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1

Neutron capture autoradiographic determination of 10B distributions and concentrations in biological samples for boron neutron capture therapy  

NASA Astrophysics Data System (ADS)

It is necessary for effective boron neutron capture therapy (BNCT) to accumulate 10B atoms in the tumor cells. We prepared a cationic liposome entrapped 10B compound for the delivery system and examined the delivery capacity of 10B atoms to pancreatic cancer cell, AsPC-1, in vivo. It is required to achieve an accurate measurement of 10B distributions and concentrations in biological samples with a sensitivity in the ppm range for BNCT. We applied CR-39 (polyallyldiglycol carbonate) plastic track detectors to ?-autoradiographic measurements of the 10B biodistribution in sliced whole-body samples of mice. To selectively desensitize undesirable proton tracks, we applied PEW (KOH+C 2H 5OH+H 2O) solution to the etching of CR-39 detector. The subsequent use of an alpha-track radiographic image analysis system enabled a discrimination between alpha tracks and recoiled proton tracks by the track size selection method. This enabled us to estimate quantitatively the distributions of 10B concentrations within the tissue sections by comparing with suitable standards.

Yanagie, Hironobu; Ogura, Koichi; Matsumoto, Toshio; Eriguchi, Masazumi; Kobayashi, Hisao

1999-11-01

2

Boron distribution in sintered silicon carbide  

SciTech Connect

Boron concentrations on intergranular and transgranular fracture areas in sintered SiC were measured; {alpha}-SiC grains oriented parallel to the fracture surface would fracture at the {alpha}-{beta} interphase boundary. Auger electron spectroscopy showed that boron does not segregate to these boundaries in sintered SiC. This conclusion was generalized to include the other types of SiC grain boundaries. The absence of boron at grain boundaries suggests that its role in sintering is not to enhance diffusion rates. Chemical reactions and free surface segregation, which may explain the increased densification of SiC when B is present, are discussed.

Carter, W.D.; Holloway, P.H. (Univ. of Florida, Gainesville (USA)); White, C.; Clausing, R. (Oak Ridge National Lab., TN (USA))

1988-01-01

3

Abundance and distribution of boron in the Hauzenberg (Bavaria) granite complex  

SciTech Connect

Hercynian S-type granites from the Hauzenberg igneous complex show a range of boron concentration from 1 to 12 ppm. The whole-rock boron data are not significantly correlated with concentrations of other trace elements (Zr, Rb, Ba, Sr, Ni, V, Co, Cu, Zn, F); neither is boron correlated with the major elements (except with sodium) or with the differentiation index (DI). The boron budget in the rock-forming minerals (plagioclase, alkali feldspar, quartz, biotite, muscovite) of the tourmaline-free granites reveals that the highest concentrations of boron occur in muscovite, whereas the greatest amount of boron is incorporated in plagioclase (57-69%) due to its high modal amount. Boron in plagioclase increases with the extent of of sericitization (obtained by X-ray diffractometry). Muscovite in a pegmatite contains more than 50% of the total boron. The areal distribution of boron within the complex is neither uniform nor random; an increase of boron concentrations from granodioritic to granitic rocks is indicated, whereas the late differentiates are depleted in boron.

Sauerer, A.; Troll, G. (Institut fuer Mineralogie und Petrographie der Universitaet Muenchen (Germany, F.R.))

1990-01-01

4

Relationship Between Soil Extractable Boron and Tissue Concentrations in Rosaceae Shrubs in Utah  

Microsoft Academic Search

Native species are distributed among a broad range of soil and environmental conditions and vary widely in boron (B) content. Soil B tests have been used often, but inconsistently, to characterize the supply of B to cultivated crop species; however such tests have never been correlated with B concentrations in native species. This study was designed to determine (a) how

D. Carter; K. T. Harper; A. K. Shiffler; V. D. Jolley; J. K. Harper

2003-01-01

5

Boron solution and distribution in ?-Fe : Application to boron steel  

NASA Astrophysics Data System (ADS)

Formation-energy formalism for a general interface is developed and applied to ?-Fe host with boron (B) impurities. In bulk ?-Fe , B impurities prefer to be located at substitutional position rather than at interstitial. The estimated formation energy of substitutional B is lower than that of interstitial B by 0.10 eV in the dilute impurity limit. At the surface, however, the interstitial site is found to be preferred, and B impurities on top of the surface are the most stable as compared to those in the subsurface positions. The stability of B impurities increases as they get close to the free surface, indicating that B impurities tend to segregate toward the free surface. This surface segregation of B impurities is found to be the direct reflection of the surface-energy minimization of Fe-B system. Based on the first-principles band calculations, it is deduced that the dominant B diffusion behavior near the free surface is described by the interstitial-to-interstitial diffusion mechanism.

Baik, Seung Su; Min, B. I.; Kwon, S. K.; Koo, Y. M.

2010-04-01

6

BORON  

Technology Transfer Automated Retrieval System (TEKTRAN)

Knowledge of boron chemical speciation is important in understanding bioavailability, excretion, and retention of boron derived from supplemental dietary sources. Undissociated boric acid is the predominant species of boron in most natural freshwater systems. Five antibiotics, one with apparent pote...

7

Soil Properties Influence Distribution of Extractable Boron in Soil Profile  

Microsoft Academic Search

Depth distribution of boron (B) extractable by hot calcium chloride (HCC), potassium dihydrogen phosphate (PDP), and tartaric acid (TA) in some typical B?deficient Inceptisols, Entisols, and Alfisols in relation to soil properties was studied. The magnitude of B extraction followed the order HCC > PDP > TA for Inceptisols, TA > HCC > PDP for Entisols, and PDP > HCC

Dibyendu Sarkar; Biswapati Mandal; Manik Chandra Kundu; Javid Ahmad Bhat

2008-01-01

8

Boron  

Technology Transfer Automated Retrieval System (TEKTRAN)

Boron is an essential micronutrient element required for plant growth. Boron deficiency is wide-spread in crop plants throughout the world especially in coarse-textured soils in humid areas. Boron toxicity can also occur, especially in arid regions under irrigation. Plants respond directly to the...

9

INFLUENCE OF GERMANIUM CONCENTRATION AND HOMOGENEOUS BORON DOPING ON MICROSTRUCTURE, KINETICS, AND SHEET RESISTANCE OF NICKEL  

E-print Network

1 INFLUENCE OF GERMANIUM CONCENTRATION AND HOMOGENEOUS BORON DOPING ON MICROSTRUCTURE, KINETICS..............................................................................15 1.2 Silicon-Germanium in Semiconductor Technologies.................................................................................................................25 2.1.1 Silicon-Germanium Binary System

Florida, University of

10

Distribution of boron in the Tip Top pegmatite, Black Hills, South Dakota  

SciTech Connect

Experimental evidence has shown the importance of boron on the crystallization behavior of granitic systems; however, the intercrystalline and intracrystalline distribution of boron in mineral phases crystallizing from granitic systems is not well documented. The distribution of boron between coexisting phases in the Tip Top pegmatite, South Dakota, is as follows: beryl ca = quartz ca = triphylite ca = montebrasite ca = potassium feldspar < biotite < albite < muscovite < spodumene << tourmaline. The bulk boron content of the Tip Top pegmatite decreases significantly with the termination of tourmaline crystallization. The significant decrease in boron in the inner zones of the pegmatite is consistent with the depletion of boron in the granite melt by either the crystallization of tourmaline from the granitic melt or the partitioning of boron into an exsolved aqueous solutions. 35 references.

Shearer, C.K.; Papike, J.J.

1986-02-01

11

Response function during oxygen sputter profiling for deconvolution of boron spatial distribution  

Microsoft Academic Search

We have studied the spatial distribution of a surface deposited boron layer by secondary ion mass spectrometry (SIMS) using oxygen beams of various incident energies. A boron layer around 0.4 nm thick was deposited by using electron-gun evaporation combined with liquid nitrogen cooling of the target. The SIMS boron profiles can be approximated closely by exponential-like distributions with decay lengths

Lin Shao; Jiarui Liu; Chong Wang; Ki B. Ma; Jianming Zhang; John Chen; Daniel Tang; Sanjay Patel; Wei-Kan Chu

2004-01-01

12

Boron concentration measurements by alpha spectrometry and quantitative neutron autoradiography in cells and tissues treated with different boronated formulations and administration protocols.  

PubMed

The possibility to measure boron concentration with high precision in tissues that will be irradiated represents a fundamental step for a safe and effective BNCT treatment. In Pavia, two techniques have been used for this purpose, a quantitative method based on charged particles spectrometry and a boron biodistribution imaging based on neutron autoradiography. A quantitative method to determine boron concentration by neutron autoradiography has been recently set-up and calibrated for the measurement of biological samples, both solid and liquid, in the frame of the feasibility study of BNCT. This technique was calibrated and the obtained results were cross checked with those of ? spectrometry, in order to validate them. The comparisons were performed using tissues taken form animals treated with different boron administration protocols. Subsequently the quantitative neutron autoradiography was employed to measure osteosarcoma cell samples treated with BPA and with new boronated formulations. PMID:24387908

Bortolussi, Silva; Ciani, Laura; Postuma, Ian; Protti, Nicoletta; Luca Reversi; Bruschi, Piero; Ferrari, Cinzia; Cansolino, Laura; Panza, Luigi; Ristori, Sandra; Altieri, Saverio

2014-06-01

13

Boron Stress and Boron Tissue Distribution in Arbidopsis thaliana and Pelargonium X Hortorum  

Technology Transfer Automated Retrieval System (TEKTRAN)

The micronutrient boron is essential for plant growth and development. Deficient or excessive levels of this micronutrient result in the formation of growth defects that reduce yield in crop plants and result in discarding of horticultural plants. To study the responses of plants to altered boron ...

14

Differences in Shoot Boron Concentrations, Leaf Symptoms, and Yield of Turkish Barley Cultivars Grown on Boron?Toxic Soil in Field  

Microsoft Academic Search

Using 10 barley Turkish cultivars (Hordeum vulgare L.) field experiments were carried out on soils containing normal and very high soluble boron (B) concentration to study genotypic variation in tolerance to B toxicity in soil and the relationships between the shoot or leaf concentrations of B, severity of B?toxicity symptoms and yield. As judged by differences in degree of severity

B. Torun; M. Kalayci; L. Ozturk; A. Torun; M. Aydin; I. Cakmak

2002-01-01

15

Peculiarities of boron distribution in as-grown boron-doped diamond  

NASA Astrophysics Data System (ADS)

Boron doped diamond (BDD) single crystals have been grown under conditions of high isostatic pressure by the temperature gradient method. Numerous equilateral triangles were found on the fluorescence images of {111}-diamond facets. Structural peculiarities of BDD were investigated by JEM-2010 transmission electron microscope with GIF Quantum attachment for electron energy loss spectroscopy (EELS). High resolution image of diamond lattice revealed some distorted {111}-layers. EELS testifies the presence of boron in distorted regions of diamond lattice. The crystallographic features of BDD and their connection with the superconductivity are discussed.

Blank, V. D.; Kulnitskiy, B. A.; Perezhogin, I. A.; Terentiev, S. A.; Nosukhin, S. A.; Kuznetsov, M. S.

2014-09-01

16

Cooling Rate Dependence of Boron Distribution in Low Carbon Steel  

NASA Astrophysics Data System (ADS)

The behavior of boron (B) segregation to austenite grain boundaries in low carbon steel was studied using particle tracking autoradiography (PTA) and secondary ion mass spectroscopy (SIMS). An effective time method was used to compare the cooling rate (CR) dependence of this segregation during continuous cooling and its time dependence during isothermal holding. Comparison of these segregation behaviors has confirmed that the CR dependence of B segregation agrees well with its time dependence and is mainly a result of the phenomenon of nonequilibrium segregation. Based on the CR dependence of B segregation, the continuous cooling transformation behavior of B-bearing steel as compared with B-free steel was also investigated using dilatometry and microstructural observations. The addition of a small amount of B to low carbon steel retarded significantly the austenite-to-ferrite transformation and finally expanded the range of cooling programs that result in the formation of bainitic microstructures. Analysis of the B distribution has confirmed that this retardation effect of B on ferrite transformation is attributed to the CR dependence of B segregation to austenite grain boundaries during cooling after austenitization.

Mun, Dong Jun; Shin, Eun Joo; Cho, Kyung Chul; Lee, Jae Sang; Koo, Yang Mo

2012-05-01

17

Boron distribution and the effect of lime on boron uptake by pansy, petunia, and gerbera plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Reports of boron (B) deficiency have become more prevalent in pansy (Viola ×wittrockiana), petunia (Petunia ×hybrida), and gerbera (Gerbera jamesonii) plug production. When symptoms are observed in production the presence and severity of symptoms have no pattern, symptomatic plants can be located a...

18

Effect of aluminum concentration and boron dopant on environmental embrittlement in FeAl aluminides  

SciTech Connect

The room-temperature tensile properties of FeAl aluminides were determined as functions of aluminum concentration (35 to 43 at. % Al), test environment, and surface (oil) coating. The two lower aluminum alloys containing 35 and 36.5% Al are prone to severe environmental embrittlement, while the two higher aluminum alloys with 40 and 43% Al are much less sensitive to change in test environment and surface coating. The reason for the different behavior is that the grain boundaries are intrinsically weak in the higher aluminum alloys, and these weak boundaries dominate the low ductility and brittle fracture behavior of the 40 and 43% Al alloys. When boron is added to the 40% Al alloy as a grain-boundary strengthener, the environmental effect becomes prominent. In this case, the tensile ductility of the boron-doped alloy, just like that of the lower aluminum alloys, can be dramatically improved by control test environment (e.g. dry oxygen vs air). Strong segregation of boron to the grain boundaries, with a segregation factor of 43, was revealed by Auger analyses. 28 refs., 2 figs., 3 tabs.

Liu, C.T.; George, E.P.

1990-01-01

19

Effect of boron concentration on recombination at the p-Si–Al{sub 2}O{sub 3} interface  

SciTech Connect

We examine the surface passivation properties of Al{sub 2}O{sub 3} deposited on boron-doped planar ?100? crystalline silicon surfaces as a function of the boron concentration. Both uniformly doped and diffused surfaces are studied, with surface boron concentrations ranging from 9.2?×?10{sup 15} to 5.2?×?10{sup 19}?cm{sup ?3}. Atmospheric pressure chemical vapor deposition and thermal atomic layer deposition are used to deposit the Al{sub 2}O{sub 3} films. The surface recombination rate of each sample is determined from photoconductance measurements together with the measured dopant profiles via numerical simulation, using the latest physical models. These values are compared with calculations based on the interface properties determined from capacitance–voltage and conductance measurements. It is found that the fundamental surface recombination velocity of electrons, S{sub n0}, which describes the chemical passivation of the interface, is independent of the surface boron concentration N{sub s} for N{sub s}???3?×?10{sup 19}?cm{sup ?3}, and in excellent agreement with values calculated from the interface state density D{sub it} and capture coefficients c{sub n} and c{sub p} measured on undiffused boron-doped surfaces. We conclude that the physical properties of the Si–Al{sub 2}O{sub 3} interface are independent of the boron dopant concentration over this range.

Black, Lachlan E., E-mail: lachlan.black@anu.edu.au; Allen, Thomas; Cuevas, Andres [Research School of Engineering, The Australian National University, Canberra, ACT 0200 (Australia); McIntosh, Keith R. [PV Lighthouse, Coledale, NSW 2515 (Australia)

2014-03-07

20

BORON CONCENTRATIONS IN MILK FROM MOTHERS OF EXCLUSIVELY BREAST-FED HEALTHY FULL-TERM INFANTS ARE STABLE DURING THE FIRST FOUR MONTHS OF LACTATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Because boron is a bioactive element that satisfies several of the criteria for essentiality in humans, the aim of the present work was to determine the profile of boron metabolism in human milk during the first 4 mo of lactation. The concentration of boron and other minerals was determined in arch...

21

Detailed dose distribution prediction of Cf-252 brachytherapy source with boron loading dose enhancement.  

PubMed

The purpose of this work is to evaluate the dose rate distribution and to determine the boron effect on dose rate distribution for (252)Cf brachytherapy source. This study was carried out using a Monte Carlo simulation. To validate the Monte Carlo computer code, the dosimetric parameters were determined following the updated TG-43 formalism and compared with current literature data. The validated computer code was then applied to evaluate the neutron and photon dose distribution and to illustrate the boron loading effect. PMID:19889549

Ghassoun, J; Mostacci, D; Molinari, V; Jehouani, A

2010-02-01

22

Electroextraction of boron from boron carbide scrap  

SciTech Connect

Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ? 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

Jain, Ashish [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Anthonysamy, S., E-mail: sas@igcar.gov.in [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ghosh, C. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ravindran, T.R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Divakar, R.; Mohandas, E. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India)

2013-10-15

23

Toward prompt gamma spectrometry for monitoring boron distributions during extra corporal treatment of liver metastases by boron neutron capture therapy: a Monte Carlo simulation study.  

PubMed

A Monte Carlo calculation was carried out for boron neutron capture therapy (BNCT) of extra corporal liver phantom. The present paper describes the basis for a subsequent clinical application of the prompt gamma spectroscopy set-up aimed at in vivo monitoring of boron distribution. MCNP code was used first to validate the homogeneity in thermal neutron field in the liver phantom and simulate the gamma ray detection system (collimator and detector) in the treatment room. The gamma ray of 478 keV emitted by boron in small specific region can be detected and a mathematical formalism was used for the tomography image reconstruction. PMID:19394243

Khelifi, R; Nievaart, V A; Bode, P; Moss, R L; Krijger, G C

2009-07-01

24

III 1 BORON  

Technology Transfer Automated Retrieval System (TEKTRAN)

Boron chemistry, analysis, environmental exposure, metabolism, anthropomorphic sources, beneficial physiological effects, and toxicity are reviewed. Boron is widely distributed in nature and always occurs bound to oxygen. Boron biochemistry is essentially that of boric acid, which forms ester comple...

25

Micro-Scale Distribution of Trace Elements in a High Boron Soil from Kern County, California  

E-print Network

Micro-Scale Distribution of Trace Elements in a High Boron Soil from Kern County, California P. Fox and 500 mg kg -1 soil total). White deposits were noted throughout the soil profile. The soil peds were air dried at 35º C and impregnated with LR White high grade resin under a vacuum in order to retain

26

Boron doping of diamond powder by enhanced diffusion and forced diffusion: Diffusion concentrations, mechanical, chemical and optical properties  

NASA Astrophysics Data System (ADS)

Diamond, with its unique mechanical properties, is an excellent material for a wide range of applications. However, there exist some problems. One such problem is integration of diamond of diamond into tool's (usually tungsten-carbide) lattice matrix for the purpose of increasing its performance. The presence of cobalt in the matrix, which acts as a poison for diamond, causes graphitization and degradation of diamond. In addition, diamond graphitizes at sintering temperatures (1770 K). The results of this work suggest that boron has produced a protective layer for diamond, thus reducing the effects of annealing at high temperatures. Boron has been introduced into single crystal high pressure, high temperature diamond powder by enhanced diffusion and forced diffusion techniques. Enhanced diffusion resulted in higher concentrations of boron in diamond powder. Total boron concentrations of 500 to 600 ppm, and 10sp{20} cmsp{-3} at a depth of 0.5 micrometer, have been achieved. Hardness tests performed on doped samples reveal that diamond did not lose its strength due to diffusion at elevated temperatures. Raman spectroscopy and X-ray diffraction analysis did not show any change in the "quality" of diamond due to doping. Oxidation experiments performed on doped and undoped samples revealed that the samples with the highest boron concentrations had superior performance and resistance to oxidation. Final weight loss in these samples was much less than in undoped samples and samples with low boron concentrations. Scanning electron microscopy of these samples showed that degradation due to oxidation of heavily doped diamond samples was significantly less than other samples.

Golshani, Fariborz

27

Boron dose determination for BNCT using Fricke and EPR dosimetry  

SciTech Connect

In Boron Neutron Capture Therapy (BNCT) the dominant dose delivered to the tumor is due to {alpha} and {sup 7}Li charged particles resulting from a neutron capture by {sup 10}B and is referred to herein as the boron dose. Boron dose is directly attributable to the following two independent factors, one boron concentration and the neutron capture energy dependent cross section of boron, and two the energy spectrum of the neutrons that interact with boron. The neutron energy distribution at a given point is dictated by the incident neutron energy distribution, the depth in tissue, geometrical factors such as beam size and patient`s dimensions. To account for these factors can be accommodated by using Monte Carlo theoretical simulations. However, in conventional experimental BNCT dosimetry, e.g., using TLDs or ionization chambers, it is only possible to estimate the boron dose. To overcome some of the limitations in the conventional dosimetry, modifications in ferrous sulfate dosimetry (Fricke) and Electron Paramagnetic Resonance (EPR) dosimetry in alanine, enable to measure specifically boron dose in a mixed gamma neutron radiation fields. The boron dose, in either of the dosimeters, is obtained as a difference between measurements with boronated and unboronated dosimeters. Since boron participates directly in the measurements, the boron dosimetry reflects the true contribution, integral of the neutron energy spectrum with boron cross section, of the boron dose to the total dose. Both methods are well established and used extensively in dosimetry, they are presented briefly here.

Wielopolski, L. [Brookhaven National Lab., Upton, NY (United States); Ciesielski, B. [Medical Academy, Gdansk (Poland). Dept. of Physics and Biophysics

1995-02-01

28

Aluminum distribution in the boron framework of ?-AlB 12  

NASA Astrophysics Data System (ADS)

The crystal structure of ?-AlB 12 ( P2 12 12 1; a = 16.573(4), b = 17.510(3), c = 10.144(1)Å) was reinvestigated by single-crystal X-ray diffractometry and the nature of the metal distribution in the boron framework examined. Starting from the structure data published by Hughes et al. (Journal of the American Chemical Society 83, 2337 (1977)), 458 independent parameters, including the occupancies of 11 Al sites, were finally refined to a conventional R value of 2.9%. A total of 5282 observed unique reflections (Mo K? radiation; 2? < 64°) were used. Although distributed in an apparently complicated manner, the aluminum atoms occur in the boron framework according to a simple rule as in the crystals of the ?-AlB 12 structure type. The numbers of the valence electrons of Al, allotted to the six boron subunits, B 12(i-iv), B 20-(C 2, C s), proportionately to the contact frequencies of Al with the units, are 2.2, 1.9, 2.2, 1.9, 5.3, and 5.2, respectively. The charge assignment is compatible with the ionic formula {20}/{3}Al+3 · 4B 12-2 · 2 B20-6, proposed from preliminary molecular orbital calculations. A negative charge balance among the six boron units at about 1:1:1:1:3:3 seems to be essential for making up the stable boron framework of ?-AlB 12.

Higashi, Iwami

1983-05-01

29

Electron momentum distributions and ionization energy spectra of boron trifluoride  

NASA Astrophysics Data System (ADS)

The complete valence shell binding energy spectra and valence orbital electron momentum distributions for BF 3 have been measured by (e, 2e) spectroscopy or electron momentum spectroscopy (EMS), at a total energy of 1200 eV and using symmetric non-coplanar kinematics. Two SCF calculations, referred as SCF 1 and SCF 2 with the contracted basis of (9s5p1d) / [4s2p1d] and ( 13s8p4d) / [7s4p4d] respectively, have been carried out. A Green's function calculation based on the SCF 1 wavefunction has also been performed. The measured binding energy spectra from 11.5 to 55 eV are compared with the results of one-particle Green's function calculations for the ionization energies and their corresponding pole strenghts. The measured spherically averaged momentum distributions for the valence orbitals are quantitatively compared with theoretical calculations using the two SCF wavefunctions. In general, the SCF wavefunctions do not describe the experimental data very well, particularly in the low-momentum region. In the outer valence region there is a good agreeement between the calculated energies and pole strenghts and the measured ones. The 2é and 3á 1 in the inner valence region are strongly split due to electron correlation and ion relaxation effects. The Green's function calculation, using the 2ph Tamm-Dancoff or ADC (3) approximation, underestimated the splitting in the inner-valence region.

Weigold, E.; Zheng, Y.; von Niessen, W.

1994-06-01

30

Removal of Boron from Silicon by Solvent Refining Using Ferrosilicon Alloys  

NASA Astrophysics Data System (ADS)

The distribution of boron between purified solid silicon and iron-silicon melt was evaluated to investigate the possibility of boron removal from silicon by solvent refining with iron-silicon alloys. The distribution coefficient, defined as the ratio of the mole fraction of boron in solid to that of liquid, was found to be strongly dependent on boron concentration. Solvent refining at lower temperatures resulted in smaller distribution coefficient values. The boron removal percentages for the lowest boron concentration examined in this study were 70 pct [1583 K (1310 °C)], 65 pct [1533 K (1260 °C)], and 65 pct [1483 K (1210 °C)]. The values obtained for interaction parameter of boron on iron in solid silicon are as follows: -813 ± 53 [1583 K (1310 °C)], -830 ± 92 [1533 K (1260 °C)], -863 ± 91 [1483 K (1210 °C)]. Lower temperature resulted in smaller distribution coefficient and higher silicon yield.

Khajavi, Leili Tafaghodi; Morita, Kazuki; Yoshikawa, Takeshi; Barati, Mansoor

2014-11-01

31

Low Critical Concentration of Metal--Insulator Transition of Vanadium Doped Amorphous Boron  

Microsoft Academic Search

The metal--insulator transition (MIT) of V- and Zr-doped amorphous boron films (VxB100-x, ZrxB100-x) was studied. The temperature dependences of the electrical conductivity, the X-ray diffraction patterns and the X-ray absorption fine structures were measured for the samples. The compositional boundary of the metal--insulator transition is found between x = 2.9 and 3.7 in VxB100-x, and between x = 11 and

Kenji Tanabe; Kohei Soga; Shizuka Hosoi; Kazuaki Osumi; Hideshi Yamaguchi; Tomoya Uruga; Kaoru Kimura

2011-01-01

32

A heterogeneous boron distribution in soil influences the poplar root system architecture development  

NASA Astrophysics Data System (ADS)

Poplars are well suited for the phytomanagement of boron (B)-contaminated sites, due to their high transpiration rate and tolerance to elevated soil B concentrations. However, the uptake and the fate of B in poplar stands are not well understood. This information is crucial to improve the design of phytomanagement systems, where the primary role of poplars is to reduce B leaching by reducing the water flux through the contaminated material. Like other trace elements, B occurs heterogeneously in soils. Concentrations can differ up to an order of magnitude within centimetres. These gradients affect plant root growth and thus via preferential flow along the roots water and mass transport in soils to ground and surface waters. Generally there are three possible reactions of plant roots to patches with elevated trace element concentrations in soils: indifference, avoidance, or foraging. While avoidance or indifference might seem to be the most obvious strategies, foraging cannot be excluded a priori, because of the high demand of poplars for B compared to other tree species. We aimed to determine the rooting strategies of poplars in soils where B is either homo- or heterogeneously distributed. We planted 5 cm cuttings of Populus tremula var. Birmensdorf clones in aluminum (Al) containers with internal dimensions of 64 x 67 x 1.2 cm. The soil used was subsoil from northern Switzerland with a naturally low B and organic C concentration. We setup two treatments and a control with three replicates each. We spiked a bigger and a smaller portion of the soil with the same amount of B(OH)3-salt, in order to obtain soil concentrations of 7.5 mg B kg-1 and 20 mg B kg-1. We filled the containers with (a) un-spiked soil, (b) the 7.5 mg B kg-1 soil and (c) heterogeneously. The heterogeneous treatment consisted of one third 20 mg B kg-1 soil and two thirds control soil. We grew the poplars in a small greenhouse over 2 months and from then on in a climate chamber for another 3 months. We irrigated the poplars with modified Hoagland's solution that contained no B. We imaged the roots in the soil every 3rd week using neutron radiography (NR) at the Paul-Scherrer Institute. Living roots can be visualised in soil by NR because of their higher water content compared to the surrounding soil. At the end of the growing period, the Al containers were opened and the soil surface was scanned by a standard office scanner. The soil in the containers was divided into nine equal portions representing different depths and spiked or un-spiked regions in soil profile. We separated roots and soil as well as the aerial parts (stems and leaves). We obtained data on root morphological parameters like root length and root density by evaluating scans of the washed root samples with an image evaluation software. All soil and plant samples were dried, weighed and analyzed for B and mineral nutrients using ICP-OES. Plant vitality parameters like water use, growth and number of living leaves did not show any reaction to the treatments. The oldest poplar leaves from poplars in the B-spiked treatments showed signs of light to serious necrosis. From the neutron radiographs it was apparent that poplar roots reached the walls of the Al- containers during the experiment. Primary roots grew at first strongly in lengths in horizontal as well as in vertical direction and only after this lateral root growth was visible. Although the filling and packing of the containers was done with great care to establish an ideally homogeneous soil profile settlement occurred in some containers resulting in gaps in the profile. However, roots growth did not seem to be deranged since roots simply crossed these gaps and continued growth in the adjacent soil patch. The complete results will be available at the time of the conference.

Rees, R.; Robinson, B. H.; Hartmann, S.; Lehmann, E.; Schulin, R.

2009-04-01

33

Central fitting distributions and extreme value distributions for prediction of high PM10 concentration  

Microsoft Academic Search

Central fitting distribution such as lognormal distribution can give a good result for fitting the mean concentration of air pollutants data. However, many researches find that it cannot precisely fit the high concentration region. Therefore, this research compares central fitting distribution (cfd) that is the lognormal distribution with the extreme value distributions (evd) that are Frechet and Gumbel distribution to

Noor Faizah Fitri Mdyusof; Nor Azam Ramli; Ahmad Shukri Yahaya; Nurulilyana Sansuddin; Nurul Adyani Ghazali; Wesam Ahmed Al Madhoun

2011-01-01

34

The use of boron for thermochemical storage and distribution of solar energy  

Microsoft Academic Search

Boron has been proposed as a candidate for hydrogen production. In this study a process is described in which boron is used as a means to store and transport solar energy from a production site to motor vehicles, where it is used to generate hydrogen and heat. The proposed multi-step fuel cycle includes no carbon as a reducing agent and,

Tareq Abu-Hamed; Jacob Karni; Michael Epstein

2007-01-01

35

Salinity's influence on boron toxicity in broccoli: I. Impacts on yield, biomass distribution, and water use  

Technology Transfer Automated Retrieval System (TEKTRAN)

Research addressing the interactive effects of the dual plant stress factors, excess boron and salinity, on crop productivity has expanded considerably over the past few years. The purpose of this research was to determine and quantify the interactive effects of salinity, saltcomposition and boron ...

36

Monte Carlo simulation of depth dose distribution in several organic models for boron neutron capture therapy  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations are performed to evaluate depth-dose distributions for possible treatment of cancers by boron neutron capture therapy (BNCT). The ICRU computational model of ADAM & EVA was used as a phantom to simulate tumors at a depth of 5 cm in central regions of the lungs, liver and pancreas. Tumors of the prostate and osteosarcoma were also centered at the depth of 4.5 and 2.5 cm in the phantom models. The epithermal neutron beam from a research reactor was the primary neutron source for the MCNP calculation of the depth-dose distributions in those cancer models. For brain tumor irradiations, the whole-body dose was also evaluated. The MCNP simulations suggested that a lethal dose of 50 Gy to the tumors can be achieved without reaching the tolerance dose of 25 Gy to normal tissue. The whole-body phantom calculations also showed that the BNCT could be applied for brain tumors without significant damage to whole-body organs.

Matsumoto, T.

2007-09-01

37

EELS measurements of boron concentration profiles in p-a-Si and nip a-Si solar cells Bas B. Van Aken a,  

E-print Network

EELS measurements of boron concentration profiles in p-a-Si and nip a-Si solar cells Bas B. Van energy loss spectroscopy (EELS); Thin film Si; Transmission electron microscopy; p-Type SiC; Doping-loss EELS combined with numerical analysis. We control the band gap and activation energy of p

Dunin-Borkowski, Rafal E.

38

BORON CONCENTRATIONS REMAIN STABLE IN MILK FROM MOTHERS OF FULL-TERM EXCLUSIVELY BREAST-FED INFANTS DURING THE FIRST FOUR MONTHS OF LACTATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

To expand the finding from this laboratory that human milk boron (B) concentrations remain stable during the first 3 months of lactation, we analyzed archived milk collected (1980-84) from lactating mothers of full-term, exclusively breast-fed, infants living in Houston, TX. Samples were collected o...

39

Electrochemical treatment of reverse osmosis concentrate on boron-doped electrodes in undivided and divided cell configurations.  

PubMed

An undivided electrolytic cell may offer lower electrochlorination through reduction of chlorine/hypochlorite at the cathode. This study investigated the performance of electrooxidation of reverse osmosis concentrate using boron-doped diamond electrodes in membrane-divided and undivided cells. In both cell configurations, similar extents of chemical oxygen demand and dissolved organic carbon removal were obtained. Continuous formation of chlorinated organic compounds was observed regardless of the membrane presence. However, halogenation of the organic matter did not result in a corresponding increase in toxicity (Vibrio fischeri bioassay performed on extracted samples), with toxicity decreasing slightly until 10AhL(-1), and generally remaining near the initial baseline-toxicity equivalent concentration (TEQ) of the raw concentrate (i.e., ?2mgL(-1)). The exception was a high range toxicity measure in the undivided cell (i.e., TEQ=11mgL(-1) at 2.4AhL(-1)), which rapidly decreased to 4mgL(-1). The discrepancy between the halogenated organic matter and toxicity patterns may be a consequence of volatile and/or polar halogenated by-products formed in oxidation by OH electrogenerated at the anode. The undivided cell exhibited lower energy compared to the divided cell, 0.25kWhgCOD(-1) and 0.34kWhgCOD(-1), respectively, yet it did not demonstrate any improvement regarding by-products formation. PMID:25048621

Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Escher, Beate I; Joll, Cynthia; Radjenovic, Jelena

2014-08-30

40

Feasibility of boron neutron capture therapy (BNCT) for malignant pleural mesothelioma from a viewpoint of dose distribution analysis  

SciTech Connect

Purpose: To investigate the feasibility of boron neutron capture therapy (BNCT) for malignant pleural mesothelioma (MPM) from a viewpoint of dose distribution analysis using Simulation Environment for Radiotherapy Applications (SERA), a currently available BNCT treatment planning system. Methods and Materials: The BNCT treatment plans were constructed for 3 patients with MPM using the SERA system, with 2 opposed anterior-posterior beams. The {sup 1}B concentrations in the tumor and normal lung in this study were assumed to be 84 and 24 ppm, respectively, and were derived from data observed in clinical trials. The maximum, mean, and minimum doses to the tumors and the normal lung were assessed for each plan. The doses delivered to 5% and 95% of the tumor volume, D{sub 05} and D{sub 95}, were adopted as the representative dose for the maximum and minimum dose, respectively. Results: When the D{sub 05} to the normal ipsilateral lung was 5 Gy-Eq, the D{sub 95} and mean doses delivered to the normal lung were 2.2-3.6 and 3.5-4.2 Gy-Eq, respectively. The mean doses delivered to the tumors were 22.4-27.2 Gy-Eq. The D{sub 05} and D{sub 95} doses to the tumors were 9.6-15.0 and 31.5-39.5 Gy-Eq, respectively. Conclusions: From a viewpoint of the dose-distribution analysis, BNCT has the possibility to be a promising treatment for MPM patients who are inoperable because of age and other medical illnesses.

Suzuki, Minoru [Particle Oncology Research Center, Osaka (Japan)]. E-mail: msuzuki@rri.kyoto-u.ac.jp; Sakurai, Yoshinori [Division of Medical Physics, Department of Radiation Life Science, Research Reactor Institute, Kyoto University, Osaka (Japan); Masunaga, Shinichiro [Particle Oncology Research Center, Osaka (Japan); Kinashi, Yuko [Particle Oncology Research Center, Osaka (Japan); Nagata, Kenji [Particle Oncology Research Center, Osaka (Japan); Maruhashi, Akira [Division of Medical Physics, Department of Radiation Life Science, Research Reactor Institute, Kyoto University, Osaka (Japan); Ono, Koji [Particle Oncology Research Center, Osaka (Japan)

2006-12-01

41

Axial solid concentration distribution in tapered and cylindrical bubble columns  

Microsoft Academic Search

The distribution of axial solid concentration was investigated experimentally and theoretically in tapered and cylindrical slurry bubble columns using air as the gas phase, tap water as the liquid phase and quartz sands as the solid phase. Based on the sedimentation–dispersion model commonly used in cylindrical columns, a mathematical model was presented to predict the solid concentration distribution in the

Kai Zhang

2002-01-01

42

Computer simulation for the concentration distribution of the parabolic cylinder and paraboloid concentrators  

SciTech Connect

A computer simulation for the solar concentration distributions for parabolic cylinder and paraboloid concentrators was developed. The method represented in this work deals with the solar rays on an individual basis which is considered as an analogy to a microscopic approach to the concentration problem. The concept of concentration is related to the distribution of the solar rays, photon, at the focal planes of the concentrators. A mathematical model was developed to simulate the concentration process of the solar rays with its three main patterns: the falling solar rays and their distribution across the solar disk, the reflection of the rays over the concentrator surface, and the reception of the concentrated rays at the concentrator focal plane. A three-dimensional ray trace analysis was used with the resulting sets of vectors equations solved by the computer. Several checks for the method developed with the available results are also given. An analysis was performed for the concentration distributions of the parabolic cylinder concentrators for the perfect shaded and unshaded conditions. For the paraboloid concentrators, the case of perfect concentration under a non-uniform sun was treated. Also a full analysis of the off-focus concentration was made.

El-Haggan, A.M.

1984-01-01

43

Macroscopic geometric heterogeneity effects in radiation dose distribution analysis for boron neutron capture therapy  

SciTech Connect

Calculations of radiation flux and dose distributions for boron neutron capture therapy (BNCT) of brain tumors are typically performed using sophisticated three-dimensional analytical models based on either a homogeneous approximation or a simplified few-region approximation to the actual highly heterogeneous geometry of the irradiation volume. Such models should be validated by comparison with calculations using detailed models in which all significant macroscopic tissue heterogeneities and geometric structures are explicitly represented as faithfully as possible. This paper describes such a validation exercise for BNCT of canine brain tumors. Geometric measurements of the canine anatomical structures of interest for this work were performed by dissecting and examining two essentially identical Labrador retriever heads. Chemical analyses of various tissue samples taken during the dissections were conducted to obtain measurements of elemental compositions for the tissues of interest. The resulting geometry and tissue composition data were then used to construct a detailed heterogeneous calculational model of the Labrador head. Calculations of three-dimensional radiation flux distributions pertinent to BNCT were performed for this model using the TORT discrete-ordinates radiation transport code. The calculations were repeated for a corresponding volume-weighted homogeneous-tissue model. Comparison of the results showed that peak neutron and photon flux magnitudes were quite similar for the two models (within 5%), but that the spatial flux profiles were shifted in the heterogeneous model such that the fluxes in some locations away from the peak differed from the corresponding fluxes in the homogeneous model by as much as 10%--20%. Differences of this magnitude can be therapeutically significant, emphasizing the need for proper validation of simplified treatment planning models.

Moran, J.M.; Nigg, D.W.; Wheeler, F.J.; Bauer, W.F. (Idaho National Engineering Laboratory, EG G Idaho, Inc., P.O. Box 1625, Idaho Falls, Idaho 83415-3515 (United States))

1992-05-01

44

Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.  

PubMed

Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7-11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L(-1) of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L(-1), yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH() in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L(-1)). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 ?M (tTHMs), and 12 and 22 ?M (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to avoid the formation of chlorinated by-products. PMID:22995242

Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

2012-11-15

45

Grain Boundary Segregation Behavior of Boron in Low-Alloy Steel  

NASA Astrophysics Data System (ADS)

The boron concentration profiles around prior austenite grain boundaries in Fe-0.05C-0.5Mo-0.001B (mass pct) are examined using aberration-corrected STEM-EELS. In order to obtain the precise distribution of boron around the boundaries, tilt series measurements with thin specimens (<30 nm) are performed and the EEL spectra are analyzed by principal component analysis (PCA) and multivariate curve resolution (MCR). The boron concentration profile changes with the cooling rate from the solid solution temperature. The concentration at grain boundaries is maximized at a medium rate (30 °C/s), where the concentration reaches 8 at. pct, and it decreases at a larger (250 °C/s) or smaller (5 °C/s) rate. On the other hand, the boron distribution becomes wider as the cooling rate becomes smaller. The current results suggest that the boron segregation in the alloy is formed by the "non-equilibrium segregation mechanism."

Shigesato, Genichi; Fujishiro, Taishi; Hara, Takuya

2014-04-01

46

Helium3 and boron-10 concentration and depth measurements in alloys and semiconductors using NDP  

Microsoft Academic Search

Neutron Depth Profiling (NDP) is a nondestructive near surface technique that is used to measure concentration versus absolute depth of several isotopes of light mass elements in various substrates. NDP is based on absorption reaction of thermal neutrons with the isotope of interest. Charged particles and recoil atoms are generated in the reaction. The depth profiles are determined by measuring

Kenan Ünlü; Mehmet Saglam; Bernard W Wehring

1999-01-01

47

Electron concentration distribution in a glow discharge in air flow  

NASA Astrophysics Data System (ADS)

Electron concentration distributions in a glow discharge in longitudinal and vortex air flows are determined from the attenuation of the electromagnetic wave passing through the plasma using microwave probes. An analysis of the distribution curves obtained indicates that electron concentration decreases in the direction of the anode. This can be explained by charge diffusion toward the chamber walls and electron recombination and sticking within the discharge.

Mukhamedzianov, R. B.; Gaisin, F. M.; Sabitov, R. A.

1989-04-01

48

Electron density distribution of bilayer nanographene and band structures of boron-carbon-nitride systems  

E-print Network

Bilayer graphene nanoribbon with zigzag edge is investigated with the tight binding model. Two stacking structures, alpha and beta, are considered. The band splitting is seen in the alpha structure, while the splitting in the wave number direction is found in the beta structure. The local density of states in the beta structure tend to avoid sites where interlayer hopping interactions are present. The calculation is extended to the boron-carbon-nitride systems. The qualitative properties persist when zigzag edge atoms are replaced with borons and nitrogens.

Harigaya, Kikuo

2011-01-01

49

Original article Effect of concentrate type and distribution method  

E-print Network

fermentation. dairy cow / fat content / concentrate / milk yield Résumé - Effet de la nature et des modalitésOriginal article Effect of concentrate type and distribution method on milk fat content and milk- ditions as treatment RW. Milk yield was higher (+ 2 kg/day) for PHM treatment than for the GW and RW

Boyer, Edmond

50

Boron Neutron Capture Therapy (BNCT) Dose Calculation using Geometrical Factors Spherical Interface for Glioblastoma Multiforme  

NASA Astrophysics Data System (ADS)

Boron Neutron Capture Therapy (BNCT) is a cancer therapy by utilizing thermal neutron to produce alpha particles and lithium nuclei. The superiority of BNCT is that the radiation effects could be limited only for the tumor cells. BNCT radiation dose depends on the distribution of boron in the tumor. Absorbed dose to the cells from the reaction 10B (n, ?) 7Li was calculated near interface medium containing boron and boron-free region. The method considers the contribution of the alpha particle and recoiled lithium particle to the absorbed dose and the variation of Linear Energy Transfer (LET) charged particles energy. Geometrical factor data of boron distribution for the spherical surface is used to calculate the energy absorbed in the tumor cells, brain and scalp for case Glioblastoma Multiforme. The result shows that the optimal dose in tumor is obtained for boron concentrations of 22.1 mg 10B/g blood.

Zasneda, Sabriani; Widita, Rena

2010-06-01

51

Passive aerosol sampler for particle concentrations and size distributions.  

