanism of austenitic stainless steel (SUS316L and SUS317L) coronary stents in flowing artificial body fluid has been investigated with electrochemical technologies. The results indicated that the flowing medium coursed the samples' pitting potential Eb shift negatively, increased the pitting corrosion sensitivity, accelerated its anodic dissolution, but had little effects on repassivated potential. The flowing environment had great effects on cathodic process. The oxygen reaction on the samples' surface became faster as the cathodic process was not controlled by oxygen diffusion but by mixed diffusion and electrochemical process. With the increase of velocity of solution, the pitting corrosion becomes liable to occur under this circumstance.

EFFECTS OF CHEMISTRY AND OTHER VARIABLES ON CORROSION AND STRESS CORROSION CRACKING IN HANFORD DOUBLE SHELL TANKS

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

BROWN MH

2008-11-13

Laboratory testing was performed to develop a comprehensive understanding of the corrosivity of the tank wastes stored in Double-Shell Tanks using simulants primarily from Tanks 241-AP-105, 241-SY-103 and 241-AW-105. Additional tests were conducted using simulants of the waste stored in 241-AZ-102, 241-SY-101, 241-AN-107, and 241-AY-101. This test program placed particular emphasis on defining the range of tank waste chemistries that do not induce the onset of localized forms of corrosion, particularly pitting and stress corrosion cracking. This document summarizes the key findings of the research program.

Mitigating Localized Corrosion Using Thermally Sprayed Aluminum (TSA) Coatings on Welded 25% Cr Superduplex Stainless Steel

NASA Astrophysics Data System (ADS)

Paul, S.; Lu, Q.; Harvey, M. D. F.

2015-04-01

Thermally sprayed aluminum (TSA) coating has been increasingly used for the protection of carbon steel offshore structures, topside equipment, and flowlines/pipelines exposed to both marine atmospheres and seawater immersion conditions. In this paper, the effectiveness of TSA coatings in preventing localized corrosion, such as pitting and crevice corrosion of 25% Cr superduplex stainless steel (SDSS) in subsea applications, has been investigated. Welded 25% Cr SDSS (coated and uncoated) with and without defects, and surfaces coated with epoxy paint were also examined. Pitting and crevice corrosion tests, on welded 25% Cr SDSS specimens with and without TSA/epoxy coatings, were conducted in recirculated, aerated, and synthetic seawater at 90 °C for 90 days. The tests were carried out at both the free corrosion potentials and an applied cathodic potential of -1100 mV saturated calomel electrode. The acidity (pH) of the test solution was monitored daily and adjusted to between pH 7.5 and 8.1, using dilute HCl solution or dilute NaOH, depending on the pH of the solution measured during the test. The test results demonstrated that TSA prevented pitting and crevice corrosion of 25% Cr SDSS in artificial seawater at 90 °C, even when 10-mm-diameter coating defect exposing the underlying steel was present.

Enhancement of Device Performances in GaN-Based Light-Emitting Diodes Using Nano-Sized Surface Pit.

PubMed

Yeon, Seunghwan; Son, Taejoon; Shin, Dong Su; Jung, Kyung-Young; Park, Jinsub

2015-07-01

We report the improvement in optical and electrical properties of GaN-based green light-emitting diodes (LEDs) with nano-sized etch pits formed by the surface chemical etching. In order to control the density and sizes of etch pits formed on top surface of green LEDs, H3PO4 solution is used as a etchant with different etching time. When the etching time was increased from 0 min to 20 min, both the etch pit size and density were gradually increased. The improvement of extraction efficiency of LEDs using surface etching method can be attributed to the enlarged escape angle of generated photon by roughened p-GaN surface. The finite-difference time-domain (FDTD) simulation results well agreed with experimentally observed results. Moreover, the LED with etched p-GaN surface for 5 min shows the lowest leakage current value and the further increase of etching time resulting in increase of densities of the large-sized etch pit makes the degradation of electrical properties of LEDs.

Electrochemical Behavior of Al-B4C Metal Matrix Composites in NaCl Solution

PubMed Central

Han, Yu-Mei; Chen, X.-Grant

2015-01-01

Aluminum based metal matrix composites (MMCs) have received considerable attention in the automotive, aerospace and nuclear industries. One of the main challenges using Al-based MMCs is the influence of the reinforcement particles on the corrosion resistance. In the present study, the corrosion behavior of Al-B4C MMCs in a 3.5 wt.% NaCl solution were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. Results indicated that the corrosion resistance of the composites decreased when increasing the B4C volume fraction. Al-B4C composite was susceptible to pitting corrosion and two types of pits were observed on the composite surface. The corrosion mechanism of the composite in the NaCl solution was primarily controlled by oxygen diffusion in the solution. In addition, the galvanic couples that formed between Al matrix and B4C particles could also be responsible for the lower corrosion resistance of the composites. PMID:28793574

Designing local solutions for emptying pit latrines in low-income urban settlements (Malawi)

NASA Astrophysics Data System (ADS)

Chipeta, W. C.; Holm, R. H.; Kamanula, J. F.; Mtonga, W. E.; de los Reyes, F. L.

2017-08-01

A lack of effective options in local technology poses challenges when onsite household sanitation facilities are eventually filled to capacity in unplanned settlement areas within Mzuzu City, located in northern Malawi. Vacuum trucks currently dominate the market but focus on emptying septic tanks in the more easily accessible planned settlement areas, rather than servicing the pit latrines common in unplanned settlement areas. As a result, households in the unplanned settlement areas within Mzuzu rely primarily on manual pit emptying (i.e., shoveling by hand) or digging a new pit latrine. These practices have associated health risks and are limited by space constraints. This research focused on filling the technological gap through the design, development, and testing of a pedal powered modified Gulper pump using locally available materials and fabrication. A modified pedal powered Gulper technology was developed and demonstrated to be capable of lifting fecal sludge from a depth of 1.5 m with a mean flow rate of 0.00058 m3/s. If the trash content was low, a typical pit latrine with a volume of 1-4 m3 could be emptied within 1-2 h. Based on the findings in our research Phase IV, the pedal powered Gulper modification is promising as a potential emptying technology for lined pit latrines in unplanned settlement areas. The success rate of the technology is about 17% (5 out 30 sampled lined pit latrines were successful) and reflects the difficulty in finding a single technology that can work well in all types of pit latrines with varying contents. We note that cost should not be the only design criteria and acknowledge the challenge of handling trash in pit latrines.

Non-destructive measurement of demineralization and remineralization in the occlusal pits and fissures of extracted 3rd molars with PS-OCT

NASA Astrophysics Data System (ADS)

Lee, Chulsung; Hsu, Dennis J.; Le, Michael H.; Darling, Cynthia L.; Fried, Daniel

2009-02-01

Previous studies have demonstrated that Polarization Sensitive Optical Coherence Tomography (PS-OCT) can be used to image the remineralization of early artificial caries lesion on smooth enamel surfaces of human and bovine teeth. However, most new dental decay is found in the pits and fissures of the occlusal surfaces of posterior dentition and it is in these high risk areas where the performance of new caries imaging devices need to be investigated. The purpose of this study was to demonstrate that PS-OCT can be used to measure the subsequent remineralization of artificial lesions produced in the pits and fissures of extracted 3rd molars. A PS-OCT system operating at 1310-nm was used to acquire polarization resolved images of occlusal surfaces exposed to a demineralizing solution at pH-4.5 followed by a fluoride containing remineralizing solution at pH-7.0 containing 2-ppm fluoride. The integrated reflectivity was calculated to a depth of 200-µm in the entire lesion area using an automated image processing algorithm. Although a well-defined surface zone was clearly resolved in only a few of the samples that underwent remineralization, the PS-OCT measurements indicated a significant (p<0.05) reduction in the integrated reflectivity between the severity of the lesions that were exposed to the remineralization solution and those that were not. The lesion depth and mineral loss were also measured with polarized light microscopy and transverse microradiography after sectioning the teeth. These results show that PS-OCT can be used to non-destructively monitor the remineralization potential of anti-caries agents in the important pits and fissures of the occlusal surface.

Hanford Double Shell Waste Tank Corrosion Studies - Final Report FY2015

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

Fuentes, R. E.; Wyrwas, R. B.

2016-05-01

During FY15, SRNL performed corrosion testing that supported Washington River Protection Solutions (WRPS) with their double shell tank (DST) integrity program. The testing investigated six concerns including, 1) the possibility of corrosion of the exterior of the secondary tank wall; 2) the effect of ammonia on vapor space corrosion (VSC) above waste simulants; 3) the determination of the minimum required nitrite and hydroxide concentrations that prevent pitting in concentrated nitrate solutions (i.e., waste buffering); 4) the susceptibility to liquid air interface (LAI) corrosion at proposed stress corrosion cracking (SCC) inhibitor concentrations; 5) the susceptibility of carbon steel to pitting inmore » dilute solutions that contain significant quantities of chloride and sulfate; and 6) the effect of different heats of A537 carbon steel on the corrosion response. For task 1, 2, and 4, the effect of heat treating and/ or welding of the materials was also investigated.« less

Ultrasonic Corrosion Fatigue Behavior of High Strength Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Ebara, R.; Yamaguchi, Y.; Kanei, D.; Yamamoto, Y.

Ultrasonic corrosion fatigue tests were conducted for high strength austenitic stainless steels such as YUS270 and SUS304N2 in 3%NaCl aqueous solution. The reduction of giga-cycle corrosion fatigue strength of YUS270 and SUS304N2 was not observed at all, while the reduction of corrosion fatigue life was observed at higher stress amplitude. Corrosion pit was observed on corrosion fatigue crack initiation area. Striation was predominantly observed on crack propagation area in air and in 3% NaCl aqueous solution. The reduction of corrosion fatigue strength of high strength austenitic stainless steels such as YUS270 and SUS304N2 is due to the corrosion pit formation at corrosion fatigue crack initiation area. It can be concluded that the higher the ultimate tensile strength of austenitic stainless steels the higher the giga-cycle corrosion fatigue strength in 3%NaCl aqueous solution is.

Characterization of Localized Corrosion in an Al-Cu-Li Alloy

NASA Astrophysics Data System (ADS)

Luo, Chen; Zhang, Xinxin; Zhou, Xiaorong; Sun, Zhihua; Zhang, Xiaoyun; Tang, Zhihui; Lu, Feng; Thompson, George E.

2016-05-01

Corrosion behaviors of recently developed 2A97-T6 aluminum-copper-lithium alloy in sodium chloride solution are investigated using scanning electron and transmission electron microscopies in conjunction with electron backscatter diffraction. It has been found that corrosion product rings were established on the alloy surface as early as 5 min during immersion in sodium chloride solution. Meanwhile, hydrogen continuously evolved from within the rings. Pitting corrosion is evident with crystallographic dependant corrosion channel facets mainly parallel to {100} planes. Non-uniform distribution of misorientation in the 2A97 aluminum alloy results in a portion of grains of relatively high stored energy. Such grains were preferentially attacked, serving as local anodes, during the development of crystallographic pitting.

Dissolution of uranophane: An AFM, XPS, SEM and ICP study

NASA Astrophysics Data System (ADS)

Schindler, Michael; Freund, Michael; Hawthorne, Frank C.; Burns, Peter C.; Maurice, Patricia A.

2009-05-01

Dissolution experiments on single crystals of uranophane and uranophane-β, Ca(H 2O) 5[(UO 2)(SiO 3(OH)] 2, from the Shinkolobwe mine of the Democratic Republic of Congo, were done in an aqueous HCl solution of pH 3.5 for 3 h, in HCl solutions of pH 2 for 5, 10 and 30 min, and in Pb 2+-, Ba-, Sr-, Ca- and Mg-HCl solutions of pH 2 for 30 min. The basal surfaces of the treated uranophane crystals were examined using atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Solutions after dissolution experiments on single crystals and synthetic powders were analysed with inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectroscopy (ICP-MS). The morphology of the observed etch pits (measured by AFM) were compared to the morphology, predicted on the basis of the bond-valence deficiency of polyhedron chains along the edges of the basal surface. Etch pits form in HCl solutions of pH 2. Their decrease in depth with the duration of the dissolution experiment is explained with the stepwave dissolution model, which describes the lowering of the surrounding area of an etch pit with continuous waves of steps emanated from the etch pit into the rest of the crystal surface. Hillocks form in an HCl solution of pH 3.5, and the chemical composition of the surface (as indicated by XPS) shows that these hillocks are the result of the precipitation of a uranyl-hydroxy-hydrate phase. Well-orientated hillocks form on the surface of uranophane in a SrCl 2-HCl solution of pH 2. They are part of an aged silica coating of composition Si 2O 2(OH) 4(H 2O) n. An amorphous layer forms on the surface of uranophane in a MgCl 2-HCl solution of pH 2, which has a composition and structure similar to silicic acid. Small crystallites of uranyl-hydroxy-hydrate phases form on the surface of uranophane after treatment in Pb(NO 3) 2-HCl and BaCl 2-HCl solutions of pH 2. Dissolution experiments on synthetic uranophane powders show that in the early stage of the experiments, the dissolution rate of uranophane increase in the sequence Pb(NO 3) 2-HCl < BaCl 2-HCl < CaCl 2-HCl < HCl < SrCl 2-HCl < MgCl 2-HCl, indicating that the dissolution of uranophane is more enhanced in solutions containing divalent cations of small ionic radii and high Lewis acidity (Mg, MgCl +).

On the influence of etch pits in the overall dissolution rate of apatite basal sections

NASA Astrophysics Data System (ADS)

Alencar, Igor; Guedes, Sandro; Palissari, Rosane; Hadler, Julio C.

2015-09-01

Determination of efficiencies for particle detection plays a central role for proper estimation of reaction rates. If chemical etching is employed in the revelation of latent particle tracks in solid-state detectors, dissolution rates and etchable lengths are important factors governing the revelation and observation. In this work, the mask method, where a reference part of the sample is protected during dissolution, was employed to measure step heights in basal sections of apatite etched with a nitric acid, HNO, solution at a concentration of 1.1 M and a temperature of 20 °C. We show a drastic increase in the etching velocity as the number of etch pits in the surface augments, in accordance with the dissolution stepwave model, where the outcrop of each etch pit generates a continuous sequence of stepwaves. The number of etch pits was varied by irradiation with neutrons and perpendicularly incident heavy ions. The size dependence of the etch-pit opening with etching duration for ion (200-300 MeV 152Sm and 238U) tracks was also investigated. There is no distinction for the etch pits between the different ions, and the dissolution seems to be governed by the opening velocity when a high number of etch pits are present in the surface. Measurements of the etchable lengths of these ion tracks show an increase in these lengths when samples are not pre-annealed before irradiation. We discuss the implications of these findings for fission-track modelling.

Functional ectopic adrenal carcinoma in a dog

PubMed Central

Taylor, Jim A.; Lee, Maris S.; Nicholson, Matthew E.; Justin, Robert B.

2014-01-01

An 11-year-old spayed female pit bull terrier was presented with a 2-month history of polyuria, polydipsia, polyphagia, and panting. Serum chemistry, blood and urine analysis, and tests for hyperadrenocorticism suggested an adrenal tumor. Abdominal ultrasound identified a mass caudal to the right kidney. The mass was completely excised and histopathology was consistent with endocrine carcinoma. Three years later there was no evidence of recurrence or metastasis. PMID:25183891

113. ARAI Hot cell (ARA626) Building wall sections and details ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

113. ARA-I Hot cell (ARA-626) Building wall sections and details of radio chemistry lab. Shows high-bay roof over hot cells and isolation rooms below grade storage pit for fuel elements. Norman Engineering Company: 961-area/SF-626-A-4. Date: January 1959. Ineel index code no. 068-0626-00-613-102724. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

Investigation of corrosion protection performance of sol-gel surface treatments on AA2024-T3

NASA Astrophysics Data System (ADS)

Voevodin, Natalia Nikolajevna

The dissertation research project addresses the technologically important problem of replacement of chromate based coatings for corrosion protection of aircraft. A review of corrosion processes in high-strength aluminum alloys indicated that the strengthening intermetallic precipitates provide local cathodic areas, which may initiate surface pitting. The mechanisms of chromate inhibition in these localized corrosion processes were identified. The environmental hazard of chromates was also highlighted, serves as the impetus for chromate coating replacement. Sol-gel coatings are shown as an excellent alternative, based on environment compliance, flexibility in the composition control, and reasonable costs. Several sol-gel coatings were formulated and applied to the surface of an AA2024-T3 alloy. The coating composition and bonding were analyzed with XPS and FTIR, surface morphology was studied with SEM and AFM, and corrosion protection properties were tested with EIS, PDS, salt water immersion, and salt-fog exposure. The results demonstrated that epoxy-zirconate sol-gel coatings can provide excellent barrier properties. A novel SVET technique was applied for studies of local electrochemical processes in the pitting formation. This technique was further refined in model studies of aluminum surfaces with artificially created local cathodic regions, experimental studies of chromate inhibition with pit formation, and pitting development studies in sol-gel coatings with artificially introduced defects. Mechanisms of pitting development and inhibition with the pit initiation and growth kinetics were established. The Zr-epoxy coatings are subjected to the pit development and undercutting in the absence of the corrosion inhibitors. Several organic and non-organic inhibitors were evaluated in the sol-gel coating composition. Organic inhibitors had a better compliance with sol-gel chemistry and were identified for future studies. Experiments were performed to verify that sol-gel coatings can be used as barrier layers in complex coating systems. The results clearly demonstrated that Zr-epoxy sol-gel coatings are a viable replacement for the currently used chromate-based surface treatments. This work expands the fundamental knowledge of chromate coating replacement with chromate-free sol-gel coatings and identifies possible ways to implement this goal.

Characterization of the corrosion resistance of several alloys to dilute biologically active solutions

NASA Technical Reports Server (NTRS)

Walsh, Daniel W.

1990-01-01

Sulfate reducing bacteria and acid producing bacteria/fungi detected in hygiene waters increased the corrosion rate in aluminum alloy. Biologically active media enhanced the formation of pits on metal coupons. Direct observation of gas evolved at the corrosion sample, coupled with scanning electron microscopy (SEM) and energy dispersive x-ray analysis of the corrosion products indicates that the corrosion rate is increased because the presence of bacteria favor the reduction of hydrogen as the cathodic reaction through the reaction of oxygen and water. SEM verifies the presence of microbes in a biofilm on the surface of corroding samples. The bacterial consortia are associated with anodic sites on the metal surface, aggressive pitting occurs adjacent to biofilms. Many pits are associated with triple points and inclusions in the aluminum alloy microstructure. Similar bacterial colonization was found on the stainless steel samples. Fourier transform Infrared Spectroscopy confirmed the presence of carbonyl groups in pitted areas of samples exposed to biologically active waters.

Application of wire beam electrode technique to investigate initiation and propagation of rebar corrosion

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

Shi, Wei; Dong, Ze Hua, E-mail: zehua.dong@gmail.com; Kong, De Jie

Multi-electrode technique named as wire beam electrode (WBE) was used to study pitting corrosion of rebar under concrete cover. When WBE embedded mortar sample was immersed in NaCl solution, uneven distributions of galvanic current and open circuit potential (OCP) on the WBE were observed due to the initiation of pitting corrosion. The following oxygen depletion in mortar facilitated the negative shift of the OCP and the smoothing of the current and potential distributions. Wetting–drying cycle experiments showed that corrosion products instead of oxygen in wet mortar specimen sustained the propagation of pitting corrosion due to Fe (III) taking part inmore » cathodic depolarization during oxygen-deficient wet period, which was confirmed by micro-Raman spectroscopy. In addition, new pitting corrosion occurred mainly near the corrosion products, leading to preferentially horizontal propagation of rust layer on the WBE. A localized corrosion factor was further presented to quantify the localised corrosion based on galvanic current maps.« less

The Effect of Surface Patterning on Corrosion Resistance of Biomedical Devices

NASA Astrophysics Data System (ADS)

Guo, Mengnan; Toloei, Alisina; Rotermund, Harm H.

2016-10-01

In this study, two styles of surface topographies have been created on stainless steel wires to test their corrosion resistance as simulated implanted biomedical devices. Grade 316 LVM stainless steel wire was initially polished to G1500 surface finish before treatment to produce the two different topographies: 1. Unidirectional roughness was created using SiC papers and 2. Various patterns were created with specific hole diameter and inter-hole spacing using focused ion beam (FIB). In order to simulate the environment of implanted biomedical devices, a three-electrode electrochemical cell with 0.9% (by mass) NaCl solution has been used to test the corrosion resistance of the samples by potentiodynamic polarization test method. SEM and EDS analyzed the appearance and chemical composition of different elements including oxygen on the surface. The potential of stable pitting, time related to the initiation of the stable pitting, and the highest corrosion current associated with stable pitting have been compared for samples with the two styles of topography. It was found that surfaces with patterns have a relatively higher pitting potential and it takes longer time to initiate stable pitting than the surface without any patterns.

Seasonal variations of snow chemistry and mineral dust in the snow pit at GV7, Antarctica

NASA Astrophysics Data System (ADS)

Kang, Jung-Ho; Hwang, Heejin; Han, Yongchoul; Hong, Sang Bum; Lee, Khanghyun; Do Hur, Soon; Frezzotti, Massimo; Narcisi, Biancamaria

2015-04-01

We conducted the scientific ice coring project led by PNRA and KOPRI during the 2013/2014 Italian-Korean Antarctic Expedition in the framework of International Partnerships in Ice Core Science (IPICS) to understand the climatic variability in the last 2000 years. In the part of project, we collected a 3.0 m-depth snow pit at the site of GV7 (S 70° 41'17.1", E 158° 51'48.9", 1950 m a.s.l.), Antarctica. Here, we present the results obtained from the analysis of the water isotope compositions, the major ion concentrations, and the mineral dust concentrations from the snow pit. Snow densities and temperatures also measured in the field. At KOPRI, the samples were melted, then the stable water isotopes, major ions, and particle size distribution were analyzed with the cavity ring-down spectrometers (L1102-i, Piccaro), ion chromatography (ICS-2100, Thermo), and coulter counter (Multisizer 3, Beckman Coulter), respectively. The δ18O varies between -38.3 and -24.1o with a mean value of -31.0o. The δD ranges between -331 and -186o with a mean value of -243o. Among the ion concentrations (Na+, Ca2+, Mg2+, Cl-, SO42-, CH3SO3-(MSA)) from the snow pit, MSA concentrations show a clear seasonal variation. The mineral dust in the pit characterized with the differences of the concentration and the particle size distribution by the seasonality. These data allow us to assume about 4.5 years of snow deposition covered from 2009 to 2013 by these oscillations of the isotopes and geochemical characteristics.

The Significance of the Origin of Physical Chemistry for Physical Chemistry Education: The Case of Electrolyte Solution Chemistry

ERIC Educational Resources Information Center

de Berg, Kevin Charles

2014-01-01

Physical Chemistry's birth was fraught with controversy, a controversy about electrolyte solution chemistry which has much to say about how scientific knowledge originates, matures, and responds to challenges. This has direct implications for the way our students are educated in physical chemistry in particular and science in general. The…

Evaluation of pitting corrosion resistance of high-alloyed stainless steels welds for FGD plants in Korea

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

Baek, K.K.; Sung, H.J.; Im, C.S.

1998-12-31

For successful application of high-alloyed stainless steels for Flue Gas Desulfurization (FGD) plants, pitting corrosion resistance of arc welds of N-added 6%Mo austenitic stainless steels (UNS N 08367) and super duplex stainless steels (UNS S 32550) made with various filler metals were evaluated using the Green Death solution. For Gas Tungsten Arc (GTA) and Gas Metal Arc (GMA) welds of N 08367, Critical Pitting Temperature (CPT) of base metal was 65--70 C, whereas weld made by ERNiCrMo-3 filler metal yielded CPT of 50 C. Welds made by ERNiCrMo-10 or ERNiCrMo-4 filler metals showed CPT of 60--65 C and 65--70C, respectively.more » For GTA and GMA welds of S 32550, CPT of welds made by ERNiCrMo-3 was 45--50 C, indicating that the filler metal can provide pitting corrosion resistance matching the S 32550 alloy. Thus, a proper pitting corrosion resistance of weldments of high-alloy stainless steels can be achieved by selecting filler metals having at least +10 higher Pitting Resistance Equivalent Number (PRE{sub N}) value than the base metal regardless of the type of arc welding process. The over-alloyed filler metals would compensate preferential segregation of Cr, MO along the dendrite boundary, which made the dendrite core more susceptible to pitting. Nitrogen addition to the GTA welds of N 08367 made with ERNiCrMo-3 failed to improve pitting corrosion resistance, which was attributed to the precipitation of nitrogen in the weld metal in the form of Nb-nitride.« less

Surface chemistry and wear behavior of single-crystal silicon carbide sliding against iron at temperatures to 1500 C in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron and Auger electron spectroscopy analyses and morphological studies of wear and metal transfer were conducted with a single-crystal silicon carbide 0001 surface in contact with iron at various temperatures to 1500 C in a vacuum of 10 to the minus 8th power pascal. The results indicate that below 800 C, carbide-carbon and silicon are primarily seen on the silicon carbide surface. Above 800 C the graphite increases rapidly with increase in temperature. The outermost surficial layer, which consists mostly of graphite and little silicon at temperatures above 1200 C is about 2 nm thick. A thicker layer, which consists of a mixture of graphite, carbide, and silicon is approximately 100 nm thick. The closer the surface sliding temperature is to 800 C, the more the metal transfer produced. Above 800 C, there was a transfer of rough, discontinuous, and thin iron debris instead of smooth, continuous and thin iron film which was observed to transfer below 800 C. Two kinds of fracture pits were observed on the silicon carbide surface: (1) a pit with a spherical asperity; and (2) multiangular shaped pits.

Corrosion behavior and pitting susceptibility of in-situ Ti-based metallic glass matrix composites in 3.5 wt.% NaCl solutions

NASA Astrophysics Data System (ADS)

Xu, K. K.; Lan, A. D.; Yang, H. J.; Han, P. D.; Qiao, J. W.

2017-11-01

The Ti62Zr12V13Cu4Be9, Ti58Zr16V10Cu4Be12, Ti46Zr20V12Cu5Be17, and Ti40Zr24V12Cu5Be19 metallic glass matrix composites (MGMCs) were prepared by copper mould casting. The corrosion resistance and the pitting susceptibility of Ti-based MGMCs were tested on their cross-sectional areas in 3.5 wt.% NaCl solutions by potentiodynamic polarization measurements. The composites with lower Ti contents (Ti40Zr24V12Cu5Be19 and Ti46Zr20V12Cu5Be17) exhibit a low resistance to the chloride induced pitting and local corrosion. The preferential dissolution of amorphous matrix is explained by the high chemical reactivity of beryllium element compared to that of stable dendrites and by the detected lower Ti and V contents. However, fairly good passivity was found in the composite with higher Ti contents (Ti62Zr12V13Cu4Be9). XPS measurements revealed that protective Ti-enriched oxide film was formed on the composite surface, additionally, lower content of beryllium element in amorphous matrix hinder the selective corrosion of amorphous matrix. The assessment of experimental observation leads to a proposed corrosion mechanism involving selective dissolution of amorphous matrix and chloride induced pitting process.

Analytical and numerical simulation of the steady-state hydrologic effects of mining aggregate in hypothetical sand-and-gravel and fractured crystalline-rock aquifers

USGS Publications Warehouse

Arnold, L.R.; Langer, William H.; Paschke, Suzanne Smith

2003-01-01

Analytical solutions and numerical models were used to predict the extent of steady-state drawdown caused by mining of aggregate below the water table in hypothetical sand-and-gravel and fractured crystalline-rock aquifers representative of hydrogeologic settings in the Front Range area of Colorado. Analytical solutions were used to predict the extent of drawdown under a wide range of hydrologic and mining conditions that assume aquifer homogeneity, isotropy, and infinite extent. Numerical ground-water flow models were used to estimate the extent of drawdown under conditions that consider heterogeneity, anisotropy, and hydrologic boundaries and to simulate complex or unusual conditions not readily simulated using analytical solutions. Analytical simulations indicated that the drawdown radius (or distance) of influence increased as horizontal hydraulic conductivity of the aquifer, mine penetration of the water table, and mine radius increased; radius of influence decreased as aquifer recharge increased. Sensitivity analysis of analytical simulations under intermediate conditions in sand-and-gravel and fractured crystalline-rock aquifers indicated that the drawdown radius of influence was most sensitive to mine penetration of the water table and least sensitive to mine radius. Radius of influence was equally sensitive to changes in horizontal hydraulic conductivity and recharge. Numerical simulations of pits in sand-and- gravel aquifers indicated that the area of influence in a vertically anisotropic sand-and-gravel aquifer of medium size was nearly identical to that in an isotropic aquifer of the same size. Simulated area of influence increased as aquifer size increased and aquifer boundaries were farther away from the pit, and simulated drawdown was greater near the pit when aquifer boundaries were close to the pit. Pits simulated as lined with slurry walls caused mounding to occur upgradient from the pits and drawdown to occur downgradient from the pits. Pits simulated as refilled with water and undergoing evaporative losses had little hydro- logic effect on the aquifer. Numerical sensitivity analyses for simulations of pits in sand-and-gravel aquifers indicated that simulated head was most sensitive to horizontal hydraulic conductivity and the hydraulic conductance of general-head boundaries in the models. Simulated head was less sensitive to riverbed conductance and recharge and relatively insensitive to vertical hydraulic conductivity. Numerical simulations of quarries in fractured crystalline-rock aquifers indicated that the area of influence in a horizontally anisotropic aquifer was elongated in the direction of higher horizontal hydraulic conductivity and shortened in the direction of lower horizontal hydraulic conductivity compared to area of influence in a homogeneous, isotropic aquifer. Area of influence was larger in an aquifer with ground-water flow in deep, low-permeability fractures than in a homogeneous, isotropic aquifer. Area of influence was larger for a quarry intersected by a hydraulically conductive fault zone and smaller for a quarry intersected by a low-conductivity fault zone. Numerical sensitivity analyses for simulations of quarries in fractured crystalline-rock aquifers indicated simulated head was most sensitive to variations in recharge and horizontal hydraulic conductivity, had little sensitivity to vertical hydraulic conductivity and drain cells used to simulate valleys, and was relatively insensitive to drain cells used to simulate the quarry.

Effect of chlorides on solution corrosivity of methyldiethanolamine (MDEA) solutions

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

Rooney, P.C.; Bacon, T.R.; DuPart, M.S.

1997-08-01

Solution corrosivity of MDEA/water solutions containing added HCl or NaCl have been measured by weight loss coupons at 250 F and by linear polarization resistance (LPR) at 208 F using carbon steel, 304SS, 316SS and 410SS. General corrosion as well as pitting or crevice corrosion tendencies were recorded for each species. Based on these results, recommendations are made for chlorides in MDEA that minimizes corrosion in gas treating operations.

Effect of Host Media on Microbial Influenced Corrosion due to Desulfotomaculum nigrificans

NASA Astrophysics Data System (ADS)

Lata, Suman; Sharma, Chhaya; Singh, Ajay K.

2013-04-01

This article reports about the tests carried to investigate microbial-induced corrosion on stainless steels due to sulfate-reducing bacteria sp. Desulfotomaculum nigrificans in different host media. Stainless steel 304L, 316L, and 2205 were selected for the test. Modified Baar's media (BM), sodium chloride solution, and artificial sea water (SW) were used as test solutions in anaerobic conditions. Electrochemical polarization and immersion test were performed to estimate the extent of corrosion rate and pitting on stainless steels. SEM/EDS were used to study the details inside/outside pits formed on the corroded samples. Biofilm formed on corroded coupons was analyzed for its components by UV/Visible spectroscopy. Corrosion attack on the test samples was observed maximum in case of exposure to SW followed by NaCl solution, both having sulfide and chloride whereas stainless steel exposed to BM, having sulfide, showed minimum attack. Tendency of extracellular polymeric substances to bind metal ions is observed to be responsible for governing the extent of corrosion attack.

Geochemical behavior and dissolved species control in acid sand pit lakes, Sepetiba sedimentary basin, Rio de Janeiro, SE - Brazil

NASA Astrophysics Data System (ADS)

Marques, Eduardo D.; Sella, Sílvia M.; Bidone, Edison D.; Silva-Filho, Emmanoel V.

2010-12-01

This work shows the influence of pluvial waters on dissolved components and mineral equilibrium of four sand pit lakes, located in the Sepetiba sedimentary basin, SE Brazil. The sand mining activities promote sediment oxidation, lowering pH and increasing SO 4 contents. The relatively high acidity of these waters, similar to ore pit lakes environment and associated acid mine drainage, increases weathering rate, especially of silicate minerals, which produces high Al concentrations, the limiting factor for fish aquaculture. During the dry season, basic cations (Ca, Mg, K and Na), SiO 2 and Al show their higher values due to evapoconcentration and pH are buffered. In the beginning of the wet season, the dilution factor by rainwater increases SO 4 and decreases pH values. The aluminum monomeric forms (Al(OH) 2+ and Al(OH) 2+), the most toxic species for aquatic organisms, occur during the dry season, while AlSO 4+ species predominate during the wet season. Gibbsite, allophane, alunite and jurbanite are the reactive mineral phases indicated by PHREEQC modeling. During the dry season, hydroxialuminosilicate allophane is the main phase in equilibrium with the solution, while the sulphate salts alunite and jurbanite predominate in the rainy season due to the increasing of SO 4 values. Gibbsite is also in equilibrium with sand pit lakes waters, pointing out that hydrolysis reaction is a constant process in the system. Comparing to SiO 2, sulphate is the main Al retriever in the pit waters because the most samples (alunite and jurbanite) are in equilibrium with the solution in both seasons. This Al hydrochemical control allied to some precaution, like pH correction and fertilization of these waters, allows the conditions for fishpond culture. Equilibrium of the majority samples with kaolinite (Ca, Mg, Na diagrams) and primary minerals (K diagram) points to moderate weathering rate in sand pit sediments, which cannot be considered for the whole basin due to the anomalous acidification of the studied waters.

A Review of Solution Chemistry Studies: Insights into Students' Conceptions

ERIC Educational Resources Information Center

Calyk, Muammer; Ayas, Alipa; Ebenezer, Jazlin V.

2005-01-01

This study has reviewed the last two decades of student conception research in solution chemistry pertaining to aims, methods of exploring students' conception, general knowledge claims, students' conceptions and difficulties, and conceptual change studies. The aims of solution chemistry studies have been to assess students' understanding level of…

Correlative Tomography

PubMed Central

Burnett, T. L.; McDonald, S. A.; Gholinia, A.; Geurts, R.; Janus, M.; Slater, T.; Haigh, S. J.; Ornek, C.; Almuaili, F.; Engelberg, D. L.; Thompson, G. E.; Withers, P. J.

2014-01-01

Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques. PMID:24736640

Pre-Service Chemistry Teachers' Competencies in the Laboratory: A Cross-Grade Study in Solution Preparation

ERIC Educational Resources Information Center

Karatas, F. O.

2016-01-01

One of the prerequisites for chemistry teacher candidates is to demonstrate certain laboratory skills. This article aims to determine and discuss the competencies of pre-service chemistry teachers in a chemistry laboratory context working with solution chemistry content. The participants in this study consisted of a group of pre-service chemistry…

Scanning electrochemical microscopy of precursor sites for pitting corrosion on titanium

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

Casillas, N.; Charlebois, S.J.; Smyrl, W.H.

1993-09-01

Scanning electrochemical microscopy, SECM, of oxide-covered titanium foils ([approximately]50 [angstrom] oxide thickness) immersed in potassium bromide solutions is reported. Electrogeneration of bromine (2 Br[sup [minus

High-temperature rapid pyrometamorphism induced by a charcoal pit burning: The case of Ricetto, central Italy

NASA Astrophysics Data System (ADS)

Capitanio, Flavio; Larocca, Francesco; Improta, Salvatore

Bulk chemistry and mineralogy of the peculiar rock of Ricetto (Carseolani Mts., Central Apennines, Italy) was studied to resolve its controversial origin: igneous dyke or anthropic product. This hybrid rock consists of a colorless, felsic component made up of glass plus quartz, and a brown, femic component made up of fans and spherulites of diopside, calcic plagioclase, wollastonite, and melilite. Textural relationships indicate very rapid cooling and immiscibility phenomena. The bulk chemistry of the rock is the same as that of the surrounding siliciclastic sandstone. The 14C analysis of a coal fragment from bottom of the body yields the conventional age of 227(+/-50) years. The Ricetto occurrence is an example of pyrometamorphism of a siliceous limestone induced by a charcoal pit burning. The small size of the heat source at Ricetto caused an intense but short-lived melting of the country rock. Prograde metamorphism caused a temperature increase up to 1,000-1,100 °C when melilite crystallization conditions were reached at appreciable P(CO2) and high f(O2). Melting occurred in a close system represented by the simplified equation: 3Cal+16.5Qtz+Ms+Bt-->Mel+Melt+2H2O+3CO2+0.5O2. Diopside+calcic plagioclase+wollastonite formed by melilite breakdown during rapid cooling, through the reaction: 6Mel+6Qtz+0.5O2-->3Di+2An+7Wo. Liquid immiscibility caused the separation between the felsic melt component and the femic melilite-bearing component. Immiscibility was characterized by different fractionation of alumina and alkalies between these two phases. Differences in bulk, glass, and mineral chemistry between the Ricetto and other melilite-bearing pyrometamorphic rocks can be attributed mainly to different protoliths.

Localized corrosion behaviour in simulated human body fluids of commercial Ni-Ti orthodontic wires.

PubMed

Rondelli, G; Vicentini, B

1999-04-01

The corrosion performances in simulated human body fluids of commercial equiatomic Ni-Ti orthodontic wires having various shape and size and produced by different manufacturers were evaluated; for comparison purposes wires made of stainless steel and of cobalt-based alloy were also examined. Potentiodynamic tests in artificial saliva at 40 degrees C indicated a sufficient pitting resistance for the Ni-Ti wires, similar to that of cobalt-based alloy wire; the stainless steel wire, instead, exhibited low pitting potential. Potentiodynamic tests at 40 degrees C in isotonic saline solution (0.9% NaCl) showed, for Ni-Ti and stainless steel wires, pitting potential values in the range approximately 200-400 mV and approximately 350 mV versus SCE, respectively: consequently, according to literature data (Hoar TP, Mears DC. Proc Roy Soc A 1996;294:486-510), these materials should be considered potentially susceptible to pitting; only the cobalt-based alloy should be immune from pitting. The localized corrosion potentials determined in the same environment by the ASTM F746 test (approximately 0-200 mV and 130 mV versus SCE for Ni-Ti and stainless steel, respectively) pointed out that for these materials an even higher risk of localized corrosion. Slight differences in localized corrosion behaviour among the various Ni-Ti wires were detected.

Uncertainties in detecting decadal change in extractable soil elements in Northern Forests

NASA Astrophysics Data System (ADS)

Bartlett, O.; Bailey, S. W.; Ducey, M. J.

2016-12-01

Northern Forest ecosystems have been or are being impacted by land use change, forest harvesting, acid deposition, atmospheric CO2 enrichment, and climate change. Each of these has the potential to modify soil forming processes, and the resulting chemical stocks. Horizontal and vertical variations in concentrations complicate determination of temporal change. This study evaluates sample design, sample size, and differences among observers as sources of uncertainty when quantifying soil temporal change over regional scales. Forty permanent, northern hardwood, monitoring plots were established on the White Mountain National Forest in central New Hampshire and western Maine. Soil pits were characterized and sampled by genetic horizon at plot center in 2001 and resampled again in 2014 two-meters on contour from the original sampling location. Each soil horizon was characterized by depth, color, texture, structure, consistency, boundaries, coarse fragments, and roots from the forest floor to the upper C horizon, the relatively unaltered glacial till parent material. Laboratory analyses included pH in 0.01 M CaCl2 solution and extractable Ca, Mg, Na, K, Al, Mn, and P in 1 M NH4OAc solution buffered at pH 4.8. Significant elemental differences were identified by genetic horizon from paired t-tests (p ≤ 0.05) indicate temporal change across the study region. Power analysis, 0.9 power (α = 0.05), revealed sampling size was appropriate within this region to detect concentration change by genetic horizon using a stratified sample design based on topographic metrics. There were no significant differences between observers' descriptions of physical properties. As physical properties would not be expected to change over a decade, this suggests spatial variation in physical properties between the pairs of sampling pits did not detract from our ability to detect temporal change. These results suggest that resampling efforts within a site, repeated across a region, to quantify elemental change by carefully described genetic horizons is an appropriate method of detecting soil temporal change in this region. Sample size and design considerations from this project will have direct implications for future monitoring programs to characterize change in soil chemistry.

Corrosion resistance of new beta type titanium alloy, Ti-29Nb-13Ta-4.6Zr in artificial saliva solution

NASA Astrophysics Data System (ADS)

Gunawarman; Giatmana, D. D.; Ilhamdi; Affi, J.; Fonna, S.; Niinomi, M.; Nakai, M.

2018-05-01

The corrosion resistance of Ti-29Nb-13Ta-4.6Zr (TNTZ) and Ti-6Al-4V alloys in oral cavity environment were studied by investigating its corrosion rate in artificial saliva solution. Corrosion measurement was conducted in 600 ml solution of Fusayama-Meyer artificial saliva containing 0.4g NaCl, 0.4g KCl, 0.795g CaCl2.2H2O, 0.69g NaH2PO4, and 1 g urea using a potentiostat controlled by a personal computer. The solution was maintained at pH 5.2 and controlled the temperature of 37°C to imitate oral cavity condition. After corrosion test, specimen surfaces were examined by SEM and EDX. The results show that the average corrosion rate of TNTZ and Ti-6Al-4V is 4,5×10-9 mmy-1 and 6,4×10-8 mmy-1, respectively, indicating that the corrosion resistance of TNTZ is slightly better than Ti-6Al-4V. This is suggested mainly due to the formation of multiple layers of Ti, Nb and Zr oxides in the surface of TNTZ. However, the formation of micro-pitting corrosion is more severe in TNTZ as compared to that of Ti-6Al-4V. The intense pitting corrosion in TNTZ is found strongly corresponded to its high impurities content and wide elemental segregation. It is recommended, therefore, a longer homogenizing process is required in TNTZ for reducing pitting corrosion attack. However, the details of corrosion mechanism are needed to be explored further.

Influence of Postbuild Microstructure on the Electrochemical Behavior of Additively Manufactured 17-4 PH Stainless Steel

NASA Astrophysics Data System (ADS)

Stoudt, M. R.; Ricker, R. E.; Lass, E. A.; Levine, L. E.

2017-03-01

The additive manufacturing build process produces a segregated microstructure with significant variations in composition and phases that are uncommon in traditional wrought materials. As such, the relationship between the postbuild microstructure and the corrosion resistance is not well understood. Stainless steel alloy 17-4 precipitation hardened (SS17-4PH) is an industrially relevant alloy for applications requiring high strength and good corrosion resistance. A series of potentiodynamic scans conducted in a deaerated 0.5-mol/L NaCl solution evaluated the influence of these microstructural differences on the pitting behavior of SS17-4. The pitting potentials were found to be higher in the samples of additively processed material than in the samples of the alloy in wrought form. This indicates that the additively processed material is more resistant to localized corrosion and pitting in this environment than is the wrought alloy. The results also suggest that after homogenization, the additively produced SS17-4 could be more resistant to pitting than the wrought SS17-4 is in an actual service environment.

The Influence of Post-Build Microstructure on the Electrochemical Behavior of Additively Manufactured 17-4 PH Stainless Steel.

PubMed

Stoudt, M R; Ricker, R E; Lass, E A; Levine, L E

2017-03-01

The additive manufacturing (AM) build process produces a segregated microstructure with significant variations in composition and phases that are uncommon in traditional wrought materials. As such, the relationship between the post-build microstructure and the corrosion resistance is not well understood. Stainless steel alloy 17-4PH is an industrially-relevant alloy for applications requiring high-strength and good corrosion resistance. A series of potentiodynamic scans conducted in a deaerated 0.5 mol/L NaCl solution evaluated the influence of these microstructural differences on the pitting behavior of SS17-4. The pitting potentials were found to be higher in the samples of additively-processed material than in samples of the alloy in wrought form. This indicates that the additively-processed material is more resistant to localized corrosion and pitting in this environment than the wrought alloy. The results also suggest that after homogenization, the additively-produced SS17-4 could be more resistant to pitting than wrought SS17-4 in an actual service environment.

The Influence of Post-Build Microstructure on the Electrochemical Behavior of Additively Manufactured 17-4 PH Stainless Steel

PubMed Central

Stoudt, M. R.; Ricker, R. E.; Lass, E. A.; Levine, L. E.

2017-01-01

The additive manufacturing (AM) build process produces a segregated microstructure with significant variations in composition and phases that are uncommon in traditional wrought materials. As such, the relationship between the post-build microstructure and the corrosion resistance is not well understood. Stainless steel alloy 17-4PH is an industrially-relevant alloy for applications requiring high-strength and good corrosion resistance. A series of potentiodynamic scans conducted in a deaerated 0.5 mol/L NaCl solution evaluated the influence of these microstructural differences on the pitting behavior of SS17-4. The pitting potentials were found to be higher in the samples of additively-processed material than in samples of the alloy in wrought form. This indicates that the additively-processed material is more resistant to localized corrosion and pitting in this environment than the wrought alloy. The results also suggest that after homogenization, the additively-produced SS17-4 could be more resistant to pitting than wrought SS17-4 in an actual service environment. PMID:28757787

Structure and mechanical and corrosion properties of new high-nitrogen Cr-Mn steels containing molybdenum

NASA Astrophysics Data System (ADS)

Berezovskaya, V. V.; Savrai, R. A.; Merkushkin, E. A.; Makarov, A. V.

2012-05-01

The structure, mechanical properties, and pitting corrosion of nickel-free high-nitrogen (0.8% N) austenitic 06Kh18AG19M2 and 07Kh16AG13M3 steels have been studied in various structural states obtained after hot deformation, quenching, and tempering at 300 and 500°C. Both steels are shown to be resistant to the γ → α and γ → ɛ martensite transformations irrespective of the decomposition of a γ solid solution (06Kh18AG19M2 steel). Austenite of the steel with 19 wt % Mn shows lower resistance to recrystallization, which provides its higher plasticity (δ5) and fracture toughness at a lower strength as compared to the steel with 13 wt % Mn. Electrochemical studies of the steels tempered at 300 and 500°C show that they are in a stable passive state during tests in a 3.5% NaCl solution and have high pitting resistance up to a potential E pf = 1.3-1.4 V, which is higher than that in 12Kh18N10T steel. In the quenched state, the passive state is instable but pitting formation potentials E pf retain their values. In all steels under study, pitting is shown to form predominantly along the grain boundaries of nonrecrystallized austenite. The lowest pitting resistance is demonstrated by the structure with a double grain boundary network that results from incomplete recrystallization at 1100°C and from the existence of initial and recrystallized austenite in the 07Kh16AG13M3 steel. To obtain a set of high mechanical and corrosion properties under given rolling conditions (1200-1150°C), annealing of the steels at temperatures no less than 1150°C (for 1 h) with water quenching and tempering at 500°C for 2 h are recommended.

Hydraulic performance improvement of the bidirectional pit pump installation based on CFD

NASA Astrophysics Data System (ADS)

Chen, H. X.; Zhou, D. Q.

2013-12-01

At present, the efficiency of bidirectional pit pump installation with lift under 2m is still low because of lack of research on it in the past. In the paper, the CFD numerical method and experimental test were applied to study flow characteristic of bidirectional pit pump installation under positive and reverse condition. Through changing airfoil type and position of blade and stay vane, the comprehensive performance of improved model were obtained by calculating many different models. The results showed that when improved model is obtained with type A runner with 4 blades that is 0.7D away from pit exit and unsymmetrical guide vane 0.25dh which away from the impeller outlet, and the flow pattern of the improved solution is steady with high efficiency. Compared with the original scheme, the efficiency of positive and reverse design condition reach to 67.23% and 58.32% respectively, which is increased 6% more than original model on the design condition and 5% on the optimum operating condition, and it achieved the purpose of improvement. According to the runner blade angle of the optimization solution, model synthetic characteristic curve was drawn and internal flow field characteristics was analyzed under optimal positive and reverse conditions. The numerical calculation shows that owing to the lack of stay vane to recycle the energy in outlet runner chamber, the water flow regime is not steady enough in the outlet passage, and that is the main reason for lower efficiency at reverse condition than that at positive condition.

In-situ Raman and X-ray photoelectron spectroscopic studies on the pitting corrosion of modified 9Cr-1Mo steel in neutral chloride solution

NASA Astrophysics Data System (ADS)

Ramya, S.; Nanda Gopala Krishna, D.; Mudali, U. Kamachi

2018-01-01

In-situ Raman and X-ray photoelectron spectroscopic studies were performed for the identification of native and corroded surface oxide layers of modified 9Cr-1Mo steel. The Raman data obtained for native oxide layer of modified 9Cr-1Mo steel revealed that it was mainly composed of oxides of Fe and Cr. The presence of alloying element Mo was found to be less significant in the native oxide film. The oxides of Cr were dominant at the surface and were found to be decreasing closer to metal/oxide layer interface. The changes in the chemical composition of the native films upon in-situ pitting during potentiostatic polarization experiment were characterized by in-situ Raman analysis. The corrosion products of potentiostatically polarized modified 9Cr-1Mo steel was composed of dominant Fe (III) phases viz., γ- Fe2O3, α and γ - FeOOH along with the oxides of chromium. The results from Raman analysis were corroborated with the XPS experiments on as received and pitted samples of modified 9Cr-1Mo steel specimens. It was observed that the oxides of Cr and Mo contributed for the stability of the surface layer by forming Cr2O3 and MoO3. Also, the study attempted to find out the intermediate corrosion products inside the metastable pits to account for the pseudo passive behavior of modified 9Cr-1Mo steel in 0.1 M NaCl solution.

Wind tunnel study of ammonia transfer from a manure pit fitted with a dairy cattle slatted floor.

PubMed

De Paepe, Merlijn; Pieters, Jan G; Mendes, Luciano B; Van Weyenberg, Stephanie; Merci, Bart; Demeyer, Peter

2016-01-01

In dairy cattle systems, most of the feces and urine go to the pit. At the manure pit level, mass transfer of NH3 ([Formula: see text]) has many factors, but practical difficulties hamper a controlled field evaluation. In this study, we propose a methodology for the determination of an alternative, more practical, pit transfer coefficient of NH3 (PTC), and compare it with [Formula: see text] determined from other scientific studies. The aims of this research study were: (1) to develop a wind tunnel set-up which mimics air flow patterns between the slats and above a clean section of a slatted floor section, featuring an aqueous NH3-emitting solution; and (2) to assess how air velocity, turbulence intensity, NH3 concentration ([NH3]) and PTC are influenced by inlet airflow ventilation rate (VR) forced deflection of the air above the slats into the manure pit through varying the deflection angle (DA) of a deflection panel and varying pit headspace height (HH). Main conclusions were: (1) the calculated PTC values presented a good fit to the power function of the air speed near the slats (u) (p < .001) while the average PTC (0.0039 m s(-1)) was comparable to [Formula: see text] values obtained from other studies, by remaining within the range of average values of 0.0015-0.0043 m s(-1); (2) VR and DA significantly impacted [NH3] profiles and PTC (p < .001) and (3) changing slurry pit from 0.10 to 0.90 m HH did not significantly impact [NH3] or PTC (p = .756 and p = .854, respectively).

Taguchi Optimization of Pulsed Current GTA Welding Parameters for Improved Corrosion Resistance of 5083 Aluminum Welds

NASA Astrophysics Data System (ADS)

Rastkerdar, E.; Shamanian, M.; Saatchi, A.

2013-04-01

In this study, the Taguchi method was used as a design of experiment (DOE) technique to optimize the pulsed current gas tungsten arc welding (GTAW) parameters for improved pitting corrosion resistance of AA5083-H18 aluminum alloy welds. A L9 (34) orthogonal array of the Taguchi design was used, which involves nine experiments for four parameters: peak current ( P), base current ( B), percent pulse-on time ( T), and pulse frequency ( F) with three levels was used. Pitting corrosion resistance in 3.5 wt.% NaCl solution was evaluated by anodic polarization tests at room temperature and calculating the width of the passive region (∆ E pit). Analysis of variance (ANOVA) was performed on the measured data and S/ N (signal to noise) ratios. The "bigger is better" was selected as the quality characteristic (QC). The optimum conditions were found as 170 A, 85 A, 40%, and 6 Hz for P, B, T, and F factors, respectively. The study showed that the percent pulse-on time has the highest influence on the pitting corrosion resistance (50.48%) followed by pulse frequency (28.62%), peak current (11.05%) and base current (9.86%). The range of optimum ∆ E pit at optimum conditions with a confidence level of 90% was predicted to be between 174.81 and 177.74 mVSCE. Under optimum conditions, the confirmation test was carried out, and the experimental value of ∆ E pit of 176 mVSCE was in agreement with the predicted value from the Taguchi model. In this regard, the model can be effectively used to predict the ∆ E pit of pulsed current gas tungsten arc welded joints.

A Cross-Age Study of Different Perspectives in Solution Chemistry from Junior to Senior High School

ERIC Educational Resources Information Center

Calik, Muammer

2005-01-01

This study reports on research examining what students think about aspects of solution chemistry and seeks to establish what alternative conceptions they hold in this area. To achieve this aim the researchers developed a test comprising of open-ended questions that evaluated students understanding of solution chemistry. The test was administered…

Catalysis and chemical mechanisms of calcite dissolution in seawater.

PubMed

Subhas, Adam V; Adkins, Jess F; Rollins, Nick E; Naviaux, John; Erez, Jonathan; Berelson, William M

2017-07-18

Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric [Formula: see text] on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms responsible for calcite dissolution in seawater. In this paper, we dissolve 13 C-labeled calcites in natural seawater. We show that the time-evolving enrichment of [Formula: see text] in solution is a direct measure of both dissolution and precipitation reactions across a large range of saturation states. Secondary Ion Mass Spectrometer profiles into the 13 C-labeled solids confirm the presence of precipitated material even in undersaturated conditions. The close balance of precipitation and dissolution near equilibrium can alter the chemical composition of calcite deeper than one monolayer into the crystal. This balance of dissolution-precipitation shifts significantly toward a dissolution-dominated mechanism below about [Formula: see text] Finally, we show that the enzyme carbonic anhydrase (CA) increases the dissolution rate across all saturation states, and the effect is most pronounced close to equilibrium. This finding suggests that the rate of hydration of [Formula: see text] is a rate-limiting step for calcite dissolution in seawater. We then interpret our dissolution data in a framework that incorporates both solution chemistry and geometric constraints on the calcite solid. Near equilibrium, this framework demonstrates a lowered free energy barrier at the solid-solution interface in the presence of CA. This framework also indicates a significant change in dissolution mechanism at [Formula: see text], which we interpret as the onset of homogeneous etch pit nucleation.

Catalysis and chemical mechanisms of calcite dissolution in seawater

PubMed Central

Adkins, Jess F.; Rollins, Nick E.; Naviaux, John; Erez, Jonathan; Berelson, William M.

2017-01-01

Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric CO2 on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms responsible for calcite dissolution in seawater. In this paper, we dissolve 13C-labeled calcites in natural seawater. We show that the time-evolving enrichment of 𝜹13C in solution is a direct measure of both dissolution and precipitation reactions across a large range of saturation states. Secondary Ion Mass Spectrometer profiles into the 13C-labeled solids confirm the presence of precipitated material even in undersaturated conditions. The close balance of precipitation and dissolution near equilibrium can alter the chemical composition of calcite deeper than one monolayer into the crystal. This balance of dissolution–precipitation shifts significantly toward a dissolution-dominated mechanism below about Ω= 0.7. Finally, we show that the enzyme carbonic anhydrase (CA) increases the dissolution rate across all saturation states, and the effect is most pronounced close to equilibrium. This finding suggests that the rate of hydration of CO2 is a rate-limiting step for calcite dissolution in seawater. We then interpret our dissolution data in a framework that incorporates both solution chemistry and geometric constraints on the calcite solid. Near equilibrium, this framework demonstrates a lowered free energy barrier at the solid–solution interface in the presence of CA. This framework also indicates a significant change in dissolution mechanism at Ω= 0.7, which we interpret as the onset of homogeneous etch pit nucleation. PMID:28720698

Effect of Mo contents on corrosion behaviors of welded duplex stainless steel

NASA Astrophysics Data System (ADS)

Bae, Seong Han; Lee, Hae Woo

2013-05-01

The corrosion behaviour and change of the phase fraction in welded 24Cr Duplex stainless steel was investigated for different chemical composition ranges of Mo contents. Filler metal was produced by fixing the contents of Cr, Ni, N, and Mn while adjusting the Mo content to 0.5, 1.4, 2.5, 3.5 wt%. The δ-ferrite fraction was observed to increase as the content of Mo increased. A polarisation test conducted in a salt solution, indicated the pitting corrosion potential increased continuously to 3.5 wt% Mo, while the corrosion potential changed most between 0.5 and 1.41 wt% Mo. The location of the pitting corrosion in 0.5 wt% Mo steel was randomly distributed, but it occurred selectively at the grain boundary between the γ- and δ-ferrite phases in 1.4, 2.5 and 3.5 wt% Mo steel. Energy dispersive X-ray spectroscopy mapping analysis showed that areas deficient in Cr, Mo, and Ni occurred around the grain boundary of the γ- and δ-ferrite phases. Non-metallic inclusions are thought to act as initiation points for the pitting corrosion that occurs in the salt solution initially as a result of the potential difference between the matrix structure and the incoherent inclusions.

Effect of Microstructure on Stress Corrosion Cracking Behaviour of High Nitrogen Stainless Steel Gas Tungsten Arc Welds

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Srinivasa Rao, K.; Madhusudhan Reddy, G.

2018-03-01

Present work is aimed to improve stress corrosion cracking resistance of high nitrogen steel and its welds. An attempt to weld high nitrogen steel of 5 mm thick plate using gas tungsten arc welding (GTAW) with three high strength age hardenable fillers i.e., 11-10 PH filler, PH 13- 8Mo and maraging grade of MDN 250 filler is made. Welds were characterized by optical microscopy and scanning electron microscopy. Vickers hardness testing of the welds was carried out to study the mechanical behaviour of welds. Potentio-dynamic polarization studies were done to determine pitting corrosion resistance in aerated 3.5% NaCl solution. Stress corrosion cracking (SCC) testing was carried out using constant load type machine with applied stress of 50% yield strength and in 45% MgCl2 solution boiling at 155°C. The results of the present investigation established that improvement in resistance to stress corrosion cracking was observed for PH 13- 8Mo GTA welds when compared to 11-10 PH and MDN 250 GTA welds. However, All GTA welds failed in the weld interface region. This may be attributed to relatively lower pitting potential in weld interface which acts as active site and the initiation source of pitting.