PubMed

This research evaluated the UNC passive aerosol sampler as a tool to measure particle mass concentrations and size distributions. The exposure scenario represented high concentrations and exposure periods of a few hours. Mass concentrations measured with the passive sampler were compared to concentrations measured using both a dichotomous sampler and an aerodynamic particle sizer (APS). In addition, the size distributions measured with the passive sampler were compared to those measured using the APS. Mass concentrations measured using the dichotomous sampler and the APS agreed well. The passive sampler tracked, but tended to overestimate, mass concentrations measured by the other two instruments. Size distributions measured with the passive sampler followed the general pattern of those measured using the APS. Overall, the passive sampler demonstrated both its utility and its limitations in these tests. The concentration measurements and size distributions found using passive samplers were more variable than those of the other instruments, but generally followed the data taken using the other methods. The advantages of low cost and ease of use offset the limitations in data quality with the passive sampler; these advantages are particularly welcome for sampling situations where aerosol properties vary over space or time. PMID:18392275

Whitehead, Todd; Leith, David

2008-03-01

52

Quantum network teleportation for quantum information distribution and concentration  

NASA Astrophysics Data System (ADS)

We investigate the schemes of quantum network teleportation for quantum information distribution and concentration, which are essential in quantum cloud computation and the quantum internet. In those schemes, with the prior shared entanglement in the quantum network, the cloud can send simultaneously identical unknown quantum states to clients located in different places. Additionally, with the same entanglement resource, these clients can concentrate their states to the cloud to reconstruct the original state. The number of clients can be beyond the number of identical quantum states intentionally being sent; this quantum network teleportation can make sure that the quantum states' distribution is optimal in the sense that the fidelity achieves the upper bound. These schemes facilitate the quantum information distribution and concentration in quantum networks in the framework of quantum cloud computation. Potential applications in time synchronization and the photonic implementation of those schemes are discussed.

Zhang, Yong-Liang; Wang, Yi-Nan; Xiao, Xiang-Ru; Jing, Li; Mu, Liang-Zhu; Korepin, V. E.; Fan, Heng

2013-02-01

53

Turbulent Concentration of Chondrules: Size Distribution and Multifractal Scaling  

NASA Technical Reports Server (NTRS)

Size-selective concentration of particles in 3D turbulence may be related to collection of chondrules and other constituents into primitive bodies in a weakly turbulent protoplanetary nebula. In the terrestrial planet region, both the characteristic size and narrow size distribution of chondrules are explained, whereas "fluffier" particles would be concentrated in lower density, or more intensely turbulent, regions of the nebula. The spatial distribution of concentrated particle density obeys multifractal scaling, suggesting a dose tie to the turbulent cascade process. This scaling behavior allows predictions of the concentration probabilities to be made in the protoplanetary nebula, which are so large (> 10(exp 3) - 10(exp 4)) that further studies must be made of the role of mass loading.

Cuzzi, Jeffrey N.; Hogan, Robert C.; Paque, Julie M.; Dobrovolskis, Anthony R.

1999-01-01

54

Manipulation of in Vivo Sorbitol Production Alters Boron Uptake and Transport in Tobacco1  

PubMed Central

Recent evidence that some species can retranslocate boron as complexes with sugar alcohols in the phloem suggests a possible mechanism for enhancing boron efficiency. We investigated the relationship between sugar alcohol (sorbitol) content, boron uptake and distribution, and translocation of foliar-applied, isotopically enriched 10B in three lines of tobacco (Nicotiana tabacum) plants differing in sorbitol production. In tobacco line S11, transformed with sorbitol-6-phosphate dehydrogenase, the production of sorbitol was accompanied by an increase in the concentration of boron in plant tissues and an increased uptake of boron compared with either tobacco line A4, transformed with antisense orientation of sorbitol-6-phosphate dehydrogenase, or wild-type tobacco (line SR1, zero-sorbitol producer). Foliar application of 10B to mature leaves was translocated to the meristematic tissues only in line S11. These results demonstrate that the concentration of the boron-complexing sugar alcohol in the plant tissue has a significant effect on boron uptake and distribution in plants, whereas the translocation of the foliar-applied 10B from the mature leaves to the meristematic tissues verifies that boron is mobile in sorbitol-producing plants (S11) as we reported previously. This suggests that selection or transgenic generation of cultivars with an increased sugar alcohol content can result in increased boron uptake, with no apparent negative effects on short-term growth. PMID:9952470

Bellaloui, Nacer; Brown, Patrick H.; Dandekar, Abahaya M.

1999-01-01

55

Boron nitride: Composition, optical properties and mechanical behavior  

Microsoft Academic Search

A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds

John J. Pouch; Samuel A. Alterovitz; Kazuhisa Miyoshi; Joseph D. Warner

1987-01-01

56

Wall Temperature Dependence of Boronization Using Decaborane and Diborane  

Microsoft Academic Search

A new boronization technique based on pyrolysis of boron hydrides on hot walls was investigated in a laboratory experiment. The deposition rate of boron films through pyrolysis of decaborane was high enough to apply the pyrolysis to actual fusion devices bakable to 300°C. The hydrogen concentration of boron films prepared by the pyrolysis or conventional plasma-assisted boronization at various temperatures

Masashi Yamage; Takeshi Ejima; Masahiro Saidoh; Norio Ogiwara; Hideo Sugai

1993-01-01

57

CONCENTRATION DISTRIBUTIONS IN THE NEAR-WAKE OF A BUILDING  

EPA Science Inventory

A set of wind-tunnel data is presented which describes the concentration distributions resulting from diffusion of a passive tracer in the near-wake of a cubical building. ources were located near ground level both upstream and downstream of the building, and centered atop the bu...

58

Two-dimensional finite elements model for boron management in agroforestry sites.  

PubMed

Agroforesty systems, which are recommended as a management option to lower the shallow groundwater level and to reuse saline subsurface drainage waters from the tile-drained croplands in the drainage-impacted areas of Jan Joaquin Valley of California, have resulted in excessive boron buildup in the soil root zone. To assess the efficacy of the long-term impacts of soil boron buildup in agroforesty systems, a mathematical model was developed to simulate non-conservative boron transport. The developed dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction processes. The simulation of two different observed field data sets by the developed model is satisfactory, with mean absolute error of 1.5 mg/L and relative error of 6.5%. Application of the model to three different soils shows that boron adsorption is higher in silt loam soil than that in sandy loam and clay loam soils. This result agrees with the laboratory experimental observations. The results of the sensitivity analysis indicate that boron uptake by root-water extraction process influences the boron concentration distribution along the root zone. Also, absorption coefficient and maximum adsorptive capacity of a soil for boron are found to be sensitive parameters. PMID:19184495

Tayfur, Gokmen; Tanji, Kenneth K; Baba, Alper

2010-01-01

59

Distribution of airborne radon-222 concentrations in U. S. homes  

Microsoft Academic Search

Apparently large exposures of the general public to the radioactive decay products of radon-222 present in indoor air have led to systematical appraisal of monitoring data from U.S. single-family homes; several ways of aggregating data were used that take into account differences in sample selection and season of measurements. The resulting distribution of annual-average radon-222 concentrations can be characterized by

A. V. Nero; M. B. Schwehr; W. W. Nazaroff; K. L. Revzan

1986-01-01

60

Spatial distribution of the daily precipitation concentration index in Algeria  

NASA Astrophysics Data System (ADS)

In this paper, the spatial and temporal distribution of the daily precipitation concentration index (CI) in Algeria (South Mediterranean Sea) has been assessed. Forty-two daily rainfall series based on high quality and fairly regular rainfall records for the period from 1970 to 2008 were used. The daily precipitation concentration index results allowed identifying three climatic zones: the northern country, characterized by coastal regions with CI values between 0.59 and 0.63, the highlands, with values between 0.57 and 0.62 (average of 0.61), except for the area of Biskra (CI = 0.70), and the southern region of the country, with high rainfall concentrations, with values between 0.62 and 0.69. CI is an index related to the rainfall intensity and erosive capacity; therefore, this index has great interest for studies on torrential rainfall and floods.

Boucherf, D.; Benhamrouche, A.; Hamadache, R.; Bendahmane, L.; Martin-Vide, J.; Teixeira Nery, J.

2014-04-01

61

Saharan Dust Particle Size And Concentration Distribution In Central Ghana  

NASA Astrophysics Data System (ADS)

A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 ?m-25 ?m.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 ?g/m3 to 1344 ?g/m3 with an average of 532 ?g/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 ?m to 2.43 ?m with an average of 1.5 ?m ± 0.5. The particle size distributions exhibited the typical distribution pattern for atmospheric aerosols with a coarse mode diameter situated at about 3.5 ?m. The experimental results reported in this study will be important in validating satellite based observations and simulation models of the African dust plume towards the Gulf of Guinea during winter.

Sunnu, A. K.

2010-12-01

62

Halogenated sulfidohydroboranes for nuclear medicine and boron neutron capture therapy  

DOEpatents

A method for performing boron neutron capture therapy for the treatment of tumors is disclosed. The method includes administering to a patient an iodinated sulfidohydroborane, a boron-10-containing compound. The site of the tumor is localized by visualizing the increased concentration of the iodine labelled compound at the tumor. The targeted tumor is then irradiated with a beam of neutrons having an energy distribution effective for neutron capture. Destruction of the tumor occurs due to high LET particle irradiation of the tissue secondary to the incident neutrons being captured by the boron-10 nuclei. Iodinated sulfidohydroboranes are disclosed which are especially suitable for the method of the invention. In a preferred embodiment, a compound having the formula Na{sub 4}B{sub 12}I{sub 11}SSB{sub 12}I{sub 11}, or another pharmaceutically acceptable salt of the compound, may be administered to a cancer patient for boron neutron capture therapy. 1 fig.

Miura, M.; Slatkin, D.N.

1995-10-03

63

Distribution of indoor radon concentrations in Pennsylvania, 1990-2007  

USGS Publications Warehouse

Results from 548,507 indoor radon tests from a database compiled by the Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection, Radon Division, are evaluated in this report in an effort to determine areas where concentrations of radon are highest. Indoor radon concentrations were aggregated according to geologic unit and hydrogeologic setting for spatial analysis. Indoor radon concentrations greater than or equal to the U.S. Environmental Protection Agency (USEPA) action level of 4 picocuries per liter (pCi/L) were observed for 39 percent of the test results; the highest concentration was 1,866.4 pCi/L. When analyzed according to Pennsylvania’s geologic units, 93 of the 188 (49.5 percent) geologic units with indoor radon concentrations had median concentrations greater than the USEPA action level of 4 pCi/L; most of these geologic units are located in the eastern part of the State and include metamorphic rocks, limestones, sandstones, shales, and glacial deposits. When analyzed according to Pennsylvania’s hydrogeologic settings, 5 of the 20 (25 percent) settings had median indoor radon concentrations greater than the USEPA action level of 4 pCi/L; these settings are located mostly in the south-central part of the State. Median indoor radon concentrations aggregated according to geologic units and hydrogeologic settings are useful for drawing general conclusions about the occurrence of indoor radon in specific geologic units and hydrogeologic settings, but the associated data and maps have limitations. The aggregated indoor radon data have testing and spatial accuracy limitations due to lack of available information regarding testing conditions and the imprecision of geocoded test locations. In addition, the associated data describing geologic units and hydrogeologic settings have spatial and interpretation accuracy limitations, which are a result of using statewide data to define conditions at test locations and geologic data that represent a broad interpretation of geologic units across the State. As a result, indoor air radon concentration distributions are not proposed for use in predicting individual concentrations at specific sites nor for use as a decision-making tool for property owners to decide whether to test for indoor radon concentrations at specific property locations.

Gross, Eliza L.

2013-01-01

64

Vertical distribution of HOx concentrations driven by boundary layer dynamics  

NASA Astrophysics Data System (ADS)

The hydroxyl (OH) and hydroperoxy (HO2) radicals are key compounds for the degradation of pollutants in the atmosphere. Therefore, accurate and precise measurements of HOx radicals (= OH + HO2) at different altitudes and in different regions are necessary to test our understanding of atmospheric chemical processes. The planetary boundary layer (PBL) is of special interest as it is chemically the most active part of the atmosphere. Until today, there is a general lack of measurements investigating the distribution of radicals, trace gases, and aerosols in the PBL with high spatial resolution. Here, we present results of measurements performed in June/July 2012 in the Po valley region in Italy as part of the Pan-European Gas-AeroSOls-climate interaction Study (PEGASOS). A Zeppelin NT was used as an airborne platform for measurements of HOx radical concentrations and total OH reactivity (kOH) applying a remotely controlled Laser Induced Fluorescence (LIF) instrument. In addition a comprehensive set of other trace gases (O3, CO, NO, NO2, HCHO, HONO, VOCs), photolysis frequencies, particle number concentration, and meteorological parameters were measured. During the morning hours, a layered atmospheric structure with vertical gradients in trace gas concentrations was observed. In altitudes larger than 600 m above ground, air masses with low trace gas concentrations (NOx < 500 ppt, kOH < 3 s-1) were probed, whereas air masses in altitudes below 100 m above ground were influenced by ground emissions resulting in higher trace gas concentrations (NOx > 6 ppb, kOH > 6 s-1). The airship Zeppelin NT was used to perform localized height profiles between 75 and 900 m above ground in order to investigate the influence of these trace gas gradients on HOx radical concentrations. Due to changing chemical conditions, the measured OH concentration shows a variability with height up to a factor of 2.5 and for the measured HO2 concentration up to a factor of 5. Additionally, we present box model calculations of HOx to identify the processes driving the radical chemistry and its change in concentration with height.

Gomm, Sebastian; Broch, Sebastian; Fuchs, Hendrik; Hofzumahaus, Andreas; Holland, Frank; Bohn, Birger; Häseler, Rolf; Jäger, Julia; Kaiser, Jennifer; Keutsch, Frank; Li, Xin; Lu, Keding; Lohse, Insa; Rohrer, Franz; Tillmann, Ralf; Wegener, Robert; Wolfe, Glenn; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Wahner, Andreas

2014-05-01

65

Concentrations and size distributions of Antarctic stratospheric aerosols  

NASA Technical Reports Server (NTRS)

Particle Measuring Systems laser particle spectrometer (ASAS-X and FSSP) probes were used to measure aerosol particle concentrations and size distributions during 11 ER-2 flights between Punta Arenas (53 deg S) and Antarctica (up to 72 deg S) from August 17 to September 22, 1987. The time resolution was 10 s, corresponding to a spatial resolution of 2 km. The data were divided into two size classes (0.05-0.25 and 0.53-5.5 micron radius) to separate the small particle from the coarse particle populations. Results show that the small-particle concentrations are typical for a background aerosol during volcanic quiescence. This concentration is generally constant along a flight track; in only one instance a depletion of small particles during a polar stratospheric cloud (PSC) encounter was measured, suggesting a nucleation of type I PSC particles on background aerosols. Temporary increases of the coarse particle concentrations indicated the presence of tenuous polar stratospheric clouds that were encountered most frequently at the southernmost portion of a flight track and when the aircraft descended to lower altitudes. During 'particle events', particle modes were found at 0.6-micron radius, corresponding to type I PSCs, and occasionally, at 2.0-micron radius corresponding to type II PSCs.

Ferry, G. V.; Pueschel, R. F.; Neish, E.; Schultz, M.

1989-01-01

66

Intra-Fuel Cell Stack Measurements of Transient Concentration Distributions  

SciTech Connect

Intra-fuel-cell measurements are required to understand detailed fuel-cell chemistry and physics, validate models, optimize system design and control, and realize enhanced efficiency regimes; in comparison, conventional integrated fuel-cell supply and effluent measurements are fundamentally limited in value. Intra-reactor measurements are needed for all fuel cell types. This paper demonstrates the ability of a capillary-inlet mass spectrometer to resolve transient species distributions within operating polymer-electrolyte-membrane (PEM) fuel cells and at temperatures typical of solid-oxide fuel cells (SOFC). This is the first such demonstration of a diagnostic that is sufficiently minimally invasive as to allow measurements throughout an operating fuel cell stack. Measurements of transient water, hydrogen, oxygen and diluent concentration dynamics associated with fuel-cell load switching suggest oxygen-limited chemistry. Intra-PEM fuel cell measurements of oxygen distribution at various fuel-cell loads are used to demonstrate concentration gradients, non-uniformities, and anomalous fuel cell operation.

Partridge Jr, William P [ORNL; Toops, Todd J [ORNL; Green Jr, Johney Boyd [ORNL; Armstrong, Timothy R. [ORNL

2006-01-01

67

In vivo prompt gamma neutron activation analysis for the screening of boron-10 distribution in a rabbit knee: a simulation study  

NASA Astrophysics Data System (ADS)

Boron neutron capture synovectomy (BNCS) is under development as a potential treatment modality for rheumatoid arthritis (RA). RA is characterized by the inflammation of the synovium (the membrane lining articular joints), which leads to pain and a restricted range of motion. BNCS is a two-part procedure involving the injection of a boronated compound directly into the diseased joint followed by irradiation with a low-energy neutron beam. The neutron capture reactions taking place in the synovium deliver a local, high-linear energy transfer (LET) dose aimed at destroying the inflamed synovial membrane. For successful treatment via BNCS, a boron-labeled compound exhibiting both high synovial uptake and long retention time is necessary. Currently, the in vivo uptake behavior of potentially useful boronated compounds is evaluated in the knee joints of rabbits in which arthritis has been induced. This strategy involves the sacrifice and dissection of a large number of animals. An in vivo 10B screening approach is therefore under investigation with the goal of significantly reducing the number of animals needed for compound evaluation via dissection studies. The 'in vivo prompt gamma neutron activation analysis' (IVPGNAA) approach uses a narrow neutron beam to irradiate the knee from several angular positions following the intra-articular injection of a boronated compound whose uptake characteristics are unknown. A high-purity germanium detector collects the 478 keV gamma photons produced by the 10B capture reactions. The 10B distribution in the knee is then reconstructed by solving a system of simultaneous equations using a weighted least squares algorithm. To study the practical feasibility of IVPGNAA, simulation data were generated with the Monte Carlo N-particle transport code. The boron-containing region of a rabbit knee was partitioned into 8 compartments, and the 10B prompt gamma signals were tallied from 16 angular positions. Results demonstrate that for this level of spatial resolution, an estimate of 10B distribution inside the joint can be obtained to within 10% uncertainty, under ideal conditions. Variations of the anatomic dimensions among individual rabbit knees and potential knee positioning errors will result in an uncertainty of over 20%. IVPGNAA thus provides sufficient resolution and quantification regarding the in vivo uptake characteristics of boronated pharmaceuticals to serve as a useful means of screening new compounds of potential use in BNCS.

Zhu, X.; Clackdoyle, R.; Shortkroff, S.; Yanch, J.

2008-05-01

68

In vivo prompt gamma neutron activation analysis for the screening of boron-10 distribution in a rabbit knee: a simulation study.  

PubMed

Boron neutron capture synovectomy (BNCS) is under development as a potential treatment modality for rheumatoid arthritis (RA). RA is characterized by the inflammation of the synovium (the membrane lining articular joints), which leads to pain and a restricted range of motion. BNCS is a two-part procedure involving the injection of a boronated compound directly into the diseased joint followed by irradiation with a low-energy neutron beam. The neutron capture reactions taking place in the synovium deliver a local, high-linear energy transfer (LET) dose aimed at destroying the inflamed synovial membrane. For successful treatment via BNCS, a boron-labeled compound exhibiting both high synovial uptake and long retention time is necessary. Currently, the in vivo uptake behavior of potentially useful boronated compounds is evaluated in the knee joints of rabbits in which arthritis has been induced. This strategy involves the sacrifice and dissection of a large number of animals. An in vivo (10)B screening approach is therefore under investigation with the goal of significantly reducing the number of animals needed for compound evaluation via dissection studies. The 'in vivo prompt gamma neutron activation analysis' (IVPGNAA) approach uses a narrow neutron beam to irradiate the knee from several angular positions following the intra-articular injection of a boronated compound whose uptake characteristics are unknown. A high-purity germanium detector collects the 478 keV gamma photons produced by the (10)B capture reactions. The (10)B distribution in the knee is then reconstructed by solving a system of simultaneous equations using a weighted least squares algorithm. To study the practical feasibility of IVPGNAA, simulation data were generated with the Monte Carlo N-particle transport code. The boron-containing region of a rabbit knee was partitioned into 8 compartments, and the (10)B prompt gamma signals were tallied from 16 angular positions. Results demonstrate that for this level of spatial resolution, an estimate of (10)B distribution inside the joint can be obtained to within 10% uncertainty, under ideal conditions. Variations of the anatomic dimensions among individual rabbit knees and potential knee positioning errors will result in an uncertainty of over 20%. IVPGNAA thus provides sufficient resolution and quantification regarding the in vivo uptake characteristics of boronated pharmaceuticals to serve as a useful means of screening new compounds of potential use in BNCS. PMID:18445874

Zhu, X; Clackdoyle, R; Shortkroff, S; Yanch, J

2008-05-21

69

Effect of boron and gadolinium concentration on the calculated neutron multiplication factor of U(3)O/sub 2/ fuel pins in optimum geometries  

SciTech Connect

The KENO-Va improved Monte Carlo criticality program is used to calculate the neutron multiplication factor for TMI-U2 fuel compositions in a variety of configurations and to display parametric regions giving rise to maximum reactivity contributions. The lattice pitch of UO/sub 2/ fuel pins producing a maximum k/sub eff/ is determined as a function of boron concentrations in the coolant for infinite and finite systems. The characteristics of U/sub 3/O/sub 8/-coolant mixtures of interest to modeling the rubble region of the core are presented. Several disrupted core configurations are calculated and comparisons made. The results should be useful to proposed defueling of the TMI-U2 reactor.

Thomas, J.T.

1984-10-01

70

Wedge etching by anodic oxidation and determination of shallow boron profile by ion beam analysis  

NASA Astrophysics Data System (ADS)

Shallow boron implantation is a widely used step in the Si technology. Boron being a light element, standard RBS and channeling is hardly used for investigating its depth distribution and lattice location after implantation and subsequent annealing. An old idea, the pulled anodic oxidation is applied to create bevelled sample surface in order to explore the implanted boron profile. Detailed description of the special sample preparation method is given. RBS and channeling studies in combination with the 11B(p,?) 8Be nuclear reaction at around 660 keV were used to measure the total boron concentration step-by-step both on random direction and channeled samples. Boron profiles extracted from step-by-step nuclear reaction measurements is presented.

Gyulai, J.; Battistig, G.; Lohner, T.; Hajnal, Z.

2008-04-01

71

Silicon nanocrystals with high boron and phosphorus concentration hydrophilic shell—Raman scattering and X-ray photoelectron spectroscopic studies  

SciTech Connect

Boron (B) and phosphorus (P) codoped silicon (Si) nanocrystals, which exhibit very wide range tunable luminescence due to the donor to acceptor transitions and can be dispersed in polar liquids without organic ligands, are studied by Raman scattering and X-ray photoelectron spectroscopies. Codoped Si nanocrystals exhibit a Raman spectrum significantly different from those of intrinsic ones. First, the Raman peak energy is almost insensitive to the size and is very close to that of bulk Si crystal in the diameter range of 2.7 to 14?nm. Second, the peak is much broader than that of intrinsic ones. Furthermore, an additional broad peak, the intensity of which is about 20% of the main peak, appears around 650?cm{sup ?1}. The peak can be assigned to local vibrational modes of substitutional B and B-P pairs, B clusters, B-interstitial clusters, etc. in Si crystal. The Raman and X-ray photoelectron spectroscopic studies suggest that a crystalline shell heavily doped with these species is formed at the surface of a codoped Si nanocrystal and it induces the specific properties, i.e., hydrophilicity, high-stability in water, high resistance to hydrofluoric acid, etc.

Fujii, Minoru, E-mail: fujii@eedept.kobe-u.ac.jp; Sugimoto, Hiroshi; Hasegawa, Masataka; Imakita, Kenji [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501 (Japan)

2014-02-28

72

Silicon nanocrystals with high boron and phosphorus concentration hydrophilic shell—Raman scattering and X-ray photoelectron spectroscopic studies  

NASA Astrophysics Data System (ADS)

Boron (B) and phosphorus (P) codoped silicon (Si) nanocrystals, which exhibit very wide range tunable luminescence due to the donor to acceptor transitions and can be dispersed in polar liquids without organic ligands, are studied by Raman scattering and X-ray photoelectron spectroscopies. Codoped Si nanocrystals exhibit a Raman spectrum significantly different from those of intrinsic ones. First, the Raman peak energy is almost insensitive to the size and is very close to that of bulk Si crystal in the diameter range of 2.7 to 14 nm. Second, the peak is much broader than that of intrinsic ones. Furthermore, an additional broad peak, the intensity of which is about 20% of the main peak, appears around 650 cm-1. The peak can be assigned to local vibrational modes of substitutional B and B-P pairs, B clusters, B-interstitial clusters, etc. in Si crystal. The Raman and X-ray photoelectron spectroscopic studies suggest that a crystalline shell heavily doped with these species is formed at the surface of a codoped Si nanocrystal and it induces the specific properties, i.e., hydrophilicity, high-stability in water, high resistance to hydrofluoric acid, etc.

Fujii, Minoru; Sugimoto, Hiroshi; Hasegawa, Masataka; Imakita, Kenji

2014-02-01

73

Minimum inhibitory concentration distribution in environmental Legionella spp. isolates.  

PubMed

In Greece standard tests are performed in the watering and cooling systems of hotels' units either as part of the surveillance scheme or following human infection. The purpose of this study was to establish the minimum inhibitory concentration (MIC) distributions of environmental Legionella isolates for six antimicrobials commonly used for the treatment of Legionella infections, by MIC-test methodology. Water samples were collected from 2004 to 2011 from 124 hotels from the four prefectures of Crete (Greece). Sixty-eight (68) Legionella isolates, comprising L. pneumophila serogroups 1, 2, 3, 5, 6, 8, 12, 13, 15, L. anisa, L. rubrilucens, L. maceachernii, L. quinlivanii, L. oakridgensis, and L. taurinensis, were included in the study. MIC-tests were performed on buffered charcoal yeast extract with ?-ketoglutarate, L-cysteine, and ferric pyrophosphate. The MICs were read after 2 days of incubation at 36 ± 1 °C at 2.5% CO2. A large distribution in MICs was recorded for each species and each antibiotic tested. Rifampicin proved to be the most potent antibiotic regardless of the Legionella spp.; tetracycline appeared to have the least activity on our environmental isolates. The MIC-test approach is an easy, although not so cost-effective, way to determine MICs in Legionella spp. These data should be kept in mind especially since these Legionella species may cause human disease. PMID:25473976

Sandalakis, Vassilios; Chochlakis, Dimosthenis; Goniotakis, Ioannis; Tselentis, Yannis; Psaroulaki, Anna

2014-12-01

74

GROWTH RESPONSE AND SELENIUM AND BORON DISTRIBUTION IN BROCCOLI VARIETIES IRRIGATED WITH POOR QUALITY WATER.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Many drainage waters can be used successfully to grow selected crops without long-term consequences to crops and soils. Certain ions in saline waters can be specifically toxic to plants, if they accumulate to toxic concentrations within the plants tissues. Of particular concern in the San Joaquin ...

75

Liposomes as drug delivery vehicles for boron agents.  

PubMed

The successful treatment of cancer by boron neutron capture therapy (BNCT) requires the selective concentration of boron-10 within malignant tumors. The potential of liposomes to deliver boron-rich compounds to tumors has been assessed by examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. Alternatively, lipophilic boron-containing species have been embedded within the phospholipid bilayer of liposomes, and both hydrophilic and lipophilic boron compounds have been incorporated within the same liposome formulation. The biodistribution of boron was determined at several time points over 48 hr after i.v. injection of liposomal suspensions in BALB/c mice bearing EMT6 tumors. The tumor-selective delivery of boron by the liposomes was demonstrated as tumor-boron concentrations increased for several hours post-injection. Even at the low injected doses employed (6-18 mg boron/kg body weight) therapeutic tumor boron concentrations were observed (> 30 micrograms boron/g tissue) and high tumor/blood ratios were achieved (> 5). The most favorable results were obtained with the polyhedral borane Na3[a2-B20H1-NH2CH2CH2NH2]. Liposomes encapsulating this species produced a tumor boron concentration of 45 micrograms/g tissue at 30 hr post-injection, at which time the tumor/blood boron ratio was 9.3. PMID:9151223

Hawthorne, M F; Shelly, K

1997-05-01

76

The implementation of a DSSSD in the upgraded boron analysis at LIBAF for applications in geochemistry  

NASA Astrophysics Data System (ADS)

Interest in high spatial resolution boron analyses from a geochemical perspective is related to the recognition of boron as an important tracer of chemical recycling in the Earth, due to the high solubility of boron in aqueous fluids and silicate melts. Although boron is not a nominal component in common silicates they may still contain significant B-concentrations and hence constitute important boron reservoirs in the deeper parts of the Earth. Boron analyses have been performed at the Lund Ion Beam Analytical Facility for almost 20 years. For the analysis the nuclear reaction p+11B is used with beam energy just below 700 keV where the reaction has a broad resonance. In this paper we describe an upgrade of the system with a double sided silicon strip detector, which allows for much higher count rates compared to the old annular surface detector based system. A gain close to 20 in the data rate allows for high resolution mapping of boron distributions in crystals. This is illustrated by a number of examples. In addition, the detection limits for boron in geological samples are improved, now around 5 ppmw. In this work we address issues with data quality, especially charge normalization, lifetime correction and subtraction of different background components.

Kristiansson, P.; Borysiuk, M.; Hålenius, U.; Mosenfelder, J. L.; Ros, L.; Skogby, H.; Abdel, N.; Elfman, M.; Nilsson, E. J. C.; Pallon, J.

2014-08-01

77

Ground-state properties of boron-doped diamond  

SciTech Connect

Boron-doped diamond undergoes an insulator-metal or even a superconducting transition at some critical value of the dopant concentration. We study the equilibrium lattice parameter and bulk modulus of boron-doped diamond experimentally and in the framework of the density functional method for different levels of boron doping. We theoretically consider the possibility for the boron atoms to occupy both substitutional and interstitial positions and investigate their influence on the electronic structure of the material. The data suggest that boron softens the lattice, but softening due to substitutions of carbon with boron is much weaker than due to incorporation of boron into interstitial positions. Theoretical results obtained for substitution of carbon are in very good agreement with our experiment. We present a concentration dependence of the lattice parameter in boron-doped diamond, which can be used for to identify the levels of boron doping in future experiments.

Zarechnaya, E. Yu., E-mail: ezarechnaya@yahoo.com; Isaev, E. I. [Moscow State Institute of Steel and Alloys (Technological University) (Russian Federation)], E-mail: eyvaz_isaev@yahoo.com; Simak, S. I. [Linkoeping University, Department of Physics, Chemistry, and Biology (IFM) (Sweden); Vekilov, Yu. Kh. [Moscow State Institute of Steel and Alloys (Technological University) (Russian Federation); Dubrovinsky, L. S. [University of Bayreuth, Bayerisches Geoinstitut (Germany); Dubrovinskaia, N. A. [University of Heidelberg, Mineralogisches Institut (Germany); Abrikosov, I. A. [Linkoeping University, Department of Physics, Chemistry, and Biology (IFM) (Sweden)

2008-04-15

78

Electron energy distributions, vibrational population distributions, and negative-ion concentrations in hydrogen discharges  

SciTech Connect

We consider the negative ion concentrations in hydrogen discharges caused by electron excitation and dissociative attachment processes. The principal formation and destruction processes are discussed for electron densities in the range 10/sup 8/ to 10/sup 13/ electrons cm/sup -3/. Expressions are developed for calculating the high energy portion of the electron energy distribution in the discharge; using these energy distributions the electron excitation rates are evaluated. At low densities, the vibrational distribution arises from singlet electronic excitations and triplet excitations through the /sup 3/..pi../sub u/ state, in equilibrium with wall de-excitation processes. At high densities singlet excitations predominate in equilibrium with atom-molecule de-excitation processes. Possibilities for negative ion generation in a two-chamber tandem system are discussed in which the vibrational excitation occurs in a high power, high electron temperature discharge, kT/sub e/ = 5 eV, and dissociative attachment occurs in a low temperature kT/sub e/ = 1 eV, plasma chamber.

Hiskes, J.R.; Karo, A.M.

1982-06-28

79

Silica and boron-containing ultraphosphate laser glass with low concentration quenching and improved thermal shock resistance  

DOEpatents

Neodymium-doped phosphate glasses having a refractive index, nd>1.520; an Abbe number, Vd, <60; a density <3.0 g/cm.sup.3, a thermal expansion coefficient, .alpha., .ltoreq.110.times.10.sup.-7 .degree.C..sup.-1 ; a Young's Modulus, E, <70.times.10.sup.3 N/mm.sup.2 ; a Poisson's Ratio, .nu., <0.28; a thermal conductivity, K, >0.5 W/m.multidot.K, a thermal FOM=(1-.nu.).multidot.K/.alpha.E>0.7, consisting essentially of, in mol. %: P.sub.2 O.sub.5 : 40-70% SiO.sub.2 : 0-20% B.sub.2 O.sub.3 : 5-20% Sum SiO.sub.2 +B.sub.2 O.sub.3 : 5-35% Sum Li.sub.2 O+Na.sub.2 O+K.sub.2 O: 5-20% Sum La.sub.2 O.sub.3 +Nd.sub.2 O.sub.3 : 3-10% Sum MgO+CaO+SrO+BaO+ZnO: 0-10% and preferably containing an amount of Nd.sub.2 O.sub.3 effective for laser activity having an emission cross-section, .sigma., >3.5.times.10.sup.-20 cm.sup.2 ; a fluorescence linewidth (.DELTA..lambda..sub.f1)<23.5 nm; a first e-folding time of the Nd.sup.3+ fluorescence at 0.5 wt. % Nd.sub.2 O.sub.3 >375 .mu.sec, and a first e-folding time of the Nd.sup.3+ fluorescence at 10 wt. % >175 .mu.sec at 10 wt. %, have very low self-concentration quenching rates.

Cook, Lee M. (Duryea, PA); Stokowski, Stanley E. (Danville, CA)

1987-04-28

80

AN ANALYSIS OF LAND DISTRIBUTION AND CONCENTRATION IN BOLIVIA  

Microsoft Academic Search

Despite the implementation of Bolivia's land reform in 1953, the agrarian structure continues to have an extreme concentration of land. Furthermore, in the last two decades regional agrarian structure have been aggravated by population pressures and a lack of new technological practices for most small scale farmers and peasants. Public and private institutions and urban residents observe hundreds of landless

Fernando Crespo Valdivia

1991-01-01

81

Dust size distribution and concentrations with cottonseed oil mills  

E-print Network

. The vertical elutriator cotton dust sampler was designed to have an effective size cutoff at 15 um aerodynamic diameter. The cutoff diameter could be changed by changing the air flow through the instrument. A practical problem with size-selective samplers... cent and above 95 per cent cumulative mass were not entered for these calculations. This was because the Coulter Counter accurately measures particle diameters between 2 and 40 um with the 100 um aperture tube. 39 The particle size distribution...

Wiederhold, Lee Roy

2012-06-07

82

A Better Steam Engine: Designing a Distributed Concentrating Solar Combined Heat and Power System  

E-print Network

A Better Steam Engine: Designing a Distributed Concentrating Solar Combined Heat and Power System of analysis of Distributed Concentrating Solar Combined Heat and Power (DCS-CHP) systems is a design that is predicted to convert sunlight to heat at 8-10% solar-electric efficiency while simultaneously capturing ~60

California at Berkeley, University of

83

The effects of boron supplementation of layer diets varying in calcium and phosphorus concentrations on performance, egg quality, bone strength and mineral constituents of serum, bone and faeces.  

PubMed

Abstract 1. A 2 × 3 factorial arrangement of treatments was used to investigate the effects of dietary calcium (Ca), phosphorus (P), and supplemental boron (B) (0, 75, and 150 mg/kg) on the performance, egg quality, bone strength, and mineral constituents in bone, serum and faeces. 2. A reduction by 18% in the dietary Ca-P concentration from the recommended levels for the hen strain reduced (P < 0.01) faecal excretion of ash, Ca and P concentrations, and shear force with stress of the tibia in association with decreased feed intake, whereas improved albumen height and Haugh unit values in the egg. 3. Supplemental B significantly decreased the feed consumption, egg weight and final body weight in hens, as well as the albumen height, but had no effect on either the biomechanical characteristics of bones or the mineral profile of the bones and serum. However, there was a significant increase in the egg production rate and a reduction in the damaged and shell-less egg ratio, and in the feed conversion rate in hens fed adequate Ca-P with 150 mg/kg B compared to those of the unsupplemented controls. 4. The amount of B that accumulated in the bones and serum was correlated with the amount of B consumed. B increased the faecal excretion of ash, Ca and B. In general, dietary variables had no effect on mineral composition of serum and tibia. 5. The magnitude of the response to dietary B was much more pronounced in hens fed a diet deficient in Ca-P with 75 mg/kg B; these hens exhibited a production performance and an egg quality comparable to those given adequate Ca-P with no added B. 6. The data presented in this study describing the measured bone properties did not corroborate the hypothesis that B is a trace element playing an important role in mineral metabolism and bone strength through an interaction with Ca, P and Mg. PMID:25330040

Küçükyilmaz, K; Erkek, R; Bozkurt, M

2014-12-01

84

Frequency distributions of the concentrations of essential and nonessential elements in largemouth bass, Micropterus salmoides  

SciTech Connect

From data on elemental concentrations in human tissues, Liebscher and Smith (1968) hypothesized that the frequency distributions of concentrations for essential elements were normal distributions, whereas the frequency distributions for nonessential elements were lognormal distributions. Although Liebscher and Smith's justifications for this hypothesis are flawed, other researchers have reported similar observations. The concentrations of Cd, Ca, Cr, Co, Cu, Fe, Pb, Mn, Hg, K, Se, Na, and Zn were measured in the muscle, liver, and egg tissues of female largemouth bass to determine (1) to what extent the frequency distributions of elemental concentrations are affected by errors in measuring concentrations and (2) whether the previously observed differences between essential and nonessential elements could be demonstrated if we restricted our comparisons to only those elements whose concentrations can be accurately measured. Variance component analyses of elemental concentrations in muscle tissue indicated that variations among replicate tissue samples due to measuring errors were large relative to the variations among individual fish for Cd, Ca, Mn, K, and Na. For elements where variation among individuals was not obscured by errors in measuring concentrations, there were no apparent differences between the frequency distributions for the essential elements, Cr, Cu, Fe, Se, and Zn, and the distributions for the nonessential elements, Pb and Hg. The hypothesis of Liebscher and Smith was not supported by our data.

Pinder, J.E. III; Giesy, J.P.

1981-04-01

85

Sunshape and its influence on the flux distribution in imaging solar concentrators  

Microsoft Academic Search

Imaging solar concentrators, such as a parabolic dish, image the sun to their focal plane. Thus, the flux distribution is basically an image of the angular distribution of the direct incident solar radiation. This distribution, referred to as sunshape, is determined by solar limb darkening and by small angle scattering in the atmosphere. The authors present measurements of the sunshape

M. Schubnell

1992-01-01

86

Boron removal from geothermal waters by electrocoagulation.  

PubMed

Most of the geothermal waters in Turkey contain extremely high concentration of boron when they are used for irrigation. The use of geothermal waters for irrigation can results in excess amount deposition of boron in soil. On the other hand, a minimal boron concentration is required for irrigational waters. In this study, electrocoagulation (EC) was selected as a treatment process for the removal of boron from thermal waters obtained from Ilica-Erzurum in Turkey. Current density (CD), pH of solution and temperature of solution were selected as operational parameters. The results showed that boron removal efficiency increased from pH 4.0 to 8.0 and decreased at pH 10.0. Although boron removal efficiency was highest at pH 8.0, energy consumption was very high at this pH value compared to other pH intervals. Boron removal efficiency reached to 95% with increasing current density from 1.5 to 6.0 mA/cm(2), but energy consumption was also increased in this interval. At higher temperatures of solution, such as 313 and 333 K, boron removal efficiency increased. At optimum conditions, boron removal efficiency in geothermal water reached up to 95%. PMID:17904734

Yilmaz, A Erdem; Boncukcuo?lu, Recep; Kocakerim, M Muhtar; Yilmaz, M Tolga; Paluluo?lu, Cihan

2008-05-01

87

Development and Application of Watershed Regressions for Pesticides (WARP) for Estimating Atrazine Concentration Distributions in Streams  

USGS Publications Warehouse

Regression models were developed for predicting atrazine concentration distributions in rivers and streams, using the Watershed Regressions for Pesticides (WARP) methodology. Separate regression equations were derived for each of nine percentiles of the annual distribution of atrazine concentrations and for the annual time-weighted mean atrazine concentration. In addition, seasonal models were developed for two specific periods of the year--the high season, when the highest atrazine concentrations are expected in streams, and the low season, when concentrations are expected to be low or undetectable. Various nationally available watershed parameters were used as explanatory variables, including atrazine use intensity, soil characteristics, hydrologic parameters, climate and weather variables, land use, and agricultural management practices. Concentration data from 112 river and stream stations sampled as part of the U.S. Geological Survey's National Water-Quality Assessment and National Stream Quality Accounting Network Programs were used for computing the concentration percentiles and mean concentrations used as the response variables in regression models. Tobit regression methods, using maximum likelihood estimation, were used for developing the models because some of the concentration values used for the response variables were censored (reported as less than a detection threshold). Data from 26 stations not used for model development were used for model validation. The annual models accounted for 62 to 77 percent of the variability in concentrations among the 112 model development stations. Atrazine use intensity (the amount of atrazine used in the watershed divided by watershed area) was the most important explanatory variable in all models, but additional watershed parameters significantly increased the amount of variability explained by the models. Predicted concentrations from all 10 models were within a factor of 10 of the observed concentrations at most model development and model validation stations. Results for the two sets of seasonal models were similar. Concentration distributions derived from the seasonal-model predictions provided additional information compared to distributions derived from the annual models.

Larson, Steven J.; Crawford, Charles G.; Gilliom, Robert J.

2004-01-01

88

Decreasing the leachibility of boron wood preservatives  

E-print Network

the leachability of boron preservatives using water repellents. Southern pine (Pinus spp.) test samples were impregnated with several types and at different concentrations of borax/boric acid and PEG (Polyethylene glycol) mixture. Leachability performance...

Gezer, Engin Derya

2012-06-07

89

Boron doped nanostructured diamond films  

NASA Astrophysics Data System (ADS)

A chemical vapor deposition hydrogen/methane/nitrogen feed-gas mixture with unconventionally high methane (15% CH4 by volume) normally used to grow ultra-hard and smooth nanostructured diamond films on Ti-6Al-4V alloy substrates was modified to include diborane B2H6 for boron-doping of diamond films. The flow rates for B2H 6 and N2 were varied to investigate their effect on plasma chemistry, film structure, boron incorporation, and mechanical properties. It was found that boron atoms can easily be incorporated into diamond films and change the lattice constant and film structure. Nitrogen, on the other hand, competes with boron in the plasma and acts to prevent boron incorporation into the diamond structure. In addition, with the appropriate choice of deposition conditions, the film structure can be tailored to range from highly crystalline, well faceted diamond to nanocrystalline diamond. Glancing angle X-ray diffraction and Micro-Raman were used as the main tools to investigate the relation between processing and structure. An optimal N2/CH4 ratio of 0.4 was found to result in a film with a minimum in grain size and surface roughness, along with high boron incorporation (˜4 x 1020 cm-3). Mechanical properties and thermal stability of boron doped nanostructured diamond films were examined by means of nanoindentation, open air thermal annealing, and nanotribometry. It was found that the films have high hardness close to that of undoped nanostructured diamond films. Thermal stability of these films was evaluated by heating in an oxygen environment above 700°C. Improved thermal stability of boron doped nanostructured diamond films was observed. Tribological tests show that although both undoped and boron doped nanostructured diamond films show extremely low coefficient of friction and wear rate as compared with uncoated titanium alloys (Ti-6Al-4V) and cobalt chrome alloy (Co-Cr-Mo), a critical failure max stress of 2.2 GPa was observed for boron doped nanostructured diamond films. A FORTRAN Chemical Kinetics Package for the Analysis of Gas Phase Chemical Kinetics, gas-phase thermodynamic equilibrium calculations involving H 2/CH4/N2/B2H6 mixtures was employed to investigate the chemical interactions leading to boron incorporation and crystalline structure variations. The strong influence of the BH 3 in causing the boron incorporation and the role of CN radical in causing the nanocrystallinity are confirmed by the correlation of their modeled compositions in the gas phase with boron content and degree of nanocrystallinity as determined experimentally. A good degree of agreement was obtained between the theoretically predicted gas phase concentration of species and the experimental concentration trends as measured by the optical emission spectroscopy of the microwave plasma. Overall, high film hardness and toughness, combined with good thermal stability and low surface roughness, indicate that nanostructured boron doped diamond films can be used as wear resistant coatings that are able to withstand high temperature oxidizing environments.