The stress-corrosion behavior of Al-Li-Cu alloys: A comparison of test methods

NASA Technical Reports Server (NTRS)

Rizzo, P. P.; Galvin, R. P.; Nelson, H. G.

1982-01-01

Two powder metallurgy processed (Al-Li-Cu) alloys with and without Mg addition were studied in aqueous 3.5% NaCl solution during the alternate immersion testing of tuning fork specimens, slow crack growth tests using fracture mechanics specimens, and the slow strain rate testing of straining electrode specimens. Scanning electron microscopy and optical metallography were used to demonstrate the character of the interaction between the Al-Li-Cu alloys and the selected environment. Both alloys are susceptible to SC in an aqueous 3.5% NaCl solution under the right electrochemical and microstructural conditions. Each test method yields important information on the character of the SC behavior. Under all conditions investigated, second phase particles strung out in rows along the extrusion direction in the alloys were rapidly attacked, and played principal role in the SC process. With time, larger pits developed from these rows of smaller pits and under certain electrochemical conditions surface cracks initiated from the larger pits and contributed directly to the fracture process. Evidence to support slow crack growth was observed in both the slow strain rate tests and the sustained immersion tests of precracked fracture mechanics specimens. The possible role of H2 in the stress corrosion cracking process is suggested.

Equipment Selection by using Fuzzy TOPSIS Method

NASA Astrophysics Data System (ADS)

Yavuz, Mahmut

2016-10-01

In this study, Fuzzy TOPSIS method was performed for the selection of open pit truck and the optimal solution of the problem was investigated. Data from Turkish Coal Enterprises was used in the application of the method. This paper explains the Fuzzy TOPSIS approaches with group decision-making application in an open pit coal mine in Turkey. An algorithm of the multi-person multi-criteria decision making with fuzzy set approach was applied an equipment selection problem. It was found that Fuzzy TOPSIS with a group decision making is a method that may help decision-makers in solving different decision-making problems in mining.

Geological and technological evaluation of gold-bearing mineral material after photo-electrochemical activation leaching

NASA Astrophysics Data System (ADS)

Manzyrev, DV

2017-02-01

The paper reports the lab test results on simulation of heap leaching of unoxidized rebellious ore extracted from deep levels of Pogromnoe open pit mine, with different flowsheets and photo-electrochemically activated solutions. It has been found that pre-treatment of rebellious ore particles -10 mm in size by photo-electrochemically activated solutions at the stage preceding agglomeration with the use of rich cyanide solutions enhances gold recovery by 6%.

Pitting and stress corrosion cracking of stainless steel

NASA Astrophysics Data System (ADS)

Saithala, Janardhan R.

An investigation has been performed to determine the pitting resistance of stainless steels and stress corrosion cracking of super duplex stainless steels in water containing chloride ions from 25 - 170°C. The steels studied are 12% Cr, FV520B, FV566, 304L, Uranus65, 2205, Ferallium Alloy 255, and Zeron 100. All these commercial materials used in very significant industrial applications and suffer from pitting and stress corrosion failures. The design of a new experimental setup using an autoclave enabled potentiodynamic polarisation experiments and slow strain rate tests in dilute environments to be conducted at elevated temperatures. The corrosion potentials were controlled using a three electrode cell with computer controlled potentiostat.The experimental programme to determine pitting potentials was designed to simulate the service conditions experienced in most industrial plants and develop mathematical model equations to help a design engineer in material selection decision. Stress corrosion resistance of recently developed Zeron100 was evaluated in dilute environments to propose a mechanism in chloride solutions at high' temperatures useful for the nuclear and power generation industry. Results have shown the significance of the composition of alloying elements across a wide range of stainless steels and its influence on pitting. Nitrogen and molybdenum added to modern duplex stainless steels was found to be unstable at higher temperatures. The fractographic results obtained using the scanning electron microscope (SEM) has given insight in the initiation of pitting in modem duplex and super duplex stainless steels. A mathematical model has been proposed to predict pitting in stainless steels based on the effect of environmental factors (temperature, chloride concentration, and chemical composition). An attempt has been made to identify the mechanism of SCC in Zeron100 super duplex stainless steel.The proposed empirical models have shown good correlation between predicted pitting potential values with experimental results. It has been shown that the SCC mechanism in Zeron100 supports the slip assisted anodic dissolution model of SCC. The relationship between pitting and stress corrosion in dilute environments is established and empirical equations have been proposed to determine the damage region for wide range of stainless steels.

Activation of aluminum as an effective reducing agent by pitting corrosion for wet-chemical synthesis.

PubMed

Li, Wei; Cochell, Thomas; Manthiram, Arumugam

2013-01-01

Metallic aluminum (Al) is of interest as a reducing agent because of its low standard reduction potential. However, its surface is invariably covered with a dense aluminum oxide film, which prevents its effective use as a reducing agent in wet-chemical synthesis. Pitting corrosion, known as an undesired reaction destroying Al and is enhanced by anions such as F⁻, Cl⁻, and Br⁻ in aqueous solutions, is applied here for the first time to activate Al as a reducing agent for wet-chemical synthesis of a diverse array of metals and alloys. Specifically, we demonstrate the synthesis of highly dispersed palladium nanoparticles on carbon black with stabilizers and the intermetallic Cu₂Sb/C, which are promising candidates, respectively, for fuel cell catalysts and lithium-ion battery anodes. Atomic hydrogen, an intermediate during the pitting corrosion of Al in protonic solvents (e.g., water and ethylene glycol), is validated as the actual reducing agent.

Method of forming grooves in the [011] crystalline direction

NASA Technical Reports Server (NTRS)

Marinelli, Donald Paul (Inventor)

1977-01-01

An A-B etchant is applied to a (100) surface of a body of semiconductor material, a portion of which along the (100) surface of the body is either gallium arsenide or gallium aluminum arsenide. The etchant is applied for at least 15 seconds at a temperature of approximately 80.degree. C. The A-B etchant is a solution by weight percent of 47.5%, water, 0.2% silver nitrate, 23.8% chromium trioxide and 28.5% of a 48% aqueous solution of hydrofluoric acid. As a result of the application of the A-B etchant a pattern of elongated etch pits form having their longitudinal axes along the [011] crystalline direction. Grooves are formed in the body at a surface opposite the (100) surface on which was applied the etchant. The grooves are formed along the [011] crystalline direction by aligning the longitudinal axes of the grooves with the longitudinal axes of the etch pits.

Toxicity Evaluation of Engineered Nanomaterials (Phase 1 Studies)

DTIC Science & Technology

2012-01-01

Surface Chemistry on Cellular Response ...................................................................................................... 48...Gold Nanomaterial Solution Purity and Surface Chemistry Toxicity ................................................................. 18 Figure 7...Solution Purity and Surface Chemistry Control Although several studies have shown that both MPS and PEG are biocompatible, in order to ensure that

Metagenomic investigation of the microbial diversity in a chrysotile asbestos mine pit pond, Lowell, Vermont, USA.

PubMed

Driscoll, Heather E; Vincent, James J; English, Erika L; Dolci, Elizabeth D

2016-12-01

Here we report on a metagenomics investigation of the microbial diversity in a serpentine-hosted aquatic habitat created by chrysotile asbestos mining activity at the Vermont Asbestos Group (VAG) Mine in northern Vermont, USA. The now-abandoned VAG Mine on Belvidere Mountain in the towns of Eden and Lowell includes three open-pit quarries, a flooded pit, mill buildings, roads, and > 26 million metric tons of eroding mine waste that contribute alkaline mine drainage to the surrounding watershed. Metagenomes and water chemistry originated from aquatic samples taken at three depths (0.5 m, 3.5 m, and 25 m) along the water column at three distinct, offshore sites within the mine's flooded pit (near 44°46'00.7673″, - 72°31'36.2699″; UTM NAD 83 Zone 18 T 0695720 E, 4960030 N). Whole metagenome shotgun Illumina paired-end sequences were quality trimmed and analyzed based on a translated nucleotide search of NCBI-NR protein database and lowest common ancestor taxonomic assignments. Our results show strata within the pit pond water column can be distinguished by taxonomic composition and distribution, pH, temperature, conductivity, light intensity, and concentrations of dissolved oxygen. At the phylum level, metagenomes from 0.5 m and 3.5 m contained a similar distribution of taxa and were dominated by Actinobacteria (46% and 53% of reads, respectively), Proteobacteria (45% and 38%, respectively), and Bacteroidetes (7% in both). The metagenomes from 25 m showed a greater diversity of phyla and a different distribution of reads than the two upper strata: Proteobacteria (60%), Actinobacteria (18%), Planctomycetes, (10%), Bacteroidetes (5%) and Cyanobacteria (2.5%), Armatimonadetes (< 1%), Verrucomicrobia (< 1%), Firmicutes (< 1%), and Nitrospirae (< 1%). Raw metagenome sequence data from each sample reside in NCBI's Short Read Archive (SRA ID: SRP056095) and are accessible through NCBI BioProject PRJNA277916.

In vitro corrosion resistance of Lotus-type porous Ni-free stainless steels.

PubMed

Alvarez, Kelly; Hyun, Soong-Keun; Fujimoto, Shinji; Nakajima, Hideo

2008-11-01

The corrosion behavior of three kinds of austenitic high nitrogen Lotus-type porous Ni-free stainless steels was examined in acellular simulated body fluid solutions and compared with type AISI 316L stainless steel. The corrosion resistance was evaluated by electrochemical techniques, the analysis of released metal ions was performed by inductively coupled plasma mass spectrometry (ICP-MS) and the cytotoxicity was investigated in a culture of murine osteoblasts cells. Total immunity to localized corrosion in simulated body fluid (SBF) solutions was exhibited by Lotus-type porous Ni-free stainless steels, while Lotus-type porous AISI 316L showed very low pitting corrosion resistance evidenced by pitting corrosion at a very low breakdown potential. Additionally, Lotus-type porous Ni-free stainless steels showed a quite low metal ion release in SBF solutions. Furthermore, cell culture studies showed that the fabricated materials were non-cytotoxic to mouse osteoblasts cell line. On the basis of these results, it can be concluded that the investigated alloys are biocompatible and corrosion resistant and a promising material for biomedical applications.

Electrochemical Corrosion of Stainless Steel in Thiosulfate Solutions Relevant to Gold Leaching

NASA Astrophysics Data System (ADS)

Choudhary, Lokesh; Wang, Wei; Alfantazi, Akram

2016-01-01

This study aims to characterize the electrochemical corrosion behavior of stainless steel in the ammoniacal thiosulfate gold leaching solutions. Electrochemical corrosion response was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy, while the semi-conductive properties and the chemical composition of the surface film were characterized using Mott-Schottky analysis and X-ray photoelectron spectroscopy, respectively. The morphology of the corroded specimens was analyzed using scanning electron microscopy. The stainless steel 316L showed no signs of pitting in the ammoniacal thiosulfate solutions.

An Investigation of Effectiveness of Conceptual Change Text-oriented Instruction on Students' Understanding of Solution Concepts

NASA Astrophysics Data System (ADS)

Pinarbaşi; , Tacettin; Canpolat, Nurtaç; Bayrakçeken, Samih; Geban, Ömer

2006-12-01

This study investigated the effect of conceptual change text-oriented instruction over traditional instruction on students' understanding of solution concepts (e.g., dissolving, solubility, factors affecting solubility, concentrations of solutions, types of solutions, physical properties of solutions) and their attitudes towards chemistry. The sample of this study consisted of 87 undergraduate students from two classes enrolled in an introductory chemistry course. One of the classes was assigned randomly to the control group, and the other class were assigned randomly to the experimental group. During teaching the topic of solution concepts in the chemistry curriculum, a conceptual change text-oriented instruction was applied in the experimental group whereas traditional instruction was followed in the control group. The results showed that the students in the experimental group performed better with respect to solution concepts. In addition, it has been found that there was no significant difference between the attitudes of students in the experimental and control groups towards chemistry.

A novel multidimensional protein identification technology approach combining protein size exclusion prefractionation, peptide zwitterion-ion hydrophilic interaction chromatography, and nano-ultraperformance RP chromatography/nESI-MS2 for the in-depth analysis of the serum proteome and phosphoproteome: application to clinical sera derived from humans with benign prostate hyperplasia.

PubMed

Garbis, Spiros D; Roumeliotis, Theodoros I; Tyritzis, Stavros I; Zorpas, Kostas M; Pavlakis, Kitty; Constantinides, Constantinos A

2011-02-01

The current proof-of-principle study was aimed toward development of a novel multidimensional protein identification technology (MudPIT) approach for the in-depth proteome analysis of human serum derived from patients with benign prostate hyperplasia (BPH) using rational chromatographic design principles. This study constituted an extension of our published work relating to the identification and relative quantification of potential clinical biomarkers in BPH and prostate cancer (PCa) tissue specimens. The proposed MudPIT approach encompassed the use of three distinct yet complementary liquid chromatographic chemistries. High-pressure size-exclusion chromatography (SEC) was used for the prefractionation of serum proteins followed by their dialysis exchange and solution phase trypsin proteolysis. The tryptic peptides were then subjected to offline zwitterion-ion hydrophilic interaction chromatography (ZIC-HILIC) fractionation followed by their online analysis with reversed-phase nano-ultraperformance chromatography (RP-nUPLC) hyphenated to nanoelectrospray ionization-tandem mass spectrometry using an ion trap mass analyzer. For the spectral processing, the sequential use of the SpectrumMill, Scaffold, and InsPecT software tools was applied for the tryptic peptide product ion MS(2) spectral processing, false discovery rate (FDR) assessment, validation, and protein identification. This milestone serum analysis study allowed the confident identification of over 1955 proteins (p ≤ 0.05; FDR ≤ 5%) with a broad spectrum of biological and physicochemical properties including secreted, tissue-specific proteins spanning approximately 12 orders of magnitude as they occur in their native abundance levels in the serum matrix. Also encompassed in this proteome was the confident identification of 375 phosphoproteins (p ≤ 0.05; FDR ≤ 5%) with potential importance to cancer biology. To demonstrate the performance characteristics of this novel MudPIT approach, a comparison was made with the proteomes resulting from the immunodepletion of the high abundant albumin and IgG proteins with offline first dimensional tryptic peptide separation with both ZIC-HILIC and strong cation exchange (SCX) chromatography and their subsequent online RP-nUPLC-nESI-MS(2) analysis.

Monitoring of adult Lost River and shortnose suckers in Clear Lake Reservoir, California, 2008–2010

USGS Publications Warehouse

Hewitt, David A.; Hayes, Brian S.

2013-01-01

Problems with inferring status and population dynamics from size composition data can be overcome by a robust capture-recapture program that follows the histories of PIT-tagged individuals. Inferences from such a program are currently hindered by poor detection rates during spawning seasons with low flows in Willow Creek, which indicate that a key assumption of capture-recapture models is violated. We suggest that the most straightforward solution to this issue would be to collect detection data during the spawning season using remote PIT tag antennas in the strait between the west and east lobes of the lake.

Bioremediation of Acidic and Metalliferous Drainage (AMD) through organic carbon amendment by municipal sewage and green waste.

PubMed

McCullough, Clint D; Lund, Mark A

2011-10-01

Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource in hot arid regions. However, pit lake water is often characterised by low pH with high dissolved metal concentrations resulting from Acidic and Metalliferous Drainage (AMD). Addition of organic matter to pit lakes to enhance microbial sulphate reduction is a potential cost effective remediation strategy. However, cost and availability of suitable organic substrates are often limiting. Nevertheless, large quantities of sewage and green waste (organic garden waste) are often available at mine sites from nearby service towns. We treated AMD pit lake water (pH 2.4) from tropical, North Queensland, Australia, with primary-treated sewage sludge, green waste, and a mixture of sewage and green waste (1:1) in a controlled microcosm experiment (4.5 L). Treatments were assessed at two different rates of organic loading of 16:1 and 32:1 pit water:organic matter by mass. Combined green waste and sewage treatment was the optimal treatment with water pH increased to 5.5 in only 145 days with decreases of dissolved metal concentrations. Results indicated that green waste was a key component in the pH increase and concomitant heavy metal removal. Water quality remediation was primarily due to microbially-mediated sulphate reduction. The net result of this process was removal of sulphate and metal solutes to sediment mainly as monosulfides. During the treatment process NH(3) and H(2)S gases were produced, albeit at below concentrations of concern. Total coliforms were abundant in all green waste-treatments, however, faecal coliforms were absent from all treatments. This study demonstrates addition of low-grade organic materials has promise for bioremediation of acidic waters and warrants further experimental investigation into feasibility at higher scales of application such as pit lakes. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Influence of microstructure and elemental partitioning on pitting corrosion resistance of duplex stainless steel welding joints

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Zhao, Lei; Zhang, Jianli

2017-02-01

The influences of microstructure and elemental partitioning on pitting corrosion resistance of duplex stainless steel joints welded by gas tungsten arc welding (GTAW) and flux-cored arc welding (FCAW) with different shielding gas compositions were studied by optical microscopy, electron backscatter diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, electron probe microanalysis, and potentiostatic and potentiodynamic polarization methods The adding 2% N2 in shielding gas facilitated primary austenite formation in GTAW weld metal (WM) and suppressed Cr2N precipitation in GTAW weld root. In the HAZ, the banded microstructure disappeared while the coarse ferrite grains maintained same orientation as the banded ferrite in the BM. In the WM, the ferrite had one single orientation throughout a grain, whereas several families of austenite appeared. The austenite both in BM and WM enriched in Ni and nitro`gen, while Cr and Mo were concentrated in the ferrite and thus no element showed clear dendritic distribution in the WM (ER2209 and E2209T1). In addition, the secondary austenite had higher Ni content but lower Cr and Mo content than the primary austenite. The N2-supplemented shielding gas promoted nitrogen solid-solution in the primary and secondary austenite. Furthermore, the secondary austenite had relatively lower pitting resistance equivalent number (PREN) than the ferrite and primary austenite, thereby resulting in its preferential corrosion. The Cr2N precipitation led to relatively poor resistance to pitting corrosion in three HAZs and pure Ar shielding GTAW weld root. The N2-supplemented shielding gas improved pitting corrosion resistance of GTAW joint by increasing PREN of secondary austenite and suppressing Cr2N precipitation. In addition, the FCAW WM had much poorer resistance to pitting corrosion than the GTAW WM due to many O-Ti-Si-Mn inclusions. In the BM, since the austenite with lower PREN compared to the ferrite, the pitting corrosion occurred at the ferrite and austenite interface or within the austenite.

Workflow Enhancement (WE) Improves Safety in Radiation Oncology: Putting the WE and Team Together

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

Chao, Samuel T., E-mail: chaos@ccf.org; Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center, Cleveland Clinic, Cleveland, Ohio; Meier, Tim

Purpose: To review the impact of a workflow enhancement (WE) team in reducing treatment errors that reach patients within radiation oncology. Methods and Materials: It was determined that flaws in our workflow and processes resulted in errors reaching the patient. The process improvement team (PIT) was developed in 2010 to reduce errors and was later modified in 2012 into the current WE team. Workflow issues and solutions were discussed in PIT and WE team meetings. Due to tensions within PIT that resulted in employee dissatisfaction, there was a 6-month hiatus between the end of PIT and initiation of the renamed/redesigned WEmore » team. In addition to the PIT/WE team forms, the department had separate incident forms to document treatment errors reaching the patient. These incident forms are rapidly reviewed and monitored by our departmental and institutional quality and safety groups, reflecting how seriously these forms are treated. The number of these incident forms was compared before and after instituting the WE team. Results: When PIT was disbanded, a number of errors seemed to occur in succession, requiring reinstitution and redesign of this team, rebranded the WE team. Interestingly, the number of incident forms per patient visits did not change when comparing 6 months during the PIT, 6 months during the hiatus, and the first 6 months after instituting the WE team (P=.85). However, 6 to 12 months after instituting the WE team, the number of incident forms per patient visits decreased (P=.028). After the WE team, employee satisfaction and commitment to quality increased as demonstrated by Gallup surveys, suggesting a correlation to the WE team. Conclusions: A team focused on addressing workflow and improving processes can reduce the number of errors reaching the patient. Time is necessary before a reduction in errors reaching patients will be seen.« less

Solving Solutions: Exploring Unknowns through Chemistry.

ERIC Educational Resources Information Center

Burns, John; Yoshina, Granville; Goodding, Debbie; Streitberger, Eric

2000-01-01

Presents a chemistry activity that introduces students to one type of chemical bond by developing the integer operation concept of zero pairs. Leads to an activity of combining drops of 0.3 molar solutions to form six different colored precipitates from five solutions. (ASK)

Stress Corrosion Cracking of an Austenitic Stainless Steel in Nitrite-Containing Chloride Solutions

PubMed Central

Singh Raman, R. K.; Siew, Wai Hoong

2014-01-01

This article describes the susceptibility of 316L stainless steel to stress corrosion cracking (SCC) in a nitrite-containing chloride solution. Slow strain rate testing (SSRT) in 30 wt. % MgCl2 solution established SCC susceptibility, as evidenced by post-SSRT fractography. Addition of nitrite to the chloride solution, which is reported to have inhibitive influence on corrosion of stainless steels, was found to increase SCC susceptibility. The susceptibility was also found to increase with nitrite concentration. This behaviour is explained on the basis of the passivation and pitting characteristics of 316L steel in chloride solution. PMID:28788276

ChIP-PIT: Enhancing the Analysis of ChIP-Seq Data Using Convex-Relaxed Pair-Wise Interaction Tensor Decomposition.

PubMed

Zhu, Lin; Guo, Wei-Li; Deng, Su-Ping; Huang, De-Shuang

2016-01-01

In recent years, thanks to the efforts of individual scientists and research consortiums, a huge amount of chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) experimental data have been accumulated. Instead of investigating them independently, several recent studies have convincingly demonstrated that a wealth of scientific insights can be gained by integrative analysis of these ChIP-seq data. However, when used for the purpose of integrative analysis, a serious drawback of current ChIP-seq technique is that it is still expensive and time-consuming to generate ChIP-seq datasets of high standard. Most researchers are therefore unable to obtain complete ChIP-seq data for several TFs in a wide variety of cell lines, which considerably limits the understanding of transcriptional regulation pattern. In this paper, we propose a novel method called ChIP-PIT to overcome the aforementioned limitation. In ChIP-PIT, ChIP-seq data corresponding to a diverse collection of cell types, TFs and genes are fused together using the three-mode pair-wise interaction tensor (PIT) model, and the prediction of unperformed ChIP-seq experimental results is formulated as a tensor completion problem. Computationally, we propose efficient first-order method based on extensions of coordinate descent method to learn the optimal solution of ChIP-PIT, which makes it particularly suitable for the analysis of massive scale ChIP-seq data. Experimental evaluation the ENCODE data illustrate the usefulness of the proposed model.

Comparative Studies on Microstructure, Mechanical and Pitting Corrosion of Post Weld Heat Treated IN718 Superalloy GTA and EB Welds

NASA Astrophysics Data System (ADS)

Dilkush; Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

In the present study, an attempt has been made to weld Inconel 718 nickel-base superalloy (IN718 alloy) using gas tungsten arc welding (GTAW) and electron beam welding (EBW) processes. Both the weldments were subjected to post-weld heat treatment condition as follows -980°C / 20 min followed by direct aging condition (DA) as 720°C/8 h/FC followed by 620°C/8 h/AC. The GTA and EB welds of IN718 alloy were compared in two conditions as-received and 980STA conditions. Welds were characterized to observe mechanical properties, pitting corrosion resistance by correlating with observed microstructures. The rate of higher cooling ranges, the fusion zone of EBW exhibited discrete and relative finer lave phases whereas the higher niobium existed laves with coarser structure were observed in GTAW. The significant dissolution of laves were observed at 980STA of EBW. Due to these effects, the EBW of IN718 alloy showed the higher mechanical properties than GTAW. The electrochemical potentiostatic etch test was carried out in 3.5wt% sodium chloride (NaCl) solution to study the pitting corrosion behaviour of the welds. Results of the present investigation established that mechanical properties and pitting corrosion behaviour are significantly better in post weld heat treated condition. The comparative studies showed that the better combination of mechanical properties and pitting corrosion resistance were obtained in 980STA condition of EBW than GTAW.

Non-uniform solute segregation at semi-coherent metal/oxide interfaces

DOE PAGES

Choudhury, Samrat; Aguiar, Jeffery A.; Fluss, Michael J.; ...

2015-08-26

The properties and performance of metal/oxide nanocomposites are governed by the structure and chemistry of the metal/oxide interfaces. Here we report an integrated theoretical and experimental study examining the role of interfacial structure, particularly misfit dislocations, on solute segregation at a metal/oxide interface. We find that the local oxygen environment, which varies significantly between the misfit dislocations and the coherent terraces, dictates the segregation tendency of solutes to the interface. Depending on the nature of the solute and local oxygen content, segregation to misfit dislocations can change from attraction to repulsion, revealing the complex interplay between chemistry and structure atmore » metal/oxide interfaces. These findings indicate that the solute chemistry at misfit dislocations is controlled by the dislocation density and oxygen content. As a result, fundamental thermodynamic concepts – the Hume-Rothery rules and the Ellingham diagram – qualitatively predict the segregation behavior of solutes to such interfaces, providing design rules for novel interfacial chemistries.« less

Cracking characteristics of alloy 690 in thiosulfate containing chloride solution

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

Huang, H.H.; Tsai, W.T.

1999-07-01

The cracking characteristics of Alloy 690 in deaerated 1wt% NaCl solution with different Na{sub 2}S{sub 2}O{sub 2} concentrations, namely 0.01, 0.1, 0.2 and 0.5 M, at controlled anodic potentials was investigated by using slow strain rate testing (SSRT) with a strain rate of 1 x 10{sup {minus}6} s{sup {minus}1}. The results showed that the ultimate tensile strength and the ductility increased with increasing the concentration of Na{sub 2}S{sub 2}O{sub 3} at the same anodic potential, but decreased with increasing potential at a fixed concentration of Na{sub 2}S{sub 2}O{sub 3}. Pitting corrosion could occur on Alloy 690 in 1wt% NaCl solutionmore » with the concentration of Na{sub 2}S{sub 2}O{sub 3} {le} 0.1 M, depending on the potential. The susceptibilities of Alloy 690 to pitting corrosion and environmentally-assisted cracking in 1wt% NaCl solution were inhibited with the concentration of Na{sub 2}S{sub 2}O{sub 3} {ge} 0.2M, regardless of the potential.« less

Superfund Record of Decision (EPA Region 6): Cimarron Mining Corporation site, Operable Unit 1, Lincoln County, Carrizozo, NM. (First remedial action), September 1990

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

Not Available

1990-09-21

The 10.6-acre Cimarron Mining site, Lincoln County, New Mexico, is an inactive milling facility used to recover iron from ores transported to the site. A shallow aquifer, which is not a potential drinking water source, and a deeper primary drinking water aquifer lie beneath the site. Cyanide was used until 1982 to recover precious metals. The operation of the mill resulted in the discharge of contaminated liquids onsite. The sources of environmental cyanide contamination at the site are the processed waste materials, including tailings piles and cinder block trench sediment piles, the cyanide solution and tailings spillage areas, and themore » cyanide solution recycling and disposal areas, including cinder block trenches and an unlined discharge pit. The major sources of ground water contamination by cyanide are the cinder block trenches and the discharge pit. These areas of prolonged contact between cyanide solution and underlying soil led to cyanide contamination in the shallow aquifer. The ROD addresses contaminated shallow ground water at the Cimarron Mining mill area as Operable Unit 1 (OU1). The primary contaminants of concern affecting the ground water are inorganics including cyanide.« less

Electrochemical study of Type 304 and 316L stainless steels in simulated body fluids and cell cultures.

PubMed

Tang, Yee-Chin; Katsuma, Shoji; Fujimoto, Shinji; Hiromoto, Sachiko

2006-11-01

The electrochemical corrosion behaviour of Type 304 and 316L stainless steels was studied in Hanks' solution, Eagle's minimum essential medium (MEM), serum containing medium (MEM with 10% of fetal bovine serum) without cells, and serum containing medium with cells over a 1-week period. Polarization resistance measurements indicated that the stainless steels were resistant to Hanks' and MEM solutions. Type 304 was more susceptible to pitting corrosion than Type 316L in Hanks' and MEM solutions. The uniform corrosion resistance of stainless steels, determined by R(p), was lower in culturing medium than in Hanks' and MEM. The low corrosion resistance was due to surface passive film with less protective to reveal high anodic dissolution rate. When cells were present, the initial corrosion resistance was low, but gradually increased after 3 days, consistent with the trend of cell coverage. The presence of cells was found to suppress the cathodic reaction, that is, oxygen reduction, and increase the uniform corrosion resistance as a consequence. On the other hand, both Type 304 and 316L stainless steels became more susceptible to pitting corrosion when they were covered with cells.

Innovative technologies on fuel assemblies cleaning for sodium fast reactors: First considerations on cleaning process

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

Simon, N.; Lorcet, H.; Beauchamp, F.

2012-07-01

Within the framework of Sodium Fast Reactor development, innovative fuel assembly cleaning operations are investigated to meet the GEN IV goals of safety and of process development. One of the challenges is to mitigate the Sodium Water Reaction currently used in these processes. The potential applications of aqueous solutions of mineral salts (including the possibility of using redox chemical reactions) to mitigate the Sodium Water Reaction are considered in a first part and a new experimental bench, dedicated to this study, is described. Anhydrous alternative options based on Na/CO{sub 2} interaction are also presented. Then, in a second part, amore » functional study conducted on the cleaning pit is proposed. Based on experimental feedback, some calculations are carried out to estimate the sodium inventory on the fuel elements, and physical methods like hot inert gas sweeping to reduce this inventory are also presented. Finally, the implementation of these innovative solutions in cleaning pits is studied in regard to the expected performances. (authors)« less

Testing and modeling the influence of reclamation and control methods for reducing nonpoint mercury emissions associated with industrial open pit gold mines.

PubMed

Miller, Matthieu B; Gustin, Mae S

2013-06-01

Industrial gold mining is a significant source of mercury (Hg) emission to the atmosphere. To investigate ways to reduce these emissions, reclamation and dust and mercury control methods used at open pit gold mining operations in Nevada were studied in a laboratory setting. Using this information along with field data, and building off previous work, total annual Hg emissions were estimated for two active gold mines in northern Nevada. Results showed that capping mining waste materials with a low-Hg substrate can reduce Hg emissions from 50 to nearly 100%. The spraying of typical dust control solutions often results in higher Hg emissions, especially as materials dry after application. The concentrated application of a dithiocarbamate Hg control reagent appears to reduce Hg emissions, but further testing mimicking the actual distribution of this chemical within an active leach solution is needed to make a more definitive assessment.

Visualization of Problem Solving Related to the Quantitative Composition of Solutions in the Dynamic "GeoGebra" Environment

ERIC Educational Resources Information Center

Kostic, V. Dj.; Jovanovic, V. P. Stankov; Sekulic, T. M.; Takaci, Dj. B.

2016-01-01

Problem solving in the field of quantitative composition of solutions (QCS), expressed as mass share and molar concentration, is essential for chemistry students. Since successful chemistry education is based on different mathematical contents, it is important to be proficient in both mathematical and chemistry concepts as well as interconnections…

Chemical passivation as a method of improving the electrochemical corrosion resistance of Co-Cr-based dental alloy.

PubMed

Rylska, Dorota; Sokołowski, Grzegorz; Sokołowski, Jerzy; Łukomska-Szymańska, Monika

2017-01-01

The purpose of the study was to evaluate corrosion resistance of Wirobond C® alloy after chemical passivation treatment. The alloy surface undergone chemical passivation treatment in four different media. Corrosion studies were carried out by means of electrochemical methods in saline solution. Corrosion effects were determined using SEM. The greatest increase in the alloy polarization resistance was observed for passive layer produced in Na2SO4 solution with graphite. The same layer caused the highest increase in corrosion current. Generally speaking, the alloy passivation in Na2SO4 solution with graphite caused a substantial improvement of the corrosion resistance. The sample after passivation in Na2SO4 solution without graphite, contrary to others, lost its protective properties along with successive anodic polarization cycles. The alloy passivation in Na3PO4 solution with graphite was the only one that caused a decrease in the alloy corrosion properties. The SEM studies of all samples after chemical passivation revealed no pit corrosion - in contrast to the sample without any modification. Every successive polarization cycle in anodic direction of pure Wirobond C® alloy enhances corrosion resistance shifting corrosion potential in the positive direction and decreasing corrosion current value. The chemical passivation in solutions with low pH values decreases susceptibility to electrochemical corrosion of Co-Cr dental alloy. The best protection against corrosion was obtained after chemical passivation of Wirobond C® in Na2SO4 solution with graphite. Passivation with Na2SO4 in solution of high pH does not cause an increase in corrosion resistance of WIROBOND C. Passivation process increases alloy resistance to pit corrosion.

Influence of nitrogen in the shielding gas on corrosion resistance of duplex stainless steel welds

NASA Astrophysics Data System (ADS)

Bhatt, R. B.; Kamat, H. S.; Ghosal, S. K.; de, P. K.

1999-10-01

The influence of nitrogen in shielding gas on the corrosion resistance of welds of a duplex stainless steel (grade U-50), obtained by gas tungsten arc (GTA) with filler wire, autogenous GTA (bead-on-plate), electron beam welding (EBW), and microplasma techniques, has been evaluated in chloride solutions at 30 °C. Pitting attack has been observed in GTA, electron beam welding, and microplasma welds when welding has been carried out using pure argon as the shielding gas. Gas tungsten arc welding with 5 to 10% nitrogen and 90 to 95% argon, as the shielding gas, has been found to result in an improved pitting corrosion resistance of the weldments of this steel. However, the resistance to pitting of autogenous welds (bead-on-plate) obtained in pure argon as the shielding gas has been observed to remain unaffected. Microscopic examination, electron probe microanalysis (EPMA), and x-ray diffraction studies have revealed that the presence of nitrogen in the shielding gas in the GTA welds not only modifies the microstructure and the austenite to ferrite ratio but also results in a nearly uniform distribution of the various alloying elements, for example, chromium, nickel, and molybdenum among the constitutent phases, which are responsible for improved resistance to pitting corrosion.

Understanding effect of 3.5 wt.% NaCl on the corrosion of Al0.1CoCrFeNi high-entropy alloy

NASA Astrophysics Data System (ADS)

Kumar, N.; Fusco, M.; Komarasamy, M.; Mishra, R. S.; Bourham, M.; Murty, K. L.

2017-11-01

High entropy alloys are a new class of metallic materials with potential for use in a wide variety of applications including their use in corrosive environment. The present study focused on the corrosion behavior of a single-phase, face-centered cubic high entropy alloy (HEA) Al0.1CoCrFeNi in as-cast condition, and the results are compared with the corrosion behavior of the SS304. The microstructural characterization of the alloys in as-received condition was carried out using optical microscopy, electron backscattered diffraction, energy dispersive spectroscopy, and X-ray diffraction. Corrosion behavior was studied using potentiodynamic polarization test in a 3.5 wt% NaCl solution and electrochemical impedance spectroscopy at room temperature. It was observed that the general corrosion resistance of the HEA was better than that of SS304. Pitting potential of the HEA was found to be superior to that of the SS304. Corrosion pits size was slightly smaller in SS304 than that in the HEA. 3D imaging determined that the pit depths were of the same order in both cases. Overall, the HEA Al0.1CoCrFeNi demonstrated a better resistance to general and pitting corrosion.

Influence of nitrogen in the shielding gas on corrosion resistance of duplex stainless steel welds

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

Bhatt, R.B.; Kamat, H.S.; Ghosal, S.K.

1999-10-01

The influence of nitrogen in shielding gas on the corrosion resistance of welds of a duplex stainless steel (grade U-50), obtained by gas tungsten arc (GTA) with filler wire, autogenous GTA (bead-on-plate), electron beam welding (EBW), and microplasma techniques, has been evaluated in chloride solutions at 30 C. Pitting attack has been observed in GTA, electron beam welding, and microplasma welds when welding has been carried out using pure argon as the shielding gas. Gas tungsten arc welding with 5 to 10% nitrogen and 90 to 95% argon, as the shielding gas, has been found to result in an improvedmore » pitting corrosion resistance of the weldments of this steel. However, the resistance of pitting of autogenous welds (bead-on-plate) obtained in pure argon as the shielding gas has been observed to remain unaffected. Microscopic examination, electron probe microanalysis (EPMA), and x-ray diffraction studies have revealed that the presence of nitrogen in the shielding gas in the GTA welds not only modifies the microstructure and the austenite to ferrite ratio but also results in a nearly uniform distribution of the various alloying elements, for example, chromium, nickel, and molybdenum among the constituent phases, which are responsible for improved resistance to pitting corrosion.« less

Electrochemical and passive behaviour of tin alloyed ferritic stainless steel in concrete environment

NASA Astrophysics Data System (ADS)

Luo, Hong; Su, Huaizhi; Li, Baosong; Ying, Guobing

2018-05-01

In the present work, the electrochemical behavior and semiconducting properties of a tin alloyed ferritic stainless steel in simulated concrete solution in presence of NaCl were estimated by conventional electrochemical methods such as potentiodynamic polarization, electrochemical impedance spectroscopy, and capacitance measurement (Mott-Schottky approach). The surface passive film was analyzed by X-ray photoelectron spectroscopy. The results revealed a good agreement between pitting corrosion, electrochemical behaviour, and electronic properties. The p and n-type bilayer structure passive film were observed. The increase of Sn4+ oxide species in the passive film shows no beneficial effects on the pitting corrosion. In addition, the dehydration of the passive film was further discussed.

Biochar from "Kon Tiki" flame curtain and other kilns: Effects of nutrient enrichment and kiln type on crop yield and soil chemistry

PubMed Central

Pandit, Naba Raj; Mulder, Jan; Hale, Sarah Elisabeth; Schmidt, Hans Peter

2017-01-01

Biochar application to soils has been investigated as a means of improving soil fertility and mitigating climate change through soil carbon sequestration. In the present work, the invasive shrub "Eupatorium adenophorum" was utilized as a sustainable feedstock for making biochar under different pyrolysis conditions in Nepal. Biochar was produced using several different types of kilns; four sub types of flame curtain kilns (deep-cone metal kiln, steel shielded soil pit, conical soil pit and steel small cone), brick-made traditional kiln, traditional earth-mound kiln and top lift up draft (TLUD). The resultant biochars showed consistent pH (9.1 ± 0.3), cation exchange capacities (133 ± 37 cmolc kg-1), organic carbon contents (73.9 ± 6.4%) and surface areas (35 to 215 m2/g) for all kiln types. A pot trial with maize was carried out to investigate the effect on maize biomass production of the biochars made with various kilns, applied at 1% and 4% dosages. Biochars were either pretreated with hot or cold mineral nutrient enrichment (mixing with a nutrient solution before or after cooling down, respectively), or added separately from the same nutrient dosages to the soil. Significantly higher CEC (P< 0.05), lower Al/Ca ratios (P< 0.05), and high OC% (P<0.001) were observed for both dosages of biochar as compared to non-amended control soils. Importantly, the study showed that biochar made by flame curtain kilns resulted in the same agronomic effect as biochar made by the other kilns (P > 0.05). At a dosage of 1% biochar, the hot nutrient-enriched biochar led to significant increases of 153% in above ground biomass production compared to cold nutrient-enriched biochar and 209% compared to biochar added separately from the nutrients. Liquid nutrient enhancement of biochar thus improved fertilizer effectiveness compared to separate application of biochar and fertilizer. PMID:28448621

Biochar from "Kon Tiki" flame curtain and other kilns: Effects of nutrient enrichment and kiln type on crop yield and soil chemistry.

PubMed

Pandit, Naba Raj; Mulder, Jan; Hale, Sarah Elisabeth; Schmidt, Hans Peter; Cornelissen, Gerard

2017-01-01

Biochar application to soils has been investigated as a means of improving soil fertility and mitigating climate change through soil carbon sequestration. In the present work, the invasive shrub "Eupatorium adenophorum" was utilized as a sustainable feedstock for making biochar under different pyrolysis conditions in Nepal. Biochar was produced using several different types of kilns; four sub types of flame curtain kilns (deep-cone metal kiln, steel shielded soil pit, conical soil pit and steel small cone), brick-made traditional kiln, traditional earth-mound kiln and top lift up draft (TLUD). The resultant biochars showed consistent pH (9.1 ± 0.3), cation exchange capacities (133 ± 37 cmolc kg-1), organic carbon contents (73.9 ± 6.4%) and surface areas (35 to 215 m2/g) for all kiln types. A pot trial with maize was carried out to investigate the effect on maize biomass production of the biochars made with various kilns, applied at 1% and 4% dosages. Biochars were either pretreated with hot or cold mineral nutrient enrichment (mixing with a nutrient solution before or after cooling down, respectively), or added separately from the same nutrient dosages to the soil. Significantly higher CEC (P< 0.05), lower Al/Ca ratios (P< 0.05), and high OC% (P<0.001) were observed for both dosages of biochar as compared to non-amended control soils. Importantly, the study showed that biochar made by flame curtain kilns resulted in the same agronomic effect as biochar made by the other kilns (P > 0.05). At a dosage of 1% biochar, the hot nutrient-enriched biochar led to significant increases of 153% in above ground biomass production compared to cold nutrient-enriched biochar and 209% compared to biochar added separately from the nutrients. Liquid nutrient enhancement of biochar thus improved fertilizer effectiveness compared to separate application of biochar and fertilizer.

The effect of functionalized polycarboxylate structures as corrosion inhibitors in a simulated concrete pore solution

NASA Astrophysics Data System (ADS)

Fazayel, A. S.; Khorasani, M.; Sarabi, A. A.

2018-05-01

In this study, the effects of polycarboxylate derivatives with different comonomers and functional groups on the control or reduction of corrosion in steel specimens were evaluated through electrochemical impedance spectroscopy (EIS) and potentiodynamic analysis. A highly alkaline contaminated concrete pore solution (CPS) containing chlorides was used to simulate the pitting corrosion, and according to the results, the mechanism of inhibitive action was determined. Both the inhibition efficiency and pitting corrosion inhibition of methacrylate-copolymers were in the order of poly methacrylate-co acrylamide > poly methacrylate-co-2-acrylamido-2 methylpropane sulfonic acid > poly methacrylate-co-hydroxyethyl methacrylate. In addition, the corrosion potential of steel specimens in all studied concentrations of NaCl with different concentrations of polymethacrylate-co acrylamide (as the best inhibitor in this study) in saturated Ca(OH)2 solution showed almost an identical trend. Polymethacrylic acid-co-acrylamide showed a 92.35% inhibitor efficiency in the saturated Ca(OH)2 solution containing 1.8 wt.% chlorides and could effectively reduce the corrosion rate. Even at 3.5 wt.% of NaCl, this inhibitor could remarkably reduce the destructive effect of chloride ion attacks on the steel surface and passive film. The inhibition effect of these polymeric inhibitors seemed to be due to the formation of a barrier layer on the metal surface, approved by the well-known adsorption mechanism of organic molecules at the metal/solution interface. The results of SEM, EDS and AFM investigations were also in agreement with the outcomes of electrochemical studies.

Influences of passivating elements on the corrosion and biocompatibility of super stainless steels.

PubMed

Yoo, Young-Ran; Jang, Soon-Geun; Oh, Keun-Taek; Kim, Jung-Gu; Kim, Young-Sik

2008-08-01

Biometals need high corrosion resistance since metallic implants in the body should be biocompatible and metal ion release should be minimized. In this work, we designed three kinds of super stainless steel and adjusted the alloying elements to obtain different microstructures. Super stainless steels contain larger amounts of Cr, Mo, W, and N than commercial alloys. These elements play a very important role in localized corrosion and, thus, their effects can be represented by the "pitting resistance equivalent number (PREN)." This work focused on the behavior which can arise when the bare surface of an implant in the body is exposed during walking, heavy exercise, and so on. Among the experimental alloys examined herein, Alloy Al and 316L stainless steels were mildly cytotoxic, whereas the other super austenitic, duplex, and ferritic stainless steels were noncytotoxic. This behavior is primarily related to the passive current and pitting resistance of the alloys. When the PREN value was increased, the passivation behavior in simulated body solution was totally different from that in acidic chloride solution and, thus, the Cr(2)O(3)/Cr(OH)(3) and [Metal oxide]/[Metal + Metal oxide] ratios of the passive film in the simulated body solution were larger than those in acidic chloride solution. Also, the critical current density in simulated body solution increased and, thus, active dissolution may induce metal ion release into the body when the PREN value and Ni content are increased. This behavior was closely related to the presence of EDTA in the simulated body solution. (c) 2007 Wiley Periodicals, Inc.

Studies of the phytoplankton and soil algae of two strip-mine impoundments in Tuscarawas County, Ohio

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

Richards, J.N.

1973-01-01

The process of strip-mining leaves vast areas that are denuded of vegetation and are open to primary succession by organisms such as algae. Acid strip-mine impoundments are either formed by man-made or natural processes. These impoundments are remnants of old strip-mine pits that have been filled with runoff water. The water chemistry of these ponds reflects the chemistry of the earth strata above the coal seam that was mined. These young impoundments or ponds are extremely low in pH and quite acidic due to the presence of great amounts of sulfuric acid. Algae that are found in these types ofmore » habitats exhibit a tolerance to acid conditions and are considered to be acidophilic. Few species of algae are known to be common componenets of these habitats.« less

Corrosion performance of alternative steam generator materials and designs. Volume 2. Posttest examination of a seawater-faulted alternative materials model steam generator. Final report. [PWR

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

Krupowicz, J.J.; Scott, D.B.; Fink, G.C.

Corrosion results obtained from the post-test non-destructive and destructive examinations of an alternative materials model steam generator are described in this final report. The model operated under representative thermal and hydraulic and accelerated (high seawater contaminant concentration) steam generator secondary water chemistry conditions. Total exposure consisted of 114 steaming days under all volatile treatment (AVT) chemistry conditions followed by 282 fault steaming days at a 30 ppM chloride concentration in the secondary bulk water. Various support plate and lattice strip support designs incorporated Types 347, 405, 409 and SCR-3 stainless steels; Alloys 600 and 690; and carbon steel. Heat transfermore » tube materials included Alloy 600 in various heat treated conditions, Alloy 690, and Alloy 800. All tubing materials in this test exhibited moderate pitting, primarily in the sludge pile region above the tubesheet.« less

Influence of Sulfur Content on the Corrosion Resistance of 17-4PH Stainless Steel

NASA Astrophysics Data System (ADS)

Tavares, S. S. M.; Pardal, J. M.; Martins, T. R. B.; da Silva, M. R.

2017-04-01

According to specification standards, the basic chemical composition of steel 17-4PH for special and critical applications is 15-17% Cr, 3.0-5.0% Ni, 3.0-5.0% Cu, 0.07% C (max) and 0.15-0.45% (Nb + Ta) (wt.%). The maximum sulfur content is 0.030%. However, as it will be shown in this work, this maximum limit for sulfur is too high for services where high corrosion resistance is necessary. Two samples of 17-4PH steel with similar base compositions, but quite different sulfur contents (0.027% and 0.001%S), were compared with respect to pitting corrosion and sensitization. Both materials were heat treated according to commercial treatments A, H900, H1100, H1150 and H1150D (ASTM A-1082). Two corrosion tests were applied to compare the steels. The first one was the double-loop electrochemical potentiodynamic reactivation (DL-EPR) test in 0.25 M H2SO4 + 0.01 KSCN solution, which is used to measure the degree of sensitization. The second test was the anodic polarization in 3.5%NaCl solution, commonly used to evaluate the pitting corrosion resistance. Detailed microstructural characterization by magnetic measurements, light optical and scanning electron microscopy was performed. As main conclusion, despite that both steels have chemical compositions in accordance with the standards, the steel with higher sulfur was much more susceptible to pitting and sensitization.

An Open Pit Nanofluidic Tool: Localized Chemistry Assisted by Mesoporous Thin Film Infiltration.

PubMed

Mercuri, Magalí; Pierpauli, Karina A; Berli, Claudio L A; Bellino, Martín G

2017-05-17

Nanofluidics based on nanoscopic porous structures has emerged as the next evolutionary milestone in the construction of versatile nanodevices with unprecedented applications. However, the straightforward development of nanofluidically interconnected systems is crucial for the production of practical devices. Here, we demonstrate that spontaneous infiltration into supramolecularly templated mesoporous oxide films at the edge of a sessile drop in open air can be used to connect pairs of landmarks. The liquids from the drops can then join through the nanoporous network to guide a localized chemical reaction at the nanofluid-front interface. This method, here named "open-pit" nanofluidics, allows mixing reagents from nanofluidically connected droplet reservoirs that can be used as reactors to conduct reactions and precipitation processes. From the fundamental point of view, the work contributes to unveiling subtle phenomena during spontaneous infiltration of fluids in bodies with nanoscale dimensions such as the front broadening effect and the oscillatory behavior of the infiltration-evaporation front. The approach has distinctive advantages such as easy fabrication, low cost, and facility of scaling up for future development of ultrasensitive detection, controlled nanomaterial synthesis, and novel patterning methods.

Conceptual Design Report Cask Loadout Sys and Cask Drop Redesign for the Immersion Pail Support Structure and Operator Interface Platform at 105 K West

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

LANGEVIN, A.S.

1999-07-12

This conceptual design report documents the redesign of the IPSS and the OIP in the 105 KW Basin south loadout pit due to a postulated cask drop accident, as part of Project A.5/A.6, Canister Transfer Facility Modifications. Project A.5/A.6 involves facility modifications needed to transfer fuel from the basin into the cask-MCO. The function of the IPSS is to suspend, guide, and position the immersion pail. The immersion pail protects the cask-MCO from contamination by basin water and acts as a lifting device for the cask-MCO. The OIP provides operator access to the south loadout pit. Previous analyses studied themore » effects of a cask-MCO drop on the south loadout pit concrete structure and on the IPSS. The most recent analysis considered the resulting loads at the pit slab/wall joint (Kanjilal, 1999). This area had not been modeled previously, and the analysis results indicate that the demand capacity exceeds the allowable at the slab/wall joint. The energy induced on the south loadout pit must be limited such that the safety class function of the basin is maintained. The solution presented in this CDR redesigns the IPSS and the OIP to include impact-absorbing features that will reduce the induced energy. The impact absorbing features of the new design include: Impact-absorbing material at the IPSS base and at the upper portion of the IPSS legs. A sleeve which provides a hydraulic means of absorbing energy. Designing the OIP to act as an impact absorber. The existing IPSS structure in 105 KW will be removed. This conceptual design considers only loads resulting from drops directly over the IPSS and south loadout pit area. Drops in other areas of the basin are not considered, and will be covered as part of a future revision to this CDR.« less

Growth and dislocation studies of β-HMX.

PubMed

Gallagher, Hugh G; Sherwood, John N; Vrcelj, Ranko M

2014-01-01

The defect structure of organic materials is important as it plays a major role in their crystal growth properties. It also can play a subcritical role in "hot-spot" detonation processes of energetics and one such energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX). The as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic of mechanical deformation by dislocation slip. Crystals of β-HMX grown from acetone show good morphological agreement with that predicted by modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution. Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays. On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits are associated with pure screw dislocations with b = [010]. Graphical abstractEtch pits on the twinned (010) face of β-HMX.

Composition of CBRN Decontamination Effluent and Development of Surrogate Mixtures for Testing Effluent Treatment Technologies

DTIC Science & Technology

2016-07-01

possible, the site around the wash stations is graded to allow the wash water to run off to a pit, where it can seep into the earth or be collected...Caustic soda solution Radioisotopes /Nuclear Residuals Soap with warm water DS2 = Decontamination Solution 2 STB = Super Tropical bleach HTH = High... DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

Corrosion behaviour of Nitinol alloy coated with alkylsilanes and polypyrrole.

PubMed

Flamini, D O; Saidman, S B

2014-11-01

Nitinol (equiatomic Ni and Ti alloy (NiTi)) substrate was modified using a coating system formed by a self-assembled film of alkylsilane compounds (propyltrichlorosilane (C3H7SiCl3) or octadecyltrichlorosilane (C18H37SiCl3)) and polypyrrole (PPy) doped with sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol OT or AOT). The combination of alkylsilanes and the presence of a voluminous molecule like AOT entrapped into the PPy films improve the pitting corrosion resistance of the substrate in chloride solution. The best performance was achieved with the longest alkylsilane chains, where the PPy film remains adhered to the underlying coating after a pitting corrosion test. Copyright © 2014 Elsevier B.V. All rights reserved.

A potentiodynamic study of aluminum-lithium alloys in an aqueous sodium chloride environment

NASA Technical Reports Server (NTRS)

Tsao, C.-H. T.; Pizzo, P. P.

1985-01-01

The characteristics of the potentiodynamic curves for Al-Li alloys in 3.5 percent NaCl aqueous solution are explained and the electrochemical parameters of the potentiodynamic technique are correlated to observed pitting and intergranular cracking behavior. It is shown that the oxygen content of the sodium chloride electrolyte plays an important role in the electrochemical behavior of Al-Li alloys. The potentiodynamic behavior of the alloys is found to be insensitive to variation in compositional content and heat treatment, both of which affect the stress-corrosion behavior. Stringer oxide particle attack and random pitting are observed. It is shown that alternate-immersion exposure prior to potentiodynamic polarization may offer a means of assessing susceptibility to stress-corrosion cracking.

Spectroscopic and microscopic investigation of MBE-grown CdTe (211)B epitaxial thin films on GaAs (211)B substrates

NASA Astrophysics Data System (ADS)

Özden, Selin; Koc, Mumin Mehmet

2018-03-01

CdTe epitaxial thin films, for use as a buffer layer for HgCdTe defectors, were grown on GaAs (211)B using the molecular beam epitaxy method. Wet chemical etching (Everson method) was applied to the epitaxial films using various concentrations and application times to quantify the crystal quality and dislocation density. Surface characterization of the epitaxial films was achieved using Atomic force microscopy and Scanning electron microscopy (SEM) before and after each treatment. The Energy Dispersive X-Ray apparatus of SEM was used to characterize the chemical composition. Untreated CdTe films show smooth surface characteristics with root mean square (RMS) roughnesses of 1.18-3.89 nm. The thicknesses of the CdTe layers formed were calculated via FTIR spectrometry and obtained by ex situ spectroscopic ellipsometry. Raman spectra were obtained for various temperatures. Etch pit densities (EPD) were measured, from which it could be seen that EPD changes between 1.7 × 108 and 9.2 × 108 cm-2 depending on the concentration of the Everson etch solution and treatment time. Structure, shape and depth of pits resulting from each etch pit implementation were also evaluated. Pit widths varying between 0.15 and 0.71 µm with heights varying between 2 and 80 nm were observed. RMS roughness was found to vary by anything from 1.56 to 26 nm.

In vitro corrosion resistance of plasma source ion nitrided austenitic stainless steels.

PubMed

Le, M K; Zhu, X M

2001-04-01

Plasma source ion nitriding has emerged as a low-temperature, low-pressure nitriding approach for low-energy implanting nitrogen ions and then diffusing them into steel and alloy. In this work, a single high nitrogen face-centered-cubic (f.c.c.) phase (gammaN) formed on the 1Cr18Ni9Ti and AISI 316L austenitic stainless steels with a high nitrogen concentration of about 32 at % was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing angle X-ray diffraction, and transmission electron microscopy. The corrosion resistance of the gammaN-phase layer was studied by the electrochemical cyclic polarization measurement in Ringer's solutions buffered to pH from 3.5 to 7.2 at a temperature of 37 degrees C. No pitting corrosion in the Ringer's solutions with pH = 7.2 and 5.5 was detected for the gammaN-phase layers on the two stainless steels. The high pitting potential for the gammaN-phase layers is higher, about 500 and 600 mV, above that of the two original stainless steels, respectively, in the Ringer's solution with pH = 3.5. The corroded surface morphologies of the gammaN-phase layers observed by scanning electron microscopy are consistent with the results of the electrochemical polarization measurement.

Solutions, Unit 5: Colligative Properties of Solutions. A Computer-Enriched Module for Introductory Chemistry. Student's Guide and Teacher's Guide.

ERIC Educational Resources Information Center

Bader, Morris

Presented are the teacher's guide and student manual for one of a series of self-instructional, computer-based learning modules for an introductory, undergraduate chemistry course. The student manual for this unit on the colligative properties of solutions includes objectives, prerequisites, pretest, discussion, and 20 problem sets. Included in…

Corrosion and Corrosion-Fatigue Behavior of 7075 Aluminum Alloys Studied by In Situ X-Ray Tomography

NASA Astrophysics Data System (ADS)

Stannard, Tyler

7XXX Aluminum alloys have high strength to weight ratio and low cost. They are used in many critical structural applications including automotive and aerospace components. These applications frequently subject the alloys to static and cyclic loading in service. Additionally, the alloys are often subjected to aggressive corrosive environments such as saltwater spray. These chemical and mechanical exposures have been known to cause premature failure in critical applications. Hence, the microstructural behavior of the alloys under combined chemical attack and mechanical loading must be characterized further. Most studies to date have analyzed the microstructure of the 7XXX alloys using two dimensional (2D) techniques. While 2D studies yield valuable insights about the properties of the alloys, they do not provide sufficiently accurate results because the microstructure is three dimensional and hence its response to external stimuli is also three dimensional (3D). Relevant features of the alloys include the grains, subgrains, intermetallic inclusion particles, and intermetallic precipitate particles. The effects of microstructural features on corrosion pitting and corrosion fatigue of aluminum alloys has primarily been studied using 2D techniques such as scanning electron microscopy (SEM) surface analysis along with post-mortem SEM fracture surface analysis to estimate the corrosion pit size and fatigue crack initiation site. These studies often limited the corrosion-fatigue testing to samples in air or specialized solutions, because samples tested in NaCl solution typically have fracture surfaces covered in corrosion product. Recent technological advancements allow observation of the microstructure, corrosion and crack behavior of aluminum alloys in solution in three dimensions over time (4D). In situ synchrotron X-Ray microtomography was used to analyze the corrosion and cracking behavior of the alloy in four dimensions to elucidate crack initiation at corrosion pits for samples of multiple aging conditions and impurity concentrations. Additionally, chemical reactions between the 3.5 wt% NaCl solution and the crack surfaces were quantified by observing the evolution of hydrogen bubbles from the crack. The effects of the impurity particles and age-hardening particles on the corrosion and fatigue properties were examined in 4D.