Liang, Qi

90

Measurement of Particle Size Distribution and Volume Concentration based on Ultrasonic Attenuation Spectrum in Fat Emulsion  

NASA Astrophysics Data System (ADS)

The determination of particle size distribution in concentrated polydisperse fat emulsions measured by ultrasonic attenuation spectrum is studied in this paper. Based on theoretical analysis, ultrasonic attenuation spectrum of fat emulsion samples containing different droplet concentrations (1˜20%) is measured over the range of 2˜13MHz. Then the droplet size and distribution are determined by processing the experiment data with inversion arithmetic. The particle size distribution of original sample determined by ultrasonic spectrum gives excellent agreement with that of diluted sample measured by an optical instrument TSM(Totally Scattering Measurement). This indicates that ultrasonic spectrum is capable of determining the particle size distribution and dispersed-phase volume fraction of concentrated fat emulsions in a non-destructive approach.

Dong, Lili; Su, Mingxu; Xue, Minghua; Cai, Xiaoshu; Shang, Zhitao

2007-06-01

91

Boron stimulates embryonic trout growth.  

PubMed

Boron is present in our soil, water and air. Cyanobacteria require it for nitrogen fixation, and vascular plants require it for the formation of cell walls and membranes. I report here how boron affects the growth of embryonic rainbow trout (Oncorhynchus mykiss). Fertilized ovum from the Mt. Whitney rainbow trout strain were incubated at (12.5 degreesC) in Type 1 ASTM ultrapure grade water supplemented with boric acid (99.5% purity) during the 1995 and 1997 spawning seasons. Boron concentrations of the incubation solutions were determined by direct measurement using the curcumin procedure or inductively coupled plasma-mass spectrometry. In the 1995 study boron ranged from 1 to 936 micromol/L. Ca, Na and Mg salts were included in the incubation solutions to approximate concentrations in natural water. In the 1997 study fertilized eggs were incubated in ultrapure water supplemented with boric acid alone over a range from 2.2 to 90.6 micromol/L. The 1995 study used 144 embryos per B concentration and the 1997 study used 96 embryos per B concentration. Growth and teratogenicity were evaluated at the eye, hatch and 2-wk posthatch developmental stages. Boron stimulated growth in a dose-dependent manner in both studies (P < 0.001), and exposure was associated with an increase in B body concentration (P < 0.05). No teratogenic or microbicidal effects were apparent. These results are consistent with those expected of an element essential for vertebrate development. J. Nutr. 2488-2493, 128: 1998 PMID:9868197

Eckhert, C D

1998-12-01

92

Ecological risk assessment of a wetland exposed to boron  

SciTech Connect

A wetland located in the southeastern portion of the United States was the site of an investigation to determine the potential ecological risk of elevated boron concentrations to the flora and fauna living in the wetland. The conceptual model identified the vegetation as the primary receptor of concern, and thus the vegetation is the focus of this article. Samples of surface water, sediments, and selected vegetation were collected from the study wetland and several nearby reference sites and were analyzed for boron. Concentrations of boron in all three media exceeded reference site concentrations. Boron concentrations were highest near the suspected source but decreased almost to reference-site concentrations near the outer perimeter of the wetland. Some plants appeared stressed with yellowing and necrotic leaves; however, a correlation between tissue boron concentrations and the plant`s visual appearance was not apparent for all species studied. Modeling of the fate of boron indicated that the wetland has likely been at a steady state for many years and that boron concentrations were not expected to increase. It was concluded that no observable adverse ecological impacts to the vegetation could be attributed to boron, nor is it likely that the boron poses an unacceptable risk to the surrounding areas.

Powell, R.L.; Kimerle, R.A.; Coyle, G.T. [Monsanto Co., St. Louis, MO (United States). Environmental Sciences Center; Best, G.R. [Univ. of Florida, Gainesville, FL (United States)

1997-11-01

93

Correlation between threshold voltage and channel dopant concentration in negative-type metal-oxide-semiconductor field-effect transistors studied by atom probe tomography  

NASA Astrophysics Data System (ADS)

The correlation between threshold voltage (VT) and channel boron concentration in silicon-based 65 nm node negative-type metal-oxide-semiconductor field-effect transistors was studied by atom probe tomography (APT). VT values were determined for one million transistors in a single chip, and transistors having a ±4? deviation from the median VT were analyzed using APT. VT and the channel boron concentration were positively correlated. This is consistent with the relationship between the average boron concentration of wafers implanted with different channel doses and the median VT of the million transistors. APT is suitable for the study of dopant-distribution-based device failure mechanisms.

Takamizawa, H.; Shimizu, Y.; Inoue, K.; Toyama, T.; Yano, F.; Nishida, A.; Mogami, T.; Okada, N.; Kato, M.; Uchida, H.; Kitamoto, K.; Miyagi, T.; Kato, J.; Nagai, Y.

2012-06-01

94

Pressure-dependent boron isotopic fractionation observed by column chromatography  

NASA Astrophysics Data System (ADS)

Boron isotopic fractionation factor ( S ) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25°C, using 0.1 mmol/L boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at atmospheric pressure at 25°C with the boron concentration of 10 mmol/L, but were larger than the values at the same condition with much higher concentration of 100 and 501 mmol/L, indicating that borate-polymerization reducing the isotopic fractionation was negligible. However, calculations based on the theory of isotope distribution between two phases estimated that 21% (5MPa) and 47% (17MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)3-form, instead of in the four-coordinated B(OH)4--form, at high pressures even with the very diluted solution. We discussed this discrepancy by introducing (1) hydration or (2) a partial molar volume difference between isotopic molecules. It was inferred that borate ions were partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Alternatively, it was likely that the S value decreased with increasing pressure, because the difference of the partial isotopic molar volumes between 10B(OH)3 and 11B(OH)3 was larger than that between 10B(OH)4- and 11B(OH)4-. If either will be the case, the influence of a pressure upon the isotope effect may not be negligible for boron isotopic exchange equilibrium. This knowledge is crucial for the principle of the boron isotopic pH-metry reconstructing a chemical variation at the paleo-deep oceanic environment where the early life may have been evolved.

Musashi, M.; Oi, T.; Matsuo, M.; Nomura, M.

2007-12-01

95

Performance evaluation of two-dimensional compound elliptic lens concentrators using a yearly distributed insolation model  

Microsoft Academic Search

Optical performance of a two-dimensional compound elliptic lens (2D-CEL) for a photovoltaic static concentrator module has been studied as a function of half-acceptance angle using an yearly distributed insolation model. The maximum yearly averaged optical concentration ratio of 1.75 was obtained for global radiation when the 2D-CEL was installed at a tilt angle equal to the latitude of Tokyo (N35°).

K. Yoshioka; A. Suzuki; T. Saitoh

1999-01-01

96

Spatial distribution of soil organic carbon concentrations in grassland of Ireland  

Microsoft Academic Search

Soil organic C (SOC) concentrations in topsoil samples taken at 678 sites in the grassland of Ireland were investigated using statistics and geostatistics. SOC concentrations (Walkley–Black method) follow a lognormal distribution, with a median and geometric mean of 5.0%, and an arithmetic mean of 5.3%. Statistically significant (P<0.01) positive correlation between SOC and silt-plus-clay, and negative correlation between SOC and

David McGrath; Chaosheng Zhang

2003-01-01

97

Drop size distribution in highly concentrated liquid-liquid dispersions using a light back scattering method  

Microsoft Academic Search

New data are presented on drop size distribution at high dispersed phase fractions of organic- in-water mixtures, obtained with a light back scattering technique (3 Dimensional Optical Reflectance Measurement technique, 3D ORM). The 3D ORM technique, which provides fast, in-situ and on-line drop distribution measurements even at high concentrations of the dispersed phase, is validated using an endoscope attached to

J Lovick; AA Mouza; SV Paras; GJ Lye; P Angeli

2005-01-01

98

Wall Temperature Dependence of Boronization Using Decaborane and Diborane  

NASA Astrophysics Data System (ADS)

A new boronization technique based on pyrolysis of boron hydrides on hot walls was investigated in a laboratory experiment. The deposition rate of boron films through pyrolysis of decaborane was high enough to apply the pyrolysis to actual fusion devices bakable to 300°C. The hydrogen concentration of boron films prepared by the pyrolysis or conventional plasma-assisted boronization at various temperatures was measured with 15N nuclear reaction and/or IR absorption methods. The hydrogen content markedly decreased with increasing wall temperature, where decaborane always gives higher H content than diborane. Oxygen gettering and hydrogen recycling in a boronized vessel were evaluated by pulsed glow discharge in O2/He and D2, respectively. The results were compared between the pyrolysis and the plasma-based boronizations in decaborane or diborane at various wall temperatures.

Yamage, Masashi; Ejima, Takeshi; Saidoh, Masahiro; Ogiwara, Norio; Sugai, Hideo

1993-09-01

99

Investigations on boron levels in drinking water sources in China.  

PubMed

To evaluate boron contamination of public drinking water in China, both dissolved and total boron contents in 98 public drinking water sources from 49 cities, 42 brands of bottled water samples from supermarkets in several cities, and 58 water samples from boron industrial area were measured by inductively coupled plasma-mass spectrometry (ICP-MS). Our experimental results showed that boron existed in public drinking water sources mainly in dissolved status with total concentrations ranging from 0.003 to 0.337 mg/L (mean = 0.046 mg/L). The mean boron concentrations in mineral and pure bottled water were 0.052 and 0.028 mg/L, respectively. The results obtained in this work showed that there was no health risk on view of boron in public drinking water sources and bottled water. In boron industrial area, boron concentrations in surface water and ground water were 1.28 mg/L (range = 0.007-3.8 mg/L) and 18.3 mg/L (range = 0.015-140 mg/L), respectively, which indicated that boron industry caused boron pollution in local water system. PMID:19444639

Xu, Ren-ji; Xing, Xiao-ru; Zhou, Qun-fang; Jiang, Gui-bin; Wei, Fu-sheng

2010-06-01

100

Angular Distributions of Deuterons from (p, d) Reactions in Light Nuclei. II. Lithium, Beryllium, Boron, Fluorine, and Aluminum  

Microsoft Academic Search

Angular distributions of deuteron groups resulting from the bombardment of various elements with ~18-Mev protons have been observed. Angular distributions for reactions leading to the following final nuclei were studied: Li6, Li6* (2.2 Mev), Be8, B9, B9* (2.4 Mev), B10, F18, Al26. The observed data are fitted to theoretical (Butler) curves and in all cases, except F18 and Al26, ln

J. B. Reynolds; K. G. Standing

1956-01-01

101

The effect of concentrator field layout on the performance of point-focus distributed receiver systems  

NASA Technical Reports Server (NTRS)

The effect of concentrator field layout on the technical-economic performance of a point-focusing distributed receiver (PFDR) solar thermal power plant is presented. The plant design is based on the small community prototype system currently under development for JPL/DOE; parabolic dish concentrators are employed, and small heat engines are used to generate electricity at each dish. The effect of field size, array proportions, dish-to-dish spacing and packing fraction (concentrator-land area ratio) are presented for typical PFDR layouts. Economic analyses are carried out to determine optimum packing fraction as a function of site cost.

Pons, R. L.; Dugan, A. F.

1984-01-01

102

Impurity behavior in boronized Heliotron E  

NASA Astrophysics Data System (ADS)

Changes of impurity behavior and plasma performances by a boronization were investigated in Heliotron E. A 2.45 GHz ECH boronization with helium and decaborane at B=0.046 T was developed. The concentration of H/B atomic ratio in the deposited boron layer was much smaller than that of conventional dc glow discharges and the typical value was 0.1. The light impurity, oxygen and carbon, decreased drastically, but the reduction of the metallic impurity, iron and chromium, was not observed. A small H/B atomic ratio and low levels in the light impurity provided high ion temperature and low density plasma by neutral beam injectin heating.

Kondo, K.; Mizuuchi, T.; Sahara, A.; Sano, F.; Zushi, H.; Besshou, S.; Okada, H.; Nagasaki, K.; Kurimoto, Y.; Takada, H.; Nakayama, T.; Ogata, K.; Shirai, T.; Sugai, H.; Yamage, M.; Wakatani, M.; Obiki, T.

1995-04-01

103

Ni doping of semiconducting boron carbide  

NASA Astrophysics Data System (ADS)

The wide band gap, temperature stability, high resistivity, and robustness of semiconducting boron carbide make it an attractive material for device applications. Undoped boron carbide is p type; Ni acts as a n-type dopant. Here we present the results of controlled doping of boron carbide with Ni on thin film samples grown using plasma enhanced chemical vapor deposition. The change in the dopant concentration within the thin film as a function of the dopant flow rate in the precursor gas mixture was confirmed by x-ray photoelectron spectroscopy measurements; with increasing dopant concentration, current-voltage (I-V) curves clearly establish the trend from p-type to n-type boron carbide.

Hong, Nina; Langell, M. A.; Liu, Jing; Kizilkaya, Orhan; Adenwalla, S.

2010-01-01

104

Boron strengthening in FeAl  

SciTech Connect

The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.

Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C. [Dartmouth Coll., Hanover, NH (United States). Thayer School of Engineering; Carleton, R.L.; George, E.P. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1998-11-01

105

Spatial distribution of livestock concentration areas and soil nutrients in pastures  

Technology Transfer Automated Retrieval System (TEKTRAN)

Livestock frequently congregate at feeders, shades, or other sites on pastures, which severely disturbs soil and vegetation leading to erosion and nutrient runoff. Our objective was to determine the extent and spatial distribution of soil nutrients in livestock concentration areas on pastures and qu...

106

ON THE PROPORTIONALITY OF FINE MASS CONCENTRATION AND EXTINCTION COEFFICIENT FOR BIMODAL SIZE DISTRIBUTIONS  

EPA Science Inventory

For a bimodal size distribution of ambient aerosol, an upper limit in particle size can be chosen for the fine aerosol fraction so that the extinction coefficient for light scattering and absorption is directly proportional to the fine mass concentration, with no dependence on th...

107

Effects of arsenic on concentration and distribution of nutrients in the fronds of the arsenic  

E-print Network

hyperaccumulator Pteris vittata L. Cong Tu1 , Lena Q. Ma) Soil and Water Science Department, University of Florida Pteris vittata was the first terrestrial plant known to hyperaccumulate arsenic (As). However hyperaccumulation; Nutrients; Concentration; Distribution; Pteris vittata L. 1. Introduction Arsenic (As

Ma, Lena

108

DETERMINATION OF IODINE CONCENTRATION AND DISTRIBUTION IN RAT THYROID FOLLICLES BY ELECTRON-PROBE MICROANALYSIS  

PubMed Central

The concentration and the distribution of iodine in various sized follicles of rat thyroid glands have been analyzed by electron-probe microanalysis. The results of the iodine analysis were grouped according to uncorrected lumen diameter size. No significant differences in iodine concentration were observed among the various size categories. When the results for all follicles from a given sample were pooled, the standard error of the mean was approximately 4%. Usually 40–50 follicles per animal were analyzed. The concentration of iodine ranged from 0.9 to 2.1% by weight among individual animals. Scanning pictures and step-scan analysis showed the iodine distribution to be quite uniform across the colloid area. Several techniques of sample preparation were used; they produced no significant differences in the iodine concentrations observed. Sodium concentration, also determined in all samples, was found to vary from 2 to 9% by weight. Because of the mobility of the sodium ion, its distribution was greatly affected by the method of sample preparation. The technique that best preserved the natural chemistry of the sample was that of freezing the tissue, sectioning, and then freeze-drying. PMID:5824060

Robison, William L.; Davis, David

1969-01-01

109

Impact of mixing interface dynamics on concentration distributions in heterogeneous porous media  

NASA Astrophysics Data System (ADS)

The dynamics of mixing interfaces control a range of important subsurface processes, including reactive transport, heat transfer, dispersion in multiphase flows, or chemical elements cycling in streams and catchments. Mass transfer and chemical reactions across these interfaces is expected to be strongly affected by their elongation and folding resulting from the spatial and temporal fluctuations of flow velocities in the subsurface. We propose a new modeling framework to quantify the impact of mixing interface dynamics on the concentration distribution, predicting its shape and rate of deformation as it progresses towards uniformity in the medium (Le Borgne et al., PRL, 2013). The concentration field is represented by a set of stretched lamellae whose rate of diffusive smoothing is locally enhanced by kinematic stretching. Based on the interplay between stretching, diffusion and aggregation, we derive analytical expressions for the concentration distribution, holding for all field heterogeneities, residence times, and Peclet numbers. The theory provides predictions of the temporal evolution of concentration moments, scalar dissipation rate and other mixing measures, quantifying the controls of structural heterogeneities on the dynamics of mixing interfaces and the associated concentration distributions.

Le Borgne, Tanguy; Dentz, Marco; Villermaux, Emmanuel

2014-05-01

110

Spatial concentration distribution model for short-range continuous gas leakage of small amount  

NASA Astrophysics Data System (ADS)

Passive infrared gas imaging systems have been utilized in the equipment leak detection and repair in chemical manufacturers and petroleum refineries. The detection performance mainly relates to the sensitivity of infrared detector, optical depth of gas, atmospheric transmission, wind speed, and so on. Based on our knowledge, the spatial concentration distribution of continuously leaking gas plays an important part in leak detection. Several computational model of gas diffusion were proposed by researchers, such as Gaussian model, BM model, Sutton model and FEM3 model. But these models focus on calculating a large scale gas concentration distribution for a great amount of gas leaks above over 100- meter height, and not applicable to assess detection limit of a gas imaging system in short range. In this paper, a wind tunnel experiment is designed. Under different leaking rate and wind speed, concentration in different spatial positions is measured by portable gas detectors. Through analyzing the experimental data, the two parameters ?y(x) and ?z (x) that determine the plume dispersion in Gaussian model are adjusted to produce the best curve fit to the gas concentration data. Then a concentration distribution model for small mount gas leakage in short range is established. Various gases, ethylene and methane are used to testify this model.

Wang, Meirong; Wang, Lingxue; Li, Jiakun; Long, Yunting; Gao, Yue

2012-06-01

111

Concentration  

NSDL National Science Digital Library

This is the NCTM Android app of their familiar on line Illuminations game, "Concentration" ( cataloged separately ) which challenges a user to match whole numbers, shapes, fractions, or multiplication facts to equivalent representations. This game can be played by one or two players taking turns and can be played in clear pane mode, or for added challenge, with the windows closed.

2011-08-11

112

Optimizing the boron effect  

Microsoft Academic Search

The effects of boron content varying from 0.0001 to 0.0110 wt pct were studied to determine the optimum boron range for commercially desirable combinations of hardenability and notch toughness in 11\\/4 in. thick steel plate made from grade ASTM A514-J. Increasing boron content up to 0.0025 pct resulted in a gradually increasing boron hardenability factor which reached a maximum value

G. F. Melloy; P. R. Summon; P. P. Podgursky

1973-01-01

113

Optimizing the boron effect  

Microsoft Academic Search

The effects of boron content varying from 0.0001 to 0.0110 wt pct were studied to determine the optimum boron range for commercially\\u000a desirable combinations of hardenability and notch toughness in 11\\/4 in. thick steel plate made from grade ASTM A514-J. Increasing\\u000a boron content up to 0.0025 pct resulted in a gradually increasing boron hardenability factor which reached a maximum value

G. F. Melloy; P. R. Summon; P. P. Podgursky

1973-01-01

114

[Measurement of nonuniform temperature and concentration distribution by absorption spectroscopy based on least-square fitting].  

PubMed

The measurement of nonuniform temperature and concentration distributions was investigated based on tunable diode laser absorption spectroscopy technology. Through direct scanning multiple absorption lines of H2O, two zones for temperature and concentration distribution were achieved by solving nonlinear equations by least-square fitting from numerical and experimental studies. The numerical results show that the calculated temperature and concentration have relative errors of 8.3% and 7.6% compared to the model, respectively. The calculating accuracy can be improved by increasing the number of absorption lines and reduction in unknown numbers. Compared with the thermocouple readings, the high and low temperatures have relative errors of 13.8% and 3.5% respectively. The numerical results are in agreement with the experimental results. PMID:24159843

Song, Jun-Ling; Hong, Yan-Ji; Wang, Guang-Yu; Pan, Hu

2013-08-01

115

Vertical variations of particle number concentration and size distribution in a street canyon in Shanghai, China.  

PubMed

Measurements of particle number size distribution in the range of 10-487 nm were made at four heights on one side of an asymmetric street canyon on Beijing East Road in Shanghai, China. The result showed that the number size distributions were bimodal or trimodal and lognormal in form. Within a certain height from 1.5 to 20 m, the particle size distributions significantly changed with increasing height. The particle number concentrations in the nucleation mode and in the Aitken mode significantly dropped, and the peaking diameter in the Aitken mode shifted to larger sizes. The variations of the particle number size distributions in the accumulation mode were less significant than those in the nucleation and Aitken modes. The particle number size distributions slightly changed with increasing height ranging from 20 to 38 m. The particle number concentrations in the street canyon showed a stronger association with the pre-existing particle concentrations and the intensity of the solar radiation when the traffic flow was stable. The particle number concentrations were observed higher in Test I than in Test II, probably because the small pre-existing particle concentrations and the intense solar radiation promoted the formation of new particles. The pollutant concentrations in the street canyon showed a stronger association with wind speed and direction. For example, the concentrations of total particle surface area, total particle volume, PM2.5 and CO were lower in Test I (high wind speed and step-up canyon) than in Test II (low wind speed and wind blowing parallel to the canyon). The equations for the normalized concentration curves of the total particle number, CO and PM2.5 in Test I and Test II were derived. A power functions was found to be a good estimator for predicting the concentrations of total particle number, CO and PM2.5 at different heights. The decay rates of PM2.5 and CO concentrations were lower in Test I than in Test II. However, the decay rate of the total particle number concentration in Test I was similar to that in Test II. No matter how the wind direction changed, for example, in the step-up case or wind blowing parallel to the canyon, the decay rates of the total particle number concentration were larger than those of PM2.5 and CO concentrations. For example, CO concentrations decreased by 0.33 and 0.69 at the heights ranging from 1.5 to 38 m in Test I and Test II, while the total particle number concentrations decreased by 0.72 and 0.85 within the same height ranges in Test I and Test II. It is concluded that the coagulation process, besides the dilution process, affected the total particle number concentration. PMID:17418375

Li, X L; Wang, J S; Tu, X D; Liu, W; Huang, Z

2007-06-01

116

Effect of boron in Fe 70 Al 30 nanostructured alloys produced by mechanical alloying  

NASA Astrophysics Data System (ADS)

The substitution of aluminum by boron in the Fe70Al30 system prepared by high energy ball milling is studied when the B content ranged from 0 up to 20 at. %, and the milling times were 24, 48 and 72 h. X-ray diffraction (XRD) patterns of Fe70Al30 showed a predominant bcc structural phase with a lattice parameter larger than that of ?-Fe. A second (tetragonal) phase arose with the addition of boron. It is associated to the existence of (Fe, Al)2B, although the values of the lattice parameters are slightly different from those found in the literature. This phase shows high stability; its lattice parameters and the Mössbauer parameters do not show notable variations, either with milling time or composition. It was also evidenced that an increase of boron content and of milling time produced a decrease of the lattice parameter of the Fe-Al bcc structure. This is in agreement with the small atomic radius of boron in comparison with that of aluminum. This also allows boron to occupy interstitial sites in the lattice, increasing the grain size and giving rise to the ductile character of the alloy. On the other hand, 300 K transmission Mössbauer spectra (TMS) were fitted, for low boron concentrations (<8 at.%), with a hyperfine field distribution (HFD) associated with the bcc phase. For high boron content (?8 at.%), a magnetic component related to the tetragonal phase is added and its broadened lines are attributed to the disordered character of Fe2B, probably induced by the milling process.

Rico, M. M.; Pérez Alcázar, G. A.; Greneche, J. M.

2013-04-01

117

Number concentration and size distribution of aerosol particles in the middle troposphere over the Western Pacific Ocean  

Microsoft Academic Search

Number concentration and size distribution of aerosol particles were measured on board aircraft during the PACE (Pacific Atmospheric Chemistry Experiment) campaign from Australia to Japan in January 1994. The spatial distribution of condensation nuclei (CN) (r ? 4 nm) at 5–6 km altitude showed large variabilities in concentrations from 102 to 103 mg?1 that is, the concentrations were low (70–500

Jørgen Jensen; John L. Gras

1996-01-01

118

Particle concentrations and number size distributions in the planetary boundary layer derived from airship based measurements  

NASA Astrophysics Data System (ADS)

Atmospheric particles play a key role for regional and global climate due to their direct and indirect radiative forcing effects. The concentration and size of the particles are important variables to these effects. Within the continental planetary boundary layer (PBL) the particle number size distribution is influenced by meteorological parameters, local sinks and sources resulting in variable spatial distributions. However, measurements of particle number size distributions over a broad vertical range of the PBL are rare. The airship ZEPPELIN NT is an ideal platform to measure atmospheric aerosols on a regional scale within an altitude range up to 1000 m. For campaigns in the Netherlands, Northern Italy and South Finland in 2012 and 2013 the airship was deployed with a wide range of instruments, including measurements of different trace gases, short lived radicals, solar radiation, aerosols and meteorological parameters. Flights were carried out at different times of the day to investigate the influence of the diurnal evolution of the PBL on atmospheric trace gases and aerosols. During night and early morning hours the concentration and size distribution of atmospheric particles were found to be strongly influenced by the layered structure of the PBL, i.e. the nocturnal boundary layer and the residual layer. Within the residual layer particle concentrations stay relatively constant as this layer is decoupled from ground sources. The particles persist in the accumulation mode as expected for an aged aerosol. In the nocturnal boundary layer particle concentrations and size are more dynamic with higher concentrations than in the residual layer. A few hours after sunrise, the layered structure of the PBL intermixes. During daytime the PBL is well mixed and a negative concentration gradient with increasing height is observed. Several height profiles at different times of the day and at different locations in Europe were measured. The aerosol measurements will be discussed together with meteorological parameters and trace gas measurements. Acknowledgement: PEGASOS project funded by the European Commission and the Framework Program 7 (FP7-ENV-2010-265148).

Tillmann, Ralf; Zhao, Defeng; Ehn, Mikael; Hofzumahaus, Andreas; Holland, Frank; Rohrer, Franz; Kiendler-Scharr, Astrid; Wahner, Andreas

2014-05-01

119

Fluoride concentrations and distribution in premolars of children from low and optimal fluoride areas.  

PubMed

We have compared the fluoride (F) concentrations from the enamel surface to the dentino-enamel junction (DEJ), and through dentine to the dentino-pulpal junction (DPJ) in premolars extracted from school children in Chemnitz (former Karl-Marx-Stadt), Germany (F: 1.0 ppm in the water supply), Erfurt, Germany (F: 0.2 ppm in the water supply) and Nagoya, Japan (F: 0.1 ppm in the water supply). In teeth from children in Cheminitz, Erfurt and Nagoya, the profiles of F distribution using an abrasive microsampling technique revealed high F concentrations in the enamel surface, with a substantial decrease towards a plateau in the interior. In dentine the F concentrations were higher than in enamel, and also decreased to a plateau from the DEJ, thereafter increasing considerably towards the DPJ. F concentrations at any depth in the enamel and dentine of teeth from Chemnitz were 2-3 times higher than those in Erfurt and Nagoya. There was no significant difference in F concentrations or distributions between Erfurt and Nagoya. Close to the DEJ in both enamel and dentine as well as the enamel surface and the DPJ side of dentine, higher F concentrations were observed in Chemnitz compared with Erfurt and Nagoya. PMID:8850587

Takeuchi, K; Nakagaki, H; Toyama, Y; Kimata, N; Ito, F; Robinson, C; Weatherell, J A; St-osser, L; Künzel, W

1996-01-01

120

The interaction of boron with goethite: experiments and CD-MUSIC modeling.  

PubMed

Boron (B) is an essential element for plants and animals growth that interacts with mineral surfaces regulating its bioavailability and mobility in soils, sediments, and natural ecosystems. The interaction with mineral surfaces is quite important because of a narrow range between boron deficiency and toxicity limits. In this study, the interaction of boric acid with goethite (?-FeOOH) was measured in NaNO(3) background solution as a function of pH, ionic strength, goethite and boron concentration representing as adsorption edges and isotherms. Boron adsorption edges showed a bell-shaped pattern with maximum adsorption around pH 8.50, whereas adsorption isotherms were rather linear. The adsorption data were successfully described with the CD-MUSIC model in combination with the Extended Stern (ES) model. The charge distribution (CD) of inner-sphere boron surface complexes was calculated from the geometry optimized with molecular orbital calculations applying density functional theory (MO/DFT). The CD modeling suggested dominant binding of boric acid as a trigonal inner-sphere complex with minor contributions of a tetrahedral inner-sphere complex (at high pH) and a trigonal outer-sphere complex (at low pH). The interpretation with the CD model is consistent with the spectroscopic observations. PMID:21185584

Goli, Esmaiel; Rahnemaie, Rasoul; Hiemstra, Tjisse; Malakouti, Mohammad Jafar

2011-03-01

121

The effect of dissolved oxygen concentration on the structure, size and size distribution of activated sludge flocs  

Microsoft Academic Search

The variations in activated sludge floc structure, size and size distribution were studied for different dissolved oxygen (DO) concentrations in pilot scale completely mixed reactors. The size distribution by volume for flocs larger than about 10?m fitted well to log–normal distribution functions. No clear relationship between DO concentration and average floc diameter could be found; there was only a trend

Britt-Marie Wilén; Peter Balmér

1999-01-01

122

The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity  

Microsoft Academic Search

The concentrations of many elements, including boron, are increasing in aquatic ecosystems due to anthropogenic activities. Laboratory studies were undertaken to evaluate the toxicity of waterborne boron to two key fresh water macroinvertebrates and to evaluate the effects of water hardness and sulfate on boron toxicity. Acute toxicity evaluations of waterborne sodium tetraborate resulted in 48 h. LC50 values of

Kurt J. Maier; Allen W. Knight

1991-01-01

123

Boron incorporation into calcite during growth: Implications for the use of boron in carbonates as a pH proxy  

NASA Astrophysics Data System (ADS)

Current interest in boron incorporation into carbonates arises from the observation that the isotopic composition of carbonates depends on the pH of the fluid from which they precipitated. This finding opened the possibility of using boron isotopic composition of natural carbonates as a paleo-pH proxy. In this study, coprecipitation of boron by calcite was investigated using Atomic Force Microscopy (AFM), as a function of pH, supersaturation and boron concentration. In situ AFM observations reported here provide experimental evidence of boron incorporation into calcite, which takes place to a greater extent at high pH (9.5) and under close to equilibrium conditions. Moreover, we report nanoscale observations that give indirect evidence of the incorporation of boron in non-lattice sites. Step-specific interactions of tetrahedrally-coordinated boron with calcite obtuse steps during growth are revealed as a reduction in the obtuse-step spreading rate as well as rounding and roughening of such steps. Our results suggest that, together with changes in pH, variations in the calcification rate or the calcite crystallographic form in which boron is incorporated are important factors to consider when using boron in carbonates as a pH proxy, as these factors could also influence the amount of boron incorporated during growth and possibly the boron isotopic signature.

Ruiz-Agudo, E.; Putnis, C. V.; Kowacz, M.; Ortega-Huertas, M.; Putnis, A.

2012-09-01

124

Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai.  

PubMed

The aerosol number concentration and size distribution as well as size-resolved particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The number of haze days accounted for 43%, of which 30% was severe (visibility<2km) and moderate (2km?visibility<3km) haze, mainly distributed in winter and spring. The mean particle number concentration was about 17,000/cm(3) in haze, more than 2 times that in clean days. The greatest increase of particle number concentration was in 0.5-1?m and 1-10?m size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of particle number concentration was within 50-100nm and 100-200nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102, 49, 15?m(3)/cm(3) and 949, 649, 206?m(2)/cm(3), respectively. As haze events got more severe, the number concentration of particles smaller than 50nm decreased, but the particles of 50-200nm and 0.5-1?m increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4(+), SO4(2-) and NO3(-) increased greatly, followed by Na(+), K(+), Ca(2+) and Cl(-). These ions were very different in size-resolved particles during haze and photochemical smog episodes. PMID:25193840

Wang, Xuemei; Chen, Jianmin; Cheng, Tiantao; Zhang, Renyi; Wang, Xinming

2014-09-01

125

Effects of microgravity on growth hormone concentration and distribution in plants  

NASA Technical Reports Server (NTRS)

On earth, gravity affects the distribution of the plant growth hormone, indole-3-acetic acid (IAA), in a manner such that the plant grows into a normal vertical orientation (shoots up, roots down). How the plant controls the amount and distribution of IAA is only partially understood and is currently under investigation in this laboratory. The question to be answered in the flight experiment concerns the effect of gravity on the concentration, turn over, and distribution of the growth hormone. The answer to this question will aid in understanding the mechanism by which plants control the amount and distribution of growth hormone. Such knowledge of a plant's hormonal metabolism may aid in the growth of plants in space and will lead to agronomic advances.

Schulze, Aga; Jensen, Philip; Desrosiers, Mark; Bandurski, Robert S.

1989-01-01

126

Spatiotemporal distribution and short-term trends of particulate matter concentration over China, 2006-2010.  

PubMed

Air quality problems caused by atmospheric particulate have drawn broad public concern in the global scope. In the paper, the spatiotemporal distributions of fine particle (PM2.5) and inhalable particle (PM10) concentrations estimated with the artificial neural network (ANN) over China during 2006 to 2010 have been discussed. Most high PM10 concentration appears in Xinjiang, Qinghai, Gansu, Ningxia, Hubei, and parts of Inner Mongolia. The distribution of PM2.5 concentration is consistent with China's three gradient terrains. The seasonal variations of PM2.5 and PM10 concentrations both indicate that they are higher in north China in spring and winter, lowest in summer. In autumn, most provinces in south China appear high value. In particular, high PM2.5 concentration appears in the southeast coastal cities while high PM10 concentration prefers the central regions in south China. On this basis, seasonal Mann-Kendall test method is utilized to analyze the short-term trends. The results also show significant changes of PM2.5 and PM10 concentrations of China in the past 5 years, and most provinces present the tendency of reduction (3-5 ?g/m(3) for PM2.5 and 10-20 ?g/m(3) for PM10 per year) while a fraction of provinces appear the increasing trend of 8-16 ?g/m(3) (PM2.5) and 16-30 ?g/m(3) (PM10). Simultaneously, PM2.5 population exposure is discussed with the combination of population density-gridded data. Municipalities get much higher exposure level than other provinces. Shanghai suffers the highest population exposure to PM2.5, followed by Beijing and then Tianjin, Jiangsu province. Most provincial capitals, such as Guangzhou, Nanjing, Chengdu, and Wuhan, face much higher exposure level than other regions of their province. Moreover, the PM2.5 exposure situation is more serious in southeast than northwest regions for Beijing-Tianjin-Hebei region. Also, per capita PM2.5 concentration and population-weighted PM2.5 concentration are calculated. The former shows that the high-level regions distribute in Guangdong, Shanghai, and Tianjin, while the latter in Hebei, Chongqing, and Shandong provinces. Further studies may consider optimizing concentration estimation model and use it to discuss the effects of particulate matters on human health. PMID:24824505

Yao, Ling; Lu, Ning

2014-08-01

127

Ultralow Contact Resistivity for a Metal/p-Type Silicon Interface by High-Concentration Germanium and Boron Doping Combined with Low-Temperature Annealing  

NASA Astrophysics Data System (ADS)

A contact resistivity of 6.9×10-9 ?.cm2 has been obtained in an AlSi (1 wt %)-Cu (0.5 wt %) alloy/silicon system by using heavy-dose ion implantations of germanium and boron combined with low-temperature annealing. The analysis of the combined state showed that B12 cluster was incorporated and the supersaturation activation layer was formed into the region where germanium separated. Separated germanium is expected to have high interface state density. It is considered that this interface state density also has a Fermi level, and in order to reduce the difference from the Fermi level of the substrate, the charge moves to interface state density from the substrate. As a result, it is not based on a metallic material but a work function becomes small because pinning by which a Fermi level is fixed to interface state density occurs owing to the substrate/metal interface. It is considered to be attributable to the existence of a Ge-rich layer formed by low-temperature annealing, and a supersaturation activation layer that lowers contact resistance was formed.

Murakoshi, Atsushi; Iwase, Masao; Niiyama, Hiromi; Koike, Mitsuo; Suguro, Kyoichi

2013-07-01

128

Direct measurement of concentration distribution within the boundary layer of an ion-exchange membrane.  

PubMed

In this study the concentration distributions within the diffusion boundary layer were obtained by directly measuring the potential drops while the currents (under- and overlimiting) passed through the Neosepta CMX cation-exchange membrane (Tokuyama Corp., Japan). Potential drops according to the distance from the membrane surface on the depleted side were measured using a microelectrode to obtain the concentration profile. From the concentration profiles obtained, it was observed that the diffusion boundary layers existed in the range of 300-350 microm, which reasonably coincide with the theoretical diffusion boundary layer thickness calculated from the limiting current density. Although there were some deviations between the concentrations determined from the Nernst model and those from experiments, it was confirmed that the Nernst model effectively depicts the transport phenomena in the ion-exchange membrane system. In addition it was found that the salt concentration at the membrane surface increased when the currents applied exceeded the limiting current. It is thought that the concentration polarization formed in the diffusion boundary layer at currents near or lower than the limiting current was disturbed by a turbulent convection when the current was greater than the limiting current. As a consequence, the concentration at the membrane surface increased to a sufficient level for generation of the overlimiting current. PMID:16290735

Choi, Jae-Hwan; Park, Jin-Soo; Moon, Seung-Hyeon

2002-07-15

129

Distribution of the concentration of heavy metals associated with the sediment particles accumulated on road surfaces.  

PubMed

The heavy metal pollution caused by road run-off water constitutes a problem in urban areas. The metallic load associated with road sediment must be determined in order to study its impact in drainage systems and receiving waters, and to perfect the design of prevention systems. This paper presents data regarding the sediment collected on road surfaces in the city of Torrelavega (northern Spain) during a period of 65 days (132 samples). Two sample types were collected: vacuum-dried samples and those swept up following vacuuming. The sediment loading (g m(-2)), particle size distribution (63-2800 microm) and heavy metal concentrations were determined. The data showed that the concentration of heavy metals tends to increase with the reduction in the particle diameter (exponential tendency). The concentrations ofPb, Zn, Cu, Cr, Ni, Cd, Fe, Mn and Co in the size fraction <63 microm were 350, 630, 124, 57, 56, 38, 3231, 374 and 51 mg kg(-1), respectively (average traffic density: 3800 vehicles day(-1)). By increasing the residence time of the sediment, the concentration increases, whereas the ratio of the concentration between the different size fractions decreases. The concentration across the road diminishes when the distance between the roadway and the sampling siteincreases; when the distance increases, the ratio between size fractions for heavy metal concentrations increases. Finally, the main sources of heavy metals are the particles detached by braking (brake pads) and tyre wear (rubber), and are associated with particle sizes <125 microm. PMID:21882553

Zafra, C A; Temprano, J; Tejero, I

2011-07-01

130

Characteristics of boron-dose enhancer dependent on dose protocol and 10B concentration for BNCT using near-threshold 7Li(p,n)7Be direct neutrons  

NASA Astrophysics Data System (ADS)

The dependence of boron-dose enhancer (BDE) characteristics on dose protocol and 10B concentration was evaluated for BNCT using near-threshold 7Li(p,n)7Be direct neutrons. The treatable protocol depth (TPD) was utilized as an evaluation index. MCNP calculations were performed for near-threshold 7Li(p,n)7Be at a proton energy of 1.900 MeV and for a polyethylene BDE. The effect of dose protocol on BDE characteristics was reflected in terms of the optimum BDE thickness needed for maximum TPD which was found to be independent of the treatable dose but was observed to vary for different combinations of the tolerance doses for heavy charged particles and gamma rays. For the 10B concentration dependence, the TPD was increased by increasing the T/N ratio, i.e., the ratio of the 10B concentration in the tumour (10BTumour) to that in the normal tissue (10BNormal), and by increasing 10BTumour and 10BNormal at constant T/N ratio. It was found that the use of BDE becomes unnecessary from the viewpoint of increasing the TPD, when 10BTumour is over a certain level which is decided by the conditions of the dose protocol.

Tanaka, Kenichi; Kobayashi, Tooru; Bengua, Gerard; Nakagawa, Yoshinobu; Endo, Satoru; Hoshi, Masaharu

2005-01-01

131

Ultrahigh resolution mass spectroscopy of boron cluster ions  

Microsoft Academic Search

Boron clusters have recently received considerable attention as a possible solution to the throughput dilemma associated with ultra-low energy (sub keV) p-type source drain extension implants required by cutting edge complimentary metal–oxide semiconductor (CMOS) technology. Boron cluster ion beams contain many masses due to the binomial distribution of the two naturally occurring isotopes (masses 10 and 11) of boron. The

Dale Jacobson; Thomas Horsky; Wade Krull; Bob Milgate

2005-01-01

132

Prediction of In-Phantom Dose Distribution Using In-Air Neutron Beam Characteristics for Boron Neutron Capture Synovectomy  

SciTech Connect

A monoenergetic neutron beam simulation study was carried out to determine the optimal neutron energy range for treatment of rheumatoid arthritis using radiation synovectomy. The goal of the treatment is the ablation of diseased synovial membranes in joints such as knees and fingers. This study focuses on human knee joints. Two figures of merit are used to measure the neutron beam quality, the ratio of the synovium-absorbed dose to the skin-absorbed dose, and the ratio of the synovium-absorbed dose to the bone-absorbed dose. It was found that (a) thermal neutron beams are optimal for treatment and that (b) similar absorbed dose rates and therapeutic ratios are obtained with monodirectional and isotropic neutron beams. Computation of the dose distribution in a human knee requires the simulation of particle transport from the neutron source to the knee phantom through the moderator. A method was developed to predict the dose distribution in a knee phantom from any neutron and photon beam spectra incident on the knee. This method was revealed to be reasonably accurate and enabled one to reduce the particle transport simulation time by a factor of 10 by modeling the moderator only.

Verbeke, Jerome M. [University of California, Berkeley (United States); Chen, Allen S. [University of California, Berkeley (United States); Vujic, Jasmina L. [University of California, Berkeley (United States); Leung, Ka-Ngo [Lawrence Berkeley National Laboratory (United States)

2000-08-15

133

Distribution of sulfhydryl boranes in mice and rats  

SciTech Connect

The distribution of boron in mice bearing transplanted Harding-Passey melanomas after rapid and slow administration of monomer were studied. Thin layer chromatographic analysis of the corresponding infusion solution revealed a slow-moving principal band that was later shown to correspond to Na/sub 4/B/sub 24/H/sub 22/S/sub 2/, the dimer of Na/sub 2/B/sub 12/H/sub 11/SH. It was found that while monomer and chemically synthesized dimer yielded similar boron concentrations when they were given rapidly intraperitoneally to mice, the dimer yielded higher boron concentrations in mouse melanoma and higher melanoma-blood boron concentration when each was infused slowly intraperitoneally for 8 to 9 days. Studies have been started on the uptake of dimer into an intracerebrally implanted rat glioma. Boron levels in the rat glioma and in the mouse melanoma from slow intraperitoneal infusion of proportionately comparable amounts of dimer, are similar. However, after these slow infusions boron levels in rat blood are about as high as boron levels in rat brain tumor. 6 refs., 1 fig., 4 tabs.

Slatkin, D.N.; Micca, P.L.; Laster, B.H.; Fairchild, R.G.

1986-01-01

134

Boronated dipeptide borotrimethylglycylphenylalanine as a potential boron carrier in boron neutron capture therapy for malignant brain tumors.  

PubMed

Takagaki, M., Ono, K., Masunaga, S-I., Kinashi, Y., Oda, Y., Miyatake, S-I., Hashimoto, N., Powell, W., Sood, A. and Spielvogel, B. F. Boronated Dipeptide Borotrimethylglycylphenylalanine as a Potential Boron Carrier in Boron Neutron Capture Therapy for Malignant Brain Tumors. Radiat. Res. 156, 118-122 (2001).A boronated dipeptide, borotrimethylglycylphenylalanine (BGPA), was synthesized as a possible boron carrier for boron neutron capture therapy (BNCT) for malignant brain tumors. In vitro, at equal concentrations of (10)B in the extracellular medium, BGPA had the same effect in BNCT as p-boronophenylalanine (BPA). Boron analysis was carried out using prompt gamma-ray spectrometry and track-etch autoradiography. The tumor:blood and tumor:normal brain (10)B concentration ratios were 8.9 +/- 2.1 and 3.0 +/- 1.2, respectively, in rats bearing intracranial C6 gliosarcomas using alpha-particle track autoradiography. The IC(50), i.e. the dose capable of inhibiting the growth of C6 gliosarcoma cells by 50% after 3 days of incubation, was 5.9 x 10(-3) M BGPA, which is similar to that of 6.4 x 10(-3) M for BPA. The amide bond of BGPA is free from enzymatic attack, since it is protected from hydrolysis by the presence of a boron atom at the alpha-carbon position of glycine. These results suggest promise for the use of this agent for BNCT of malignant brain tumors. Further preclinical studies of BGPA are warranted, since BGPA has advantages over both BPA and BSH. PMID:11418080

Takagaki, M; Powell, W; Sood, A; Spielvogel, B F; Hosmane, N S; Kirihata, M; Ono, K; Masunaga, S I; Kinashi, Y; Miyatake, S I; Hashimoto, N

2001-07-01

135

Concentration and distribution of sixty-one elements in coals from DPR Korea  

Microsoft Academic Search

Fifty coal samples (28 anthracite and 22 lignites) were collected from both main and small coal mines in DPR Korea prioritized by resource distribution and coal production. The concentrations of 61 elements in 50 coal samples were determined by several multielement and element-specific techniques, including inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS), ion

Jun Hu; Baoshan Zheng; Robert B. Finkelman; Binbin Wang; Mingshi Wang; Shehong Li; Daishe Wu

2006-01-01

136

Spatially Resolved Temperature and Water Vapor Concentration Distributions in Supersonic Combustion Facilities by TDLAT  

NASA Technical Reports Server (NTRS)

Detailed knowledge of the internal structure of high-enthalpy flows can provide valuable insight to the performance of scramjet combustors. Tunable Diode Laser Absorption Spectroscopy (TDLAS) is often employed to measure temperature and species concentration. However, TDLAS is a path-integrated line-of-sight (LOS) measurement, and thus does not produce spatially resolved distributions. Tunable Diode Laser Absorption Tomography (TDLAT) is a non-intrusive measurement technique for determining two-dimensional spatially resolved distributions of temperature and species concentration in high enthalpy flows. TDLAT combines TDLAS with tomographic image reconstruction. More than 2500 separate line-of-sight TDLAS measurements are analyzed in order to produce highly resolved temperature and species concentration distributions. Measurements have been collected at the University of Virginia's Supersonic Combustion Facility (UVaSCF) as well as at the NASA Langley Direct-Connect Supersonic Combustion Test Facility (DCSCTF). Due to the UVaSCF s unique electrical heating and ability for vitiate addition, measurements collected at the UVaSCF are presented as a calibration of the technique. Measurements collected at the DCSCTF required significant modifications to system hardware and software designs due to its larger measurement area and shorter test duration. Tomographic temperature and water vapor concentration distributions are presented from experimentation on the UVaSCF operating at a high temperature non-reacting case for water vitiation level of 12%. Initial LOS measurements from the NASA Langley DCSCTF operating at an equivalence ratio of 0.5 are also presented. Results show the capability of TDLAT to adapt to several experimental setups and test parameters.

Busa, K. M.; McDaniel J. C.; Diskin, G. S.; DePiro, M. J.; Capriotti, D. P.; Gaffney, R. L.

2012-01-01

137

On the concentration of large deviations for fat tailed distributions, with application to financial data  

NASA Astrophysics Data System (ADS)

Large deviations for fat tailed distributions, i.e. those that decay slower than exponential, are not only relatively likely, but they also occur in a rather peculiar way where a finite fraction of the whole sample deviation is concentrated on a single variable. The regime of large deviations is separated from the regime of typical fluctuations by a phase transition where the symmetry between the points in the sample is spontaneously broken. For stochastic processes with a fat tailed microscopic noise, this implies that, while typical realizations are well described by a diffusion process with continuous sample paths, large deviation paths are typically discontinuous. For eigenvalues of random matrices with fat tailed distributed elements, a large deviation where the trace of the matrix is anomalously large concentrates on just a single eigenvalue, whereas in the thin tailed world the large deviation affects the whole distribution. These results find a natural application to finance. Since the price dynamics of financial stocks are characterized by fat tailed increments, large fluctuations in stock prices are expected to be realized by discrete jumps. Interestingly, we find that large excursions of prices are more likely realized by continuous drifts rather than by discontinuous jumps. Indeed, auto correlations suppress the concentration of large deviations. Financial covariance matrices also exhibit an anomalously large eigenvalue, the market mode, as compared to the prediction of random matrix theory. We show that this is explained by a large deviation with excess covariance rather than by one with excess volatility.

Filiasi, Mario; Livan, Giacomo; Marsili, Matteo; Peressi, Maria; Vesselli, Erik; Zarinelli, Elia

2014-09-01

138

Concentration and size distribution of airborne hexavalent chromium in electroplating factories.  

PubMed

Studies have shown that chromium from electroplating factories can cause respiratory problems to workers after prolonged exposure. Since Taiwan has a relatively high number of electroplating factories and minimal data regarding chromium's effect on workers, the authors undertook this study focusing on the size distribution of airborne hexavalent chromium and its concentration levels within the factory. Both area and personal sampling were conducted using a particle fractionating sampler. Samples were analyzed using visible spectrophotometry. A comparison of three types of factories-chromium, nickel-chromium, and zinc-showed that the highest concentrations were found in chromium electroplating factories near the electroplating tank. Hexavalent chromium particles obtained from area sampling had mass median diameters between 1.67-6.38 microns and 0.75-4.73 microns for personal sampling. Particles of this high concentration and small size can enter and cause considerable damage to the respiratory tract. PMID:9018834

Kuo, H W; Lai, J S; Lin, T I

1997-01-01

139

Distribution of dissolved and particulate radiocesium concentrations along rivers and the relations between radiocesium concentration and deposition after the nuclear power plant accident in Fukushima.  

PubMed

This study involved measurement of concentrations of dissolved and particulate radiocesium ((134)Cs and (137)Cs) in river water, and determination of the quantitative relations between the amount of deposited (137)Cs and (137)Cs concentrations in river waters after the Fukushima Daiichi nuclear power plant accident. First, the current concentrations of dissolved and particulate (134)Cs·(137)Cs were determined in a river watershed from 20 sampling locations in four contaminated rivers (Abukuma, Kuchibuto, Shakado, and Ota). Distribution characteristics of different (137)Cs forms varied with rivers. Moreover, a higher dissolved (137)Cs concentration was observed at the sampling location where the (137)Cs deposition occurred much more heavily. In contrast, particulate (137)Cs concentration along the river was quite irregular, because fluctuations in suspended solids concentrations occur easily from disturbance and heavy precipitation. A similar tendency with dissolved (137)Cs distribution was observed for the (137)Cs concentration per unit weight of suspended solids. Regression analysis between deposited (137)Cs and dissolved/particulate (137)Cs concentrations was performed for the four rivers. The results showed a strong correlation between deposited (137)Cs and dissolved (137)Cs, and a relatively weak correlation between deposited (137)Cs and particulate (137)Cs concentration for each river. However, if the particulate (137)Cs concentration was converted to (137)Cs concentration per unit weight of suspended solid, the values showed a strong correlation with deposited (137)Cs. PMID:24813506

Tsuji, Hideki; Yasutaka, Tetsuo; Kawabe, Yoshishige; Onishi, Takeo; Komai, Takeshi

2014-09-01

140

Aerosol size distribution and mass concentration measurements in various cities of Pakistan.  

PubMed

During March and April 2010 aerosol inventories from four large cities in Pakistan were assessed in terms of particle size distributions (N), mass (M) concentrations, and particulate matter (PM) concentrations. These M and PM concentrations were obtained for Karachi, Lahore, Rawalpindi, and Peshawar from N concentrations using a native algorithm based on the Grimm model 1.109 dust monitor. The results have confirmed high N, M and PM concentrations in all four cities. They also revealed major contributions to the aerosol concentrations from the re-suspension of road dust, from sea salt aerosols, and from vehicular and industrial emissions. During the study period the 24 hour average PM(10) concentrations for three sites in Karachi were found to be 461 ?g m(-3), 270 ?g m(-3), and 88 ?g m(-3), while the average values for Lahore, Rawalpindi and Peshawar were 198 ?g m(-3), 448 ?g m(-3), and 540 ?g m(-3), respectively. The corresponding 24 hour average PM(2.5) concentrations were 185 ?g m(-3), 151 ?g m(-3), and 60 ?g m(-3) for the three sites in Karachi, and 91 ?g m(-3), 140 ?g m(-3), and 160 ?g m(-3) for Lahore, Rawalpindi and Peshawar, respectively. The low PM(2.5)/PM(10) ratios revealed a high proportion of coarser particles, which are likely to have originated from (a) traffic, (b) other combustion sources, and (c) the re-suspension of road dust. Our calculated 24 hour averaged PM(10) and PM(2.5) concentrations at all sampling points were between 2 and 10 times higher than the maximum PM concentrations recommended by the WHO guidelines. The aerosol samples collected were analyzed for crustal elements (Al, Fe, Si, Mg, Ca) and trace elements (B, Ba, Cr, Cu, K, Na, Mn, Ni, P, Pb, S, Sr, Cd, Ti, Zn and Zr). The averaged concentrations for crustal elements ranged from 1.02 ± 0.76 ?g m(-3) for Si at the Sea View location in Karachi to 74.96 ± 7.39 ?g m(-3) for Ca in Rawalpindi, and averaged concentrations for trace elements varied from 7.0 ± 0.75 ng m(-3) for B from the SUPARCO location in Karachi to 17.84 ± 0.30 ?g m(-3) for Na at the M. A. Jinnah Road location, also in Karachi. PMID:21677943

Alam, Khan; Blaschke, Thomas; Madl, Pierre; Mukhtar, Azam; Hussain, Majid; Trautmann, Thomas; Rahman, Said

2011-07-01

141

Calculation of the Concentrated Flux Density Distribution in Parabolic Trough Solar Concentrators by Monte Carlo Ray-Trace Method  

Microsoft Academic Search

In this paper, the optical concentration ratio for the parabolic trough solar concentrators (PTSCs), which is a key boundary condition in the heat transfer performance analysis, would be simulated and computed by Monte Carlo Ray-Trace (MCRT) method in different conditions. In the computation process, non-parallelism of solar rays, geometric concentrating ratio and rim angle would be considered. Based on the

Bin Yang; Jun Zhao; Tao Xu; Qiang Zhu

2010-01-01

142

Influence of pH in the elimination of boron by means of reverse osmosis  

Microsoft Academic Search

The European Union (EU) stipulates the maximum admissible value for the concentration of boron at 1 ppm and the World Health Organization (WHO) at 0.3 ppm as the non-observed effect level (NOEL) for drinking water. The content of boron in water can be reduced by means of various processes. Treatment by means of conventional reverse osmosis only reduces the boron

M. Rodríguez Pastor; A. Ferrándiz Ruiz; M. F. Chillón; D. Prats Rico

2001-01-01

143

Boron nitride: Composition, optical properties and mechanical behavior  

NASA Astrophysics Data System (ADS)

A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphate. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by X-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on III-V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.

Pouch, John J.; Alterovitz, Samuel A.; Miyoshi, Kazuhisa; Warner, Joseph D.

1987-04-01

144

Boron Arsenide and Boron Phosphide for High Temperature and Luminescent Devices. [semiconductor devices - crystal growth/crystal structure  

NASA Technical Reports Server (NTRS)

The crystal growth of boron arsenide and boron phosphide in the form of bulk crystals and epitaxial layers on suitable substrates is discussed. The physical, chemical, and electrical properties of the crystals and epitaxial layers are examined. Bulk crystals of boron arsenide were prepared by the chemical transport technique, and their carrier concentration and Hall mobility were measured. The growth of boron arsenide crystals from high temperature solutions was attempted without success. Bulk crystals of boron phosphide were also prepared by chemical transport and solution growth techniques. Techniques required for the fabrication of boron phosphide devices such as junction shaping, diffusion, and contact formation were investigated. Alloying techniques were developed for the formation of low-resistance ohmic contacts to boron phosphide. Four types of boron phosphide devices were fabricated: (1) metal-insulator-boron phosphide structures, (2) Schottky barriers; (3) boron phosphide-silicon carbide heterojunctions; and (4) p-n homojunctions. Easily visible red electroluminescence was observed from both epitaxial and solution grown p-n junctions.

Chu, T. L.

1975-01-01

145

Influence of soil solution salinity on boron adsorption by soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Boron adsorption on two arid-zone soils from the San Joaquin Valley of California was investigated as a function of equilibrium solution B concentration (0-250 mg L-1), solution pH (3-12), and electrical conductivity (EC = 0.3 or 7.8 dS m-1). Boron adsorption on both soils increased with increasing...

146

Monte Carlo simulation of boron doping profile of fin and trench structures by plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Plasma immersion ion implantation into fins and trenches at elevated pressures is simulated. In the present work we calculate boron concentration distribution in the sample accounting for ion scattering in plasma sheath and geometric shadowing effects (ions at certain angle of incidence couldn't achieve shadowed part of trench wall and bottom). First, energy and angle distribution of ions passed through the plasma sheath to the sample surface is obtained. These data are used to calculate boron concentration distribution in the sample. Pressure range is 30-300 mTorr, plasma electron temperature 5 eV, plasma density 1010-1012 cm-3. The degree of conformity increases with the pressure raises and decreases with the density of plasma.

Shahsenov, Izat S.; Miakonkikh, Andrey V.; Rudenko, Kostantin V.

2014-12-01

147

Prediction of high concentrations and concentration distribution of a continuous point source release in a semi-idealized urban canopy using CFD-RANS modeling  

NASA Astrophysics Data System (ADS)

One of the key issues in recent research on dispersion in complex urban areas is the ability predicting high concentrations and concentration distribution of a pollutant released continuously from a point source. The present work addresses the question whether the CFD-RANS methodology can provide valid predictions of concentration peaks and distributions. A probabilistic and a deterministic approach are incorporated in the CFD-RANS code ADREA. Innovative algebraic equations for the calculation of the concentration time scales as a function of the hydrodynamic and pollutant travel times are used. The capabilities of the new methodology are validated against wind tunnel experimental data under well described boundary conditions and representative concentration measurements. The comparisons of model and wind tunnel gave fairly good results.

Efthimiou, George C.; Berbekar, Eva; Harms, Frank; Bartzis, John G.; Leitl, Bernd

2015-01-01

148

Mineral-fluid partitioning and isotopic fractionation of boron in synthetic calcium carbonate  

NASA Astrophysics Data System (ADS)

Aragonite, high-Mg calcite, and Mg-free calcite have been grown under monitored laboratory conditions to investigate mineral-fluid partitioning and isotopic fractionation of boron into carbonates. At pH ? 8, both polymorphs have boron isotopic compositions I6.5%0 lower than the boron isotopic composition of the experimental fluid ( ? 11B = 0 ± 0.7?. ). The isotopic composition of the synthetic minerals is identical to the calculated boron isotopic composition of the B(OH) 4- species in the parent solutions, consistent with only B(OH) 4- interacting with the crystal surface. The fractionation factor calculated from this isotopic offset is within analytical error of that measured between seawater and modern marine carbonates. The boron concentrations of the experimentally grown aragonite are 13.4, 85.1, and 379 ppm for total fluid boron concentrations of 0.59, 5.1, and 37.0 ppm, respectively. High-Mg calcite (HMC) coprecipitating with the aragonite has bulk boron concentrations of 5.6, 56.2, 260, and 1771 ppm for fluid boron concentrations of 0.59, 5.1, 37, and 272 ppm, respectively. Calcite boron concentrations are 1.78, 14.0, 137.7, and 1228 ppm for fluid boron concentrations of 0.45, 4.0, 44.l, and 499 ppm, respectively. Boron uptake by aragonite is greater than boron uptake by calcite grown under nearly identical conditions, while boron uptake by HMC is intermediate. Synthetic calcite crystals grown in solutions with greater than 4 ppm boron exhibit habit modification with the appearance of a subordinate form {11 overline20} in addition to the dominant {10 overline14}, the perfect cleavage rhombohedron, found in low-boron calcites. This is evidence of strong interaction of the borate with the crystal surface.

Hemming, N. G.; Reeder, R. J.; Hanson, G. N.

1995-01-01

149

Selenium accumulation, distribution and speciation in spineless prickly pear cactus: a salt, boron, and drought tolerant, selenium-enriched nutraceutical fruit crop.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Prickly pear cactus (Opuntia) may be an alternative crop to grow in drainage-impacted regions of the westside of California, where high levels of salinity, selenium (Se), and boron (B) are present. Preliminary trials have demonstrated that Opuntia can tolerate the adverse soil conditions, while accu...

150

Boron sorption from aqueous solution by hydrotalcite and its preliminary application in geothermal water deboronation.  

PubMed

Hydrotalcite and its calcination product were used to treat pure water spiked with various concentrations of boron and geothermal water containing boron as a major undesirable element. The kinetics process of boron sorption by uncalcined hydrotalcite is controlled by the diffusion of boron from bulk solution to sorbent-solution boundary film and its exchange with interlayer chloride of hydrotalcite, whereas the removal rate of boron by calcined hydrotalcite rests with the restoration process of its layered structure. The results of isotherm sorption experiments reveal that calcined hydrotalcite generally has much stronger ability to lower solution boron concentration than uncalcined hydrotalcite. The combination of adsorption of boron on the residue of MgO-Al2O3 solid solution and intercalation of boron into the reconstructed hydrotalcite structure due to "structural memory effect" is the basic mechanism based on which the greater boron removal by calcined hydrotalcite was achieved. As 15 geothermal water samples were used to test the deboronation ability of calcined hydrotalcite at 65 °C, much lower boron removal efficiencies were observed. The competitive sorption of the other anions in geothermal water, such as HCO3-, SO4(2-), and F-, is the reason why calcined hydrotalcite could not remove boron from geothermal water as effectively as from pure boron solution. However, boron removal percents ranging from 89.3 to 99.0% could be obtained if 50 times of sorbent were added to the geothermal water samples. Calcined hydrotalcite is a good candidate for deboronation of geothermal water. PMID:23695854

Guo, Qinghai; Zhang, Yin; Cao, Yaowu; Wang, Yanxin; Yan, Weide

2013-11-01

151

Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.  

PubMed Central

The successful treatment of cancer by boron neutron-capture therapy (BNCT) requires the selective concentration of boron-10 within malignant tumors. The potential of liposomes to deliver boron-rich compounds to tumors has been assessed by the examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles with mean diameters of 70 nm or less, composed of a pure synthetic phospholipid (distearoyl phosphatidylcholine) and cholesterol, have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. The hydrolytically stable borane anions B10H10(2-), B12H11SH2-, B20H17OH4-, B20H19(3-), and the normal form and photoisomer of B20H18(2-) were encapsulated in liposomes as their soluble sodium salts. The tissue concentration of boron in tumor-bearing mice was measured at several time points over 48 h after i.v. injection of emulsions of liposomes containing the borane anions. Although the boron compounds used do not exhibit an affinity for tumors and are normally rapidly cleared from the body, liposomes were observed to selectively deliver the borane anions to tumors. The highest tumor concentrations achieved reached the therapeutic range (greater than 15 micrograms of boron per g of tumor) while maintaining high tumor-boron/blood-boron ratios (greater than 3). The most favorable results were obtained with the two isomers of B20H18(2-). These boron compounds have the capability to react with intracellular components after they have been deposited within tumor cells by the liposome, thereby preventing the borane ion from being released into blood. PMID:1409600

Shelly, K; Feakes, D A; Hawthorne, M F; Schmidt, P G; Krisch, T A; Bauer, W F

1992-01-01

152

[Concentration and distribution characterization of polycyclic aromatic hydrocarbons in airborne particles with different sizes].  

PubMed

Airborne particles with different sizes were collected in 2003 at two sampling sites(urban border and suburban area) of Beijing. Compositions of polycyclic aromatic hydrocarbons were detected by GC/MS. The results show that total concentrations of 17 PAHs ranged between 0.84 and 152.23 ng/m3, in urban border area were 1.07 - 6.60 times higher than those measured in suburban area. The total concentration of PAHs increased with decreasing ambient temperature (winter > autumn > spring > summer). About 68.4% - 84.7% of PAHs were absorbed on particles having aerodynamic diameter < or = 2.0 microm. The distribution of PAHs varies with the size of the molecules. Nearly bimodal distribution was found for two- and three-rings PAHs, four- to six-rings PAHs, however, followed unimodal distribution. The overall mass median diameter (MMD) for PAHs decreases with increasing molecular weight. Higher pollution level of PAHs in wintertime is probably ascribed to domestic heating and lower ambient temperature. PMID:16004297

Zhou, Jia-Bin; Wang, Tie-Guan; Huang, Yun-Bi; Mao, Ting; Zhong, Ning-Ning; Zhang, Yi; Zhang, Xiao-Shan

2005-03-01

153

Concentration and distribution of copper and cadmium in water, sediments, detritus, plants and animals in a hardwater lowland river  

Microsoft Academic Search

The concentration and distribution of copper (Cu) and cadmium (Cd) were examined in water, sediments, detritus, plants and animals in a small, lowland, hardwater river. Consistently higher concentrations of Cu and Cd were found in all types of samples from two sites. There were marked variations in metal concentrations between different types of samples, and between seasons. Copper and Cd

S. Smith; M.-H. Chen; R. G. Bailey; W. P. Williams

1996-01-01

154

Electrochemical oxidation of electrodialysed reverse osmosis concentrate on Ti/Pt-IrO2, Ti/SnO2-Sb and boron-doped diamond electrodes.  

PubMed

Reverse osmosis concentrate from wastewater reclamation contains biorefractory trace organic contaminants that may pose environmental or health hazard. Due to its high conductivity, electrochemical oxidation of brine requires low voltage which is energetically favourable. However, the presence of chloride ions may lead to the formation of chlorinated by-products, which are likely to exert an increased toxicity and persistence to further oxidation than their non-chlorinated analogues. Here, the performance of Ti/Pt-IrO(2), Ti/SnO(2)-Sb and Si/BDD anodes was evaluated for the electrochemical oxidation of ROC in the presence of chloride, nitrate or sulfate ions (0.05 M sodium salts). In order to investigate the electrooxidation of ROC with nitrate and sulfate ions as dominant ion mediators, chloride ion concentration was decreased 10 times by electrodialytic pretreatment. The highest Coulombic efficiency for chemical oxygen demand (COD) removal was observed in the presence of high chloride ions concentration for all anodes tested (8.3-15.9%). Electrooxidation of the electrodialysed concentrate at Ti/SnO(2)-Sb and Ti/Pt-IrO(2) electrodes exhibited low dissolved organic carbon (DOC) (i.e. 23 and 12%, respectively) and COD removal (i.e. 37-43 and 6-22%, respectively), indicating that for these electrodes chlorine-mediated oxidation was the main oxidation mechanism, particularly in the latter case. In contrast, DOC removal for the electrodialysed concentrate stream was enhanced at Si/BDD anode in the presence of SO(4)(2-) (i.e. 51%) compared to NO(3)(2-) electrolyte (i.e. 41%), likely due to the contribution of SO(4)(·-) and S(2)O(8)(2-) species to the oxidative degradation. Furthermore, decreased concentration of chloride ions lead to a lower formation of haloacetic acids and trihalomethanes at all three electrodes tested. PMID:23137830

Bagastyo, Arseto Y; Batstone, Damien J; Rabaey, Korneel; Radjenovic, Jelena

2013-01-01

155

Preparation of pure boron coating film and its characterization by XPS and TDS  

NASA Astrophysics Data System (ADS)

A PACVD apparatus was designed and fabricated at Shizuoka University in order to prepare high-pure boron coating films. In the present study, some parameters, especially feeding gas concentration, substrate temperature and CVD input power, have been optimized to prepare pure boron coating films. It was found that the purity of boron coating film was controlled by the decaborane concentration of feeding gas and substrate temperature during the PACVD process, and each optimized values were 0.4 and 473 K, respectively. The atomic composition of boron in the boron coating film under the optimized condition has been achieved to be 0.94.

Oyaidzu, M.; Yoshikawa, A.; Kodama, H.; Oya, Y.; Sagara, A.; Noda, N.; Okuno, K.

2005-05-01

156

Impact of roadside noise barriers on particle size distributions and pollutants concentrations near freeways  

NASA Astrophysics Data System (ADS)

Increasing epidemiological evidence has established an association between a host of adverse health effects and exposure to ambient particulate matter (PM) and co-pollutants, especially those emitted from motor vehicles. Although PM and their co-pollutants dispersion profiles near the open freeway have been extensively characterized by means of both experimental measurements and numerical simulations in recent years, such investigations near freeways with roadside barriers have not been well documented in the literature. A few previous studies suggested that the presence of roadside structures, such as noise barriers and vegetation, may impact the decay of pollutant concentrations downwind of the freeway by limiting the initial dispersion of traffic emissions and increasing their vertical mixing due to the upward deflection of airflow. Since the noise barriers are now common roadside features of the freeways, particularly those running through populated urban areas, it is pertinent to investigate the impact of their presence on the particles and co-pollutants concentrations in areas adjacent to busy roadways. This study investigated two highly trafficked freeways (I-710 and I-5) in Southern California, with two sampling sites for each freeway, one with and the other without the roadside noise barriers. Particle size distributions and co-pollutants concentrations were measured in the immediate proximity of freeways and at different distances downwind of the freeways. The results showed the formation of a "concentration deficit" zone in the immediate vicinity of the freeway with the presence of roadside noise barrier, followed by a surge of pollutant concentrations further downwind at 80-100 m away from freeway. The particle and co-pollutants concentrations reach background levels at farther distances of 250-400 m compared to 150-200 m at the sites without roadside noise barriers.

Ning, Zhi; Hudda, Neelakshi; Daher, Nancy; Kam, Winnie; Herner, Jorn; Kozawa, Kathleen; Mara, Steven; Sioutas, Constantinos

2010-08-01

157

The influence of Saffman lift force on nanoparticle concentration distribution near a wall  

NASA Astrophysics Data System (ADS)

The lift force on a spherical nanoparticle near a wall in micro/nanofluidics has not received sufficient attention so far. In this letter the concentration of ?200 nm particles is measured at 0.25-2.0 ?m to a wall in a microchannel with pressure-driven de-ionized water flow (pressure gradient 0-2000 kPa/m). The measured data show the influence of the lift force on the nanoparticle concentration distribution. By introducing the Saffman lift force into the Nernst-Planck equation near a wall, we find that the lift force is dominant at the range of 2

Zheng, Xu; Silber-Li, Zhanhua

2009-09-01

158

Specificity Study on Concentration of Monoamine Transmitters at Acupoint and Effect of Acupuncture on Its Distribution  

PubMed Central

To investigate the distribution of monoamine transmitters at acupoints and effect of acupuncture on it. Take this experiment by means of microdialysis. Twenty rabbits were randomly assigned to two groups (Group A: acupuncture Guanyuan (RN4), Group B: acupuncture nonacupoint which is besides Guanyuan (RN4) 1?cm). Before and after acupuncture was taken, tissue fluids both at Zhongwan (RN12) which is on the same meridian as Guanyuan and at a nonacupoint 1?cm away from Zhongwan were collected through microdialysis, respectively. The collected samples were analyzed to determine concentrations of monoamine transmitters. Epinephrine and 5-HT were detected. An unknown substance was found. Its concentration at acupoint was significantly higher than that at nonacupoint and decreased after acupuncture. Its significant specificity at acupoints suggests that it may play an important role in meridian's activity.

Guo, Yi

2014-01-01

159

Concentration and Spatial Distribution of Polycyclic Aromatic Hydrocarbons in Surface Roadside Soils, Shanghai  

NASA Astrophysics Data System (ADS)

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that may lead to mutagenesis, carcinogenesis or teratogenesis. Vehicular traffic pollution is one of the important sources for PAHs in soils. Concentrations of 19 PAHs were detected in soils along nine roads in Shanghai by automatic Soxhlet extraction and high performance liquid chromatography. Concentration and spatial distribution of PAHs in surface soils beside nine target roads in Shanghai were investigated and a preliminary migration regularity of PAHs was proposed based on data analysis of Cheting Highway (NO.320 Chinese National Highway). The result showed that the total concentrations of PAHs in the target roadside soils ranged from undetectable to 34.6?g/g-dw, with a mean of 7.77?g/g-dw. In comparison with the level of PAHs in urban or suburban roadside soils, the results showed significantly that ? PAHs concentration in roadside soils inside industrial areas was higher. The study on the migration regularity of PAHs in soils along roads demonstrated that surface runoff had a more significant effect on the PAHs transportation than air-borne transportation.

Pan, Zhaoyu; Liu, Ying; He, Yao; Chen, Ling

2010-11-01

160

Boron as a tracer of aerosol from combustion of coal  

NASA Astrophysics Data System (ADS)

Atmospheric boron was found to be predominantly gaseous in ambient samples and in stacks of coal-fired power plants. Typical gas/particulate ratios ranged from 20 to more than 100, with stack ratios above 100 and ambient ratios generally below 100. In the stacks, B/SO2 ratios were lower than expected from bulk U.S. coals, consistent with volatilization of 20-80 percent of the boron during combustion. Midwestern ambient B/SO2 ratios were at or above stack values, with the lowest ratios associated with highest concentrations. SO2 was always more variable than gaseous boron. These observations are consistent with coal combustion as the major source of atmospheric boron (and SO2) in the Midwest. In northern Vermont, concentrations of gaseous boron and SO2 were several times lower than in the Midwest, but the B/SO2 ratio was several times higher. Both species passed through quasiweekly in-phase cycles of concentration with the relative amplitudes being greater for SO2 than for gaseous boron. All major pulses of boron and SO2 came from the direction of the Midwest, on the backsides of high-pressure areas. Since the ocean is also a source of gaseous boron, its anthropogenic tracer potential for acid deposition studies will be most useful in the interior of continents.

Fogg, Thomas R.; Rahn, Kenneth A.

1984-09-01

161

The suspended sediment concentration distribution in the Bohai Sea, Yellow Sea and East China Sea  

NASA Astrophysics Data System (ADS)

The distribution of the suspended sediment concentration (SSC) in the Bohai Sea, Yellow Sea and East China Sea (BYECS) is studied based on the observed turbidity data and model simulation results. The observed turbidity results show that (i) the highest SSC is found in the coastal areas while in the outer shelf sea areas turbid water is much more difficult to observe, (ii) the surface layer SSC is much lower than the bottom layer SSC and (iii) the winter SSC is higher than the summer SSC. The Regional Ocean Modeling System (ROMS) is used to simulate the SSC distribution in the BYECS. A comparison between the modeled SSC and the observed SSC in the BYECS shows that the modeled SSC can reproduce the principal features of the SSC distribution in the BYECS. The dynamic mechanisms of the sediment erosion and transport processes are studied based on the modeled results. The horizontal distribution of the SSC in the BYECS is mainly determined by the current-wave induced bottom stress and the fine-grain sediment distribution. The current-induced bottom stress is much higher than the wave-induced bottom stress, which means the tidal currents play a more significant role in the sediment resuspension than the wind waves. The vertical mixing strength is studied based on the mixed layer depth and the turbulent kinetic energy distribution in the BYECS. The strong winter time vertical mixing, which is mainly caused by the strong wind stress and surface cooling, leads to high surface layer SSC in winter. High surface layer SSC in summer is restricted in the coastal areas.

Bian, Changwei; Jiang, Wensheng; Greatbatch, Richard J.; Ding, Hui

2013-09-01

162

Parameterization of Buoyancy Effects in Generic PWR Boron Dilution Scenarios  

SciTech Connect

A computational investigation is undertaken into the role of buoyancy in a PWR boron dilution transient following a postulated Small Break Loss of Coolant Accident (SB-LOCA). In the scenario envisaged there is flow of de-borated and relatively high temperature water from a single cold leg into the downcomer; flow rates are typical of natural circulation conditions. The study focuses upon the development of boron concentration distributions in the downcomer and adopts a 3D-unsteady formulation of the mean flow equations in combination with the standard high-Reynolds-number k-{epsilon} turbulence model. It is found that the Richardson number (Ri = Gr/Re{sup 2}) is the most important group parameterizing the course of a concentration transient. At Ri values characterizing a 'baseline' scenario the results indicate that there is a stable, circumferentially-uniform, descent through the downcomer of a stratified region of low-borated fluid. Qualitatively the same behaviour is found at higher Richardson number, although at Ri values of approximately one-fifth the baseline level there is evidence of large-scale mixing and a consequent absence of concentration stratification. (authors)

Galindo-Garcia, Ivan F.; Cotton, Mark A.; Axcell, Brian P. [University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

2006-07-01

163

Spatial and temporal distribution of pesticide air concentrations in Canadian agricultural regions  

NASA Astrophysics Data System (ADS)

The Canadian Pesticide Air Sampling Campaign was initiated in 2003 to assess atmospheric levels of pesticides, especially currently used pesticides (CUPs) in agricultural regions across Canada. In the first campaign during the spring to summer of 2003, over 40 pesticides were detected. The spatial and temporal distribution of pesticides in the Canadian atmosphere was shown to reflect the pesticide usage in each region. Several herbicides including triallate, bromoxynil, MCPA, 2,4-D, dicamba, trifluralin and ethalfluralin were detected at highest levels at Bratt's Lake, SK in the prairie region. Strong relationships between air concentrations and dry depositions were observed at this site. Although no application occurred in the Canadian Prairies in 2003, high air concentrations of lindane ( ?-hexachlorocyclohexane) were still observed at Bratt's Lake and Hafford, SK. Two fungicides (chlorothalonil and metalaxyl) and two insecticides (endosulfan and carbofuran) were measured at highest levels at Kensington, PEI. Maximum concentrations of chlorpyrifos and metolachlor were found at St. Anicet, QC. The southern Ontario site, Egbert showed highest concentration of alachlor. Malathion was detected at the highest level at the west coast site, Abbotsford, BC. In case of legacy chlorinated insecticides, high concentrations of DDT, DDE and dieldrin were detected in British Columbia while ?-HCH and HCB were found to be fairly uniform across the country. Chlordane was detected in Ontario, Québec and Prince Edward Island. This study demonstrates that the sources for the observed atmospheric occurrence of pesticides include local current pesticide application, volatilization of pesticide residues from soil and atmospheric transport. In many instances, these data represent the first measurements for certain pesticides in a given part of Canada.

Yao, Yuan; Tuduri, Ludovic; Harner, Tom; Blanchard, Pierrette; Waite, Don; Poissant, Laurier; Murphy, Clair; Belzer, Wayne; Aulagnier, Fabien; Li, Yi-Fan; Sverko, Ed

164

Droplet Size Distributions as a function of rainy system type and Cloud Condensation Nuclei concentrations  

NASA Astrophysics Data System (ADS)

This work aims to study typical Droplet Size Distributions (DSDs) for different types of precipitation systems and Cloud Condensation Nuclei concentrations over the Vale do Paraíba region in southeastern Brazil. Numerous instruments were deployed during the CHUVA (Cloud processes of tHe main precipitation systems in Brazil: a contribUtion to cloud resolVing modeling and to the GPM) Project in Vale do Paraíba campaign, from November 22, 2011 through January 10, 2012. Measurements of CCN (Cloud Condensation Nuclei) and total particle concentrations, along with measurements of rain DSDs and standard atmospheric properties, including temperature, pressure and wind intensity and direction, were specifically made in this study. The measured DSDs were parameterized with a gamma function using the moment method. The three gamma parameters were disposed in a 3-dimensional space, and subclasses were classified using cluster analysis. Seven DSD categories were chosen to represent the different types of DSDs. The DSD classes were useful in characterizing precipitation events both individually and as a group of systems with similar properties. The rainfall regime classification system was employed to categorize rainy events as local convective rainfall, organized convection rainfall and stratiform rainfall. Furthermore, the frequencies of the seven DSD classes were associated to each type of rainy event. The rainfall categories were also employed to evaluate the impact of the CCN concentration on the DSDs. In the stratiform rain events, the polluted cases had a statistically significant increase in the total rain droplet concentrations (TDCs) compared to cleaner events. An average concentration increase from 668 cm- 3 to 2012 cm- 3 for CCN at 1% supersaturation was found to be associated with an increase of approximately 87 m- 3 in TDC for those events. For the local convection cases, polluted events presented a 10% higher mass weighted mean diameter (Dm) on average. For the organized convection events, no significant results were found.

Cecchini, Micael A.; Machado, Luiz A. T.; Artaxo, Paulo

2014-06-01

165

The structure of boron in boron fibres  

NASA Technical Reports Server (NTRS)

The structure of noncrystalline, chemically vapour-deposited boron fibres was investigated by computer modelling the experimentally obtained X-ray diffraction patterns. The diffraction patterns from the models were computed using the Debye scattering equation. The modelling was done utilizing the minimum nearest-neighbour distance, the density of the model, and the broadening and relative intensity of the various peaks as boundary conditions. The results suggest that the fibres consist of a continuous network of randomly oriented regions of local atomic order, about 2 nm in diameter, containing boron atoms arranged in icosahedra. Approximately half of these regions have a tetragonal structure and the remaining half a distorted rhombohedral structure. The model also indicates the presence of many partial icosahedra and loose atoms not associated with any icosahedra. The partial icosahedra and loose atoms indicated in the present model are in agreement with the relaxing sub-units which have been suggested to explain the anelastic behavior of fibre boron and the loosely bound boron atoms which have been postulated to explain the strengthening mechanism in boron fibres during thermal treatment.

Bhardwaj, J.; Krawitz, A. D.

1983-01-01

166

In vivo evaluation of the boronated porphyrin TABP-1 in U-87 MG intracerebral human glioblastoma xenografts.  

PubMed

Boron neutron capture therapy (BNCT) is an adjuvant therapy that has the potential to control local tumor growth. A selective delivery of sufficient amounts of boron to individual tumor cells, compared to surrounding normal tissues, is the key for successful BNCT. We have designed and synthesized a new highly water-soluble boronated porphyrin, TABP-1, as a possible BNCT agent. When we injected the maximum tolerated dose (MTD: 15 mg/kg) of TABP-1 systemically into the tail vein of athymic rats bearing intracerebral (i.c.) human glioblastoma U-87 MG xenografts, the compound accumulated preferentially in brain tumors compared to normal brain; however, the level of boron in the tumors was less than the 30 microg/g of tissue that is generally considered necessary for BNCT. We next investigated whether convection-enhanced delivery (CED) could improve the boron distribution. The compound was administered directly into i.c. tumors using an osmotic minipump attached to a brain-infusion cannula. TABP-1 doses from 0.25 to 1.0 mg infused locally over 24 h produced tumor boron concentrations greater than those obtained by systemic administration at the MTD. For example, CED administration of 0.5 mg of TABP-1 produced a tumor boron level of 65.4 microg/g of tumor, whereas the serum level was only 0.41 microg/g (tumor to serum ratio of approximately 160:1). CED also produced relatively high tumor to normal brain ratios of approximately 5:1 for ipsilateral brain and approximately 26:1 for contralateral brain tissues at the 0.5 mg dose. Thus, we may be able to achieve therapeutic BNCT efficacy with minimal systemic toxicity or radiation-induced damage to normal tissue by administering TABP-1 using CED. PMID:16026007

Ozawa, Tomoko; Santos, Raquel A; Lamborn, Kathleen R; Bauer, William F; Koo, Myoung-Seo; Kahl, Stephen B; Deen, Dennis F

2004-01-01

167

Distribution of Genetic Marker Concentrations for Fecal Indicator Bacteria in Sewage and Animal Feces  

PubMed Central

Very little is known about the density and distribution of fecal indicator bacteria (FIB) genetic markers measured by quantitative real-time PCR (qPCR) in fecal pollution sources. Before qPCR-based FIB technologies can be applied to waste management and public health risk applications, it is vital to characterize the concentrations of these genetic markers in pollution sources (i.e., untreated wastewater and animal feces). We report the distribution of rRNA genetic markers for several general FIB groups, including Clostridium spp., Escherichia coli, enterococci, and Bacteroidales, as determined by qPCR on reference collections consisting of 54 primary influent sewage samples collected from treatment facilities across the United States and fecal samples representing 20 different animal species. Based on raw sewage sample collection data, individual FIB genetic markers exhibited a remarkable similarity in concentration estimates from locations across the United States ranging from Hawaii to Florida. However, there was no significant correlation between genetic markers for most FIB combinations (P > 0.05). In addition, large differences (up to 5 log10 copies) in the abundance of FIB genetic markers were observed between animal species, emphasizing the importance of indicator microorganism selection and animal source contribution for future FIB applications. PMID:22504809

Kelty, Catherine A.; Varma, Manju; Sivaganesan, Mano; Haugland, Richard A.

2012-01-01

168

Uranium concentration and distribution in six peridotite inclusions of probable mantle origin  

NASA Technical Reports Server (NTRS)

Fission-track activation was used to investigate uranium concentration and distribution in peridotite inclusions in alkali basalt from six localities. Whole-rock uranium concentrations range from 24 to 82 ng/g. Most of the uranium is uniformly distributed in the major silicate phases - olivine, orthopyroxene, and clinopyroxene. Chromian spinels may be classified into two groups on the basis of their uranium content - those which have less than 10 ng/g and those which have 100 to 150 ng/g U. In one sample accessory hydrous phases, phlogopite and hornblende, contain 130 and 300 ng/g U, respectively. The contact between the inclusion and the host basalt is usually quite sharp. Glassy or microcrystalline veinlets found in some samples contain more than 1 microgram/g. Very little uranium is associated with microcrystals of apatite. These results agree with some earlier investigators, who have concluded that suboceanic peridotites contain too little uranium to account for normal oceanic heat flow by conduction alone.

Haines, E. L.; Zartman, R. E.

1973-01-01

169

Uranium concentration and distribution in six peridotite inclusions of probable mantle origin  

USGS Publications Warehouse

Fission-track activation was used to investigate uranium concentration and distribution in peridotite inclusions in alkali basalt from six localities. Whole-rock uranium concentrations range from 24 to 82 ng/g (1 ng = 10-9 g). Most of the uranium is uniformly distributed in the major silicate phases - olivine, orthopyroxene, and clinopyroxene. Chromian spinels may be classified into two groups on the basis of their uranium content, having either less than 10 ng/g or 100-150 ng/g U. In one sample accessory hydrous phases, phlogopite and hornblende, contain 130 and 300 ng/g U, respectively. The contact between the inclusion and the host basalt is usually quite sharp. Glassy or microcrystalline veinlets found in some samples contain more than 1??g/g (1 ??g = 10-6 g). Very little uranium is associated with microcrystals of apatite. Our results agree with some earlier investigators, who have concluded that suboceanic peridotites contain too little uranium to account for normal oceanic heat flow by conduction alone. ?? 1973.

Haines, E.L.; Zartman, R.E.