3D Pit Stop Printing

ERIC Educational Resources Information Center

Wright, Lael; Shaw, Daniel; Gaidds, Kimberly; Lyman, Gregory; Sorey, Timothy

2018-01-01

Although solving an engineering design project problem with limited resources or structural capabilities of materials can be part of the challenge, students making their own parts can support creativity. The authors of this article found an exciting solution: 3D printers are not only one of several tools for making but also facilitate a creative…

CASE STUDY: IN-SITU SOLIDIFICATION/STABILIZATION OF HAZARDOUS ACID WASTE OIL SLUDGE AND LESSONS LEARNED

EPA Science Inventory

The South 8th Street site contained a 2.5 acre oily sludge pit with very low pH waste produced by oil recycling activities. This sludge was treated using in-situ solidification/stabilization technology applied by deep soil mixing augers. The problems encountered, solutions develo...

Exploiting Locality in Quantum Computation for Quantum Chemistry.

PubMed

McClean, Jarrod R; Babbush, Ryan; Love, Peter J; Aspuru-Guzik, Alán

2014-12-18

Accurate prediction of chemical and material properties from first-principles quantum chemistry is a challenging task on traditional computers. Recent developments in quantum computation offer a route toward highly accurate solutions with polynomial cost; however, this solution still carries a large overhead. In this Perspective, we aim to bring together known results about the locality of physical interactions from quantum chemistry with ideas from quantum computation. We show that the utilization of spatial locality combined with the Bravyi-Kitaev transformation offers an improvement in the scaling of known quantum algorithms for quantum chemistry and provides numerical examples to help illustrate this point. We combine these developments to improve the outlook for the future of quantum chemistry on quantum computers.

Corrosion of orthodontic brackets in different spices: in vitro study.

PubMed

Chaturvedi, T P

2014-01-01

Moist environment in the mouth varies and causes variable amounts of corrosion of dental materials. This is of concern particularly when metallic implants, metallic fillings, orthodontic appliances are placed in the hostile electrolytic environment in the human mouth. Components of diet rich in salt and spices are important factors influencing the corrosion of metallic appliances placed in the oral cavity. To study in vitro corrosion of orthodontic metallic brackets immersed in solutions of salt and spices in artificial saliva. Orthodontic brackets were used for corrosion studies in artificial saliva, salt, and spices using electrochemical technique and surface analysis. Electrochemical studies using different parameters were done in solutions of artificial saliva containing salt and spices. Photomicrographs from the optical microscope were also obtained. RESULTS of corrosion studies have clearly demonstrated that certain spices such as turmeric and coriander are effective in reducing corrosion, whereas salt and red chili have been found to enhance it. Surface analysis of small pits present on the surface of the as-received bracket will initiate corrosion which leads to more pitting.

Ultrasonic cavitation erosion of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in NaCl solution.

PubMed

Hong, Sheng; Wu, Yuping; Zhang, Jianfeng; Zheng, Yugui; Qin, Yujiao; Lin, Jinran

2015-09-01

The high-velocity oxygen-fuel (HVOF) spraying process was used to prepare near-nanostructured WC-10Co-4Cr coating. The cavitation erosion behavior and mechanism of the coating in 3.5 wt.% NaCl solution were analyzed in detail. The results showed that the amorphous phase and WC grain were present in the coating. The cavitation erosion resistance of the coating was about 1.27 times that of the stainless steel 1Cr18Ni9Ti under the same testing conditions. The effects of erosion time on the microstructural evolution were discussed. It was revealed that cracks initiated at the edge of pre-existing pores and propagated along the carbide-binder interface, leading to the pull-out of carbide particle and the formation of pits and craters on the surface. The main failure mechanism of the coating was erosion of the binder phases, brittle detachment of hard phases and formation of pitting corrosion products. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrochemical studies of Copper, Tantalum and Tantalum Nitride surfaces in aqueous solutions for applications in chemical-mechanical and electrochemical-mechanical planarization

NASA Astrophysics Data System (ADS)

Sulyma, Christopher Michael

This report will investigate fundamental properties of materials involved in integrated circuit (IC) manufacturing. Individual materials (one at a time) are studied in different electrochemical environmental solutions to better understand the kinetics associated with the polishing process. Each system tries to simulate a real CMP environment in order to compare our findings with what is currently used in industry. To accomplish this, a variety of techniques are used. The voltage pulse modulation technique is useful for electrochemical processing of metal and alloy surfaces by utilizing faradaic reactions like electrodeposition and electrodissolution. A theoretical framework is presented in chapter 4 to facilitate quantitative analysis of experimental data (current transients) obtained in this approach. A typical application of this analysis is demonstrated for an experimental system involving electrochemical removal of copper surface layers, a relatively new process for abrasive-free electrochemical mechanical planarization of copper lines used in the fabrication of integrated circuits. Voltage pulse modulated electrodissolution of Cu in the absence of mechanical polishing is activated in an acidic solution of oxalic acid and hydrogen peroxide. The current generated by each applied voltage step shows a sharp spike, followed by a double-exponential decay, and eventually attains the rectangular shape of the potential pulses. For the second system in chapter 5, open-circuit potential measurements, cyclic voltammetry and Fourier transform impedance spectroscopy have been used to study pH dependent surface reactions of Cu and Ta rotating disc electrodes (RDEs) in aqueous solutions of succinic acid (SA, a complexing agent), hydrogen peroxide (an oxidizer), and ammonium dodecyl sulfate (ADS, a corrosion inhibitor for Cu). The surface chemistries of these systems are relevant for the development of a single-slurry approach to chemical mechanical planarization (CMP) of Cu lines and Ta barriers in the fabrication of semiconductor devices. It is shown that in non-alkaline solutions of H2O2, the SA-promoted surface complexes of Cu and Ta can potentially support chemically enhanced material removal in low-pressure CMP of surface topographies overlying fragile low-k dielectrics. ADS can suppress Cu dissolution without significantly affecting the surface chemistry of Ta. Chapter 6 discusses anodic corrosion of Ta, which is examined as a possible route to voltage induced removal of Ta for potential applications in electrochemical mechanical planarization (ECMP) of diffusion barriers. This strategy involves electro-oxidation of Ta in the presence of NO3- anions to form mechanically weak surface oxide films, followed by removal of the oxide layers by moderate mechanical abrasion. This NO3 - system is compared with a reference solution of Br -. In both electrolytes, the voltammetric currents of anodic oxidation exhibit oscillatory behaviors in the initial cycles of slow (5 mV s-1) voltage scans. The frequencies of these current oscillations are show signature attributes of localized pitting or general surface corrosion caused by Br- or NO3 -, respectively. Scanning electron microscopy, cyclic voltammetry, polarization resistance measurements, and time resolved Fourier transform impedance spectroscopy provide additional details about these corrosion mechanism. Apart from their relevance in the context of ECMP, the results also address certain fundamental aspects of pitting and general corrosions. The general protocols necessary to combine and analyze the results of D.C. and A.C. electrochemical measurements involving such valve metal corrosion systems are discussed in detail. In chapter 7 potassium salts of certain oxyanions (nitrate, sulfate and phosphate in particular) are shown to serve as effective surface-modifying agents in chemically enhanced, low-pressure chemical mechanical planarization (CMP) of Ta and TaN barrier layers for interconnect structures. The surface reactions that form the basis of this CMP strategy are investigated here in detail using the electrochemical techniques of cyclic voltammetry, open circuit potential analysis, polarization resistance measurements, and Fourier transform impedance spectroscopy. The results suggest that forming structurally weak oxide layers on the CMP samples is a key to achieving the goal of chemically controlled CMP of Ta/TaN at low down-pressures. (Abstract shortened by UMI.)

A Wet Chemistry Laboratory Cell

NASA Image and Video Library

2008-06-26

This picture of NASA Phoenix Mars Lander Wet Chemistry Laboratory WCL cell is labeled with components responsible for mixing Martian soil with water from Earth, adding chemicals and measuring the solution chemistry.

Desorption of 1,3,5-Trichlorobenzene from Multi-Walled Carbon Nanotubes: Impact of Solution Chemistry and Surface Chemistry

PubMed Central

Ma, Xingmao; Uddin, Sheikh

2013-01-01

The strong affinity of carbon nanotubes (CNTs) to environmental contaminants has raised serious concern that CNTs may function as a carrier of environmental pollutants and lead to contamination in places where the environmental pollutants are not expected. However, this concern will not be realized until the contaminants are desorbed from CNTs. It is well recognized that the desorption of environmental pollutants from pre-laden CNTs varies with the environmental conditions, such as the solution pH and ionic strength. However, comprehensive investigation on the influence of solution chemistry on the desorption process has not been carried out, even though numerous investigations have been conducted to investigate the impact of solution chemistry on the adsorption of environmental pollutants on CNTs. The main objective of this study was to determine the influence of solution chemistry (e.g., pH, ionic strength) and surface functionalization on the desorption of preloaded 1,3,5-trichlorobenzene (1,3,5-TCB) from multi-walled carbon nanotubes (MWNTs). The results suggested that higher pH, ionic strength and natural organic matter in solution generally led to higher desorption of 1,3,5-TCB from MWNTs. However, the extent of change varied at different values of the tested parameters (e.g., pH < 7 vs. pH > 7). In addition, the impact of these parameters varied with MWNTs possessing different surface functional groups, suggesting that surface functionalization could considerably alter the environmental behaviors and impact of MWNTs. PMID:28348336

The Ground Flash Fraction Retrieval Algorithm Employing Differential Evolution: Simulations and Applications

NASA Technical Reports Server (NTRS)

Koshak, William; Solakiewicz, Richard

2012-01-01

The ability to estimate the fraction of ground flashes in a set of flashes observed by a satellite lightning imager, such as the future GOES-R Geostationary Lightning Mapper (GLM), would likely improve operational and scientific applications (e.g., severe weather warnings, lightning nitrogen oxides studies, and global electric circuit analyses). A Bayesian inversion method, called the Ground Flash Fraction Retrieval Algorithm (GoFFRA), was recently developed for estimating the ground flash fraction. The method uses a constrained mixed exponential distribution model to describe a particular lightning optical measurement called the Maximum Group Area (MGA). To obtain the optimum model parameters (one of which is the desired ground flash fraction), a scalar function must be minimized. This minimization is difficult because of two problems: (1) Label Switching (LS), and (2) Parameter Identity Theft (PIT). The LS problem is well known in the literature on mixed exponential distributions, and the PIT problem was discovered in this study. Each problem occurs when one allows the numerical minimizer to freely roam through the parameter search space; this allows certain solution parameters to interchange roles which leads to fundamental ambiguities, and solution error. A major accomplishment of this study is that we have employed a state-of-the-art genetic-based global optimization algorithm called Differential Evolution (DE) that constrains the parameter search in such a way as to remove both the LS and PIT problems. To test the performance of the GoFFRA when DE is employed, we applied it to analyze simulated MGA datasets that we generated from known mixed exponential distributions. Moreover, we evaluated the GoFFRA/DE method by applying it to analyze actual MGAs derived from low-Earth orbiting lightning imaging sensor data; the actual MGA data were classified as either ground or cloud flash MGAs using National Lightning Detection Network[TM] (NLDN) data. Solution error plots are provided for both the simulations and actual data analyses.

Influence of ultrasound pretreatment on wood physiochemical structure.

PubMed

He, Zhengbin; Wang, Zhenyu; Zhao, Zijian; Yi, Songlin; Mu, Jun; Wang, Xiaoxu

2017-01-01

As an initial step to increase the use of renewable biomass resources, this study was aimed at investigating the effects of ultrasound pretreatment on structural changes of wood. Samples were pretreated by ultrasound with the power of 300W and frequency of 28kHz in aqueous soda solution, aqueous acetic acid, or distilled water, then pretreated and control samples were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The results shown that ultrasound pretreatment is indeed effective in modifying the physiochemical structure of eucalyptus wood; the pretreatment decreased the quantity of alkali metals (e.g., potassium, calcium and magnesium) in the resulting material. Compared to the control group, the residual char content of samples pretreated in aqueous soda solution increased by 10.08%-20.12% and the reaction temperature decreased from 361°C to 341°C, however, in samples pretreated by ultrasound in acetic solution or distilled water, the residual char content decreased by 12.40%-21.45% and there were no significant differences in reactivity apart from a slightly higher maximum reaction rate. Ultrasound pretreatment increased the samples' crystallinity up to 35.5% and successfully removed cellulose, hemicellulose, and lignin from the samples; the pretreatment also increased the exposure of the sample to the treatment solutions, broke down sample pits, and generated collapses and microchannels on sample pits, and removed attachments in the samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Raman-atomic force microscopy of the ommatidial surfaces of Dipteran compound eyes.

PubMed

Anderson, Mark S; Gaimari, Stephen D

2003-06-01

The ommatidial lens surfaces of the compound eyes in several species of files (Insecta: Diptera) and a related order (Mecoptera) were analyzed using a recently developed Raman-atomic force microscope. We demonstrate in this work that the atomic force microscope (AFM) is a potentially useful instrument for gathering phylogenetic data and that the newly developed Raman-AFM may extend this application by revealing nanometer-scale surface chemistry. This is the first demonstration of apertureless near-field Raman spectroscopy on an intact biological surface. For Chrysopilus testaceipes Bigot (Rhagionidae), this reveals unique cerebral cortex-like surface ridges with periodic variation in height and surface chemistry. Most other Brachyceran flies, and the "Nematoceran" Sylvicola fenestralis (Scopoli) (Anisopodidae), displayed the same morphology, while other taxa displayed various other characteristics, such as a nodule-like (Tipula (Triplicitipula) sp. (Tipulidae)) or coalescing nodule-like (Tabanus punctifer Osten Sacken (Tabanidae)) morphology, a smooth morphology with distinct pits and grooves (Dilophus orbatus (Say) (Bibionidae)), or an entirely smooth surface (Bittacus chlorostigma MacLachlan (Mecoptera: Bittacidae)). The variation in submicrometer structure and surface chemistry provides a new information source of potential phylogenetic importance, suggesting the Raman-atomic force microscope could provide a new tool useful to systematic and evolutionary inquiry.

Raman-atomic force microscopy of the ommatidial surfaces of Dipteran compound eyes

NASA Technical Reports Server (NTRS)

Anderson, Mark S.; Gaimari, Stephen D.

2003-01-01

The ommatidial lens surfaces of the compound eyes in several species of files (Insecta: Diptera) and a related order (Mecoptera) were analyzed using a recently developed Raman-atomic force microscope. We demonstrate in this work that the atomic force microscope (AFM) is a potentially useful instrument for gathering phylogenetic data and that the newly developed Raman-AFM may extend this application by revealing nanometer-scale surface chemistry. This is the first demonstration of apertureless near-field Raman spectroscopy on an intact biological surface. For Chrysopilus testaceipes Bigot (Rhagionidae), this reveals unique cerebral cortex-like surface ridges with periodic variation in height and surface chemistry. Most other Brachyceran flies, and the "Nematoceran" Sylvicola fenestralis (Scopoli) (Anisopodidae), displayed the same morphology, while other taxa displayed various other characteristics, such as a nodule-like (Tipula (Triplicitipula) sp. (Tipulidae)) or coalescing nodule-like (Tabanus punctifer Osten Sacken (Tabanidae)) morphology, a smooth morphology with distinct pits and grooves (Dilophus orbatus (Say) (Bibionidae)), or an entirely smooth surface (Bittacus chlorostigma MacLachlan (Mecoptera: Bittacidae)). The variation in submicrometer structure and surface chemistry provides a new information source of potential phylogenetic importance, suggesting the Raman-atomic force microscope could provide a new tool useful to systematic and evolutionary inquiry.

Filtrates & Residues: A "Semimicro" Spectrophotometric Determination of the Ksp of Silver Acetate at Various Temperatures.

ERIC Educational Resources Information Center

Liebermann, John, Jr.; Yun, Ki J.

1988-01-01

Examines a solubility laboratory experiment using silver acetate and spectrophotometers for an Advanced Placement chemistry course. Covers experimental procedure, analysis of saturated solutions, and a discussion of chemistry involved. Includes an absorbance curve for silver ions and solution preparation suggestions. (ML)

Farewell to Alexandria: Solutions to Space, Growth, and Performance Problems of Libraries.

ERIC Educational Resources Information Center

Gore, Daniel, Ed.

All of the contributions in this volume, except the last, were presented at a conference sponsored by the Associated Colleges of the Midwest, held in Chicago, April 17-18, 1975. Entitled "Touching Bottom in the Bottomless Pit," the conference was intended to open a national debate on space, growth, and performance problems of…

Ground-water conditions and effects of mine dewatering in Desert Valley, Humboldt and Pershing Counties, northwestern Nevada, 1962-91

USGS Publications Warehouse

Berger, D.L.

1995-01-01

Desert Valley is a 1,200-square-mile, north- trending, structural basin, about 30 miles northwest of Winnemucca, Nevada. Unconsolidated basin-fill deposits exceeding 7,000 feet in thickness constitute the primary ground-water reservoir. Dewatering operations at an open-pit mine began in the Spring of 1985 in the northeast part of Desert Valley. Ground-water withdrawal for mine dewatering in 1991 was greater than three times the estimated average annual recharge from precipitation. The mine discharge water has been allowed to flow to areas west of the mine where it has created an artificial wetlands. This report documents the 1991 hydrologic conditions in Desert Valley and the change in conditions since predevelopment (pre-1962). It also summarizes the results of analyzing the simulated effects of open-pit mine dewatering on a basin-wide scale over time. Water-level declines associated with the dewatering have propagated north and south of the mine, but have been attenuated to the west due to the infiltration beneath the artificial wetlands. Maximum water-level declines beneath the open pits at the mine, as of Spring 1991, are about 300 feet. Changes in the hydrologic conditions since predevelopment are observed predominantly near the dewatering operations and the associated discharge lakes. General ground-water chemistry is essentially unchanged since pre- development. On the basis of a ground-water flow model used to simulate mine dewatering, a new equilibrium may slowly be approached only after 100 years of recovery from the time mine dewatering ceases.

Actinides-1981

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

Not Available

Abstracts of 134 papers which were presented at the Actinides-1981 conference are presented. Approximately half of these papers deal with electronic structure of the actinides. Others deal with solid state chemistry, nuclear physic, thermodynamic properties, solution chemistry, and applied chemistry.

Fundamental investigation of stress corrosion cracking

NASA Technical Reports Server (NTRS)

Beck, T. R.; Blackburn, M. J.; Smyrl, W. H.

1972-01-01

Two principle areas studied were stress corrosion crack growth rates of a titanium alloy in liquid environments containing halide ions and pitting corrosion of titanium in bromide solutions. Two initial assumptions were made, that the rate of propagation was controlled by a macroscopic solution parameter and that this parameter was viscosity. A series of solutions were prepared using lithium chloride as the solute and water, methanol, glycerin, formic acid, acetone, dimethyl sulphoxide, etc. As solvents, these solutions were prepared with a 5:1 solvent-solute ratio. Viscosity was varied by changing the temperature and it was found: (1) In all solvents the velocity of cracking was proportional to the reciprocal of the viscosity. (2) Each solvent gave a separate relationship, (3) The temperature dependence and numerical values for the apparent activation energy of cracking and viscosity were the same.

Sodium-dependent phosphate cotransporters and phosphate-induced calcification of vascular smooth muscle cells: Redundant roles for PiT-1 and PiT-2

PubMed Central

Crouthamel, Matthew H.; Lau, Wei Ling; Leaf, Elizabeth M.; Chavkin, Nick; Wallingford, Mary C.; Peterson, Danielle F.; Li, Xianwu; Liu, Yonggang; Chin, Michael T.; Levi, Moshe; Giachelli, Cecilia M.

2014-01-01

Objective Elevated serum phosphate has emerged as a major risk factor for vascular calcification. The sodium-dependent phosphate cotransporter, PiT-1, was previously shown to be required for phosphate-induced osteogenic differentiation and calcification of cultured human VSMCs, but its importance in vascular calcification in vivo, as well as the potential role of its homologue, PiT-2, have not been determined. We investigated the in vivo requirement for PiT-1 in vascular calcification using a mouse model of chronic kidney disease, and the potential compensatory role of PiT-2 using in vitro knockdown and over-expression strategies. Approach and Results Mice with targeted deletion of PiT-1 in VSMCs were generated (PiT-1Δsm). PiT-1 mRNA levels were undetectable whereas PiT-2 mRNA levels were increased 2 fold in the vascular aortic media of PiT-1Δsm compared to PiT-1flox/flox control. When arterial medial calcification was induced in PiT-1Δsm and PiT-1flox/flox by chronic kidney disease followed by dietary phosphate loading, the degree of aortic calcification was not different between genotypes, suggesting compensation by PiT-2. Consistent with this possibility, VSMCs isolated from PiT-1Δsm mice had no PiT-1 mRNA expression, increased PiT-2 mRNA levels, and no difference in sodium-dependent phosphate uptake or phosphate-induced matrix calcification compared to PiT-1flox/flox VSMCs. Knockdown of PiT-2 decreased phosphate uptake and phosphate-induced calcification of PiT-1Δsm VSMCs. Furthermore, over-expression of PiT-2 restored these parameters in human PiT-1-deficient VSMCs. Conclusions PiT-2 can mediate phosphate uptake and calcification of VSMCs in the absence of PiT-1. Mechanistically, PiT-1 and PiT-2 appear to serve redundant roles in phosphate-induced calcification of vascular smooth muscle cells. PMID:23968976

Chemistry of americium

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

Schulz, W.W.

1976-01-01

Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, separation, purification. Author and subject indexes are included. (JCB)

Chemistry Comes Alive!, Volume 4: Abstract of Special Issue 25 on CD-ROM

NASA Astrophysics Data System (ADS)

Jacobsen, Jerrold J.; Bain, Gordon; Bruce, Kara; Moore, John W.

2000-06-01

The answers can be found on p676 of the PDF version of the Table of Contents. Chemistry Comes Alive!, Volume 4 is the fourth in a series of CD-ROMs for Macintosh and Windows computers. (Chemistry Comes Alive!, Volumes 1, 2, and 3 (1-3), are also available from JCE Software.) Volume 4 contains two main topics, Reactions in Aqueous Solution and Reactions of the Elements. Chemistry truly does come to life through this collection of pictures, animations, and movies depicting chemical reactions. Topic I. Reactions in Aqueous Solution Reactions in Aqueous Solution includes video of the mixing and subsequent reaction, if any, of aqueous solutions of inorganic compounds. The compounds and ions included are listed below. Reactions with a specific compound can be accessed either by selecting the compound from an alphabetical list of the compounds or from a matrix of reactions. There are more than 200 movies of reactions from which to choose. There are also still images of each reaction. Reactions are shown in which reactants are mixed in either order; there are images of solution 2 being added to solution 1 as well as images of solution 1 being added to solution 2. In addition to videos of reactions, a quiz is available in which a matrix of unknown solutions is presented. Students attempt to identify the solutions by viewing video of each unknown solution as it is mixed with another unknown solution. Students may compare their observations from mixing the unknowns with reactions of known solutions. Topic II. Reactions of the Elements Reactions of the Elements includes video of the elements reacting with air, water, acids, and base. (This video is also used in JCE Software's popular Periodic Table Live! (4) and is included here to allow you greater freedom to use the video in your own presentations under the Chemistry Comes Alive! license.) In addition you may purchase an additional license that allows you to place all or a portion of the video on your WWW site. Contact JCE Software for more details. Chemistry Comes Alive! Volume 4: Reactions in Aqueous Solution Compounds and Ions Ammonia, NH3 Barium chloride, BaCl2 Cadmium nitrate, Cd(NO3)2 Chromium(III) chloride, CrCl3 Cobalt(II) chloride, CoCl2 Copper(II) nitrate, Cu(NO3)2 Copper(II) sulfate, CuSO4 Hydrochloric acid, HCl Iron(II) ion, Fe2+ Iron(III) ion, Fe3+ Lead(II) nitrate, Pb(NO3)2 Manganese(II) chloride, MnCl2 Mercury(I) nitrate, Hg2(NO3)2 Mercury(II) ion, Hg2+ Nickel(II) nitrate, Ni(NO3)2 Silver nitrate, AgNO3 Sodium bromide, NaBr Sodium carbonate, Na2CO3 Sodium chloride, NaCl Sodium hydroxide, NaOH Sodium iodide, NaI Sodium sulfate, Na2SO4 Sodium sulfide, Na2S Strontium chloride, SrCl2 Sulfuric acid, H2SO4 Zinc nitrate, Zn(NO3)2 About the Chemistry Comes Alive! Series In Chemistry Comes Alive!, the emphasis is on the chemistry. Reactions are shown close up. Only where scale is important can more than the demonstrator's hands be seen. Most movies in Chemistry Comes Alive! include a voice-over narration and the sound of a reaction is included when it is important. Reactions or demonstrations have been chosen because they illustrate an important aspect of chemistry, involve substances or equipment that are not available in many schools, or are hazardous or cause problems of disposal or cleanup. All are certain to stimulate students' curiosity and help them learn. The Chemistry Comes Alive! series is divided into several CD volumes on related topics as recommended by a group of chemistry educators. How to Use This CD-ROM The Chemistry Comes Alive! CD-ROMs are organized in the manner of a World Wide Web site. You access their contents with a browser such as Netscape Navigator or Microsoft Internet Explorer. Chemistry Comes Alive! Volume 4 provides links to JCE Online where you can find information about other Chemistry Comes Alive! volumes. JCE Software hopes you will let us know how you use Chemistry Comes Alive! in your classroom so that we can share with others contributed ideas, lessons, or instructional materials that utilize Chemistry Comes Alive! The movies on this CD-ROM are QuickTime movies. In addition to viewing with a WWW browser, the video can be played directly using QuickTime MoviePlayer. Images from the CD can be easily incorporated into multimedia presentations or lessons. Use of the Bookmark function of the Web browser is a particularly convenient method of organizing material for a lecture or for a student lesson. Remember that an additional license must be purchased before you place video from any CCA! volume on your local WWW server. Images of the reactions of potassium, selected from movies on Reactions of the Elements Acknowledgments Funding for Chemistry Comes Alive! was provided by the National Science Foundation, New Traditions, grant DUE-9455928 and National Science Foundation, Instructional Materials Development grant ESI-9154099. Many individuals made significant contributions to the development of this project. These include Alton Banks, North Carolina State University; Joe March, University of Alabama at Birmingham. Price and Ordering An order form is inserted in this issue that provides prices and other ordering information. If this card is not available or if you need additional information, contact JCE Software, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1396; phone; 608/262-5153 or 800/991-5534; fax: 608/265-8094; email: jcesoft@chem.wisc.edu. Information about all our publications (including abstracts, descriptions, updates) is available from our World Wide Web site. Literature Cited

1. Jacobsen, J. J.; Moore, J. W. Chemistry Comes Alive! Vol. 1; J. Chem. Educ. Software 1998, SP 18.
2. Jacobsen, J. J.; Moore, J. W. Chemistry Comes Alive! Vol. 2; J. Chem. Educ. Software 1998, SP 21.
3. Jacobsen, J. J.; Moore, J. W. Chemistry Comes Alive! Vol. 3; J. Chem. Educ. Software 2000, SP 23.
4. Banks, A. J.; Holmes, J. L.; Jacobsen, J. J.; Kotz, J. C.; Moore, J. W.; Robinson, W. R.; Schatz, P. F.; Tweedale, J.; Young, S. Periodic Table Live! 2nd Edition; J. Chem. Educ. Software 1999, SP17.

Coupled effects of solution chemistry and hydrodynamics on the mobility and transport of quantum dot nanomaterials in the Vadose Zone

USDA-ARS?s Scientific Manuscript database

To investigate the coupled effects of solution chemistry and vadose zone processes on the mobility of quantum dot (QD) nanoparticles, laboratory scale transport experiments were performed. The complex coupled effects of ionic strength, size of QD aggregates, surface tension, contact angle, infiltrat...

Nobody’s perfect: can irregularities in pit structure influence vulnerability to cavitation?

PubMed Central

Plavcová, Lenka; Jansen, Steven; Klepsch, Matthias; Hacke, Uwe G.

2013-01-01

Recent studies have suggested that species-specific pit properties such as pit membrane thickness, pit membrane porosity, torus-to-aperture diameter ratio and pit chamber depth influence xylem vulnerability to cavitation. Despite the indisputable importance of using mean pit characteristics, considerable variability in pit structure within a single species or even within a single pit field should be acknowledged. According to the rare pit hypothesis, a single pit that is more air-permeable than many neighboring pits is sufficient to allow air-seeding. Therefore, any irregularities or morphological abnormalities in pit structure allowing air-seeding should be associated with increased vulnerability to cavitation. Considering the currently proposed models of air-seeding, pit features such as rare, large pores in the pit membrane, torus extensions, and plasmodesmatal pores in a torus can represent potential glitches. These aberrations in pit structure could either result from inherent developmental flaws, or from damage caused to the pit membrane by chemical and physical agents. This suggests the existence of interesting feedbacks between abiotic and biotic stresses in xylem physiology. PMID:24273549

Corrosion behavior of austenitic alloy 690 under anodic and cathodic potentials

NASA Astrophysics Data System (ADS)

Dutta, R. S.; Dey, G. K.; Lobo, A.; Purandare, R.; Kulkarni, S. K.

2002-05-01

The corrosion behavior of austenitic alloy 690 in a solution-annealed condition has been evaluated with the application of anodic as well as cathodic potentials in an acidic chloride solution at room temperature (RT). In a 0.5M H2SO4 + 0.5M NaCl solution, the alloy displayed active-passive pitting behavior with the application of an anodic potential. Surface films, formed at the onset and later stage of the passive region, were characterized using X-ray photoelectron spectroscopy (XPS). The XPS revealed that the surface film formed at the onset of passivity (+ 100 mV SCE) consisted of Cr(OH)3, without any Fe+3/Fe+2. The presence of nickel in the film was found in a transition state of Ni+2 and Ni0. The passive film formed at the higher anodic potential (+ 700 mV SCE) consisted of Cr2O3 without any Fe+3/Fe+2 or even Ni+2/Ni0. Microscopic studies of alloy 690 after anodic polarization in an acidic chloride solution revealed pitting, which was found to be initiated at large, faceted TiN-type inclusions. The susceptibility of the alloy to hydrogen embrittlement has been investigated by conducting cathodic charging of the tensile samples in a 0.5M H2SO4 solution at RT and by subsequent tensile testing of the charged samples in air at a strain rate of 1.3 × 10-4 s-1 up to fracture. An indication toward hydrogen-induced ductility loss was noticed for the samples of the alloy, which is believed to be attributable to a hydrogen-enhanced microvoid growth process. Since the microvoid growth process occurs at the last stage of fracture, the effect of hydrogen on the ductility of the alloy is little.

Corrosion resistance of a new AL 6013-20 SiC(P) in salt spray chamber

NASA Astrophysics Data System (ADS)

Ahmad, Zaki; Aleem, B. J. Abdul

2000-06-01

Aluminum 6013 alloy (0.82Si, 0.95Mg, and 0.35Mn) is finding increasing usage in new aircraft designs, automotives, and structural applications due to its good stretch forming character in T4 temper (solution heat treated and naturally aged to a substantially stable conditions) compared to alloy 2024 (4.4Cu, 0.6Mn, 1.5Mg, and balance Al) and Al6061 (Si0.51 to 0.71, Fe0.35, Cu0.15, Mn0.85, Mg0.15, 0.25Cr, 0.15Zn, and balanced Al). The newly developed A1 6013 reinforced with 20 vol.% SiC(P) has a higher strength than its unreinforced counterpart. Whereas the corrosion behavior of A1 6013 has been reported in literature, there is no previous data on A1 6013 reinforced with SiC(P). A knowledge of the corrosion behavior of this alloy is crucial to its applications in aerospace, structural, and automotive industry. The first results of corrosion study of this alloy in 3.5 wt.% Na Cl in a salt spray chamber are presented. Three tempers F (as fabricated), O (annealed), and T4 (age hardened and stabilized at room temperature) of the alloy A1 6013-30 SiC(P) were exposed to environmental chamber in accordance with ASTM recommended practice. The corrosion rate of the alloy showed a decrease with increased exposure period and after 800 h of exposure no appreciable change in the rate of corrosion was observed. The lowest rate of corrosion (4.83 mdd) was shown by temper T4 followed by tempers F and O after 1200 h of exposure in the increasing order of corrosion rate. Fluctuations in the corrosion rate with time are related to the kinetics of growth and dissolution of Al(OH)3 film, which was detected by fourier transformation infrared (FTIR) spectroscopy (FTIS). The film was composed of an inner compact layer and outer bulk layer dependent on the refreshment rate from the bulk solution. Micrograph examination by scanning electron microscopy (SEM) showed the presence of pits covered by aluminum hydroxide gel, which isolates the pit from the bulk solution. The acidic conditions of pits also cause intergranular attack. Pitting was observed to be less pronounced in temper T4 compared to F and O tempers, the former also showing the highest resistance to corrosion. The data generated predict promising application potential of this alloy in environment where resistance to corrosion is also a major consideration.

Detection of parathion pesticide by quartz crystal microbalance functionalized with UV-activated antibodies.

PubMed

Funari, Riccardo; Della Ventura, Bartolomeo; Schiavo, Luigi; Esposito, Rosario; Altucci, Carlo; Velotta, Raffaele

2013-07-02

Photonic immobilization technique (PIT) has been used to develop an immunosensor for the detection of parathion. An antibody solution has been activated by breaking the disulfide bridge in the triad Trp/Cys-Cys through absorption of ultrashort UV laser pulses. The free thiol groups so produced interact with gold lamina making the antibody oriented upside, that is, with its variable parts exposed to the environment, thereby greatly increasing the detection efficiency. PIT has been applied to anchor polyclonal antiparathion antibodies to the gold electrode of a Quartz Crystal Microbalance (QCM) giving rise to very high detection sensitivity once the parathion is made heavier by complexion with BSA (bovine serum albumin), this latter step only required by the mass based transducer used in this case. The comparison of the sensor response with irradiated antibodies against different analytes shows that the high degree of antibody specificity is not affected by PIT nor is it by the complexion of parathion with BSA. These results pave the way to important applications in biosensing, since the widespread occurrence of the Trp/Cys-Cys residues triads in proteins make our procedure very general and effective to detect light analytes.

Toward Edge-Defined Holey Boron Nitride Nanosheets

NASA Technical Reports Server (NTRS)

Lin, Yi; Liao, Yunlong; Chen, Zhongfan; Connell, John W.

2015-01-01

"Holey" two-dimensional (2D) nanosheets with well-defined holy morphology and edge chemistry are highly desirable for applications such as energy storage, catalysis, sensing, transistors, and molecular transport/separation. For example, holey grapheme is currently under extensive investigation for energy storage applications because of the improvement in ion transport due to through the thickness pathways provided by the holes. Without the holes, the 2D materials have significant limitations for such applications in which efficient ion transport is important. As part of an effort to apply this approach to other 2D nanomaterials, a method to etch geometrically defined pits or holes on the basal plane surface of hexagonal boron nitride (h-BN) nanosheets has been developed. The etching, conducted via heating in ambient air using metal nanoparticles as catalysts, was facile, controllable, and scalable. Starting h-BN layered crystals were etched and subsequently exfoliated into boron nitride nanosheets (BNNSs). The as-etched and exfoliated h-BN nanosheets possessed defined pit and hole shapes that were comprised of regulated nanostructures at the edges. The current finding are the first step toward the bulk preparation of holey BNNSs with defined holes and edges.

Communities of Molecules: A Physical Chemistry Module.

ERIC Educational Resources Information Center

DeVoe, Howard

This book is one in the series of Interdisciplinary Approaches to Chemistry (IAC) designed to help students discover that chemistry is a lively science and actively used to pursue solutions to the important problems of today. It is expected for students to see how chemistry takes place continuously all around and to readily understand the daily…

Diversity and Periodicity: An Inorganic Chemistry Module.

ERIC Educational Resources Information Center

Huheey, James

This book is one in a series of Interdisciplinary Approaches to Chemistry (IAC) designed to help students discover that chemistry is a lively science and actively used to pursue solutions to the important problems of today. It is expected for students to see how chemistry takes place continuously all around and to readily understand the daily…

Form and Function: An Organic Chemistry Module.

ERIC Educational Resources Information Center

Jarvis, Bruce; Mazzocchi, Paul

This book is one in the series of Interdisciplinary Approaches to Chemistry (IAC) designed to help students discover that chemistry is a lively science and actively used to pursue solutions to the important problems of today. It is expected for students to see how chemistry takes place continuously all around and to readily understand the daily…

A field demonstration of the microbial treatment of sour produced water

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

Sublette, K.L.; Morse, D.; Raterman, K.

1995-12-31

The potential for detoxification and deodorization of sulfide-laden water (sour water) by microbial treatment was evaluated at a petroleum production site under field conditions. A sulfide-tolerant strain of the chemautotroph and facultative anaerobe, Thiobacillus denitrificans, was introduced into an oil-skimming pit of the Amoco Production Company LACT 10 Unit of the Salt Creek Field, Wyoming. Field-produced water enters this pit from the oil/water separation treatment train at an average flowrate of 5,000 bbl/D (795 m{sup 3}/D) with a potential maximum of 98,000 bbl/D (15,580 m{sup 3}/D). Water conditions at the pit inlet are 4,800 mg/l TDS, 100 mg/l sulfide, pHmore » 7.8, and 107{degrees}F. To this water an aqueous solution of ammonium nitrate and diphosphorous pentoxide was added to provide required nutrients for the bacteria. The first 20% of the pit was aerated to a maximum depth of 5 ft (1.5 m) to facilitate the aerobic oxidation of sulfide. No provisions for pH control or biomass recovery and recycle were made. Pilot operations were initiated in October 1992 with the inoculation of the 19,000 bbl (3,020 m{sup 3}) pit with 40 lb (18.1 kg) of dry weight biomass. After a brief acclimation period, a nearly constant mass flux of 175 lb/D (80 kg/D) sulfide was established to the pit. Bio-oxidation of sulfide to elemental sulfur and sulfate was immediate and complete. Subsequent pilot operations focused upon process optimization and process sensitivity to system upsets. The process appeared most sensitive to large variations in sulfide loading due to maximum water discharge events. However, recoveries from such events could be accomplished within hours. This paper details all pertinent aspects of pilot operation, performance, and economics. Based on this body of evidence, it is suggested that the oxidation of inorganic sulfides by T denitrificans represents a viable concept for the treatment of sour water coproduced with oil and gas.« less

Game Theory Analysis of Bidding for A Construction Contract

NASA Astrophysics Data System (ADS)

Kembłowski, Marian W.; Grzyl, Beata; Siemaszko, Agata

2017-10-01

The authors are concerned with a bidding problem. There are two companies (P1 and P2) bidding for a highway construction project. In order to be more competitive, P1 considers buying a new gravel pit near the construction site. The basic cost of the pit is known to both companies. However, there is also an additional, hidden, cost (C) known only to P1. P2 is uncertain whether the hidden cost is C = 0 or C = x. P1 plans to bid for the job, but has to decide whether to buy the gravel pit. P2, not having a complete knowledge about C, thus not knowing the strategy choice of P1, has to decide if to bid for the job. In effect we have two payoff matrices, one for the additional cost C = 0, and the other one for C = x. If the probability of P2 bidding for the project can be estimated by propagating intelligence information through a Bayesian Belief Network, the best strategy for P1 can be readily determined. Otherwise, the solution calls for changing this game of incomplete information (players may or may not know some information about the other players, e.g., their “type,” their strategies, payoffs) into a game of imperfect information (players are simply unaware of the actions chosen by other players). This is achieved by introducing an additional “Nature” node which for this problem determines with some probability “p” the additional cost C= 0 (thus, C = x with probability 1-p). The solution of this game turns out to depend on the probability “p”. For some values of p the game is solved with pure strategies, whereas for other values the game is in equilibrium when the players randomly mix their strategies.

Ellipsometric measurements on the passive film prior to the initiation of breakdown in aluminum

NASA Technical Reports Server (NTRS)

Yahalom, J.; Kruger, J.; Mcbee, C. L.

1971-01-01

The presence of chlorides in aqueous solutions causes pitting attack or stress corrosion cracking in many metals if the oxidation potential is high enough. Results are presented of a series of experiments carried out on 99.99% pure aluminum to determine changes that occur in the ellipsometric parameter of the passive film during incubation period.

Tank Inspection NDE Results for Fiscal Year 2014, Waste Tanks 26, 27, 28 and 33

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

Elder, J.; Vandekamp, R.

2014-09-29

Ultrasonic nondestructive examinations (NDE) were performed on waste storage tanks 26, 27, 28 and 33 at the Savannah River Site as a part of the “In-Service Inspection (ISI) Program for High Level Waste Tanks.” No reportable conditions were identified during these inspections. The results indicate that the implemented corrosion control program continues to effectively mitigate corrosion in the SRS waste tanks. Ultrasonic inspection (UT) is used to detect general wall thinning, pitting and interface attack, as well as vertically oriented cracks through inspection of an 8.5 inch wide strip extending over the accessible height of the primary tank wall andmore » accessible knuckle regions. Welds were also inspected in tanks 27, 28 and 33 with no reportable indications. In a Type III/IIIA primary tank, a complete vertical strip includes scans of five plates (including knuckles) so five “plate/strips” would be completed at each vertical strip location. In FY 2014, a combined total of 79 plate/strips were examined for thickness mapping and crack detection, equating to over 45,000 square inches of area inspected on the primary tank wall. Of the 79 plate/strips examined in FY 2014 all but three have average thicknesses that remain at or above the construction minimum thickness which is nominal thickness minus 0.010 inches. There were no service induced reportable thicknesses or cracking encountered. A total of 2 pits were documented in 2014 with the deepest being 0.032 inches deep. One pit was detected in Tank 27 and one in Tank 33. No pitting was identified in Tanks 26 or 28. The maximum depth of any pit encountered in FY 2014 is 5% of nominal thickness, which is less than the minimum reportable criteria of 25% through-wall for pitting. In Tank 26 two vertical strips were inspected, as required by the ISI Program, due to tank conditions being outside normal chemistry controls for more than 3 months. Tank 28 had an area of localized thinning on the exterior wall of the secondary tank noted during the initial inspections in 2005. That area was inspected again in 2014 and found to be larger and slightly deeper. The deepest area of thinning in the secondary wall is less than 20% wall loss. The maximum length of thinning is less than 24 inches and does not impact structural or leak integrity per WSRC-TR-2002-00063. Inspection results were presented to the In-service Inspection Review Committee (ISIRC) where it was determined that no additional data was required to complete these inspections.« less

Ascorbic Acid as a Standard for Iodometric Titrations. An Analytical Experiment for General Chemistry

NASA Astrophysics Data System (ADS)

Silva, Cesar R.; Simoni, Jose A.; Collins, Carol H.; Volpe, Pedro L. O.

1999-10-01

Ascorbic acid is suggested as the weighable compound for the standardization of iodine solutions in an analytical experiment in general chemistry. The experiment involves an iodometric titration in which iodine reacts with ascorbic acid, oxidizing it to dehydroascorbic acid. The redox titration endpoint is determined by the first iodine excess that is complexed with starch, giving a deep blue-violet color. The results of the titration of iodine solution using ascorbic acid as a calibration standard were compared with the results acquired by the classic method using a standardized solution of sodium thiosulfate. The standardization of the iodine solution using ascorbic acid was accurate and precise, with the advantages of saving time and avoiding mistakes due to solution preparation. The colorless ascorbic acid solution gives a very clear and sharp titration end point with starch. It was shown by thermogravimetric analysis that ascorbic acid can be dried at 393 K for 2 h without decomposition. This experiment allows general chemistry students to perform an iodometric titration during a single laboratory period, determining with precision the content of vitamin C in pharmaceutical formulations.

Flame Emission Spectrometry in General Chemistry Labs: Solubility Product (K[subscript sp]) of Potassium Hydrogen Phthalate

ERIC Educational Resources Information Center

Nyasulu, Frazier W.; Cusworth, William, III; Lindquist, David; Mackin, John

2007-01-01

In this general chemistry laboratory, flame emission spectrometry is used to determine the potassium ion concentration in saturated solutions of potassium hydrogen phthalate (KHP) in the 0-65 [degree]C temperature range. From these data the solubility products (K[subscript sp]), the Gibbs free energies of solution ([Delta][subscript…

A Study of First-Year Chemistry Students' Understanding of Solution Concentration at the Tertiary Level

ERIC Educational Resources Information Center

de Berg, Kevin

2012-01-01

This paper reports on students' understanding of sugar concentration in aqueous solutions presented in two different modes: a visual submicroscopic mode for particles and a verbal mode referring to macroscopic amounts of sugar. One hundred and forty-five tertiary college students studying some form of first-year chemistry participated in the…

Enhancing Pre-Service Elementary Teachers' Conceptual Understanding of Solution Chemistry with Conceptual Change Text

ERIC Educational Resources Information Center

Calik, Muammer; Ayas, Alipasa; Coll, Richard Kevin

2007-01-01

This paper reports on the use of a constructivist-based pedagogy to enhance understanding of some features of solution chemistry. Pre-service science teacher trainees' prior knowledge about the dissolution of salts and sugar in water were elicited by the use of a simple diagnostic tool. The test revealed widespread alternative conceptions. These…

The Study Of Soil And Agrochemical Features Of Zonal Soils Of Coal Mining Enterprises In Kemerovo Region

NASA Astrophysics Data System (ADS)

Yakovchenko, M. A.; Kosolapova, A. A.; Ermolaev, V. A.

2017-01-01

The paper represents the results of the study of soil and agrochemical features of zonal soils: the grain-size composition, the content of humus, phosphorus and potassium, and heavy metals, the reaction of soil solution of the territory of the open-pit coal mine No12 of Kemerovo region in the areas of the working enterprise. The species composition of the lignose and herbaceous vegetation of the undisturbed territories has been studied. It has been revealed that the fertile soil layer of the studied areas of the open-pit coal mine is characterized as fertile but can’t be removed and stored because the surface of the whole area under study is forest-covered very much, rumpled, there are gullies and a lot of wind-fallen trees.

Investigating the Effectiveness of Teaching Methods Based on a Four-Step Constructivist Strategy

NASA Astrophysics Data System (ADS)

Çalik, Muammer; Ayas, Alipaşa; Coll, Richard K.

2010-02-01

This paper reports on an investigation of the effectiveness an intervention using several different methods for teaching solution chemistry. The teaching strategy comprised a four-step approach derived from a constructivist view of learning. A sample consisting of 44 students (18 boys and 26 girls) was selected purposively from two different Grade 9 classes in the city of Trabzon, Turkey. Data collection employed a purpose-designed `solution chemistry concept test', consisting of 17 items, with the quantitative data from the survey supported by qualitative interview data. The findings suggest that using different methods embedded within the four-step constructivist-based teaching strategy enables students to refute some alternative conceptions, but does not completely eliminate student alternative conceptions for solution chemistry.

The Heart of Matter: A Nuclear Chemistry Module.

ERIC Educational Resources Information Center

Viola, Vic

This book is one in a series of Interdisciplinary Approaches to Chemistry (IAC) designed to help students discover that chemistry is a lively science and actively used to pursue solutions to the important problems of today. It is expected for students to see how chemistry takes place continuously all around and to readily understand the daily…

Healdsburgite - a New Tektite and Associated Tektite Strewnfield in North Central California

NASA Astrophysics Data System (ADS)

Erickson, R. C.; Deino, A. L.; Norwick, S. A.; Byrd, C.

2012-12-01

Erickson, Rolfe; Norwick, Steven; and Byrd, Caitlin, Sonoma State University; Deino, Alan, Berkeley Geochronology Center. I A Distinctive Glass Clast Population In numerous locations in Sonoma and Solano Counties in north central California, over an area of ~ 200 km2, distinctive ~ 1-5 cm dominantly ovoid glass clasts are found as part of the pebble population in young sediments. They are composed of black massive aphyric nonvesicular glass whose surfaces are totally covered with a texture of adjoining small deep pits and grooves. The pits are hemispherical, 1-10 mm across, and join at sharp edges composed of straight segments. The grooves, where present, are the width and depth of the pits and may be up to several cm long and vermicular. Some clasts have internal layering resembling flow textures. These glass objects were brought to our attention by a local resident, Ms. Diane Moore, about 20 years ago. Four of these glass clasts from widely separated locations in the exposure area have been dated by the laser incremental-heating Ar39/Ar40 method at the Berkeley Geochronology Center, with an age of ~ 2.81 Ma (upper Pliocene). The four samples have mutually overlapping ages at one sigma. Chemical analyses of the 10 major and 50 minor elements, of four widely separated clasts, were obtained at commercial laboratories. The clasts are all rhyolites and cluster tightly on the TAS diagram of Le Maitre et al (2002). All available data show that all these pitted and grooved clasts are part of a single population. II. The Clasts are Tektites We believe these distinctive glass clasts to be tektites for the following reasons: 1. Pits are always present and wholly cover the clast surface. Perhaps half the clasts also have distinctive irregular vermicular grooves superimposed on the pitted surface. This surface pattern is like those on other long-recognized 'classic' tektites, like indochinites. The clasts look like tektites; compare McCall (2001, Figure 2.30) for example. 2. The clasts show no significant weathering. Once cleaned of adhering sediment, they are solid and vitreous. There are also no cases of partial development of the distinctive surface texture, as might be expected if it were a consequence of in situ weathering. 3. The clasts do not have a detrital origin; they are not obsidian pebbles. The pit and groove pattern, which is uniformly well developed on clasts throughout the distribution area, is fragile and could not have survived much transport. 4. The clasts are not volcanic in origin (i.e., 'apache tears'). The pit and groove pattern contrasts with the relatively smooth surface of apache tears, and the clasts bear no resemblance to lapilli. Their distinctive appearance and uniform age and chemistry suggests that these objects are tektites in a strewnfield, only a small part of which has been identified to date. No related impact site has been identified, but clast composition suggests a continental target. We suggest these clasts, heretofore informally called Healdsburg glass, be recognized as tektites and called healdsburgites, in the manner of other tektites. A public domain PDF format copy of this poster will be available for download in the digital archive in the Sonoma State University library.

Corrosion resistance of cast irons and titanium alloys as reference engineered metal barriers for use in basalt geologic storage: a literature assessment

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

Charlot, L.A.; Westerman, R.E.

A survey and assessment of the literature on the corrosion resistance of cast irons and low-alloy titanium are presented. Selected engineering properties of cast iron and titanium are briefly described; however, the corrosion resistance of cast iron and titanium in aqueous solutions or in soils and their use in a basalt repository are emphasized. In evaluating the potential use of cast iron and titanium as structural barrier materials for long-lived nuclear waste packages, it is assumed that titanium has the general corrosion resistance to be used in relatively thin cross sections whereas the cost and availability of cast iron allowsmore » its use even in very thick cross sections. Based on this assumption, the survey showed that: The uniform corrosion of low-alloy titanium in a basalt environment is expected to be extremely low. A linear extrapolation of general corrosion rates with an added corrosion allowance suggests that a 3.2- to 6.4-mm-thick wall may have a life of 1000 yr. Pitting and crevice corrosion are not likely corrosion modes in basalt ground waters. It is also unlikely that stress corrosion cracking (SCC) will occur in the commercially pure (CP) titanium alloy or in palladiumor molybdenum-alloyed titanium materials. Low-alloy cast irons may be used as barrier metals if the environment surrounding the metal keeps the alloy in the passive range. The solubility of the corrosion product and the semipermeable nature of the oxide film allow significant uniform corrosion over long time periods. A linear extrapolation of high-temperature corrosion rates on carbon steels and corrosion rates of cast irons in soils gives an estimated metal penetration of 51 to 64 mm after 1000 yr. A corrosion allowance of 3 to 5 times that suggests that an acceptable cast iron wall may be from 178 to 305 mm thick. Although they cannot be fully assessed, pitting and crevice corrosion should not affect cast iron due to the ground-water chemistry of basalt.« less

Nucleation sites of Ge nanoislands grown on pit-patterned Si substrate prepared by electron-beam lithography

NASA Astrophysics Data System (ADS)

Smagina, Zh. V.; Zinovyev, V. A.; Rudin, S. A.; Novikov, P. L.; Rodyakina, E. E.; Dvurechenskii, A. V.

2018-04-01

Regular pit-patterned Si(001) substrates were prepared by electron-beam lithography followed by plasma chemical etching. The geometry of the pits was controlled by varying the etching conditions and the electron-beam exposure duration. It was shown that the location of three-dimensional (3D) Ge nanoislands subsequently grown on the pit-patterned Si substrates depends on the shape of the pit bottom. In the case of pits having a sharp bottom, 3D Ge islands nucleate inside the pits. For pits with a wide flat bottom, the 3D Ge island nucleation takes place at the pit periphery. This effect is attributed to the strain relaxation depending not only on the initial pit shape, but also on its evolution during the Ge wetting layer deposition. It was shown by Monte Carlo simulations that in the case of a pit with a pointed bottom, the relaxation is most effective inside the pit, while for a pit with a wide bottom, the most relaxed area migrates during Ge deposition from the pit bottom to its edges, where 3D Ge islands nucleate.

Computations of ideal and real gas high altitude plume flows

NASA Technical Reports Server (NTRS)

Feiereisen, William J.; Venkatapathy, Ethiraj

1988-01-01

In the present work, complete flow fields around generic space vehicles in supersonic and hypersonic flight regimes are studied numerically. Numerical simulation is performed with a flux-split, time asymptotic viscous flow solver that incorporates a generalized equilibrium chemistry model. Solutions to generic problems at various altitude and flight conditions show the complexity of the flow, the equilibrium chemical dissociation and its effect on the overall flow field. Viscous ideal gas solutions are compared against equilibrium gas solutions to illustrate the effect of equilibrium chemistry. Improved solution accuracy is achieved through adaptive grid refinement.

Martian Central Pit Craters

NASA Technical Reports Server (NTRS)

Hillman, E.; Barlow, N. G.

2005-01-01

Impact craters containing central pits are rare on the terrestrial planets but common on icy bodies. Mars is the exception among the terrestrial planets, where central pits are seen on crater floors ( floor pits ) as well as on top of central peaks ( summit pits ). Wood et al. [1] proposed that degassing of subsurface volatiles during crater formation produced central pits. Croft [2] argued instead that central pits might form during the impact of volatile-rich comets. Although central pits are seen in impact craters on icy moons such as Ganymede, they do show some significant differences from their martian counterparts: (a) only floor pits are seen on Ganymede, and (b) central pits begin to occur at crater diameters where the peak ring interior morphology begins to appear in terrestrial planet craters [3]. A study of craters containing central pits was conducted by Barlow and Bradley [4] using Viking imagery. They found that 28% of craters displaying an interior morphology on Mars contain central pits. Diameters of craters containing central pits ranged from 16 to 64 km. Barlow and Bradley noted that summit pit craters tended to be smaller than craters containing floor pits. They also noted a correlation of central pit craters with the proposed rings of large impact basins. They argued that basin ring formation fractured the martian crust and allowed subsurface volatiles to concentrate in these locations. They favored the model that degassing of the substrate during crater formation was responsible for central pit formation due to the preferential location of central pit craters along these basin rings.

Mapping of the minimal inorganic phosphate transporting unit of human PiT2 suggests a structure universal to PiT-related proteins from all kingdoms of life

PubMed Central

2011-01-01

Background The inorganic (Pi) phosphate transporter (PiT) family comprises known and putative Na+- or H+-dependent Pi-transporting proteins with representatives from all kingdoms. The mammalian members are placed in the outer cell membranes and suggested to supply cells with Pi to maintain house-keeping functions. Alignment of protein sequences representing PiT family members from all kingdoms reveals the presence of conserved amino acids and that bacterial phosphate permeases and putative phosphate permeases from archaea lack substantial parts of the protein sequence when compared to the mammalian PiT family members. Besides being Na+-dependent Pi (NaPi) transporters, the mammalian PiT paralogs, PiT1 and PiT2, also are receptors for gamma-retroviruses. We have here exploited the dual-function of PiT1 and PiT2 to study the structure-function relationship of PiT proteins. Results We show that the human PiT2 histidine, H502, and the human PiT1 glutamate, E70, - both conserved in eukaryotic PiT family members - are critical for Pi transport function. Noticeably, human PiT2 H502 is located in the C-terminal PiT family signature sequence, and human PiT1 E70 is located in ProDom domains characteristic for all PiT family members. A human PiT2 truncation mutant, which consists of the predicted 10 transmembrane (TM) domain backbone without a large intracellular domain (human PiT2ΔR254-V483), was found to be a fully functional Pi transporter. Further truncation of the human PiT2 protein by additional removal of two predicted TM domains together with the large intracellular domain created a mutant that resembles a bacterial phosphate permease and an archaeal putative phosphate permease. This human PiT2 truncation mutant (human PiT2ΔL183-V483) did also support Pi transport albeit at very low levels. Conclusions The results suggest that the overall structure of the Pi-transporting unit of the PiT family proteins has remained unchanged during evolution. Moreover, in combination, our studies of the gene structure of the human PiT1 and PiT2 genes (SLC20A1 and SLC20A2, respectively) and alignment of protein sequences of PiT family members from all kingdoms, along with the studies of the dual functions of the human PiT paralogs show that these proteins are excellent as models for studying the evolution of a protein's structure-function relationship. PMID:21586110

Mapping of the minimal inorganic phosphate transporting unit of human PiT2 suggests a structure universal to PiT-related proteins from all kingdoms of life.

PubMed

Bøttger, Pernille; Pedersen, Lene

2011-05-17

The inorganic (Pi) phosphate transporter (PiT) family comprises known and putative Na(+)- or H(+)-dependent Pi-transporting proteins with representatives from all kingdoms. The mammalian members are placed in the outer cell membranes and suggested to supply cells with Pi to maintain house-keeping functions. Alignment of protein sequences representing PiT family members from all kingdoms reveals the presence of conserved amino acids and that bacterial phosphate permeases and putative phosphate permeases from archaea lack substantial parts of the protein sequence when compared to the mammalian PiT family members. Besides being Na(+)-dependent P(i) (NaP(i)) transporters, the mammalian PiT paralogs, PiT1 and PiT2, also are receptors for gamma-retroviruses. We have here exploited the dual-function of PiT1 and PiT2 to study the structure-function relationship of PiT proteins. We show that the human PiT2 histidine, H(502), and the human PiT1 glutamate, E(70),--both conserved in eukaryotic PiT family members--are critical for P(i) transport function. Noticeably, human PiT2 H(502) is located in the C-terminal PiT family signature sequence, and human PiT1 E(70) is located in ProDom domains characteristic for all PiT family members.A human PiT2 truncation mutant, which consists of the predicted 10 transmembrane (TM) domain backbone without a large intracellular domain (human PiT2ΔR(254)-V(483)), was found to be a fully functional P(i) transporter. Further truncation of the human PiT2 protein by additional removal of two predicted TM domains together with the large intracellular domain created a mutant that resembles a bacterial phosphate permease and an archaeal putative phosphate permease. This human PiT2 truncation mutant (human PiT2ΔL(183)-V(483)) did also support P(i) transport albeit at very low levels. The results suggest that the overall structure of the P(i)-transporting unit of the PiT family proteins has remained unchanged during evolution. Moreover, in combination, our studies of the gene structure of the human PiT1 and PiT2 genes (SLC20A1 and SLC20A2, respectively) and alignment of protein sequences of PiT family members from all kingdoms, along with the studies of the dual functions of the human PiT paralogs show that these proteins are excellent as models for studying the evolution of a protein's structure-function relationship. © 2011 Bøttger and Pedersen; licensee BioMed Central Ltd.