1973-01-01

170

Middle East measurements of concentration and size distribution of aerosol particles for coastal zones  

NASA Astrophysics Data System (ADS)

Recently, an extension of the Navy Aerosol Model (NAM) was proposed based on analysis of an extensive series of measurements at the Irish Atlantic Coast and at the French Mediterranean Coast. We confirm the relevance of that work for the distant eastern Meditteranean and extend several coefficients of that coastal model, proposed by Piazzola et al. for the Meditteranean Coast (a form of the Navy Aerosol Model), to midland Middle East coastal environments. This analysis is based on data collected at three different Middle East coastal areas: the Negev Desert (Eilat) Red Sea Coast, the Sea of Galilee (Tiberias) Coast, and the Mediterranean (Haifa) Coast. Aerosol size distributions are compared with those obtained through measurements carried out over the Atlantic, Pacific, and Indian Ocean Coasts, and Mediterranean, and Baltic Seas Coasts. An analysis of these different results allows better understanding of the similarities and differences between different coastal lake, sea, and open ocean zones. It is shown that in the coastal regions in Israel, compared to open ocean and other sea zones, larger differences in aerosol particle concentration are observed. The aerosol particle concentrations and their dependences on wind speed for these coastal zones are analyzed and discussed. We propose to classify the aerosol distribution models to either: 1. a coastal model with marine aerosol domination; 2. a coastal model with continental aerosol domination (referred to as midland coast in this work); or 3. a coastal model with balanced marine and continental conditions.

Bendersky, Sergey; Kopeika, Norman S.; Blaunstein, Natan S.

2005-10-01

171

Evolution of root plasticity responses to variation in soil nutrient distribution and concentration  

PubMed Central

Root plasticity, a trait that can respond to selective pressure, may help plants forage for nutrients in heterogeneous soils. Agricultural breeding programs have artificially selected for increased yield under comparatively homogeneous soil conditions, potentially decreasing the capacity for plasticity in crop plants like barley (Hordeum vulgare). However, the effects of domestication on the evolution of root plasticity are essentially unknown. Using a split container approach, we examined the differences in root plasticity among three domestication levels of barley germplasm (wild, landrace, and cultivar) grown under different concentrations and distribution patterns of soil nutrients. Domestication level, nutrient concentration, and nutrient distribution interactively affected average root diameter; differential root allocation (within-plant plasticity) was greatest in wild barley (Hordeum spontaneum), especially under low nutrient levels. Correlations of within-plant root plasticity and plant size were most pronounced in modern cultivars under low-nutrient conditions. Barley plants invested more resources to root systems when grown in low-nutrient soils and allocated more roots to higher-nutrient locations. Root plasticity in barley is scale dependent and varies with domestication level. Although wild barley harbors a greater capacity for within-plant root plasticity than domesticated barley, cultivars exhibited the greatest capacity to translate within-plant plasticity into increased plant size. PMID:23346229

Grossman, Judah D; Rice, Kevin J

2012-01-01

172

Effects of Established Hypolipidemic Drugs on HDL Concentration, Subclass Distribution, and Function.  

PubMed

The knowledge of an inverse relationship between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and rates of cardiovascular disease has led to the concept that increasing plasma HDL-C levels would be protective against cardiovascular events. Therapeutic interventions presently available to correct the plasma lipid profile have not been designed to specifically act on HDL, but have modest to moderate effects on plasma HDL-C concentrations. Statins, the first-line lipid-lowering drug therapy in primary and secondary cardiovascular prevention, have quite modest effects on plasma HDL-C concentrations (2-10 %). Fibrates, primarily used to reduce plasma triglyceride levels, also moderately increase HDL-C levels (5-15 %). Niacin is the most potent available drug in increasing HDL-C levels (up to 30 %), but its use is limited by side effects, especially flushing.The present chapter reviews the effects of established hypolipidemic drugs (statins, fibrates, and niacin) on plasma HDL-C levels and HDL subclass distribution, and on HDL functions, including cholesterol efflux capacity, endothelial protection, and antioxidant properties. PMID:25523003

Gomaraschi, Monica; Adorni, Maria Pia; Banach, Maciej; Bernini, Franco; Franceschini, Guido; Calabresi, Laura

2015-01-01

173

3D-Simulation Of Concentration Distributions Inside Large-Scale Circulating Fluidized Bed Combustors  

NASA Astrophysics Data System (ADS)

With increasing size of modern CFB combustors the lateral mixing of fuels and secondary air gains more and more importance. Strong concentration gradients, which result from improper lateral mixing, can lead to operational problems, high flue gas emissions and lower boiler efficiencies. A 3D-model for the simulation of local gas and solids concentrations inside industrial-sized CFB boilers has been developed. The model is based on a macroscopic approach and considers all major mechanisms during fuel spreading and subsequent combustion of char and volatiles. Typical characteristics of modern boilers like staged combustion, a smaller cross-sectional area in the lower section of the combustion chamber and the co-combustion of additional fuels with coal can be considered. The 252 MWth combustor of Stadtwerke Duisburg AG is used for the validation of the model. A comprehensive picture of the local conditions inside the combustion chamber is achieved by the combination of local gas measurements and the three-dimensional simulation of concentration distributions.

Wischnewski, R.; Ratschow, L.; Hartge, E. U.; Werthe, J.

174

Effect of solids concentration distribution on the flue gas desulfurization process  

SciTech Connect

A dry flue gas desulfurization (FGD) process at 600-800{sup o}C was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. Various fresh sorbent distribution types and internal structures were modeled numerically to investigate their effect on the gas-solid flow and sulfate reaction characteristics. Experimental results show that, after the fresh sorbent supply was stopped, the desulfurization efficiency declined rapidly even though the sorbent recirculation was maintained. Therefore, the fresh sorbent is the main contributor to the desulfurization process and the primary effect of the recirculated sorbent was to evenly distribute the fresh sorbent and to prolong the sorbent particle residence time. The numerical results demonstrate that the desulfurization efficiency varied greatly for the various fresh sorbent bottom injection methods. The desulfurization efficiency of the bottom-even injection method was 1.5 times that of the bottom two-sided injection method. Internal structures effectively improved the fresh sorbent solids concentration distribution and the desulfurization efficiency. Optimized internal structures increased the desulfurization efficiency of the bottom two-sided injection method by 46%, so that it was very close to that of the bottom-even injection method with only a 4.6% difference. 16 refs., 6 figs., 2 tabs.

Jie Zhang; Changfu You; Haiying Qi; Changhe Chen; Xuchang Xu [Tsinghua University, Beijing (China). Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education, Department of Thermal Engineering

2006-06-15

175

Beyond phthalates: gas phase concentrations and modeled gas/particle distribution of modern plasticizers.  

PubMed

The ongoing health debate about polymer plasticizers based on the esters of phthalic acid, especially di(2-ethylhexyl) phthalate (DEHP), has caused a trend towards using phthalates of lower volatility such as diisononyl phthalate (DINP) and towards other acid esters, such as adipates, terephthalates, citrates, etc. Probably the most important of these so-called "alternative" plasticizers is diisononyl cyclohexane-1,2-dicarboxylate (DINCH). In the indoor environment, the continuously growing market share of this compound since its launch in 2002 is inter alia apparent from the increasing concentration of DINCH in settled house dust. From the epidemiological point of view there is considerable interest in identifying how semi-volatile organic compounds (SVOCs) distribute in the indoor environment, especially in air, airborne particles and sedimented house dust. This, however, requires reliable experimental concentration data for the different media and good measurements or estimates of their physical and chemical properties. This paper reports on air concentrations for DINP, DINCH, diisobutyl phthalate (DIBP), diisobutyl adipate (DIBA), diisobutyl succinate (DIBS) and diisobutyl glutarate (DIBG) from emission studies in the Field and Laboratory Emission Cell (FLEC). For DINP and DINCH it took about 50 days to reach the steady-state value: for four months no decay in the concentration could be observed. Moreover, vapor pressures p(0) and octanol-air partitioning coefficients K(OA) were obtained for 37 phthalate and non-phthalate plasticizers from two different algorithms: EPI Suite and SPARC. It is shown that calculated gas/particle partition coefficients K(p) and fractions can widely differ due to the uncertainty in the predicted p(0) and K(OA) values. For most of the investigated compounds reliable experimental vapor pressures are not available. Rough estimates can be obtained from the measured emission rate of the pure compound in a microchamber as is shown for di-n-butyl phthalate (DnBP), di(2-ethylhexyl) adipate(DEHA), tri(octyl) trimellitate (TOTM) and DEHP. PMID:21764421

Schossler, Patrícia; Schripp, Tobias; Salthammer, Tunga; Bahadir, Müfit

2011-09-01

176

Characteristics of inhalable particulate matter concentration and size distribution from power plants in China  

SciTech Connect

The collection efficiency of particulate emission control devices (PECDs), particulate matter (PM) emissions, and PM size distribution were determined experimentally at the inlet and outlet of PECDs at five coal-fired power plants. Different boilers, coals, and PECDs are used in these power plants. Measurement in situ was performed by an electrical low-pressure impactor with a sampling system, which consisted of an isokinetic sampler probe, precut cyclone, and two- stage dilution system with a sample line to the instruments. The size distribution was measured over a range from 0.03 to 10 {mu}m. Before and after all of the PECDs, the particle number size distributions display a bimodal distribution. The PM2.5 fraction emitted to atmosphere includes a significant amount of the mass from the coarse particle mode. The controlled and uncontrolled emission factors of total PM, inhalable PM (PM10), and fine PM (PM2.5) were obtained. Electrostatic precipitator (ESP) and baghouse total collection efficiencies are 96.38 99.89% and 99.94%, respectively. The minimum collection efficiency of the ESP and the baghouse both appear in the particle size range of 0.1 1 0 {mu}m. In this size range, ESP and baghouse collection efficiencies are 85.79 98.6% and 99.54%. Real- time measurement shows that the mass and number concentration of PM10 will be greatly affected by the operating conditions of the PECDs. The number of emitted particles increases with increasing boiler load level because of higher combustion temperature. During test run periods, the data reproducibility is satisfactory. 19 refs., 11 figs., 6 tabs.

Honghong Yi; Jiming Hao; Lei Duan; Xinghua Li; Xingming Guo [Tsinghua University, Beijing (China). Department of Environmental Science and Engineering

2006-09-15

177

Boron enrichment in martian clay.  

PubMed

We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest mineralogy by plate tectonics, we suggest that the conditions for prebiotic ribose synthesis may be better understood by further Mars exploration. PMID:23762242

Stephenson, James D; Hallis, Lydia J; Nagashima, Kazuhide; Freeland, Stephen J

2013-01-01

178

On maximum likelihood estimation of the concentration parameter of von Mises-Fisher distributions.  

PubMed

Maximum likelihood estimation of the concentration parameter of von Mises-Fisher distributions involves inverting the ratio [Formula: see text] of modified Bessel functions and computational methods are required to invert these functions using approximative or iterative algorithms. In this paper we use Amos-type bounds for [Formula: see text] to deduce sharper bounds for the inverse function, determine the approximation error of these bounds, and use these to propose a new approximation for which the error tends to zero when the inverse of [Formula: see text] is evaluated at values tending to [Formula: see text] (from the left). We show that previously introduced rational bounds for [Formula: see text] which are invertible using quadratic equations cannot be used to improve these bounds. PMID:25309045

Hornik, Kurt; Grün, Bettina

2014-01-01

179

Wild-type minimal inhibitory concentration distributions in bacteria of animal origin in Argentina.  

PubMed

The aim of this study was to determine the antimicrobial resistance profiles of indicator bacteria isolated from domestic animal feces. Minimal inhibitory concentration (MIC) was determined by agar dilution. Interpretative criteria on the basis of wild-type MIC distributions and epidemiological cutoff values (ECOFF or ECV) were used according to the 'European Committee on Antimicrobial Susceptibility Testing' (EUCAST) data. Results from 237 isolates of Escherichia coli showed reduced susceptibility for ampicillin, streptomycin and tetracycline, the antimicrobials commonly used in intensive breeding of pigs and hens. Regarding all the species of the genus Enterococcus spp., there are only ECOFF or ECV for vancomycin. Of the 173 Enterococcus spp. isolated, only one showed reduced susceptibility to vancomycin and was classified as 'non-wild-type' (NWT) population. This is the first report in Argentina showing data of epidemiological cutoff values in animal bacteria. PMID:24721272

Pantozzi, Florencia L; Ibar, Mariela P; Nievas, Victorio F; Vigo, Germán B; Moredo, Fabiana A; Giacoboni, Gabriela I

2014-01-01

180

Suspended sediment concentration and particle size distribution, and their relationship with heavy metal content  

NASA Astrophysics Data System (ADS)

This paper aims at assessing the feasibility of suspended sediment concentration (SSC) estimation by using predictor variables of heavy metal concentration (HMC, viz., iron, chromium, zinc and nickel) transported in solution and solid. The study was conducted in the Research and Educational Forest Watershed of the Tarbiat Modares University (Kojour) which comprises an area of ca. 50000 ha. For this study, suspended sediment samples were collected from the left bank of the Kojour River twice a week, as well as during runoff events from November 2007 to June 2008. The samples were then prepared through direct digestion and finally analyzed by atomic absorption spectrophotometry (AAS). The relationship between SSC and particle size distribution (PSD) were correlated with HMC by using bivariate and multivariate regression models. Proposed models were then selected based on statistical criteria. The results showed high correlation between dissolved and particulate chromium content with efficiency coefficients beyond 77% ( P < 0.001). However, a lower relationship was found between SSC and nickel content. From these results, it is clearly shown that the HMC can practically be estimated by SSC in watersheds with different accuracy and vice versa. It is also understood that heavy metal pollution can be easily managed by controlling SSC.

Sadeghi, S. H. R.; Harchegani, M. Kiani; Younesi, H. A.

2012-02-01

181

Degenerate crystalline silicon films by aluminum-induced crystallization of boron-doped amorphous silicon  

NASA Astrophysics Data System (ADS)

Degenerate p-type crystalline silicon film with a hole concentration of 4 × 1021 cm-3 was investigated using aluminum-induced crystallization (AIC) of boron-doped amorphous silicon (a-Si). The AIC mechanism is different from that in the undoped AIC-Si. Boron atoms accumulate at Al layer forming a boron bump and segregate the Al atoms into Si layer, resulting to the formation of AlSi alloy. The degeneracy is not attributed to boron doping but instead to the AlSi alloy. Observations show that Al and Si layer transfer occurs not at original interface of Al and Si, but at the boron bump.

Hwang, J. D.; Luo, L. C.; Hsueh, T. J.; Hwang, S. B.

2012-10-01

182

The Cloud and Autonomic Computing Center concentrates on topics in advanced distributed computing as part of the National Science Foundation  

E-print Network

The Cloud and Autonomic Computing Center concentrates on topics in advanced distributed program. The Cloud and Autonomic Computing Center at Texas Tech University (CAC@TTU) provides expertise in cloud security and standards, machine learning, data mining, parallel and distributed computing

Rock, Chris

183

Boron alloying of GaN  

NASA Astrophysics Data System (ADS)

The III-V semiconductor GaN has received considerable attention due to its wide band gap. Using LDA calculations, we studied the effects of boron incorporation in GaN (zincblende). Lattice parameters and band gap energies for B_xGa_1-xN supercells were computed. For small boron concentrations, the GaN band gap increased slightly and a band gap bowing parameter was determined. Strain energy calculations were also performed to determine whether boron incorporation could resolve the lattice mismatch in wide band gap semicounductor alloys. Formation enthalpies of B_xGa_1-xN, B_xGa_1-xAs, and GaAs_1-xNx were compared.

Escalanti, Laurian; Hart, Gus L. W.

2003-03-01

184

The impact of plasma triglyceride and apolipoproteins concentrations on high-density lipoprotein subclasses distribution  

PubMed Central

Objective To investigate the effect of triglyceride (TG) integrates with plasma major components of apolipoproteins in HDL subclasses distribution and further elicited the TG-apolipoproteins (apos) interaction in the processes of high density lipoprotein (HDL) mature metabolic and atherosclerosis related diseases. Methods Contents of plasma HDL subclasses were quantities by two-dimensional gel electrophoresis associated with immunodetection in 500 Chinese subjects. Results Contents of pre?1-HDL, HDL3a, and apoB-100 level along with apoB-100/A-I ratio were significantly increased, whereas there was a significant reduction in the contents of HDL2, apoA-I level as well as apoC-III/C-II ratio with increased TG concentration. Moreover, pre?1-HDL contents is elevated about 9 mg/L and HDL2b contents can be reduced 21 mg/L for 0.5 mmol/L increment in TG concentration. Moreover, with increase of apoA-I levels, HDL2b contents were marginally elevated in any TG concentration group. Furthermore, despite of in the apoB-100/A-I < 0.9 group, the contents of pre?1-HDL increased, and those of HDL2b decreased significantly for subjects in both high and very high TG levels compared to that in normal TG levels. Similarly, in the apoB-100/A-I ? 0.9 group, the distribution of HDL subclasses also showed abnormality for subjects with normal TG levels. Conclusions The particle size of HDL subclasses tend to small with TG levels increased which indicated that HDL maturation might be impeded and efficiency of reverse cholesterol transport(RCT) might be weakened. These data suggest that TG levels were not only significantly associated with but liner with the contents of pre?1-HDL and HDL2b. They also raise the possibility that the TG levels effect on HDL maturation metabolism are subjected to plasma apolipoproteins and apolipoproteins ratios. PMID:21251287

2011-01-01

185

Concentration and distribution of heavy metals in two Andisols of the Azuay Andes (Ecuador)  

NASA Astrophysics Data System (ADS)

At present many governmental and environmental bureaus are interested in establishing reliable soil quality criteria for heavy metals to enable the detection of polluted sites. To evaluate the variation of heavy metal natural concentration and to assess heavy metal contamination in soils, it is necessary to survey heavy metal baseline levels in order to understand their migration and distribution during pedogenesis. Many nationwide projects report elemental baseline values in soils. Baseline levels of heavy metals in soils have also been determined at local scales. Data is scarce on qualitative and quantitative trace elements content of Ecuatorian soils. The soils in the Azuay Andes (S of Ecuador) are thought to be generally non-contaminated. The objective of this study is to determine and evaluate the natural concentrations and distribution of seven heavy metals (Cd, Co, Cr, Cu, Ni, Pb and Zn) in Andisol of Azuay Andes. Soil samples were grounded in an agate mill prior to pseudototal heavy metal analysis. Cadmium, Co, Cr, Cu, Ni, Pb and Zn were determined by a masses spectrometer (MS-ICP) after aqua regia extraction according to ISO standard procedures. Soil particle size distribution, organic carbon, electrical conductivity and pH have been previously determined. Andisols are dominated by amorphous aluminium silicates and Al-organic complexes. The soils of volcanic area usually have an Ah-Bh-Bhs/Bw-C horizon sequence. The Ah horizon is dark-coloured and normally very high in organic matter, ranging from 6.4 to 15.2 %. A strong rise in pH upon addition of a fluoride solution is used to signal the presence of allophane. The pH usually rises to 10.5 bellow 20 cm. The range of total soil values in mgkg-1 is as follows: Cd (0.03-0.3), Co (0.8-5), Cr (7-15), Cu (9-25), Ni (2-4), Pb (11-41) and Zn (12-37). All heavy metal contents, except for Cd, are strongly correlated with pH. For the pseudototal fraction, there was significant difference between the soil horizons in regards to complex profile development.

Bech, Jaume; Roca, Núria; Ugalde, Sandra; Tonon, Luis; Larriva, Giovani

2013-04-01

186

Statistical approach for the source identification of boron in leachates from industrial landfills  

Microsoft Academic Search

Boron has been found in high concentrations in leachates from landfills located throughout Japan. However, the source(s) of\\u000a boron in the leachates, i.e., what kind of waste(s) releases this element into the leachate, has not been clarified. In this\\u000a study, boron concentrations in leachates from 48 industrial landfills were evaluated, in relation to the categories of waste\\u000a constituting the landfill

Jun Yoshinaga; Akiko Kida; Osami Nakasugi

2001-01-01

187

Boron removal by electrocoagulation and recovery.  

PubMed

This work investigated the removal of boron from wastewater and its recovery by electrocoagulation and hydrothermal mineralization methods respectively. The experimental design was developed using Box-Behnken Model. An initial study was performed based on four preselected variables (pH, current density, concentration and time) using synthetic wastewater. Response surface methodology (RSM) was used to evaluate the effect of process variables and their interaction on boron removal. The optimum conditions were obtained as pH 6.3, current density 17.4 mA/cm(2), and time 89 min. At these applied optimum conditions, 99.7% boron removal from an initial concentration of 10.4 mg/L was achieved. The process was effectively optimized by RSM with a desirability value of 1.0. The results showed that boron removal efficiency enhanced with increase in current density and treatment time. Removal efficiency also increased when pH was increased from 4 to 7 and subsequently decreased at pH 10. Adsorption kinetics study revealed that the reaction followed pseudo second order kinetic model; evidenced by high correlation and goodness of fit. Thermodynamics study showed that mechanism of boron adsorption was chemisorption and the reaction was endothermic in nature. Furthermore, the adsorption process was spontaneous as indicated by negative values of the adsorption free energy. Treatment of real produced water using electrocoagulation resulted in 98% boron removal. The hydrothermal mineralization study showed that borate minerals (Inyoite, Takadaite and Nifontovite) can be recovered as recyclable precipitate from electrocoagulation flocs of produced water. PMID:24412846

Isa, Mohamed Hasnain; Ezechi, Ezerie Henry; Ahmed, Zubair; Magram, Saleh Faraj; Kutty, Shamsul Rahman Mohamed

2014-03-15

188

Boron diffusion in nanocrystalline 3C-SiC  

SciTech Connect

The diffusion of boron in nanocrystalline silicon carbide (nc-SiC) films with a grain size of 4–7 nm is studied using a poly-Si boron source. Diffusion is found to be much faster than in monocrystalline SiC as it takes place within the grain boundary (GB) network. Drive-in temperatures of 900–1000°C are suitable for creating shallow boron profiles up to 100?nm deep, while 1100°C is sufficient to flood the 200?nm thick films with boron. From the resulting plateau at 1100?°C a boron segregation coefficient of 28 between nc-SiC and the Si substrate, as well as a GB boron solubility limit of 0.2?nm{sup ?2} is determined. GB diffusion in the bulk of the films is Fickian and thermally activated with D{sub GB}(T)=(3.1?5.6)×10{sup 7}exp(?5.03±0.16??eV/k{sub B}T) cm{sup 2}s{sup ?1}. The activation energy is interpreted in terms of a trapping mechanism at dangling bonds. Higher boron concentrations are present at the nc-SiC surface and are attributed to immobilized boron.

Schnabel, Manuel, E-mail: manuel.schnabel@ise.fraunhofer.de [Fraunhofer ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Department of Materials, University of Oxford, Parks Rd, Oxford OX1 3PH (United Kingdom); Weiss, Charlotte; Rachow, Thomas; Löper, Philipp; Janz, Stefan [Fraunhofer ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Canino, Mariaconcetta; Summonte, Caterina [CNR-IMM, Via Piero Gobetti 101, 40129 Bologna (Italy); Mirabella, Salvo [CNR-IMM MATIS, Via S. Sofia 64, 95123 Catania (Italy); Wilshaw, Peter R. [Department of Materials, University of Oxford, Parks Rd, Oxford OX1 3PH (United Kingdom)

2014-05-26

189

Boron-Silicon complex defects in GaAs: An ab initio study  

NASA Astrophysics Data System (ADS)

First principles calculations have been performed to investigate defect equilibria of the silicon-boron pair complex (Si-B) in a GaAs matrix. For several charge states, the formation energies were evaluated within the Car-Parrinello scheme considering cation and anion substitutional site defects. The calculations, including the full relaxation of all ionic coordinates, investigate native defects and isolated substitutional silicon (Si) and boron (B) impurities. The obtained formation energies are used to calculate the impurity concentration for different growth conditions. These results can be used to estimate the effect of different thermal profiles on the distribution and electrical state of Si and B defects, which is interesting for classical process simulations.

Leitsmann, R.; Chicker, F.; Plänitz, Ph.; Radehaus, C.; Kretzer, U.; Scheffer-Czygan, M.; Eichler, S.

2011-03-01

190

Carbon and metal concentrations, size distributions and fluxes in major rivers of the Amazon basin  

NASA Astrophysics Data System (ADS)

The chemical composition of the Amazon River results from the mixing of two water types: black water and white water. On-site fractionation by sequential tangential ultrafiltration (STUF) was used to differentiate transported organic carbon and to determine the distribution and association of major and trace elements with different size fraction of the organic carbon (OC). Several sampling campaigns (1994-1996) allow a monthly quantification of particulate (OCP, MeP), colloidal (OCC, MeC) and dissolved (OCD, MeD) organic carbon and metal ions inputs. In white rivers the OC is mainly concentrated in the low molecular weight fraction (OCD < 5000 D) while in black rivers most of the OC is in the heavier molecular weight fractions (OCP and OCC > 5 kDa). For Mg, Ca and K, 50% of the total amount of each element is found in fraction MeD while 15% and 35% are found in fractions MeC and MeP, respectively. Al and Fe are in the particulate fraction at 99% of the total metal concentration for all river samples. This work emphasizes the coagulation processes and the sink for elements in the mixing zone. These physicochemical transformations of the organic matter vary seasonally. The changes happen during the transition periods: before high-level waters and before low-level waters. By way of flux measurement, a seasonal carbon loss was observed. The estimated annual organic carbon flux of the Amazon at Òbidos is 28 × 106 t. At the same time, an average of 9 × 106 t of organic carbon per year is retained in the reach between Manaus and Òbidos, probably via coagulation processes.

Benedetti, Marc F.; Mounier, Stephane; Filizola, Naziano; Benaim, Jean; Seyler, Patrick

2003-05-01

191

On the submicron aerosol distributions and CCN number concentrations in and around the Korean Peninsula  

NASA Astrophysics Data System (ADS)

Total number concentrations of particles having a diameter larger than 10 nm (NCN), cloud condensation nuclei at several supersaturation (S) values (NCCN) and number size distributions of particles with 10-414 nm diameter were measured in Seoul between 2004 and 2010. Overall average values of NCN and geometric mean diameter were 17 811 ± 5581 cm-3 and 48 ± 6 nm. Average NCCN at 0.4, 0.6 and 0.8% S were 4145 ± 2016, 5323 ± 2453 and 6067 ± 2780 cm-3 and corresponding NCCN / NCN were 0.26 ± 0.11, 0.33 ± 0.11 and 0.37 ± 0.12. There is a clear seasonal variation in aerosol concentration, which seems to be due to the monsoon. NCN and NCCN are also found to depend on the volume of traffic and the height of the planetary boundary layer, respectively. During aircraft campaigns in 2009 and 2011, NCN and NCCN at 0.6% S (N0.6%) were measured in and around the Korean Peninsula. During the 2011 campaign, the aerosol scattering coefficient was also measured. NCN and N0.6% in the lower altitudes were generally higher than at higher altitudes, except for cases when particle formation and growth events were thought to occur at higher altitudes. NCN and N0.6% generally show a positive correlation with aerosol scattering coefficients but this correspondence tends to vary with altitude. Occasional instances of low (< 0.3) N0.6% / NCN in the boundary layer are demonstrated to be associated with particle formation and growth events. With the support of ground measurements, it is confirmed that a particle formation and growth event did indeed occur over the Yellow Sea on a flight day, and the areal extent of this event is estimated to be greater than 100 km × 450 km. With the combination of the current and several relevant previous studies, a composite map of NCN and NCCN in and around the Korean Peninsula is produced. Overall, the exhibited concentrations are typical of values measured over polluted regions elsewhere on the globe. Moreover, there is a generally decreasing trend from west to east over the region, implying that the region is constantly under the dominant influence of continental outflow.

Kim, J. H.; Yum, S. S.; Shim, S.; Kim, W. J.; Park, M.; Kim, J.-H.; Kim, M.-H.; Yoon, S.-C.

2014-08-01

192

On the submicron aerosol distributions and CCN number concentrations in and around the Korean Peninsula  

NASA Astrophysics Data System (ADS)

Total number concentrations of particles having diameter larger than 10 nm (NCN), cloud condensation nuclei at several supersaturation (S) values (NCCN), and the number size distribution of particles for 10-414 nm particle diameter range were measured in Seoul between 2004 and 2010. Overall average values of NCN and geometric mean diameter are 17 811 ± 5581 cm-3 and 48 ± 6 nm, respectively. Average NCCN at 0.4, 0.6, and 0.8% S are 4145 ± 2016, 5323 ± 2453 and 6067 ± 2780 cm-3, respectively and corresponding NCCN / NCN are 0.26 ± 0.11, 0.33 ± 0.11 and 0.37 ± 0.12. There is a clear seasonal variation of aerosol concentration, which seems to be due to the monsoon. NCN and NCCN are also found to be dependent on the volume of traffic and the height of planetary boundary layer, respectively. During the two aircraft campaigns in 2009 and 2011, NCN and NCCN at 0.6% S were measured in and around the Korean Peninsula. During the 2011 campaign, aerosol scattering coefficient was also measured. NCN and NCCN 0.6 in the lower altitudes were generally higher than at higher altitudes, except for the cases when particle formation and growth events are thought to occur at higher altitudes. NCN and NCCN 0.6 show generally a positive correlation with aerosol scattering coefficients but its correspondence tends to vary with altitude. Occasional instances of low (< 0.3) NCCN 0.6 / NCN in the boundary layer are demonstrated to be associated with particle formation and growth events. With the support of ground measurements, it is confirmed that a particle formation and growth event indeed occurred on a flight day over the Yellow Sea and the areal extent of the event is estimated to be greater than 100 km × 450 km. With the combination of the current and several relevant previous studies, a composite map of NCN and NCCN in and around the Korean Peninsula is produced. Overall, the exhibited concentrations are typical of the values measured over the polluted regions elsewhere in the globe. Moreover, there is a generally decreasing trend from west to east over the region, implying that the region is constantly under the dominant influence of continental outflow.

Kim, J. H.; Yum, S. S.; Shim, S.; Kim, W. J.; Park, M.; Kim, J.; Kim, M.; Yoon, S. C.

2014-03-01

193

Effects of wall boron coating on FTU plasma operations  

NASA Astrophysics Data System (ADS)

To achieve good performance on FTU in a large density range (0.3-6.0×10 20 m -3), boronization with a mixture of He (90%) and B 2H 6 (10%) (diborane) as the feeding gas has been tested with thermal loads on the limiter surface up to 2.5 MW/m 2. With boronized limiter (TZM alloy with 98% of Mo) and walls (SS AISI 304), the total radiated power drastically drops from 70-90% down to 35-45% and the Zeff decreases from 6.0 to 2.2 at 0.3-0.4×10 20 m -3 related to a strong reduction of heavy-metal concentration and to the getter effect of boron on oxygen (<0.5%). During this phase the action of the boron film as particle reservoir and its quick saturation due to the low temperature of FTU walls makes it difficult to obtain reproducible plasmas. Another consequence of boronization is the large dilution of the plasma with the hydrogen particles released from the B film. All these effects decrease after about 60 discharges when boron is eroded by the limiter but it is still present on the chamber walls. During this phase which lasts for more than 500 discharges, oxygen concentration does not increase at all and metal influx is lower than before boronization because the physical sputtering by oxygen ions and atoms is strongly reduced.

Apicella, M. L.; Mazzitelli, G.; Apruzzese, G.; Bracco, G.; Esposito, B.; Gabellieri, L.; Kroegler, H.; Leigheb, M.; Maddaluno, G.; Marinucci, M.; Mattioli, M.; Pericoli Ridolfini, V.; Pieroni, L.; Romanelli, M.; FTU Team

2003-03-01

194

Number concentration and size distribution of aerosol particles in the middle troposphere over the Western Pacific Ocean  

NASA Astrophysics Data System (ADS)

Number concentration and size distribution of aerosol particles were measured on board aircraft during the PACE (Pacific Atmospheric Chemistry Experiment) campaign from Australia to Japan in January 1994. The spatial distribution of condensation nuclei (CN) ( r ? 4 nm) at 5-6 km altitude showed large variabilities in concentrations from 10 2 to 10 3 mg -1 that is, the concentrations were low (70-500 mg -1) in the intertropical convergence zone, high (400-1500 mg -1) in the subtropical highpressure area, and low again in the higher latitudes. An apparent opposite tendency was present between CN and large particle ( r ? 0.15 ?m) concentrations. The size distributions in the subtropical region exhibited high number concentrations of very fine particles ( r < 0.02 ?m). Together with the horizontal observation, vertical observations of aerosols were carried out over some areas. In the subtropical area (Saipan), CN concentration increased with altitude in contrast to the large particle concentration. Also most of the particles collected at 6 km altitude over Saipan contained sulfuric acid. These results are consistent with the results of Clarke (1993, J. geophys. Res.98, 20,633-20,647) that new particle formation is favored in the upper troposphere.

Zaizen, Yuji; Ikegami, Miwako; Tsutsumi, Yukitomo; Makino, Yukio; Okada, Kikuo; Jensen, Jørgen; Gras, John L.

195

BORON TRANSPORT WITHIN AN AGRICULTURAL FIELD: UNIFORM FLOW VERSUS MOBILE-IMMOBILE MODEL SIMULATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The transport of boron in soil is important to agriculture because boron concentrations in soil water are beneficial to plants only over a limited range (0.37 to 1.39 mmol L-1 for tolerant crops). Irrigation water in the San Joaquin Valley, California commonly has elevated B concentrations and soil ...

196

Atomic diffusion across Ni50Ti50—Cu explosive welding interface: Diffusion layer thickness and atomic concentration distribution  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are carried out to study atomic diffusion in the explosive welding process of Ni50Ti50—Cu (at.%). By using a hybrid method which combines molecular dynamics simulation and classical diffusion theory, the thickness of the diffusion layer and the atomic concentration distribution across the welding interface are obtained. The results indicate that the concentration distribution curves at different times have a geometric similarity. According to the geometric similarity, the atomic concentration distribution at any time in explosive welding can be calculated. Ni50Ti50—Cu explosive welding and scanning electron microscope experiments are done to verify the results. The simulation results and the experimental results are in good agreement.

Chen, Shi-Yang; Wu, Zhen-Wei; Liu, Kai-Xin

2014-06-01

197

Boron nitride housing cools transistors  

NASA Technical Reports Server (NTRS)

Boron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted.

1965-01-01

198

Spatial and temporal distribution characteristics of near-surface CO2 concentration over China based on GOSAT data  

NASA Astrophysics Data System (ADS)

To study the spatial and temporal distribution characteristics of near-surface CO2 concentration over China, the data of GOSAT L4B and auxiliary data of Mt Waliguan background observations, population density, total energy consumption (coal) and GDP in 2009 were applied to this study. The ArcGIS Geostatistical Analytical Method was used. The ground-based validation was processed by comparing GOSAT data with Mt Waliguan background observations. The variation characteristics of the near-surface CO2 concentration over China was analysed spatially and temporally. The results show that: GOSAT retrieved near-surface products are consistent with Mt Waliguan ground-based measurement; Near-surface CO2 concentration over China is relatively concentrated, and has significant differences between the East and the West, with a overall characteristic that CO2 concentration in the east of China is high and in the west is low; Near-surface CO2 concentration over China has a significant seasonal variation characteristic, and the monthly average concentration rise to the highest value of 396.512 ppmv in April (spring), which is significantly higher than other seasons, decline to the lowest value of 382.781 ppmv in July (summer); All relationships illustrate a big uncertainty, resulting a conclusion that the reasons causing the spatial distribution of near-surface CO2 concentration may be varied, could not be easily determined as anthropogenic or natural ressons, which need further study.

Zhao, Jing; Cui, Weihong; Sun, Yunhua

2014-11-01

199

Characterization of Concentration, Particle Size Distribution, and Contributing Factors to Ambient Hexavalent Chromium in an Area with Multiple Emission Sources  

Microsoft Academic Search

Airborne hexavalent chromium (Cr(VI)) is a known pulmonary carcinogen and can be emitted from both natural and anthropogenic sources, including diesel emissions. However, there is limited knowledge about ambient Cr(VI) concentration levels and its particle size distribution. This pilot study characterized ambient Cr(VI) concentrations in the New Jersey Meadowlands (NJ ML) district, which is close to the heavily trafficked New

Chang Ho Yu; Lihui Huang; Jin Young Shin; Francisco Artigas; Zhi-hua Tina Fan

2014-01-01

200

Primary Accretion and Turbulent Cascades: Scale-Dependence of Particle Concentration Multiplier Probability Distribution Functions  

NASA Astrophysics Data System (ADS)

Primitive bodies with 10s-100s of km diameter (or even larger) may form directly from small nebula constituents, bypassing the step-by-step “incremental growth” that faces a variety of barriers at cm, m, and even 1-10km sizes. In the scenario of Cuzzi et al (Icarus 2010 and LPSC 2012; see also Chambers Icarus 2010) the immediate precursors of 10-100km diameter asteroid formation are dense clumps of chondrule-(mm-) size objects. These predictions utilize a so-called cascade model, which is popular in turbulence studies. One of its usual assumptions is that certain statistical properties of the process (the so-called multiplier pdfs p(m)) are scale-independent within a cascade of energy from large eddy scales to smaller scales. In similar analyses, Pan et al (2011 ApJ) found discrepancies with results of Cuzzi and coworkers; one possibility was that p(m) for particle concentration is not scale-independent. To assess the situation we have analyzed recent 3D direct numerical simulations of particles in turbulence covering a much wider range of scales than analyzed by either Cuzzi and coworkers or by Pan and coworkers (see Bec et al 2010, J. Flu. Mech 646, 527). We calculated p(m) at scales ranging from 45-1024? where ? is the Kolmogorov scale, for both particles with a range of stopping times spanning the optimum value, and for energy dissipation in the fluid. For comparison, the p(m) for dissipation have been observed to be scale-independent in atmospheric flows (at much larger Reynolds number) for scales of at least 30-3000?. We found that, in the numerical simulations, the multiplier distributions for both particle concentration and fluid dissipation are as expected at scales of tens of ?, but both become narrower and less intermittent at larger scales. This is consistent with observations of atmospheric flows showing scale independence to >3000? if scale-free behavior is established only after some number 10 of large-scale bifurcations (at scales perhaps 10x smaller than the largest scales in the flow), but become scale-free at smaller scales. Predictions of primitive body initial mass functions can now be redone using a slightly modified cascade.

Cuzzi, Jeffrey N.; Weston, B.; Shariff, K.

2013-10-01

201

Co-solvent exfoliation and suspension of hexagonal boron nitride.  

PubMed

A simple method is presented for exfoliating and suspending hexagonal boron nitride using a co-solvent approach. A 60 w/w% concentration of tert-butanol in water is very effective at exfoliating boron nitride especially when compared to the individual components alone as indicated by UV-vis and transmission electron microscopy. Molecular weight and surface tension are found to play inverse roles in the exfoliation. PMID:25388621

Marsh, K L; Souliman, M; Kaner, R B

2015-01-01

202

Boron recovery from clay waste using Diaion CRB-02 resin.  

PubMed

A two-step process for boron recovery from clay waste is proposed in the present work. The leachate obtained after the clay waste was leached with sulphuric acid solution was treated with Diaion CRB-02 - a boron-specific resin for the separation of boron from the alkaline species in the leachate. The batch studies showed that a maximum boron recovery of about 95% was obtained at a pH value of 8.0, an initial boron concentration of 50 mg L(-1), a contact time of 24 h and a temperature of 25 degrees C. Equilibrium sorption data fitted the Langmuir isotherm. Column studies were carried out using different inlet boron concentrations and flow rates at a pH value of 8.0 and a temperature of 25 degrees C. The Yoon-Nelson and Thomas models were used to describe the dynamic behaviour of the column and to determine the column kinetic parameters. By these models and graphical integration, the column capacity values were found to be 7.3-8.5 mg g(-1) and 7.1-8.5 mg g(-1), respectively, and the 50% breakthrough time values were found to be 21-155 min and 19-149 min, respectively, depending on the inlet concentration and flow rate. It was observed that about 76% of the boron in the leachate solution could be recovered at an inlet boron concentration of 250 mg L(-1), a flow rate of 2.5 mL min(-1), a pH value of 8.0 and a temperature of 25 degrees C. PMID:20426274

Kipçak, I; Ozdemir, M

2010-03-01

203

Toxic elements at a disused mine district: Particle size distribution and total concentration in stream sediments and mine tailings.  

PubMed

Heavy metal and metalloid pollution at a disused pyrite mine was investigated. Five solid samples collected in the area (three stream sediments with different soil texture, a background soil sample and a mine tailing) were characterised by mineral and element composition, particle size distribution (by wet and dry sieving and laser diffraction) and total concentration by acid digestion (Mn, Zn, Cu, Pb, Hg, Cd, Sb and As). X-ray and element analyses denoted a common mineralogical and chemical composition of mainly quartz, clinochlore, muscovite, anorthite, and hematite. Particle size distributions of the five samples showed that stream sediments were characterised by larger percentage of sand range classes (2000-60 microm) while background sample and tailing are mainly characterised by gravel particles (>2000 microm). Wet and dry sieving procedures gave different particle size distributions, which can be interpreted by laser diffraction analysis and represented by Rosin-Rammler model. Concentrations of Zn, Cu and Cd were higher in the stream sediments than the tailing and background soil, while Mn, As, Sb and Hg are mainly concentrated in the tailing sample. Metal concentrations in the three stream sediment samples are correlated with both particle size dimensions (D(63.2)) and concentration of geochemical normalizers (iron and aluminium). These correlations are observed also for the pollutants that are mainly concentrated in tailing sample (Mn and As), denoting the importance of surface interactions also for the binding of these elements onto stream sediments. PMID:17400373

Giuliano, V; Pagnanelli, F; Bornoroni, L; Toro, L; Abbruzzese, C

2007-09-01

204

Boron Ion Implantation into Silicon by Use of the Boron Vacuum-Arc Plasma Generator  

SciTech Connect

This paper continues with presentation of experimental work pertaining to use of the boron vacuum arc (a.k.a. cathodic arc) plasma generator for boron doping in semiconductor silicon, particularly with a view to the problems associated with shallow junction doping. Progress includes development of an excellent and novel macroparticle filter and subsequent ion implantations. An important perceived issue for vacuum arc generators is the production of copious macroparticles from cathode material. This issue is more important for cathodes of materials such as carbon or boron, for which the particles are not molten or plastic, but instead are elastic, and tend to recoil from baffles used in particle filters. The present design starts with two vanes of special orientation, so as to back reflect the particles, while steering the plasma between the vanes by use of high countercurrents in the vanes. Secondly, behind and surrounding the vanes is a complex system of baffles that has been designed by a computer-based strategy to ultimately trap the particles for multiple bounces. The statistical transmittance of particles is less than 5 per coulomb of boron ions transmitted at a position just a few centimeters outside the filter. This value appears adequate for the silicon wafer application, but improvement is easily visualized as wafers will be situated much further away when they are treated in systems. A total of 11 silicon samples, comprising an area of 250 cm2, have been implanted. Particles were not detected. Sample biases ranged from 60 to 500 V. Boron doses ranged from 5 x 1014 to 5 x 1015/cm2. Exposure times ranged from 20 to 200 ms for average transmitted boron current values of about 125 mA. SIMS concentration profiles from crystalline material are presented. The results appear broadly favorable in relation to competitive techniques and will be discussed. It is concluded that doubly charged boron ions are not present in the plume.

Williams, J. M. [Brontek Delta Corporation, 6580 Valley Center Drive, Radford, VA 24141 (United States); Klepper, C. C. [Brontek Delta Corporation, 6580 Valley Center Drive, Radford, VA 24141 (United States); HY-Tech Research Corporation, 105 Centre Court, Radford, VA 24141 (United States); Chivers, D. J. [Ion Links Int. Ltd., 32 St. Mary's Place, Bathgate, Scotland (United Kingdom); Hazelton, R. C.; Moschella, J. J.; Keitz, M. D. [HY-Tech Research Corporation, 105 Centre Court, Radford, VA 24141 (United States)

2006-11-13

205

Mineral of the month: boron  

USGS Publications Warehouse

What does boron have to do with baseball, apple pie, motherhood and Chevrolet? Boron minerals and chemicals are used in the tanning of leather baseballs and gloves; in micro-fertilizer to grow apples and in the glass and enamels of bakewares to cook apple pie; in boron detergents for soaking baby clothes and diapers; and in fiberglass parts for the Chevrolet Corvette.