Assessment of factors limiting algal growth in acidic pit lakes--a case study from Western Australia, Australia.

PubMed

Kumar, R Naresh; McCullough, Clint D; Lund, Mark A; Larranaga, Santiago A

2016-03-01

Open-cut mining operations can form pit lakes on mine closure. These new water bodies typically have low nutrient concentrations and may have acidic and metal-contaminated waters from acid mine drainage (AMD) causing low algal biomass and algal biodiversity. A preliminary study was carried out on an acidic coal pit lake, Lake Kepwari, in Western Australia to determine which factors limited algal biomass. Water quality was monitored to obtain baseline data. pH ranged between 3.7 and 4.1, and solute concentrations were slightly elevated to levels of brackish water. Concentrations of N were highly relative to natural lakes, although concentrations of FRP (<0.01 mg/L) and C (total C 0.7-3.7 and DOC 0.7-3.5 mg/L) were very low, and as a result, algal growth was also extremely low. Microcosm experiment was conducted to test the hypothesis that nutrient enrichment will be able to stimulate algal growth regardless of water quality. Microcosms of Lake Kepwari water were amended with N, P and C nutrients with and without sediment. Nutrient amendments under microcosm conditions could not show any significant phytoplankton growth but was able to promote benthic algal growth. P amendments without sediment showed a statistically higher mean algal biomass concentration than controls or microcosms amended with phosphorus but with sediment did. Results indicated that algal biomass in acidic pit lake (Lake Kepwari) may be limited primarily by low nutrient concentrations (especially phosphorus) and not by low pH or elevated metal concentrations. Furthermore, sediment processes may also reduce the nutrient availability.

PROCEEDINGS OF THE PROTACTINIUM CHEMISTRY SYMPOSIUM, GATLINBURG, TENNESSEE, APRIL 25-26, 1963

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

None

1963-04-26

Eleven papers are presented on the chemistry of protactinium. Most of the emphasis is on solvent extraction and solution chemistry. Separate abstracts were prepared for ten of the papers; the remaining paper was previously abstracted in NSA. (D.L.C.)

Pretreatment of lignocellulosic biomass using Fenton chemistry

USDA-ARS?s Scientific Manuscript database

Pretreatment is a necessary step in “biomass to biofuel conversion” due to the recalcitrant nature of lignocellulosic biomass. White-rot fungi utilize peroxidases and hydrogen peroxide (in vivo Fenton chemistry) to degrade lignin. In an attempt to mimic this process, solution phase Fenton chemistry ...

GROUNDWATER MASS TRANSPORT AND EQUILIBRIUM CHEMISTRY MODEL FOR MULTICOMPONENT SYSTEMS

EPA Science Inventory

A mass transport model, TRANQL, for a multicomponent solution system has been developed. The equilibrium interaction chemistry is posed independently of the mass transport equations which leads to a set of algebraic equations for the chemistry coupled to a set of differential equ...

Transport of E. coli D21g with runoff water under different solution chemistry conditions and surface slopes

USDA-ARS?s Scientific Manuscript database

Tracer and indicator microbe runoff experiments were conducted to investigate the influence of solution chemistry on the transport, retention, and release of Escherichia coli D21g. Experiments were conducted in a chamber (2.25 m long, 0.15 m wide, and 0.16 m high) packed with ultrapure quartz sand (...

Challenges Faced by Pre-Service Chemistry Teachers Teaching in a Laboratory and Their Solution Proposals

ERIC Educational Resources Information Center

Yalcin-Celik, Ayse; Kadayifci, Hakki; Uner, Sinem; Turan-Oluk, Nurcan

2017-01-01

This study examines the challenges faced by pre-service chemistry teachers teaching in a laboratory and their proposed solutions to these challenges. The study was conducted in a 13-week-long methodology course. Written statements from participants and observations from researchers were used as data sources. From these data, it was found that the…

Role of Precursor-Conversion Chemistry in the Crystal-Phase Control of Catalytically Grown Colloidal Semiconductor Quantum Wires.

PubMed

Wang, Fudong; Buhro, William E

2017-12-26

Crystal-phase control is one of the most challenging problems in nanowire growth. We demonstrate that, in the solution-phase catalyzed growth of colloidal cadmium telluride (CdTe) quantum wires (QWs), the crystal phase can be controlled by manipulating the reaction chemistry of the Cd precursors and tri-n-octylphosphine telluride (TOPTe) to favor the production of either a CdTe solute or Te, which consequently determines the composition and (liquid or solid) state of the Bi x Cd y Te z catalyst nanoparticles. Growth of single-phase (e.g., wurtzite) QWs is achieved only from solid catalysts (y ≪ z) that enable the solution-solid-solid growth of the QWs, whereas the liquid catalysts (y ≈ z) fulfill the solution-liquid-solid growth of the polytypic QWs. Factors that affect the precursor-conversion chemistry are systematically accounted for, which are correlated with a kinetic study of the composition and state of the catalyst nanoparticles to understand the mechanism. This work reveals the role of the precursor-reaction chemistry in the crystal-phase control of catalytically grown colloidal QWs, opening the possibility of growing phase-pure QWs of other compositions.

Geologic setting of the Snake Pit hydrothermal site: An active vent field on the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Karson, Jeffrey A.; Brown, Jennifer R.

1988-03-01

The Snake Pit Hydrothermal Site lies on the axis of the Mid-Atlantic Ridge at 23°22' N latitude, about 30 km south of the Kane Transform Intersection. Active ‘black smoker’ vents and a surrounding field of hydrothermal sediment occur at the crest of a laterally extensive neovolcanic ridge. It is one of the first active hydrothermal vent fields to be found on a slow-spreading ridge axis and despite significant differences in its geologic setting from those of the East Pacific Rise, has many similarities to its fast-spreading counterparts. Although preliminary reports have documented many interesting aspects of these vents and their surroundings, new data collected from the manned submersible ALVIN and the deep-towed ANGUS camera system define the regional tectonic setting as well as the local geologic environment of this fascinating area. The Snake Pit vents are located on a local peak of a volcanic constructional ridge at a depth of 3450 m, 700 800 m deeper than vents known from the East Pacific Rise, Galapagos, or Juan de Fuca spreading centers. The vent field is at least 600 m long and up to 200 m wide and is covered by a thick blanket of greenish to yellow-orange hydrothermal sediment. Both active and extinct vents are perched along the crests of steep-sided sulfide mounds that reach heights of over 40 m. High-temperature (350° C) fluids are vented from black smoker chimneys and low-temperature (226° C) fluids seep from sulphide domes and subordinate anhydrite constructions. Water temperatures, flow rates, fluid chemistries, and mineralization are strikingly similar to vents of faster spreading ridge crests; however, a somewhat distinct fauna inhabit the area.

Biomineralization of copper: Solutions for waste remediation and biomining

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

Ashby, C.R.; Thompson, S.A.; Crusberg, T.C.

1997-12-31

The fungus Penicillium ochro-chloron is able to extract copper from aqueous solutions and form insoluble copper precipitates within the matrix of fungal mycelia. The formation of these complexes is probably a detoxification mechanism used by the organism to deal with the potentially lethal concentrations of heavy metals. Metal immobilization occurs external to the cells but within the mycelia when the solubility products of copper phosphate and copper oxalate are exceeded. This process may be exploited in biomining to remove and recover copper and perhaps other heavy metals that have become solubilized in pit mine lakes.

The three principles of action: a Pavlovian-instrumental transfer hypothesis

PubMed Central

Cartoni, Emilio; Puglisi-Allegra, Stefano; Baldassarre, Gianluca

2013-01-01

Pavlovian conditioned stimuli can influence instrumental responding, an effect called Pavlovian-instrumental transfer (PIT). During the last decade, PIT has been subdivided into two types: specific PIT and general PIT, each having its own neural substrates. Specific PIT happens when a conditioned stimulus (CS) associated with a reward enhances an instrumental response directed to the same reward. Under general PIT, instead, the CS enhances a response directed to a different reward. While important progress has been made into identifying the neural substrates, the function of specific and general PIT and how they interact with instrumental responses are still not clear. In the experimental paradigm that distinguishes specific and general PIT an effect of PIT inhibition has also been observed and is waiting for an explanation. Here we propose an hypothesis that links these three PIT effects (specific PIT, general PIT and PIT inhibition) to three aspects of action evaluation. These three aspects, which we call “principles of action”, are: context, efficacy, and utility. In goal-directed behavior, an agent has to evaluate if the context is suitable to accomplish the goal, the efficacy of his action in getting the goal, and the utility of the goal itself: we suggest that each of the three PIT effects is related to one of these aspects of action evaluation. In particular, we link specific PIT with the estimation of efficacy, general PIT with the evaluation of utility, and PIT inhibition with the adequacy of context. We also provide a latent cause Bayesian computational model that exemplifies this hypothesis. This hypothesis and the model provide a new framework and new predictions to advance knowledge about PIT functioning and its role in animal adaptation. PMID:24312025

A probability distribution model of tooth pits for evaluating time-varying mesh stiffness of pitting gears

NASA Astrophysics Data System (ADS)

Lei, Yaguo; Liu, Zongyao; Wang, Delong; Yang, Xiao; Liu, Huan; Lin, Jing

2018-06-01

Tooth damage often causes a reduction in gear mesh stiffness. Thus time-varying mesh stiffness (TVMS) can be treated as an indication of gear health conditions. This study is devoted to investigating the mesh stiffness variations of a pair of external spur gears with tooth pitting, and proposes a new model for describing tooth pitting based on probability distribution. In the model, considering the appearance and development process of tooth pitting, we model the pitting on the surface of spur gear teeth as a series of pits with a uniform distribution in the direction of tooth width and a normal distribution in the direction of tooth height, respectively. In addition, four pitting degrees, from no pitting to severe pitting, are modeled. Finally, influences of tooth pitting on TVMS are analyzed in details and the proposed model is validated by comparing with a finite element model. The comparison results show that the proposed model is effective for the TVMS evaluations of pitting gears.

Human imprint on archaeological anthroposols: first assessment of combined micromophological, pedological and lipid biomarkers analyses of organic matter

NASA Astrophysics Data System (ADS)

Cammas, Cécilia; Thuy Nguyen Tu, Thanh; Plessis, Marion; Clotuche, Raphaël; Derenne, Sylvie

2013-04-01

Archaeological anthroposol matrix contains significant amounts of fine organic matter (OM), which can give archaeological information. Geoarchaeological studies of OM aim to reveal its origin in order to reconstruct past human activities. Such studies are complex because the nature and the abundance of OM is the result of human activities together with natural processes. Also, MO evolves over time, a process that is not well understood. Combination of complementary approaches may give further insights into human imprint on archaeological anthroposols. For example, micromorphology gives data on in situ activities and pedological processes with the result that components of animal and vegetal origin can be identified but not some amorphous / fibrous material and very fine residues (< ~10 µm). On the other hand, pedological and geochemical analyses of bulk samples are often disconnected from contextual studies. Our work aims to (i) identify morphological and geochemical markers of human activity at different scales, (ii) compare results of different analytical methods to better understand the relation between matrix components and features, chemical properties, and geochemical markers, and (iii) infer relations between pedo-sedimentary history and OM preservation. Two tanning pits in urban craft areas were selected for sampling, as they are likely to contain large amounts of organic matter of vegetal and animal origin. The pit of Saint-Denis (SDN, 10 km at the north of Paris, calcareous alluvium, 13th cAD) was a reference tanning pit. The pit of Famars (FAM, near the Belgian border, luvisols, Roman period) was hypothesized to be a part of the tanning process. To assess preservation of organic components and molecules in relation with pedo-sedimentary context and their potential as biomarkers of human activities, methodology combined micromorphology, pedological analysis (C, N, LOI, P total, organic and inorganic phosphorus) and lipid analysis by GC/MS, lipids having a high preservation potential and containing biomarkers indicative of OM origin. Micromorphological study showed a high amount and diversity of organic components in the two pits. At the SDN pit, the interpretation of tanning (liming) was supported by the presence of scarce fragments of lime with calcitic hairs pseudomorphoses. Plant remains and bone fragments were identified, but red fibrous and yellow amorphous material were not. At the FAM pit, bones and coprolithic material were scarce, but there were abundant vegetal remains such as decaying and burnt fragments, as well as siliceous skeletons. Initial results of organic chemistry show that lipids were preserved (0,13 % for SDN, 0,09 % for FAM), and that lipids of vegetal origin were dominant in the two samples. At SDN, both plant and faecal material biomarkers were identified in the form of various sterols and coprostanol, respectively. Lipids extracted from FAM included ubiquitous compounds as well as plant biomarkers, but no faecal markers. The structure of several compounds is still to be elucidated. However, initial results may suggest that vegetal imprint in thin section and in lipid analysis can be correlated. For animal remains, the two methods seem to lead to different but complementary conclusions; the difference noted for inferred source material will be investigated in term of cultural and contextual origin.

Chemistry in Microfluidic Channels

ERIC Educational Resources Information Center

Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

2011-01-01

General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…

Using Games To Teach Chemistry: An Annotated Bibliography.

ERIC Educational Resources Information Center

Russell, Jeanne V.

1999-01-01

Lists 67 published or marketed chemistry games organized under the following categories: (1) general knowledge; (2) elements and atomic structure; (3) nomenclature, formulas, and equation writing; (4) chemical reactions; (5) solutions and solubilities; (6) organic chemistry, and (8) miscellaneous subjects. Includes a brief description of each…

NIR detection of pits and pit fragments in fresh cherries (abstract)

USDA-ARS?s Scientific Manuscript database

The feasibility of using near infrared (NIR) diffuse reflectance spectroscopy for the detection of pits and pit fragments in cherries was demonstrated. For detection of whole pits, 300 cherries were obtained locally and pits were removed from half. NIR reflectance spectra were obtained in triplicate...

7 CFR 52.779 - Freedom from pits.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Freedom from pits. 52.779 Section 52.779 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Freedom from pits. (a) General. The factor of freedom from pits refers to the incidence of pits and pit...

Effect of Bacillus subtilis on Granite Weathering: A Laboratory Experiment

NASA Astrophysics Data System (ADS)

Song, W.; Ogawa, N.; Oguchi, C. T.; Hatta, T.; Matsukura, Y.

2006-12-01

We performed a comparative experiment to investigate how the ubiquitous soil bacterium Bacillus subtilis weathers granite and which granite-forming minerals weather more rapidly via biological processes. Batch type experiments (granite specimen in a 500 ml solution including NaCl, glucose, yeast extract and bacteria Bacillus subtilis at 27°E C) were carried out for 30 days. Granite surfaces were observed by SEM before and after the experiment. Bacillus subtilis had a strong influence on granite weathering by forming pits. There were 2.4 times as many pits and micropores were 2.3 times wider in granite exposed to Bacillus subtilis when compared with bacteria-free samples. Bacillus subtilis appear to preferentially select an optimum place to adhere to the mineral and dissolve essential elements from the mineral to live. Plagioclase was more vulnerable to bacterial weathering than biotite among the granite composing minerals.

An Analysis of 16-17-Year-Old Students' Understanding of Solution Chemistry Concepts Using a Two-Tier Diagnostic Instrument

ERIC Educational Resources Information Center

Adadan, Emine; Savasci, Funda

2012-01-01

This study focused on the development of a two-tier multiple-choice diagnostic instrument, which was designed and then progressively modified, and implemented to assess students' understanding of solution chemistry concepts. The results of the study are derived from the responses of 756 Grade 11 students (age 16-17) from 14 different high schools…

Effects of simulated acid rain on soil and soil solution chemistry in a monsoon evergreen broad-leaved forest in southern China.

PubMed

Qiu, Qingyan; Wu, Jianping; Liang, Guohua; Liu, Juxiu; Chu, Guowei; Zhou, Guoyi; Zhang, Deqiang

2015-05-01

Acid rain is an environmental problem of increasing concern in China. In this study, a laboratory leaching column experiment with acid forest soil was set up to investigate the responses of soil and soil solution chemistry to simulated acid rain (SAR). Five pH levels of SAR were set: 2.5, 3.0, 3.5, 4.0, and 4.5 (as a control, CK). The results showed that soil acidification would occur when the pH of SAR was ≤3.5. The concentrations of NO₃(-)and Ca(2+) in the soil increased significantly when the pH of SAR fell 3.5. The concentration of SO₄(2-) in the soil increased significantly when the pH of SAR was <4.0. The effects of SAR on soil solution chemistry became increasingly apparent as the experiment proceeded (except for Na(+) and dissolved organic carbon (DOC)). The net exports of NO₃(-), SO₄(2-), Mg(2+), and Ca(2+) increased about 42-86% under pH 2.5 treatment as compared to CK. The Ca(2+) was sensitive to SAR, and the soil could release Ca(2+) through mineral weathering to mitigate soil acidification. The concentration of exchangeable Al(3+) in the soil increased with increasing the acidity of SAR. The releases of soluble Al and Fe were SAR pH dependent, and their net exports under pH 2.5 treatment were 19.6 and 5.5 times, respectively, higher than that under CK. The net export of DOC was reduced by 12-29% under SAR treatments as compared to CK. Our results indicate the chemical constituents in the soil are more sensitive to SAR than those in the soil solution, and the effects of SAR on soil solution chemistry depend not only on the intensity of SAR but also on the duration of SAR addition. The soil and soil solution chemistry in this region may not be affected by current precipitation (pH≈4.5) in short term, but the soil and soil leachate chemistry may change dramatically if the pH of precipitation were below 3.5 and 3.0, respectively.

Proportional Reasoning in the Learning of Chemistry: Levels of Complexity

ERIC Educational Resources Information Center

Ramful, Ajay; Narod, Fawzia Bibi

2014-01-01

This interdisciplinary study sketches the ways in which proportional reasoning is involved in the solution of chemistry problems, more specifically, problems involving quantities in chemical reactions (commonly referred to as stoichiometry problems). By building on the expertise of both mathematics and chemistry education research, the present…

The Synthesis of Copper(II) Carboxylates Revisited

ERIC Educational Resources Information Center

Kushner, Kevin; Spangler, Robert E.; Salazar, Ralph A., Jr.; Lagowski, J. J.

2006-01-01

An electrochemical synthesis of copper(II) carboxylates has been developed and used in the general chemistry laboratory course for chemistry majors. This synthesis, using nonaqueous solutions, supplements the strategy of providing experiences in synthetic chemistry described by Yoder et al. ("J. Chem. Educ." 1995, 72, 267). (Contains 1 table.)

The hardness, microstructure, and pitting resistance of austenitic stainless steel Fe25Ni15Cr with the addition of tungsten, niobium, and vanadium

NASA Astrophysics Data System (ADS)

Prifiharni, Siska; Anwar, Moch. Syaiful; Nikitasari, Arini; Mabruri, Efendi

2018-05-01

In this work, the effect of 2% W, 1%Nb, and 1% V addition on the hardness, microstructure, and pitting resistance to austenitic stainless steel Fe25Ni15Cr was investigated. The specimens were prepared in induction melting furnace, followed by homogenizing at 1100°C for 24 h. Then, the specimens were solution treated at 975°C for 2 h followed by water quenching and aging at 725°C for 15 h. The hardness was measured by using Rockwell hardness B, and metallographic observation was conducted using optical microscope and SEM-EDS. The results show that the increament of W, Nb, and V in the austenitic stainless steel Fe25Ni15Crby increased the hardness. The metal carbide precipitation occurred at grain boundaries in niobium free alloy. The addition of Nb in the alloy promotes the Laves phase transformation, and addition of V increase Nb content in the Laves phase. Laves phase formation in alloys containing niobium during aging heat treatments lead to an increase in hardness. Addition of W, Nb, and V also increase pitting resistance of the Fe25Ni15Cr austenitic stainless steel. This can be attributed to an increasing level of niobium in the matrix.

Effect of occlusal calculus utilized as a potential "biological sealant" in special needs patients with gastric feeding tubes: a qualitative in vitro contrast to pit and fissure sealant restorations.

PubMed

Owens, Barry M; Sharp, Harry K; Fourmy, Emily E; Phebus, Jeffrey G

2016-01-01

The aim of this case report and in vitro investigation was to evaluate the marginal microleakage of intact occlusal calculus of primary molars extracted from a special needs patient who received nutrition via a gastric feeding tube. An adolescent with a history of developmental disturbance presented for routine dental care in a hospital facility. Prophylaxis was performed, and 2 mandibular permanent molars were restored. Five primary molars were extracted due to mobility and delayed retention. Heavy deposits of intact calculus were present on the occlusal surfaces of the primary teeth. The extracted teeth were immersed in methylene blue dye solution, invested in acrylic resin, sectioned into blocks, and photographed at 20× and 40× magnification. Previously photographed calculus-free molars with pit and fissure sealants were reviewed and served as contrasting "restorations." The occlusal calculus on the primary teeth extracted from the patient absorbed the dye, while the comparison teeth containing pit and fissure sealants exhibited varying degrees of marginal dye penetration (microleakage). No marginal microleakage was noted in the calculus specimens, indicating that this substrate may serve as a "natural" occlusal surface sealant and that its removal from occlusal surfaces during routine oral prophylaxis may be unnecessary.

Study on effect of microparticle's size on cavitation erosion in solid-liquid system

NASA Astrophysics Data System (ADS)

Chen, Haosheng; Liu, Shihan; Wang, Jiadao; Chen, Darong

2007-05-01

Five different solutions containing microparticles in different sizes were tested in a vibration cavitation erosion experiment. After the experiment, the number of erosion pits on sample surfaces, free radicals HO• in solutions, and mass loss all show that the cavitation erosion strength is strongly related to the particle size, and 500nm particles cause more severe cavitation erosion than other smaller or larger particles do. A model is presented to explain such result considering both nucleation and bubble-particle collision effects. Particle of a proper size will increase the number of heterogeneous nucleation and at the same time reduce the number of bubble-particle combinations, which results in more free bubbles in the solution to generate stronger cavitation erosion.

Gravity-induced stresses in finite slopes

USGS Publications Warehouse

Savage, W.Z.

1994-01-01

An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

Dose-Dependent Dual Role of PIT-1 (POU1F1) in Somatolactotroph Cell Proliferation and Apoptosis

PubMed Central

Jullien, Nicolas; Roche, Catherine; Brue, Thierry; Figarella-Branger, Dominique; Graillon, Thomas; Barlier, Anne; Herman, Jean-Paul

2015-01-01

To test the role of wtPIT-1 (PITWT) or PIT-1 (R271W) (PIT271) in somatolactotroph cells, we established, using inducible lentiviral vectors, sublines of GH4C1 somatotroph cells that allow the blockade of the expression of endogenous PIT-1 and/or the expression of PITWT or PIT271, a dominant negative mutant of PIT-1 responsible for Combined Pituitary Hormone Deficiency in patients. Blocking expression of endogenous PIT-1 induced a marked decrease of cell proliferation. Overexpressing PITWT twofold led also to a dose-dependent decrease of cell proliferation that was accompanied by cell death. Expression of PIT271 induced a strong dose-dependent decrease of cell proliferation accompanied by a very pronounced cell death. These actions of PIT271 are independent of its interaction/competition with endogenous PIT-1, as they were unchanged when expression of endogenous PIT-1 was blocked. All these actions are specific for somatolactotroph cells, and could not be observed in heterologous cells. Cell death induced by PITWT or by PIT271 was accompanied by DNA fragmentation, but was not inhibited by inhibitors of caspases, autophagy or necrosis, suggesting that this cell death is a caspase-independent apoptosis. Altogether, our results indicate that under normal conditions PIT-1 is important for the maintenance of cell proliferation, while when expressed at supra-normal levels it induces cell death. Through this dual action, PIT-1 may play a role in the expansion/regression cycles of pituitary lactotroph population during and after lactation. Our results also demonstrate that the so-called “dominant-negative” action of PIT271 is independent of its competition with PIT-1 or a blockade of the actions of the latter, and are actions specific to this mutant variant of PIT-1. PMID:25822178

21 CFR 862.1540 - Osmolality test system.

Code of Federal Regulations, 2011 CFR

2011-04-01

...) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862... measure ionic and nonionic solute concentration in body fluids, such as serum and urine. Osmolality...

21 CFR 862.1540 - Osmolality test system.

Code of Federal Regulations, 2012 CFR

2012-04-01

...) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862... measure ionic and nonionic solute concentration in body fluids, such as serum and urine. Osmolality...

21 CFR 862.1540 - Osmolality test system.

Code of Federal Regulations, 2013 CFR

2013-04-01

...) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862... measure ionic and nonionic solute concentration in body fluids, such as serum and urine. Osmolality...

21 CFR 862.1540 - Osmolality test system.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862... measure ionic and nonionic solute concentration in body fluids, such as serum and urine. Osmolality...

Pretreatment of lignocellulosic biomass using Fenton chemistry.

PubMed

Kato, Dawn M; Elía, Noelia; Flythe, Michael; Lynn, Bert C

2014-06-01

In an attempt to mimic white-rot fungi lignin degradation via in vivo Fenton chemistry, solution phase Fenton chemistry (10 g biomass, 176 mmol hydrogen peroxide and 1.25 mmol Fe(2+) in 200 mL of water) was applied to four different biomass feedstocks. An enzymatic saccharification of Fenton pretreated biomass showed an average 212% increase relative to untreated control across all four feedstocks (P<0.05, statistically significant). A microbial fermentation of the same Fenton pretreated biomass showed a threefold increase in gas production upon a sequential co-culture with Clostridium thermocellum and Clostridium beijerinckii. These results demonstrate the use of solution phase Fenton chemistry as a viable pretreatment method to make cellulose more bioavailable for microbial biofuel conversion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Rain Erosion Studies of Sapphire, Aluminum Oxynitride, Spinel, Lanthana- Doped Yttria, and TAF Glass

DTIC Science & Technology

1990-07-01

small , there is little change in average scatter for any material in any test. CONCLUSIONS AND DISCUSSION The principal conclusions are 1. ALON...20 Sample broke erosion damage 10 Slight pitting, 20 No change erosion damage 15 Pitting, cratering, 20 Small surface pits erosion damage 15 Pitting...Sample broke 10 No damage 15 Sample pitted, small edge fracture 15 Slight pitting, 1 crater, 20 Sample pitted, erosion damage small edge fracture 15 SUght

Applied Geochemistry Special Issue on Environmental geochemistry of modern mining

USGS Publications Warehouse

Seal, Robert R.; Nordstrom, D. Kirk

2015-01-01

Environmental geochemistry is an integral part of the mine-life cycle, particularly for modern mining. The critical importance of environmental geochemistry begins with pre-mining baseline characterization and the assessment of environmental risks related to mining, continues through active mining especially in water and waste management practices, and culminates in mine closure. The enhanced significance of environmental geochemistry to modern mining has arisen from an increased knowledge of the impacts that historical and active mining can have on the environment, and from new regulations meant to guard against these impacts. New regulations are commonly motivated by advances in the scientific understanding of the environmental impacts of past mining. The impacts can be physical, chemical, and biological in nature. The physical challenges typically fall within the purview of engineers, whereas the chemical and biological challenges typically require a multidisciplinary array of expertise including geologists, geochemists, hydrologists, microbiologists, and biologists. The modern mine-permitting process throughout most of the world now requires that potential risks be assessed prior to the start of mining. The strategies for this risk assessment include a thorough characterization of pre-mining baseline conditions and the identification of risks specifically related to the manner in which the ore will be mined and processed, how water and waste products will be managed, and what the final configuration of the post-mining landscape will be.In the Fall 2010, the Society of Economic Geologists held a short course in conjunction with the annual meeting of the Geological Society of America in Denver, Colorado (USA) to examine the environmental geochemistry of modern mining. The intent was to focus on issues that are pertinent to current and future mines, as opposed to abandoned mines, which have been the focus of numerous previous short courses. The geochemical challenges of current and future mines share similarities with abandoned mines, but differences also exist. Mining and ore processing techniques have changed; the environmental footprint of waste materials has changed; environmental protection has become a more integral part of the mine planning process; and most historical mining was done with limited regard for the environment. The 17 papers in this special issue evolved from the Society of Economic Geologists’ short course.The relevant geochemical processes encompass the source, transport, and fate of contaminants related to the life cycle of a mine. Contaminants include metals and other inorganic species derived from geologic sources such as ore and solid mine waste, and substances brought to the site for ore processing, such as cyanide to leach gold. Factors, such as mine-waste mineralogy, hydrologic setting, mine-drainage chemistry, and microbial activity, that affect the hydrochemical risks from mining are reviewed by Nordstrom et al. In another paper, Nordstrom discusses baseline characterization at mine sites in a regulatory framework, and emphasizes the influence of mineral deposits in producing naturally elevated concentrations of many trace elements in surface water and groundwater. Surface water quality in mineralized watersheds is influenced by a number of processes that act on daily (diel) cycles and can produce dramatic variations in trace element concentrations as described by Gammons et al. Pre-mining baseline characterization studies should strive to capture the magnitude of these diel variations. Desbarats et al., using a case study of mine drainage from a gold mine, illustrate how elements that commonly occur as negatively charged species (anions) in solution, such as arsenic as arsenate, behave in an opposite fashion than most metals, which occur as positively charged species (cations). Significant improvement in the understanding of factors that influence the toxicity of metals to aquatic organisms in surface water has highlighted the importance of aqueous chemistry, particularly dissolved organic carbon, as described by Smith et al. Stream sediment contamination is another important pathway for affecting aquatic organisms, as reviewed by Besser et al. Understanding and predicting environmental consequences from mining begins with knowing the mineralogy and mineral reactivity of the ore, the wastes, and of secondary minerals formed later. Jamieson et al. review the importance of mineralogical studies in mine planning and remediation. A number of types of site-specific studies are needed to identify environmental risks related to individual mines. Lapakko reviews the general framework of mine waste characterization studies that are integral to the mine planning process. Hageman et al. present a comparative study of several static tests commonly used to characterize mine waste.The mining and ore processing practices employed at a specific mine site will vary on the basis of the commodities being targeted, the geology of the deposit, the geometry of the deposit, and the mining and ore processing methods used. Thus, these factors, in addition to the waste management practices used, can result in a variety of end-member mine waste features, each of which has its own set of challenges. Open pit mines and underground mines require waste rock to be removed to access ore. Waste rock presents unique problems because the rock is commonly mineralized at sub-economic grades and has not been processed to remove potentially problematic minerals, such as pyrite. Amos et al. examine the salient aspects of the geochemistry of waste rock. Mill tailings – the waste material after ore minerals have been removed – are a volumetrically important solid waste at many mine sites. Their fine grain size and the options for their management make their behavior in the environment distinct from that of waste rock. Lindsay et al. describe some of these differences through three case-study examples. Subaqueous disposal of tailings is another option described by Moncur et al. Cyanide leaching for gold extraction is a common method throughout the world. Johnson describes environmental aspects of cyanidation. Uranium mining presents unique environmental challenges, particularly since in-situ recovery has seen widespread use. Campbell et al. review the environmental geochemistry of uranium mining and current research on bioremediation. Ore concentrates from many types of metal mining undergo a pyrometallurgical technique known as smelting to extract the metal. Slag is the result of smelting, and it may be an environmental liability or a valuable byproduct, as described by Piatak et al. Finally, the open pits that result from surface mining commonly reach below the water table. At the end of mining, these pits may fill to form lakes that become part of the legacy of the mine. Castendyk et al., in two papers, review theoretical aspects of the environmental limnology of pit lakes. They also describe approaches that have been used to model pit lake water balance, wall-rock contributions to pit lake chemistry, pit lake water quality, and limnological processes, such as vertical mixing, through the use of three case studies.

Prebiotic chemistry in eutectic solutions at the water-ice matrix.

PubMed

Menor-Salván, César; Marín-Yaseli, Margarita R

2012-08-21

A crystalline ice matrix at subzero temperatures can maintain a liquid phase where organic solutes and salts concentrate to form eutectic solutions. This concentration effect converts the confined reactant solutions in the ice matrix, sometimes making condensation and polymerisation reactions occur more favourably. These reactions occur at significantly high rates from a prebiotic chemistry standpoint, and the labile products can be protected from degradation. The experimental study of the synthesis of nitrogen heterocycles at the ice-water system showed the efficiency of this scenario and could explain the origin of nucleobases in the inner Solar System bodies, including meteorites and extra-terrestrial ices, and on the early Earth. The same conditions can also favour the condensation of monomers to form ribonucleic acid and peptides. Together with the synthesis of these monomers, the ice world (i.e., the chemical evolution in the range between the freezing point of water and the limit of stability of liquid brines, 273 to 210 K) is an under-explored experimental model in prebiotic chemistry.

Phosphate (Pi)-regulated heterodimerization of the high-affinity sodium-dependent Pi transporters PiT1/Slc20a1 and PiT2/Slc20a2 underlies extracellular Pi sensing independently of Pi uptake.

PubMed

Bon, Nina; Couasnay, Greig; Bourgine, Annabelle; Sourice, Sophie; Beck-Cormier, Sarah; Guicheux, Jérôme; Beck, Laurent

2018-02-09

Extracellular phosphate (P i ) can act as a signaling molecule that directly alters gene expression and cellular physiology. The ability of cells or organisms to detect changes in extracellular P i levels implies the existence of a P i -sensing mechanism that signals to the body or individual cell. However, unlike in prokaryotes, yeasts, and plants, the molecular players involved in P i sensing in mammals remain unknown. In this study, we investigated the involvement of the high-affinity, sodium-dependent P i transporters PiT1 and PiT2 in mediating P i signaling in skeletal cells. We found that deletion of PiT1 or PiT2 blunted the P i -dependent ERK1/2-mediated phosphorylation and subsequent gene up-regulation of the mineralization inhibitors matrix Gla protein and osteopontin. This result suggested that both PiTs are necessary for P i signaling. Moreover, the ERK1/2 phosphorylation could be rescued by overexpressing P i transport-deficient PiT mutants. Using cross-linking and bioluminescence resonance energy transfer approaches, we found that PiT1 and PiT2 form high-abundance homodimers and P i -regulated low-abundance heterodimers. Interestingly, in the absence of sodium-dependent P i transport activity, the PiT1-PiT2 heterodimerization was still regulated by extracellular P i levels. Of note, when two putative P i -binding residues, Ser-128 (in PiT1) and Ser-113 (in PiT2), were substituted with alanine, the PiT1-PiT2 heterodimerization was no longer regulated by extracellular P i These observations suggested that P i binding rather than P i uptake may be the key factor in mediating P i signaling through the PiT proteins. Taken together, these results demonstrate that P i -regulated PiT1-PiT2 heterodimerization mediates P i sensing independently of P i uptake. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Analysis of the bacterial community in aged and aging pit mud of Chinese Luzhou-flavour liquor by combined PCR-DGGE and quantitative PCR assay.

PubMed

Liang, Huipeng; Li, Wenfang; Luo, Qingchun; Liu, Chaolan; Wu, Zhengyun; Zhang, Wenxue

2015-10-01

The community structure of bacteria in aged and aging pit mud, which was judged according to their sensory and physicochemical characteristics, was analysed using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative real-time PCR (qPCR). The phyla Firmicutes, Actinobacteria, Proteobacteria, Synergistetes and Unclassified Bacteria were detected and the fermentative Firmicutes was predominant in both types of pit mud in the PCR-DGGE analysis. Among Firmicutes, Clostridiales was dominant in aged pit mud while Bacillales and Lactobacillales were dominant in aging pit mud. The diversity of bacterial communities in aged pit mud was higher than that in aging pit mud. In the qPCR analysis the abundance of Clostridium IV in aged pit mud was higher than that in aging pit mud and there were significant differences in the quantity of Clostridium IV between aged and aging pit mud of the same cellar (P < 0.05). There were some significant differences in the microbial community structure between aged and aging pit mud. The differences in the quantity of Clostridium IV might be involved in the distinction that the aged pit mud has a strong aroma while the aging pit mud does not. © 2014 Society of Chemical Industry.

Structure and function of bordered pits: new discoveries and impacts on whole-plant hydraulic function.

PubMed

Choat, Brendan; Cobb, Alexander R; Jansen, Steven

2008-01-01

Bordered pits are cavities in the lignified cell walls of xylem conduits (vessels and tracheids) that are essential components in the water-transport system of higher plants. The pit membrane, which lies in the center of each pit, allows water to pass between xylem conduits but limits the spread of embolism and vascular pathogens in the xylem. Averaged across a wide range of species, pits account for > 50% of total xylem hydraulic resistance, indicating that they are an important factor in the overall hydraulic efficiency of plants. The structure of pits varies dramatically across species, with large differences evident in the porosity and thickness of pit membranes. Because greater porosity reduces hydraulic resistance but increases vulnerability to embolism, differences in pit structure are expected to correlate with trade-offs between efficiency and safety of water transport. However, trade-offs in hydraulic function are influenced both by pit-level differences in structure (e.g. average porosity of pit membranes) and by tissue-level changes in conduit allometry (average length, diameter) and the total surface area of pit membranes that connects vessels. In this review we address the impact of variation in pit structure on water transport in plants from the level of individual pits to the whole plant.

PitScan: Computer-Assisted Feature Detection

NASA Astrophysics Data System (ADS)

Wagner, R. V.; Robinson, M. S.

2018-04-01

We developed PitScan to assist in searching the very large LROC image dataset for pits — unusual <200m wide vertical-walled holes in the Moon's surface. PitScan reduces analysts' workload by pre-filtering images to identify possible pits.

Quantitative Correlation of 7B04 Aluminum Alloys Pitting Corrosion Morphology Characteristics with Stress Concentration Factor

NASA Astrophysics Data System (ADS)

Liu, Zhiguo; Yan, Guangyao; Mu, Zhitao; Li, Xudong

2018-01-01

The accelerated pitting corrosion test of 7B04 aluminum alloy specimen was carried out according to the spectrum which simulated airport environment, and the corresponding pitting corrosion damage was obtained and was defined through three parameters A and B and C which respectively denoted the corrosion pit surface length and width and corrosion pit depth. The ratio between three parameters could determine the morphology characteristics of corrosion pits. On this basis the stress concentration factor of typical corrosion pit morphology under certain load conditions was quantitatively analyzed. The research shows that the corrosion pits gradually incline to be ellipse in surface and moderate in depth, and most value of B/A and C/A lies in 1 between 4 and few maximum exceeds 4; The stress concentration factor Kf of corrosion pits is obviously affected by the its morphology, the value of Kf increases with corrosion pits depth increasement under certain corrosion pits surface geometry. Also, the value of Kf decreases with surface width increasement under certain corrosion pits depth. The research conclusion can set theory basis for corrosion fatigue life analysis of aircraft aluminum alloy structure.

SRNL SHELF LIFE STUDIES - SCC STUDIES AT ROOM TEMPERTURE [stress corrosion cracking

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

Mickalonis, J.; Duffey, J.

Phase II, Series 2 corrosion testing performed by the Savannah River National Laboratory (SRNL) for the Department of Energy 3013 container has been completed. The corrosion tests are part of an integrated plan conducted jointly by Los Alamos National Laboratory and the Savannah River Site. SRNL was responsible for conducting corrosion studies in small-scale vessels to address the influence of salt composition, water loading, and type of oxide/salt contact on the relative humidity inside a 3013 container and on the resulting corrosion of Type 304L and 316L stainless steel (304L and 316L). This testing was conducted in two phases: Phasemore » I evaluated a broad spectrum of salt compositions and initial water loadings on the salt mixtures exposed to 304L and 316L and the resulting corrosion; Phase II evaluated the corrosion of 304L at specific water loadings and a single salt composition. During Phase I testing at high initial moisture levels (0.35 to 1.24 wt%)a, the roomtemperature corrosion of 304L exposed to a series of plutonium oxide/chloride salt mixtures ranged from superficial staining to pitting and stress corrosion cracking (SCC). 304L teardrop coupons that exhibited SCC were directly exposed to a mixture composed of 98 wt % PuO2, 0.9 wt % NaCl, 0.9 wt % KCl, and 0.2 wt % CaCl2. Cracking was not observed in a 316L teardrop coupon. Pitting was also observed in this environment for both 304L and 316L with depths ranging from 20 to 100 μm. Neither pitting nor SCC was observed in mixtures with a greater chloride salt concentration (5 and 28 wt%). These results demonstrated that for a corrosive solution to form a balance existed between the water loading and the salt chloride concentration. This chloride solution results from the interaction of loaded water with the hydrating CaCl2 salt. In Phase II, Series 1 tests, the SCC results were shown to be reproducible with cracking occurring in as little as 85 days. The approximate 0.5 wt% moisture level was found to result in an initial relative humidity of ~55% within the small-scale vessels. Pits were found to be associated with cracks and appeared to act as initiators for the cracking. In a vapor-space only exposure, the weld oxide, which results from the TIG closure weld used to fabricate the teardrop coupon, was also shown to be more susceptible to pitting corrosion than a surface free from weld oxide. This result has important implications for the closure weld of the 3013 inner can since the weld oxide on the can internal surface cannot be removed. The results from the Phase II, Series 2 tests further demonstrated the significance of forming a solution with a critical chloride concentration for corrosion to proceed. 304L teardrop coupons were found to corrode only by pitting with a similar oxide/salt mixture as used in Series 1 testing but with a lower water loading of 0.2 wt%, which resulted in an initial relative humidity of 35-38%. These tests ran twice as long as those for Series 1 testing. The exposure condition was also found to impact the corrosion with salt-exposed surfaces showing lower corrosion resistance. Additional analyses of the Series 2 coupons are recommended especially for determining if cracks emanate from the bottom of pits. Data generated under the 2009 3013 corrosion test plan, as was presented here, increased the understanding of the corrosion process within a sealed 3013 container. Along with the corrosion data from destructive evaluations of 3013 containers, the inner can closure weld region (ICCWR) has been identified as the most vulnerable area of the inner can where corrosion may lead to corrosive species leaking to the interior surface of the outer container, thereby jeopardizing the integrity of the 3013 container. A new corrosion plan has been designed that will characterize the corrosion at the ICCWR of 3013 DEs as well as parameters affecting this corrosion.« less

Structures of Bordered Pits Potentially Contributing to Isolation of a Refilled Vessel from Negative Xylem Pressure in Stems of Morus australis Poir.: Testing of the Pit Membrane Osmosis and Pit Valve Hypotheses.

PubMed

Ooeda, Hiroki; Terashima, Ichiro; Taneda, Haruhiko

2017-02-01

Two hypotheses have been proposed to explain the mechanism preventing the refilling vessel water from being drained to the neighboring functional vessels under negative pressure. The pit membrane osmosis hypothesis proposes that the xylem parenchyma cells release polysaccharides that are impermeable to the intervessel pit membranes into the refilling vessel; this osmotically counteracts the negative pressure, thereby allowing the vessel to refill. The pit valve hypothesis proposes that gas trapped within intervessel bordered pits isolates the refilling vessel water from the surrounding functional vessels. Here, using the single-vessel method, we assessed these hypotheses in shoots of mulberry (Morus australis Poir.). First, we confirmed the occurrence of xylem refilling under negative pressure in the potted mulberry saplings. To examine the pit membrane osmosis hypothesis, we estimated the semi-permeability of pit membranes for molecules of various sizes and found that the pit membranes were not semi-permeable to polyethylene glycol of molecular mass <20,000. For the pit valve hypothesis, we formed pit valves in the intervessel pits in the short stem segments and measured the maximum liquid pressure up to which gases in bordered pits were retained. The threshold pressure ranged from 0.025 to 0.10 MPa. These values matched the theoretical value calculated from the geometry of the pit chamber (0.0692-0.101 MPa). Our results suggest that gas in the pits is retained by surface tension, even under substantial positive pressure to resolve gases in the refilling vessel, whereas the molecule size required for the pit membrane osmosis mechanism in mulberry would be unrealistically large. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Comparison of short-term in vitro fluoride release and recharge from four different types of pit-and-fissure sealants.

PubMed

Koga, Hiroshi; Kameyama, Atsushi; Matsukubo, Takashi; Hirai, Yoshito; Takaesu, Yoshinori

2004-08-01

The purpose of this in vitro study was to assess the effects of four commercial fluoride-containing pit-and-fissure sealants on caries prevention. Four sealants containing fluoride, Fuji III, Fuji III LC (GC Co., Tokyo), Teethmate F-1 (Kuraray Medical Co., Osaka) and Helioseal F (Vivadent Co., Liechtenstein) were used to investigate fluoride release and recharge. Disk-shaped specimens prepared from each material were immersed in distilled water at a temperature of 37 degrees C. After seven days, acidulated phosphate fluoride solution (APF) was applied to each specimen, and it was then again immersed in distilled water for 14 days. We then determined how much fluoride had been released into the immersing water. Fuji III LC was used with APF solution to investigate the fluoride uptake. Fuji III had the highest fluoride release, and Fuji III LC had the highest fluoride recharge. Helioseal F and Teethmate F-1 had almost no fluoride recharge. Fuji III LC/APF had a higher fluoride uptake to enamel than Fuji III LC. These results suggest that GIC-sealants in the oral cavity can serve as a fluoride reservoir and contribute to retaining a low fluoride level in oral fluids, thereby preventing caries.

Susceptibility of nitinol to localized corrosion.

PubMed

Pound, Bruce G

2006-04-01

The effect of different conditions on the susceptibility of nitinol to localized corrosion was examined using the cyclic potentiodynamic polarization technique. Tests were performed on mechanically polished (MP) and electropolished (EP) nitinol wire in 0.9 wt % NaCl and phosphate-buffered saline (PBS). A polarization curve was also obtained for an EP stent in the NaCl. Differences between the breakdown potential and the corrosion potential (E(corr)) and between the protection potential and E(corr) were used to evaluate the susceptibility to pitting corrosion and crevice corrosion, respectively. The type of solution and, particularly, the surface condition affected the resistance of nitinol to pitting corrosion. Both EP and MP nitinol were more susceptible to breakdown in the NaCl than in PBS, indicating that the NaCl provides a more severe test environment than does PBS. Electropolishing increased the breakdown resistance of nitinol in PBS and the NaCl, as found in previous studies with Hank's solution. Surface condition, however, did not have a significant effect on the repassivation behavior of nitinol, as is also the case with titanium. The EP wire and stent showed similar breakdown and repassivation behavior in the NaCl, suggesting that the nature of the EP surface was similar in both cases. (c) 2005 Wiley Periodicals, Inc.

Acquired pit of the optic nerve: a risk factor for progression of glaucoma.

PubMed

Ugurlu, S; Weitzman, M; Nduaguba, C; Caprioli, J

1998-04-01

To examine acquired pit of the optic nerve as a risk factor for progression of glaucoma. In a retrospective longitudinal study, 25 open-angle glaucoma patients with acquired pit of the optic nerve were compared with a group of 24 open-angle glaucoma patients without acquired pit of the optic nerve. The patients were matched for age, mean intraocular pressure, baseline ratio of neuroretinal rim area to disk area, visual field damage, and duration of follow-up. Serial optic disk photographs and visual fields of both groups were evaluated by three independent observers for glaucomatous progression. Of 46 acquired pits of the optic nerve in 37 eyes of 25 patients, 36 pits were located inferiorly (76%) and 11 superiorly (24%; P < .001). Progression of optic disk damage occurred in 16 patients (64%) in the group with acquired pit and in three patients (12.5%) in the group without acquired pit (P < .001). Progression of visual field loss occurred in 14 patients (56%) in the group with acquired pit and in six (25%) in the group without pit (P=.04). Bilateral acquired pit of the optic nerve was present in 12 patients (48%). Disk hemorrhages were observed more frequently in the group with acquired pit (10 eyes, 40%) compared with the group without pit (two eyes, 8%; P=.02). Among patients with glaucoma, patients with acquired pit of the optic nerve represent a subgroup who are at increased risk for progressive optic disk damage and visual field loss.

Parturition pit: the bony imprint of vaginal birth.

PubMed

McArthur, Tatum A; Meyer, Isuzu; Jackson, Bradford; Pitt, Michael J; Larrison, Matthew C

2016-09-01

To retrospectively evaluate for pits along the dorsum of the pubic body in females and compare the presence/absence of these pits to vaginal birth data. We retrospectively reviewed females with vaginal birth data who underwent pelvic CT. The presence of pits along the dorsum of the pubic body, pit grade (0 = not present; 1 = faintly imperceptible; 2 = present; 3 = prominent), and the presence of osteitis condensans ilii, preauricular sulcus, and sacroiliac joint vacuum phenomenon were assessed on imaging. Musculoskeletal radiologists who were blinded to the birth data evaluated the CTs. 48 males were also evaluated for the presence of pits. 482 female patients underwent CT pelvis and 171 were excluded due to lack of vaginal birth data. Of the 311 study patients, 262 had prior vaginal birth(s) and 194 had pits on CT. Only 7 of the 49 patients without prior vaginal birth had pits. There was a statistically significant association between vaginal birth and presence of pits (p < 0.0001). Patients with more prominent pits (grades 2/3) had a greater number of vaginal births. As vaginal deliveries increased, the odds of having parturition pits greatly increased, adjusting for age and race at CT (p < 0.0001). No males had pits. Our study indicates that parturition pits are associated with prior vaginal birth and should be considered a characteristic of the female pelvis. The lytic appearance of prominent pits on imaging can simulate disease and create a diagnostic dilemma for interpreting radiologists.

Parturition Pit: The Bony Imprint of Vaginal Birth

PubMed Central

Meyer, Isuzu; Jackson, Bradford; Pitt, Michael J.; Larrison, Matthew C.

2017-01-01

Purpose To retrospectively evaluate for pits along the dorsum of the pubic body in females and compare the presence/absence of these pits to vaginal birth data. Materials and Methods We retrospectively reviewed females with vaginal birth data who underwent pelvic CT. The presence of pits along the dorsum of the pubic body, pit grade (0 = not present; 1 = faintly imperceptible; 2 = present; 3 = prominent), and the presence of osteitis condensans ilii, preauricular sulcus, and sacroiliac joint vacuum phenomenon were assessed on imaging. Musculoskeletal radiologists who were blinded to the birth data evaluated the CTs. 48 males were also evaluated for the presence of pits. Results 482 female patients underwent CT pelvis and 171 were excluded due to lack of vaginal birth data. Of the 311 study patients, 262 had prior vaginal birth(s) and 194 had pits on CT. Only 7 of the 49 patients without prior vaginal birth had pits. There was a statistically significant association between vaginal birth and presence of pits (p<0.0001). Patients with more prominent pits (grades 2/3) had a greater number of vaginal births. As vaginal deliveries increased, the odds of having parturition pits greatly increased, adjusting for age and race at CT (p<0.0001). No males had pits. Conclusion Our study indicates that parturition pits are associated prior vaginal birth and should be considered a characteristic of the female pelvis. The lytic appearance of prominent pits on imaging can simulate disease and create a diagnostic dilemma for interpreting radiologists. PMID:27270921

The effect of normal pulsed Nd-YAG laser irradiation on pits and fissures in human teeth.

PubMed

Bahar, A; Tagomori, S

1994-01-01

The effects of normal pulsed Nd-YAG laser irradiation on the acid resistance of human dental enamel of pits and fissures, the cleaning of the pit and fissure contents and fluoride uptake into deep pits and fissures were examined. The acid resistance of the pit and fissure enamel was evaluated by the amount of dissolved calcium per square millimeter of the surface area. The pit and fissure enamel treated with laser irradiation obtained an acid resistance 30% higher than that of the unlased controls. The cleaning effect of laser irradiation on the pit and fissure contents was compared with chemicomechanical and mechanical methods. The laser irradiation was found to clean the pits and fissures to a greater depth without alterating the shape of pits and fissures, compared with the other two methods. The distribution of calcium, phosphorus and fluoride in the enamel of the pits and fissures was then measured by electron probe microanalyzer. At the entrance and in the deep part of the pits and fissures, the fluoride content of the enamel treated with acidulated phosphate fluoride after laser irradiation was higher than that of the enamel treated with acidulated phosphate fluoride alone. These results thus suggest that Nd-YAG laser irradiation might be effective in increasing the acid resistance of the pit and fissure enamel, while removing the pit and fissure debris contents and increasing the fluoride uptake into the pit and fissure enamel.

College Students Solving Chemistry Problems: A Theoretical Model of Expertise

ERIC Educational Resources Information Center

Taasoobshirazi, Gita; Glynn, Shawn M.

2009-01-01

A model of expertise in chemistry problem solving was tested on undergraduate science majors enrolled in a chemistry course. The model was based on Anderson's "Adaptive Control of Thought-Rational" (ACT-R) theory. The model shows how conceptualization, self-efficacy, and strategy interact and contribute to the successful solution of quantitative,…

Dynamic Vertical Profiles of Peat Porewater Chemistry in a Northern Peatland

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

Griffiths, Natalie A.; Sebestyen, Stephen D.

We measured pH, cations, nutrients, and total organic carbon (TOC) over 3 years to examine weekly to monthly variability in porewater chemistry depth profiles (0–3.0 m) in an ombrotrophic bog in Minnesota, USA. We also compared temporal variation at one location to spatial variation in depth profiles at 16 locations across the bog. Most solutes exhibited large gradients with depth. pH increased by two units and calcium concentrations increased over 20 fold with depth, and may reflect peatland development from minerotrophic to ombrotrophic conditions. Ammonium concentrations increased almost 20 fold and TOC concentrations decreased by half with depth, and thesemore » patterns likely reflect mineralization of peat or decomposition of TOC. There was also considerable temporal variation in the porewater chemistry depth profiles. Ammonium, soluble reactive phosphorus, and potassium showed greater temporal variation in near-surface porewater, while pH, calcium, and TOC varied more at depth. This variation demonstrates that deep peat porewater chemistry is not static. Lastly, temporal variation in solute chemistry depth profiles was greater than spatial variation in several instances, especially in shallow porewaters. In conclusion, characterizing both temporal and spatial variability is necessary to ensure representative sampling in peatlands, especially when calculating solute pools and fluxes and parameterizing process-based models.« less

Dynamic Vertical Profiles of Peat Porewater Chemistry in a Northern Peatland

DOE PAGES

Griffiths, Natalie A.; Sebestyen, Stephen D.

2016-10-14

We measured pH, cations, nutrients, and total organic carbon (TOC) over 3 years to examine weekly to monthly variability in porewater chemistry depth profiles (0–3.0 m) in an ombrotrophic bog in Minnesota, USA. We also compared temporal variation at one location to spatial variation in depth profiles at 16 locations across the bog. Most solutes exhibited large gradients with depth. pH increased by two units and calcium concentrations increased over 20 fold with depth, and may reflect peatland development from minerotrophic to ombrotrophic conditions. Ammonium concentrations increased almost 20 fold and TOC concentrations decreased by half with depth, and thesemore » patterns likely reflect mineralization of peat or decomposition of TOC. There was also considerable temporal variation in the porewater chemistry depth profiles. Ammonium, soluble reactive phosphorus, and potassium showed greater temporal variation in near-surface porewater, while pH, calcium, and TOC varied more at depth. This variation demonstrates that deep peat porewater chemistry is not static. Lastly, temporal variation in solute chemistry depth profiles was greater than spatial variation in several instances, especially in shallow porewaters. In conclusion, characterizing both temporal and spatial variability is necessary to ensure representative sampling in peatlands, especially when calculating solute pools and fluxes and parameterizing process-based models.« less

Pitting corrosion as a mixed system: coupled deterministic-probabilistic simulation of pit growth

NASA Astrophysics Data System (ADS)

Ibrahim, Israr B. M.; Fonna, S.; Pidaparti, R.

2018-05-01

Stochastic behavior of pitting corrosion poses a unique challenge in its computational analysis. However, it also stems from electrochemical activity causing general corrosion. In this paper, a framework for corrosion pit growth simulation based on the coupling of the Cellular Automaton (CA) and Boundary Element Methods (BEM) is presented. The framework assumes that pitting corrosion is controlled by electrochemical activity inside the pit cavity. The BEM provides the prediction of electrochemical activity given the geometrical data and polarization curves, while the CA is used to simulate the evolution of pit shapes based on electrochemical activity provided by BEM. To demonstrate the methodology, a sample case of local corrosion cells formed in pitting corrosion with varied dimensions and polarization functions is considered. Results show certain shapes tend to grow in certain types of environments. Some pit shapes appear to pose a higher risk by being potentially significant stress raisers or potentially increasing the rate of corrosion under the surface. Furthermore, these pits are comparable to commonly observed pit shapes in general corrosion environments.

Experimental research on micro-pit defects of SUS 430 stainless steel strip in cold rolling process

NASA Astrophysics Data System (ADS)

Li, Changsheng; Li, Miao; Zhu, Tao; Huo, Gang

2013-05-01

In order to improve surface glossiness of stainless steel strip in tandem cold rolling, experimental research on micro-pit defects of SUS 430 ferrite stainless steel was investigated in laboratory. The surface morphology of micro-pit defects was observed by SEM. The effects of micro-pit defects on rolling reduction, roll surface roughness and emulsion parameters were analyzed. With the pass number increasing, the quantity and surface of micro-pit defects were reduced, uneven peak was decreased and gently along rolling direction, micro-pit defects had equally distributed tendency along tranverse direction. The micro-pit defects were increased with the roll surface roughness increase. The defects ratio was declined with larger gradient at pass number 1 to 3, but gentle slope at pass number 4 to 5. The effects of temperature 55° and 63°, concentration 3% and 6% of emulsion on micro-pit effects had not obvious difference. Maintain of micro-pit was effected by rolling oil or air in the micro-pit, the quality of oil was much more than the air in the micro-pit in lubrication rolling.

Monitoring of surface deformation in open pit mine using DInSAR time-series: a case study in the N5W iron mine (Carajás, Brazil) using TerraSAR-X data

NASA Astrophysics Data System (ADS)

Mura, José C.; Paradella, Waldir R.; Gama, Fabio F.; Santos, Athos R.; Galo, Mauricio; Camargo, Paulo O.; Silva, Arnaldo Q.; Silva, Guilherme G.