Lyday, Phyllis A.

2005-01-01

206

Roadside particle number distributions and relationships between number concentrations, meteorology, and traffic along a northern California freeway.  

PubMed

Particle number distributions were measured simultaneously upwind and downwind of a suburban-agricultural freeway to determine relationships with traffic and meteorological parameters. Average traffic volumes were 6330 vehicles/hr with 10% heavy-duty vehicles, and volumes were higher in July than November. Most downwind particle number distributions were bimodal, with a primary mode at approximately 10-25 nm, indicating that newly formed particles were sampled. Total downwind 6-237 nm particle number concentrations (Ntot) ranged from 9.3 x 10(3) to 2.5 x 10(5) cm(-3), with higher daily average concentrations in November compared with July. Ntot correlated with wind speed, temperature, and relative humidity. Upwind photochemically initiated nucleation likely led to elevated background nanoparticle concentrations in July, as evidenced by increasing upwind distribution modal diameter with increasing temperature and a strong correlation between upwind Ntot and solar radiation. Also in summer, Ntot showed stronger correlation with heavy-duty vehicle volumes than wind speed, temperature, and relative humidity. These results indicate the importance of measuring background particle size distributions simultaneously with roadside distributions. There may be a minimum vehicle volume from which useful real-world vehicle particle number distributions can be measured at roadside, even when collecting samples within 10 m of the traveled lanes. PMID:15149042

Nanzetta, M Katherine; Holmén, Britt A

2004-05-01

207

Impact of urbanization on the concentrations and distribution of organic contaminants in boreal lake sediments.  

PubMed

The main goal of this study was to evaluate the impacts of a middle-sized Finnish urban area on the quality of sediments in an adjacent boreal lake. We investigated the sources and distribution of organic pollutants (polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs)) in the sediments from urban stormwater traps and from Lake Vesijärvi. Grab surface sediment samples were taken from Lake Vesijärvi at various distances (25-2,000 m) from four major stormwater drainage outlets and at 15 urban stormwater traps in areas with different degrees of urbanization. These samples were analysed for 16 PAHs and 28 PCBs with gas chromatography-mass spectrometry. The concentrations of pollutants in the lake sediments were elevated in the vicinity of the urban shore (?PAH 3-16, ?PCB up to 0.02-0.3 mg/kg dw) and decreased as a function of distance (?PAH 0.1-2.5, ?PCB 0.01-0.3 mg/kg dw at a distance of more than 500 m from the shore), whereas contamination levels in suburban areas were notably lower (?PAH 0.1-3, ?PCB < LOQ-0.03 mg/kg dw; did not decline with distance). Possible sources and pathways of contamination were also investigated. The majority of stormwater trap sediments contained predominantly asphalt-derived PAHs due to pulverized pavement. PAHs in lake sediments were of pyrogenic origin, including the combustion of gasoline, diesel and coal. Suggested pathways of lake contamination are urban runoff discharge, boat traffic and atmospheric deposition. PMID:22527470

Honkonen, Olga; Rantalainen, Anna-Lea

2013-02-01

208

Biodistribution of the boron carriers boronophenylalanine (BPA) and/or decahydrodecaborate (GB-10) for Boron Neutron Capture Therapy (BNCT) in an experimental model of lung metastases  

SciTech Connect

BNCT was proposed for the treatment of diffuse, non-resectable tumors in the lung. We performed boron biodistribution studies with 5 administration protocols employing the boron carriers BPA and/or GB-10 in an experimental model of disseminated lung metastases in rats. All 5 protocols were non-toxic and showed preferential tumor boron uptake versus lung. Absolute tumor boron concentration values were therapeutically useful (25–76 ppm) for 3 protocols. Dosimetric calculations indicate that BNCT at RA-3 would be potentially therapeutic without exceeding radiotolerance in the lung.

D.W. Nigg; Various Others

2014-06-01

209

In situ deposition of boron layer by electron cyclotron resonance discharges for wall conditioning  

SciTech Connect

Plasma-assisted coating of boron thin films on inner surfaces of nuclear fusion devices, referred to as boronization, has been applied to many machines since its development in a laboratory device and the first performance in TEXTOR. Tile boronization is the most promising method of wall conditioning for particle controls in fusion experiments, in view of strong oxygen gettering (impurity control) and low hydrogen recycling (fuel control). To date, decomposition of boron hydride such as diborane (B{sub 2}H{sub 6}) and decaborane (B{sub 10}H{sub 14}) has been accomplished by dc glow discharges without magnetic fields which can boronize a large vessel as uniformly as possible. In a next generation fusion device such as ITER, however, a hot core plasma should be sustained quasi-steadily in a strong magnetic field provided by super-conducting magnets. Thus, a new boronization technique will be needed which enables in situ boron deposition using a fusion plasma itself without interrupting magnetic fields. In this paper, we report a fundamental experiment on boronization using a magnetized plasma, i.e., an electron-cyclotron-resonance (ECR) microwave discharge. The spatial distributions of boron films suggest that boron containing ions (B{sub m}H{sub n}{sup +}) are easily transported far away along the magnetic field lines, thus making boron deposition in a wide area of fusion machine.

Sugai, H.; Kokura, T.; Sasaki, K. [Nagoya Univ. (Japan)] [and others

1995-12-31

210

Proposed physiologic functions of boron in plants pertinent to animal and human metabolism.  

PubMed Central

Boron has been recognized since 1923 as an essential micronutrient element for higher plants. Over the years, many roles for boron in plants have been proposed, including functions in sugar transport, cell wall synthesis and lignification, cell wall structure, carbohydrate metabolism, RNA metabolism, respiration, indole acetic acid metabolism, phenol metabolism and membrane transport. However, the mechanism of boron involvement in each case remains unclear. Recent work has focused on two major plant-cell components: cell walls and membranes. In both, boron could play a structural role by bridging hydroxyl groups. In membranes, it could also be involved in ion transport and redox reactions by stimulating enzymes like nicotinamide adenine dinucleotide and reduced (NADH) oxidase. There is a very narrow window between the levels of boron required by and toxic to plants. The mechanisms of boron toxicity are also unknown. In nitrogen-fixing leguminous plants, foliarly applied boron causes up to a 1000% increase in the concentration of allantoic acid in leaves. In vitro studies show that boron inhibits the manganese-dependent allantoate amidohydrolase, and foliar application of manganese prior to application of boron eliminates allantoic acid accumulation in leaves. Interaction between borate and divalent cations like manganese may alter metabolic pathways, which could explain why higher concentrations of boron can be toxic to plants. PMID:7889877

Blevins, D G; Lukaszewski, K M

1994-01-01

211

In Vivo Boron Uptake Determination for Boron Neutron Capture Synovectomy  

SciTech Connect

Boron neutron capture synovectomy (BNCS) has been proposed as a new application of the boron neutron capture reaction for the treatment of rheumatoid arthritis. In BNCS, a boron compound is injected into the joint space, where it is taken up by the synovium. The joint is then irradiated with neutrons of a desired energy range, inducing the boron neutron capture reaction in boron-loaded cells. Boron uptake by the synovium is an important parameter in the assessment of the potential of BNCS and in the determination of whether to proceed to animal irradiations for the testing of therapeutic efficacy. We present results from an investigation of boron uptake in vivo by the synovium.

Binello, Emanuela; Shortkroff, Sonya; Yanch, Jacquelyn C.

1999-06-06

212

HEALTH EFFECTS OF CHRONIC EXPOSURE TO ARSENIC VIA DRINKING WATER IN INNER MONGOLIA: IV. DISTRIBUTION OF ARSENIC CONCENTRATIONS IN WELLS  

EPA Science Inventory

HEALTH EFFECTS OF CHRONIC EXPOSURE TO ARSENIC VIA DRINKING WATER IN INNER MONGOLIA: IV. DISTRIBUTION OF ARSENIC CONCENTRATIONS IN WELLS Zhixiong Ning, B.S., Zhiyi Liu,B.S., Shiying Zhang, B.S., Chenglong Ma, B.S., Inner Mongolia Ba Men Anti-epidemic Station, Michael Ri...

213

Frequency distributions and spatially dependent variability of ammonium and nitrate concentrations in soil under grazed and ungrazed grassland  

Microsoft Academic Search

The frequency distributions of soil NO3- and NH4+ concentrations under grazed and ungrazed grassland were found to be lognormal, irrespective of time of year or soil depth. The variance and skewness of the sample values increased with stocking density and use of N fertilizer. An analysis of the spatial dependence of the variability using the semivariogram showed a high ‘nugget’

RE White; Rosalyn A Haigh; Jh Macduff

1987-01-01

214

Boron hydride polymer coated substrates  

DOEpatents

A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

1986-08-27

215

Metronidazole and Hydroxymetronidazole Central Nervous System Distribution: 2. Cerebrospinal Fluid Concentration Measurements in Patients with External Ventricular Drain  

PubMed Central

This study explored metronidazole and hydroxymetronidazole distribution in the cerebrospinal fluid (CSF) of brain-injured patients. Four brain-injured patients with external ventricular drain received 500 mg of metronidazole over 0.5 h every 8 h. CSF and blood samples were collected at steady state over 8 h, and the metronidazole and hydroxymetronidazole concentrations were assayed by high-pressure liquid chromatograph. A noncompartmental analysis was performed. Metronidazole is distributed extensively within CSF, with a mean CSF to unbound plasma AUC0–? ratio of 86% ± 16%. However, the concentration profiles in CSF were mostly flat compared to the plasma profiles. Hydroxymetronidazole concentrations were much lower than those of metronidazole both in plasma and in CSF, with a corresponding CSF/unbound plasma AUC0–? ratio of 79% ± 16%. We describe here for the first time in detail the pharmacokinetics of metronidazole and hydroxymetronidazole in CSF. PMID:24277050

Frasca, Denis; Dahyot-Fizelier, Claire; Adier, Christophe; Mimoz, Olivier; Debaene, Bertrand; Couet, William

2014-01-01

216

Pore-size distributions of cationic polyacrylamide hydrogels varying in initial monomer concentration and cross-linker/monomer ratio  

SciTech Connect

Pore-size distributions have been measured for cationic acrylamide-based hydrogels. The authors use the experimental mixed-solute-exclusion method, MSE (introduced by Kuga), to obtain the solute-exclusion curve representing the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The authors use the Brownian motion model (developed by Cassasa) to convert the size-exclusion curve into the pore-size distribution, which gives the frequency of pore radius R as a function of R. This theoretically-based interpretation of MSE data leads to the Fredholm integral equation that they solve numerically. Results are reported for a series of hydrogels containing acrylamide and 3% MAPTAC; the hydrogels differed in extent of cross-linking and/or initial concentration of monomer. Pore-size distributions shift to lower pore sizes with rising initial monomer concentration and with rising cross-linker-to-monomer ratio.

Kremer, M.; Pothmann, E.; Roessler, T.; Baker, J.; Yee, A.; Blanch, H.; Prausnitz, J.M. (Lawrence Berkeley Lab., CA (United States))

1994-05-23

217

Axial residual stresses in boron fibers  

NASA Technical Reports Server (NTRS)

The axial residual stress distribution as a function of radius was determined from the fiber surface to the core including the average residual stress in the core. Such measurements on boron on tungsten (B/W) fibers show that the residual stresses for 102, 142, 203, and 366 micron diameter fibers were similar, being compressive at the surface and changing monotonically to a region of tensile within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile stress of about 860 mn/sq.m and then decreases to a compressive stress near the tungsten boride core. Data were presented for 203 micron diameter B/W fibers that show annealing above 900 C reduces the residual stresses. A comparison between 102 micron diameter B/W and boron on carbon (b/C) shows that the residual stresses were similar in the outer regions of the fibers, but that large differences near and in the core were observed. The effects of these residual stresses on the fracture of boron fibers were discussed.

Behrendt, D. R.

1978-01-01

218

Geographical distribution of the annual mean radon concentrations in primary schools of Southern Serbia - application of geostatistical methods.  

PubMed

Between 2008 and 2011 a survey of radon ((222)Rn) was performed in schools of several districts of Southern Serbia. Some results have been published previously (Žuni? et al., 2010; Carpentieri et al., 2011; Žuni? et al., 2013). This article concentrates on the geographical distribution of the measured Rn concentrations. Applying geostatistical methods we generate "school radon maps" of expected concentrations and of estimated probabilities that a concentration threshold is exceeded. The resulting maps show a clearly structured spatial pattern which appears related to the geological background. In particular in areas with vulcanite and granitoid rocks, elevated radon (Rn) concentrations can be expected. The "school radon map" can therefore be considered as proxy to a map of the geogenic radon potential, and allows identification of radon-prone areas, i.e. areas in which higher Rn radon concentrations can be expected for natural reasons. It must be stressed that the "radon hazard", or potential risk, estimated this way, has to be distinguished from the actual radon risk, which is a function of exposure. This in turn may require (depending on the target variable which is supposed to measure risk) considering demographic and sociological reality, i.e. population density, distribution of building styles and living habits. PMID:24231373

Bossew, P; Žuni?, Z S; Stojanovska, Z; Tollefsen, T; Carpentieri, C; Veselinovi?, N; Komatina, S; Vaupoti?, J; Simovi?, R D; Antignani, S; Bochicchio, F

2014-01-01

219

Numerical simulation on the effects of drug eluting stents at different Reynolds numbers on hemodynamic and drug concentration distribution  

PubMed Central

Background The changes of hemodynamics and drug concentration distribution caused by the implantation of drug eluting stents (DESs) in curved vessels have significant effects on In-Stent Restenosis. Methods A 3D virtual stent with 90°curvature was modelled and the distribution of wall shear stress (WSS) and drug concentration in this model were numerically studied at Reynolds numbers of 200, 400, 600, 800. Results The results showed that (1) the intensity of secondary flow at the 45° cross-section was stronger than that at the 90° cross-section; (2) As the Reynolds number increases, the WSS decreases. When the Reynolds number reaches 600, the low-WSS region only accounts for 3% of the total area. (3) The effects of Reynolds number on drug concentration in the vascular wall decreases in proportionally and then the blood velocity increased 4 times, the drug concentration in the vascular wall decreased by about 30%. (4) The size of the high drug concentration region is inversely proportional to the Reynolds number. As the blood velocity increases, the drug concentration in the DES decreases, especially at the outer bend. Conclusions It is beneficial for the patient to decrease vigorous activities and keep calm at the beginning of the stent implantation, because a substantial amount of the drug is released in the first two months of stent implantation, thus a calm status is conducive to drug release and absorption; Subsequently, appropriate exercise which increases the blood velocity is helpful in decreasing regions of low-WSS. PMID:25602685

2015-01-01

220

Concentration regimes of biopolymers xanthan, tara, and clairana, comparing dynamic light scattering and distribution of relaxation time.  

PubMed

The aim of this work was to evaluate the utilization of analysis of the distribution of relaxation time (DRT) using a dynamic light back-scattering technique as alternative method for the determination of the concentration regimes in aqueous solutions of biopolymers (xanthan, clairana and tara gums) by an analysis of the overlap (c*) and aggregation (c**) concentrations. The diffusion coefficients were obtained over a range of concentrations for each biopolymer using two methods. The first method analysed the behaviour of the diffusion coefficient as a function of the concentration of the gum solution. This method is based on the analysis of the diffusion coefficient versus the concentration curve. Using the slope of the curves, it was possible to determine the c* and c** for xanthan and tara gum. However, it was not possible to determine the concentration regimes for clairana using this method. The second method was based on an analysis of the DRTs, which showed different numbers of relaxation modes. It was observed that the concentrations at which the number of modes changed corresponded to the c* and c**. Thus, the DRT technique provided an alternative method for the determination of the critical concentrations of biopolymers. PMID:23671627

Oliveira, Patrícia D; Michel, Ricardo C; McBride, Alan J A; Moreira, Angelita S; Lomba, Rosana F T; Vendruscolo, Claire T

2013-01-01

221

Concentration Regimes of Biopolymers Xanthan, Tara, and Clairana, Comparing Dynamic Light Scattering and Distribution of Relaxation Time  

PubMed Central

The aim of this work was to evaluate the utilization of analysis of the distribution of relaxation time (DRT) using a dynamic light back-scattering technique as alternative method for the determination of the concentration regimes in aqueous solutions of biopolymers (xanthan, clairana and tara gums) by an analysis of the overlap (c*) and aggregation (c**) concentrations. The diffusion coefficients were obtained over a range of concentrations for each biopolymer using two methods. The first method analysed the behaviour of the diffusion coefficient as a function of the concentration of the gum solution. This method is based on the analysis of the diffusion coefficient versus the concentration curve. Using the slope of the curves, it was possible to determine the c* and c** for xanthan and tara gum. However, it was not possible to determine the concentration regimes for clairana using this method. The second method was based on an analysis of the DRTs, which showed different numbers of relaxation modes. It was observed that the concentrations at which the number of modes changed corresponded to the c* and c**. Thus, the DRT technique provided an alternative method for the determination of the critical concentrations of biopolymers. PMID:23671627

Oliveira, Patrícia D.; Michel, Ricardo C.; McBride, Alan J. A.; Moreira, Angelita S.; Lomba, Rosana F. T.; Vendruscolo, Claire T.

2013-01-01

222

Boron and Marine Life: A New Look at an Enigmatic Bioelement  

Microsoft Academic Search

On the occasion of the 200th anniversary of the discovery of boron, we review the oceanic biogeochemistry of boron as well\\u000a as suitable analytical techniques for its determination. This overview includes aspects of biogeochemistry including geochemical\\u000a stable isotope variations, uptake, transport, storage, nutritional value, toxicity, and distribution within biological materials,\\u000a providing a framework for discussion of the role of boron

Carl J. Carrano; Stephen Schellenberg; Shady A. Amin; David H. Green; Frithjof C. Küpper

2009-01-01

223

Calculation of dose distribution near an innovative concentric balloon catheter for endovascular brachytherapy  

Microsoft Academic Search

Purpose: Using a radioactive solution-filled catheter for intravascular irradiation has the potential problem of chemical and radiological toxicity in the case of a balloon rupture. In order to reduce this risk, an innovative concentric balloon catheter was developed.Methods and Materials: The concentric balloon was made by inner and outer balloons filled with saline and radioactive solution, respectively. The optimal inner

Zhigang Xu; Guozhen Yang; L. E Reinstein; Patricia E Cole

2001-01-01

224

Extended distributed model for analysis of non-ideal concentration operation  

Microsoft Academic Search

Non-ideal illumination is often observed in practical concentrator systems. The simulation to that problem was usually done by a time-consuming 2D numerical calculation or a linear approximation of algebraic calculation. This paper proposes a simple method to anticipate non-linear response to non-ideal illumination operation for concentrator cells.

Kenji Araki; Masafumi Yamaguchi

2003-01-01

225

Process for microwave sintering boron carbide  

DOEpatents

A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

Holcombe, Cressie E. (440 Sugarwood Dr., Knoxville, TN 37922); Morrow, Marvin S. (Rte. #3, Box 113, Kingston, TN 37763)

1993-01-01

226

Superconductivity in Boron-doped SiC  

NASA Astrophysics Data System (ADS)

We report superconductivity in heavily boron-doped bulk silicon carbide related to the diamond structure. The compound exhibits zero resistivity and diamagnetic susceptibility below a critical temperature Tc of ˜1.4 K, and an effective boron doping concentration higher than 1021 cm-3. We present the H-T phase diagram of this new superconducting compound determined from AC susceptibility. In finite DC magnetic fields a clear hysteresis was observed between cooling and subsequent warming runs. This indicates, in contrast with the type-II superconductivity in boron-doped diamond and silicon, that a type-I superconductivity with a critical field Hc(0) of about 100 Oe is realized in boron-doped SiC. Moreover, the specific-heat shows a clear jump at Tc, demonstrating bulk nature of the superconductivity.

Ren, Zhi-An; Kato, Junya; Muranaka, Takahiro; Akimitsu, Jun; Kriener, Markus; Maeno, Yoshiteru

2007-10-01

227

Use of dissolved H2 concentrations to determine distribution of microbially catalyzed redox reactions in anoxic groundwater  

USGS Publications Warehouse

The potential for using concentrations of dissolved H2 to determine the distribution of redox processes in anoxic groundwaters was evaluated. In pristine aquifers in which standard geochemical measurements indicated that Fe-(III) reduction, sulfate reduction, or methanogenesis was the terminal electron accepting process (TEAP), the H2 concentrations were similar to the H2 concentrations that have previously been reported for aquatic sediments with the same TEAPs. In two aquifers contaminated with petroleum products, it was impossible with standard geochemical analyses to determine which TEAPs predominated in specific locations. However, the TEAPs predicted from measurements of dissolved H2 were the same as those determined directly through measurements of microbial processes in incubated aquifer material. These results suggest that H2 concentrations may be a useful tool for analyzing the redox chemistry of nonequilibrium groundwaters.

Lovley, D.R.; Chapelle, F.H.; Woodward, J.C.

1994-01-01

228

Electron Cyclotron Resonance Discharge of Sublimation Gas of Decaborane and Its Application to Preparation of Boron Thin Films  

NASA Astrophysics Data System (ADS)

Plasmas are produced by electron cyclotron resonance (ECR) discharge of a mixture of hydrogen and sublimation gas of decaborane B10H14 in its solid state. Emissions from boron atoms B and boron hydride BH in the plasmas are measured spectroscopically. Hydrogenated boron films are prepared using the ECR plasmas. The hydrogen concentration in the boron films is about 2% at the substrate temperature T s of 300°C. Apparent activation energy of the growth reactions of the boron films is estimated to be about -0.06 eV.

Ito, Yoshifumi; Kanazawa, Naoki; Arakawa, Takashi; Saidoh, Masahiro; Nishikawa, Masahiro

1994-07-01

229

Precise gamma ray measurement of the radial distribution of a cracking catalyst at diluted concentrations in a glass riser  

NASA Astrophysics Data System (ADS)

The radial concentration distribution of a cracking catalyst circulating in a glass riser of a cold model was precisely measured in diluted flow regime. Catalyst and compressed air were the components of the fluidized bed system. The gamma transmission measurements were carried out with a 241Am radioactive source and a scintillation NaI(Tl) detector. The gamma ray transmission profile of riser was evaluated and the main effects were identified. The standard uncertainty in the concentration values was evaluated as a function of the photopeak counts. A model was proposed to describe the profile curve of the empty riser as a function of the chordal length that fits experimental data adequately. A calibration of catalyst density carried out in static experiments and an integral evaluation of the radial scan were compared with punctual density. Under flow conditions the radial concentration distribution was measured at (2-16) kg/m 3 and at (10-60) kg/m 3 intervals. At two different airflow rates, concentration distribution tendency to move from the annular to the core region in the higher airflow, was observed.

Dantas, C. C.; Dos Santos, V. A.; Melo, A. C. B. A.; Van Grieken, R.

2006-09-01

230

Facile synthesis of concentrated gold nanoparticles with low size-distribution in water: temperature and pH controls  

PubMed Central

The citrate reduction method for the synthesis of gold nanoparticles (GNPs) has known advantages but usually provides the products with low nanoparticle concentration and limits its application. Herein, we report a facile method to synthesize GNPs from concentrated chloroauric acid (2.5 mM) via adding sodium hydroxide and controlling the temperature. It was found that adding a proper amount of sodium hydroxide can produce uniform concentrated GNPs with low size distribution; otherwise, the largely distributed nanoparticles or instable colloids were obtained. The low reaction temperature is helpful to control the nanoparticle formation rate, and uniform GNPs can be obtained in presence of optimized NaOH concentrations. The pH values of the obtained uniform GNPs were found to be very near to neutral, and the pH influence on the particle size distribution may reveal the different formation mechanism of GNPs at high or low pH condition. Moreover, this modified synthesis method can save more than 90% energy in the heating step. Such environmental-friendly synthesis method for gold nanoparticles may have a great potential in large-scale manufacturing for commercial and industrial demand. PMID:21733153

2011-01-01

231

Selective boron delivery to murine tumors by lipophilic species incorporated in the membranes of unilamellar liposomes.  

PubMed Central

The nido-carborane species K[nido-7-CH3(CH2)15-7,8-C2B9H11] has been synthesized for use as an addend for the bilayer membrane of liposomes. Small unilamellar vesicles, composed of distearoylphosphatidylcholine/cholesterol, 1:1, and incorporating K[nido-7-CH3(CH2)15-7,8-C2B9H11] in the bilayer, have been investigated in vivo. The time-course biodistribution of boron delivered by these liposomes was determined by inductively coupled plasma-atomic emission spectroscopy analyses after the injection of liposomal suspensions in BALB/c mice bearing EMT6 mammary adenocarcinomas. At the low injected doses normally used (approximately 5-10 mg of boron per kg of body weight), peak tumor boron concentrations of approximately 35 micrograms of boron per g of tissue and tumor/blood boron ratios of approximately 8 were achieved. These values are sufficiently high for the successful application of boron neutron capture therapy. The bilayer-embedded boron compound may provide the sole boron source or, alternatively, a concentrated aqueous solution of a hydrophilic boron compound may also be encapsulated within the liposomes to provide a dose enhancement. Thus, the incorporation of both K[nido-7-CH3(CH2)15-7,8-C2B9H11] and the hydrophilic species, Na3[1-(2'-B10H9)-2-NH3B10H8], within the same liposomes demonstrated significantly enhanced biodistribution characteristics, exemplified by maximum tumor boron concentrations of approximately 50 micrograms of boron per g of tissue and tumor/blood boron ratios of approximately 6. PMID:7877984

Feakes, D A; Shelly, K; Hawthorne, M F

1995-01-01

232

Tersoff Potential Parameters for Simulating Cubic Boron Carbonitrides  

NASA Astrophysics Data System (ADS)

We have developed Tersoff potential parameters for boron in order to simulate cubic boron carbonitride systems by molecular dynamics. Combined with parameters for C and N available from the literature, our parameters are shown to reproduce the lattice parameters and bulk moduli of boron nitride and boron carbonitride (C0.33(BN)0.67) with good accuracy. By simulating several systems of formula (Cx(BN)1-x) over a wide range of carbon contents (x=0 to 1), we observed the same trends in the deviation from ideal mixing as found experimentally. We attribute this deviation to the relatively longer C-N bonds distributed randomly throughout the intermediate C content systems.

Matsunaga, Katsuyuki; Fisher, Craig; Matsubara, Hideaki

2000-01-01

233

[Effect of the change in sulphate and dissolved oxygen mass concentration on metal release in old cast iron distribution pipes].  

PubMed

To understand the processes of corrosion by-product release and the consequent "red water" problems caused by the variation of water chemical composition in drinking water distribution system, the effect of sulphate and dissolved oxygen (DO) concentration on total iron release in corroded old iron pipe sections historically transporting groundwater was investigated in laboratory using small-scale pipe section reactors. The release behaviors of some low-level metals, such as Mn, As, Cr, Cu, Zn and Ni, in the process of iron release were also monitored. The results showed that the total iron and Mn release increased significantly with the increase of sulphate concentration, and apparent red water occurred when sulphate concentration was above 400 mg x L(-1). With the increase of sulfate concentration, the effluent concentrations of As, Cr, Cu, Zn and Ni also increased obviously, however, the effluent concentrations of these metals were lower than the influent concentrations under most circumstances, which indicated that adsorption of these metals by pipe corrosion scales occurred. Increasing DO within a certain range could significantly inhibit the iron release. PMID:24288993

Wu, Yong-li; Shi, Bao-you; Sun, Hui-fang; Zhang, Zhi-huan; Gu, Jun-nong; Wang, Dong-sheng

2013-09-01

234

Flux density distribution in the focal region of a solar concentrator system  

Microsoft Academic Search

In high temperature solar energy applications highly concentration optical systems, such as, e.g., parabolic dishes, achieve typical tradition flux densities <2 MW\\/M². In order to investigate thermo and photochemical reactions at temperatures <1500 K and radiation flux densities <2 MW\\/m² a solar furnace was built at Paul Scherrer Institute (PSI). This furnace is a two-stage concentrator. The first stage is

M. Schubnell; J. Keller; A. Imhof

1991-01-01

235

Aircraft measurements of vertical and spatial distribution of aerosol concentration and size over different environments in India  

NASA Astrophysics Data System (ADS)

It is well known that atmospheric aerosols play a major role in climate change by directly scattering and absorbing the incoming and outgoing radiation as well as through modifying cloud properties, such as droplet size distribution and cloud lifetime. However, aerosol measurements, particularly their vertical distribution, are less and unevenly distributed around the globe. Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) is an Indian National program conducted by the Indian Institute of Tropical Meteorology (IITM), Pune, India, during summer monsoon season May-September 2009. Under CAIPEEX program, an instrumented aircraft has been used to study background aerosol along with cloud microphysical properties and their interactions over different parts of India. This experiment has been carried out for the first time in India. During CAIPEEX, PCASP (Passive Cavity aerosol Spectro Photometer) which measures aerosol concentrations in the size range 0.1 to 3 microns is operated in the aircraft over different parts of India viz., Pathankot (May), Hyderabad (June), Bengaluru (June-July), Bareilly (July-August), Guwahati (August- September) and Pune (September). The preliminary results suggest that aerosol vertical distribution is observed up to a maximum of 7.0 - 7.5 km, with high surface concentrations and enhanced layers at higher altitudes. During monsoon period also high concentrations are observed. The spatial distribution of aerosols along the flight track shows aerosol gradient from one place to another place. Also thick haze is observed near Himalayas during the month of May. The results at all the locations showed high aerosol concentrations in the size range of 0.1 to 0.3 microns, steep decreasing trend from 0.3 - 0.6 microns and less concentration from 0.6 to 3 microns. In the size range of 0.1 to 0.3 microns the concentrations varied from 100-10000 particles/cc. In-depth analysis of CAIPEEX data gives a clear picture of aerosol distribution over different parts of India during monsoon season, which further helps to understand the cloud micro physics. This paper presents a glimpse of the CAIPEEX mission and the preliminary results of aerosol measurements over different environments in India.

Kumari B., Padma; S, Mahesh Kumar R.; R, Kulkarni J.; N, Goswami B.

2010-05-01

236

A study of Monitoring and Mapping for Radon-Concentration Distribution in Gyeongju - 12201  

SciTech Connect

Radon is one of the most important contributors to the radiation exposure in humans. This study measured the indoor radon concentrations at the 17 elementary school auditoriums that were sampled from those in the city of Gyeongju, Korea. The reason that an elementary school was selected as a measurement object is that many students and teachers stay for a long time in a day and it's easy to identify the characteristics of the auditorium building such as the essential building. The measurement shows that most of the indoor radon concentrations at the 17 elementary school auditoriums did not exceed 148 Bq/m{sup 3} that is the action level recommended by U.S. Environmental Protection Agency. This study measured the indoor radon concentrations at the elementary school auditoriums in Gyeongju. The measurements were analyzed according to the bedrock type and the time intervals per day. In this study, it was found that the indoor radon concentrations over off-duty hours were generally higher that those over on-duty hours, and the indoor radon concentration in the area whose bedrock is volcanic rock was higher than those in the area of the other types of bedrock. As mentioned above, attention has to be paid to an elementary school since many young students and teachers stay for more 6 hours a day at it. Hence, it is necessary to continuously monitor and properly manage the indoor radon concentrations in the elementary schools. (authors)

Park, Chan Hee; Lee, Jung Min; Jang, So Young; Kim, Shin Jae; Moon, Joo Hyun [Dongguk University, 707, Seokjang-Dong, Gyeongju, Gyeongbuk 780-714 (Korea, Republic of)

2012-07-01

237

Fracture Strength: Stress Concentration, Extreme Value Statistics, and the Fate of the Weibull Distribution  

NASA Astrophysics Data System (ADS)

The statistical properties of fracture strength of brittle and quasibrittle materials are often described in terms of the Weibull distribution. However, the weakest-link hypothesis, commonly used to justify it, is expected to fail when fracture occurs after significant damage accumulation. Here we show that this implies that the Weibull distribution is unstable in a renormalization-group sense for a large class of quasibrittle materials. Our theoretical arguments are supported by numerical simulations of disordered fuse networks. We also find that for brittle materials such as ceramics, the common assumption that the strength distribution can be derived from the distribution of preexisting microcracks by using Griffith's criteria is invalid. We attribute this discrepancy to crack bridging. Our findings raise questions about the applicability of Weibull statistics to most practical cases.

Bertalan, Zsolt; Shekhawat, Ashivni; Sethna, James P.; Zapperi, Stefano

2014-09-01

238

Concentration and Spatial Distribution of Selected Constituents in Detroit River Bed Sediment Adjacent to Grassy Island, Michigan, August 2006  

USGS Publications Warehouse

In August 2006, the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, collected sediment?core samples from the bed of the Detroit River adjacent to Grassy Island. The goal of the sampling was to assess the distribution and concentration of chemical constituents in sediment adjacent to Grassy Island, which was operated from 1960 to 1982 as a confined disposal facility to hold dredge spoils. On August 31, 2006, seven samples were collected at four locations in the Detroit River on the north, south, east, and west sides of the island. Metals concentrations in the riverbed sediment tended to be higher on the west side of the island, whereas organic?compound concentrations were generally higher on the east side. Comparison of results from this sampling to concentrations reported in previous studies indicates that the concentrations of inorganic constituents, mainly metals, in the riverbed sediment around Grassy Island fell within the range of concentrations found regionally throughout the Detroit River and in most cases have lower mean and median values than found elsewhere regionally in the Detroit River. Comparison of results from the August 31, 2006, sampling to U.S. Environmental Protection Agency risk?based sediment?quality guidelines indicates that 18 organic constituents for which an ecological screening level (ESL), and (or) a threshold effect concentration (TEC), and (or) a probable effect concentration (PEC) has been defined exceeded one or more of these guidelines at least once. Further work would be needed to determine whether constituent concentrations in the river sediment are related to constituent runoff from Grassy Island.

Hoard, C.J.

2008-01-01

239

Prevention of boron penetration from p+ poly gate by RTN produced thin gate oxide  

Microsoft Academic Search

The effect of a nitrided oxide gate film produced by RTN on the boron penetration from a p+ poly gate electrode was studied. It was found that the RTN oxide gate is very effective for the suppression of boron penetration, even when the nitrogen concentration is as low as a few percent.

T. Morimoto; H. S. Momose; K. Yamabe; H. Iwai

1990-01-01

240

Temporal distribution of heavy metal concentrations in oysters Crassostrea rhizophorae from the central Venezuelan coast.  

PubMed

The oyster Crassostrea rhizophorae is a bivalve abundant in Venezuelan estuaries and consumed by local populations. No known values have been reported on trace metals in oysters from the central Venezuelan coast. We report the concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn in the soft parts of C. rhizophorae, which were collected bimonthly between March 2008 and March 2009, at two sampling areas from the Central Venezuelan Coast: Buche estuary and Mochima estuary. Our results show that for each metal there is a similar temporal variation pattern. The concentrations of the heavy metals reported in this work are useful as reliable baselines and can be used for comparison in future environment studies. Concentrations in C. rhizophorae from the Buche estuary can be interpreted to be high on a global scale for Cd, Cu, Ni and Mn, indicating atypically raised bioavailabilities. PMID:23746942

Alfonso, Juan A; Handt, Helga; Mora, Abrahan; Vásquez, Yaneth; Azocar, José; Marcano, Eunice

2013-08-15

241

Beneficiation of borax by reverse flotation in boron saturated brine.  

PubMed

Flotation is one of the plausible methods for recovering borax fines discharged as fine waste to the tailings dam in the Kirka borax processing plant. A literature review dealing with the flotation behavior of boron minerals reveals that clay minerals in the boron ores coat boron minerals and thus deteriorate the quality of boron concentrates produced by direct flotation. The main objective of this study is therefore to recover borax fines from the tailings of the concentrator by reverse flotation. A three-level-factor experimental design was used to determine the main and interaction effects of variables selected on the metallurgical performance of reverse flotation. An analysis of variance for experimental results indicates that interaction effects of the variables for concentrate quality and recovery of B2O3 is nonsignificant and the most important variable for grade of concentrate and recovery is the collector dosage. It is shown that a concentrate assaying 11.25% B2O3 with 89.90% B2O3 recovery could be produced by means of single-stage (rougher) reverse flotation. Additionally, in order to produce a sufficient-quality concentrate, a multistage reverse flotation scheme involving rougher, scavenger, and two cleaners was devised. A final concentrate containing 23.47% B2O3 with 81.78% B2O3 recovery was obtained from these tests. The reverse flotation method can be thus considered as an important option for the beneficiation of borax fines. PMID:15939429

Cafer Cilek, Emin; Uresin, Hasan

2005-10-15

242

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study  

NASA Astrophysics Data System (ADS)

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt% H2O and 1.8 wt% B2O3. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 °C, 100 MPa, 20 wt% H2O and 4.1 wt% B2O3. Cooling and concomitant fractional crystallisation from 700 to 500 °C induced development of two conjugate melts, an H2O-poor (A-melt) and an H2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H2O-rich melt. Temperature-dependent distribution coefficients $ D{boron}{{B - melt/A - melt}} $ are 1.3 at 650 °C, 1.5 at 600 °C, and 1.8 at 500 °C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt% was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 °C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 °C, along with varying densities and highly variable B2O3 contents ranging from 0.20 to 2.94 wt%. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine- and tin-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.

Thomas, Rainer; Förster, Hans-Jürgen; Heinrich, Wilhelm

2002-09-01

243

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study  

NASA Astrophysics Data System (ADS)

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt% H2O and 1.8 wt% B2O3. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 °C, 100 MPa, 20 wt% H2O and 4.1 wt% B2O3. Cooling and concomitant fractional crystallisation from 700 to 500 °C induced development of two conjugate melts, an H2O-poor (A-melt) and an H2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H2O-rich melt. Temperature-dependent distribution coefficients $ D{boron}{{B - melt/A - melt}} $ are 1.3 at 650 °C, 1.5 at 600 °C, and 1.8 at 500 °C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt% was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 °C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 °C, along with varying densities and highly variable B2O3 contents ranging from 0.20 to 2.94 wt%. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine- and tin-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.

Thomas, Rainer; Förster, Hans-Jürgen; Heinrich, Wilhelm

244

Cyanide distribution in five fatal cyanide poisonings and the effect of storage conditions on cyanide concentration in tissue.  

PubMed

The cyanide distribution in five fatal cyanide poisonings was analyzed by the pyridine-pyrazolone method using a Conway diffusion cell. In order to study the effect of storage conditions on cyanide concentration in tissue samples, the cyanide concentrations were first measured immediately after collection of the samples at autopsy, then measured again after storage in a refrigerator (4 degrees C) or in a freezer (-20 degrees C) for periods ranging from 1 day to 3 weeks. Concentrations in all but three of the blood samples stored at 4 degrees C or -20 degrees C increased, with concentration ratios based on measurement made before and after storage ranging from 0.71 to 1.46. The concentrations in the liver, kidney, and brain samples either increased or decreased, with ratios of from 0.2 to 8.8. The concentrations in the stomach contents samples decreased rapidly at 4 degrees C, but hardly changed at all at -20 degrees C. PMID:3192140

Chikasue, F; Yashiki, M; Kojima, T; Miyazaki, T; Okamoto, I; Ohtani, M; Kodama, K

1988-09-01

245

Mathematical modeling and finite element simulation of slow release of drugs using hydrogels as carriers with various drug concentration distributions.  

PubMed

In drug release systems using hydrogels as carriers, the presence of the polymer network will reduce the drug release rate, which can extend the release period. For a controlled-release process of drug, usually the ideal situation is to get a zero-order drug release rate. In this paper, the mathematical model of hydrogel swelling processes is constructed on the basis of a biphasic theory, and then an integrated equation that considers both water convection and drug diffusion phenomena is used to describe the drug release process. The effects of the initial drug concentration with nonuniform distributions along the radial direction of hydrogel carriers on the release of drugs are studied through simulating two-dimensional hydrogel swelling processes by means of the COMSOL Multiphysics software. The simulation results show that along with the hydrogel swelling, the drug release rate is changing, and the major influencing factors of the drug release rate are water convection and drug diffusion coefficient, which are affected by water volume fraction, drug concentration distribution in matrix, and carrier radius. The results also indicate that the initial drug concentration distribution following a sine curve can result in an ideal zero-order release process. PMID:23526640

Xu, Yihan; Jia, Yuxi; Wang, Zhao; Wang, Zhaojing

2013-05-01

246

A simple model for predicting the flux distribution through the focal plane of a multifaceted concentrator solar furnace  

SciTech Connect

The authors describe a small doubly reflecting research furnace. Its optical components, a heliostat and a concentrating array of hexagonal-in-plan-form mirrors, focus sunlight at the aperture of a cavity receiver. A perfect paraboloid of revolution would have given higher concentration ratios. But large paraboloids are difficult to make and manipulate. Small hexagons are convenient and can be close packed. Spherical mirrors centered on a sphere simplified construction and were economical. In this note they use a simple model to describe the radial distribution of the normal flux at the focus of such an array. A schematic representation of a cross section of the concentrator mirror array in a plane which includes its axis is shown.

Carlson, D.E.E.; Diver, R.B.; Fletcher, E.A.

1984-02-01

247

Direct elicitation of template concentration from quantification cycle (Cq) distributions in digital PCR.  

PubMed

Digital PCR (dPCR) exploits limiting dilution of a template into an array of PCR reactions. From this array the number of reactions that contain at least one (as opposed to zero) initial template is determined, allowing inferring the original template concentration. Here we present a novel protocol to efficiently infer the concentration of a sample and its optimal dilution for dPCR from few targeted qPCR assays. By taking advantage of the real-time amplification feature of qPCR as opposed to relying on endpoint PCR assessment as in standard dPCR prior knowledge of template concentration is not necessary. This eliminates the need for serial dilutions in a separate titration and reduces the number of necessary reactions. We describe the theory underlying our approach and discuss experimental moments that contribute to uncertainty. We present data from a controlled experiment where the initial template concentration is known as proof of principle and apply our method on directly monitoring transcript level change during cell differentiation as well as gauging amplicon numbers in cDNA samples after pre-amplification. PMID:25104023

Mojtahedi, Mitra; Fouquier d'Hérouël, Aymeric; Huang, Sui

2014-01-01

248

Spatial distribution and temporal variation of Microcystis species composition and microcystin concentration in Lake Biwa.  

PubMed

Spatial and temporal variation in Microcystis species composition and microcystin concentration, quantified by enzyme-linked immunosorbent assay and high-performance liquid chromatography, were investigated during a 3-year period (1998-2000) in the Northern Basin of Lake Biwa. The Northern Basin generally had a concentration of 5 microg L(-1) or less, except at station 1 (Nagahama Bay) from July to October during the study period. The maximum concentration at station 1 was 22.7, 35.9, and 22.0 microg L(-1) in October of 1998, 1999, and 2000, respectively. Eleven species of cyanobacteria were observed: Microcystis aeruginosa, M. ichthyoblabe, M. novacekii, M. wesenbergii, Oscillatoria raciborskii, Anabaena oumiana, A. affinis, A. flos-aquae, A. ucrainica, A. smithii, and A. crassa. Of these, M. aeruginosa and M. wesenbergii were the main components observed. A high concentration of microcystin in the lake water was mostly a result of variation in the relative amount of toxic M. aeruginosa rather than of the total Microcystis cell number. This was supported by the analytical results for isolated strains. Microcystis spp. cell density in the Northern Basin appeared to increase gradually over the course of the study. This is the first study to have surveyed the Northern Basin of Lake Biwa, which supplies drinking water to 14 million people and is the largest lake in Japan. PMID:15892068

Ozawa, Kazuhiko; Fujioka, Hiroki; Muranaka, Minoru; Yokoyama, Atsushi; Katagami, Yukimi; Homma, Takamitsu; Ishikawa, Kanako; Tsujimura, Shigeo; Kumagai, Michio; Watanabe, Mariyo F; Park, Ho-Dong

2005-06-01

249

THE SPATIAL DISTRIBUTION OF PHYTOPLANKTON CHLOROPHYLL CONCENTRATIONS IN NARRAGANSETT BAY USING AIRCRAFT REMOTE SENSING  

EPA Science Inventory

During the summer of 2002, phytoplankton chlorophyll concentrations were determined in Narragansett Bay, Rhode Island using a light aircraft equipped with the MicroSAS remote sensing system. From an altitude of 300 m, the three sensor system measured sea surface radiance (Lt), sk...