2014-10-01

We present an investigation of surface deformation using Differential SAR Interferometry (DInSAR) time-series carried out in an active open pit iron mine, the N5W, located in the Carajás Mineral Province (Brazilian Amazon region), using 33 TerraSAR-X (TSX-1) scenes. This mine has presented a historical of instability and surface monitoring measurements over sectors of the mine (pit walls) have been done based on ground based radar. Two complementary approaches were used: the standard DInSAR configuration, as an early warning of the slope instability conditions, and the DInSAR timeseries analysis. In order to decrease the topographic phase error a high resolution DEM was generated based on a stereo GeoEye-1 pair. Despite the fact that a DinSAR contains atmospheric and topographic phase artifacts and noise, it was possible to detect deformation in some interferometric pairs, covering pit benches, road ramps and waste piles. The timeseries analysis was performed using the 31 interferometric pairs, which were selected based on the highest mean coherence of a stack of 107 interferograms, presenting less phase unwrapping errors. The time-series deformation was retrieved by the Least-Squares (LS) solution using an extension of the Singular Value Decomposition (SVD), with a set of additional weighted constrain on the acceleration deformation. The atmospheric phase artifacts were filtered in the space-time domain and the DEM height errors were estimated based on the normal baseline diversity. The DInSAR time-series investigation showed good results for monitoring surface displacement in the N5W mine located in a tropical rainforest environment, providing very useful information about the ground movement for alarm, planning and risk assessment.

Effect of Welding Process on Microstructure, Mechanical and Pitting Corrosion Behaviour of 2205 Duplex Stainless Steel Welds

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

An attempt has been made to weld 2205 Duplex stainless steel of 6mm thick plate using conventional gas tungsten arc welding (GTAW) and activated gas tungsten arc welding (A- GTAW) process using silica powder as activated flux. Present work is aimed at studying the effect of welding process on depth of penetration, width of weld zone of 2205 duplex stainless steel. It also aims to observe the microstructural changes and its effect on mechanical properties and pitting corrosion resistance of 2205 duplex stainless steel welds. Metallography is done to observe the microstructural changes of the welds using image analyzer attached to the optical microscopy. Hardness studies, tensile and ductility bend tests were evaluated for mechanical properties. Potentio-dynamic polarization studies were carried out using a basic GillAC electro-chemical system in 3.5% NaCl solution to observe the pitting corrosion behaviour. Results of the present investigation established that increased depth of penetration and reduction of weld width in a single pass by activated GTAW with the application of SiO2 flux was observed when compared with conventional GTAW process. It may be attributed to the arc constriction effect. Microstructure of the weld zones for both the welds is observed to be having combination of austenite and delta ferrite. Grain boundary austenite (GBA) with Widmanstatten-type austenite (WA) of plate-like feature was nucleated from the grain boundaries in the weld zone of A-GTAW process. Mechanical properties are relatively low in activated GTAW process and are attributed to changes in microstructural morphology of austenite. Improved pitting corrosion resistance was observed for the welds made with A-GTAW process.

Role of Rhipicephalus microplus cheliceral receptors in gustation and host differentiation.

PubMed

Ferreira, Lorena Lopes; Soares, Sara Fernandes; de Oliveira Filho, Jaires Gomes; Oliveira, Thaynara Tatielly; Pérez de León, Adalberto A; Borges, Lígia Miranda Ferreira

2015-04-01

Rhipicephalus microplus is considered the most economically important ectoparasite of cattle worldwide. It is known that zebuine breeds of cattle are less susceptible to tick infestation than taurine breeds. Contact chemoreceptors in the cheliceral pit sensilla of ticks respond selectively to phagostimulant compounds, however their role in blood feeding relative to host susceptibility to infestation remains to be fully understood. We addressed this topic by conducting taste electrophysiology experiments with cheliceral pit sensilla preparations of R. microplus females. Solutions of five known ixodid tick phagostimulants were tested at different concentrations: sodium (NaCl), and potassium chloride (KCl) (10(-3)-10(-1)M); glucose (10(-4)-10(-1)M); adenosine triphosphate (ATP) (10(-6)-10(-2)M); and reduced l-glutathione (GSH) (10(-6)-10(-2)M). Serum samples from six susceptible animals of the Girolando breed (5/8 Bos indicus×3/8 B. taurus) and six resistant Nelore bovines (pure B. indicus) were also tested. A dose-dependent response of gustatory neurons associated with the chelicerae sensillum to NaCl, glucose, GSH, and ATP were observed. Responses by the cheliceral inner digit pit sensilla of R. microplus to KCl and glucose were also observed and they are reported here for the first time. In addition to an electrophysiological response to known phagostimulants, chemoreceptors in the chelicera of R. microplus responded differently to serum from cattle susceptible and resistant to infestation. The cheliceral pit neurons were more responsive to serum of R. microplus resistant bovines with a higher mean spike frequency (53.5±2spikess(-1)) than to serum samples from susceptible cattle (40.3±2spikess(-1)). The implications of chemosensation during tick blood feeding are discussed. Copyright © 2015 Elsevier GmbH. All rights reserved.

Distribution, morphology, and origins of Martian pit crater chains

NASA Astrophysics Data System (ADS)

Wyrick, Danielle; Ferrill, David A.; Morris, Alan P.; Colton, Shannon L.; Sims, Darrell W.

2004-06-01

Pit craters are circular to elliptical depressions found in alignments (chains), which in many cases coalesce into linear troughs. They are common on the surface of Mars and similar to features observed on Earth and other terrestrial bodies. Pit craters lack an elevated rim, ejecta deposits, or lava flows that are associated with impact craters or calderas. It is generally agreed that the pits are formed by collapse into a subsurface cavity or explosive eruption. Hypotheses regarding the formation of pit crater chains require development of a substantial subsurface void to accommodate collapse of the overlying material. Suggested mechanisms of formation include: collapsed lava tubes, dike swarms, collapsed magma chamber, substrate dissolution (analogous to terrestrial karst), fissuring beneath loose material, and dilational faulting. The research described here is intended to constrain current interpretations of pit crater chain formation by analyzing their distribution and morphology. The western hemisphere of Mars was systematically mapped using Mars Orbiter Camera (MOC) images to generate ArcView™ Geographic Information System (GIS) coverages. All visible pit crater chains were mapped, including their orientations and associations with other structures. We found that pit chains commonly occur in areas that show regional extension or local fissuring. There is a strong correlation between pit chains and fault-bounded grabens. Frequently, there are transitions along strike from (1) visible faulting to (2) faults and pits to (3) pits alone. We performed a detailed quantitative analysis of pit crater morphology using MOC narrow angle images, Thermal Emission Imaging System (THEMIS) visual images, and Mars Orbiter Laser Altimeter (MOLA) data. This allowed us to determine a pattern of pit chain evolution and calculate pit depth, slope, and volume. Volumes of approximately 150 pits from five areas were calculated to determine volume size distribution and regional trends. The information collected in the study was then compared with non-Martian examples of pit chains and physical analog models. We evaluated the various mechanisms for pit chain development based on the data collected and conclude that dilational normal faulting and sub-vertical fissuring provide the simplest and most comprehensive mechanisms to explain the regional associations, detailed geometry, and progression of pit chain development.

Closure Report for Corrective Action Unit 544: Cellars, Mud Pits, and Oil Spills, Nevada National Security Site, Nevada, Revision 0

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

Mark Krauss and Catherine Birney

2011-05-01

This Closure Report (CR) presents information supporting the closure of Corrective Action Unit (CAU) 544: Cellars, Mud Pits, and Oil Spills, Nevada National Security Site, Nevada. This CR complies with the requirements of the Federal Facility Agreement and Consent Order that was agreed to by the State of Nevada; U.S. Department of Energy (DOE), Environmental Management; U.S. Department of Defense; and DOE, Legacy Management. The corrective action sites (CASs) within CAU 544 are located within Areas 2, 7, 9, 10, 12, 19, and 20 of the Nevada National Security Site. Corrective Action Unit 544 comprises the following CASs: • 02-37-08,more » Cellar & Mud Pit • 02-37-09, Cellar & Mud Pit • 07-09-01, Mud Pit • 09-09-46, U-9itsx20 PS #1A Mud Pit • 10-09-01, Mud Pit • 12-09-03, Mud Pit • 19-09-01, Mud Pits (2) • 19-09-03, Mud Pit • 19-09-04, Mud Pit • 19-25-01, Oil Spill • 19-99-06, Waste Spill • 20-09-01, Mud Pits (2) • 20-09-02, Mud Pit • 20-09-03, Mud Pit • 20-09-04, Mud Pits (2) • 20-09-06, Mud Pit • 20-09-07, Mud Pit • 20-09-10, Mud Pit • 20-25-04, Oil Spills • 20-25-05, Oil Spills The purpose of this CR is to provide documentation supporting the completed corrective actions and data confirming that the closure objectives for CASs within CAU 544 were met. To achieve this, the following actions were performed: • Review the current site conditions, including the concentration and extent of contamination. • Implement any corrective actions necessary to protect human health and the environment. • Properly dispose of corrective action and investigation wastes. • Document Notice of Completion and closure of CAU 544 issued by the Nevada Division of Environmental Protection.« less

Solution of heat removal from nuclear reactors by natural convection

NASA Astrophysics Data System (ADS)

Zitek, Pavel; Valenta, Vaclav

2014-03-01

This paper summarizes the basis for the solution of heat removal by natural convection from both conventional nuclear reactors and reactors with fuel flowing coolant (such as reactors with molten fluoride salts MSR).The possibility of intensification of heat removal through gas lift is focused on. It might be used in an MSR (Molten Salt Reactor) for cleaning the salt mixture of degassed fission products and therefore eliminating problems with iodine pitting. Heat removal by natural convection and its intensification increases significantly the safety of nuclear reactors. Simultaneously the heat removal also solves problems with lifetime of pumps in the primary circuit of high-temperature reactors.

A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed

USGS Publications Warehouse

Bukaveckas, P.A.; Likens, G.E.; Winter, T.C.; Buso, D.C.

1998-01-01

Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in estimating flux rates. Flux rates of dissolved Si and SO42- were calculated from 10 years of data (1981-1990) for the NW inlet and Outlet of Mirror Lake and for a 40-day period (March 22 to April 30, 1993) during which we augmented our routine (weekly) chemical monitoring with collection of daily samples. The time-averaging method yielded higher estimates of solute flux during high-flow periods if no chemistry samples were collected corresponding to peak discharge. Concentration-discharge relationships should be used to interpolate stream chemistry during changing flow conditions if chemical changes are large. Caution should be used in choosing the appropriate time-scale over which data are pooled to derive the concentration-discharge regressions because the model parameters (slope and intercept) were found to be sensitive to seasonal and inter-annual variation. Both methods approximated solute flux to within 2-10% for a range of solutes that were monitored during the intensive sampling period. Our results suggest that errors arising from interpolation of stream chemistry data are small compared with other sources of error in developing watershed mass balances.

Morphology and Evolution of Sublimation Pits on Pluto

NASA Astrophysics Data System (ADS)

Abu-Hashmeh, N.; Conrad, J. W.; Nimmo, F.; Moore, J. M.; Stern, A.; Olkin, C.; Weaver, H. A., Jr.; Ennico Smith, K.; Young, L. A.

2017-12-01

Pluto's Sputnik Planitia region hosts a geologically young surface of nitrogen ice that exhibits striking pitted terrain (Moore et al., Science 351, 2016). These pits are most likely formed by sublimation due to incident sunlight, similar to the southern polar cap of Mars (Byrne and Ingersoll, Science 299, 2003); however, their evolution over time has resulted in unique morphological characteristics. Motivated by this, we used the high-resolution mosaic strips captured by New Horizons' Long Range Reconnaissance Imager (LORRI) to map sublimation pits in the southernmost region of Sputnik Planitia. Statistical data shows pit orientations appearing North-South dominant; their morphology also indicates extensional evolution along the major axis caused by further sublimation and contact-coalescence processes. Qualitative analysis of the region yielded indications of an evolutionary path for individual pits that coalesce into each other and exhibit an elongated end-stage. Additionally, densely-pitted regions generally appear to correlate with regions containing longer pits, implying that coalescence may be an important process for elongation. We also model the evolution geometry through competing effects of diffusion (viscous relaxation) and retreat (sublimation) (Buhler and Ingersoll, LPSC Abstract #1746, 2017). The model demonstrates single-pit and coalescing-pit evolutions that influence overall length, as well as a potential ability for the pit center to move in space while the pit morphology evolves.

Monte Carlo simulation of a near-continuum shock-shock interaction problem

NASA Technical Reports Server (NTRS)

Carlson, Ann B.; Wilmoth, Richard G.

1992-01-01

A complex shock interaction is calculated with direct simulation Monte Carlo (DSMC). The calculation is performed for the near-continuum flow produced when an incident shock impinges on the bow shock of a 0.1 in. radius cowl lip for freestream conditions of approximately Mach 15 and 35 km altitude. Solutions are presented both for a full finite-rate chemistry calculation and for a case with chemical reactions suppressed. In each case, both the undisturbed flow about the cowl lip and the full shock interaction flowfields are calculated. Good agreement has been obtained between the no-chemistry simulation of the undisturbed flow and a perfect gas solution obtained with the viscous shock-layer method. Large differences in calculated surface properties when different chemical models are used demonstrate the necessity of adequately representing the chemistry when making surface property predictions. Preliminary grid refinement studies make it possible to estimate the accuracy of the solutions.

Initation of pitting corrosion in martensitic stainless steels. [17-4PH; 13-8Mo; Custom 450

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

Cieslak, W.R.; Semarge, R.E.; Bovard, F.S.

1986-01-01

The form of localized corrosion known as pitting often initiates preferentially at microstructural inhomogeneities. The pit initiation resistance, therefore, is controlled by the characteristics of the initiation sites, rather than by the bulk material composition. This investigation correlates the pit initiation resistance, as measured by critical pitting potentials, with preferred pit initiation sites for 3 martensitic stainless steels. Pit initiation sites are determined by secondary electron (SE) and backscattered electron (BSE) imaging and energy dispersive and wavelength dispersive spectrometries (EDS and WDS) with a scalling electron microscope (SEM) and an electron probe microanalyzer (EPMA).

Burn Pit Emissions Exposure and Respiratory and Cardiovascular Conditions Among Airborne Hazards and Open Burn Pit Registry Participants.

PubMed

Liu, Jason; Lezama, Nicholas; Gasper, Joseph; Kawata, Jennifer; Morley, Sybil; Helmer, Drew; Ciminera, Paul

2016-07-01

The aim of this study was to determine how burn pit emissions exposure is associated with the incidence of respiratory and cardiovascular conditions. We examined the associations between assumed geographic and self-reported burn pit emissions exposure and respiratory and cardiovascular outcomes in participants of the Airborne Hazards and Open Burn Pit Registry. We found significant dose-response associations for higher risk of self-reported emphysema, chronic bronchitis, or chronic obstructive pulmonary disease with increased days of deployment within 2 miles of selected burn pits (P-trend = 0.01) and self-reported burn pit smoke exposure (P-trend = 0.0005). We found associations between burn pit emissions exposure and higher incidence of post-deployment self-reported respiratory and cardiovascular conditions, but these findings should be interpreted with caution because the surrogate measurements of burn pit emissions exposure in this analysis may not reflect individual exposure levels.

Pitted terrains on (1) Ceres and implications for shallow subsurface volatile distribution

PubMed Central

Platz, T.; Schorghofer, N.; Prettyman, T. H.; De Sanctis, M. C.; Crown, D. A.; Schmedemann, N.; Neesemann, A.; Kneissl, T.; Marchi, S.; Schenk, P. M.; Bland, M. T.; Schmidt, B. E.; Hughson, K. H. G.; Tosi, F.; Zambon, F.; Mest, S. C.; Yingst, R. A.; Williams, D. A.; Russell, C. T.; Raymond, C. A.

2017-01-01

Abstract Prior to the arrival of the Dawn spacecraft at Ceres, the dwarf planet was anticipated to be ice‐rich. Searches for morphological features related to ice have been ongoing during Dawn's mission at Ceres. Here we report the identification of pitted terrains associated with fresh Cerean impact craters. The Cerean pitted terrains exhibit strong morphological similarities to pitted materials previously identified on Mars (where ice is implicated in pit development) and Vesta (where the presence of ice is debated). We employ numerical models to investigate the formation of pitted materials on Ceres and discuss the relative importance of water ice and other volatiles in pit development there. We conclude that water ice likely plays an important role in pit development on Ceres. Similar pitted terrains may be common in the asteroid belt and may be of interest to future missions motivated by both astrobiology and in situ resource utilization. PMID:28989206

Pitted terrains on (1) Ceres and implications for shallow subsurface volatile distribution.

PubMed

Sizemore, H G; Platz, T; Schorghofer, N; Prettyman, T H; De Sanctis, M C; Crown, D A; Schmedemann, N; Neesemann, A; Kneissl, T; Marchi, S; Schenk, P M; Bland, M T; Schmidt, B E; Hughson, K H G; Tosi, F; Zambon, F; Mest, S C; Yingst, R A; Williams, D A; Russell, C T; Raymond, C A

2017-07-16

Prior to the arrival of the Dawn spacecraft at Ceres, the dwarf planet was anticipated to be ice-rich. Searches for morphological features related to ice have been ongoing during Dawn's mission at Ceres. Here we report the identification of pitted terrains associated with fresh Cerean impact craters. The Cerean pitted terrains exhibit strong morphological similarities to pitted materials previously identified on Mars (where ice is implicated in pit development) and Vesta (where the presence of ice is debated). We employ numerical models to investigate the formation of pitted materials on Ceres and discuss the relative importance of water ice and other volatiles in pit development there. We conclude that water ice likely plays an important role in pit development on Ceres. Similar pitted terrains may be common in the asteroid belt and may be of interest to future missions motivated by both astrobiology and in situ resource utilization.

Pitted terrains on (1) Ceres and implications for shallow subsurface volatile distribution

USGS Publications Warehouse

Sizemore, H.G.; Platz, Thomas; Schorghofer, Norbert; Prettyman, Thomas; De Sanctis, Maria Christina; Crown, David A.; Schmedemann, Nico; Nessemann, Andeas; Kneissl, Thomas; Simone Marchi,; Schenk, Paul M.; Bland, Michael T.; Schmidt, B.E.; Hughson, Kynan H.G.; Tosi, F.; Zambon, F; Mest, S.C.; Yingst, R.A.; Williams, D.A.; Russell, C.T.; Raymond, C.A.

2017-01-01

Prior to the arrival of the Dawn spacecraft at Ceres, the dwarf planet was anticipated to be ice-rich. Searches for morphological features related to ice have been ongoing during Dawn's mission at Ceres. Here we report the identification of pitted terrains associated with fresh Cerean impact craters. The Cerean pitted terrains exhibit strong morphological similarities to pitted materials previously identified on Mars (where ice is implicated in pit development) and Vesta (where the presence of ice is debated). We employ numerical models to investigate the formation of pitted materials on Ceres and discuss the relative importance of water ice and other volatiles in pit development there. We conclude that water ice likely plays an important role in pit development on Ceres. Similar pitted terrains may be common in the asteroid belt and may be of interest to future missions motivated by both astrobiology and in situ resource utilization.

Force-displacement measurements of earlywood bordered pits using a mesomechanical tester.

PubMed

Zelinka, Samuel L; Bourne, Keith J; Hermanson, John C; Glass, Samuel V; Costa, Adriana; Wiedenhoeft, Alex C

2015-10-01

The elastic properties of pit membranes are reported to have important implications in understanding air-seeding phenomena in gymnosperms, and pit aspiration plays a large role in wood technological applications such as wood drying and preservative treatment. Here we present force-displacement measurements for pit membranes of circular bordered pits, collected on a mesomechanical testing system. The system consists of a quartz microprobe attached to a microforce sensor that is positioned and advanced with a micromanipulator mounted on an inverted microscope. Membrane displacement is measured from digital image analysis. Unaspirated pits from earlywood of never-dried wood of Larix and Pinus and aspirated pits from earlywood of dried wood of Larix were tested to generate force-displacement curves up to the point of membrane failure. Two failure modes were observed: rupture or tearing of the pit membrane by the microprobe tip, and the stretching of the pit membrane until the torus was forced out of the pit chamber through the pit aperture without rupture, a condition we refer to as torus prolapse. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Evaluation of on-line chelant addition to PWR steam generators. Steam generator cleaning project

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

Tvedt, T.J.; Wallace, S.L.; Griffin, F. Jr.

1983-09-01

The investigation of chelating agents for continuous water treatment of secondary loops of PWR steam generators were conducted in two general areas: the study of the chemistry of chelating agents and the study of materials compatability with chelating agents. The thermostability of both EDTA and HEDTA metal chelates in All Volatile Treatment (AVT) water chemistry were shown to be greater than or equal to the thermostability of EDTA metal chelates in phosphate-sulfite water chemistry. HEDTA metal chelates were shown to have a much greater stability than EDTA metal chelates. Using samples taken from the EDTA metal chelate thermostability study andmore » from the Commonwealth Research Corporation (CRC) model steam generators (MSG), EDTA decomposition products were determined. Active metal surfaces were shown to become passivated when exposed to EDTA and HEDTA concentrations as high as 0.1% w/w in AVT. Trace amounts of iron in the water were found to increase the rate of passivation. Material balance and visual inspection data from CRC model steam generators showed that metal was transported through and cleaned from the MSG's. The Inconel 600 tubes of the salt water fouled model steam generators experienced pitting corrosion. Results of this study demonstrates the feasibility of EDTA as an on-line water treatment additive to maintain nuclear steam generators in a clean condition.« less

An Investigation of the Effects of Relevant Samples and a Comparison of Verification versus Discovery Based Lab Design

ERIC Educational Resources Information Center

Rieben, James C., Jr.

2010-01-01

This study focuses on the effects of relevance and lab design on student learning within the chemistry laboratory environment. A general chemistry conductivity of solutions experiment and an upper level organic chemistry cellulose regeneration experiment were employed. In the conductivity experiment, the two main variables studied were the effect…

An Introduction to the Fundamentals of Chemistry for the Marine Engineer - An Audio-Tutorial Correspondence Course (CH-1C).

ERIC Educational Resources Information Center

Schlenker, Richard M.

This document provides a study guide for a three-credit-hour fundamentals of chemistry course for marine engineer majors. The course is composed of 17 minicourses including: chemical reactions, atomic theory, solutions, corrosion, organic chemistry, water pollution, metric system, and remedial mathematics skills. Course grading, objectives,…

Analysis of Copper-Bearing Rocks and Minerals for Their Metal Content Using Visible Spectroscopy: A First Year Chemistry Laboratory Exploration

ERIC Educational Resources Information Center

Bopegedera, A. M. R. P.

2016-01-01

General chemistry and introductory chemistry students were presented with a laboratory exploration for the determination of the mass percent of copper in rock and mineral samples. They worked independently in the laboratory, which involved multiple lab (pipetting, preparing standard solutions by quantitative dilution, recording visible spectra…

Least tern and piping plover nesting at sand pits in Nebraska

USGS Publications Warehouse

Sidle, John G.; Kirsch, E.M.

1993-01-01

Endangered Least Terns (Sterna antillarum) and threatened Piping Plovers (Charadrius melodus) nest at commercial sand and gravel mining operations (sand pits) along the Platte River system in Nebraska. Sandbar habitat has been disappearing since the early 1900's along the Platte River system, but numbers of sand pits have increased. We hypothesized that birds would more fully utilize sand pits where suitable sandbar habitat was limited. We inventoried sand pits and censused terns and plovers on both habitats along the Loup River, part of the North Loup River, and most of the Platte River during 1988-1991. Using aircraft, we also quantified features of suitable sand pits present on the central Platte in 1988 and lower Platte in 1990, and related features to abundance and presence of birds. We found 225 sand pits of which 78 were suitable and 187 were unsuitable for nesting. Along the central Platte, where sandbar habitat is severely degraded, birds nested at 81% of the suitable sand pits (N = 32) at least once during 1988-1991, and most birds (61-94%) nested on sand pits. Along the lower Platte, where both sandbar and sand pit habitat are plentiful, birds nested at 60% of the suitable sand pits (N = 35) at least once during 1988-1991, and most birds (60-86%) nested on sandbars. Numbers of terns and plovers were more weakly correlated with features of sand pits on the central Platte than on the lower Platte. Least Terns and Piping Plovers seem to use more of the suitable sand pit habitat on the central Platte than on the lower Platte. Sand pits probably have influenced the birds' distribution by providing alternative nesting habitat along rivers where suitable sandbars are rare or absent.

Efficacy of UV-Pit-light traps for discerning micro-habitat-specific beetle and ant species related with different oil palm age stands and tropical annual seasons for accurate ecology and diversity interpretations

NASA Astrophysics Data System (ADS)

Ahmad Bukhary, A. K.; Ruslan, M. Y.; Mohd. Fauzi, M. M.; Nicholas, S.; Muhamad Fahmi, M. H.; Izfa Riza, H.; Idris, A. B.

2015-09-01

A newly innovated and efficient UV-Pit-light Trap is described and the results of the experiments on its efficacy that were carried out within different oil palm age stands of the year 2013 were evaluated and compared with previous study year of 2010, with out the implementation of the UV-Pit-light Trap. In 2013 the UV-Pit-light Traps, the Malaise Traps, and the Pit-fall Traps were employed, while in 2010, the conventional canopy-height UV-Light Traps, Malaise Traps, and the Pit-fall Traps were employed. The UV-Pit-light traps caught more beetle and ant families, morpho-species, and individuals per species compared with the passive Pit-fall traps. The UV-Pit-light Trap targets different subsets of the oil palm beetles and ants' communities, specifying on epigaeic-related micro-habitats, with different oil palm age stands have different compositions of micro-habitats. The UV-Pit-light Traps have the dual quality for satisfying both the biological and statistical data requirements and evaluations. There were no significant difference between the UV-Pit-light Traps and the passive Pit-fall Traps, while the trapping difference with the Malaise traps for different seasons of the year 2013. The UV-Pit-light Traps and the Malaise Traps were complementary to each other, detecting the activities of beetles and ants around the epigaeic-related micro-habitats or having active flight activities respectively according to annual seasons. The UV-Pit-light Trap is an oil-palm specific type of passive trapping system, focusing on the insect species dwelling the upper-ground/epigaeic micro-habitats.

Nanoscale dissolution and growth on anhydrite cleavage faces

NASA Astrophysics Data System (ADS)

Pina, Carlos M.

2009-12-01

In situ atomic force microscopy (AFM) was used to study the molecular-scale reactivity of anhydrite (1 0 0), (0 1 0), and (0 0 1) faces exposed to water and CaSO 4 aqueous solutions at room temperature. In pure water, dissolution occurs by step retreat and etch pit nucleation and growth. Both the kinetics of the step retreat and the shape of the etch pits are surface-specific and crystallographically controlled. In CaSO 4 aqueous solutions with concentrations ranging from 0.030 mol/l to 0.075 mol/l, the growth kinetics on anhydrite (1 0 0) and (0 1 0) faces was studied. Growth is also strongly controlled by crystallographic constraints and occurs exclusively from pre-existing step edges by highly anisotropic spreading of monolayers (˜3.5 Å in height). The AFM observations demonstrate that monolayer growth can occur on anhydrite (0 1 0) and (1 0 0) faces even from slightly supersaturated solutions. In addition, the comparison of the step kinetics on anhydrite faces shows that the mechanisms of step dissolution and growth are essentially the same, with the direction of migration of crystal building units being reversed at the anhydrite saturation point. Moreover, the analysis of both high resolution AFM images and lateral force microscopy (LFM) images confirms that the newly-formed monolayers are anhydrite growing in structural continuity with the original (1 0 0) and (0 1 0) surfaces. However, the formation of the first monolayers is metastable and two-dimensional nucleation and further multilayer growth of anhydrite are strongly inhibited even at high supersaturations.

A comparative study of the in vitro corrosion behavior and cytotoxicity of a superferritic stainless steel, a Ti-13Nb-13Zr alloy, and an austenitic stainless steel in Hank's solution.

PubMed

Assis, S L; Rogero, S O; Antunes, R A; Padilha, A F; Costa, I

2005-04-01

In this study, the in vitro corrosion resistance of a superferritic stainless steel in naturally aerated Hank's solution at 37 degrees C has been determined to evaluate the steel for use as a biomaterial. The potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS) were used to determine the corrosion resistance. The polarization results showed very low current densities at the corrosion potential and electrochemical behavior typical of passive metals. At potentials above 0.75 V (SCE), and up to that of the oxygen evolution reaction, the superferritic steel exhibited transpassive behavior followed by secondary passivation. The superferritic stainless steel exhibited high pitting resistance in Hank's solution. This steel did not reveal pits even after polarization to 3000 mV (SCE). The EIS results indicated high impedance values at low frequencies, supporting the results obtained from the polarization measurements. The results obtained for the superferritic steel have been compared with those of the Ti-13Nb-13Zr alloy and an austenitic stainless steel, as Ti alloys are well known for their high corrosion resistance and biocompatibility, and the austenitic stainless steel is widely used as an implant material. The cytotoxicity tests indicated that the superferritic steel, the austenitic steel, and the Ti-13Nb-13Zr alloy were not toxic. Based on corrosion resistance and cytotoxicity results, the superferritic stainless steel can be considered as a potential biomaterial. (c) 2005 Wiley Periodicals, Inc.

Microstructure Evolution and the Resulted Influence on Localized Corrosion in Al-Zn-Mg-Cu Alloy during Non-Isothermal Ageing.

PubMed

Chen, Jun-Zhou; Li, Guo-Ai; Cai, Xin; Jiang, Jian-Tang; Shao, Wen-Zhu; Yang, Li; Zhen, Liang

2018-05-03

A non-isothermal ageing process was proposed for an Al-Zn-Mg-Cu alloy aiming to accommodate the slow heating/cooling procedure during the ageing of large components. The evolution of microstructure and microchemistry was analyzed by using transmission electron microscopy, high-angle annular dark field imaging, and energy dispersive spectrometry. The age-hardening of the alloy was examined to evaluate the strengthening behavior during the non-isothermal process. The corrosion behavior was investigated via observing the specimens immersed in EXCO solution (solution for Exfoliation Corrosion Susceptibility test in 2xxx and 7xxx series aluminum alloys, referring ASTM G34-01). Secondary precipitation was observed during the cooling stage, leading to increased precipitate number density. The distribution of grain boundary precipitates transits from discontinuous to continuous at the cooling stage, due to the secondary precipitation’s linking-up effect. The solutes’ enrichment on grain boundary precipitates and the depletion in precipitate-free zones develops during the heating procedure, but remains invariable during the cooling procedure. The corrosion in NIA (Non-isothermal Ageing) treated specimens initiates from pitting and then transits to intergranular corrosion and exfoliation corrosion. The transition from pitting to intergranular corrosion is very slow for specimens heated to 190 °C, but accelerates slightly as the cooling procedure proceeds. The transition to exfoliation corrosion is observed to be quite slow in all specimens in non-isothermal aged to over-aged condition, suggesting a corrosion resistance comparable to that of RRA condition.

One dimensional Linescan x-ray detection of pits in fresh cherries

USDA-ARS?s Scientific Manuscript database

The presence of pits in processed cherries is a concern for both processors and consumers, in many cases causing injury and potential lawsuits. While machines used for pitting cherries are extremely efficient, if one or more plungers in a pitting head become misaligned, a large number of pits may p...

Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse.

PubMed

Vincent, Jean-Baptiste; Bodewits, Dennis; Besse, Sébastien; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F; Auger, Anne-Thérèse; Barucci, M Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Capanna, Claire; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; El-Maarry, Mohamed Ramy; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Giacomini, Lorenza; Groussin, Olivier; Guilbert-Lepoutre, Aurélie; Gutierrez-Marques, P; Gutiérrez, Pedro J; Güttler, Carsten; Hoekzema, Nick; Höfner, Sebastian; Hviid, Stubbe F; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M; Lazzarin, Monica; Lee, Vicky; Leyrat, Cédric; Lin, Zhong-Yi; Lopez Moreno, Josè J; Lowry, Stephen; Magrin, Sara; Maquet, Lucie; Marchi, Simone; Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Preusker, Frank; Scholten, Frank; Thomas, Nicolas; Toth, Imre; Tubiana, Cecilia

2015-07-02

Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments and models cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts. Alternative mechanisms like explosive activity have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface.

Beach Erosional Hot Spots: Types, Causes, and Solutions

DTIC Science & Technology

2001-09-01

Pope, and McClung (1999) showed that variable erosion rates along a beach nourishment project on Presque Isle , Pennsylvania (Lake Erie ) were related to...and McClung, J. K. (1999). “Coastal response to a detached breakwater system: Presque Isle , Erie , PA, U.S.A,” Proc. Coastal Sediments ’99, ASCE...borrow pits located too close to shore at Grand Isle , LA. The resultant cuspate shoreline was subsequently predicted by refraction analysis

Materials Evaluation. Part II. Development of Corrosion Inhibitors.

DTIC Science & Technology

1979-09-01

concentration upon the pitting behavior of Al 7075-T6 in an inhibited solution 46 24 Polarization behavior of 4340 steel 47 25 Polarization behavior of copper ...However, this combination itself was not effective in inhibiting the corrosion of high- strength aluminum alloys, copper , and other alloys used in...79 JUNE MONTHLY COMPOSITE COMPLETE ANALYSIS (Results expressed in milligrams per liter) Calcium Ca 61.60 Magnesium Mg 7.00 Sulfates S04 55.00 Chlorides

Sanitation practices and perceptions in Kakuma refugee camp, Kenya: Comparing the status quo with a novel service-based approach

PubMed Central

Nyoka, Raymond; Foote, Andrew D.; Woods, Emily; Lokey, Hana; O’Reilly, Ciara E.; Magumba, Fred; Okello, Patrick; Mintz, Eric D.; Marano, Nina

2017-01-01

Globally, an estimated 2.5 billion people lack access to improved sanitation. Unimproved sanitation increases the risk of morbidity and mortality, especially in protracted refugee situations where sanitation is based on pit latrine use. Once the pit is full, waste remains in the pit, necessitating the construction of a new latrine, straining available land and funding resources. A viable, sustainable solution is needed. This study used qualitative and quantitative methods to design, implement, and pilot a novel sanitation system in Kakuma refugee camp, Kenya. An initial round of 12 pre-implementation focus group discussions (FGDs) were conducted with Dinka and Somali residents to understand sanitation practices, perceptions, and needs. FGDs and a supplementary pre-implementation survey informed the development of an innovative sanitation management system that incorporated the provision of urine and liquid-diverting toilets, which separate urine and fecal waste, and a service-based sanitation system that included weekly waste collection. The new system was implemented on a pilot scale for 6 weeks. During the implementation, bi-weekly surveys were administered in each study household to monitor user perceptions and challenges. At the end of the pilot, the sanitation system was assessed using a second round of four post-implementation FGDs. Those who piloted the new sanitation system reported high levels of user satisfaction. Reported benefits included odor reduction, insect/pest reduction, the sitting design, the appropriateness for special populations, and waste collection. However, urine and liquid diversion presented a challenge for users who perform anal washing and for women who had experienced female genital mutilation. Refugee populations are often culturally and ethnically diverse. Using residents’ input to inform the development of sanitation solutions can increase user acceptability and provide opportunities to improve sanitation system designs based on specific needs. PMID:28704504

The Effects of Hot Corrosion Pits on the Fatigue Resistance of a Disk Superalloy

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Telesman, Jack; Hazel, Brian; Mourer, David P.

2009-01-01

The effects of hot corrosion pits on low cycle fatigue life and failure modes of the disk superalloy ME3 were investigated. Low cycle fatigue specimens were subjected to hot corrosion exposures producing pits, then tested at low and high temperatures. Fatigue lives and failure initiation points were compared to those of specimens without corrosion pits. Several tests were interrupted to estimate the fraction of fatigue life that fatigue cracks initiated at pits. Corrosion pits significantly reduced fatigue life by 60 to 98 percent. Fatigue cracks initiated at a very small fraction of life for high temperature tests, but initiated at higher fractions in tests at low temperature. Critical pit sizes required to promote fatigue cracking were estimated, based on measurements of pits initiating cracks on fracture surfaces.

Environmental-Induced Damage in Tin (Sn) and Aluminum (Al) Alloys

NASA Astrophysics Data System (ADS)

Vallabhaneni, Venkata Sathya Sai Renuka

Sn and Al alloys are widely used in various industries. Environmental-induced damage resulting in whiskering in Sn and corrosion in Al account for numerous failures globally every year. Therefore, for designing materials that can better withstand these failures, a comprehensive study on the characterization of the damage is necessary. This research implements advanced characterization techniques to study the above-mentioned environmental-induced damage in Sn and Al alloys. Tin based films are known to be susceptible to whisker growth resulting in numerous failures. While the mechanisms and factors affecting whisker growth have been studied extensively, not much has been reported on the mechanical properties of tin whiskers themselves. This study focuses on the tensile behavior of tin whiskers. Tensile tests of whiskers were conducted in situ a dual beam focused ion beam (FIB) with a scanning electron microscope (SEM) using a micro electro-mechanical system (MEMS) tensile testing stage. The deformation mechanisms of whiskers were analyzed using transmission electron microscopy (TEM). Due to the heterogenous nature of the microstructure of Al 7075, it is susceptible to corrosion forming corrosion products and pits. These can be sites for cracks nucleation and propagation resulting in stress corrosion cracking (SCC). Therefore, complete understanding of the corrosion damaged region and its effect on the strength of the alloy is necessary. Several studies have been performed to visualize pits and understand their effect on the mechanical performance of Al alloys using two-dimensional (2D) approaches which are often inadequate. To get a thorough understanding of the pits, it is necessary for three-dimensional (3D) studies. In this study, Al 7075 alloys were corroded in 3.5 wt.% NaCl solution and X-ray tomography was used to obtain the 3D microstructure of pits enabling the quantification of their dimensions accurately. Furthermore, microstructure and mechanical property correlations helped in a better understanding of the effect of corrosion. Apart from the pits, a surface corrosion layer also forms on Al. A subsurface damage layer has also been identified that forms due to the aggressive nature of NaCl. Energy dispersive X-ray spectroscopy (EDX) and nanoindentation helped in identifying this region and understanding the variation in properties.

Pit-1/growth hormone factor 1 splice variant expression in the rhesus monkey pituitary gland and the rhesus and human placenta.

PubMed

Schanke, J T; Conwell, C M; Durning, M; Fisher, J M; Golos, T G

1997-03-01

We have examined the expression of Pit-1 messenger RNA (mRNA) splice variants in the nonhuman primate pituitary and in rhesus and human placenta. Full-length complementary DNAs (cDNAs) representing Pit-1 and the Pit-1 beta splice variants were cloned from a rhesus monkey pituitary cDNA library and were readily detectable by RT-PCR with rhesus pituitary gland RNA. The Pit-1T variant previously reported in mouse pituitary tumor cell lines was not detectable in normal rhesus pituitary tissue, although two novel splice variants were detected. A cDNA approximating the rat Pit-1 delta 4 variant was cloned but coded for a truncated and presumably nonfunctional protein. Only by using a nested RT-PCR approach were Pit-1 and Pit-1 beta variants consistently detectable in both human and rhesus placental tissue. The Pit-1 beta variant mRNA was not detectable in JEG-3 choriocarcinoma cells unless the cells were stimulated with 8-Br-cAMP. Immunoblot studies with nuclear extracts from primary rhesus syncytiotrophoblast cultures or JEG-3 choriocarcinoma cells indicated that although mRNA levels were very low, Pit-1 protein was detectable in differentiated cytotrophoblasts, and levels increased after treatment with 8-Br-cAMP. Two major species of Pit-1 protein were detected that corresponded to the two major bands in rat pituitary GH3 cell nuclear extracts. Low levels of slightly larger bands also were seen, which may represent Pit-1 beta protein or phosphorylated species. We conclude that Pit-1 splice variants expressed in the primate pituitary gland differ from those in the rodent gland and that the Pit-1 and Pit-1 beta mRNAs expressed in the placenta give rise to a pattern of protein expression similar to that seen in pituitary cells, which is inducible by treatment with 8-Br-cAMP.

Advantages and limitations for users of double pit pour-flush latrines: a qualitative study in rural Bangladesh.

PubMed

Hussain, Faruqe; Clasen, Thomas; Akter, Shahinoor; Bawel, Victoria; Luby, Stephen P; Leontsini, Elli; Unicomb, Leanne; Barua, Milan Kanti; Thomas, Brittany; Winch, Peter J

2017-05-25

In rural Bangladesh, India and elsewhere, pour-flush pit latrines are the most common sanitation system. When a single pit latrine becomes full, users must empty it themselves and risk exposure to fresh feces, pay an emptying service to remove pit contents or build a new latrine. Double pit pour-flush latrines may serve as a long-term sanitation option including high water table areas because the pits do not need to be emptied immediately and the excreta decomposes into reusable soil. Double pit pour-flush latrines were implemented in rural Bangladesh for 'hardcore poor' households by a national NGO, BRAC. We conducted interviews, focus groups, and spot checks in two low-income, rural areas of Bangladesh to explore the advantages and limitations of using double pit latrines compared to single pit latrines. The rural households accepted the double pit pour-flush latrine model and considered it feasible to use and maintain. This latrine design increased accessibility of a sanitation facility for these low-income residents and provided privacy, convenience and comfort, compared to open defecation. Although a double pit latrine is more costly and requires more space than a single pit latrine the households perceived this sanitation system to save resources, because households did not need to hire service workers to empty pits or remove decomposed contents themselves. In addition, the excreta decomposition process produced a reusable soil product that some households used in homestead gardening. The durability of the latrine superstructures was a problem, as most of the bamboo-pole superstructure broke after 6-18 months of use. Double pit pour-flush latrines are a long-term improved sanitation option that offers users several important advantages over single pit pour-flush latrines like in rural Bangladesh which can also be used in areas with high water table. Further research can provide an understanding of the comparative health impacts and effectiveness of the model in preventing human excreta from entering the environment.

Evaluating the effects of variable water chemistry on bacterial transport during infiltration.

PubMed

Zhang, Haibo; Nordin, Nahjan Amer; Olson, Mira S

2013-07-01

Bacterial infiltration through the subsurface has been studied experimentally under different conditions of interest and is dependent on a variety of physical, chemical and biological factors. However, most bacterial transport studies fail to adequately represent the complex processes occurring in natural systems. Bacteria are frequently detected in stormwater runoff, and may present risk of microbial contamination during stormwater recharge into groundwater. Mixing of stormwater runoff with groundwater during infiltration results in changes in local solution chemistry, which may lead to changes in both bacterial and collector surface properties and subsequent bacterial attachment rates. This study focuses on quantifying changes in bacterial transport behavior under variable solution chemistry, and on comparing the influences of chemical variability and physical variability on bacterial attachment rates. Bacterial attachment rate at the soil-water interface was predicted analytically using a combined rate equation, which varies temporally and spatially with respect to changes in solution chemistry. Two-phase Monte Carlo analysis was conducted and an overall input-output correlation coefficient was calculated to quantitatively describe the importance of physiochemical variation on the estimates of attachment rate. Among physical variables, soil particle size has the highest correlation coefficient, followed by porosity of the soil media, bacterial size and flow velocity. Among chemical variables, ionic strength has the highest correlation coefficient. A semi-reactive microbial transport model was developed within HP1 (HYDRUS1D-PHREEQC) and applied to column transport experiments with constant and variable solution chemistries. Bacterial attachment rates varied from 9.10×10(-3)min(-1) to 3.71×10(-3)min(-1) due to mixing of synthetic stormwater (SSW) with artificial groundwater (AGW), while bacterial attachment remained constant at 9.10×10(-3)min(-1) in a constant solution chemistry (AGW only). The model matched observed bacterial breakthrough curves well. Although limitations exist in the application of a semi-reactive microbial transport model, this method represents one step towards a more realistic model of bacterial transport in complex microbial-water-soil systems. Copyright © 2013 Elsevier B.V. All rights reserved.

Chemistry Division. Quarterly progress report for period ending June 30, 1949

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

Not Available

1949-09-14

Progress reports are presented for the following tasks: (1) nuclear and chemical properties of heavy elements (solution chemistry, phase rule studies); (2) nuclear and chemical properties of elements in the fission product region; (3) general nuclear chemistry; (4) radio-organic chemistry; (5) chemistry of separations processes; (6) physical chemistry and chemical physics; (7) radiation chemistry; (8) physical measurements and instrumentation; and (9) analytical chemistry. The program of the chemistry division is divided into two efforts of approximately equal weight with respect to number of personnel, chemical research, and analytical service for the Laboratory. The various research problems fall into the followingmore » classifications: (1) chemical separation processes for isolation and recovery of fissionable material, production of radioisotopes, and military applications; (2) reactor development; and (3) fundamental research.« less

Pierre-Joseph Macquer: Chemistry in the French Enlightenment.

PubMed

Lehman, Christine

2014-01-01

Despite recent studies of chemistry courses and of academic research at the beginning of the eighteenth century, the perception of chemistry in the French Enlightenment has often been overshadowed by Lavoisier's works. This article proposes three specific case studies selected from Pierre Joseph Macquer's (1718-84) rich career to show the continuous evolution of chemistry throughout the century: medicinal chemistry through the application of the Comte de La Garaye's metallic salt solutions, the emergence of industrial chemistry through a few of Macquer's evaluations at the Bureau du Commerce, and finally communal academic research through the experiments on diamonds using Tschirnhaus's lens. These examples attempt to illustrate the innovative, creative, dynamic, multicultural, and multifaceted chemistry of the Enlightenment.

Involvement of the pituitary-specific transcription factor pit-1 in somatolactotrope cell growth and death: an approach using dominant-negative pit-1 mutants.

PubMed

Pellegrini, Isabelle; Roche, Cathy; Quentien, Marie-Helene; Ferrand, Mireille; Gunz, Ginette; Thirion, Sylvie; Bagnis, Claude; Enjalbert, Alain; Franc, Jean-Louis

2006-12-01

The anterior pituitary-specific transcription factor Pit-1 was initially identified and cloned as a transactivator of the prolactin (PRL) and GH genes and later as a regulator of the TSHb gene. It was found to be a major developmental regulator, because natural Pit-1 gene mutations cause a dwarf phenotype in mice and cause combined pituitary hormone deficiency associated with pituitary hypoplasia in humans. To further investigate the growth-promoting effects of Pit-1, we used a strategy based on the use of dominant-negative Pit-1 mutants as an alternative means of inactivating endogenous Pit-1 functions. R271W, a Pit-1 mutant identified in one allele in patients with severe combined pituitary hormone deficiency, and Pit-1Delta1-123, a deletion mutant in which only the DNA binding domain of Pit-1 is conserved, were generated, and their ability to abolish the effects of the endogenous native Pit-1 in the differentiated proliferating somatolactotrope GH4C1 cell line was investigated. Enforced expression of the dominant-negative mutants in GH4C1 cells using recombinant lentiviral vectors decreased the levels of expression of known Pit-1 target genes such as PRL and GH, abolished the hormone release, and reduced cell viability by decreasing the growth rate and inducing apoptosis via a caspase-independent pathway. These results show for the first time that the growth-promoting effects of Pit-1 are at least partly due to the fact that this transcription factor prevents apoptotic cell death.

Multi-Scale Modeling of the Gamma Radiolysis of Nitrate Solutions.

PubMed

Horne, Gregory P; Donoclift, Thomas A; Sims, Howard E; Orr, Robin M; Pimblott, Simon M

2016-11-17

A multiscale modeling approach has been developed for the extended time scale long-term radiolysis of aqueous systems. The approach uses a combination of stochastic track structure and track chemistry as well as deterministic homogeneous chemistry techniques and involves four key stages: radiation track structure simulation, the subsequent physicochemical processes, nonhomogeneous diffusion-reaction kinetic evolution, and homogeneous bulk chemistry modeling. The first three components model the physical and chemical evolution of an isolated radiation chemical track and provide radiolysis yields, within the extremely low dose isolated track paradigm, as the input parameters for a bulk deterministic chemistry model. This approach to radiation chemical modeling has been tested by comparison with the experimentally observed yield of nitrite from the gamma radiolysis of sodium nitrate solutions. This is a complex radiation chemical system which is strongly dependent on secondary reaction processes. The concentration of nitrite is not just dependent upon the evolution of radiation track chemistry and the scavenging of the hydrated electron and its precursors but also on the subsequent reactions of the products of these scavenging reactions with other water radiolysis products. Without the inclusion of intratrack chemistry, the deterministic component of the multiscale model is unable to correctly predict experimental data, highlighting the importance of intratrack radiation chemistry in the chemical evolution of the irradiated system.

A Study of the Liquid-Liquid Partitioning Process Using Reverse-Phase Liquid Chromatography: An Undergraduate Analytical Chemistry Experiment.

ERIC Educational Resources Information Center

Lochmuller, C. H.; And Others

1980-01-01

Presents an undergraduate analytical chemistry experiment that promotes an interpretation of the molecular aspects of solute partitioning, enhancing student understanding of separation science and liquid chromatography. (CS)

Electrolyte Solutions and Specific Ion Effects on Interfaces

ERIC Educational Resources Information Center

Friedman, Ran

2013-01-01

Introductory general and physical chemistry courses often deal with colligative properties of solutions and do not discuss nonideal solutions in detail. Yet, a growing body of evidence reveals that even at physiological concentrations electrolyte solutions cannot be treated as ideal when a charged or partially charged solute (such as a protein) is…

Force-displacement measurements of earlywood bordered pits using a mesomechanical tester

Treesearch

Samuel L. Zelinka; Keith J. Bourne; John C. Hermanson; Samuel V. Glass; Adriana Costa; Alex C. Wiedenhoeft

2015-01-01

The elastic properties of pit membranes are reported to have important implications in understanding air-seeding phenomena in gymnosperms, and pit aspiration plays a large role in wood technological applications such as wood drying and preservative treatment. Here we present force–displacement measurements for pit membranes of circular bordered pits, collected on a...

Manipulation of nanoscale V-pits to optimize internal quantum efficiency of InGaN multiple quantum wells

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

Chang, Chiao-Yun; Li, Heng; Shih, Yang-Ta

2015-03-02

We systematically investigated the influence of nanoscale V-pits on the internal quantum efficiency (IQE) of InGaN multiple quantum wells (MQWs) by adjusting the underlying superlattices (SLS). The analysis indicated that high barrier energy of sidewall MQWs on V-pits and long diffusion distance between the threading dislocation (TD) center and V-pit boundary were crucial to effectively passivate the non-radiative centers of TDs. For a larger V-pit, the thicker sidewall MQW on V-pit would decrease the barrier energy. On the contrary, a shorter distance between the TD center and V-pit boundary would be observed in a smaller V-pit, which could increase themore » carrier capturing capability of TDs. An optimized V-pit size of approximately 200–250 nm in our experiment could be concluded for MQWs with 15 pairs SLS, which exhibited an IQE value of 70%.« less

Techniques To Enhance Instructors' Teaching Effectiveness with Chemistry Students Who Are Blind or Visually Impaired

NASA Astrophysics Data System (ADS)

Supalo, Cary

2005-10-01

This paper describes techniques developed as solutions to problems encountered while teaching blind or visually impaired students in chemistry courses at high school and postsecondary levels. Establishing and maintaining a sound student instructor relationship is critical to the success and implementation of a plan of action for blind or visually impaired students enrolled in chemistry courses.

Survey of application of radiation to preparative chemistry

NASA Technical Reports Server (NTRS)

Philipp, W. H.

1973-01-01

The use of radiation for preparative chemistry in liquid solutions is investigated. General principles are presented and preparations involving reduction, oxidation, polymerization, and decomposition are given. The use of various solvents, water, other inorganic liquids and organic liquids for this purpose is discussed. Finally, a commentary is made on some specific applications where radiation chemistry as a preparative technique may be useful.

Introduction to Computational Chemistry: Teaching Hu¨ckel Molecular Orbital Theory Using an Excel Workbook for Matrix Diagonalization

ERIC Educational Resources Information Center

Litofsky, Joshua; Viswanathan, Rama

2015-01-01

Matrix diagonalization, the key technique at the heart of modern computational chemistry for the numerical solution of the Schrödinger equation, can be easily introduced in the physical chemistry curriculum in a pedagogical context using simple Hückel molecular orbital theory for p bonding in molecules. We present details and results of…

Independent Learning Project for Advanced Chemistry (ILPAC). Teachers' and Technicians' Notes for First Year Units.

ERIC Educational Resources Information Center

Inner London Education Authority (England).

The Independent Learning Project for Advanced Chemistry (ILPAC) has produced units of study for students in A-level chemistry. Students completing ILPAC units assume a greater responsibility for their own learning and can work, to some extent, at their own pace. By providing guidance, and detailed solutions to exercises in the units, supported by…

Distribution, formation mechanisms, and significance of lunar pits

NASA Astrophysics Data System (ADS)

Wagner, Robert V.; Robinson, Mark S.

2014-07-01

Lunar Reconnaissance Orbiter Camera images reveal the presence of steep-walled pits in mare basalt (n = 8), impact melt deposits (n = 221), and highland terrain (n = 2). Pits represent evidence of subsurface voids of unknown extents. By analogy with terrestrial counterparts, the voids associated with mare pits may extend for hundreds of meters to kilometers in length, thereby providing extensive potential habitats and access to subsurface geology. Because of their small sizes relative to the local equilibrium crater diameters, the mare pits are likely to be post-flow features rather than volcanic skylights. The impact melt pits are indirect evidence both of extensive subsurface movement of impact melt and of exploitable sublunarean voids. Due to the small sizes of pits (mare, highland, and impact melt) and the absolute ages of their host materials, it is likely that most pits formed as secondary features.

Pit Latrine Fecal Sludge Resistance Using a Dynamic Cone Penetrometer in Low Income Areas in Mzuzu City, Malawi

PubMed Central

Chirwa, Charles F. C.; Hall, Ralph P.; Krometis, Leigh-Anne H.; Vance, Eric A.; Edwards, Adam; Guan, Ting; Holm, Rochelle H.

2017-01-01

Pit latrines can provide improved household sanitation, but without effective and inexpensive emptying options, they are often abandoned once full and may pose a public health threat. Emptying techniques can be difficult, as the sludge contents of each pit latrine are different. The design of effective emptying techniques (e.g., pumps) is limited by a lack of data characterizing typical in situ latrine sludge resistance. This investigation aimed to better understand the community education and technical engineering needs necessary to improve pit latrine management. In low income areas within Mzuzu city, Malawi, 300 pit latrines from three distinct areas were assessed using a dynamic cone penetrometer to quantify fecal sludge strength, and household members were surveyed to determine their knowledge of desludging procedures and practices likely to impact fecal sludge characteristics. The results demonstrate that there is a significant difference in sludge strength between lined and unlined pits within a defined area, though sludge hardened with depth, regardless of the pit type or region. There was only limited association between cone penetration depth and household survey data. To promote the adoption of pit emptying, it is recommended that households be provided with information that supports pit emptying, such as latrine construction designs, local pit emptying options, and cost. This study indicates that the use of a penetrometer test in the field prior to pit latrine emptying may facilitate the selection of appropriate pit emptying technology. PMID:28165378

Computational chemistry

NASA Technical Reports Server (NTRS)

Arnold, J. O.

1987-01-01

With the advent of supercomputers, modern computational chemistry algorithms and codes, a powerful tool was created to help fill NASA's continuing need for information on the properties of matter in hostile or unusual environments. Computational resources provided under the National Aerodynamics Simulator (NAS) program were a cornerstone for recent advancements in this field. Properties of gases, materials, and their interactions can be determined from solutions of the governing equations. In the case of gases, for example, radiative transition probabilites per particle, bond-dissociation energies, and rates of simple chemical reactions can be determined computationally as reliably as from experiment. The data are proving to be quite valuable in providing inputs to real-gas flow simulation codes used to compute aerothermodynamic loads on NASA's aeroassist orbital transfer vehicles and a host of problems related to the National Aerospace Plane Program. Although more approximate, similar solutions can be obtained for ensembles of atoms simulating small particles of materials with and without the presence of gases. Computational chemistry has application in studying catalysis, properties of polymers, all of interest to various NASA missions, including those previously mentioned. In addition to discussing these applications of computational chemistry within NASA, the governing equations and the need for supercomputers for their solution is outlined.

Tank Riser Pit Decontamination System (Pit Viper) Return on Investment and Break-Even Analysis

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

Young, Joan K.; Weimar, Mark R.; Balducci, Patrick J.

2003-06-30

This study assessed the cost benefit of Pit Viper deployment for 80 tank farm pits between October 1, 2003 and September 30, 2012 under the technical baseline for applicable double-shell tank (DST) and single-shell tank (SST) projects. After this assessment had been completed, the U.S. Department of Energy (DOE) Richland Operations Office (RL) and Office of River Protection (ORP) published the Hanford Performance Management Plan (August 2003), which accelerated the schedule for SST retrieval. Then, DOE/CH2M HILL contract modification M064 (October 2002) and The Integrated Mission Acceleration Plan (March 2003) further accelerated SST retrieval and closure schedules. Twenty-six to 40more » tanks must be retrieved by 2006. Thus the schedule for SST pit entries is accelerated and the number of SST pit entries is increased. This study estimates the return on investment (ROI) and the number of pits where Pit Viper deployment would break even or save money over current manual practices. The results of the analysis indicate a positive return on the federal investment for deployment of the Pit Viper provided it is used on a sufficient number of pits.« less

Printability and inspectability of programmed pit defects on teh masks in EUV lithography

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

Kang, I.-Y.; Seo, H.-S.; Ahn, B.-S.

2010-03-12

Printability and inspectability of phase defects in ELlVL mask originated from substrate pit were investigated. For this purpose, PDMs with programmed pits on substrate were fabricated using different ML sources from several suppliers. Simulations with 32-nm HP L/S show that substrate pits with below {approx}20 nm in depth would not be printed on the wafer if they could be smoothed by ML process down to {approx}1 nm in depth on ML surface. Through the investigation of inspectability for programmed pits, minimum pit sizes detected by KLA6xx, AIT, and M7360 depend on ML smoothing performance. Furthermore, printability results for pit defectsmore » also correlate with smoothed pit sizes. AIT results for pattemed mask with 32-nm HP L/S represents that minimum printable size of pits could be {approx}28.3 nm of SEVD. In addition, printability of pits became more printable as defocus moves to (-) directions. Consequently, printability of phase defects strongly depends on their locations with respect to those of absorber patterns. This indicates that defect compensation by pattern shift could be a key technique to realize zero printable phase defects in EUVL masks.« less

An Autoregulatory Pathway Establishes the Definitive Chromatin Conformation at the Pit-1 Locus

PubMed Central

Cooke, Nancy E.; Liebhaber, Stephen A.