250

Distribution and Diversity of Escherichia and Salmonella isolates obtained from beef cattle concentrated animal feeding operations  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Southern High Plains are home to numerous cattle feedlots containing approximately 3.5 million beef cattle that account for nearly 30% of the United States fed beef cattle operations. The high density of beef cattle results in a concentration of nutrients (C, N, and P) due to the generation of m...

251

CONCENTRATIONS AND PHASE DISTRIBUTIONS OF NITRATED AND OXYGENATED POLYCYCLIC AROMATIC HYDROCARBONS IN AMBIENT AIR  

EPA Science Inventory

The concentrations of nitrated and oxygenated aromatic hydrocarbons (PAH) in ambient air, both in the vapor phase and adsorbed on airborne particles, were measured over a 12-month period in Houston, Texas. easonal variations in the levels of the target compounds were weakly relat...

252

Airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in Aichi prefecture, Japan.  

PubMed

Airborne fiber concentrations and size distributions of both asbestos and nonasbestos fibers were determined at property boundaries of 4 serpentinite quarries producing crushed stone (quarry property boundary), 10 sites within 10 km of the area with serpentinite outcrops (serpentinite area), and 2 sites in a reference area. The asbestos was identified in 7 rock and 3 soil samples collected in the serpentinite area. The geometric means of airborne concentrations of asbestos and nonasbestos fibers longer than 0.2 microm in length were: 384 and 447 fibers/liter (f/L) in the quarry property boundary (in operation), 12 and 124 f/L in the quarry property boundary (in closed), 5 and 103 fibers/liter in the serpentinite area, and less than 2 and 59 fibers/liter in the reference area, respectively. There was a significant difference in airborne concentrations of both asbestos and nonasbestos fibers among the areas. Ttremolite/actinolite were found with chrysotile in the stones. Airborne concentrations of tremolite/actinolite were higher than those of chrysotile at the quarry property boundary and in the serpentinite area. Tremolite/actinolite were also found in the soils. There was no significant difference among the areas in the arithmetic means of fiber size distribution of both asbestos and nonasbestos fibers. PMID:11341543

Sakai, K; Hisanaga, N; Kohyama, N; Shibata, E; Takeuchi, Y

2001-04-01

253

Natural Radioactivity of Boron Added Clay Samples  

NASA Astrophysics Data System (ADS)

Clay, consisting fine-grained minerals, is an interesting materials and can be used in a variety of diferent fields especially in dermatology application. Using clay such a field it is important to measure its natural radioacitivty. Thus the purpose of this study is to measure 226Ra, 232Th and 40K concentration in clay samples enriched with boron. Three different types of clay samples were prepared where boron is used in different rate. The measurements have been determined using a gamma-ray spectrometry consists of a 3?×3? NaI(Tl) detector. From the measured activity the radium equivalent activities (Raeq), external hazard index (Hex), absorbed dose rate in air (D) and annual effective dose (AED) have also been obtained.

Akkurt, I.; ?anakci?, H.; Mavi, B.; Güno?lu, K.

2011-12-01

254

Natural Radioactivity of Boron Added Clay Samples  

SciTech Connect

Clay, consisting fine-grained minerals, is an interesting materials and can be used in a variety of different fields especially in dermatology application. Using clay such a field it is important to measure its natural radioactivity. Thus the purpose of this study is to measure {sup 226}Ra, {sup 232}Th and {sup 40}K concentration in clay samples enriched with boron. Three different types of clay samples were prepared where boron is used in different rate. The measurements have been determined using a gamma-ray spectrometry consists of a 3''x3'' NaI(Tl) detector. From the measured activity the radium equivalent activities (Ra{sub eq}), external hazard index (H{sub ex}), absorbed dose rate in air (D) and annual effective dose (AED) have also been obtained.

Akkurt, I.; Guenoglu, K. [Sueleyman Demirel University, Faculty of Arts and Sciences, Dept. of Physics, Isparta (Turkey); Canakcii, H. [Gaziantep University, Engineering Faculty, Civil Engineering Dept., Gaziantep (Turkey); Mavi, B. [Amasya University, Faculty of Arts and Sciences, Dept. of Physics, Amasya (Turkey)

2011-12-26

255

Indoor radon concentration data: Its geographic and geologic distribution, an example from the Capital District, NY  

Microsoft Academic Search

Most studies of the geographic distribution of indoor radon levels are plotted by county or ZIP code. This method is used for the radon potential maps produced by the U.S. Environmental Protection Agency (EPA) and the New York State Department of Health (NYSDOH). The basis for the mapping is the mean or median indoor radon count for all the data

J. J. Thomas; H. M. Overeynder; B. R. Thomas

1995-01-01

256

Concentration distribution and viscosity of ice-slurry in heterogeneous flow  

Microsoft Academic Search

Mathematical modeling of two phase flows, especially liquid–solid flows is very complex. Especially when a distribution of the solid phase in a carrier liquid is not homogenous but heterogeneous or even when a moving or stationary bed occurs. In this case, the rheological characteristics of suspension are changing and affect transport characteristics. Therefore, the slurry flow may present a Newtonian

Andrej Kitanovski; Alojz Poredoš

2002-01-01

257

Boron Nitride Nanomesh  

Microsoft Academic Search

A highly regular mesh of hexagonal boron nitride with a 3-nanometer periodicity and a 2-nanometer hole size was formed by self-assembly on a Rh(111) single crystalline surface. Two layers of mesh cover the surface uniformly after high-temperature exposure of the clean rhodium surface to borazine (HBNH)3. The two layers are offset in such a way as to expose a minimum

Martina Corso; Willi Auwärter; Matthias Muntwiler; Anna Tamai; Thomas Greber; Jürg Osterwalder

2004-01-01

258

Structural Modification in Carbon Nanotubes by Boron Incorporation  

PubMed Central

We have synthesized boron-incorporated carbon nanotubes (CNTs) by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm?1in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon–carbon bonds. PMID:20596333

2009-01-01

259

Facile Synthesis of Ternary Boron Carbonitride Nanotubes  

PubMed Central

In this study, a novel and facile approach for the synthesis of ternary boron carbonitride (B–C–N) nanotubes was reported. Growth occurred by heating simple starting materials of boron powder, zinc oxide powder, and ethanol absolute at 1150 °C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B–C–N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor–liquid–solid (VLS) mechanism was proposed for the growth of the nanotubes. PMID:20596377

2009-01-01

260

Towards an understanding of deep boron: study of type IIb blue diamonds  

NASA Astrophysics Data System (ADS)

Boron concentration and isotopic signature are known as a tracer of recycled crustal material from subduction zones inside the Earth's mantle. Thus far, the focus has been on analyzing boron in volcanic rocks and olivine inclusions. However, these materials always experience some degree of late processing on their way to the surface (alteration, crystallization, change in structure, etc.). As of now, the boron content and isotopic ratio of the mantle end-member is only assumed through mass balance calculations (Chaussidon & Marty, 1995). Diamonds, on the other hand, would be a more ideal material to analyze for boron, as it does not undergo significant processing while on its way to the surface. Boron-containing diamonds are well known but extremely rare; they are referred as type IIb diamonds. They are highly valuable in the gem market, as the presence of boron in the diamond structure gives rise to the blue color, such as in the Hope diamond. Only a few boron analyses have been undertaken on type IIb natural diamonds, however, it is generally accepted that their boron concentration is ~1 ppm or lower. The combination of rarity, high value, and low boron content are the most likely reasons why geologists have not yet performed boron analyses on blue diamonds. This study used various spectroscopic methods and time-of-fight (ToF-) SIMS, which are non- or nearly non-destructive techniques, to characterize and analyze for boron in natural type IIb blue diamonds, including the well-known Hope diamond. Results obtained by Fourier Transform Infrared (FTIR) and phosphorescence spectroscopies on 103 diamonds will be presented and compared to some analyses of boron contents measured using ToF-SIMS. ToF-SIMS analyses gave spot (50 x 50 ?m x few nm deep) boron concentrations as high as 8.4 ± 1.1 (atomic) ppm for the Hope diamond to less than 0.08 ppm in other blue diamonds, with an overall average value of ~1 ppm. ToF-SIMS analyses revealed strong zoning of boron in some diamonds, which was confirmed by mapping active boron using synchrotron FTIR. ToF-SIMS gives the spectrum of all the masses at once, so both 11B and 10B were detected. However, the counts on 10B were too low at the counting time we used (several hours) to provide significant ?11B measurements. We observed that there is not a strong correlation between the amount of boron and the color intensity in type IIb diamonds (Gaillou et al., 2012). However, the deep-blue colored diamonds are always associated with a "high" boron content, and therefore, future attempted measurements of boron isotopic ratios should be conducted on deep blue (and unfortunately, valuable) diamonds, using either a much longer counting time, or a different ion mass spectrometer (with different standards), that would consume more material. This study shows that the range of boron concentration, even if in the lower range of instrument detectability, should soon be able to provide boron isotopic measurements, and perhaps gives insights into the origin of boron in diamonds, e.g. from a subducted slab and/or from primitive mantle reservoir. Chaussidon M., Marty B. (1995) Primitive boron isotope composition of the mantle, Science, 269, 383-386. Gaillou E., Rost D., Post J.E., Butler J.E. (2012) Boron in natural type IIb blue diamonds: chemical and spectroscopic measurements. Am. Min., 1, 1-18.

Gaillou, E.; Rost, D.; Post, J. E.; Butler, J. E.

2012-12-01

261

Characterization of concentration, particle size distribution, and contributing factors to ambient hexavalent chromium in an area with multiple emission sources  

NASA Astrophysics Data System (ADS)

Airborne hexavalent chromium (Cr(VI)) is a known pulmonary carcinogen and can be emitted from both natural and anthropogenic sources, including diesel emissions. However, there is limited knowledge about ambient Cr(VI) concentration levels and its particle size distribution. This pilot study characterized ambient Cr(VI) concentrations in the New Jersey Meadowlands (NJ ML) district, which is close to the heavily trafficked New Jersey Turnpike (NJTPK) as well as Chromium Ore Processing Residue (COPR) waste sites. Monitoring was simultaneously conducted at two sites, William site (?50 m from NJTPK) and MERI site (?700 m from NJTPK). The distance between the two sites is approximately 6.2 km. Ambient Cr(VI) concentrations and PM2.5 mass concentrations were concurrently measured at both sites during summer and winter. The summer concentrations (mean ± S.D. [median]), 0.13 ± 0.06 [0.12] ng/m3 at the MERI site and 0.08 ± 0.05 [0.07] ng/m3 at the William site, were all significantly higher than the winter concentrations, 0.02 ± 0.01 [0.02] ng/m3 and 0.03 ± 0.01 [0.03] ng/m3 at the MERI and William sites, respectively. The site difference (i.e., MERI > William) was observed for summer Cr(VI) concentrations; however, no differences for winter and pooled datasets. These results suggest higher Cr(VI) concentrations may be attributed from stronger atmospheric reactions such as photo-oxidation of Cr(III) to Cr(VI) in the summer. The Cr(VI) distribution as a function of particle size, ranging from 0.18 to 18 ?m, was determined at the William site. It was found that Cr(VI) was enriched in the particles less than 2.5 ?m in diameter (PM2.5). This finding suggested potential health concerns, because PM2.5 are easily inhaled and deposited in the alveoli. A multiple linear regression analysis confirmed ambient Cr(VI) concentrations were significantly affected by meteorological factors (i.e., temperature and humidity) and reactive gases/particles (i.e., O3, Fe and Mn).

Yu, Chang Ho; Huang, Lihui; Shin, Jin Young; Artigas, Francisco; Fan, Zhi-hua (Tina)

2014-09-01

262

Caenorhabditis elegans Maintains Highly Compartmentalized Cellular Distribution of Metals and Steep Concentration Gradients of Manganese  

PubMed Central

Bioinorganic chemistry is critical to cellular function. Homeostasis of manganese (Mn), for example, is essential for life. A lack of methods for direct in situ visualization of Mn and other biological metals within intact multicellular eukaryotes limits our understanding of management of these metals. We provide the first quantitative subcellular visualization of endogenous Mn concentrations (spanning two orders of magnitude) associated with individual cells of the nematode, Caenorhabditis elegans. PMID:22393436

Mayo, Sheridan; Howard, Daryl L.; Ryan, Christopher G.; Kirkham, Robin; Moorhead, Gareth F.; Paterson, David; de Jonge, Martin D.; Bush, Ashley I.

2012-01-01

263

Urinary phthalate metabolite concentrations among pregnant women in Northern Puerto Rico: Distribution, temporal variability, and predictors  

PubMed Central

Background Phthalate contamination exists in the North coast karst aquifer system in Puerto Rico. In light of potential health impacts associated with phthalate exposure, targeted action for elimination of exposure sources may be warranted, especially for sensitive populations such as pregnant women. However, information on exposure to phthalates from a variety of sources in Puerto Rico is lacking. The objective of this study was to determine concentrations and predictors of urinary phthalate biomarkers measured at multiple times during pregnancy among women living in the Northern karst area of Puerto Rico. Methods We recruited 139 pregnant women in Northern Puerto Rico and collected urine samples and questionnaire data at three separate visits (18±2 weeks, 22±2 weeks, and 26±2 weeks of gestation). Urine samples were analyzed for eleven phthalate metabolites: mono-2-ethylhexyl phthalate (MEHP), mono-2-ethyl-5-hydroxyhexyl phthalate, mono-2-ethyl-5-oxohexyl phthalate, mono-2-ethyl-5-carboxypentyl phthalate, mono-ethyl phthalate (MEP), mono-n-butyl phthalate, mono-benzyl phthalate, mono-isobutyl phthalate, mono-3-carboxypropyl phthalate (MCPP), mono carboxyisononyl phthalate (MCNP), and mono carboxyisooctyl phthalate (MCOP). Results Detectable concentrations of phthalate metabolites among pregnant women living in Puerto Rico was prevalent, and metabolite concentrations tended to be higher than or similar to those measured in women of reproductive age from the general US population. Intraclass correlation coefficients ranged from very weak (MCNP; 0.05) to moderate (MEP; 0.44) reproducibility among all phthalate metabolites. We observed significant or suggestive positive associations between urinary phthalate metabolites concentrations and water usage/storage habits (MEP, MCNP, MCOP), use of personal care products (MEP), and consumption of certain food items (MCPP, MCNP, and MCOP). Conclusions To our knowledge this is the first study to report concentrations, temporal variability, and predictors of phthalate biomarkers among pregnant women in Puerto Rico. Preliminary results suggest several potentially important exposure sources to phthalates in this population and future analysis from this ongoing prospective cohort will help to inform targeted approaches to reduce exposure. PMID:24161445

Cantonwine, David E.; Cordero, José F.; Rivera-González, Luis O.; Del Toro, Liza V. Anzalota; Ferguson, Kelly K.; Mukherjee, Bhramar; Calafat, Antonia M.; Crespo, Noe; Jiménez-Vélez, Braulio; Padilla, Ingrid Y.; Alshawabkeh, Akram N.; Meeker, John D.

2013-01-01

264

Effect of solids concentration distribution on the flue gas desulfurization process  

Microsoft Academic Search

A dry flue gas desulfurization (FGD) process at 600-800{sup o}C was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. Various fresh sorbent distribution types and internal structures were modeled numerically to investigate their effect on the gas-solid flow and sulfate reaction characteristics. Experimental results show that, after the fresh sorbent supply was stopped, the desulfurization efficiency declined rapidly

Jie Zhang; Changfu You; Haiying Qi; Changhe Chen; Xuchang Xu

2006-01-01

265

Relationships between stream nitrate concentration and spatially distributed snowmelt in high-elevation catchments of the western U.S.  

NASA Astrophysics Data System (ADS)

study compares stream nitrate (NO3-) concentrations to spatially distributed snowmelt in two alpine catchments, the Green Lakes Valley, Colorado (GLV4) and Tokopah Basin, California (TOK). A snow water equivalent reconstruction model and Landsat 5 and 7 snow cover data were used to estimate daily snowmelt at 30 m spatial resolution in order to derive indices of new snowmelt areas (NSAs). Estimates of NSA were then used to explain the NO3- flushing behavior for each basin over a 12 year period (1996-2007). To identify the optimal method for defining NSAs and elucidate mechanisms underlying catchment NO3- flushing, we conducted a series of regression analyses using multiple thresholds of snowmelt based on temporal and volumetric metrics. NSA indices defined by volume of snowmelt (e.g., snowmelt ? 30 cm) rather than snowmelt duration (e.g., snowmelt ? 9 days) were the best predictors of stream NO3- concentrations. The NSA indices were better correlated with stream NO3- concentration in TOK (average R2= 0.68) versus GLV4 (average R2= 0.44). Positive relationships between NSA and stream NO3- concentration were observed in TOK with peak stream NO3- concentration occurring on the rising limb of snowmelt. Positive and negative relationships between NSA and stream NO3- concentration were found in GLV4 with peak stream NO3- concentration occurring as NSA expands. Consistent with previous works, the contrasting NO3- flushing behavior suggests that streamflow in TOK was primarily influenced by overland flow and shallow subsurface flow, whereas GLV4 appeared to be more strongly influenced by deeper subsurface flow paths.

Perrot, Danielle; Molotch, Noah P.; Williams, Mark W.; Jepsen, Steven M.; Sickman, James O.

2014-11-01

266

Concentration, distribution, and human health risk assessment of endosulfan from a manufacturing facility in Huai'an, China.  

PubMed

Endosulfan concentrations and its distribution in air, soil, sediment and foodstuffs in the area surrounding a production facility in Huai'an, China were investigated because of its threats to the environment and human health. Air concentrations for endosulfan ?, endosulfan II and endosulfan sulfate measured in this study were several orders of magnitude higher than those reported previously for this region. Surface soil concentration ranges of endosulfan I, endosulfan II, and endosulfan sulfate were greater than in sediment. Endosulfan II was the greatest contributor to total endosulfan concentrations in both surface sediment and soil followed by endosulfan sulfate and endosulfan ?. However, a different concentration profile was observed in fish and crop samples, with endosulfan sulfate having the highest concentration followed by endosulfan I and endosulfan II. The concentration of ?endosulfans (endosulfans ? and II) in soil decreased rapidly with increasing distance from the plant by a factor of 10 within 45 km. Trace amounts of ?endosulfans were observed in deep soil layers which implied that these compounds are transported through the leaching of pore water in soil. This demonstrated that emissions from the manufacturing facility can lead to ground water contamination in the area near the plant. A screening level human health risk assessment of ?endosulfans based on the worst-case scenario was performed for people living in the vicinity of the manufacturing facility. The hazard indices were at least 2 orders of magnitude of <1, indicating no adverse health effects are likely to occur at current exposure levels, and the risk to human health is generally acceptable. PMID:24491393

Wang, De-Gao; Alaee, Mehran; Guo, Ming-Xing; Pei, Wei; Wu, Qian

2014-09-01

267

In situ boron nitride coating and comparison with existing boronizations  

NASA Astrophysics Data System (ADS)

Two new types of boronization were demonstrated in a laboratory apparatus bakable up to 350°C: (i) amorphous boron nitride films (B/N?1) were deposited by a dc glow discharge of a 0.1 B 2H 6+0.3 N 2+0.6 He mixture, and (ii) decaborane B 10H 14, a less hazardous powder, was used to deposit pure boron films. A feasibility boronization of fusion devices with the new method was demonstrated by basic experiments on hydrogen recycling, helium glow conditioning, and oxygen gettering. In the laboratory experiment, time variations in relevant partial pressures were measured in pulsed glow discharges in D 2, He, and 1% O 2/He. Standard boronization and carbonization using B 2H 6 and/or CH 4 were also done in an identical apparatus at the same temperature (150 or 300°C). A comparison among them revealed that the boron nitride coating is a new candidate competing with existing boronizations. The first results of boronization using decaborane indicate the new technique to be easy and safe for hadling.

Yamage, M.; Ejima, T.; Toyoda, H.; Sugai, H.

1992-12-01

268

Thermal conductivity of boron carbide-boron nitride composites  

Microsoft Academic Search

This paper reports that because of their preferred orientation, the addition of boron nitride dispersions to hot-pressed boron carbide was found to result in a considerable degree of anisotropy in thermal conductivity of the resulting composite, indicated by an increase in the thermal conductivity perpendicular to the hot-pressing direction by as much as a factor of 3 at the highest

Robert Ruh; Kimberly Y. Donaldson; D. P. H. Hasselman

1992-01-01

269

Experimental and Numerical Simulation of Boron Transport in a Nuclear Reactor Vessel  

NASA Astrophysics Data System (ADS)

The Westinghouse AP600 reactor design uses a gravity -forced safety injection system with nozzles in the vessel downcomer. In the event of overcooling transients, this system delivers soluble boron to the core to offset moderator defect reactivity. To evaluate the outcome of a design basis overcooling event, a tool to predict the transport of boron to the core was required. A hybrid computational fluid dynamic/fluid element tracking model was developed for this task. In this technique, the loop and safety injection flow was determined by the 1-D system code LOFTRAN. From these boundary conditions, the reactor vessel steady-state velocity field and k- varepsilon turbulence parameters were found using the 3-D computational fluid dynamics code FLOTRAN. These pointwise values were used to define the flow field characteristics in a fluid element tracking model. In this random walk model, the k-varepsilon values at a point were used to find a local turbulent diffusion time scale and a distribution of length scales. A distribution of molecular diffusion length scales were also generated. Fluid element motion was determined by combining the deterministic convective transport during a time interval with turbulent and molecular diffusion components chosen randomly from the distributions. The transient concentration distribution was determined from the time and position of the elements as they reached the core inlet. A scaling analysis of the reactor system showed that buoyancy and turbulent diffusion effects were of equal importance during overcooling transient conditions. A 1:9 scale model was constructed using air and dense gas to simulate the reactor coolant and safety injection fluid. Experiments were performed with velocities chosen to give Richardson and mixing Reynolds number scaling. Concentration of the dense gas was measured at the core inlet using a sonic nozzle/hot film anemometer instrument. The results of these experiments were used to validate the numerical model. Overall, the model was capable of predicting the experimental transient concentration distribution very well, with the exception of underprediction of the lower concentration values, for experiments with Richardson or mixing Reynolds scaling. With this validation, the model should be capable of predicting boron transport in the reactor.

Radcliff, Thomas Dean

1995-01-01

270

Effect of traffic restriction on atmospheric particle concentrations and their size distributions in urban Lanzhou, Northwestern China.  

PubMed

During the 2012 Lanzhou International Marathon, the local government made a significant effort to improve traffic conditions and air quality by implementing traffic restriction measures. To evaluate the direct effect of these measures on urban air quality, especially particle concentrations and their size distributions, atmospheric particle size distributions (0.5-20 microm) obtained using an aerodynamic particle sizer (model 3321, TSI, USA) in June 2012 were analyzed. It was found that the particle number, surface area and volume concentrations for size range 0.5-10 microm were (15.0 +/- 2.1) cm(-3), (11.8 +/- 2.6) microm2/cm3 and (1.9 +/- 0.6) microm2/cm3, respectively, on the traffic-restricted day (Sunday), which is 63.2%, 53.0% and 47.2% lower than those on a normal Sunday. For number and surface area concentrations, the most affected size range was 0.5-0.7 and 0.5-0.8 microm, respectively, while for volume concentration, the most affected size ranges were 0.5-0.8, 1.7-2.0 and 5.0-5.4 microm. Number and volume concentrations of particles in size range 0.5-1.0 microm correlated well with the number of non-CNG (Compressed Natural Gas) powered vehicles, while their correlation with the number of CNG-powered vehicles was very low, suggesting that reasonable urban traffic controls along with vehicle technology improvements could play an important role in improving urban air quality. PMID:25076527

Zhao, Suping; Yu, Ye; Liu, Na; He, Jianjun; Chen, Jinbei

2014-02-01

271

Radiation transmission of concrete including boron waste for 59.54 and 80.99 keV gamma rays  

NASA Astrophysics Data System (ADS)

Accurate measurement have been made to determine radiation transmission of boron compounds by using an extremely narrow collimated beam transmission method for 59.54 and 80.99 keV gamma energy with a Si(Li) detector. Appreciable variations were observed in the transmission factors of the concrete samples including different boron wastes (borogypsum and colemanite concentrator waste). Additionally, mass attenuation coefficients were also calculated. It is seen that ?/ ? is increased with increasing boron concentration in the concrete and the both kind of boron waste have nearly the same property in the radiation transmission.

Demir, Demet; Kele?, Gürbüz

2006-04-01

272

Improving Simulations of Fine Dust Surface Concentrations over the Western United States by Optimizing the Particle Size Distribution  

SciTech Connect

To improve estimates of remote contributions of dust to fine particulate matter (PM2.5) in the western United States, new dust particle size distributions (PSDs) based upon scale-invariant fragmentation theory (Kok_PSD) with constraints from in situ measurements (IMP_PSD) are implemented in a chemical transport model (GEOS-Chem). Compared to initial simulations, this leads to reductions in the mass of emitted dust particles with radii <1.8 mm by 40%-60%. Consequently, the root-mean-square error in simulated fine dust concentrations compared to springtime surface observations in the western United States is reduced by 67%-81%. The ratio of simulated fine to coarse PM mass is also improved, which is not achievable by reductions in total dust emissions. The IMP_PSD best represents the PSD of dust transported from remote sources and reduces modeled PM2.5 concentrations up to 5 mg/m3 over the western United States, which is important when considering sources contributing to nonattainment of air quality standards. Citation: Zhang, L., J. F. Kok, D. K. Henze, Q. Li, and C. Zhao (2013), Improving simulations of fine dust surface concentrations over the western United States by optimizing the particle size distribution, Geophys. Res. Lett., 40, 3270-3275, doi:10.1002/grl.50591.

Zhang, Li; Kok, Jasper F.; Henze, Daven; Li, Qinbin; Zhao, Chun

2013-06-28

273

Nuclear reaction secondary particle dose distributions and dose enhancement by boron neutron capture in proton beam therapy evaluated using the LAHET code system  

Microsoft Academic Search

The objective of this study was to use the LAHET Code System (LCS), which has recently been used in shielding calculations for proton therapy, to model the proton, neutron and photon dose and equivalent dose distributions created in tissue during proton beam cancer therapy. Proton beams used for therapy have shown distinct advantages over other therapeutic radiation treatments due to

Peter Gyula Laky

1997-01-01

274

BORON ANALYSIS IN TISSUES BEFORE APPLE TREE BLOOM CAN BE USED TO ASSESS BORON NUTRITIONAL STATUS  

Microsoft Academic Search

The aim of this study was to examine relationships between boron (B) concentrations in flower buds, spur leaves, and flowers and B in leaves of one-year-old shoots. The experiment was carried out during 1997–1999 in the Experimental Orchard of the Research Institute of Pomology and Floriculture in Skierniewice, Poland on mature “Jonagold” and “Gala” apple (Malus domestica Borkh.) trees grafted

Pawel Wojcik

2002-01-01

275

Concentrations and Distribution of Trace Metals in Water and Streambed Sediments of Orogodo River, Southern Nigeria  

Microsoft Academic Search

The distribution of Cd, Pb, Ni, Cr, Cu, Mn, Fe, and Zn in sediment and surface water, and some physico-chemical characteristics of Orogodo river sediments, were evaluated. The sediment pH ranged from 5.1–7.3; conductivity values ranged from 34.5 to 389.0 ?Scm. Total nitrogen values ranged from 0.06–0.10%, NH3-N values ranged from 0.25–0.44 mgkg, percent total organic carbon ranged from 0.21–1.68%,

Chukwujindu M. A. Iwegbue; Francis O. Arimoro; Godwin E. Nwajei; Osayonmo I. Eguavoen

2012-01-01

276

3D Trace gas concentration distributions from groundbased and airborne tomographic DOAS measurements  

NASA Astrophysics Data System (ADS)

An overview on the AFO-2000 project "Tom-DOAS" is given. The project aims the assessment of concentration maps from DOAS measurements performed from ground or aircraft with more than ten light beams. 1) A first ground-based experiment was set up in April/May 2001 during the motorway campaign BABII (organised by Fiedler et al.): Two DOAS telescopes were directed onto eight retro reflector arrays mounted on two cranes, providing 16 light beams in total. From the data Luff and Lee profiles and the emission plumes of NO2 and ozone could be derived. 2) A new telescope type, the Multibeam telescope, was developed for the simultaneous measurement of multiple paths at ground. 3) An aircraft instrument was developed and about 20 flight hours of Tom-DOAS measurements were performed onboard a Partenavia aircraft in the Milano area (Italy) in the frame of the EU "FORMAT" project (July/August 2002) - in co-operation with the Institut für Umweltphysik of the University of Bremen 4) A new inversion software, "TOMOLAB", was developed, which converts the DOAS column data to concentration maps. It is used for the optimisation of tomographic setups using model data, e.g. for flight track choices, as well as for the inversion of real data sets from the measurements.

Pundt, I.; Hak, C.; Hartl, A.; Heue, K.-P.; Knab, V.; Kunz, C.; Laepple, T.; Lee, W.-D.; Mettendorf, K. U.; Sun, H.

2003-04-01

277

A high boronate avidity monolithic capillary for the selective enrichment of trace glycoproteins.  

PubMed

Boronate affinity materials, as effective sample enrichment sorbents for glycoproteomic analysis, have attracted increasing attention in recent years. However, most of boronate affinity materials suffer from an apparent limitation, limited binding strength. As a result, extraction of glycoproteins of trace concentration is rather difficult or impossible. In this study, we present a high boronate avidity monolithic capillary. Branched polyethyleneimine (PEI) was used as a scaffold to amplify the number of boronic acid moieties. While 2,4-difluoro-3-formyl-phenylboronic acid (DFFPBA), which exhibited ultrahigh affinity toward cis-diol-containing compounds, was employed as an affinity ligand. Due to the PEI-assisted synergistic multivalent binding, the monolithic column exhibited high boronate avidity toward glycoproteins, with binding constants of 10(-6)-10(-7)M. Such binding strength was the highest among already reported boronic acid-functionalized materials that can be used for glycoproteomic analysis. Besides, the boronate avidity monolithic column exhibited one additional beneficial feature, lowered binding pH (?6.5). These features greatly favored the selective enrichment of trace glycoproteins from real samples. The feasibility for practical applications was demonstrated with the selective enrichment of trace glycoproteins in human saliva. As compared with other boronate avidity/affinity materials, the boronate avidity monolithic capillary exhibited the best performance. PMID:25638264

Li, Daojin; Li, Yang; Li, Xinglin; Bie, Zijun; Pan, Xianghua; Zhang, Qian; Liu, Zhen

2015-03-01

278

Preliminary weight and costs of sandwich panels to distribute concentrated loads  

NASA Technical Reports Server (NTRS)

Minimum mass honeycomb sandwich panels were sized for transmitting a concentrated load to a uniform reaction through various distances. The form skin gages were fully stressed with a finite element computer code. The panel general stability was evaluated with a buckling computer code labeled STAGS-B. Two skin materials were considered; aluminum and graphite-epoxy. The core was constant thickness aluminum honeycomb. Various panel sizes and load levels were considered. The computer generated data were generalized to allow preliminary least mass panel designs for a wide range of panel sizes and load intensities. An assessment of panel fabrication cost was also conducted. Various comparisons between panel mass, panel size, panel loading, and panel cost are presented in both tabular and graphical form.

Belleman, G.; Mccarty, J. E.

1976-01-01

279

Concentration and distribution of antibiotics in water-sediment system of Bosten Lake, Xinjiang.  

PubMed

This study investigated the residues of four sulfonamides, four quinolones, and four tetracyclines in surface water as well as surficial sediment samples, of Bosten Lake, in Xinjiang, China. The results showed the presence of 10 out of the 12 selected antibiotics in both water and sediment. Lomefloxacin was not detected in any of the samples. Among the 12 antibiotics considered, ciprofloxacin, with median concentrations of 39.22 ng L(-1) in surface water and 76.51 ?g kg(-1) in surficial sediment, was the dominant antibiotic in all samples. The sorption coefficient values presented higher sorption capacities of tetracycline and chlortetracycline than the other antibiotics. The cluster analysis revealed elevated levels of pollution in sampling sites 1, 2, and 3, which were situated in a nearby urban area and in the estuary of Kaidu River. This study demonstrates the necessity of regulating the use of antibiotics and improving the management and treatment of their release. PMID:24809500

Lei, Xiaoning; Lu, Jianjiang; Liu, Zilong; Tong, Yanbin; Li, Shanman

2015-02-01

280

The place of solar power: an economic analysis of concentrated and distributed solar power  

PubMed Central

Background This paper examines the cost and benefits, both financial and environmental, of two leading forms of solar power generation, grid-tied photovoltaic cells and Dish Stirling Systems, using conventional carbon-based fuel as a benchmark. Methods First we define how these solar technologies will be implemented and why. Then we delineate a model city and its characteristics, which will be used to test the two methods of solar-powered electric distribution. Then we set the constraining assumptions for each technology, which serve as parameters for our calculations. Finally, we calculate the present value of the total cost of conventional energy needed to power our model city and use this as a benchmark when analyzing both solar models’ benefits and costs. Results The preeminent form of distributed electricity generation, grid-tied photovoltaic cells under net-metering, allow individual homeowners a degree of electric self-sufficiency while often turning a profit. However, substantial subsidies are required to make the investment sensible. Meanwhile, large dish Stirling engine installations have a significantly higher potential rate of return, but face a number of pragmatic limitations. Conclusions This paper concludes that both technologies are a sensible investment for consumers, but given that the dish Stirling consumer receives 6.37 dollars per watt while the home photovoltaic system consumer receives between 0.9 and 1.70 dollars per watt, the former appears to be a superior option. Despite the large investment, this paper deduces that it is far more feasible to get few strong investors to develop a solar farm of this magnitude, than to get 150,000 households to install photovoltaic arrays in their roofs. Potential implications of the solar farm construction include an environmental impact given the size of land require for this endeavour. However, the positive aspects, which include a large CO2 emission reduction aggregated over the lifespan of the farm, outweigh any minor concerns or potential externalities. PMID:22540991

2012-01-01

281

Functionalized boron nitride nanotubes  

DOEpatents

A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

2014-04-22

282

Transmembrane partitioning of boron and other elements in RAW 264.7 and HL60 cell cultures  

Microsoft Academic Search

The trace element boron is essential for all higher plants and is beneficial or has been established as essential for several\\u000a animal models of human nutrition. To help identify the biomolecules that require boron for function in humans, we determined\\u000a whether intracellular boron is retained against a concentration gradient. Cells (Abelson leukemia virus BALB murine monocyte-macrophage\\u000a RAW 264.7 [RAW] and

Nicholas V. C. Ralston; Curtiss D. Hunt

2004-01-01

283

The mapping of natural boron in histological sections of mouse tissues by the use of neutron-capture radiography  

Microsoft Academic Search

Summary  Neutron-capture radiography has been applied to the mapping of natural boron in mouse histological sections. The method is based on the fact that the stable isotope boron-10 has an extremely large cross-section for the thermal-neutron reaction10B(n, )7Li. The local tissue boron concentrations were evaluated from the corresponding track densities of the nuclear reaction using an equation derived from a theoretical

Maria Laurent-Pettersson; Bertrand Delpech; Michel Thellier

1992-01-01

284

CIRCE2/DEKGEN2: A software package for facilitated optical analysis of 3-D distributed solar energy concentrators. Theory and user manual  

SciTech Connect

CIRCE2 is a computer code for modeling the optical performance of three-dimensional dish-type solar energy concentrators. Statistical methods are used to evaluate the directional distribution of reflected rays from any given point on the concentrator. Given concentrator and receiver geometries, sunshape (angular distribution of incident rays from the sun), and concentrator imperfections such as surface roughness and random deviation in slope, the code predicts the flux distribution and total power incident upon the target. Great freedom exists in the variety of concentrator and receiver configurations that can be modeled. Additionally, provisions for shading and receiver aperturing are included.- DEKGEN2 is a preprocessor designed to facilitate input of geometry, error distributions, and sun models. This manual describes the optical model, user inputs, code outputs, and operation of the software package. A user tutorial is included in which several collectors are built and analyzed in step-by-step examples.

Romero, V.J.

1994-03-01

285

Impact of spectral irradiance distribution and temperature on the outdoor performance of concentrator photovoltaic system  

NASA Astrophysics Data System (ADS)

Multi-junction solar cell is designed to have considerable effect towards the solar spectrum distribution so that the maximum solar radiation could be absorbed hence, enhancing the energy conversion efficiency of the cell. Due to its application in CPV system, the system's characteristics are more sensitive to environmental factor in comparison to flat-plate PV system which commonly equipped with Si-based solar cell. In this paper, the impact of environmental factors i.e. average photon energy (APE) and temperature of solar cell (Tcell) towards the performance of the tracking type CPV system were discussed. A year data period of direct spectral irradiance, cell temperature, and power output which recorded from November 2010 to October 2011 at a CPV system power generator plant located at Miyazaki, Japan was used in this study. The result showed that most frequent condition during operation was at APE = 1.87±0.005eV, Tcell = 65±2.5°C with performance ratio of 83.9%. Furthermore, an equivalent circuit simulation of a CPV subsystem in module unit was conducted in order to investigate the influence of environmental factors towards the performance of the module.

Husna, Husyira Al; Shibata, Naoki; Sawano, Naoki; Ueno, Seiya; Ota, Yasuyuki; Minemoto, Takashi; Araki, Kenji; Nishioka, Kensuke

2013-09-01

286

Blind Deconvolution for Distributed Parameter Systems with Unbounded Input and Output and Determining Blood Alcohol Concentration from Transdermal Biosensor Data.  

PubMed

We develop a blind deconvolution scheme for input-output systems described by distributed parameter systems with boundary input and output. An abstract functional analytic theory based on results for the linear quadratic control of infinite dimensional systems with unbounded input and output operators is presented. The blind deconvolution problem is then reformulated as a series of constrained linear and nonlinear optimization problems involving infinite dimensional dynamical systems. A finite dimensional approximation and convergence theory is developed. The theory is applied to the problem of estimating blood or breath alcohol concentration (respectively, BAC or BrAC) from biosensor-measured transdermal alcohol concentration (TAC) in the field. A distributed parameter model with boundary input and output is proposed for the transdermal transport of ethanol from the blood through the skin to the sensor. The problem of estimating BAC or BrAC from the TAC data is formulated as a blind deconvolution problem. A scheme to identify distinct drinking episodes in TAC data based on a Hodrick Prescott filter is discussed. Numerical results involving actual patient data are presented. PMID:24707065

Rosen, I G; Luczak, Susan E; Weiss, Jordan

2014-03-15

287

Spatial distribution of the electrical potential and ion concentration in the downstream area of atmospheric pressure remote plasma  

NASA Astrophysics Data System (ADS)

This paper presents the results from an experimental study of the ion flux characteristics behind the remote plasma zone in a vertical tube reaction chamber for atmospheric pressure plasma enhanced chemical vapor deposition. Capacitively coupled radio frequency plasma was generated in pure He and gas mixtures: He-Ar, He-O2, He-TEOS. We previously used the reaction system He-TEOS for the synthesis of self-assembled structures of silicon dioxide nanoparticles. It is likely that the electrical parameters of the area, where nanoparticles have been transported from the synthesis zone to the substrate, play a significant role in the self-organization processes both in the vapor phase and on the substrate surface. The results from the spatial distribution of the electrical potential and ion concentration in the discharge downstream area measured by means of the external probe of original design and the special data processing method are demonstrated in this work. Positive and negatives ions with maximum concentrations of 106-107 cm-3 have been found at 10-80 mm distance behind the plasma zone. On the basis of the revealed distributions for different gas mixtures, the physical model of the observed phenomena is proposed. The model illustrates the capability of the virtual ion emitter formation behind the discharge gap and the presence of an extremum of the electrical potential at the distance of approximately 10-2-10-1 mm from the grounded electrode.

Mishin, M. V.; Protopopova, V. S.; Uvarov, A. A.; Alexandrov, S. E.

2014-10-01

288

Spatial distribution of seasonality of SeaWiFS chlorophyll-a concentrations in the East/Japan Sea  

NASA Astrophysics Data System (ADS)

To investigate the spatial characteristics of seasonality in phytoplankton productivity over the entire East/Japan Sea (EJS), a wavelet analysis was applied to SeaWiFS chlorophyll-a (chl-a) data over the period from 1998 to 2007. The wavelet analysis revealed that a 6-month period of change in chl-a concentration, explained by spring and fall blooms, was persistent throughout EJS during the ten years examined. The time series seasonality could be further classified into three patterns: (1) the highest variance peak at the 6-month period, (2) double variance peaks with similar values at the periods of 6- and 12-month, and (3) the highest variance at the 12-month period. A spatial map of the ratios between variances at the 6- and 12-month periods illustrated geographical distribution of the chl-a seasonality patterns. The Japan Basin and Ulleung Warm Eddy area were characterized by pattern 1 associated with clear spring and fall blooms. The region near the sub-polar front had seasonality pattern 2 characterized by two similar, weak blooms, and the area of East Koran Bay and the Yamato Basin are distinguished by pattern 3 with strong spring bloom, but irregular and unnoticeable fall bloom due to relatively high chl-a concentrations in wintertime. Distinct regional distribution of the seasonality patterns may suggest that phytoplankton productivity and its seasonal cycles respond not only to basin-scale or mesoscale climate forcing but also to changes in local physical properties characterizing each region.

Jo, Chun Ok; Park, Sunyoung; Kim, Young Ho; Park, Kyung-Ae; Park, Jong Jin; Park, Mi-Kyung; Li, Shanlan; Kim, Jae-Yeon; Park, Ji-Eun; Kim, Ji-Yoon; Kim, Kyung-Ryul

2014-11-01

289

Free energies, vacancy concentrations and density distribution anisotropies in hard--sphere crystals: A combined density functional and simulation study  

E-print Network

We perform a comparative study of the free energies and the density distributions in hard sphere crystals using Monte Carlo simulations and density functional theory (employing Fundamental Measure functionals). Using a recently introduced technique (Schilling and Schmid, J. Chem. Phys 131, 231102 (2009)) we obtain crystal free energies to a high precision. The free energies from Fundamental Measure theory are in good agreement with the simulation results and demonstrate the applicability of these functionals to the treatment of other problems involving crystallization. The agreement between FMT and simulations on the level of the free energies is also reflected in the density distributions around single lattice sites. Overall, the peak widths and anisotropy signs for different lattice directions agree, however, it is found that Fundamental Measure theory gives slightly narrower peaks with more anisotropy than seen in the simulations. Among the three types of Fundamental Measure functionals studied, only the White Bear II functional (Hansen-Goos and Roth, J. Phys.: Condens. Matter 18, 8413 (2006)) exhibits sensible results for the equilibrium vacancy concentration and a physical behavior of the chemical potential in crystals constrained by a fixed vacancy concentration.