2015-01-01

The transcription factor Pit-1 (POU1-F1) plays a dominant role in cell lineage expansion and differentiation in the anterior pituitary. Prior studies of the mouse Pit-1 (mPit-1) gene revealed that this master regulatory locus is activated at embryonic day 13.5 (E13.5) by an early enhancer (EE), whereas its subsequent expression throughout adult life is maintained by a more distal definitive enhancer (DE). Here, we demonstrate that the sequential actions of these two enhancers are linked to corresponding shifts in their proximities to the Pit-1 promoter. We further demonstrate that the looping of the definitive enhancer to the mPit-1 promoter is critically dependent on a self-sustaining autoregulatory mechanism mediated by the Pit-1 protein. These Pit-1-dependent actions are accompanied by localized recruitment of CBP and enrichment for H3K27 acetylation within the Pit-1 locus. These data support a model in which the sequential actions of two developmentally activated enhancers are linked to a corresponding shift in higher-order chromatin structures. This shift establishes an autoregulatory circuit that maintains durable expression of Pit-1 throughout adult life. PMID:25691665

Giant weathering pits in the Entrada Sandstone, southeastern Utah: Preliminary findings

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

Netoff, D.I.; Shroba, R.R.

Giant weathering pits formed in outcrops of the lower Entrada Sandstone slickrock of Jurassic age are present in two areas in the Glen Canyon region of arid southeastern Utah. The pits are far larger than any previously described in the geologic literature. The pits near Cookie Jar Butte are commonly cylindrical, typically have low width-to-depth ratios (1.5--3.6), and have a depth of closure of as much as 18 m. There are no obvious lithologic or structural controls that determine their shape or location. Many of the pits at Rock Creek Bay are elongate; several of them have long axes inmore » excess of 53 m, and the longest one is 74 m. Many of the pit walls are breached at the top, and the depth of closure is generally less than 6 m. The shapes of these pits are influenced by point orientation and pit coalescence. Thin-section analyses of near-surface sandstone cores taken near Cookie Jar Butte from pit walls, floors, and rims reveal no significant diagenetic alteration of the fine-grained to very fine frained quartzose sandstone (quartz arenite). Quartz grains appear fresh, and feldspar grains are only slightly weathered. The cement between the grains is mostly CaCO[sub 3]. In several of the pits in both areas sandy sediment veneers the bedrock floor. This sediment is similar in character to the adjacent sandstone and is probably locally derived. Possible origins of the giant pits include various physical, chemical, and biological weathering processes that initiate pit development, followed by excavation by plunge-pool action, wind deflation, dissolution, and piping. Preliminary field and laboratory data do not clearly identify and single process of group of processes that account for pit development.« less

Hydrated Cations in the General Chemistry Course.

ERIC Educational Resources Information Center

Kauffman, George B.; Baxter, John F., Jr.

1981-01-01

Presents selected information regarding the descriptive chemistry of the common metal ions and their compounds, including the concepts of process of solution, polar molecules, ionic size and charge, complex ions, coordination number, and the Bronsted-Lowry acid-base theory. (CS)

Is Playing in the Pit Really the Pits?: Pain, Strength, Music Performance Anxiety, and Workplace Satisfaction in Professional Musicians in Stage, Pit, and Combined Stage/Pit Orchestras.

PubMed

Kenny, Dianna T; Driscoll, Tim; Ackermann, Bronwen J

2016-03-01

Typically, Australian orchestral musicians perform on stage, in an orchestra pit, or in a combination of both workplaces. This study explored a range of physical and mental health indicators in musicians who played in these different orchestra types to ascertain whether orchestra environment was a risk factor affecting musician wellbeing. Participants comprised 380 full-time orchestral musicians from the eight major state orchestras in Australia comprised of two dedicated pit orchestras, three stage-only symphonic orchestras, and three mixed stage/pit orchestras. Participants completed a physical assessment and a range of self-report measures assessing performance-related musculoskeletal disorders (PRMD), physical characteristics including strength and perceived exertion, and psychological health, including music performance anxiety (MPA), workplace satisfaction, and bullying. Physical characteristics and performance-related musculoskeletal profiles were similar for most factors on the detailed survey completed by orchestra members. The exceptions were that pit musicians demonstrated greater shoulder and elbow strength, while mixed-workload orchestra musicians had greater flexibility Significantly more exertion was reported by pit musicians when rehearsing and performing. Stage/pit musicians reported less physical exertion when performing in the pit compared with performing on stage. Severity of MPA was significantly greater in pit musicians than mixed orchestra musicians. Pit musicians also reported more frequent bullying and lower job satisfaction compared with stage musicians. There were few differences in the objective physical measures between musicians in the different orchestra types. However, pit musicians appear more psychologically vulnerable and less satisfied with their work than musicians from the other two orchestra types. The physical and psychological characteristics of musicians who perform in different orchestra types have not been adequately theorized or studied. We offer some preliminary thoughts that may account for the observed differences.

Mitis group streptococci express variable pilus islet 2 pili.

PubMed

Zähner, Dorothea; Gandhi, Ashish R; Yi, Hong; Stephens, David S

2011-01-01

Streptococcus oralis, Streptococcus mitis, and Streptococcus sanguinis are members of the Mitis group of streptococci and agents of oral biofilm, dental plaque and infective endocarditis, disease processes that involve bacteria-bacteria and bacteria-host interactions. Their close relative, the human pathogen S. pneumoniae uses pilus-islet 2 (PI-2)-encoded pili to facilitate adhesion to eukaryotic cells. PI-2 pilus-encoding genetic islets were identified in S. oralis, S. mitis, and S. sanguinis, but were absent from other isolates of these species. The PI-2 islets resembled the genetic organization of the PI-2 islet of S. pneumoniae, but differed in the genes encoding the structural pilus proteins PitA and PitB. Two and three variants of pitA (a pseudogene in S. pneumoniae) and pitB, respectively, were identified that showed ≈20% difference in nucleotide as well as corresponding protein sequence. Species-independent combinations of pitA and pitB variants indicated prior intra- and interspecies horizontal gene transfer events. Polyclonal antisera developed against PitA and PitB of S. oralis type strain ATCC35037 revealed that PI-2 pili in oral streptococci were composed of PitA and PitB. Electronmicrographs showed pilus structures radiating >700 nm from the bacterial surface in the wild type strain, but not in an isogenic PI-2 deletion mutant. Anti-PitB-antiserum only reacted with pili containing the same PitB variant, whereas anti-PitA antiserum was cross-reactive with the other PitA variant. Electronic multilocus sequence analysis revealed that all PI-2-encoding oral streptococci were closely-related and cluster with non-PI-2-encoding S. oralis strains. This is the first identification of PI-2 pili in Mitis group oral streptococci. The findings provide a striking example of intra- and interspecies horizontal gene transfer. The PI-2 pilus diversity provides a possible key to link strain-specific bacterial interactions and/or tissue tropisms with pathogenic traits in the Mitis group streptococci.

Development of an aversive Pavlovian-to-instrumental transfer task in rat

PubMed Central

Campese, Vincent; McCue, Margaret; Lázaro-Muñoz, Gabriel; LeDoux, Joseph E.; Cain, Christopher K.

2013-01-01

Pavlovian-to-instrumental transfer (PIT) is an effect whereby a classically conditioned stimulus (CS) enhances ongoing instrumental responding. PIT has been extensively studied with appetitive conditioning but barely at all with aversive conditioning. Although it's been argued that conditioned suppression is a form of aversive PIT, this effect is fundamentally different from appetitive PIT because the CS suppresses, instead of facilitates, responding. Five experiments investigated the importance of a variety of factors on aversive PIT in a rodent Sidman avoidance paradigm in which ongoing shuttling behavior (unsignaled active avoidance or USAA) was facilitated by an aversive CS. Experiment 1 demonstrated a basic PIT effect. Experiment 2 found that a moderate amount of USAA extinction produces the strongest PIT with shuttling rates best at around 2 responses per minute prior to the CS. Experiment 3 tested a protocol in which the USAA behavior was required to reach the 2-response per minute mark in order to trigger the CS presentation and found that this produced robust and reliable PIT. Experiment 4 found that the Pavlovian conditioning US intensity was not a major determinant of PIT strength. Experiment 5 demonstrated that if the CS and US were not explicitly paired during Pavlovian conditioning, PIT did not occur, showing that CS-US learning is required. Together, these studies demonstrate a robust, reliable and stable aversive PIT effect that is amenable to analysis of neural circuitry. PMID:24324417

Observation of Eye Pattern on Super-Resolution Near-Field Structure Disk with Write-Strategy Technique

NASA Astrophysics Data System (ADS)

Fuji, Hiroshi; Kikukawa, Takashi; Tominaga, Junji

2004-07-01

Pit-edge recording at a density of 150 nm pits and spaces is carried out on a super-resolution near-field structure (super-RENS) disk with a platinum oxide layer. Pits are recorded and read using a 635-nm-wavelength laser and an objective lens with a 0.6 numerical aperture. We arrange laser pulses to correctly record the pits on the disk by a write-strategy technique. The laser-pulse figure includes a unit time of 0.25 T and intensities of Pw1, Pw2 and Pw3. After recording pits of various lengths, the observation of an eye pattern is achieved despite a pit smaller than the resolution limit. Furthermore, the eye pattern maintains its shape even though other pits fill the adjacent tracks at a track density of 600 nm. The disk can be used as a pit-edge recording system through a write-strategy technique.

Analysis on the stress corrosion crack inception based on pit shape and size of the FV520B tensile specimen

NASA Astrophysics Data System (ADS)

Xiang, Longhao; Pan, Juyi; Chen, Songying

2018-06-01

The influence of pit shape and size on local stress concentration in the tensile specimen and the stress corrosion cracks inception was studied by employing the element remove technique. The maximum stress located in the bottom of pit on FV520B tensile specimen. The location of maximum strain was near the mouth of the pit or the shoulder and plastic strain existed in this region. Stress concentration factor and plastic deformation on four different geometrical shape pits of hemisphere, semi-ellipsoid, bullet and butterfly were numerically investigated, respectively. The simulation results showed that butterfly pit got the biggest stress concentration factor. The plastic strain rate during pit growth was in the sensitivity range of stress corrosion cracks inception, indicating that stress corrosion cracks were more likely to nucleate near the pit tip or the shoulder.

Hot corrosion of ceramic engine materials

NASA Technical Reports Server (NTRS)

Fox, Dennis S.; Jacobson, Nathan S.; Smialek, James L.

1988-01-01

A number of commercially available SiC and Si3N4 materials were exposed to 1000 C in a high velocity, pressurized burner rig as a simulation of a turbine engine environment. Sodium impurities added to the burner flame resulted in molten Na2SO4 deposition, attack of the SiC and Si4N4 and formation of substantial Na2O-x(SiO2) corrosion product. Room temperature strength of the materials decreased. This was a result of the formation of corrosion pits in SiC, and grain boundary dissolution and pitting in Si3N4. Corrosion regimes for such Si-based ceramics have been predicted using thermodynamics and verified in rig tests of SiO2 coupons. Protective mullite coatings are being investigated as a solution to the corrosion problem for SiC and Si3N4. Limited corrosion occurred to cordierite (Mg2Al4Si5O18) but some cracking of the substrate occurred.

Evaluation of candidate alloys for the construction of metal flex hoses in the STS launch environment

NASA Technical Reports Server (NTRS)

Ontiveros, Cordelia

1988-01-01

Various vacuum jacketed cryogenic supply lines at the Shuttle launch site use convoluted flexible expansion joints. The atmosphere at the launch site has a very high salt content, and during a launch, fuel combustion products include hydrochloric acid. This extremely corrosive environment has caused pitting corrosion failure in the flex hoses, which were made of 304L stainless steel. A search was done to find a more corrosion resistant replacement material. This study focused on 19 metal alloys. Tests which were performed include electrochemical corrosion testing, accelerated corrosion testing in a salt fog chamber, long term exposure at the beach corrosion testing site, and pitting corrosion tests in ferric chloride solution. Based on the results of these tests, the most corrosion resistant alloys were found to be (in order) Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, and Inco Alloy G-3. Of these top five alloys, the Hastelloy C-22 stands out as being the best of those tested for this application.

Evaluation of candidate alloys for the construction of metal flex hoses in the STS launch environment

NASA Technical Reports Server (NTRS)

Macdowell, Louis G., III; Ontiveros, Cordelia

1988-01-01

Various vacuum jacketed cryogenic supply lines at the Shuttle launch site use convoluted flexible expansion joints. The atmosphere at the launch site has a very high salt content, and during a launch fuel combustion products include hydrochloric acid. This extremely corrosive environment has caused pitting corrosion failure in the flex hoses, which were made out of 304L stainless steel. A search was done to find a more corrosion resistant replacement material. Nineteen metal alloys were tested. Tests which were performed include electrochemical corrosion testing, accelerated corrosion testing in a salt fog chamber, long term exposure at the beach corrosion testing site, and pitting corrosion tests in ferric chloride solution. Based on the results, the most corrosion resistant alloys were found to be, in order, Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, and Inco Alloy G-3. Of these top five alloys, the Hastelloy C-22 stands out as being the best of the alloys tested.

Effects of impurities on the biodegradation behavior of pure magnesium

NASA Astrophysics Data System (ADS)

Lee, Ji-Young; Han, Gilsoo; Kim, Yu-Chan; Byun, Ji-Young; Jang, Jae-il; Seok, Hyun-Kwang; Yang, Seok-Jo

2009-12-01

The corrosion behavior of pure magnesium that has different content ratio of impurities (such as Fe/Mn ratio) in Hanks' solution was investigated in order to tailor the lifetime of biodegradable implant made of pure magnesium. Two distinct stages of corrosion were observed: a slow corrosion rate stage and a subsequent fast corrosion rate stage. The first stage was characterized by uniform corrosion that produced magnesium hydroxide and calcium phosphate film on a magnesium surface, resulting in a slow corrosion rate. The second stage with an abrupt increase in the corrosion rate was induced by Fe precipitates and was stimulated by an increase in the Fe/Mn ratio. This corrosion was developed to a preferred crystallographic pitting corrosion where the pits propagated along the preferred crystallographic plane and several layers of Mg planes with narrow interplanar space remained uncorroded. From this study, it is expected that the lifetime of the biodegradable implant made of pure Mg can be tailored by controlling the amount and ratio of the impurities.

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

Lawrence, G.B.; Fernandez, I.J.; Goltz, S.M.

To provide information needed to assess the current and future status of spruce-fir forests in Maine, the Howland Integrated Forest Study (HIFS) was initiated in 1987 as part of the USDA Forest Service Forest Response Program, in conjunction with the establishment of a Mountain Cloud Chemistry Program (MCCP) monitoring site. Through this project, bulk and wet-only precipitation, dry deposition, throughfall and soil solution chemistry has been determined. This paper will focus on soil solution collected between May, 1988 and bulk precipitation collected from June through November, 1988.

Using Games To Teach Chemistry: An Annotated Bibliography

NASA Astrophysics Data System (ADS)

Russell, Jeanne V.

1999-04-01

A list of published or marketed games based on a chemistry motif is presented. Each game is listed according to its level, subject matter, and title. A bibliographic notation and a short description are given for each game. For Introductory/High School/General Chemistry, 45 games are listed under the subjects General Knowledge; Elements & Atomic Structure (not Symbols); Nomenclature, Formulas, & Equation Writing; Chemical Reactions: Solutions & Solubilities; and Other Subjects. Seventeen games are listed under Organic Chemistry and 4 games under Other Chemistry Games. Computer games designed for outdated computers (PDP-11, TRS-80, and Apple II) are not included.

Loss of PiT-1 Results in Abnormal Endocytosis in the Yolk Sac Visceral Endoderm

PubMed Central

Wallingford, Mary C.; Giachelli, Cecilia M.

2014-01-01

PiT-1 protein is a transmembrane sodium-dependent phosphate (Pi) transporter. PiT-1 knock out (KO) embryos die from largely unknown causes by embryonic day (E) 12.5. We tested the hypothesis that PiT-1 is required for endocytosis in the embryonic yolk sac (YS) visceral endoderm (VE). Here we present data supporting that PiT-1 KO results in a YS remodeling defect and decreased endocytosis in the YS VE. The remodeling defect is not due to an upstream cardiomyocyte requirement for PiT-1, as SM22αCre-specific KO of PiT-1 in the developing heart and the YS mesodermal layer (ME) does not recapitulate the PiT-1 global KO phenotype. Furthermore, we find that high levels of PiT-1 protein localize to the YS VE apical membrane. Together these data support that PiT-1 is likely required in YS VE. During normal development maternal immunoglobulin (IgG) is endocytosed into YS VE and accumulates in the apical side of the VE in a specialized lysosome termed the apical vacuole (AV). We have identified a reduction in PiT-1 KO VE cell height and a striking loss of IgG accumulation in the PiT-1 KO VE. The endocytosis genes Tfeb, Lamtor2 and Snx2 are increased at the RNA level. Lysotracker Red staining reveals a loss of distinct AVs, and yolk sacs incubated ex vivo with phRODO Green Dextran for Endocytosis demonstrate a functional loss of endocytosis. As yolk sac endocytosis is controlled in part by microautophagy, but expression of LC3 had not been examined, we investigated LC3 expression during yolk sac development and found stage-specific LC3 RNA expression that is predominantly from the YS VE layer at E9.5. Normalized LC3-II protein levels are decreased in the PiT-1 KO YS, supporting a requirement for PiT-1 in autophagy in the YS. Therefore, we propose the novel idea that PiT-1 is central to the regulation of endocytosis and autophagy in the YS VE. PMID:25138534

Retention and transport of nutrients in a third-order stream in northwestern California; hyporheic processes

USGS Publications Warehouse

Triska, F.J.; Kennedy, V.C.; Avanzino, R.J.; Zellweger, G.W.; Bencala, K.E.

1989-01-01

Chloride and nitrate were coinjected into the surface waters of a third-order stream for 20 d to exmaine solute retention, and the fate of nitrate during subsurface transport. A series of wells (shallow pits) 0.5-10 m from the adjacent channel were sampled to estimate the lateral interflow of water. Two subsurface return flows beneath the wetted channel were also examined. Results indicated that the capacity of the hyporheic zone for transient solute storage and as potential biological habitat varies with channel morphology, bed roughness, and permeability. A conceptual model that considers the groundwater-stream water interface as the fluvial boundary is proposed. -from Authors

Effect of Phosphate-Buffered Solution Corrosion on the Ratcheting Fatigue Behavior of a Duplex Mg-Li-Al Alloy

NASA Astrophysics Data System (ADS)

Yuan, Xin; Yu, Dunji; Gao, Li-Lan; Gao, Hong

2016-05-01

This work reports the uniaxial ratcheting and fatigue behavior of a duplex Mg-Li-Al alloy under the influence of phosphate-buffered solution corrosion. Microstructural observations reveal pitting and filament corrosion defects, which impair the load-bearing capacity of the alloy and cause stress concentration, thus leading to an accelerated accumulation of ratcheting strain and shortened fatigue life under the same nominal loading conditions. Comparing Smith model, Smith-Watson-Topper model, and Paul-Sivaprasad-Dhar model, a ratcheting fatigue life prediction model based on the Broberg damage rule and the Paul-Sivaprasad-Dhar model was proposed, and the model yielded a superior prediction for the studied magnesium alloy.

Microfluidics for High School Chemistry Students.

PubMed

Hemling, Melissa; Crooks, John A; Oliver, Piercen M; Brenner, Katie; Gilbertson, Jennifer; Lisensky, George C; Weibel, Douglas B

2014-01-14

We present a laboratory experiment that introduces high school chemistry students to microfluidics while teaching fundamental properties of acid-base chemistry. The procedure enables students to create microfluidic systems using nonspecialized equipment that is available in high school classrooms and reagents that are safe, inexpensive, and commercially available. The experiment is designed to ignite creativity and confidence about experimental design in a high school chemistry class. This experiment requires a computer program (e.g., PowerPoint), Shrinky Dink film, a readily available silicone polymer, weak acids, bases, and a colorimetric pH indicator. Over the span of five 45-min class periods, teams of students design and prepare devices in which two different pH solutions mix in a predictable way to create five different pH solutions. Initial device designs are instructive but rarely optimal. During two additional half-class periods, students have the opportunity to use their initial observations to redesign their microfluidic systems to optimize the outcome. The experiment exposes students to cutting-edge science and the design process, and solidifies introductory chemistry concepts including laminar flow, neutralization of weak acids-bases, and polymers.

Microfluidics for High School Chemistry Students

PubMed Central

Hemling, Melissa; Crooks, John A.; Oliver, Piercen M.; Brenner, Katie; Gilbertson, Jennifer; Lisensky, George C.; Weibel, Douglas B.

2014-01-01

We present a laboratory experiment that introduces high school chemistry students to microfluidics while teaching fundamental properties of acid–base chemistry. The procedure enables students to create microfluidic systems using nonspecialized equipment that is available in high school classrooms and reagents that are safe, inexpensive, and commercially available. The experiment is designed to ignite creativity and confidence about experimental design in a high school chemistry class. This experiment requires a computer program (e.g., PowerPoint), Shrinky Dink film, a readily available silicone polymer, weak acids, bases, and a colorimetric pH indicator. Over the span of five 45-min class periods, teams of students design and prepare devices in which two different pH solutions mix in a predictable way to create five different pH solutions. Initial device designs are instructive but rarely optimal. During two additional half-class periods, students have the opportunity to use their initial observations to redesign their microfluidic systems to optimize the outcome. The experiment exposes students to cutting-edge science and the design process, and solidifies introductory chemistry concepts including laminar flow, neutralization of weak acids–bases, and polymers. PMID:25584013

Illuminating Anaerobic Microbial Community and Cooccurrence Patterns across a Quality Gradient in Chinese Liquor Fermentation Pit Muds

PubMed Central

Hu, Xiaolong; Du, Hai; Ren, Cong

2016-01-01

Fermentation pit mud, an important reservoir of diverse anaerobic microorganisms, is essential for Chinese strong-aroma liquor production. Pit mud quality, according to its sensory characteristics, can be divided into three grades: degraded, normal, and high quality. However, the relationship between pit mud microbial community and pit mud quality is poorly understood, as are microbial associations within the pit mud ecosystem. Here, microbial communities at these grades were compared using Illumina MiSeq sequencing of the variable region V4 of the 16S rRNA gene. Our results revealed that the pit mud microbial community was correlated with its quality and environmental factors. Species richness, biodiversity, and relative and/or absolute abundances of Clostridia, Clostridium kluyveri, Bacteroidia, and Methanobacteria significantly increased, with corresponding increases in levels of pH, NH4+, and available phosphorus, from degraded to high-quality pit muds, while levels of Lactobacillus, dissolved organic carbon, and lactate significantly decreased, with normal samples in between. Furthermore, 271 pairs of significant and robust correlations (cooccurrence and negative) were identified from 76 genera using network analysis. Thirteen hubs of cooccurrence patterns, mainly under the Clostridia, Bacteroidia, Methanobacteria, and Methanomicrobia, may play important roles in pit mud ecosystem stability, which may be destroyed with rapidly increased levels of lactic acid bacteria (Lactobacillus, Pediococcus, and Streptococcus). This study may help clarify the relationships among microbial community, environmental conditions, and pit mud quality, allow the improvement of pit mud quality by using bioaugmentation and controlling environmental factors, and shed more light on the ecological rules guiding community assembly in pit mud. PMID:26896127

What We Have Learned From Our Inspections of Incinerators and Use of Burn Pits in Afghanistan: Final Assessment

DTIC Science & Technology

2015-02-01

In 2004, the Department of Defense (DOD) began introducing new solid waste disposal methods in Afghanistan, including landfills and incineration...base landfills and incinera- tion. Nonetheless, the overall approach to its solid waste disposal in Afghanistan was hap- hazard and reactive. DOD was...contract to have solid waste hauled to a local landfill —a solution that could have eliminat- SIGAR 15-33-AL: Final assessment: incinerators and Burn

Effects of laser remelting on microstructures and immersion corrosion performance of arc sprayed Al coating in 3.5% NaCl solution

NASA Astrophysics Data System (ADS)

Sun, Ze; Zhang, Donghui; Yan, Baoxu; Kong, Dejun

2018-02-01

An arc sprayed aluminum (Al) coating on S355 steel was processed using a laser remelting (LR). The microstructures, chemical element composition, and phases of the obtained Al coating were analyzed using a field mission scanning electronic microscope (FESEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively, and the residual stresses were measured using an X-ray diffraction stress tester. The immersion corrosion tests and potentiodynamic polarization of Al coating in 3.5% NaCl solution were performed to investigate the effects of LR on its immersion corrosion behaviors, and the corrosion mechanism of Al coating was also discussed. The results show that the arc sprayed Al coating is composed of Al phase, while that by LR is composed of Al-Fe and AlO4FeO6 phases, and the porosities and cracks in the arc sprayed Al coating are eliminated by LR, The residual stress of arc sprayed Al coating is -5.6 ± 18 MPa, while that after LR is 137.9 ± 12 MPa, which deduces the immersion corrosion resistance of Al coating. The corrosion mechanism of arc sprayed Al coating is pitting corrosion and crevice corrosion, while that by LR is uniform corrosion and pitting corrosion. The corrosion potential of arc sprayed Al coating by LR shifts positively, which improves its immersion corrosion resistance.

Microscopic effects of predator digestion on the surfaces of bones and teeth.

PubMed

Rensberger, J M; Krentz, H B

1988-09-01

Concentrations of small fossil mammals are frequently encountered in Cenozoic deposits, but the causes for such accumulations have seldom been determined. In many cases the tooth, jaw, and limb fragments appear to be well-preserved under light microscopy, and it is difficult to differentiate damage due to predator digestion from breakage and abrasion due to physical agents. In order to find more specific evidence of predator digestion, we used a scanning electron microscope (SEM) to examine the surface microstructure of bones and teeth consumed by Bubo virginianus (great horned owl) and Canis latrans (coyote), which prey upon similar species. Effects of digestion were found on all the digested bones and teeth examined. The effects on bone include distinctive sets of pits and fissures, dissolution, and physical polishing. The pits and fissures are apparently caused by solution that commences in canals beneath the surface of the bone. The most conspicuous effects on teeth are island-like pillars of dentin surrounded by deep solution fissures. The effects of digestion by coyote and owl are fundamentally the same but differ in degree of development. Bone digested by the owl shows a greater degree of polishing and rounding of edges but has less extensive fissuring. Wide variation in the degree of surface damage occurs in bones digested by the coyote, even within a single fecal pellet.

Refunctionalization of the ancient rice blast disease resistance gene Pit by the recruitment of a retrotransposon as a promoter.

PubMed

Hayashi, Keiko; Yoshida, Hitoshi

2009-02-01

The plant genome contains a large number of disease resistance (R) genes that have evolved through diverse mechanisms. Here, we report that a long terminal repeat (LTR) retrotransposon contributed to the evolution of the rice blast resistance gene Pit. Pit confers race-specific resistance against the fungal pathogen Magnaporthe grisea, and is a member of the nucleotide-binding site leucine-rich repeat (NBS-LRR) family of R genes. Compared with the non-functional allele Pit(Npb), the functional allele Pit(K59) contains four amino acid substitutions, and has the LTR retrotransposon Renovator inserted upstream. Pathogenesis assays using chimeric constructs carrying the various regions of Pit(K59) and Pit(Npb) suggest that amino acid substitutions might have a potential effect in Pit resistance; more importantly, the upregulated promoter activity conferred by the Renovator sequence is essential for Pit function. Our data suggest that transposon-mediated transcriptional activation may play an important role in the refunctionalization of additional 'sleeping' R genes in the plant genome.

Associations of polymorphisms in the Pit-1 gene with growth and carcass traits in Angus beef cattle.

PubMed

Zhao, Q; Davis, M E; Hines, H C

2004-08-01

The Pit-1 gene was studied as a candidate for genetic markers of growth and carcass traits. Angus beef cattle that were divergently selected for high- or low-blood serum IGF-I concentration were used in this study. The single-strand conformation polymorphism method was used to identify polymorphism in the Pit-1 gene including regions from intron 2 to exon 6. Two polymorphisms, Pit1I3H (HinfI) and Pit1I3NL (NlaIII), were detected in intron 3 of the Pit-1 gene. One polymorphism, Pit1I4N (BstNI), was found in intron 4, and a single nucleotide polymorphism, Pit1I5, was found in intron 5. The previously reported polymorphism in exon 6, Pit1E6H (HinfI), was also studied in 416 Angus beef cattle. Associations of the polymorphisms with growth traits, carcass traits, and IGF-I concentration were analyzed using a general linear model procedure. No significant associations were observed between these polymorphisms and growth and carcass traits.

JPRS Report, Science & Technology, USSR: Chemistry.

DTIC Science & Technology

1987-08-18

ZHURNAL PRIKLADNOY KHIMII, No 11, Nov 86). 64 Hydrothermal Chemistry of Gallium Alpha-orthophosphate in Orthophosphoric Acid (A. A, Adkhamov, B. S...precipitation from nitrate solutions with ammonium oxalate , heating to 400 deg and calcining at 800, 950 and 1100 deg for 4 hours. A high catalytic...12765/9835 CSO: 1841/215 UDC 548.54 HYDROTHERMAL CHEMISTRY OF GALLIUM ALPHA-ORTHOPHOSPHATE IN ORTHOPHOSPHORIC ACID Moscow DOKLADY AKADEMII NAUK

Understanding `green chemistry' and `sustainability': an example of problem-based learning (PBL)

NASA Astrophysics Data System (ADS)

Günter, Tuğçe; Akkuzu, Nalan; Alpat, Şenol

2017-10-01

Background: This study uses problem-based learning (PBL) to ensure that students comprehend the significance of green chemistry better by experiencing the stages of identifying the problem, developing hypotheses, and providing solutions within the problem-solving process.

Education in Environmental Chemistry: Setting the Agenda and Recommending Action

ERIC Educational Resources Information Center

Zoller, Uri

2005-01-01

The effective utilization of Education in Environmental Chemistry (EEC) in addressing global and societal environmental problems requires integration between educational, technical, financial, ethical and societal considerations. An interdisciplinary approach is fundamental to efforts to achieve long-term solutions.

Method for providing uranium articles with a corrosion resistant anodized coating

DOEpatents

Waldrop, Forrest B.; Washington, Charles A.

1982-01-01

Uranium articles are provided with anodized oxide coatings in an aqueous solution of an electrolyte selected from the group consisting of potassium phosphate, potassium hydroxide, ammonium hydroxide, and a mixture of potassium tetraborate and boric acid. The uranium articles are anodized at a temperature greater than about 75.degree. C. with a current flow of less than about 0.036 A/cm.sup.2 of surface area while the pH of the solution is maintained in a range of about 2 to 11.5. The pH values of the aqueous solution and the low current density utilized during the electrolysis prevent excessive dissolution of the uranium and porosity in the film or watering. The relatively high temperature of the electrolyte bath inhibits hydration and the attendant deleterious pitting so as to enhance corrosion resistance of the anodized coating.

Detecting Cavitation Pitting Without Disassembly

NASA Technical Reports Server (NTRS)

Barkhoudarian, S.

1986-01-01

Technique for detecting cavitation pitting in pumps, turbines, and other machinery uses low-level nuclear irradiation. Isotopes concentrated below surface emit gamma radiation, a portion of which is attenuated by overlying material. Where there are cavitation pits, output of gamma-ray detector fluctuates as detector is scanned near pits. Important to detect cavitation pits because nozzle, turbine blade, or other pump component weakened by cavitation could fail catastrophically and cause machine to explode.

Corrosion pitting of SiC by molten salts

NASA Technical Reports Server (NTRS)

Jacobson, N. S.; Smialek, J. L.

1986-01-01

The corrosion of SiC by thin films of Na2CO3 and Na2SO4 at 1000 C is characterized by a severe pitting attack of the SiC substrate. A range of different Si and SiC substrates were examined to isolate the factors critical to pitting. Two types of pitting attack are identified: attack at structural discontinuities and a crater-like attack. The crater-like pits are correlated with bubble formation during oxidation of the SiC. It appears that bubbles create unprotected regions, which are susceptible to enhanced attack and, hence, pit formation.

Targeted overexpression of calcitonin in gonadotrophs of transgenic mice leads to chronic hypoprolactinemia.

PubMed

Yuan, Ren; Kulkarni, Trupti; Wei, Fu; Shah, Girish V

2005-01-14

It was previously shown that calcitonin-like pituitary peptide (pit-CT) is synthesized and secreted by gonadotrophs, and pit-CT inhibits PRL gene transcription and lactotroph cell proliferation. Present studies examined long-term consequences of pit-CT overexpression on the functioning of mouse anterior pituitary (AP) gland. Targeted overexpression of pit-CT in gonadotrophs of mouse pituitaries was achieved by generating mice overexpressing bovine luteinizing hormone (LH)-alpha subunit promoter-pit-CT cDNA transgene. Transgenic (pit-CT+) mice displayed chronic but selective overexpression of pit-CT in gonadotrophs. The mice also displayed a dramatic decline in PRL gene expression as assessed by PRL mRNA abundance, PRL immunohistochemistry (IHC) and serum PRL levels. LH secretion in pit-CT+ mice was also reduced, without any change in FSH secretion. Reproductive abnormalities such as prolonged estrous cycles, reduced pregnancy rate, delivery of smaller litters, increased neonatal mortality and deficient lactation were also observed. Administration of PRL during early pregnancy significantly increased the pregnancy rate and neonatal survival of newborns. These results demonstrate that overexpression of pit-CT leads to chronic hypoprolactinemia and reproductive dysfunction in female mice, and reinforces the possibility that gonadotroph-derived pit-CT is an important paracrine regulator of lactotroph function.

Research on horizontal displacement monitoring method of deep foundation pit based on laser projecting sensing technology

NASA Astrophysics Data System (ADS)

Liu, Peng; Xie, Shulin; Zhang, Lixiao; Zhou, Guangyi; Zhao, Xuefeng

2018-03-01

A certain level of horizontal displacement will occur during excavation or subsequent construction of deep foundation pit. If the support is improper and the horizontal displacement of the foundation pit is too large, it will cause collapse and even affect the buildings around the foundation pit, which will endanger people's life and property. Therefore, the horizontal displacement monitoring of deep foundation pit becomes more and more important. At present, the electronic total station is often used to monitor the horizontal displacement of the foundation pit, but this monitoring method is expensive, prone to accidental errors, and can not be used for real-time monitoring. Therefore, a method of monitoring the horizontal displacement of deep foundation pit by using laser projection sensing technique is proposed in this paper. The horizontal displacement of the foundation pit is replaced by the displacement of the laser spot emitted by the laser, and the horizontal displacement of the foundation pit can be obtained by identifying the displacement of the laser spot projected on the screen. A series of experiments show that the accuracy of this monitoring method meets the engineering requirements and greatly reduces the cost, which provides a new technology for the displacement monitoring of deep foundation pit.

Chemical evaluation of soil-solution in acid forest soils

USGS Publications Warehouse

Lawrence, G.B.; David, M.B.

1996-01-01

Soil-solution chemistry is commonly studied in forests through the use of soil lysimeters.This approach is impractical for regional survey studies, however, because lysimeter installation and operation is expensive and time consuming. To address these problems, a new technique was developed to compare soil-solution chemistry among red spruce stands in New York, Vermont, New Hampshire, Maine. Soil solutions were expelled by positive air pressure from soil that had been placed in a sealed cylinder. Before the air pressure was applied, a solution chemically similar to throughfall was added to the soil to bring it to approximate field capacity. After the solution sample was expelled, the soil was removed from the cylinder and chemically analyzed. The method was tested with homogenized Oa and Bs horizon soils collected from a red spruce stand in the Adirondack Mountains of New York, a red spruce stand in east-central Vermont, and a mixed hardwood stand in the Catskill Mountains of New York. Reproducibility, effects of varying the reaction time between adding throughfall and expelling soil solution (5-65 minutes) and effects of varying the chemical composition of added throughfall, were evaluated. In general, results showed that (i) the method was reproducible (coefficients of variation were generally < 15%), (ii) variations in the length of reaction-time did not affect expelled solution concentrations, and (iii) adding and expelling solution did not cause detectable changes in soil exchange chemistry. Concentrations of expelled solutions varied with the concentrations of added throughfall; the lower the CEC, the more sensitive expelled solution concentrations were to the chemical concentrations of added throughfall. Addition of a tracer (NaBr) showed that the expelled solution was a mixture of added solution and solution that preexisted in the soil. Comparisons of expelled solution concentrations with concentrations of soil solutions collected by zero-tension and tension lysimetry indicated that expelled solution concentrations were higher than those obtained with either type of lysimeter, although there was less difference with tension lysimeters than zero-tension lysimeters. The method used for collection of soil solution should be taken into consideration whenever soil solution data are being interpreted.

Solution chemistry of carbonate minerals and its effects on the flotation of hematite with sodium oleate

NASA Astrophysics Data System (ADS)

Li, Dong; Yin, Wan-zhong; Xue, Ji-wei; Yao, Jin; Fu, Ya-feng; Liu, Qi

2017-07-01

The effects of carbonate minerals (dolomite and siderite) on the flotation of hematite using sodium oleate as a collector were investigated through flotation tests, supplemented by dissolution measurements, solution chemistry calculations, zeta-potential measurements, Fourier transform infrared (FTIR) spectroscopic studies, and X-ray photoelectron spectroscopy (XPS) analyses. The results of flotation tests show that the presence of siderite or dolomite reduced the recovery of hematite and that the inhibiting effects of dolomite were stronger. Dissolution measurements, solution chemistry calculations, and flotation tests confirmed that both the cations (Ca2+ and Mg2+) and CO3 2- ions dissolved from dolomite depressed hematite flotation, whereas only the CO3 2- ions dissolved from siderite were responsible for hematite depression. The zeta-potential, FTIR spectroscopic, and XPS analyses indicated that Ca2+, Mg2+, and CO3 2- (HCO3 -) could adsorb onto the hematite surface, thereby hindering the adsorption of sodium oleate, which was the main reason for the inhibiting effects of carbonate minerals on hematite flotation.

Are pit latrines in urban areas of Sub-Saharan Africa performing? A review of usage, filling, insects and odour nuisances.

PubMed

Nakagiri, Anne; Niwagaba, Charles B; Nyenje, Philip M; Kulabako, Robinah N; Tumuhairwe, John B; Kansiime, Frank

2016-02-04

A pit latrine is the most basic form of improved sanitation which is currently used by a number of people around the globe. In spite of the wide spread use, known successes and advantages associated with pit latrines, they have received little attention in form of research and development. This review focuses on the usage and performance (filling, smell and insect nuisance) of pit latrines in urban areas of sub-Saharan Africa (SSA) and proposes approaches for their improvements and sustainability. Current pit latrine usage within urban SSA was calculated from Joint Monitoring Programme (JMP) water and sanitation country-files. We conducted a literature search and review of documents on pit latrine usage, filling, smell and insect nuisances in urban areas of SSA. Findings of the review are presented and discussed in this paper. Pit latrines are in use by more than half the urban population in SSA and especially among low income earners. An additional 36 million people in urban areas of SSA have adopted the pit latrine since 2007. However, their performance is unsatisfactory. Available literature shows that contributions have been made to address shortfalls related to pit latrine use in terms of science and technological innovations. However, further research is still needed. Any technology and process management innovations to pit latrines should involve scientifically guided approaches. In addition, development, dissemination and enforcement of minimum pit latrine design standards are important while the importance of hygienic latrines should also be emphasized.

Entertaining Chemistry--Two Colorful Reactions.

ERIC Educational Resources Information Center

Elsworth, John F.

2000-01-01

Describes two related color-change reactions that are relatively easy and safe to demonstrate. In the "Sunday School Reaction", a black and a white solution are mixed to form a white solution. In the "South Africa Reaction", a series of black, brown, red, and white solutions are mixed to form a clear, colorless solution. (WRM)

NELL-1 increases pre-osteoblast mineralization using both phosphate transporter Pit1 and Pit2

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

Cowan, Catherine M.; Dental and Craniofacial Research Institute and Section of Orthodontics, School of Dentistry, University of California, Los Angeles, 40833 Le Conte Ave, Los Angeles, CA 90095; Zhang, Xinli

2012-06-08

Highlights: Black-Right-Pointing-Pointer NELL-1 accelerates extracellular matrix mineralization in MC3T3-E1 pre-osteoblasts. Black-Right-Pointing-Pointer NELL-1 significantly increases intracellular inorganic phosphate levels. Black-Right-Pointing-Pointer NELL-1 positively regulates osteogenesis but not proliferation in MC3T3-E1 cells. Black-Right-Pointing-Pointer NELL-1 regulates inorganic phosphate transporter activity. -- Abstract: NELL-1 is a potent osteoinductive molecule that enhances bone formation in multiple animal models through currently unidentified pathways. In the present manuscript, we hypothesized that NELL-1 may regulate osteogenic differentiation accompanied by alteration of inorganic phosphate (Pi) entry into the osteoblast via sodium dependent phosphate (NaPi) transporters. To determine this, MC3T3-E1 pre-osteoblasts were cultured in the presence of recombinant human (rh)NELL-1 ormore » rhBMP-2. Analysis was performed for intracellular Pi levels through malachite green staining, Pit-1 and Pit-2 expression, and forced upregulation of Pit-1 and Pit-2. Results showed rhNELL-1 to increase MC3T3-E1 matrix mineralization and Pi influx associated with activation of both Pit-1 and Pit-2 channels, with significantly increased Pit-2 production. In contrast, Pi transport elicited by rhBMP-2 showed to be associated with increased Pit-1 production only. Next, neutralizing antibodies against Pit-1 and Pit-2 completely abrogated the Pi influx effect of rhNELL-1, suggesting rhNELL-1 is dependent on both transporters. These results identify one potential mechanism of action for rhNELL-1 induced osteogenesis and highlight a fundamental difference between NELL-1 and BMP-2 signaling.« less

Tridimensional morphology and kinetics of etch pit on the {l_brace}0 0 0 1{r_brace} plane of sapphire crystal

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

Zhang Lunyong; Sun Jianfei, E-mail: jfsun_hit@263.net; Zuo Hongbo

2012-08-15

The tridimensional morphology and etching kinetics of the etch pit on the C-{l_brace}0 0 0 1{r_brace} plane of sapphire crystal ({alpha}-Al{sub 2}O{sub 3}) in molten KOH were studied experimentally. It was shown that the etch pit takes on tridimensional morphologies with triangular symmetry same as the symmetric property of the sapphire crystal. Pits like centric and eccentric triangular pyramid as well as hexagonal pyramid were observed, but the latter is less in density. In-depth analyses show the side walls of the etch pits belong to the {l_brace}1 1{sup Macron} 0 2{sup Macron }{r_brace} family, and the triangular pit contains edgesmore » full composed by Al{sup 3+} ions on the etching surface so it is more stable than the hexagonal pit since its edges on the etching surface contains Al{sup 2+} ions. The etch pits developed in a manner of kinematic wave by the step moving with constant speed, which is controlled by the chemical reaction with activation energy of 96.6 kJ/mol between Al{sub 2}O{sub 3} and KOH. - Graphical abstract: Schematic showing the atomic configuration of the predicted side walls of regular triangular pyramid shaped etch pit on the C-{l_brace}0 0 0 1{r_brace} plane of sapphire crystal. Highlights: Black-Right-Pointing-Pointer Observed the tridimensional morphology of etch pits. Black-Right-Pointing-Pointer Figured out the atomic configuration origin of the etch pits. Black-Right-Pointing-Pointer Quantitatively determined the etch rates of the etch pits.« less

Effector and central memory T helper 2 cells respond differently to peptide immunotherapy

PubMed Central

Mackenzie, Karen J.; Nowakowska, Dominika J.; Leech, Melanie D.; McFarlane, Amanda J.; Wilson, Claire; Fitch, Paul M.; O’Connor, Richard A.; Howie, Sarah E. M.; Schwarze, Jürgen; Anderton, Stephen M.

2014-01-01

Peptide immunotherapy (PIT) offers realistic prospects for the treatment of allergic diseases, including allergic asthma. Much is understood of the behavior of naive T cells in response to PIT. However, treatment of patients with ongoing allergic disease requires detailed understanding of the responses of allergen-experienced T cells. CD62L expression by allergen-experienced T cells corresponds to effector/effector memory (CD62Llo) and central memory (CD62Lhi) subsets, which vary with allergen exposure (e.g., during, or out with, pollen season). The efficacy of PIT on different T helper 2 (Th2) cell memory populations is unknown. We developed a murine model of PIT in allergic airway inflammation (AAI) driven by adoptively transferred, traceable ovalbumin-experienced Th2 cells. PIT effectively suppressed AAI driven by unfractionated Th2 cells. Selective transfer of CD62Lhi and CD62Llo Th2 cells revealed that these two populations behaved differently from one another and from previously characterized (early deletional) responses of naive CD4+ T cells to PIT. Most notably, allergen-reactive CD62Llo Th2 cells were long-lived within the lung after PIT, before allergen challenge, in contrast to CD62Lhi Th2 cells. Despite this, PIT was most potent against CD62Llo Th2 cells in protecting from AAI, impairing their ability to produce Th2 cytokines, whereas this capacity was heightened in PIT-treated CD62Lhi Th2 cells. We conclude that Th2 cells do not undergo an early deletional form of tolerance after PIT. Moreover, memory Th2 subsets respond differently to PIT. These findings have implications for the clinical translation of PIT in different allergic scenarios. PMID:24516158

Illuminating Anaerobic Microbial Community and Cooccurrence Patterns across a Quality Gradient in Chinese Liquor Fermentation Pit Muds.

PubMed

Hu, Xiaolong; Du, Hai; Ren, Cong; Xu, Yan

2016-04-01

Fermentation pit mud, an important reservoir of diverse anaerobic microorganisms, is essential for Chinese strong-aroma liquor production. Pit mud quality, according to its sensory characteristics, can be divided into three grades: degraded, normal, and high quality. However, the relationship between pit mud microbial community and pit mud quality is poorly understood, as are microbial associations within the pit mud ecosystem. Here, microbial communities at these grades were compared using Illumina MiSeq sequencing of the variable region V4 of the 16S rRNA gene. Our results revealed that the pit mud microbial community was correlated with its quality and environmental factors. Species richness, biodiversity, and relative and/or absolute abundances of Clostridia,Clostridium kluyveri, Bacteroidia, and Methanobacteria significantly increased, with corresponding increases in levels of pH, NH4 (+), and available phosphorus, from degraded to high-quality pit muds, while levels of Lactobacillus, dissolved organic carbon, and lactate significantly decreased, with normal samples in between. Furthermore, 271 pairs of significant and robust correlations (cooccurrence and negative) were identified from 76 genera using network analysis. Thirteen hubs of cooccurrence patterns, mainly under the Clostridia,Bacteroidia,Methanobacteria, and Methanomicrobia, may play important roles in pit mud ecosystem stability, which may be destroyed with rapidly increased levels of lactic acid bacteria (Lactobacillus,Pediococcus, and Streptococcus). This study may help clarify the relationships among microbial community, environmental conditions, and pit mud quality, allow the improvement of pit mud quality by using bioaugmentation and controlling environmental factors, and shed more light on the ecological rules guiding community assembly in pit mud. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Inconsistent identification of pit bull-type dogs by shelter staff.

PubMed

Olson, K R; Levy, J K; Norby, B; Crandall, M M; Broadhurst, J E; Jacks, S; Barton, R C; Zimmerman, M S

2015-11-01

Shelter staff and veterinarians routinely make subjective dog breed identification based on appearance, but their accuracy regarding pit bull-type breeds is unknown. The purpose of this study was to measure agreement among shelter staff in assigning pit bull-type breed designations to shelter dogs and to compare breed assignments with DNA breed signatures. In this prospective cross-sectional study, four staff members at each of four different shelters recorded their suspected breed(s) for 30 dogs; there was a total of 16 breed assessors and 120 dogs. The terms American pit bull terrier, American Staffordshire terrier, Staffordshire bull terrier, pit bull, and their mixes were included in the study definition of 'pit bull-type breeds.' Using visual identification only, the median inter-observer agreements and kappa values in pair-wise comparisons of each of the staff breed assignments for pit bull-type breed vs. not pit bull-type breed ranged from 76% to 83% and from 0.44 to 0.52 (moderate agreement), respectively. Whole blood was submitted to a commercial DNA testing laboratory for breed identification. Whereas DNA breed signatures identified only 25 dogs (21%) as pit bull-type, shelter staff collectively identified 62 (52%) dogs as pit bull-type. Agreement between visual and DNA-based breed assignments varied among individuals, with sensitivity for pit bull-type identification ranging from 33% to 75% and specificity ranging from 52% to 100%. The median kappa value for inter-observer agreement with DNA results at each shelter ranged from 0.1 to 0.48 (poor to moderate). Lack of consistency among shelter staff indicated that visual identification of pit bull-type dogs was unreliable. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Controlling potential barrier height by changing V-shaped pit size and the effect on optical and electrical properties for InGaN/GaN based light-emitting diodes

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

Okada, Narihito, E-mail: nokada@yamaguchi-u.ac.jp; Kashihara, Hiroyuki; Sugimoto, Kohei

2015-01-14

The internal quantum efficiency (IQE) of InGaN/GaN multiple quantum wells (MQWs) with blue light emission was improved by inserting an InGaN/GaN superlattice (SL) beneath the MQWs. While the SL technique is useful for improving the light-emitting diode (LED) performance, its effectiveness from a multilateral point of view requires investigation. V-shaped pits (V-pits), which generate a potential barrier and screen the effect of the threading dislocation, are one of the candidates for increasing the light emission efficiency of LEDs exceptionally. In this research, we investigated the relationship between the V-pit and SL and revealed that the V-pit diameter is strongly correlatedmore » with the IQE by changing the number of SL periods. Using scanning near-field optical microscopy and photoluminescence measurements, we demonstrated the distinct presence of the potential barrier formed by the V-pits around the dislocations. The relationship between the V-pit and the number of SL periods resulted in changing the potential barrier height, which is related to the V-pit diameter determined by the number of SL periods. In addition, we made an attempt to insert pit expansion layers (PELs) composed of combination of SL and middle temperature grown GaN layer instead of only SL structure. As a result of the evaluation of LEDs using SL or PEL, the EL intensity was strongly related to pit diameter regardless of the structures to form the V-pits. In addition, it was clear that larger V-pits reduce the efficiency droop, which is considered to be suppression of the carrier loss at high injection current.« less

Mineral Type and Solution Chemistry Affect the Structure and Composition of Actively Growing Bacterial Communities as Revealed by Bromodeoxyuridine Immunocapture and 16S rRNA Pyrosequencing.

PubMed

Kelly, L C; Colin, Y; Turpault, M-P; Uroz, S

2016-08-01

Understanding how minerals affect bacterial communities and their in situ activities in relation to environmental conditions are central issues in soil microbial ecology, as minerals represent essential reservoirs of inorganic nutrients for the biosphere. To determine the impact of mineral type and solution chemistry on soil bacterial communities, we compared the diversity, composition, and functional abilities of a soil bacterial community incubated in presence/absence of different mineral types (apatite, biotite, obsidian). Microcosms were prepared containing different liquid culture media devoid of particular essential nutrients, the nutrients provided only in the introduced minerals and therefore only available to the microbial community through mineral dissolution by biotic and/or abiotic processes. By combining functional screening of bacterial isolates and community analysis by bromodeoxyuridine DNA immunocapture and 16S rRNA gene pyrosequencing, we demonstrated that bacterial communities were mainly impacted by the solution chemistry at the taxonomic level and by the mineral type at the functional level. Metabolically active bacterial communities varied with solution chemistry and mineral type. Burkholderia were significantly enriched in the obsidian treatment compared to the biotite treatment and were the most effective isolates at solubilizing phosphorous or mobilizing iron, in all the treatments. A detailed analysis revealed that the 16S rRNA gene sequences of the OTUs or isolated strains assigned as Burkholderia in our study showed high homology with effective mineral-weathering bacteria previously recovered from the same experimental site.

[Microsite characteristics of pit and mound and their effects on the vegetation regeneration in Pinus koraiensis-dominated broadleaved mixed forest].

PubMed

Du, Shan; Duan, Wen-Biao; Wang, Li-Xia; Chen, Li-Xin; Wei, Quan-Shuai; Li, Meng; Wang, Li-dong

2013-03-01

Abstract: An investigation was conducted in a 2.55 hm2 plot of Pinus koraiensis-dominated broad-leaved mixed forest to study the microsite characteristics of pit and mound formed by 42 treefalls and the status of vegetation regeneration on the microsites. The soil water content, soil temperature, relative air humidity, and photosynthetically active radiation (PAR) on five microsites (mound top, mound face, pit wall, pit bottom, and intact forest floor) were measured. Among the five mirosites, mound top had the highest PAR (527.9 micromol.m-2.s-1 ) while intact forest floor had the lowest one (58.7 micromol.m-2.s-), mound top had the highest soil temperature (16.0 degrees C) but pit bottom had the lowest one (13.3 degrees C), pit bottom had the highest soil water content (34.6%) but mound face had the lowest one (0.5%), and intact forest floor had the highest relative air humidity (75.9%) but mound top had the lowest one (68.0%). The frequency of forming pit/ mound complex by the tree species was decreased in the order of Pinus koraiensis (42. 9%) >Picea asperata (31.0%) > Betula platyphylla (16.7%) > Abies fabri (7. 1%) > Prunus padus (2.4%). Among the 42 treefalls, two-thirds of them were in northwest direction. The treefalls volume had significant positive correlations with pit depth, pit length, mound height, and mound width, but negative correlation with mound thickness. The treefall mean diameter at breast height had significant positive correlations with pit width (r=0.328, P=0.017) and pit length (r=0.527, P= 0). The tree species richness at the microsites decreased in the order of intact forest floor > pit > mound, and the tree species coverage was in the sequence of intact forest floor > pit > mound.

High-sensitivity chemiluminescence immunoassays for detection of growth hormone doping in sports.

PubMed

Bidlingmaier, Martin; Suhr, Jennifer; Ernst, Andrea; Wu, Zida; Keller, Alexandra; Strasburger, Christian J; Bergmann, Andreas

2009-03-01

Recombinant human growth hormone (rhGH) is abused in sports, but adequate routine doping tests are lacking. Analysis of serum hGH isoform composition has been shown to be effective in detecting rhGH doping. We developed and validated selective immunoassays for isoform analysis with potential utility for screening and confirmation in doping tests. Monoclonal antibodies with preference for pituitary hGH (phGH) or rhGH were used to establish 2 pairs of sandwich-type chemiluminescence assays with differential recognition of rhGH (recA and recB) and phGH (pitA and pitB). We analyzed specimens from volunteers before and after administration of rhGH and calculated ratios between the respective rec- and pit-assay results. Functional sensitivities were <0.05 microg/L, with intra- and interassay imprecision < or =8.4% and < or =13.7%, respectively. In 2 independent cohorts of healthy subjects, rec/pit ratios (median range) were 0.84 (0.09-1.32)/0.81 (0.27-1.21) (recA/pitA) and 0.68 (0.08-1.20)/0.80 (0.25-1.36) (recB/pitB), with no sex difference. In 20 recreational athletes, ratios (median SD) increased after a single injection of rhGH, reaching 350% (73%) (recA/pitA) and 400% (93%) (recB/pitB) of baseline ratios. At a moderate dose (0.033 mg/kg), mean recA/pitA and recB/pitB ratios remained significantly increased for 18 h (men) and 26 h (women). After high-dose rhGH (0.083 mg/kg), mean rec/pit ratios remained increased for 32 h (recA/pitA) and 34 h (recB/pitB) in men and were still increased after 36 h in women. Using sensitive chemiluminescence assays with preferential recognition of phGH or rhGH, detection of a single injection of rhGH was possible for up to 36 h.

Interface chemistry and surface morphology evolution study for InAs/Al2O3 stacks upon in situ ultrahigh vacuum annealing

NASA Astrophysics Data System (ADS)

Wang, Xinglu; Qin, Xiaoye; Wang, Wen; Liu, Yue; Shi, Xiaoran; Sun, Yong; Liu, Chen; Zhao, Jiali; Zhang, Guanhua; Liu, Hui; Cho, Kyeongjae; Wu, Rui; Wang, Jiaou; Zhang, Sen; Wallace, Robert M.; Dong, Hong

2018-06-01

A systematic study of the interfacial chemistry for the HCl pretreated and native oxide InAs(100) samples upon atomic layer deposition (ALD) of Al2O3, and the post deposition annealing (PDA) process has been carried out, using in situ synchrotron radiation photoelectron spectroscopy. The "clean up" effect for the native oxide sample is detected, but it is not observed for the HCl pretreated sample. The out-diffusion and desorption of both In and As oxides have been characterized during the ALD process and the following PDA process. The surface morphology evolution during the PDA process is studied by in situ photo-emission electron microscopy. The bubbles emerged after PDA at 360 °C and grew up at 370 °C. After PDA at 400 °C and at higher temperatures, pits are seen in some areas, and the tear up of the Al2O3 film is seen in other areas with the formation of indium droplets. This study gives insight in the mechanism of elemental diffusion/desorption, which may associate the reliability of III-V semiconductor based devices.

Baseline Risk Assessment for the F-Area Burning/Rubble Pits and Rubble Pit

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

Palmer, E.

This document provides an overview of the Savannah River Site (SRS) and a description of the F-Area Burning/Rubble Pits (BRPs) and Rubble Pit (RP) unit. It also describes the objectives and scope of the baseline risk assessment (BRA).

Site-controlled crystalline InN growth from the V-pits of a GaN substrate

NASA Astrophysics Data System (ADS)

Kuo, Chien-Ting; Hsu, Lung-Hsing; Lai, Yung-Yu; Cheng, Shan-Yun; Kuo, Hao-Chung; Lin, Chien-Chung; Cheng, Yuh-Jen

2017-05-01

A site-controlled crystalline InN growth from the V-pits of a GaN substrate was investigated. The V- pits were fabricated by epitaxial lateral growth of GaN over SiO2 disks patterned on a sapphire substrate. InN crystals were found to preferably grow on the inclined {10-11} crystal planes of the V-pits. A V-pit size of 1 μm or less can provide precise site-controlled InN nucleation at the V-pit bottom, while no InN was grown on the rest of the exposed GaN surfaces. The site-controlled nucleation is attributed to the low surface energy point created by the converging six {10-11} crystal facets at the V-pit bottom. When In source supply is below a certain value, this V-pit bottom is the only location able to aggregate enough active sources to start nucleation, thereby providing site-controlled crystal growth.

Dependence of Crystallographic Orientation on Pitting Corrosion Behavior of Ni-Fe-Cr Alloy 028

NASA Astrophysics Data System (ADS)

Zhang, LiNa; Szpunar, Jerzy A.; Dong, JianXin; Ojo, Olanrewaju A.; Wang, Xu

2018-06-01

The influence of crystallographic orientation on the pitting corrosion behavior of Ni-Fe-Cr alloy 028 was studied using a combination of X-ray diffraction (XRD), electron backscatter diffraction (EBSD), potentiodynamic polarization technique, and atomic force microscopy (AFM). The results show that there is anisotropy of pitting corrosion that strongly depends on crystallographic orientation of the surface plane. The distribution of pit density in a standard stereographic triangle indicates that the crystallographic planes close to {100} are more prone to pitting corrosion compared to planes {110} and {111}. The surface energy calculation of (001) and (111) shows that the plane with a high atomic packing density has a low surface energy with concomitant strong resistance to pitting corrosion. A correlation function between crystallographic orientation and pitting corrosion susceptibility suggests a method that not only predicts the pitting resistance of known textured materials, but also could help to improve corrosion resistance by controlling material texture.

Tale of two pit lakes: initial results of a three-year study of the Main Zone and Waterline pit lakes near Houston, British Columbia, Canada

USGS Publications Warehouse

Crusius, John; Pieters, R.; Leung, A.; Whittle, P.; Pedersen, T.; Lawrence, G.; McNee, J.J.

2003-01-01

Pit lakes are becoming increasingly common in North America as well as in the rest of the world. They are created as openpit mines fill passively with ground water and surface inflows on cessation of mining activity. In many instances, the water quality in these pit lakes does not meet regulatory requirements due to a number of influences. The most important are the oxidation of sulfide minerals and the associated release of acid and metals and the flushing of soluble metals during pit filling. Examples of pit lakes with severe water-quality problems include the Berkeley Pit lake (Butte, MT) and the Liberty Pit lake (Nevada), whose waters are characterized by a pH near 3 and Cu concentrations as high as ~150 mg/L (Miller et al., 1996; Davis and Eary, 1997). The importance of the problem can be seen in the fact that some of these sites in the United States are Superfund sites.

Heterogeneous nucleation of pits via step pinning during Si(100) homoepitaxy

DOE PAGES

Yitamben, Esmeralda; Butera, Robert E.; Swartzentruber, Brian S.; ...

2017-10-16

Using scanning tunneling microscopy (STM), we investigate oxide-induced growth pits in Si thin films deposited by molecular beam epitaxy. In the transition temperature range from 2D adatom islanding to step-flow growth, systematic controlled air leaks into the growth chamber induce pits in the growth surface. We show that pits are also correlated with oxygen-contaminated flux from Si sublimation sources. From a thermodynamic standpoint, multilayer growth pits are unexpected in relaxed homoepitaxial growth, whereas oxidation is a known cause for step-pinning, roughening, and faceting on elemental surfaces, both with and without growth flux. Not surprisingly, pits are thermodynamically metastable and healmore » by annealing to recover a smooth periodic step arrangement. STM reveals new details about the pits' atomistic origins and growth dynamics. Here, we give a model for heterogeneous nucleation of pits by preferential adsorption of Å-sized oxide nuclei at intrinsic growth antiphase boundaries, and subsequent step pinning and bunching around the nuclei.« less

Single Etch-Pit Shape on Off-Angled 4H-SiC(0001) Si-Face Formed by Chlorine Trifluoride

NASA Astrophysics Data System (ADS)

Hatayama, Tomoaki; Tamura, Tetsuya; Yano, Hiroshi; Fuyuki, Takashi

2012-07-01

The etch pit shape of an off-angled 4H-SiC Si-face formed by chlorine trifluoride (ClF3) in nitrogen (N2) ambient has been studied. One type of etch pit with a crooked hexagonal shape was formed at an etching temperature below 500 °C. The angle of the etch pit measured from a cross-sectional atomic force microscopy image was about 10° from the [11bar 20] view. The dislocation type of the etch pit was discussed in relation to the etch pit shape and an electron-beam-induced current image.

Study on the Accident-causing of Foundation Pit Engineering

NASA Astrophysics Data System (ADS)

Shuicheng, Tian; Xinyue, Zhang; Pengfei, Yang; Longgang, Chen

2018-05-01

With the development of high-rise buildings and underground space, a large number of foundation pit projects have occurred. Frequent accidents of it cause great losses to the society, how to reduce the frequency of pit accidents has become one of the most urgent problems to be solved. Therefore, analysing the influencing factors of foundation pit engineering accidents and studying the causes of foundation pit accidents, which of great significance for improving the safety management level of foundation pit engineering and reducing the incidence of foundation pit accidents. Firstly, based on literature review and questionnaires, this paper selected construction management, survey, design, construction, supervision and monitoring as research factors, we used the AHP method and the Dematel method to analyze the weights of various influencing factors to screen indicators to determine the ultimate system of accidents caused by foundation pit accidents; Secondly, SPSS 21.0 software was used to test the reliability and validity of the recovered questionnaire data. AMOS 7.0 software was used to fit, evaluate, and explain the set model; Finally, this paper analysed the influencing factors of foundation pit engineering accidents, corresponding management countermeasures and suggestions were put forward.

The effect of pits of different sizes on ultrasonic shear wave signals

NASA Astrophysics Data System (ADS)

Howard, Richard; Cegla, Frederic

2018-04-01

The use of 0-degree shear waves in NDE and SHM has become more commonplace as the disadvantage of coupling has been eliminated by permanent sensor installations or the use of non-contact transducers, such as EMATs. While the effect of rough surfaces and flat bottom holes on shear waves has been studied in depth, the effect of more complex geometries, such as pitting, has not. In this work, 3D finite element simulations are used to explore the reflection and scattering characteristics of shear bulk waves from pits. Specifically, three scenarios have been investigated, the effect on shear waves of: a sloped backwall; pitting directly under the transducer; and the effect of pits with variable pit position. High speed GPU finite element models enabled a wide range of pit radii and positions to be modeled. Hemispherical pits were used throughout. Key findings of the study are that the anisotropic effects that are clearly visible on sloped reflecting surfaces can also be measured on pits that are located not directly below the center of a shear wave transducer. These anisotropic effects are due to the nature of shear wave polarization. This can potentially be used for better defect characterization purposes.

Corrosion behavior of aluminum-alumina composites in aerated 3.5 percent chloride solution

NASA Astrophysics Data System (ADS)

Acevedo Hurtado, Paul Omar

Aluminum based metal matrix composites are finding many applications in engineering. Of these Al-Al2O3 composites appear to have promise in a number of defense applications because of their mechanical properties. However, their corrosion behavior remains suspect, especially in marine environments. While efforts are being made to improve the corrosion resistance of Al-Al2O3 composites, the mechanism of corrosion is not well known. In this study, the corrosion behavior of powder metallurgy processed Al-Cu alloy reinforced with 10, 15, 20 and 25 vol. % Al2O3 particles (XT 1129, XT 2009, XT 2048, XT 2031) was evaluated in aerated 3.5% NaCl solution using microstructural and electrochemical measurements. AA1100-O and AA2024T4 monolithic alloys were also studied for comparison purposes. The composites and unreinforced alloys were subjected to potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) testing. Addition of 25 vol. % Al2O 3 to the base alloys was found to increase its corrosion resistance considerably. Microstructural studies revealed the presence of intermetallic Al2Cu particles in these composites that appeared to play an important role in the observations. Pitting potential for these composites was near corrosion potential values, and repassivation potential was below the corresponding corrosion potential, indicating that these materials begin to corrode spontaneously as soon as they come in contact with the 3.5 % NaCl solution. EIS measurements indicate the occurrence of adsorption/diffusion phenomena at the interface of the composites which ultimately initiate localized or pitting corrosion. Polarization resistance values were extracted from the EIS data for all the materials tested. Electrically equivalent circuits are proposed to describe and substantiate the corrosive processes occurring in these Al-Al2O 3 composite materials.

Scaling theory in a model of corrosion and passivation.

PubMed

Aarão Reis, F D A; Stafiej, Janusz; Badiali, J-P

2006-09-07

We study a model for corrosion and passivation of a metallic surface after small damage of its protective layer using scaling arguments and simulation. We focus on the transition between an initial regime of slow corrosion rate (pit nucleation) to a regime of rapid corrosion (propagation of the pit), which takes place at the so-called incubation time. The model is defined in a lattice in which the states of the sites represent the possible states of the metal (bulk, reactive, and passive) and the solution (neutral, acidic, or basic). Simple probabilistic rules describe passivation of the metal surface, dissolution of the passive layer, which is enhanced in acidic media, and spatially separated electrochemical reactions, which may create pH inhomogeneities in the solution. On the basis of a suitable matching of characteristic times of creation and annihilation of pH inhomogeneities in the solution, our scaling theory estimates the average radius of the dissolved region at the incubation time as a function of the model parameters. Among the main consequences, that radius decreases with the rate of spatially separated reactions and the rate of dissolution in acidic media, and it increases with the diffusion coefficient of H(+) and OH(-) ions in solution. The average incubation time can be written as the sum of a series of characteristic times for the slow dissolution in neutral media, until significant pH inhomogeneities are observed in the dissolved cavity. Despite having a more complex dependence on the model parameters, it is shown that the average incubation time linearly increases with the rate of dissolution in neutral media, under the reasonable assumption that this is the slowest rate of the process. Our theoretical predictions are expected to apply in realistic ranges of values of the model parameters. They are confirmed by numerical simulation in two-dimensional lattices, and the expected extension of the theory to three dimensions is discussed.

CALL FOR ABSTRACTS - PIT LAKES 2004

EPA Science Inventory

This call for abstracts is for the 11/16-18/2004 Pit Lakes 2004 meeting held in Reno, NV. This conference will provide a forum for the exchange of scientific information on current domestic and international pit lake approaches, including pit lakes from arid and wet regions throu...

Steam generator issues in the United States

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

Strosnider, J.R.

1997-02-01

Alloy 600 steam generator tubes in the US have exhibited degradation mechanisms similar to those observed in other countries. Effective programs have been implemented to address several degradation mechanisms including: wastage; mechanical wear; pitting; and fatigue. These degradation mechanisms are fairly well understood as indicated by the ability to effectively mitigate/manage them. Stress corrosion cracking (SCC) is the dominant degradation mechanism in the US. SCC poses significant inspection and management challenges to the industry and the regulators. The paper also addresses issues of research into SCC, inspection programs, plugging, repair strategies, water chemistry, and regulatory control. Emerging issues in themore » US include: parent tube cracking at sleeve joints; detection and repair of circumferential cracks; free span cracking; inspection and cracking of dented regions; and severe accident analysis.« less

Surface Dynamics of Unipolar Arcing

DTIC Science & Technology

1989-12-01

slioising bulk copper deposition. (6.4X)( i10 ) Figure 20. Copper deposition on a steel surface shoiing a cor relation bet’seeni greater pitting...pit’s depth and its width. 1. Arc damage - a heating phenomenon To study the effect of the same laser shot. and the same unipolar arc. on two...between pit depth and diameter for pitting on the copper films. This conclusion comes from the fact that in many cases pits with relatively smaller

Method for Identifying Lava Tubes Among Pit Craters Using Brightness Profile Across Pits on the Moon or Mars

NASA Astrophysics Data System (ADS)

Jung, Jongil; Hong, Ik-Seon; Cho, Eunjin; Yi, Yu

2016-03-01

Caves can serve as major outposts for future human exploration of the Moon and Mars. In addition, caves can protect people and electronic equipment from external hazards such as cosmic ray radiation and meteorites impacts and serve as a shelter. Numerous pit craters have been discovered on the Moon and Mars and are potential entrances to caves; the principal topographic features of pit craters are their visible internal floors and pits with vertical walls. We have devised two topographical models for investigating the relationship between the topographical characteristics and the inner void of pit craters. One of our models is a concave floor void model and the other is a convex floor tube model. For each model, optical photographs have been obtained under conditions similar to those in which optical photographs have been acquired for craters on the Moon and Mars. Brightness profiles were analyzed for determining the profile patterns of the void pit craters. The profile patterns were compared to the brightness profiles of Martian pit craters, because no good-quality images of lunar pit craters were available. In future studies, the model profile patterns will be compared to those of lunar pit craters, and the proposed method will likely become useful for finding lunar caves and consequently for planning lunar bases for manned lunar expeditions.

Pluto: Pits and mantles on uplands north and east of Sputnik Planitia

NASA Astrophysics Data System (ADS)

Howard, Alan D.; Moore, Jeffrey M.; White, Oliver L.; Umurhan, Orkan M.; Schenk, Paul M.; Grundy, William M.; Schmitt, Bernard; Philippe, Sylvain; McKinnon, William B.; Spencer, John R.; Beyer, Ross A.; Stern, S. Alan; Ennico, Kimberly; Olkin, Cathy B.; Weaver, Harold A.; Young, Leslie A.; New Horizons Science Team

2017-09-01

The highlands region north and east of Sputnik Planitia can be subdivided into seven terrain types based on their physiographic expression. The northern rough uplands are characterized by jagged uplands and broad troughs, and it may contain a deeply-eroded ancient mantle. Dissected terrain has been interpreted to have been eroded by paleo-glaciation. The smooth uplands and pits terrain contains broad, rolling uplands surrounding complexes of pits, some of which contain smooth floors. The uplands are mantled by smooth-surfaced deposits possibly derived from adjacent pits through low-power explosive cryovolcanism or through slow vapor condensation. The eroded smooth uplands appear to have originally been smooth uplands and pits terrain modified by small-scale sublimation pitting. The bright pitted uplands features intricate texturing by reticulate ridges that may have originated by sublimation erosion, volatile condensation, or both. The bladed terrain is characterized by parallel ridges oriented north-south and is discussed in a separate paper. The dark uplands are mantled with reddish deposits that may be atmospherically deposited tholins. Their presence has affected long-term landform evolution. Widespread pit complexes occur on most of the terrain units. Most appear to be associated with tectonic lineations. Some pits are floored by broad expanses of ices, whereas most feature deep, conical depressions. A few pit complexes are enclosed by elevated rims of uncertain origin.

Phosphate Uptake-Independent Signaling Functions of the Type III Sodium-Dependent Phosphate Transporter, PiT-1, in Vascular Smooth Muscle Cells

PubMed Central

Chavkin, Nicholas W.; Jun Chia, Jia; Crouthamel, Matthew H.; Giachelli, Cecilia M.

2015-01-01

Vascular calcification (VC) is prevalent in chronic kidney disease and elevated serum inorganic phosphate (Pi) is a recognized risk factor. The type III sodium-dependent phosphate transporter, PiT-1, is required for elevated Pi-induced osteochondrogenic differentiation and matrix mineralization in vascular smooth muscle cells (VSMCs). However, the molecular mechanism(s) by which PiT-1 promotes these processes is unclear. In the present study, we confirmed that the Pi concentration required to induce osteochondrogenic differentiation and matrix mineralization of mouse VSMCs was well above that required for maximal Pi uptake, suggesting a signaling function of PiT-1 that was independent of Pi transport. Elevated Pi-induced signaling via ERK1/2 phosphorylation was abrogated in PiT-1 deficient VSMCs, but could be rescued by wild-type (WT) and a Pi transport-deficient PiT-1 mutant. Furthermore, both WT and transport-deficient PiT-1 mutants promoted osteochondrogenic differentiation as measured by decreased SM22α and increased osteopontin mRNA expression. Finally, compared to vector alone, expression of transport-deficient PiT-1 mutants promoted VSMC matrix mineralization, but not to the extent observed with PiT-1 WT. These data suggest that both Pi uptake-dependent and -independent functions of PiT-1 are important for VSMC processes mediating vascular calcification. PMID:25684711

Lunar Pit Craters Presumed to be the Entrances of Lava Caves by Analogy to the Earth Lava Tube Pits

NASA Astrophysics Data System (ADS)

Hong, Ik-Seon; Yi, Yu; Kim, Eojin

2014-06-01

Lava caves could be useful as outposts for the human exploration of the Moon. Lava caves or lava tubes are formed when the external surface of the lava flows cools more quickly to make a hardened crust over subsurface lava flows. The lava flow eventually ceases and drains out of the tube, leaving an empty space. The frail part of the ceiling of lava tube could collapse to expose the entrance to the lava tubes which is called a pit crater. Several pit craters with the diameter of around 100 meters have been found by analyzing the data of SELENE and LRO lunar missions. It is hard to use these pit craters for outposts since these are too large in scale. In this study, small scale pit craters which are fit for outposts have been investigated using the NAC image data of LROC. Several topographic patterns which are believed to be lunar caves have been found and the similar pit craters of the Earth were compared and analyzed to identify caves. For this analysis, the image data of satellites and aerial photographs are collected and classified to construct a database. Several pit craters analogous to lunar pit craters were derived and a morphological pit crater model was generated using the 3D printer based on this database.

A PIT-1 Homeodomain Mutant Blocks the Intranuclear Recruitment Of the CCAAT/Enhancer Binding Protein α Required for Prolactin Gene Transcription

PubMed Central

ENWRIGHT, JOHN F.; KAWECKI-CROOK, MARGARET A.; VOSS, TY C.; SCHAUFELE, FRED; DAY, RICHARD N.

2010-01-01

The pituitary-specific homeodomain protein Pit-1 cooperates with other transcription factors, in cluding CCAAT/enhancer binding protein α (C/ EBPα), in the regulation of pituitary lactotrope gene transcription. Here, we correlate cooperative activation of prolactin (PRL) gene transcription by Pit-1 and C/EBPα with changes in the subnuclear localization of these factors in living pituitary cells. Transiently expressed C/EBPα induced PRL gene transcription in pituitary GHFT1–5 cells, whereas the coexpression of Pit-1 and C/EBPα in HeLa cells demonstrated their cooperativity at the PRL promoter. Individually expressed Pit-1 or C/EBPα, fused to color variants of fluorescent proteins, occupied different subnuclear compartments in living pituitary cells. When coexpressed, Pit-1 recruited C/EBPα from regions of transcriptionally quiescent centromeric heterochromatin to the nuclear regions occupied by Pit-1. The homeodomain region of Pit-1 was necessary for the recruitment of C/EBPα. A point mutation in the Pit-1 homeodomain associated with the syndrome of combined pituitary hormone deficiency in humans also failed to recruit C/EBPα. This Pit-1 mutant functioned as a dominant inhibitor of PRL gene transcription and, instead of recruiting C/EBPα, was itself recruited by C/EBPα to centromeric heterochromatin. Together our results suggest that the intranuclear positioning of these factors determines whether they activate or silence PRL promoter activity. PMID:12554749

Modelling effects of tree population dynamics, tree throw and pit-mound formation/diffusion on microtopography over time in different forest settings

NASA Astrophysics Data System (ADS)

Martin, Y. E.; Johnson, E. A.; Gallaway, J.; Chaikina, O.

2011-12-01

Herein we conduct a followup investigation to an earlier research project in which we developed a numerical model of tree population dynamics, tree throw, and sediment transport associated with the formation of pit-mound features for Hawk Creek watershed, Canadian Rockies (Gallaway et al., 2009). We extend this earlier work by exploring the most appropriate transport relations to simulate the diffusion over time of newly-formed pit-pound features due to tree throw. We combine our earlier model with a landscape development model that can incorporate these diffusive transport relations. Using these combined models, changes in hillslope microtopography over time associated with the formation of pit-mound features and their decay will be investigated. The following ideas have motivated this particular study: (i) Rates of pit-mound degradation remain a source of almost complete speculation, as there is almost no long-term information on process rates. Therefore, we will attempt to tackle the issue of pit-mound degradation in a methodical way that can guide future field studies; (ii) The degree of visible pit-mound topography at any point in time on the landscape is a joint function of the rate of formation of new pit-mound features due to tree death/topple and their magnitude vs. the rate of decay of pit-mound features. An example of one interesting observation that arises is the following: it appears that pit-mound topography is often more pronounced in some eastern North American forests vs. field sites along the eastern slopes of the Canadian Rockies. Why is this the case? Our investigation begins by considering whether pit-mound decay might occur by linear or nonlinear diffusion. What differences might arise depending on which diffusive approach is adopted? What is the magnitude of transport rates associated with these possible forms of transport relations? We explore linear and nonlinear diffusion at varying rates and for different sizes of pit-mound pairs using a numerical modelling approach. Model results suggest that longevity of pit-mound features is dependent on: (i) magnitude/dimensions of initial pit-mound features for forests in different regions; (ii) defining appropriate pit-mound diffusion rates for these different forests (unfortunately, almost no appropriate field observations exist for calibration of these transport relations). In the next stage of this research, we will combine our earlier model of forest disturbance/tree population dynamics, tree throw and pit-mound formation with the numerical model LandMod (Martin, 1998, 2000, 2007); the latter will be used to simulate pit-mound diffusion over time. In this way, we can observe changes in hillslope microtopographic signatures over time that are found in different forest settings.

Selenium bioaccumulation in stocked fish as an indicator of fishery potential in pit lakes on reclaimed coal mines in Alberta, Canada.

PubMed

Miller, L L; Rasmussen, J B; Palace, V P; Sterling, G; Hontela, A

2013-07-01

Pit lakes are a common reclamation strategy for open pit mines; however, there is a concern about their water quality and suitability as fish habitat because they are often contaminated by metals or metalloids. This study assessed the exposure of fish and invertebrates to selenium (Se) and other metals and metalloids in pit lakes formed by open pit coal mining in Tertiary (thermal coal) and in Cretaceous (metallurgical coal) bedrock. Juvenile hatchery rainbow trout, Oncorhynchus mykiss, and brook trout, Salvelinus fontinalis, were stocked into two thermal coal pit lakes (water Se < 2 μg/L, low water Se) and two metallurgical coal pit lakes (water Se > 15 μg/L, high water Se). Se accumulation in stocked fish and concentrations in invertebrates were characterized over a period of 2 years. In the metallurgical pits, invertebrates had higher Se concentrations and fish accumulated Se to higher levels (exceeding USEPA tissue Se guidelines) than biota in the thermal pits. Rainbow and brook trout accumulated similar concentrations of Se in their muscle and exhibited a similar relationship between whole-body and muscle Se concentrations. These results may be used by resource managers to assess compliance with whole-body tissue Se guidelines and to determine if pit lakes in coal mining areas pose a significant Se risk to wildlife or human health. The high Se exposure in metallurgical coal pits indicates that under the current mining and reclamation strategy, these lakes are not suitable for management as recreational "put and take" fisheries.

Near Infrared Photoimmunotherapy in the Treatment of Pleural Disseminated NSCLC: Preclinical Experience

PubMed Central

Sato, Kazuhide; Nagaya, Tadanobu; Choyke, Peter L.; Kobayashi, Hisataka

2015-01-01

Pleural metastases are common in patients with advanced thoracic cancers and are a cause of considerable morbidity and mortality yet is difficult to treat. Near Infrared Photoimmunotherapy (NIR-PIT) is a cancer treatment that combines the specificity of intravenously injected antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to NIR-light. Herein, we evaluate the efficacy of NIR-PIT in a mouse model of pleural disseminated non-small cell lung carcinoma (NSCLC). In vitro and in vivo experiments were conducted with a HER2, luciferase and GFP expressing NSCLC cell line (Calu3-luc-GFP). An antibody-photosensitizer conjugate (APC) consisting of trastuzumab and a phthalocyanine dye, IRDye-700DX, was synthesized. In vitro NIR-PIT cytotoxicity was assessed with dead staining, luciferase activity, and GFP fluorescence intensity. In vivo NIR-PIT was performed in mice with tumors implanted intrathoracic cavity or in the flank, and assessed by tumor volume and/or bioluminescence and fluorescence thoracoscopy. In vitro NIR-PIT-induced cytotoxicity was light dose dependent. In vivo NIR-PIT led significant reductions in both tumor volume (p = 0.002 vs. APC) and luciferase activity (p = 0.0004 vs. APC) in a flank model, and prolonged survival (p < 0.0001). Bioluminescence indicated that NIR-PIT lead to significant reduction in pleural dissemination (1 day after PIT; p = 0.0180). Fluorescence thoracoscopy confirmed the NIR-PIT effect on disseminated pleural disease. In conclusion, NIR-PIT has the ability to effectively treat pleural metastases caused by NSCLC in mice. Thus, NIR-PIT is a promising therapy for pleural disseminated tumors. PMID:25897335

Fish assemblages in borrow-pit lakes of the Lower Mississippi River

USGS Publications Warehouse

Miranda, Leandro E.; Killgore, K. J.; Hoover, J.J.

2013-01-01

Borrow-pit lakes encompass about a third of the lentic water habitats (by area) in the active floodplain of the Lower Mississippi River, yet little is known about their fish assemblages. We investigated whether fish assemblages supported by borrow-pit lakes resembled those in oxbow lakes to help place the ecological relevance of borrow-pit lakes in context with that of natural floodplain lakes. In all, we collected 75 fish species, including 65 species in eight borrow-pit lakes, 52 species in four riverside oxbow lakes, and 44 species in eight landside oxbow lakes. Significant differences in several species richness metrics were evident between borrow-pit lakes and landside oxbow lakes but not between borrow-pit lakes and riverside oxbow lakes. All three lake types differed in fish assemblage composition. Borrow-pit lakes and riverside oxbow lakes tended to include a greater representation of fish species that require access to diverse environments, including lentic, lotic, and palustrine habitats; fish assemblages in landside oxbow lakes included a higher representation of lacustrine species. None of the fish species collected in borrow-pit lakes was federally listed as threatened or endangered, but several were listed as species of special concern by state governments in the region, suggesting that borrow-pit lakes provide habitat for sensitive riverine and wetland fish species. Differences in fish assemblages among borrow-pit lakes were linked to engineered morphologic features, suggesting that diversity in engineering can contribute to diversity in fish assemblages; however, more research is needed to match engineering designs with fish assemblage structures that best meet conservation needs.

Using passive integrated transponder (PIT) systems for terrestrial detection of blue-spotted salamanders (Ambystoma laterale) in situ

USGS Publications Warehouse

Ryan, Kevin J.; Zydlewski, Joseph D.; Calhoun, Aram J.K.

2014-01-01

Pure-diploid Blue-spotted Salamanders (Ambystoma laterale) are the smallest members of the family Ambystomatidae which makes tracking with radio-transmitters difficult because of small battery capacity. Passive integrated transponder (PIT) tags provide another tracking approach for small fossorial animals such as salamanders. We evaluated the use of portable PIT tag readers (PIT packs) to detect PIT tag-implanted pure-diploid Blue-spotted Salamanders in situ. We also examined the detection probability of salamanders with PIT tags held in enclosures in wetland and terrestrial habitats, as well as the underground detection range of PIT packs by scanning for buried tags not implanted into salamanders. Of the 532 PIT tagged salamanders, we detected 6.84% at least once during scanning surveys. We scanned systematically within a 13.37 ha area surrounding a salamander breeding pool on 34 occasions (~119 hours of survey time) and detected PIT tags 74 times. We detected 55% of PITs in tagged salamanders and 45%were expelled tags. We were able to reliably detect buried PIT tags from 1–22cm below the ground surface. Because nearly half the locations represented expelled tags, our data suggest this technique is inappropriate for future studies of pure-diploid Blue-spotted Salamanders, although it may be suitable for polyploid Blue-spotted Salamanders and other ambystomatid species, which are larger in size and may exhibit higher tag retention rates. It may also be prudent to conduct long-term tag retention studies in captivity before tagging and releasing salamanders for in situ study, and to double-mark individuals.

Imidazole as a pH Probe: An NMR Experiment for the General Chemistry Laboratory

ERIC Educational Resources Information Center

Hagan, William J., Jr.; Edie, Dennis L.; Cooley, Linda B.

2007-01-01

The analysis describes an NMR experiment for the general chemistry laboratory, which employs an unknown imidazole solution to measure the pH values. The described mechanism can also be used for measuring the acidity within the isolated cells.

Visualizing Chemistry: Investigations for Teachers.

ERIC Educational Resources Information Center

Ealy, Julie B.; Ealy, James L., Jr.

This book contains 101 investigations for chemistry classrooms. Topics include: (1) Physical Properties; (2) Reactions of Some Elements; (3) Reactions Involving Gases; (4) Energy Changes; (5) Solutions and Solubility; (6) Transition Metals and Complex Ions; (7) Kinetics and Equilibrium; (8) Acids and Bases; (9) Oxidation-Reduction; (10)…

Plastic Bags to Batteries: A Green Chemistry Solution

ScienceCinema

Pol, Vilas

2018-04-16

Plastic bags are the scourge of roadsides, parking lots and landfills. But chemistry comes to the rescue! At Argonne National Laboratory, Vilas Pol has found a way to not only recycle plastic bags--but make them into valuable batteries for cell phones and laptops.

Plastic Bags to Batteries: A Green Chemistry Solution

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

Pol, Vilas

2010-01-01

Plastic bags are the scourge of roadsides, parking lots and landfills. But chemistry comes to the rescue! At Argonne National Laboratory, Vilas Pol has found a way to not only recycle plastic bags--but make them into valuable batteries for cell phones and laptops.

1. VIEW OF THE WEST ELEVATION, LOOKING EAST, OF BUILDING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. VIEW OF THE WEST ELEVATION, LOOKING EAST, OF BUILDING 886 WHILE UNDER CONSTRUCTION IN 1964. ON THE RIGHT OF THE PHOTOGRAPH IS THE CRITICALITY ASSEMBLY ROOM, ROOM 101, CONSTRUCTED OF DOUBLE REINFORCED CONCRETE WALLS INTEGRALLY CAST TO THE TWO FEET THICK CEILING. IN THE FOREGROUND, IS THE 19' FEET DEEP PIT AREA INTENDED TO HOUSE WASTE SOLUTION STORAGE TANKS. ONLY ONE TANK WAS USED, TO STORE WASTEWATER. - Rocky Flats Plant, Critical Mass Laboratory, Intersection of Central Avenue & 86 Drive, Golden, Jefferson County, CO

Theoretical study of the dissolution kinetics of galena and cerussite in an abandoned mining area (Zaida mine, Morocco)

NASA Astrophysics Data System (ADS)

El Alaoui, Lamiae; Dekayir, Abdelilah

2018-05-01

In the abandoned mine in Zaida, the pit lakes filled with water constitute significant water reserves. In these lakes, the waters are permanently in contact with ore deposit (cerussite and galena). The modelling of the interaction of waters with this mineralization shows that cerussite dissolves more rapidly than galena. This dissolution is controlled by the pH and dissolved oxygen concentration in solution. The lead concentrations recorded in these lakes come largely from the dissolution of cerussite.

Possibilities of surface waters monitoring at mining areas using UAV

NASA Astrophysics Data System (ADS)

Lisiecka, Ewa; Motyka, Barbara; Motyka, Zbigniew; Pierzchała, Łukasz; Szade, Adam

2018-04-01

The selected, remote measurement methods are discussed, useful for determining surface water properties using mobile unmanned aerial platforms (UAV). The possibilities of using this type of solutions in the scope of measuring spatial, physicochemical and biological parameters of both natural and anthropogenic water reservoirs, including flood polders, water-filled pits, settling tanks and mining sinks were analyzed. Methods of remote identification of the process of overgrowing this type of ecosystems with water and coastal plant formations have also been proposed.

Effect of non-equilibrium flow chemistry and surface catalysis on surface heating to AFE

NASA Technical Reports Server (NTRS)

Stewart, David A.; Henline, William D.; Chen, Yih-Kanq

1991-01-01

The effect of nonequilibrium flow chemistry on the surface temperature distribution over the forebody heat shield on the Aeroassisted Flight Experiment (AFE) vehicle was investigated using a reacting boundary-layer code. Computations were performed by using boundary-layer-edge properties determined from global iterations between the boundary-layer code and flow field solutions from a viscous shock layer (VSL) and a full Navier-Stokes solution. Surface temperature distribution over the AFE heat shield was calculated for two flight conditions during a nominal AFE trajectory. This study indicates that the surface temperature distribution is sensitive to the nonequilibrium chemistry in the shock layer. Heating distributions over the AFE forebody calculated using nonequilibrium edge properties were similar to values calculated using the VSL program.

Effect of PWHT on Microstructure, Mechanical and Corrosion Behaviour of Gas Tungsten Arc Welds of IN718 Superalloys

NASA Astrophysics Data System (ADS)

Dilkush; Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

The present work aims to improve corrosion resistance and mechanical behavior of the welds with suitable post weld heat treatment i.e. direct aging and solutionizing treatments (980STA, 1080STA). Gas tungsten arc welding (GTAW) has been performed on Inconel 718 (IN718) nickel based super alloy plates with 3mm thickness. The structural –property relationship of the post weld heat treated samples is judged by correlating the microstructural changes with observed mechanical behavior and pitting corrosion resistance of the welds As-recevied, direct aging (DA), 980STA,1080STA were studied. Welds were characterized for microstructure changes with scanning electron microscopy (SEM) and optical microscopy (OM).Vickers micro- hardness tester was used to measure the hardness of the weldments. Potential-dynamic polarization testing was carried out to study the pitting corrosion resistance in 3.5%NaCl (Sodium chloride) solution at 30°C.Results of the present study established that post weld heat treatments resulted in promoting the element segregation diffusion and resolve them from brittle laves particles in the matrix. Increased precipitation of strengthening phases lead to a significant increase in fusion zone hardness of 1080STA post weld heat treated condition compared to as welded, direct aged, 980STA conditions. Due to significant changes in the microstructural behavior of 1080STA condition resulted in superior pitting corrosion resistance than 980STA, direct aged and as- recevied conditions of IN718 GTA welds

Evidence of ancient microbial activity on Mars

NASA Astrophysics Data System (ADS)

Wallis, Jamie; Wickramasinghe, N. C.; Wallis, Daryl H.; Miyake, Nori; Wallis, M. K.; Hoover, Richard B.

2015-09-01

We report for the first time in situ observations of a relatively rare secondary iron arsenate-sulphate mineral named bukovskýite - Fe3+ 2(As5+O4)(S6+O4)(OH)•7(H2O) - found in a shock melt vein of the Tissint Martian meteorite. It is hypothesised that the mineral formed when high concentrations of aqueous H+, Fe(III), SO4 and AsO4 were maintained for long periods of time in microenvironments created within wet subsurface Martian clays. The aqueous H+, Fe(III), SO4 and AsO4 species arose from the microbial oxidation of FeS2 with concurrent release of sequestrated As. The availability of aqueous AsO4 would also be complemented by dissolution by-products of the microbial reduction of Feoxides influenced by dissolved organic matter that alters the redox state and the complexation of As, thus shifting As partitioning in favour of the solute phase. This hypothesis is substantially supported by SEM analysis of a 15μm spherical structure comprising of a carbonaceous outer coating with a inner core of FeS2 (pyrite) that showed the pyrite surface with spherical pits, and chains of pits, with morphologies distinct from abiotic alteration features. The pits and channels have a clustered, geometric distribution, typical of microbial activity, and are closely comparable to biologically mediated microstructures created by Fe- and S-oxidising microbes in the laboratory. These microstructures are interpreted as trace fossils resulting from the attachment of bacteria to the pyrite surfaces.

Soil-pit Method for Distribution and Leaching Loss of Nitrogen in Winter Wheat’s Soil, Weishan Irrigation District

NASA Astrophysics Data System (ADS)

Zhao, Erni; Xu, Lirong; Wang, Rongzhen

2018-01-01

Unreasonable application of irrigation and fertilizer will cause the waste of water and nitrogen and environmental pollution. In this paper, a series of soil-pit experiments were carried out to study the distribution and leaching loss of nitrogen in winter wheat’s soil. The results showed that NO3 - concentration at 20-80cm depth mainly responded to fertilizer application at the beginning of field experiment, but the amount of irrigation became the dominant factor with the growth of winter wheat. It is noteworthy that the distribution of NO3 - was mainly affected by the amount of fertilizer applied at the depth of 120-160cm in the whole period of growth of winter wheat. The accumulation position of NH4 + was deepened as the amount of irrigation increased, however, the maximum aggregation depth of ammonium nitrogen was no more than 80cm owing to its poor migration. It can be concluded that the influence of irrigation amount on the concentration of NH4 + in soil solution was more obvious than that of fertilizer. Compared with fertilizer, the amount of irrigation played a leading role in the utilization ratio of nitrogen and the yield of winter wheat. In summary, the best water and fertilizer treatment occurred in No.3 soil-pit, which meant that the middle amount of water and fertilizer could get higher wheat yield and less nitrogen leaching losses in the study area.

Passivation Dynamics in the Anisotropic Deposition and Stripping of Bulk Magnesium Electrodes During Electrochemical Cycling.

PubMed

Wetzel, David J; Malone, Marvin A; Haasch, Richard T; Meng, Yifei; Vieker, Henning; Hahn, Nathan T; Gölzhäuser, Armin; Zuo, Jian-Min; Zavadil, Kevin R; Gewirth, Andrew A; Nuzzo, Ralph G

2015-08-26

Although rechargeable magnesium (Mg) batteries show promise for use as a next generation technology for high-density energy storage, little is known about the Mg anode solid electrolyte interphase and its implications for the performance and durability of a Mg-based battery. We explore in this report passivation effects engendered during the electrochemical cycling of a bulk Mg anode, characterizing their influences during metal deposition and dissolution in a simple, nonaqueous, Grignard electrolyte solution (ethylmagnesium bromide, EtMgBr, in tetrahydrofuran). Scanning electron microscopy images of Mg foil working electrodes after electrochemical polarization to dissolution potentials show the formation of corrosion pits. The pit densities so evidenced are markedly potential-dependent. When the Mg working electrode is cycled both potentiostatically and galvanostatically in EtMgBr these pits, formed due to passive layer breakdown, act as the foci for subsequent electrochemical activity. Detailed microscopy, diffraction, and spectroscopic data show that further passivation and corrosion results in the anisotropic stripping of the Mg {0001} plane, leaving thin oxide-comprising passivated side wall structures that demark the {0001} fiber texture of the etched Mg grains. Upon long-term cycling, oxide side walls formed due to the pronounced crystallographic anisotropy of the anodic stripping processes, leading to complex overlay anisotropic, columnar structures, exceeding 50 μm in height. The passive responses mediating the growth of these structures appear to be an intrinsic feature of the electrochemical growth and dissolution of Mg using this electrolyte.

Analysis of Proximity-1 Space Link Interleaved Time Synchronization (PITS) Protocol

NASA Technical Reports Server (NTRS)

Woo, Simon S.

2011-01-01

To synchronize clocks between spacecraft in proximity, the Proximity-1 Space Link Interleaved Time Synchronization (PITS) Protocol has been proposed. PITS is based on the NTP Interleaved On-Wire Protocol and is capable of being adapted and integrated into CCSDS Proximity-1 Space Link Protocol with minimal modifications. In this work, we will discuss the correctness and liveness of PITS. Further, we analyze and evaluate the performance of time synchronization latency with various channel error rates in different PITS operational modes.

Nucleation Of Ge 3D-islands On Pit-patterned Si Substrates

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

Novikov, P. L.; Smagina, J. V.; Vlasov, D. Yu.

2011-12-23

Joint experimental and theoretical study of Ge nanoislands growth on pit-patterned Si substrate is carried out. Si substrates that have been templated by means of electron beam lithography and reactive ion etching have been used to grow Ge by molecular-beam epitaxy. Atomic-force-microscopy studies show that at Si(100) substrate temperature 550 deg. C, Ge nanoislands are formed at the pits' edges, rather than between the pits. The effect is interpreted in terms of energy barrier, that is formed near the edge of a pit and prevents Ge transport inside the pit. By molecular dynamics calculations the value of the energy barriermore » 0.9 eV was obtained.« less

Perspective—Localized Corrosion: Passive Film Breakdown vs Pit Growth Stability

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

Frankel, G. S.; Li, Tianshu; Scully, J. R.

2017-02-24

A debate about the critical step in localized corrosion has raged for decades. Some researchers focus on the composition and structure of the passive film associated with the initial breakdown of the film, whereas others consider that the susceptibility to pitting is controlled by the pit growth kinetics and the stabilization of pit growth. The basis for a unified theory of pitting is presented here in which pit stability considerations are controlling under aggressive conditions (harsh electrolytes and extreme environments and/or susceptible microstructures) and the passive film properties and protectiveness are the critical factors in less extreme environments and/or formore » less susceptible alloys.« less

First-Principles pH Theory

NASA Astrophysics Data System (ADS)

Kim, Yong-Hyun; Zhang, S. B.

2006-03-01

Despite being one of the most important macroscopic measures and a long history even before the quantum mechanics, the concept of pH has rarely been mentioned in microscopic theories, nor being incorporated computationally into first-principles theory of aqueous solutions. Here, we formulate a theory for the pH dependence of solution formation energy by introducing the proton chemical potential as the microscopic counterpart of pH in atomistic solution models. Within the theory, the general acid-base chemistry can be cast in a simple pictorial representation. We adopt density-functional molecular dynamics to demonstrate the usefulness of the method by studying a number of solution systems including water, small solute molecules such as NH3 and HCOOH, and more complex amino acids with several functional groups. For pure water, we calculated the auto- ionization constant to be 13.2 with a 95 % accuracy. For other solutes, the calculated dissociation constants, i.e., the so- called pKa, are also in reasonable agreement with experiments. Our first-principles pH theory can be readily applied to broad solution chemistry problems such as redox reactions.

Aqueous Plasma Pharmacy: Preparation Methods, Chemistry, and Therapeutic Applications

PubMed Central

Joslin, Jessica M.; McCall, James R.; Bzdek, Justin P.; Johnson, Derek C.; Hybertson, Brooks M.

2017-01-01

Plasma pharmacy is a subset of the broader field of plasma medicine. Although not strictly defined, the term aqueous plasma pharmacy (APP) is used to refer to the generation and distribution of reactive plasma-generated species in an aqueous solution followed by subsequent administration for therapeutic benefits. APP attempts to harness the therapeutic effects of plasma-generated oxidant species within aqueous solution in various applications, such as disinfectant solutions, cell proliferation related to wound healing, and cancer treatment. The subsequent use of plasma-generated solutions in the APP approach facilitates the delivery of reactive plasma species to internal locations within the body. Although significant efforts in the field of plasma medicine have concentrated on employing direct plasma plume exposure to cells or tissues, here we focus specifically on plasma discharge in aqueous solution to render the solution biologically active for subsequent application. Methods of plasma discharge in solution are reviewed, along with aqueous plasma chemistry and the applications for APP. The future of the field also is discussed regarding necessary research efforts that will enable commercialization for clinical deployment. PMID:28428835

Corrosion and corrosion fatigue of airframe aluminum alloys

NASA Technical Reports Server (NTRS)

Chen, G. S.; Gao, M.; Harlow, D. G.; Wei, R. P.

1994-01-01

Localized corrosion and corrosion fatigue crack nucleation and growth are recognized as degradation mechanisms that effect the durability and integrity of commercial transport aircraft. Mechanically based understanding is needed to aid the development of effective methodologies for assessing durability and integrity of airframe components. As a part of the methodology development, experiments on pitting corrosion, and on corrosion fatigue crack nucleation and early growth from these pits were conducted. Pitting was found to be associated with constituent particles in the alloys and pit growth often involved coalescence of individual particle-nucleated pits, both laterally and in depth. Fatigue cracks typically nucleated from one of the larger pits that formed by a cluster of particles. The size of pit at which fatigue crack nucleates is a function of stress level and fatigue loading frequency. The experimental results are summarized, and their implications on service performance and life prediction are discussed.

Light-extraction efficiency and forward voltage in GaN-based light-emitting diodes with different patterns of V-shaped pits

NASA Astrophysics Data System (ADS)

Wang, Min-Shuai; Huang, Xiao-Jing

2013-08-01

We present a new method of making a textured V-pit surface for improving the light extraction efficiency in GaN-based light-emitting diodes and compare it with the usual low-temperature method for p-GaN V-pits. Three types of GaN-based light-emitting diodes (LEDs) with surface V-pits in different densities and regions were grown by metal—organic chemical vapor deposition. We achieved the highest output power and lowest forward voltage values with the p-InGaN V-pit LED. The V-pits enhanced the light output power values by 1.45 times the values of the conventional LED owing to an enhancement of the light scattering probability and an effective reduction of Mg-acceptor activation energy. Moreover, this new technique effectively solved the higher forward voltage problem of the usual V-pit LED.

Improving Pit Vehicle Ecology Safety

NASA Astrophysics Data System (ADS)

Koptev, V. Yu; Kopteva, A. V.

2018-05-01

The article discloses the ways to improve the ecological safety of a pit transport: reducing harmful substance concentrations in exhaust gases, implementation of the ecological certificate of the dumping truck, taking into account the operation of the dumping truck actual work, choosing the best model and comparing ecological characteristics of pit lifters at deep pits.

The dependence receptor Ret induces apoptosis in somatotrophs through a Pit-1/p53 pathway, preventing tumor growth

PubMed Central

Cañibano, Carmen; Rodriguez, Noela L; Saez, Carmen; Tovar, Sulay; Garcia-Lavandeira, Montse; Borrello, Maria Grazia; Vidal, Anxo; Costantini, Frank; Japon, Miguel; Dieguez, Carlos; Alvarez, Clara V

2007-01-01

Somatotrophs are the only pituitary cells that express Ret, GFRα1 and GDNF. This study investigated the effects of Ret in a somatotroph cell line, in primary pituitary cultures and in Ret KO mice. Ret regulates somatotroph numbers by inducing Pit-1 overexpression, leading to increased p53 expression and apoptosis, both of which can be prevented with Ret or Pit-1 siRNA. The Pit-1 overexpression is mediated by sustained activation of PKCδ, JNK, c/EBPα and CREB induced by a complex of Ret, caspase 3 and PKCδ. In the presence of GDNF, Akt is activated, and the Pit-1 overexpression and resulting apoptosis are blocked. The adenopituitary of Ret KO mice is larger than normal, showing Pit-1 and somatotroph hyperplasia. In normal animals, activation of the Ret/Pit-1/p53 pathway by retroviral introduction of Ret blocked tumor growth in vivo. Thus, somatotrophs have an intrinsic mechanism for controlling Pit-1/GH production through an apoptotic/survival pathway. Ret might be of value for treatment of pituitary adenomas. PMID:17380130

The dependence receptor Ret induces apoptosis in somatotrophs through a Pit-1/p53 pathway, preventing tumor growth.

PubMed

Cañibano, Carmen; Rodriguez, Noela L; Saez, Carmen; Tovar, Sulay; Garcia-Lavandeira, Montse; Borrello, Maria Grazia; Vidal, Anxo; Costantini, Frank; Japon, Miguel; Dieguez, Carlos; Alvarez, Clara V

2007-04-18

Somatotrophs are the only pituitary cells that express Ret, GFRalpha1 and GDNF. This study investigated the effects of Ret in a somatotroph cell line, in primary pituitary cultures and in Ret KO mice. Ret regulates somatotroph numbers by inducing Pit-1 overexpression, leading to increased p53 expression and apoptosis, both of which can be prevented with Ret or Pit-1 siRNA. The Pit-1 overexpression is mediated by sustained activation of PKCdelta, JNK, c/EBPalpha and CREB induced by a complex of Ret, caspase 3 and PKCdelta. In the presence of GDNF, Akt is activated, and the Pit-1 overexpression and resulting apoptosis are blocked. The adenopituitary of Ret KO mice is larger than normal, showing Pit-1 and somatotroph hyperplasia. In normal animals, activation of the Ret/Pit-1/p53 pathway by retroviral introduction of Ret blocked tumor growth in vivo. Thus, somatotrophs have an intrinsic mechanism for controlling Pit-1/GH production through an apoptotic/survival pathway. Ret might be of value for treatment of pituitary adenomas.

Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

PubMed Central

Huang, Yongfang; Gang, Tieqiang; Chen, Lijie

2017-01-01

For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ) and pit depth (d) with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor Ktnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, Ktnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that Ktnor follows a linear and an exponential relationship with the dimensionless depth parameter Rd for intersecting and adjacent cases, respectively. PMID:28772758

A Practical and Convenient Diffusion Apparatus: An Undergraduate Physical Chemistry Experiment.

ERIC Educational Resources Information Center

Clifford, Ben; Ochiai, E. I.

1980-01-01

Described is a diffusion apparatus to be used in an undergraduate physical chemistry laboratory experiment to determine the diffusion coefficients of aqueous solutions of sucrose and potassium dichromate. Included is the principle of the method, apparatus design and description, and experimental procedure. (Author/DS)

EPR Studies of Spin-Spin Exchange Processes: A Physical Chemistry Experiment.

ERIC Educational Resources Information Center

Eastman, Michael P.

1982-01-01

Theoretical background, experimental procedures, and analysis of experimental results are provided for an undergraduate physical chemistry experiment on electron paramagnetic resonance (EPR) linewidths. Source of line broadening observed in a spin-spin exchange process between radicals formed in aqueous solutions of potassium peroxylamine…

SOME ASPECTS OF THE CHEMISTRY OF POLYSULFIDE PULPING,

DTIC Science & Technology

Kraft pulping with the addition of polysulfide, i.e. polysulfide pulping, is one of the few methods available which can be used to increase the yield...and change the properties of kraft pulp. The chemistry of aqueous polysulfide solutions and the concurrent reactions occurring in polysulfide pulping

Trace fossil evidence of coral-inhabiting crabs (Cryptochiridae) and its implications for growth and paleobiogeography

NASA Astrophysics Data System (ADS)

Klompmaker, Adiël A.; Portell, Roger W.; van der Meij, Sancia E. T.

2016-03-01

Members of the Cryptochiridae are small, fragile, symbiotic crabs that live in domiciles in modern corals. Despite their worldwide occurrence with over 50 species known today, their fossil record is unknown. We provide the first unambiguous evidence of cryptochirids in the fossil record through their crescentic pits, typical for certain cryptochirids, in Western Atlantic fossil corals, while the Eocene genus Montemagrechirus is excluded from the Cryptochiridae and referred to Montemagrechiridae fam. nov. Nine Pleistocene corals with crescentic pits originate from Florida (USA), and single specimens with pits come from the late Pleistocene of Cuba and the late Pliocene of Florida, all of which are measured for growth analyses. These pits represent trace fossils named Galacticus duerri igen. nov., isp. nov. A study of modern cryptochirid domicile shape (crescentic pit, circular-oval pit, or a true gall) shows that species within crab genera tend to inhabit the same pit shape. Crescentic pits in corals occur not only in the Western Atlantic today, but also in the Indo-West Pacific and in the Eastern Pacific. Thus, examination of Cenozoic fossil coral collections from these regions should yield further examples of cryptochirid pits, which would help to constrain the antiquity of this cryptic crab family.

Mechanism of water-stress induced cavitation in conifers: bordered pit structure and function support the hypothesis of seal capillary-seeding

PubMed Central

DELZON, SYLVAIN; DOUTHE, CYRIL; SALA, ANNA; COCHARD, HERVE

2010-01-01

Resistance to water-stress induced cavitation is an important indicator of drought tolerance in woody species and is known to be intimately linked to the anatomy of the xylem. However, the actual mechanical properties of the pit membrane are not well known and the exact mode of air-seeding by which cavitation occurs is still uncertain. We examined the relationship between cavitation resistance and bordered pit structure and function in 40 coniferous species. Xylem pressure inducing 50% loss of hydraulic conductance (P50, a proxy for cavitation resistance) varied widely among species, from −2.9 to −11.3 MPa. The valve effect of the pit membrane, measured as a function of margo flexibility and torus overlap, explained more variation in cavitation-resistance than simple anatomical traits such as pit membrane, pit aperture or torus size. Highly cavitation resistant species exhibited both a high flexibility of the margo and a large overlap between the torus and the pit aperture, allowing the torus to tightly seal the pit aperture. Our results support the hypothesis of seal capillary-seeding as the most likely mode of air-seeding, and suggest that the adhesion of the torus to the pit border may be the main determinant of cavitation resistance in conifers. PMID:20636490

Mechanism of water-stress induced cavitation in conifers: bordered pit structure and function support the hypothesis of seal capillary-seeding.

PubMed

Delzon, Sylvain; Douthe, Cyril; Sala, Anna; Cochard, Herve

2010-12-01

Resistance to water-stress induced cavitation is an important indicator of drought tolerance in woody species and is known to be intimately linked to the anatomy of the xylem. However, the actual mechanical properties of the pit membrane are not well known and the exact mode of air-seeding by which cavitation occurs is still uncertain. We examined the relationship between cavitation resistance and bordered pit structure and function in 40 coniferous species. Xylem pressure inducing 50% loss of hydraulic conductance (P(50), a proxy for cavitation resistance) varied widely among species, from -2.9 to -11.3 MPa. The valve effect of the pit membrane, measured as a function of margo flexibility and torus overlap, explained more variation in cavitation-resistance than simple anatomical traits such as pit membrane, pit aperture or torus size. Highly cavitation resistant species exhibited both a high flexibility of the margo and a large overlap between the torus and the pit aperture, allowing the torus to tightly seal the pit aperture. Our results support the hypothesis of seal capillary-seeding as the most likely mode of air-seeding, and suggest that the adhesion of the torus to the pit border may be the main determinant of cavitation resistance in conifers. © 2010 Blackwell Publishing Ltd.

Methodology of selecting dozers for lignite open pit mines in Serbia

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

Stojanovic, D.; Ignjatovic, D.; Kovacevic, S.

1996-12-31

Apart from the main production processes (coal and overburden mining, rail conveyors transportation and storage of excavated masses) performed by great-capacity mechanization at open pit mines, numerous and different auxiliary works, that often have crucial influence on both the work efficiency of main equipment and the maintenance of optimum technical conditions of machines and plants covering technological system of open pit, are present. Successful realization of work indispensably requires a proper and adequate selection of auxiliary machines according to their type quantity, capacity, power etc. thus highly respecting specific conditions existing at each and every open pit mine. A dozermore » is certainly the most important and representative auxiliary machine at single open pit mine. It is widely used in numerous works that, in fact, are preconditions for successful work of the main mechanization and consequently the very selection of a dozer ranges among the most important operations when selecting mechanization. This paper presents the methodology of dozers selection when lignite open pit mines are concerned. A mathematical model defining the volume of work required for dozers to perform at open pit mines and consequently the number of necessary dozers was designed. The model underwent testing in practice at big open pit mines and can be used in design of future open pits mines.« less

A Single Base Difference between Pit-1 Binding Sites at the hGH Promoter and Locus Control Region Specifies Distinct Pit-1 Conformations and Functions

PubMed Central

Shewchuk, Brian M.; Ho, Yugong; Liebhaber, Stephen A.; Cooke, Nancy E.

2006-01-01

Activation of the human growth hormone (hGH-N) gene in pituitary somatotropes is mediated by a locus control region (LCR). This LCR is composed of DNase I-hypersensitive sites (HS) located −14.5 kb to −32 kb relative to the hGH-N promoter. HSI, at −14.5 kb, is the dominant determinant of hGH-N expression and is essential for establishment of a 32-kb domain of histone acetylation that encompasses the active hGH locus. This activity is conferred by three binding sites for the POU domain transcription factor Pit-1. These Pit-1 elements are sufficient to activate hGH-N expression in the mouse pituitary. In contrast, Pit-1 sites at the hGH-N promoter are consistently unable to mediate similar activity. In the present study, we demonstrate that the functional difference between the promoter-proximal and the HSI Pit-1 binding sites can be attributed in part to a single base difference. This base affects the conformation of the Pit-1/DNA complex, and reciprocal exchange of the divergent bases between the two sets of Pit-1 elements results in a partial reversal of their transgenic activities. These data support a model in which the Pit-1 binding sites in the hGH LCR allosterically program the bound Pit-1 complex for chromatin activating functions. PMID:16914737

Reliable identification of deep sulcal pits: the effects of scan session, scanner, and surface extraction tool.

PubMed

Im, Kiho; Lee, Jong-Min; Jeon, Seun; Kim, Jong-Heon; Seo, Sang Won; Na, Duk L; Grant, P Ellen

2013-01-01

Sulcal pit analysis has been providing novel insights into brain function and development. The purpose of this study was to evaluate the reliability of sulcal pit extraction with respect to the effects of scan session, scanner, and surface extraction tool. Five subjects were scanned 4 times at 3 MRI centers and other 5 subjects were scanned 3 times at 2 MRI centers, including 1 test-retest session. Sulcal pits were extracted on the white matter surfaces reconstructed with both Montreal Neurological Institute and Freesurfer pipelines. We estimated similarity of the presence of sulcal pits having a maximum value of 1 and their spatial difference within the same subject. The tests showed high similarity of the sulcal pit presence and low spatial difference. The similarity was more than 0.90 and the spatial difference was less than 1.7 mm in most cases according to different scan sessions or scanners, and more than 0.85 and about 2.0 mm across surface extraction tools. The reliability of sulcal pit extraction was more affected by the image processing-related factors than the scan session or scanner factors. Moreover, the similarity of sulcal pit distribution appeared to be largely influenced by the presence or absence of the sulcal pits on the shallow and small folds. We suggest that our sulcal pit extraction from MRI is highly reliable and could be useful for clinical applications as an imaging biomarker.

Pavlovian-to-instrumental transfer in alcohol dependence: a pilot study.

PubMed

Garbusow, Maria; Schad, Daniel J; Sommer, Christian; Jünger, Elisabeth; Sebold, Miriam; Friedel, Eva; Wendt, Jean; Kathmann, Norbert; Schlagenhauf, Florian; Zimmermann, Ulrich S; Heinz, Andreas; Huys, Quentin J M; Rapp, Michael A

2014-01-01

Pavlovian processes are thought to play an important role in the development, maintenance and relapse of alcohol dependence, possibly by influencing and usurping ongoing thought and behavior. The influence of pavlovian stimuli on ongoing behavior is paradigmatically measured by pavlovian-to-instrumental transfer (PIT) tasks. These involve multiple stages and are complex. Whether increased PIT is involved in human alcohol dependence is uncertain. We therefore aimed to establish and validate a modified PIT paradigm that would be robust, consistent and tolerated by healthy controls as well as by patients suffering from alcohol dependence, and to explore whether alcohol dependence is associated with enhanced PIT. Thirty-two recently detoxified alcohol-dependent patients and 32 age- and gender-matched healthy controls performed a PIT task with instrumental go/no-go approach behaviors. The task involved both pavlovian stimuli associated with monetary rewards and losses, and images of drinks. Both patients and healthy controls showed a robust and temporally stable PIT effect. Strengths of PIT effects to drug-related and monetary conditioned stimuli were highly correlated. Patients more frequently showed a PIT effect, and the effect was stronger in response to aversively conditioned CSs (conditioned suppression), but there was no group difference in response to appetitive CSs. The implementation of PIT has favorably robust properties in chronic alcohol-dependent patients and in healthy controls. It shows internal consistency between monetary and drug-related cues. The findings support an association of alcohol dependence with an increased propensity towards PIT. © 2014 S. Karger AG, Basel.

Life's Biological Chemistry: A Destiny or Destination Starting from Prebiotic Chemistry?

PubMed

Krishnamurthy, Ramanarayanan

2018-06-05

Research into understanding the origins -and evolution- of life has long been dominated by the concept of taking clues from extant biology and extrapolating its molecules and pathways backwards in time. This approach has also guided the search for solutions to the problem of how contemporary biomolecules would have arisen directly from prebiotic chemistry on early earth. However, the continuing difficulties in finding universally convincing solutions in connecting prebiotic chemistry to biological chemistry should give us pause, and prompt us to rethink this concept of treating extant life's chemical processes as the sole end goal and, therefore, focusing only -and implicitly- on the respective extant chemical building blocks. Rather, it may be worthwhile "to set aside the goal" and begin with what would have been plausible prebiotic reaction mixtures (which may have no obvious or direct connection to life's chemical building blocks and processes) - and allow their chemistries and interactions, under different geochemical constraints, to guide and illuminate as to what processes and systems can emerge. Such a conceptual approach gives rise to the prospect that chemistry of life-as-we-know-it is not the only result (not a "destiny"), but one that has emerged among many potential possibilities (a "destination"). This postulate, in turn, could impact the way we think about chemical signatures and criteria used in the search for alternative and extraterrestrial "life". As a bonus, we may discover the chemistries and pathways naturally that led to the emergence of life as we know it. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption of Dissolved Metals in the Berkeley Pit using Thiol-Functionalized Self-Assembled Monolayers on Mesoporous Supports (Thiol-SAMMS)

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

Betancourt, Amaury P.; Mattigod, Shas V.; Wellman, Dawn M.

2010-03-07

The Berkeley Pit in Butte, Montana, is heavily contaminated with dissolved metals. Adsorption and extraction of these metals can be accomplished through the use of a selective adsorbent. For this research, the adsorbent used was thiol-functionalized Self-Assembled Monolayers on Mesoporous Supports (thiol-SAMMS), which was developed at Pacific Northwest National Laboratory (PNNL). Thiol-SAMMS selectively binds to numerous types of dissolved metals. The objective of this research was to evaluate the loading and kinetics of aluminum, beryllium, copper, and zinc on thiol-SAMMS. For the loading tests, a series of Berkeley Pit water to thiol-SAMMS ratios (mL:g) were tested. These ratios were 1000:1,more » 500:1, 100:1, and 50:1. Berkeley Pit water is acidic (pH {approx} 2.5). This can affect the performance of SAMMS materials. Therefore, the effect of pH was evaluated by conducting parallel series of loading tests wherein the Berkeley Pit water was neutralized before or after addition of thiol-SAMMS, and a series of kinetics tests wherein the Berkeley Pit water was neutralized before addition of thiol-SAMMS for the first test and was not neutralized for the second test. For the kinetics tests, one Berkeley Pit water to thiol-SAMMS ratio was tested, which was 2000:1. The results of the loading and kinetics tests suggest that a significant decrease in dissolved metal concentration at Berkeley Pit could be realized through neutralization of Berkeley Pit water. Thiol-SAMMS technology has a limited application under the highly acidic conditions posed by the Berkeley Pit. However, thiol-SAMMS could provide a secondary remedial technique which would complete the remedial system and remove dissolved metals from the Berkeley Pit to below drinking water standards.« less

Cloning of the canine gene encoding transcription factor Pit-1 and its exclusion as candidate gene in a canine model of pituitary dwarfism.

PubMed

Lantinga-van Leeuwen, I S; Mol, J A; Kooistra, H S; Rijnberk, A; Breen, M; Renier, C; van Oost, B A

2000-01-01

Combined pituitary hormone deficiency (CPHD) is an autosomal recessive inherited disease of German shepherd dogs characterized primarily by dwarfism. In mice and humans a similar genetic disorder has been described that results from an alteration in the gene encoding the transcription factor Pit-1. In this study we characterized the canine Pit-1 gene, determined the chromosomal localization of the Pit-1 gene, and screened dwarf German shepherd dogs for the presence of mutations in this gene. The full-length canine Pit-1 cDNA contained an open reading frame encoding 291 amino acids, 92 bp of 5'-untranslated region, and 1959 bp of 3'-untranslated region. The deduced amino acid sequence was highly homologous with Pit-1 of other mammalian species. Using a Pit-1 BAC clone as probe, the Pit-1 gene was mapped by FISH to canine Chromosome (Chr) 31. In dwarf German shepherd dogs a C to A transversion was detected, causing a Phe (TTC) to Leu (TTA) substitution at codon 81. This alteration was present neither in other canine breeds analyzed nor in other mammalian species. However, healthy German shepherd dogs were also homozygous for the mutant allele, indicating that it is not the primary disease-causing mutation. In addition, linkage analysis of polymorphic DNA markers flanking the Pit-1 gene, 41K19 and 52L05, revealed no co-segregation between the Pit-1 locus and the CPHD phenotype. These findings suggest that a gene other than Pit-1 is responsible for the pituitary anomaly in dwarf German shepherd dogs.

Expression of ayu (Plecoglossus altivelis) Pit-1 in Escherichia coli: its purification and immunohistochemical detection using monoclonal antibody.

PubMed

Chiu, Chi-Chien; John, Joseph Abraham Christopher; Hseu, Tzong-Hsiung; Chang, Chi-Yao

2002-03-01

The pituitary-specific transcription factor Pit-1 belongs to the family of POU-domain proteins and is known to play an important role in the differentiation of pituitary cells. Here we report the complete nucleotide sequence of cDNA encoding Pit-1 from the brackish water fish, ayu (Plecoglossus altivelis). Nucleotide sequence analysis of 1910 bp of ayu Pit-1 cDNA revealed an open reading frame of 1074 bp that encodes a protein of 358 amino acids containing a POU-specific domain, POU homeodomain, and an STA (Ser/Thr-rich activation) transactivation domain. We inserted the coding region of Pit-1 cDNA, obtained by PCR, into a pET-20b(+) plasmid to produce recombinant Pit-1 in Escherichia coli BL21 (DE3) pLysS cells. Upon induction with isopropyl beta-D-thiogalactopyranoside, Pit-1 was expressed and accumulated as inclusion bodies in E. coli. The protein was then purified in one step by affinity chromatography on a nickel-nitrilotriacetic acid agarose column under denaturing conditions. This method yielded 0.7 mg of highly pure and stable protein per 200 ml of bacterial culture. A band of 40 kDa, resolved as recombinant ayu Pit-1 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, agrees well with the molecular mass calculated from the translated cDNA sequence. The purified recombinant Pit-1 was confirmed in vitro through Western blot analysis, using its monoclonal antibody. This monoclonal antibody detected Pit-1 in the nuclei of ayu developing pituitary by immunohistochemical reaction. It serves as a good reagent for the detection of ayu Pit-1 in situ. Copyright 2002 Elsevier Science (USA).

Zebrafish pit1 mutants lack three pituitary cell types and develop severe dwarfism.

PubMed

Nica, Gabriela; Herzog, Wiebke; Sonntag, Carmen; Hammerschmidt, Matthias

2004-05-01

The Pou domain transcription factor Pit-1 is required for lineage determination and cellular commitment processes during mammalian adenohypophysis development. Here we report the cloning and mutational analysis of a pit1 homolog from zebrafish. Compared with mouse, zebrafish pit1 starts to be expressed at a much earlier stage of adenohypophysis development. However, as in the mouse, expression is restricted to a subset of pituitary cell types, excluding proopiomelanocortin (pomc)-expressing cells (corticotropes, melanotropes) and possibly gonadotropes. We could identify two N-ethyl-N-nitrosourea-induced zebrafish pit1 null mutants. Most mutants die during larval stages, whereas survivors develop severe dwarfism. Mutant larvae lack lactotropes, somatotropes, and thyrotropes, although the adenohypophysis is of normal size, without any sign of increased apoptosis rates. Instead, mutant embryos initiate ectopic expression of pomc in pit1-positive cells, leading to an expansion of the Pomc lineage. Similarly, the number of gonadotropes seems increased, as indicated by the expression of gsualpha, a marker for thyrotropes and gonadotropes. In pit1 mutants, the total number of gsualpha-positive cells is normal despite the loss of gsualpha and tshbeta coexpressing cells. Together, these data suggest a transfating of the Pit1 lineage to the Pomc and possibly the gonadotroph lineages in the mutant, and a pomc- and gonadotropin-repressive role of Pit1 during normal zebrafish development. This is different from mouse, for which a repressive role of Pit-1 has only been reported for the gonadotropin Lhbeta, but not for Pomc. In sum, our data point to both conserved and class-specific aspects of Pit1 function during pituitary development in different vertebrate species.

Near infrared photoimmunotherapy in the treatment of disseminated peritoneal ovarian cancer

PubMed Central

Sato, Kazuhide; Hanaoka, Hirofumi; Watanabe, Rira; Nakajima, Takahito; Choyke, Peter L.; Kobayashi, Hisataka

2014-01-01

Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of intravenously injected antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. Herein, we evaluate the efficacy of NIR-PIT in a mouse model of disseminated peritoneal ovarian cancer. In vitro and in vivo experiments were conducted with a HER2-expressing, luciferase expressing, ovarian cancer cell line (SKOV-luc). An antibody-photosensitizer conjugate (APC) consisting of trastuzumab and a phthalocyanine dye, IRDye-700DX, was synthesized (tra-IR700) and cells or tumors were exposed to near infrared (NIR) light. In vitro PIT cytotoxicity was assessed with dead staining and luciferase activity in freely growing cells and in a 3D spheroid model. In vivo NIR-PIT was performed in mice with tumors implanted in the peritoneum and in the flank and these assessed by tumor volume and/or bioluminescence. In vitro NIR-PIT-induced cytotoxicity was light dose dependent. Repeated light exposures induced complete tumor cell killing in the 3D spheroid model. In vivo the anti-tumor effects of NIR-PIT were confirmed by significant reductions in both tumor volume and luciferase activity in the flank model (NIR-PIT vs control in tumor volume changes at day 10; p=0.0001, NIR-PIT vs control in luciferase activity at day 4; p=0.0237), and the peritoneal model (NIR-PIT vs control in luciferase activity at day 7; p=0.0037). NIR-PIT provided effective cell killing in this HER2 positive model of disseminated peritoneal ovarian cancer. Thus, NIR-PIT is a promising new therapy for the treatment of disseminated peritoneal tumors. PMID:25416790

Simulations and measurements of artificial cracks and pits in flat stainless steel plates using tone burst eddy-current thermography (TBET)

NASA Astrophysics Data System (ADS)

Libin, M. N.; Balasubramaniam, Krishnan; Maxfield, B. W.; Krishnamurthy, C. V.

2013-01-01

Tone Burst Eddy current Thermography (TBET) is a new hybrid, non-contacting, Non-Destructive Evaluation (NDE) method which employs a combination of Pulsed Eddy current Thermography (PEC) and Thermographic Non-Destructive Evaluation (TNDE). For understanding the influence of cracking and pitting on heat generation and flow within a metallic body, a fundamental knowledge of the detailed induced current density distribution in the component under test is required. This information enables us to calculate the amount of heat produced by the defects and how that heat diffuses to the surface where it is imaged. This paper describes simulation work done for artificial pits and cracks within pits on the far surface of poorly conducting metals like stainless steel. The first phase of this investigation simulates the transient thermal distribution for artificial 2D pit and crack-like defects using the finite element package COMSOL multi-physics with the AC/DC module and general heat transfer. Considering the reflection measurement geometry where thermal excitation and temperature monitoring are on the same surface, pitting reduces the material volume thereby contributing to a larger temperature rise for the same thermal energy input. A crack within a pit gives a further increase in temperature above the pure pit baseline. The tone burst frequency can be changed to obtain approximately uniform heating (low frequency) or heating of a thin region at the observation surface. Although front surface temperature changes due to 10% deep far-side pits in a 6 mm thick plate can be measured, it is not yet clear whether a 20% deep crack within this pit can be discriminated against the background. Both simulations and measurements will be presented. The objective of this work is to determine whether the TBET method is suitable for the detection and characterization of far side pitting, cracking and cracks within those pits.

Dependency of EBT2 film calibration curve on postirradiation time

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

Chang, Liyun, E-mail: liyunc@isu.edu.tw; Ding, Hueisch-Jy; Ho, Sheng-Yow

2014-02-15

Purpose: The Ashland Inc. product EBT2 film model is a widely used quality assurance tool, especially for verification of 2-dimensional dose distributions. In general, the calibration film and the dose measurement film are irradiated, scanned, and calibrated at the same postirradiation time (PIT), 1-2 days after the films are irradiated. However, for a busy clinic or in some special situations, the PIT for the dose measurement film may be different from that of the calibration film. In this case, the measured dose will be incorrect. This paper proposed a film calibration method that includes the effect of PIT. Methods: Themore » dose versus film optical density was fitted to a power function with three parameters. One of these parameters was PIT dependent, while the other two were found to be almost constant with a standard deviation of the mean less than 4%. The PIT-dependent parameter was fitted to another power function of PIT. The EBT2 film model was calibrated using the PDD method with 14 different PITs ranging from 1 h to 2 months. Ten of the fourteen PITs were used for finding the fitting parameters, and the other four were used for testing the model. Results: The verification test shows that the differences between the delivered doses and the film doses calculated with this modeling were mainly within 2% for delivered doses above 60 cGy, and the total uncertainties were generally under 5%. The errors and total uncertainties of film dose calculation were independent of the PIT using the proposed calibration procedure. However, the fitting uncertainty increased with decreasing dose or PIT, but stayed below 1.3% for this study. Conclusions: The EBT2 film dose can be modeled as a function of PIT. For the ease of routine calibration, five PITs were suggested to be used. It is recommended that two PITs be located in the fast developing period (1∼6 h), one in 1 ∼ 2 days, one around a week, and one around a month.« less

New Generation Energy Efficient Refractory Application in Soaking Pits of Bhilai Steel Plant, Sail

NASA Astrophysics Data System (ADS)

Roy, Indranil; Chintaiah, Perumetla; Bhattacharya, Ajoy Kr.; Garai, Swapan Kr.; Ray Choudhury, Pankaj Kr.; Tiwari, Laksman

In Bhilai Steel Plant (BSP), soaking pits are used for heating ingots for successive rolling into blooms. Pits are operated at a temperature of around 1350°C. Mixed gas (Mixture of Blast Furnace gas & Coke Oven gas) of calorific value around 2040 kcal/Nm3 is used as fuel. The walls of soaking pits were lined with traditional 38% Al2O3 firebricks and top 500mm was cast with 70% Al2O3 low cement castable (LCC). This type of lining results in frequent damages due to hitting by ingots while being lifted from pit by overhead cranes thus affecting the availability of pit. Life of pits was 2 to 2.5 years in BSP with 3-4 cold repairs and 3-4 hot repairs. Energy loss through the wall is also quite high in this type of lining. To triumph over the limitations of the conventional lining, a lining design was developed for the walls which consist of special 70% Al2O3 LCC having high hot strength (HMOR) in combination with specially design flexible SS-304 anchors. Ceramic fiber blanket and insulation bricks were provided between castable and the metallic shell of the pit to minimize the heat loss. A heating schedule was developed and introduced based on available infrastructure at BSP for proper curing of modified LCC based lining. After introduction of modified lining, pit no. 14/2 is running for more than 2.5 years without any repair. To capitalize the success, two more pits i.e. 12/1 and 9/2 were converted to modified lining. These pits are also running satisfactorily for more than 1.5 years. The modification has resulted in higher availability with substantial increase in production. Shell temperature of the modified pits reduced to 90° - 140°C from 120° - 200°C of conventional pits. This shows reduction in heat loss through walls, resulting less fuel consumption and energy saving of about 18%.

Detection probability of an in-stream passive integrated transponder (PIT) tag detection system for juvenile salmonids in the Klamath River, northern California, 2011

USGS Publications Warehouse

Beeman, John W.; Hayes, Brian; Wright, Katrina

2012-01-01

A series of in-stream passive integrated transponder (PIT) detection antennas installed across the Klamath River in August 2010 were tested using tagged fish in the summer of 2011. Six pass-by antennas were constructed and anchored to the bottom of the Klamath River at a site between the Shasta and Scott Rivers. Two of the six antennas malfunctioned during the spring of 2011 and two pass-through antennas were installed near the opposite shoreline prior to system testing. The detection probability of the PIT tag detection system was evaluated using yearling coho salmon implanted with a PIT tag and a radio transmitter and then released into the Klamath River slightly downstream of Iron Gate Dam. Cormack-Jolly-Seber capture-recapture methods were used to estimate the detection probability of the PIT tag detection system based on detections of PIT tags there and detections of radio transmitters at radio-telemetry detection systems downstream. One of the 43 PIT- and radio-tagged fish released was detected by the PIT tag detection system and 23 were detected by the radio-telemetry detection systems. The estimated detection probability of the PIT tag detection system was 0.043 (standard error 0.042). Eight PIT-tagged fish from other studies also were detected. Detections at the PIT tag detection system were at the two pass-through antennas and the pass-by antenna adjacent to them. Above average river discharge likely was a factor in the low detection probability of the PIT tag detection system. High discharges dislodged two power cables leaving 12 meters of the river width unsampled for PIT detections and resulted in water depths greater than the read distance of the antennas, which allowed fish to pass over much of the system with little chance of being detected. Improvements in detection probability may be expected under river discharge conditions where water depth over the antennas is within maximum read distance of the antennas. Improvements also may be expected if additional arrays of antennas are used.

Application of laser-based profilometry to tubing in power generating utilities

NASA Astrophysics Data System (ADS)

Doyle, James L.

1995-05-01

Over the past several years lasers have been employed in an ever widening number of applications in an incredibly diverse set of markets. In the area of nondestructive testing, however, laser-based systems have only recently made inroads into the commercial markets. About ten years ago QUEST Integrated, Inc., began working with the U.S. Navy to adapt the principal of laser triangulation to solve a serious maintenance related problem. The internal surfaces of marine boiler tubes were experiencing pitting and corrosion which had resulted in catastrophic shipboard failures. At that time, conventional visual methods only allowed operators to inspect the first eighteen inches of the tube using a rigid borescope. If any pits were located, a mechanical stylus mechanism was used to obtain an approximate depth measurement of the pit. The condition of the balance of the tube was then extrapolated based on this extremely limited amount of information. Often the worst pitting was found in the bends of the tube, which could not be inspected by the visual method. Finally, a catastrophic boiler failure on an aircraft carrier resulted in the initiation of a search by the U.S. Navy for a better solution. Quest was contracted to develop an articulated probe which could negotiate the full length of a boiler tube with multiple bends, and generate a complete digital map of the inside surface. A key requirement of this probe would be rapid and quantitative measurement of internal features such as ID pits and corrosion. In 1987 QUEST delivered the first laser- optic tube inspection system to the U.S. Navy for use in marine boiler tubes. The Laser Optic Tube Inspection System (LOTISTM) was immediately put to use and paid for itself many times over in reduced maintenance costs. Over the next six years several generations of LOTIS were developed for the U.S. Navy, each one providing more capabilities, improved inspection speeds, and more user friendly operator interface. Today, LOTIS is used for routine inspections on marine boiler tubes by the U.S. Navy, with units located in several parts of the United States and overseas. In 1993 QUEST began exploring the possibility of extending this technology to the inspection of commercial tubes used in power generation and chemical processing. The following is an overview of the use of laser profilometry for nondestructive testing.

Method for providing uranium articles with a corrosion-resistant anodized coating

DOEpatents

Waldrop, F.B.; Washington, C.A.

1981-01-07

Uranium articles are provided with anodized oxide coatings in an aqueous solution of an electrolyte selected from the group consisting of potassium phosphate, potassium hydroxide, ammonium hydroxide, and a mixture of potassium tetraborate and boric acid. The uranium articles are anodized at a temperature greater than about 75/sup 0/C with a current flow of less than about 0.036 A/cm/sup 2/ of surface area while the pH of the solution is maintained in a range of about 2 to 11.5. The pH values of the aqueous solution and the low current density utilized during the electrolysis prevent excessive dissolution of the uranium and porosity in the film or watering. The relatively high temperature of the electrolyte bath inhibits hydration and the attendant deleterious pitting so as to enhance corrosion resistance of the anodized coating.

The Effect of Solution Heat Treatment on an Advanced Nickel-Base Disk Alloy

NASA Technical Reports Server (NTRS)

Gayda, J.; Gabb, T. P.; Kantzos, P. T.

2004-01-01

Five heat treat options for an advanced nickel-base disk alloy, LSHR, have been investigated. These included two conventional solution heat treat cycles, subsolvus/oil quench and supersolvus/fan cool, which yield fine grain and coarse grain microstructure disks respectively, as well as three advanced dual microstructure heat treat (DMHT) options. The DMHT options produce disks with a fine grain bore and a coarse grain rim. Based on an overall evaluation of the mechanical property data, it was evident that the three DMHT options achieved a desirable balance of properties in comparison to the conventional solution heat treatments for the LSHR alloy. However, one of the DMHT options, SUB/DMHT, produced the best set of properties, largely based on dwell crack growth data. Further evaluation of the SUB/DMHT option in spin pit experiments on a generic disk shape demonstrated the advantages and reliability of a dual grain structure at the component level.

SEM Characterization of Extinguished Grains from Plasma-Ignited M30 Charges

NASA Technical Reports Server (NTRS)

Kinkennon, A.; Birk, A.; DelGuercio, M.; Kaste, P.; Lieb, R.; Newberry, J.; Pesce-Rodriguez, R.; Schroeder, M.

2000-01-01

M30 propellant grains that had been ignited in interrupted closed bomb experiments were characterize by scanning electron microscopy (SEM). Previous chemical analysis of extinguished grains had given no indications of plasma-propellant chemical interactions that could explain the increased burning rates that had been previously observed in full-pressure closed bomb experiments. (This does not mean that there is no unique chemistry occurring with plasma ignition. It may occur very early in the ignition event and then become obscured by the burning chemistry.) In this work, SEM was used to look at grain morphologies to determine if there were increases in the surface areas of the plasma-ignited grains which would contribute to the apparent increase in the burning rate. Charges were made using 30 propellant grains (approximately 32 grams) stacked in two tiers and in two concentric circles around a plastic straw. Each grain was notched so that, when the grains were expelled from the bomb during extinguishment, it could be determined in which tier and which circle each grain was originally packed. Charges were ignited in a closed bomb by either a nickel wire/Mylar-capillary plasma or black powder. The bomb contained a blowout disk that ruptured when the pressure reached 35 MPa, and the propellant was vented into a collection chamber packed with polyurethane foam. SEM analysis of the grains fired with a conventional black powder igniter showed no signs of unusual burning characteristics. The surfaces seemed to be evenly burned on the exteriors of the grains and in the perforations. Grains that had been subjected to plasma ignition, however, had pits, gouges, chasms, and cracks in the surfaces. The sides of the grains closest to the plasma had the greatest amount of damage, but even surfaces facing the outer wall of the bomb had small pits. The perforations contained gouges and abnormally burned regions (wormholes) that extended into the web. The SEM photos indicated that a grain from the top tier, which was farther away from the plasma ignition source, sustained more plasma-induced damage to the perforations and the web than did the grains on the bottom tier.

76 FR 12096 - McCloud-Pit Project; Notice of Availability of the Final Environmental Impact Statement for the...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-04

... Project; Notice of Availability of the Final Environmental Impact Statement for the Mccloud-Pit... Pit Rivers in Shasta County, California and has prepared a final environmental impact statement (EIS... and the alternatives for relicensing the McCloud-Pit Project. The final EIS documents the views of...

Cavitation pitting and erosion of aluminum 6061-T6 in mineral oil water

NASA Technical Reports Server (NTRS)

Rao, B. C. S.; Buckley, D. H.

1983-01-01

Cavitation erosion studies of aluminum 6061-T6 in mineral oil and in ordinary tap water are presented. The maximum erosion rate (MDPR, or mean depth of penetration rate) in mineral oil was about four times that in water. The MDPR in mineral oil decreased continuously with time, but the MDPR in water remained approximately constant. The cavitation pits in mineral oil were of smaller diameter and depth than the pits in water. Treating the pits as spherical segments, we computed the radius r of the sphere. The logarithm of h/a, where h is the pit depth and 2a is the top width of the pit, was linear when plotted against the logarithm of 2r/h - 1.

Microcrater investigations on lunar rock 12002

NASA Technical Reports Server (NTRS)

Hartung, J. B.; Hodges, F.; Horz, F.; Storzer, D.

1975-01-01

Relative ages of 26 submillimeter-sized pits from an equilibrium population in rock 12002 were measured by determining the densities of pits 0.7 microns in diameter and larger on the submillimeter-sized pits. Production rates for 0.7 micron diameter pits were determined from solar-flare track exposure age measurements, and the data for rock 12002 are consistent with previously obtained data for sample 15205 if a lower meteoroid flux prevailed in the past. Metal mounds or spherules within a microcrater pit glass were found to have a meteoritic composition, and an impact lining consisting of protruding crystals was observed. The crystals apparently developed during exposure to space immediately after the 200-micron diameter pit was formed by impact into an olivine grain.

Connecting Biology and Organic Chemistry Introductory Laboratory Courses through a Collaborative Research Project

ERIC Educational Resources Information Center

Boltax, Ariana L.; Armanious, Stephanie; Kosinski-Collins, Melissa S.; Pontrello, Jason K.

2015-01-01

Modern research often requires collaboration of experts in fields, such as math, chemistry, biology, physics, and computer science to develop unique solutions to common problems. Traditional introductory undergraduate laboratory curricula in the sciences often do not emphasize connections possible between the various disciplines. We designed an…

Coloring a Superabsorbent Polymer with Metal Ions: An Undergraduate Chemistry Experiment

ERIC Educational Resources Information Center

Yaung, Jing-Fun; Chen, Yueh-Huey

2009-01-01

A novel undergraduate chemistry experiment involving superabsorbent polymers commonly used in diapers and other personal care products is described. Students observe the removal of divalent transition-metal ions from aqueous solutions by the polymers. With the procedures provided, students are able to color the superabsorbent polymers with metal…

A Comprehensive General Chemistry Demonstration

ERIC Educational Resources Information Center

Sweeder, Ryan D.; Jeffery, Kathleen A.

2013-01-01

This article describes the use of a comprehensive demonstration suitable for a high school or first-year undergraduate introductory chemistry class. The demonstration involves placing a burning candle in a container adjacent to a beaker containing a basic solution with indicator. After adding a lid, the candle will extinguish and the produced…

The chemistry of salt-affected soils and waters

USDA-ARS?s Scientific Manuscript database

Knowledge of the chemistry of salt affected soils and waters is necessary for management of irrigation in arid and semi-arid regions. In this chapter we review the origin of salts in the landscape, the major chemical reactions necessary for prediction of the soil solution composition, and the use of...

Corrosion resistance improvement for 316L stainless steel coronary artery stents by trimethylsilane plasma nanocoatings.

PubMed

Eric Jones, John; Chen, Meng; Yu, Qingsong

2014-10-01

To improve their corrosion resistance and thus long-term biocompatibility, 316L stainless steel coronary artery stents were coated with trimethylsilane (TMS) plasma coatings of 20-25 nm in thickness. Both direct current (DC) and radio-frequency (RF) glow discharges were utilized for TMS plasma coatings and additional NH₃/O₂ plasma treatment to tailor the surface properties. X-ray photoelectron spectroscopy (XPS) was used to characterize the coating surface chemistry. It was found that both DC and RF TMS plasma coatings had Si- and C-rich composition, and the O- and N-contents on the surfaces were substantially increased after NH₃/O₂ plasma treatment. Surface contact angle measurements showed that DC TMS plasma nanocoating with NH₃/O₂ plasma treatment generated very hydrophilic surface. The corrosion resistance of TMS plasma coated stents was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization demonstrated that the TMS plasma coated stents imparted higher corrosion potential and pitting potential, as well as lower corrosion current densities as compared with uncoated controls. The surface morphology of stents before and after potentiodynamic polarization testing was analyzed with scanning electron microscopy, which indicated less corrosion on coated stents than uncoated controls. It was also noted that, from EIS data, the hydrophobic TMS plasma nanocoatings showed stable impedance modulus at 0.1 Hz after 21 day immersion in an electrolyte solution. These results suggest improved corrosion resistance of the 316L stainless steel stents by TMS plasma nanocoatings and great promise in reducing and blocking metallic ions releasing into the bloodstream. © 2014 Wiley Periodicals, Inc.

Cherry-Slush-Candling Apparatus

NASA Technical Reports Server (NTRS)

Stephens, James B.; Weiss, James R.; Hoover, Gordon

1996-01-01

Proposed infrared-scanning apparatus for use in bakeries making cherry pies detect cherry pits remaining in cherry slush after pitting process. Pits detected via their relative opacity to infrared radiation.

Solute-specific patterns and drivers of urban stream chemistry revealed by long-term monitoring in Baltimore, Maryland

NASA Astrophysics Data System (ADS)

Reisinger, A. J.; Woytowitz, E.; Majcher, E.; Rosi, E. J.; Groffman, P.

2017-12-01

Urban streams receive a myriad of chemical inputs from the surrounding landscape due to altered lithology (asphalt, concrete), leaky sewage infrastructure, and other human activities (road salt, fertilizer, industrial wastes, wastewater effluent), potentially leading to multiple chemical stressors occurring simultaneously. To evaluate potential drivers of water chemistry change, we used approximately 20 years of weekly water chemistry monitoring data from streams in the Baltimore Ecosystem Study (BES) to quantify trends of annual loads and flow-weighted concentrations for multiple solutes of interest, including nitrate (NO3-), phosphate (PO43-), total nitrogen (TN), total phosphorus (TP), chloride (Cl-), and sulfate (SO42-) and subsequently examined various gray and green infrastructure characteristics at the watershed scale. For example, we quantified annual volume and duration of reported sanitary sewer overflows (SSO) and cumulative storage volume and area of various best management practices (BMPs). Site- and solute-specific trends differed, but across our monitoring network we found evidence for decreasing annual export for multiple solutes. Additionally, we found that changes in gray- and green-infrastructure characteristics were related to changes in water quality at our most downstream (most urban) monitoring site. For example, annual NO3- loads increased with longer cumulative SSO duration, whereas annual PO43- and TP loads decreased with a cumulative BMP area in the watershed. Further, we used same long-term water chemistry data and multivariate analyses to investigate whether urban streams have unique water chemistry fingerprints representing the multiple chemical stressors at a given site, which could provide insight into sources and impacts of water-quality impairment. These analyses and results illustrate the major role gray and green infrastructure play in influencing water quality in urban environments, and illustrate that focusing on a variety of chemical stressors is necessary to gain a broader understanding of the issues affecting urban water quality.

Properties of hydrocarbon- and salt-contaminated flare pit soils in northeastern British Columbia (Canada).

PubMed

Arocena, J M; Rutherford, P M

2005-07-01

Many contaminated sites in Canada are associated with flare pits generated during past petroleum extraction operations. Flare pits are located adjacent to well sites, compressor stations and batteries and are often subjected to the disposal of wastes from the flaring of gas, liquid hydrocarbons and brine water. This study was conducted to evaluate the physical, chemical, electrical and mineral properties of three flare pit soils as compared to adjacent control soils. Results showed that particle size distribution, pH, total N, cation exchange capacity, exchangeable Mg(2+), and sodium adsorption ratio were similar in soils from flare pits and control sites. Total C, exchangeable Ca(2+), K(+) and Na(+), soluble Ca(2+), Mg(2+), K(+) and Na(+) and electrical conductivity were higher in flare pit soils compared to control soils. X-ray diffraction and scanning electron microscopic analyses showed the presence of gypsum [CaSO(4).2H(2)O], dolomite [CaMg(CO(3))(2)], pyrite [FeS(2)], jarosite [KFe(3)(OH)(6)(SO(4))(2)], magnesium sulphate, oxides of copper and iron+copper in salt efflorescence observed in flare pit soils. Soils from both flare pits and control sites contained mica, kaolonite and 2:1 expanding clays. The salt-rich materials altered the ionic equilibria in the flare pit soils; K(Mg-Ca) selectivity coefficients in control soils were higher compared to contaminated soils. The properties of soils (e.g., high electrical conductivity) affected by inputs associated with oil and gas operations might render flare pit soils less conducive to the establishment and growth of common agricultural crops and forest trees.

Pit Latrines and Their Impacts on Groundwater Quality: A Systematic Review

PubMed Central

Polizzotto, Matthew L.

2013-01-01

Background: Pit latrines are one of the most common human excreta disposal systems in low-income countries, and their use is on the rise as countries aim to meet the sanitation-related target of the Millennium Development Goals. There is concern, however, that discharges of chemical and microbial contaminants from pit latrines to groundwater may negatively affect human health. Objectives: Our goals were to a) calculate global pit latrine coverage, b) systematically review empirical studies of the impacts of pit latrines on groundwater quality, c) evaluate latrine siting standards, and d) identify knowledge gaps regarding the potential for and consequences of groundwater contamination by latrines. Methods: We used existing survey and population data to calculate global pit latrine coverage. We reviewed the scientific literature on the occurrence of contaminants originating from pit latrines and considered the factors affecting transport of these contaminants. Data were extracted from peer-reviewed articles, books, and reports identified using Web of ScienceSM, PubMed, Google, and document reference lists. Discussion: We estimated that approximately 1.77 billion people use pit latrines as their primary means of sanitation. Studies of pit latrines and groundwater are limited and have generally focused on only a few indicator contaminants. Although groundwater contamination is frequently observed downstream of latrines, contaminant transport distances, recommendations based on empirical studies, and siting guidelines are variable and not well aligned with one another. Conclusions: In order to improve environmental and human health, future research should examine a larger set of contextual variables, improve measurement approaches, and develop better criteria for siting pit latrines. PMID:23518813

Inhibitory effect of konjac glucomanan on pitting corrosion of AA5052 aluminium alloy in NaCl solution.

PubMed

Zhang, Kegui; Yang, Wenzhong; Xu, Bin; Chen, Yun; Yin, Xiaoshuang; Liu, Ying; Zuo, Huanzhen

2018-05-01

A natural carbohydrate polymer, konjac glucomanan, has been extracted from commercial product and studied as a green corrosion inhibitor for AA5052 aluminium alloy in 3.5 wt% NaCl solution by high-performance gel permeation chromatography (GPC), thermo gravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectra, electrochemical measurement and surface characterization techniques. The results of GPC measurements suggest the weight-average molecular weight and the number-average molecular weight of KGM with 98.2% purity are 1.61 × 10 5  g/mol and 1.54 × 10 5  g/mol, respectively. Potentiodynamic polarization curves show konjac glucomanan behaves as a mixed-type inhibitor with dominant anodic effect and that its maximum efficiency at 200 ppm is 94%. Electrochemical impedance spectroscopy (EIS) studies reveal the resistance of oxide film is approximately two orders of magnitude greater than the resistance of adsorbed inhibitor layer and that they both increase with KGM concentration. Moreover, in-situ electrochemical noise (EN) detection demonstrates that the growth and propagation stages of the pitting corrosion germinating on metal surface are blocked by polysaccharide additive, which is confirmed by the surface analysis of aluminium alloy using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Raman spectroscopy. At last, it is found that the addition of KGM makes it harder for water droplet containing NaCl to wet the metallic substrate. Copyright © 2018 Elsevier Inc. All rights reserved.

Biochemical and structural characterization of a novel cooperative binding mode by Pit-1 with CATT repeats in the macrophage migration inhibitory factor promoter

PubMed Central

Agarwal, Sorabh

2018-01-01

Abstract Overexpression of the proinflammatory cytokine macrophage migration inhibitory factor (MIF) is linked to a number of autoimmune diseases and cancer. MIF production has been correlated to the number of CATT repeats in a microsatellite region upstream of the MIF gene. We have characterized the interaction of pituitary-specific positive transcription factor 1 (Pit-1) with a portion of the MIF promoter region flanking a microsatellite polymorphism (−794 CATT5–8). Using fluorescence anisotropy, we quantified tight complex formation between Pit-1 and an oligonucleotide consisting of eight consecutive CATT repeats (8xCATT) with an apparent Kd of 35 nM. Using competition experiments we found a 23 base pair oligonucleotide with 4xCATT repeats to be the minimum DNA sequence necessary for high affinity interaction with Pit-1. The stoichiometry of the Pit-1 DNA interaction was determined to be 2:1 and binding is cooperative in nature. We subsequently structurally characterized the complex and discovered a completely novel binding mode for Pit-1 in contrast to previously described Pit-1 complex structures. The affinity of Pit-1 for the CATT target sequence was found to be highly dependent on cooperativity. This work lays the groundwork for understanding transcriptional regulation of MIF and pursuing Pit-1 as a therapeutic target to treat MIF-mediated inflammatory disorders. PMID:29186613

A comparison of conventional capture versus PIT reader techniques for estimating survival and capture probabilities of big brown bats (Eptesicus fuscus)

USGS Publications Warehouse

Ellison, L.E.; O'Shea, T.J.; Neubaum, D.J.; Neubaum, M.A.; Pearce, R.D.; Bowen, R.A.

2007-01-01

We compared conventional capture (primarily mist nets and harp traps) and passive integrated transponder (PIT) tagging techniques for estimating capture and survival probabilities of big brown bats (Eptesicus fuscus) roosting in buildings in Fort Collins, Colorado. A total of 987 female adult and juvenile bats were captured and marked by subdermal injection of PIT tags during the summers of 2001-2005 at five maternity colonies in buildings. Openings to roosts were equipped with PIT hoop-style readers, and exit and entry of bats were passively monitored on a daily basis throughout the summers of 2002-2005. PIT readers 'recaptured' adult and juvenile females more often than conventional capture events at each roost. Estimates of annual capture probabilities for all five colonies were on average twice as high when estimated from PIT reader data (P?? = 0.93-1.00) than when derived from conventional techniques (P?? = 0.26-0.66), and as a consequence annual survival estimates were more precisely estimated when using PIT reader encounters. Short-term, daily capture estimates were also higher using PIT readers than conventional captures. We discuss the advantages and limitations of using PIT tags and passive encounters with hoop readers vs. conventional capture techniques for estimating these vital parameters in big brown bats. ?? Museum and Institute of Zoology PAS.

Photoimmunotherapy of Gastric Cancer Peritoneal Carcinomatosis in a Mouse Model

PubMed Central

Sato, Kazuhide; Choyke, Peter L.; Kobayashi, Hisataka

2014-01-01

Photoimmunotherapy (PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. We performed PIT in a model of disseminated gastric cancer peritoneal carcinomatosis and monitored efficacy with in vivo GFP fluorescence imaging. In vitro and in vivo experiments were conducted with a HER2-expressing, GFP-expressing, gastric cancer cell line (N87-GFP). A conjugate comprised of a photosensitizer, IR-700, conjugated to trastuzumab (tra-IR700), followed by NIR light was used for PIT. In vitro PIT was evaluated by measuring cytotoxicity with dead staining and a decrease in GFP fluorescence. In vivo PIT was evaluated in a disseminated peritoneal carcinomatosis model and a flank xenograft using tumor volume measurements and GFP fluorescence intensity. In vivo anti-tumor effects of PIT were confirmed by significant reductions in tumor volume (at day 15, p<0.0001 vs. control) and GFP fluorescence intensity (flank model: at day 3, PIT treated vs. control p<0.01 and peritoneal disseminated model: at day 3 PIT treated vs. control, p<0.05). Cytotoxic effects in vitro were shown to be dependent on the light dose and caused necrotic cell rupture leading to GFP release and a decrease in fluorescence intensity in vitro. Thus, loss of GFP fluorescence served as a useful biomarker of cell necrosis after PIT. PMID:25401794

Avoidance-based human Pavlovian-to-instrumental transfer

PubMed Central

Lewis, Andrea H.; Niznikiewicz, Michael A.; Delamater, Andrew R.; Delgado, Mauricio R.

2013-01-01

The Pavlovian-to-instrumental transfer (PIT) paradigm probes the influence of Pavlovian cues over instrumentally learned behavior. The paradigm has been used extensively to probe basic cognitive and motivational processes in studies of animal learning but, more recently, PIT and its underlying neural basis have been extended to investigations in humans. These initial neuroimaging studies of PIT have focused on the influence of appetitively conditioned stimuli on instrumental responses maintained by positive reinforcement, and highlight the involvement of the striatum. In the current study, we sought to understand the neural correlates of PIT in an aversive Pavlovian learning situation when instrumental responding was maintained through negative reinforcement. Participants exhibited specific PIT, wherein selective increases in instrumental responding to conditioned stimuli occurred when the stimulus signaled a specific aversive outcome whose omission negatively reinforced the instrumental response. Additionally, a general PIT effect was observed such that when a stimulus was associated with a different aversive outcome than was used to negatively reinforce instrumental behavior, the presence of that stimulus caused a non-selective increase in overall instrumental responding. Both specific and general PIT behavioral effects correlated with increased activation in corticostriatal circuitry, particularly in the striatum, a region involved in cognitive and motivational processes. These results suggest that avoidance-based PIT utilizes a similar neural mechanism to that seen with PIT in an appetitive context, which has implications for understanding mechanisms of drug-seeking behavior during addiction and relapse. PMID:24118624

Degradation of Highly Alloyed Metal Halide Perovskite Precursor Inks: Mechanism and Storage Solutions

DOE PAGES

Dou, Benjia; Wheeler, Lance M.; Christians, Jeffrey A.; ...

2018-03-14

Whereas the promise of metal halide perovskite (MHP) photovoltaics (PV) is that they can combine high efficiency with solution-processability, the chemistry occurring in precursor inks is largely unexplored. Herein, we investigate the degradation of MHP solutions based on the most widely used solvents, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). For the MHP inks studied, which contain formamidinium (FA+), methylammonium (MA+), cesium (Cs+), lead (Pb2+), bromide (Br-), and iodide (I-), dramatic compositional changes are observed following storage of the inks in nitrogen in the dark. We show that hydrolysis of DMF in the precursor solution forms dimethylammonium formate, which subsequently incorporatesmore » into the MHP film to compromise the ability of Cs+ and MA+ to stabilize FA+-based MHP. The changes in solution chemistry lead to a modification of the perovskite film stoichiometry, band gap, and structure. The solid precursor salts are stable when ball-milled into a powder, allowing for the storage of large quantities of stoichiometric precursor materials.« less

Enhancing boron rejection in FO using alkaline draw solutions.

PubMed

Wang, Yi-Ning; Li, Weiyi; Wang, Rong; Tang, Chuyang Y

2017-07-01

This study provides a novel method to enhance boron removal in a forward osmosis (FO) process. It utilizes the reverse solute diffusion (RSD) of ions from alkaline draw solutions (DSs) and the concentration polarization of the hydroxyl ions to create a highly alkaline environment near the membrane active surface. The results show that boron rejection can be significantly enhanced by increasing the pH of NaCl DS to 12.5 in the active-layer-facing-feed-solution (AL-FS) orientation. The effect of RSD enhanced boron rejection was further promoted in the presence of concentration polarization (e.g., in the active-layer-facing-draw-solution (AL-DS) orientation). The current study opens a new dimension for controlling contaminant removal by FO using tailored DS chemistry, where the RSD-induced localized water chemistry change is taken advantage in contrast to the conventional method of chemical dosing to the bulk feed water. Copyright © 2017 Elsevier Ltd. All rights reserved.

Degradation of Highly Alloyed Metal Halide Perovskite Precursor Inks: Mechanism and Storage Solutions

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

Dou, Benjia; Wheeler, Lance M.; Christians, Jeffrey A.

Whereas the promise of metal halide perovskite (MHP) photovoltaics (PV) is that they can combine high efficiency with solution-processability, the chemistry occurring in precursor inks is largely unexplored. Herein, we investigate the degradation of MHP solutions based on the most widely used solvents, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). For the MHP inks studied, which contain formamidinium (FA+), methylammonium (MA+), cesium (Cs+), lead (Pb2+), bromide (Br-), and iodide (I-), dramatic compositional changes are observed following storage of the inks in nitrogen in the dark. We show that hydrolysis of DMF in the precursor solution forms dimethylammonium formate, which subsequently incorporatesmore » into the MHP film to compromise the ability of Cs+ and MA+ to stabilize FA+-based MHP. The changes in solution chemistry lead to a modification of the perovskite film stoichiometry, band gap, and structure. The solid precursor salts are stable when ball-milled into a powder, allowing for the storage of large quantities of stoichiometric precursor materials.« less

[Dissolved aluminum and organic carbon in soil solution under six tree stands in Lushan forest ecosystems].

PubMed

Wang, Lianfeng; Pan, Genxing; Shi, Shengli; Zhang, Lehua; Huang, Mingxing

2003-10-01

Different depths of soils under 6 tree stands in Lushan Botany Garden were sampled and water-digested at room temperature. The dissolved aluminum and organic carbon were then determined by colorimetry, using 8-hydroxylquilin and TOC Analyzer, respectively. The results indicated that even derived from a naturally identical soil type, the test soils exhibited a diverse solution chemistry, regarding with the Al speciation. The soil solutions under Japanese cedar, giant arborvitae and tea had lower pH values and higher contents of soluble aluminum than those under Giant dogwood, azalea and bamboo. Under giant arborvitae, the lowest pH and the highest content of total soluble aluminum and monomeric aluminum were found in soil solution. There was a significant correlation between soluble aluminum and DOC, which tended to depress the accumulation of toxic monomeric aluminum. The 6 tree stands could be grouped into 2 categories of solution chemistry, according to aluminum mobilization.

Effect of surface chemistries and characteristics of Ti6Al4V on the Ca and P adsorption and ion dissolution in Hank's ethylene diamine tetra-acetic acid solution.

PubMed

Chang, E; Lee, T M

2002-07-01

This study examined the influence of chemistries and surface characteristics of Ti6Al4V on the adsorption of Ca and P species and ion dissolution behavior of the material exposed in Hank's solution with 8.0 mM ethylene diamine tetra-acetic acid at 37 degrees C. The variation of chemistries of the alloy and nano-surface characteristics (chemistries of nano-surface oxides, amphoteric OH group adsorbed on oxides, and oxide thickness) was effected by surface modification and three passivation methods (34% nitric acid passivation. 400 degrees C heated in air, and aged in 100 degrees C water). X-ray photoelectron spectroscopy and Auger electron spectroscopy were used for surface analyses. The chemistries of nano-surface oxides in a range studied should not change the capability of Ca and P adsorption. Nor is the capability affected significantly by amphoteric OH group and oxide thickness. However, passivations influence the surface oxide thickness and the early stage ion dissolution rate of the alloy. The rate-limiting step of the rate can be best explained by metal-ion transport through the oxide film, rather than hydrolysis of the film. Variation of the chemistries of titanium alloy alters the electromotive force potential of the metal, thereby affecting the corrosion and ion dissolution rate.

13. DETAIL WEST OF TURBINE PIT SHOWING PIT DRAINED AND ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

13. DETAIL WEST OF TURBINE PIT SHOWING PIT DRAINED AND TURBINE EXPOSED. ORIGINAL WATER LEVEL SHOWN BY LINE JUST ABOVE ARCHED OPENING TO LEFT. WATER LINE AFTER 1982 INSTALLATION OF FLASH BOARDS REVEALED BY DARK STAIN. - Middle Creek Hydroelectric Dam, On Middle Creek, West of U.S. Route 15, 3 miles South of Selinsgrove, Selinsgrove, Snyder County, PA

10. Turbine Pit of Unit 5, view to the north. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. Turbine Pit of Unit 5, view to the north. Note the difference in configuration within this turbine pit as compared to one of the original pits illustrated in photograph number MT-105-A-11. - Washington Water Power Clark Fork River Noxon Rapids Hydroelectric Development, Powerhouse, South bank of Clark Fork River at Noxon Rapids, Noxon, Sanders County, MT

Weathering pits as indicators of the relative age of granite surfaces in the Cairngorm mountains, Scotland

USGS Publications Warehouse

Hall, A.M.; Phillips, W.M.

2006-01-01

Weathering pits 1-140 cm deep occur on granite surfaces in the Cairngorms associated with a range of landforms, including tors, glacially exposed slabs, large erratics and blockfields. Pit depth is positively correlated with cosmogenic exposure age, and both measures show consistent relationships on individual rock landforms. Rates of pit deepening are non-linear and a best fit is provided by the sigmoidal function D = b1+ exp(b2+b3/t). The deepest pits occur on unmodified tor summits, where 10 Be exposure ages indicate that surfaces have been exposed to weathering for a minimum of 52-297 ka. Glacially exposed surfaces with pits 10-46 cm deep have given 10 Be exposure durations of 21-79 ka, indicating exposure by glacial erosion before the last glacial cycle. The combination of cosmogenic exposure ages with weathering pit depths greatly extends the area over which inferences can be made regarding the ages of granite surfaces in the Cairngorms. Well-developed weathering pits on glacially exposed surfaces in other granite areas are potential indicators of glacial erosion before the Last Glacial Maximum. ?? Swedish Society for Anthropology and Geography.

Perforated Pit Membranes in Imperforate Tracheary Elements of Some Angiosperms

PubMed Central

SANO, YUZOU; JANSEN, STEVEN

2006-01-01

• Background and Aims The structure of pit membranes in angiosperms has not been fully examined and our understanding about the structure is incomplete. Therefore, this study aims to illustrate the micromorphology of pit membranes in fibres and tracheids of woody species from various families. • Methods Specimens from ten species from ten genera and eight families were prepared using two techniques and examined by field-emission scanning electron microscopy. • Key Results Interfibre pit membranes with an average diameter of <4 µm were frequently perforated or appeared to be very porous. In contrast, pit membranes in imperforate tracheary elements with distinctly bordered pits and an average diameter of ≥4 µm were homogeneous and densely packed with microfibrils. These differences were observed consistently not only among species but also within a single species in which different types of imperforate tracheary elements were present. • Conclusions This study demonstrates that the structure of interfibre pit membranes differs among cell types and the differences are closely associated with the specialization of the fibre cells. It is suggested that perforated pit membranes between specialized fibres contribute to the dehydration of the fibre cells at or soon after maturation. PMID:16520339

Evaluation of methods for attaching PIT tags and biotelemetry devices to freshwater mussels

USGS Publications Warehouse

Young, S.P.; Isely, J.J.

2008-01-01

We evaluated methods to attach PIT tags and transmitters to freshwater mussels. Mussels received externally-mounted PIT tags using cyanoacrylate or underwater epoxy, and a sub-group of those with PIT tags attached using cyanoacrylate also received dummy transmitters. Tag retention and survival were 100% after a 30 day laboratory observation period for each method. During the subsequent 18 months of field observation, underwater epoxy and cyanoacrylate proved to be adequate adhesives for attaching PIT tags and transmitters. Epoxy performed best with 100% PIT tag retention. Cyanoacrylate also provided high retention rates of PIT tags and transmitters, >90%. Mortality was minimal at 4.7% for all relocated mussels over 18 months. All mortalities were those tagged with cyanoacrylate. Three of the mortalities occurred among mussels fitted with dummy transmitters, and seven among PIT tags only. Percent recapture of the different tag/adhesive combinations ranged from 48 - 77.5% during 6- and 18-month surveys. Results suggest both adhesives provide a reliable method for external attachment of tags during freshwater mussel research; however, epoxy may be better suited because of slightly higher tag retention and reduced emersion times during attachment. Copyright ?? 2008 Malacological Society of Australasia.

Comparison of Chain Conformation of Poly(vinyl alcohol) in Solutions and Melts from Quantum Chemistry Based Molecular Dynamics Simulations

NASA Technical Reports Server (NTRS)

Jaffe, Richard; Han, Jie; Matsuda, Tsunetoshi; Yoon, Do; Langhoff, Stephen R. (Technical Monitor)

1997-01-01

Confirmations of 2,4-dihydroxypentane (DHP), a model molecule for poly(vinyl alcohol), have been studied by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. QC calculations at the 6-311G MP2 level show the meso tt conformer to be lowest in energy followed by the racemic tg, due to intramolecular hydrogen bond between the hydroxy groups. The Dreiding force field has been modified to reproduce the QC conformer energies for DHP. MD simulations using this force field have been carried out for DHP molecules in the gas phase, melt, and CHCl3 and water solutions. Extensive intramolecular hydrogen bonding is observed for the gas phase and CHCl3 solution, but not for the melt or aqueous solution, Such a condensed phase effect due to intermolecular interactions results in a drastic change in chain conformations, in agreement with experiments.

Progressive Retinal Nerve Fiber Layer Atrophy Associated With Enlarging Peripapillary Pit.

PubMed

Lee, Eun Ji; Kim, Tae-Woo

2017-02-01

To report a case in which progressive retinal nerve fiber layer (RNFL) atrophy was observed along with enlargement of the peripapillary pit. A 34-year-old male was diagnosed with primary open-angle glaucoma and followed up for 4 years with regular ophthalmic examinations. Both eyes were myopic (-10 D, OD and -10.5 D, OS), and untreated intraocular pressures were 18 mm Hg (OD) and 16 mm Hg (OS). A subtle depression of the superotemporal peripapillary area was deepened and emerged as a peripapillary pit during the follow-up period. With the enlargement of the peripapillary pit, a RNFL defect at the location of pit widened and thinned continuously. The enlargement of the pit was documented by the spectral-domain optical coherence tomography posterior pole scanning. Progressive RNFL atrophy was observed with enlargement of the peripapillary pit. The finding suggests that tensile stress derived from the scleral stretching may have significant influence on the integrity of the RNFL.

Heterogeneous nucleation of pits via step pinning during Si(100) homoepitaxy

NASA Astrophysics Data System (ADS)

Yitamben, E. N.; Butera, R. E.; Swartzentruber, B. S.; Simonson, R. J.; Misra, S.; Carroll, M. S.; Bussmann, E.

2017-11-01

Using scanning tunneling microscopy (STM), we investigate oxide-induced growth pits in Si thin films deposited by molecular beam epitaxy. In the transition temperature range from 2D adatom islanding to step-flow growth, systematic controlled air leaks into the growth chamber induce pits in the growth surface. We show that pits are also correlated with oxygen-contaminated flux from Si sublimation sources. From a thermodynamic standpoint, multilayer growth pits are unexpected in relaxed homoepitaxial growth, whereas oxidation is a known cause for step pinning, roughening, and faceting on elemental surfaces, both with and without growth flux. Not surprisingly, pits are thermodynamically metastable and heal by annealing to recover a smooth periodic step arrangement. STM reveals new details about the pits’ atomistic origins and growth dynamics. We give a model for heterogeneous nucleation of pits by preferential adsorption of Å-sized oxide nuclei at intrinsic growth antiphase boundaries, and subsequent step pinning and bunching around the nuclei.

Electronic structures of GeSi nanoislands grown on pit-patterned Si(001) substrate

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

Ye, Han, E-mail: Dabombyh@aliyun.com; Yu, Zhongyuan

2014-11-15

Patterning pit on Si(001) substrate prior to Ge deposition is an important approach to achieve GeSi nanoislands with high ordering and size uniformity. In present work, the electronic structures of realistic uncapped pyramid, dome, barn and cupola nanoislands grown in (105) pits are systematically investigated by solving Schrödinger equation for heavy-hole, which resorts to inhomogeneous strain distribution and nonlinear composition-dependent band parameters. Uniform, partitioned and equilibrium composition profile (CP) in nanoisland and inverted pyramid structure are simulated separately. We demonstrate the huge impact of composition profile on localization of heavy-hole: wave function of ground state is confined near pit facetsmore » for uniform CP, at bottom of nanoisland for partitioned CP and at top of nanoisland for equilibrium CP. Moreover, such localization is gradually compromised by the size effect as pit filling ratio or pit size decreases. The results pave the fundamental guideline of designing nanoislands on pit-patterned substrates for desired applications.« less

Structural Design and Monitoring Analysis of Foundation Pit Support in Yiwu Huishang Tiandi

NASA Astrophysics Data System (ADS)

Zhang, Chunsu

2017-08-01

Huishang Tiandi deep foundation pit in Yiwu is a two-story basement,which is located in the downtown area and adjacent to the city center main traffic trunk. The surrounding environment is too com-plex to slope. The excavation depth is large, the formation is weak and complex, and the groundwater level is high.In order to ensure the safety of the foundation wall and the surrounding environment, the deformation of the foundation pit support is strictly controlled, and the deformation and internal force of the foundation supporting structure and the surrounding building are monitored.The deformation law of the foundation pit is obtained through the analysis of the horizontal displacement, the deformation rate of the supporting struc-ture, the surrounding environment of the foundation pit and the internal force of the anchor cable. The relia-bility and rationality of the design of foundation pit support are verified. It is of reference value for the de-sign and construction of other deep foundation pit engineering in Yiwu area.

Mapping sand and gravel pits in the Patuxent River watershed

NASA Technical Reports Server (NTRS)

Schmidt, T. J.; Witt, R. G.

1981-01-01

LANDSAT data from July 1973 and June 1978 for the Patuxent River Watershed of Maryland were processed in an effort to devise an economical method of monitoring the reclamation of sand and gravel pits. ASTEP-II and IDIMS software were utilized to derive signatures for sand and gravel pits and other land use/land cover types. Both unsupervised and supervised classifications of the two data sets were produced. Resultant statistics and color output products were compared in order to determine the extent of reclamation and expansion of sand and gravel pits over the five-year time span and to check the locations of more recent sand and gravel pits. Preliminary results indicate that, for a selected northern sub-acre, signatures derived for sand and gravel pits were nearly 90 percent accurate.

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

Adamson, P.; Austin, J.; Cao, S. V.

This Letter of Intent outlines a proposal to build a large, yet cost-effective, 100 kton fiducial mass water Cherenkov detector that will initially run in the NuMI beam line. The CHIPS detector (CHerenkov detector In Mine PitS) will be deployed in a flooded mine pit, removing the necessity and expense of a substantial external structure capable of supporting a large detector mass. There are a number of mine pits in northern Minnesota along the NuMI beam that could be used to deploy such a detector. In particular, the Wentworth Pit 2W is at the ideal off-axis angle to contribute tomore » the measurement of the CP violating phase. The detector is designed so that it can be moved to a mine pit in the LBNE beam line once that becomes operational.« less

Simulation of Fatigue Crack Initiation at Corrosion Pits With EDM Notches

NASA Technical Reports Server (NTRS)

Smith, Stephen W.; Newman, John A.; Piascik, Robert S.

2003-01-01

Uniaxial fatigue tests were conducted to compare the fatigue life of laboratory produced corrosion pits, similar to those observed in the shuttle main landing gear wheel bolt-hole, and an electro-discharged-machined (EDM) flaw. EDM Jaws are used to simulate corrosion pits during shuttle wheel (dynamometer) testing. The aluminum alloy, (AA 7050) laboratory fatigue tests were conducted to simulate the local stress level contained in the wheel bolt-hole. Under this high local stress condition, the EDM notch produced a fatigue life similar to test specimens containing corrosion pits of similar size. Based on the laboratory fatigue test results, the EDM Jaw (semi-circular disc shaped) produces a local stress state similar to corrosion pits and can be used to simulate a corrosion pit during the shuttle wheel dynamometer tests.