M. Oettel; S. Goerig; A. Haertel; H. Loewen; M. Radu; T. Schilling

2010-09-03

290

Characterization of boron incorporation and speciation in calcite and aragonite from co-precipitation experiments under controlled pH, temperature and precipitation rate  

NASA Astrophysics Data System (ADS)

About 20 years ago, the boron isotopic composition of marine carbonates was proposed as a proxy of ancient seawater pH. Since that time, a large body of studies has used boron isotopes in carbonates to reconstruct seawater paleo-pH and atmospheric paleo-CO2 concentration. To date, however, no systematic investigation of the physicochemical parameters that control boron incorporation in calcite and aragonite (pH, temperature, precipitation rate, etc.) has been performed. To fill this gap, we have experimentally investigated the inorganic co-precipitation of boron with calcite and aragonite at 5 and 25 °C in the presence and absence of seed crystals and over the pHNBS range 7.4 < pH < 9.5 in 0.1 or 0.2 M NaCl solutions. The boron partition coefficient, DB, between CaCO3 and the fluid is defined as: DB = {(XB/XCO3)CaCO3}/([B]/[CO32-])fluid} with Xi and [i] standing for the mole fraction and molality of the ith species in the solid and fluid, respectively. DB measured in this study are very small (DB ? 10-3 and ? 10-4 for aragonite and calcite, respectively) and exhibit a strong dependence on the solution pH and the calcium carbonate precipitation rate. High field 11B MAS NMR analyses of the precipitated carbonates show that boron in aragonite is mostly in the form of tetragonal B (? 85%[IV]B) but that both trigonal and tetragonal B are present in calcite. A significant amount of tetragonal boron in calcite may be in non-lattice (defect) sites, in addition to the structural site. The relative abundance of [III]B and [IV]B in calcite is independent of the parent solution pH but appears to decrease with increasing precipitation rate. The change in boron coordination during its incorporation in calcite and its distribution in, at least, two different sites strongly suggest that the mechanisms controlling B incorporation in this mineral are more complex than for aragonite. It follows that calcite-based calibrations may be less reliable than aragonite calibrations for ocean paleo-pH reconstructions.

Mavromatis, Vasileios; Montouillout, Valérie; Noireaux, Johanna; Gaillardet, Jérôme; Schott, Jacques

2015-02-01

291

Detections, concentrations, and distributional patterns of compounds of emerging concern in the San Antonio River Basin, Texas, 2011-12  

USGS Publications Warehouse

During 2011–12, the U.S. Geological Survey, in cooperation with the San Antonio River Authority, evaluated detections, concentrations, and distributional patterns of selected compounds of emerging concern (hereinafter referred to as “CECs”) from water-quality samples (hereinafter referred to as “samples”) collected at a total of 20 sampling sites distributed throughout the San Antonio River Basin, Texas. Of the 54 wastewater compounds analyzed, 32 were detected in at least one sample collected from the San Antonio River Basin, and 22 of those compounds were not detected in any samples. The flame retardants tris (2-chloroethyl) phosphate and tris (dichloroisopropyl) phosphate, both possible endocrine disruptors, were the most frequently detected wastewater compounds with 28 of the 33 samples analyzed for wastewater compounds having measureable concentrations of those compounds. Of the 13 analyzed pharmaceuticals, 4 compounds were detected in a least one sample. Carbamazepine, an anticonvulsant, was the most frequently detected prescription pharmaceutical with 24 detections in 34 samples analyzed for pharmaceuticals. Of the 17 steroidal hormones, 4 were detected in at least one sample from the San Antonio River Basin. Estrone was detected in 9 of 34 samples analyzed for steroidal hormones, making it the most frequently detected steroidal hormone. Of the 4 sterols, all 4 were detected in at least one sample from the San Antonio River Basin. Cholesterol, detected in 19 of 34 samples analyzed for sterols, was the most frequently detected sterol. Three synoptic sampling events were completed as part of this study. The first and second synoptic sampling events included samples collected at the same 12 sampling sites. During the first and second synoptic sampling events, the lowest number of detections (2 and 0, respectively) and the lowest total concentrations of all measured compounds (0.62 and not measureable, respectively) occurred in samples collected at the Macdona site (Medina River near Macdona, Tex.). The highest number of detections (21 and 23, respectively) and highest total concentrations of all measured compounds (7.75 and 3.97 micrograms per liter [µg/L], respectively) occurred in samples collected at the SAR Elmendorf site (San Antonio River near Elmendorf, Tex.). The third synoptic sampling event included samples collected at seven sites that were added to the study after the first two synoptic sampling events were completed. During the third synoptic sampling event, the lowest number of detections (two) and the lowest total concentration (0.14 µg/L) of compounds were measured in samples collected at the North Prong site (North Prong Medina River above confluence Wallace Creek near Medina, Tex.). The highest number of detections (21) occurred at the SAR Mitchell site (San Antonio River at Mitchell Street, San Antonio, Tex.). The Dos Rios site (the Dos Rios wastewater treatment plant outfall at San Antonio, Tex.) had the highest total concentration of all measured compounds (4.37 µg/L) in the third synoptic sampling event. Because Ecleto Creek flows only intermittently at the Ecleto site (Ecleto Creek near Runge, Tex.), samples from the Ecleto site were collected at different times than were samples from the other sites and were not included in a synoptic sampling event. The presence of wastewater compounds at the Ecleto site indicates that at least some wastewater compounds can be introduced into surface waters in rural parts of the San Antonio River Basin during runoff or because of onsite wastewater system seepage. The steroidal hormone and sterols detected at the Ecleto site, including estrone, cholesterol, beta-sitosterol, and beta-stigmastanol, likely were derived from cattle waste rather than from wastewater effluent. The distributional patterns of detections and concentrations of individual compounds and compound classes show the influence of wastewater-treatment plant (WWTP) outfalls on the quality of water in the San Antonio River Basin. In the Medina River Subbasin, the minimal influence of

Opsahl, Stephen P.; Lambert, Rebecca B.

2013-01-01

292

On Boron Diffusion in MgF2  

NASA Astrophysics Data System (ADS)

The MgF2 monocrystals were irradiated at room temperature with 390 keV B+ ions up to the fluence of 1016cm?2. The irradiated samples were (isochronally and isothermally) annealed in high vacuum at the temperatures 200° C, 300° C, 400° C, 500° C, 600° C and 700° C for the times ranging from 2-100 hours. After each annealing step, the boron depth distribution was determined using the neutron depth profiling technique. As implanted, the depth distributions of boron exhibited standard Gaussian-like forms, but the evaluated profile parameters, RP = 960 nm and ? RP = 140 nm, were higher than those calculated using the SRIM code (RP = 870 nm and ?RP = 115 nm). Annealing at temperatures up to 400° C did not change the depth profiles. Annealing at 600° C, however, led to a one-way gradual transfer of the boron atoms from the site of implantation towards the sample surface, and in this way a bimodal profile was created. The amount of boron atoms, transferred to the sample surface, was an increasing function of the annealing time. After annealing at 700° C for 64 hours the bimodal profile collapsed into a single broad distribution, extending from the sample surface up to the implantation depth. The observed phenomena clearly points out the stability of the as-implanted boron depth profiles at lower annealing temperatures. Thermal annealing above 600° C, however, liberates boron atoms, which then predominantly migrate from the implantation site towards the sample surface, where they are captured on some unspecified surface defects.

Vacik, J.; Hnatowicz, V.; Cervena, J.; Posta, S.; Köster, U.; Pasold, G.

2009-03-01

293

Evaluation of hexagonal boron nitride as a new tablet lubricant.  

PubMed

In this study, hexagonal boron nitride (HBN) was evaluated as a new lubricant for pharmaceutical tablet manufacturing. The other conventional lubricants such as magnesium stearate (MGST), stearic acid (STAC), and glyceryl behenate (COMP) were also tested along with HBN. Tablets were manufactured on an instrumented single-station tablet press to monitor and quantify the lower punch ejection force (LPEF). The force ratio, tablet crushing strength, disintegration time, and thickness were measured. The lubricant film formation and lubricant distribution in tablets were studied using the scanning electron microscopy (SEM) and electron probe micro analyzer (EPMA). Based on the force ratio, a good lubrication was obtained at 1% for MGST and HBN; in contrast, STAC and COMP did not show a good lubrication. After 1%, all lubricants performed well. MGST was found to be the most effective lubricant based on LPEF-lubricant concentration profile. HBN provided a 50% decrease in LPEF at 2% lubricant concentration and was rated as an effective tablet lubricant. HBN was better than either STAC or COMP. Unlike MGST, HBN had no significant prolongation effect on tablet disintegration times. PMID:16176018

Turkoglu, Murat; Sahin, Inan; San, Tangul

2005-01-01

294

Rapid accurate isotopic measurements on boron in boric acid and boron carbide.  

PubMed

A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry. PMID:18964086

Duchateau, N L; Verbruggen, A; Hendrickx, F; De Bièvre, P

1986-04-01

295

Carrier doping into boron nanobelts by neutron transmutation  

SciTech Connect

We report the effects of a neutron-capture reaction of isotope {sup 10}B on the structure and electrical transport of {sup 10}B-enriched single-crystalline boron nanobelts. Partial amorphization, particularly at the surface of the nanobelt, was observed after thermal neutron irradiation with a dose of 2x10{sup 19} cm{sup -2}. Carrier doping into the nanobelts by neutron transmutation is expected after postannealing. The change in conductance is discussed based on the distribution of localized states in the band gap of {alpha}-tetragonal boron.

Kirihara, Kazuhiro; Shimizu, Yoshiki; Sasaki, Takeshi; Koshizaki, Naoto [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565 (Japan); Yamada, Yoichi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Esaka, Fumitaka [Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Yamamoto, Hiroyuki; Shamoto, Shin-ichi [Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Kimura, Kaoru [Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561 (Japan)

2010-11-22

296

Determination of boron and lithium by recording the products from (n, alpha) reactions  

NASA Technical Reports Server (NTRS)

Irradiation with thermal neutrons in the VVR-S reactor provides a nondestructive method for determining the presence of boron and lithium in solids. The charged particles produced in the reactions Li-6(n,alpha)H-3 and B-10(n,alpha)Li-7 were detected using CsI single crystal. For alpha-particle spectrometry in the boron determination, an ionization chamber (W and Sn electrodes, 99% Ar + 1% H2) was developed allowing both absolute and relative measurements. In determining boron in lithium-containing samples, both scintillation and ionization chambers are used. In determining lithium in minerals, the error was 1.5%, and the sensitivity 0.00005 wt.%. In the determination of boron in SiC with a concentration of boron approximately (3 plus or minus 2) the error given by the alpha-range uncertainty was 15%.

Lobanov, Y. M.; Zverev, B. P.; Simakhin, Y. F.; Usmanova, M. M.

1978-01-01

297

Comparative in vitro evaluation of dequalinium B, a new boron carrier for neutron capture therapy (NCT).  

PubMed

A boronated derivative of dequalinium, a delocalized lipophilic cation (DLC), was synthesized as a potential boron carrier for the selective targeting of mitochondria in malignant versus benign cells for boron neutron capture therapy (BNCT), a binary modality for the treatment of cancer. This agent, designated DEQ-B, was taken up and retained in vitro in the KB, F98, and C6 tumor cell lines but not in the normal epithelial cell line CV1. DEQ-B was also less toxic in the latter cell line at lower exposure concentrations The uptake, retention, and toxicity profiles of DEQ-B are comparable to those of the non-boronated DLCs, dequalinium, MKT 077, RH 123, and tetraphenylphosphonium chloride. Our results suggest that the synthesis and further evaluation of boronated DLCs as potential delivery agents for BNCT is warranted. PMID:11131639

Adams, D M; Ji, W; Barth, R F; Tjarks, W

298

Effect of initial salt concentrations on cell performance and distribution of internal resistance in microbial desalination cells.  

PubMed

Microbial desalination cells (MDCs) are modified microbial fuel cells (MFCs) that concurrently produce electricity and desalinate seawater, but adding a desalination compartment and an ion-exchange membrane may increase the internal resistance (Ri), which can limit the cell performance. However, the effects of a desalination chamber and initial NaCl concentrations on the internal resistances and the cell performances (i.e. Coulombic efficiency (CE), current and power density) of MDCs have yet to be thoroughly explored; thus, the cell performance and Ri distributions of MDCs having different initial concentrations and an MFC having no desalination chamber were compared. In the MDCs, the current and power density generation increased from 2.82?mA and 158.2?mW/m(2) to 3.17?mA and 204.5?mW/m(2) when the initial NaCl concentrations were increased from 5 to 30?g/L, as a consequence of the internal resistances decreasing from 2432.0 to 2328.4??. And even though the MFC has a lower Ri than the MDCs, lower cell performances (current: 2.59?mA; power density: 141.6?mW/m(2) and CE: 62.1%) were observed; there was no effect of improved junction potential in the MFC. Thus, in the MDCs, the higher internal resistances due to the addition of a desalination compartment can be offset by reducing the electrolyte resistance and improving the junction potential at higher NaCl concentrations. PMID:25212471

Yang, Euntae; Choi, Mi-Jin; Kim, Kyoung-Yeol; Chae, Kyu-Jung; Kim, In S

2015-04-01

299

Concentrations and distribution of synthetic musks and siloxanes in sewage sludge of wastewater treatment plants in China.  

PubMed

In this study, we assessed the occurrence and distribution patterns of seven synthetic musks (SMs) and 17 siloxanes in anaerobic digested sludge samples collected at the dewatering process from 42 wastewater treatment plants (WWTPs) in China. SMs in sludge from different WWTPs exhibited similar composition profiles, and their total concentrations ranged from 47.3 ng/g to 68.2 ?g/g dry weight (dw). On average, galaxolide (HHCB, 63.8%) and tonalide (AHTN, 31.7%) accounted for 95.5% of ?SMs. The total concentrations of cyclic siloxanes ranged from concentrations and detection frequencies of SMs and siloxanes in sewage sludge indicated that both of them were widely used in China. Among the sludge samples from 42 WWTPs, the concentrations of both ?SMs and ?siloxanes had considerable variations. We investigated the influence of potential factors (wastewater and sludge characteristics, the treatment capacity, serving population, and the treatment techniques of WWTPs) on the levels of target compounds in sludge, and found that SMs were significantly (p<0.05) correlated with the total organic carbon (TOC) of the sludge and the serving population of WWTP. There were also strong correlations (p<0.05) between the treatment capacity of WWTPs and cyclic siloxanes, as well as between the TOC of the sludge and linear siloxanes. In addition, the ecological risks of SMs and siloxanes in sewage sludge addressed to land application were assessed, which suggested that there was a low risk to the soil environment. PMID:24463026

Liu, Nannan; Shi, Yali; Li, Wenhui; Xu, Lin; Cai, Yaqi

2014-04-01

300

Spectrophotometric determination of traces of boron in high purity silicon  

SciTech Connect

A reddish brown complex is formed between boron and curcumin in concentrated sulfuric acid and glacial acetic acid mixture (1:1). The colored complex is highly selective and stable for about 3 hours and has the maximum absorbance at 545 nm. The sensitivity of the method is extremely high and the detection limit is 3 parts per billion based on 0.004 absorbance value. The interference of some of the important cations and anions relevant to silicon were studied and it is found that 100 fold excess of most of these cations and anions do not interfere in the determination of boron. The method is successfully employed for the determination of boron in silicon used in semiconductor devices. The results have been verified by standard addition method.

Parashar, D.C.; Sarkar, A.K.; Singh, N. (National Physical Lab., New Delhi (India))

1989-07-01

301

Microanalytical techniques for boron analysis using the 10B(n,alpha)7Li reaction.  

PubMed

In order to predict the efficacy of boronated compounds for neutron capture therapy (NCT), it is mandatory that the boron concentration in tissues be known. Various techniques for measurement of trace amounts of boron (1-100 ppm) are available, including chemical and physical procedures. Experience has shown that, with the polyhedral boranes and carboranes in particular, the usual colorimetric and spark emission spectroscopic methods are not reliable. Although these compounds may be traced with additional radiolabels, direct physical detection of boron by nondestructive methods is clearly preferable. Boron analysis via detection of the prompt-gamma ray from the 10B(n, alpha)7Li reaction has been shown to be a reliable technique. Two prompt-gamma facilities developed at Brookhaven National Laboratory are described. One, at the 60-MW high flux beam reactor, uses sophisticated beam extraction techniques to enhance thermal neutron intensity and reduce fast neutron and gamma contamination. The other was constructed at Brookhaven's 5-MW medical research reactor and uses conventional shielding and electronics to provide an "on-line" boron analysis facility adjacent to beams designed for NCT, thus satisfying one of the requisites for clinical application of this procedure. Technical restrictions attendant upon the synthesis and testing of boronated biomolecules often require the measurement of trace amounts of boron in extremely small (mg) samples. A track-etching technique capable of detecting ng amounts of boron in mg liquid or cell samples is described. Thus it is possible to measure the boron content in small amounts (mg samples) of antibodies, or boron uptake in cells grown in tissue culture. PMID:3951409

Fairchild, R G; Gabel, D; Laster, B H; Greenberg, D; Kiszenick, W; Micca, P L

1986-01-01

302

Comparison of elemental boron and boron halide implants into silicon  

NASA Astrophysics Data System (ADS)

This paper investigates the electrical activation of boron halide molecular implants into silicon and compares them to boron implants at the same effective energy. The implanted species: B +, BF2+, BCl2+ and BBr2+ were implanted to doses of 2 × 10 14 and 1 × 10 15 B cm -2 the energy of the molecular implants was calculated to give an effective boron implant energy of 5 keV. Samples cut from the wafers were annealed for 30 s at temperatures ranging from 800 °C to 1100 °C. Hall effect measurements were used to compare and contrast the electrical activation of the boron between the different halide species and doses. It was found that molecular implants of BBr2+ and BCl2+ do not enhance the electrical activation of boron to the same extent that BF2+ implants do. The BBr2+ implants are only comparable with boron after annealing at high temperatures (above 1000 °C). The BF2+ implants show enhanced electrical activation with respect to boron for all the annealing temperatures and doses studied. Rutherford backscattering spectroscopy (RBS) of silicon implanted with BBr2+ to a dose of 1 × 10 15 boron atoms cm -2, shows that an amorphous region is created during the implantation. This region fully re-grows after annealing at 1100 °C; lower temperature anneals remove only part of the amorphous layer. RBS channelling shows that a fraction of the bromine takes up substitutional lattice sites upon implantation, and that this fraction increases as the samples are annealed at temperatures above 600 °C with 40% of the B being in substitutional sites after annealing at 1050 °C.

Sharp, J. A.; Gwilliam, R. M.; Sealy, B. J.; Jeynes, C.; Hamilton, J. J.; Kirkby, K. J.

2005-08-01

303

Concentration and particle size distribution of particulate matter inside tunnel-ventilated high-rise layer operation houses  

NASA Astrophysics Data System (ADS)

Particulate matter (PM) is a criteria pollutant emitted from animal feeding operation (AFO) facilities, especially from poultry operation buildings. Fundamental data regarding AFO PM either do not exist, or are not representative of different animal production systems or housing types. This field study investigated particle size distributions (PSDs) and concentrations of total suspended particulate (TSP) in a tunnel ventilated high-rise layer house under different operational conditions. Six low-volume (1 m3 h-1) TSP samplers were used to collect PM samples on two floors of the high-rise layer houses across four seasons through day/night sampling protocols. The day/night sampling design was to examine animal activity impact. The PM samples were analyzed by a multi-wave length laser diffraction particle size analyzer (LS13 320) for PSDs characterized by mass median diameters (MMDs) and geometric standard deviations (GSDs). It was discovered that the mean TSP concentrations ranged from 1.0 ± 0.5 mg m-3 to 5.33 ± 0.36 mg m-3 (mean ± SD). TSP concentrations in winter were higher than in summer; concentrations on the 2nd floor were higher than that on the 1st floor; concentrations of daytime samples were higher than those of nighttime samples. Animal activity (represented by day/night samples) had the highest impact on TSP concentration as compared to other influential factors (spatial, seasonal, ventilation). No significant seasonal variations of MMD and GSD were observed in most of samples. Majority of day/night MMDs and GSDs demonstrated no significant differences. Thus the impact of animal activity (day vs. night) on MMD and GSD were not significant. Mean MMDs ± SDs ranged from 16.81 ± 1.57 ?m to 20.26 ± 3.53 ?m, whereas means ± SDs of GSDs ranged from 2.38 ± 0.20 to 2.81 ± 0.30. Mean PM2.5 fractions ± SDs ranged from 5.03 ± 1.60% to 8.93 ± 0.97%, whereas mean PM10 fractions ± SDs ranged from 23.25 ± 5.18% to 38.55 ± 2.96%. Significant seasonal variation in both PM10 and PM2.5 mass fractions were observed.

Wang-Li, Lingjuan; Cao, Zihan; Li, Qianfeng; Liu, Zifei; Beasley, David B.

2013-02-01

304

Residual stresses in boron/tungsten and boron/carbon fibers  

NASA Technical Reports Server (NTRS)

By measuring the change in fracture stress of 203 micrometer diameter fibers of boron on tungsten (B/W) as a function of fiber diameter as reduced by chemical etching, it is shown that the flaws which limit B/W fiber strength are located at the surface and in the tungsten boride core. After etching to a diameter of 188 micrometers m virtually all fiber fractures were caused by core flaws, the average strength being 4.50 GN/sq m. If both the surface and core flaws are removed, the fracture strength, limited by flaws in the boron itself, is approximately 6.89 GN/sq m. This was measured on B/W fibers which were split longitudinally and had their cores removed by chemical etching. The longitudinal residual stress distribution was determined for 102 micrometer diameter B/W and B/C fibers.

Behrendt, D. R.

1977-01-01

305

Personal exposures to VOC in the upper end of the distribution—relationships to indoor, outdoor and workplace concentrations  

NASA Astrophysics Data System (ADS)

Evaluation of relationships between median residential indoor, indoor workplace and population exposures may obscure potential strategies for exposure reduction. Evaluation of participants with personal exposures above median levels in the EXPOLIS study in Athens, Helsinki, Oxford and Prague illustrated that these participants frequently showed a different relationship to indoor and workplace levels than that shown by the population median. Thus, prioritization of environments for control measures based on median exposures may exclude important areas where effectively focused control measures are possible, and may therefore have little impact on the highest and most harmful exposures. Further, personal exposures at the upper end of the distribution may exceed the US EPA inhalation reference concentration (Rfc), illustrated here using hexane, naphthalene and benzene. For example upper 90th percentile personal exposures to benzene in Athens and Prague were 64 and 27 ?g m -3 with peak exposures of 217 and 38 ?g m -3, respectively for non-ETS exposed participants relative to an Rfc of 30 ?g m -3. Strategies to reduce exposures to individual compounds, therefore, may benefit from focus on the high end of the distribution to identify activities and behaviors that result in elevated exposures. Control strategies targeting activities that lead to exposures in the upper end of the distribution would reduce the variability associated with population median values by bringing the upper end of the exposure distribution closer to median values. Thus, compliance with health-based standards would be more protective of the higher exposed fraction of the population, in whom health effects would be more expected.

Edwards, Rufus D.; Schweizer, Christian; Jantunen, Matti; Lai, Hak Kan; Bayer-Oglesby, Lucy; Katsouyanni, Klea; Nieuwenhuijsen, Mark; Saarela, Kristiina; Sram, Radim; Künzli, Nino

306

A CLOSURE STUDY OF AEROSOL MASS CONCENTRATION MEASUREMENTS: COMPARISON OF VALUES OBTAINED WITH FILTERS AND BY DIRECT MEASUREMENTS OF MASS DISTRIBUTIONS. (R826372)  

EPA Science Inventory

We compare measurements of aerosol mass concentrations obtained gravimetrically using Teflon coated glass fiber filters and by integrating mass distributions measured with the differential mobility analyzer–aerosol particle mass analyzer (DMA–APM) technique (Aero...

307

Inhibitory effect of boron against Botrytis cinerea on table grapes and its possible mechanisms of action.  

PubMed

Boron, an essential plant micronutrient, was effective in the form of potassium tetraborate for control of postharvest gray mold caused by Botrytis cinerea on table grapes stored at room temperature or at 0 degrees C. The inhibition of fruit decay was closely correlated with boron concentrations and partially influenced by pH value of the solution. Boron strongly inhibited spore germination, germ tube elongation, and mycelial spread of B. cinerea in the culture medium. Application of boron at 1% caused the appearance of abnormal spores (disrupted) in some cases. By using propidium iodide fluorescent staining, loss of membrane integrity in B. cinerea was observed after boron treatment. Furthermore, boron led to the leakage of cellular constituents (soluble proteins and carbohydrates) from hyphae of B. cinerea. These data suggest that the mechanisms by which boron decreased gray mold decay of table grapes may be directly related to the disruption effect of boron on cell membrane of the fungal pathogen that resulted in the breakdown of the cell membrane and loss of cytoplasmic materials from the hyphae. PMID:20060611

Qin, Guozheng; Zong, Yuanyuan; Chen, Qiling; Hua, Donglai; Tian, Shiping

2010-03-31

308

Life cycle analysis of distributed concentrating solar combined heat and power: economics, global warming potential and water  

NASA Astrophysics Data System (ADS)

We report on life cycle assessment (LCA) of the economics, global warming potential and water (both for desalination and water use in operation) for a distributed concentrating solar combined heat and power (DCS-CHP) system. Detailed simulation of system performance across 1020 sites in the US combined with a sensible cost allocation scheme informs this LCA. We forecast a levelized cost of 0.25 kWh-1 electricity and 0.03 kWh-1 thermal, for a system with a life cycle global warming potential of ˜80 gCO2eq kWh-1 of electricity and ˜10 gCO2eq kWh-1 thermal, sited in Oakland, California. On the basis of the economics shown for air cooling, and the fact that any combined heat and power system reduces the need for cooling while at the same time boosting the overall solar efficiency of the system, DCS-CHP compares favorably to other electric power generation systems in terms of minimization of water use in the maintenance and operation of the plant. The outlook for water desalination coupled with distributed concentrating solar combined heat and power is less favorable. At a projected cost of 1.40 m-3, water desalination with DCS-CHP would be economical and practical only in areas where water is very scarce or moderately expensive, primarily available through the informal sector, and where contaminated or salt water is easily available as feed-water. It is also interesting to note that 0.40-1.90 m-3 is the range of water prices in the developed world, so DCS-CHP desalination systems could also be an economical solution there under some conditions.

Norwood, Zack; Kammen, Daniel

2012-12-01

309

Enhanced Thematic Mapper Plus Analyses of Chlorophyll-a Concentration and Distribution in Small Kettle Lakes, Southern Minnesota  

NASA Astrophysics Data System (ADS)

Spatial and temporal variability of lake water quality is well defined; however, due to costs and logistical constraints, multiple assessments of water quality are rarely obtained in Minnesota lakes. For improved resource management, an integrated assessment of whole-lake surface water quality is needed. Sequential spatial descriptions of water quality variability will facilitate characterizing physical, chemical, and biological processes in lakes and help to identify sources of external and internal nutrient loading within individual lakes. Our study focused on surface water properties in six small southern Minnesota meso-eutrophic, eutrophic, and hypereutrophic lakes. Our protocol included obtaining multiple, georeferenced in-lake and laboratory-based assays of surface water quality within 24 hours of each Enhanced Thematic Mapper Plus (ETM+) overpass during the summer of 2001. Lake water data (including chlorophyll-a, total phosphorus, water transparency, and total suspended solids) were regressed against temporally and spatially equivalent three-by-three pixel averages of singular and combined ETM+ spectral bands. A simple linear regression of chlorophyll-a analyses from water samples and corrected ETM+ Band 2 data provided the strongest correlation (R2 = 0.96) among the available data. The chlorophyll-a concentrations from processed ETM+ data in each lake exhibit up to three orders of magnitude greater variance than those derived from water sample data. Furthermore, ETM+ results illustrate distinctive patterns of chlorophyll-a distribution among lakes of similar trophic status that are not present in water sample data. Thus, it appears ETM+ data provide better characterizations of overall chlorophyll-a concentrations and distribution relative to multiple-sample in-lake water analyses in small kettle lakes.

Hoppie, B.; Roost, B.

2004-12-01

310

Neutron detectors comprising boron powder  

SciTech Connect

High-efficiency neutron detector substrate assemblies comprising a first conductive substrate, wherein a first side of the substrate is in direct contact with a first layer of a powder material comprising .sup.10boron, .sup.10boron carbide or combinations thereof, and wherein a conductive material is in proximity to the first layer of powder material; and processes of making said neutron detector substrate assemblies.

Wang, Zhehui; Morris, Christopher; Bacon, Jeffrey Darnell; Makela, Mark F; Spaulding, Randy Jay

2013-05-21

311

Carbothermic formation of boron nitride  

Microsoft Academic Search

Formation of boron nitride by reaction of boric oxide with carbon and nitrogen was studied. It was found from the results of experiments conducted by holding B2O3-activated C mixtures under a flowing nitrogen atmosphere that formation of boron nitride was complete in 120 min at 1500 °C. After cleaning the reaction product from the ash of the activated carbon and from

A. Aydo?du; N. Sevinç

2003-01-01

312

The effect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium  

NASA Astrophysics Data System (ADS)

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D( 3He,p) 4He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N 2 gas at 650°C. Deuterium loading was performed by exposure to 1 Torr of D 2 gas at 500°C. The deuterium distribution was influenced by nitrogen in the near-surface regions of all samples. Specifically, deuterium solubility was suppressed in surface regions of high (greater than 1%) nitrogen concentration. The deuterium solubility also remained low within the first few microns, well beyond the region of high nitrogen concentration. This effect is attributed to internal elastic stresses imposed by the non-deuterium absorbing nitrogen-rich layer on the Ti. These stresses prohibit the volume expansion associated with deuterium absorption. We estimate stresses on the order of 3-4 GPa are required to suppress the deuterium solubility to the values observed. The deuterium absorption kinetics were observed to depend systematically on the thickness of the nitrogen-rich layer. This is consistent with limited solubility near the surface or a surface poisoning effect influencing the overall deuterium diffusion from the gas phase into the Ti bulk.

Costescu, Corneliu I.; Heuser, Brent J.

2000-04-01

313

The spatial distribution pattern of heavy metal concentrations in urban soils — a study of anthropogenic effects in Berehove, Ukraine  

NASA Astrophysics Data System (ADS)

In the present study we examined the Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn contamination levels of the soils of Berehove, a small city in West-Ukraine. As a first step we determined the spatial distribution of the heavy metal contents of the urban soils; then, by studying the land use structure of the city and by statistical analysis we identified the major sources of contamination; we established a matrix of correlations between the heavy metal contents of the soils and the different types of land use; and finally, we drew a conclusion regarding the possible origin(s) of these heavy metals. By means of multivariate statistical analysis we established that of the investigated metals, Ba, Cd, Cu, Pb and Zn accumulated in the city's soils primarily as a result of anthropogenic activity. In the most polluted urban areas (i.e. in the industrial zones and along the roads and highways with heavy traffic), in the case of several metals (Ba, Cd, Cu, Pb, Zn) we measured concentration levels even two or three times higher than the threshold limit values. Furthermore, Cr, Fe and Ni are primarily of lithogenic origin; therefore, the soil concentrations of these heavy metals depend mainly on the chemical composition of the soil-forming rocks.

Vince, Tímea; Szabó, György; Csoma, Zoltán; Sándor, Gábor; Szabó, Szilárd

2014-09-01

314

A Nanometer Aerosol Size Analyzer (nASA) for Rapid Measurement of High-Concentration Size Distributions  

NASA Technical Reports Server (NTRS)

We have developed a fast-response Nanometer Aerosol Size Analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 seconds. The analyzer includes a bipolar charger (P0210), an extended-length Nanometer Differential Mobility Analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 second per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the Tandem Differential Mobility Analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented.

Han, Hee-Siew; Chen, Da-Ren; Pui, David Y. H.; Anderson, Bruce E.

2001-01-01

315

Initial boronization of PBX-M using ablation from solid boronized probes  

SciTech Connect

Boronization was performed by plasma ablation of two solid boronized target probes. Probe-1, in a mushroom shape, consisted of a 10.7% boronized two-dimensional carbon-carbon composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2, in a rectangular shape, consisted of an 86% boronized graphite felt composite containing 19.5 g of 40-[mu]m boron particles. Probe-1 boronization deposited [approximately]26 monolayers of boron. After boronization with Probe-1, the loop voltage in 1-MW neutral-beam-heated plasmas decreased 27%, and volt-second consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of [approximately]5. The central oxygen density decreased 15 to 20%. Carbon levels initially increased during boronization but were significantly reduced after boronization. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization deposited [approximately]70 monolayers. Probe-2 boronization exhibited similar improved plasma conditions, but for some parameters, a smaller percentage change occurred because of the previous boronization with Probe-1. The ablation rates of both probes were consistent with front-face temperatures above the boron melting point. The results demonstrate the performance of two different boronized probe materials and the relative simplicity and effectiveness of solid target boronization as a convenient, real-time impurity control technique. 20 refs., 10 figs., 1 tab.

Kugel, H.W.; Timberlake, J.; Bell, R.; Kaita, R.; Kaye, S.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; Von Goeler, S. (Princeton Univ., NJ (United States)) (and others)

1994-07-01

316

Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx  

SciTech Connect

During the VOCALS Regional Experiment, the DOE G-1 aircraft was used to sample a varying aerosol environment pertinent to properties of stratocumulus clouds over a longitude band extending 800 km west from the Chilean coast at Arica. Trace gas and aerosol measurements are presented as a function of longitude, altitude, and dew point in this study. Spatial distributions are consistent with an upper atmospheric source for O{sub 3} and South American coastal sources for marine boundary layer (MBL) CO and aerosol, most of which is acidic sulfate in agreement with the dominant pollution source being SO{sub 2} from Cu smelters and power plants. Pollutant layers in the free troposphere (FT) can be a result of emissions to the north in Peru or long range transport from the west. At a given altitude in the FT (up to 3 km), dew point varies by 40 C with dry air descending from the upper atmospheric and moist air having a BL contribution. Ascent of BL air to a cold high altitude results in the condensation and precipitation removal of all but a few percent of BL water along with aerosol that served as CCN. Thus, aerosol volume decreases with dew point in the FT. Aerosol size spectra have a bimodal structure in the MBL and an intermediate diameter unimodal distribution in the FT. Comparing cloud droplet number concentration (CDNC) and pre-cloud aerosol (Dp > 100 nm) gives a linear relation up to a number concentration of {approx}150 cm{sup -3}, followed by a less than proportional increase in CDNC at higher aerosol number concentration. A number balance between below cloud aerosol and cloud droplets indicates that {approx}25% of aerosol in the PCASP size range are interstitial (not activated). One hundred and two constant altitude cloud transects were identified and used to determine properties of interstitial aerosol. One transect is examined in detail as a case study. Approximately 25 to 50% of aerosol with D{sub p} > 110 nm were not activated, the difference between the two approaches possibly representing shattered cloud droplets or unknown artifact. CDNC and interstitial aerosol were anti-correlated in all cloud transects, consistent with the occurrence of dry in-cloud areas due to entrainment or circulation mixing.

Kleinman, L.I.; Daum, P. H.; Lee, Y.-N.; Lewis, E. R.; Sedlacek III, A. J.; Senum, G. I.; Springston, S. R.; Wang, J.; Hubbe, J.; Jayne, J.; Min, Q.; Yum, S. S.; Allen, G.

2011-06-21

317

Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx  

SciTech Connect

During the VOCALS Regional Experiment, the DOE G-1 aircraft was used to sample a varying aerosol environment pertinent to properties of stratocumulus clouds over a longitude band extending 800 km west from the Chilean coast at Arica. Trace gas and aerosol measurements are presented as a function of longitude, altitude, and dew point in this study. Spatial distributions are consistent with an upper atmospheric source for O{sub 3} and South American coastal sources for marine boundary layer (MBL) CO and aerosol, most of which is acidic sulfate. Pollutant layers in the free troposphere (FT) can be a result of emissions to the north in Peru or long range transport from the west. At a given altitude in the FT (up to 3 km), dew point varies by 40 C with dry air descending from the upper atmospheric and moist air having a boundary layer (BL) contribution. Ascent of BL air to a cold high altitude results in the condensation and precipitation removal of all but a few percent of BL water along with aerosol that served as CCN. Thus, aerosol volume decreases with dew point in the FT. Aerosol size spectra have a bimodal structure in the MBL and an intermediate diameter unimodal distribution in the FT. Comparing cloud droplet number concentration (CDNC) and pre-cloud aerosol (D{sub p} > 100 nm) gives a linear relation up to a number concentration of {approx}150 cm{sup -3}, followed by a less than proportional increase in CDNC at higher aerosol number concentration. A number balance between below cloud aerosol and cloud droplets indicates that {approx}25 % of aerosol with D{sub p} > 100 nm are interstitial (not activated). A direct comparison of pre-cloud and in-cloud aerosol yields a higher estimate. Artifacts in the measurement of interstitial aerosol due to droplet shatter and evaporation are discussed. Within each of 102 constant altitude cloud transects, CDNC and interstitial aerosol were anti-correlated. An examination of one cloud as a case study shows that the interstitial aerosol appears to have a background, upon which is superimposed a high frequency signal that contains the anti-correlation. The anti-correlation is a possible source of information on particle activation or evaporation.

Kleinman L. I.; Daum, P. H.; Lee, Y.-N.; Lewis, E. R.; Sedlacek III, A. J.; Senum, G. I.; Springston, S. R.; Wang, J.; Hubbe, J.; Jayne, J.; Min, Q.; Yum, S. S.; Allen, G.

2012-01-04

318

On the probability distribution of the concentration of two aqueous species undergoing a bimolecular reaction in heterogeneous formations  

NASA Astrophysics Data System (ADS)

Sound understanding of chemical transformations in fully saturated formations is needed in order to conduct realistic simulations of biodegradation processes, transport of radionuclide, and chemical transformations induced by the injection of reactants in the subsurface, just to mention a few examples in which chemical reactions other than sorption are relevant. In a large number of cases of interest chemical transformation depends on the mixing between two waters with different geochemical characteristics, as for example in engineered remediation of contaminated sites, or dissolution/precipitation processes occurring naturally in karst formations. A relatively large body of literature has been dedicated to this subject, mostly considering the case of bimolecular dissolution-precipitation equilibrium reaction, because of its simplicity. Since the early work of Kapoor, Gelhar and Miralles-Wilhelm (1997), it was clear that the chemical transformation depends critically to the extent to which the two waters actually mix in the subsurface. On the other hand, mixing depends chiefly on the non-linear interplay between pore-scale (local) dispersion and heterogeneous advection. In this contribution we study how pore-scale dispersion and advection influence the bimolecular reaction resulting from the injection of water in a heterogeneous formation with two aqueous species which concentrations are different from those of the ambient water. The reaction is considered fast with respect to the transport time scale such that it can be considered at equilibrium. We first study the time evolution of the plume moments of the two aqueous species. Then, we study the evolution of the concentration pdf of the two aqueous species, in order to better describe the chemical transformation and explore how pore-scale dispersion and advection influences the dynamics of the two aqueous species. We observe that the pdf of the concentration of the two species show a transition from a bimodal distribution at the early times to a unimodal Gaussian-like distribution at times which are larger at smaller pore-scale dispersion. Overall, pore-scale dispersion is more effective in inducing mixing for highly than for weakly heterogeneous formations, and for small than large injection volumes.

Bellin, A.; Fiori, A.; Severino, G.

2009-12-01

319

Prompt gamma-ray activation analysis for determination of boron in aqueous solutions  

NASA Astrophysics Data System (ADS)

Prompt gamma-ray activation analysis (PGAA) is a nuclear analytical technique for the determination of trace and other elements in solid, liquid or gaseous samples. The method consists in observing gamma rays emitted by a sample during neutron irradiation. Of particular importance for PGAA is the measurement of boron. Indeed, this technique gives the opportunity to detect boron concentration down to the ppm or ppb level depending on the sample matrix. Furthermore, boron cannot be easily measured by other methods without risks of contamination. Trace analysis of boron in liquids has been performed and characterized at the PGA facility of the neutron spallation source SINQ (Paul Scherrer Institute, Switzerland). First, a calibration curve was determined with standard boron solutions. Then, the PGAA was applied for the determination of boron in geological water samples. The results were compared with ICP-MS measurements. Finally, the method yielded promising results to measure the concentration of boron taken up by cells in a new treatment for rheumatoid arthritis.

Baechler, S.; Kudejova, P.; Jolie, J.; Schenker, J.-L.; Stritt, N.

2002-08-01

320

Determination of boron contents in water samples collected from the Neelum valley, Azad Kashmir, Pakistan.  

PubMed

Intake of boron from food and drinking water may pose a risk to the public health above a certain concentration level. Therefore, knowledge of boron concentration in drinking water and food items is essential. In this context, samples of drinking water were collected from natural springs of the Neelum valley, Azad Kashmir, hit by devastating earthquake in 2005. In these samples, boron concentration was determined using neutron-induced radiography technique. To do so, unknown water samples, along with standard of known boron dried on CR-39 detectors, were irradiated with thermal neutrons. After exposure, CR-39 detectors were etched in 6 M NaOH at 70°C. The tracks produced due to the alpha particles and (7)Li ions as a result of (10)B(n,?)(7)Li reaction were counted under an optical microscope. The tracks produced in theses samples were then related to the boron contents. The measured boron concentration in water samples was found to vary from 0.105?±?0.005 to 0.247?±?0.013 mg/l with an average value of 0.17?±?0.04 mg/l, which are within the acceptable limits. PMID:20306233

Akram, Muhammad; Matiullah; Iqbal, Arshid; Husaini, S N; Malik, Fariha

2011-03-01

321

Boron11 MRI and MRS of intact animals infused with a boron neutron capture agent  

Microsoft Academic Search

Boron neutron capture therapy (BNCT) depends on the delivery of boron-containing drugs to a targeted lesion. Currently, the verification and quantification of in vivo boron content is a difficult problem. Boron-11 spectroscopy was utilized to confirm the presence of a dimeric sulfhydryl dodecaborane BNCT agent contained in an intact animal. Spectroscopy experiments revealed that the decay time of transverse magnetization

George W. Kabalka; Mark Davis; Peter Bendel

1988-01-01

322

Coprecipitation and isotopic fractionation of boron in modern biogenic carbonates  

SciTech Connect

The abundances and isotopic composition of boron in modern, biogenic calcareous skeletons from the Gulf of Elat, Israel, the Great Barrier Reef, Australia, and in deep-sea sediments have been examined by negative thermal-ionization mass spectrometry. The selected species (Foraminifera, Pteropoda, corals, Gastropoda, and Pelecypoda) yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals. The variations of {delta}{sup 11}B may be controlled by isotopic exchange of boron species in which {sup 10}B is preferentially partitioned into the tetrahedral species, and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates. The B content and {delta}{sup 11}B values of deep-sea sediments, Foraminifera tests, and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition. As a result of enrichment of B in corals, a substantially higher biogenic sink of 6.4 {plus minus} 0.9 {times} 10{sup 10} g/yr is calculated for carbonates. This is only slightly lower than the sink for desorbable B in marine sediments (10 {times} 10{sup 10} g/yr) and approximately half that of altered oceanic crust (14 {times} 10{sup 10} g/yr). Thus, carbonates are an important sink for B in the oceans being {approximately}20% of the total sinks. The preferential incorporation of {sup 10}B into calcium carbonate results in oceanic {sup 11}B-enrichment, estimated as 1.2 {plus minus} 0.3 {times} 10{sup 12} per mil {center dot} g/yr. The boron-isotope composition of authigenic, well-preserved carbonate skeletons may provide a useful tool to record secular boron-isotope variations in seawater at various times in the geological record.

Vengosh, A. (Australian National Univ., Canberra (Australia) Hebrew Univ., Jerusalem (Israel)); Chivas, A.R.; McCulloch, M.T. (Australian National Univ., Canberra (Australia)); Kolodny, Y.; Starinsky, A. (Hebrew Univ., Jerusalem (Israel))

1991-10-01

323

Boron in Presolar Silicon Carbide Grains from Supernovae  

NASA Astrophysics Data System (ADS)

Eleven presolar silicon carbide grains of type X separated from the Murchison meteorite have been analyzed for boron abundances and isotopic compositions by secondary ion mass spectrometry. Boron concentrations are low with typical B/Si ratios of ~1×10-5. The average 11B/10B ratio of 3.46+/-1.39 is compatible with the solar system value but might be affected by contaminating boron of laboratory origin. These data are compared with theoretical predictions for Type II supernovae, the most likely parent stars of X grains. The B/Si ratios of X grains are much lower (more than an order of magnitude on average) than expected from Type II supernova shell-mixing of matter from the C- and Si-rich zones, contrary to other elemental ratios such as Al/Si and Ti/Si. Condensation calculations show that with C/O>1 in the ejecta, boron and aluminum will readily condense as BN and AlN, respectively, into silicon carbide, and the B/Al ratio is expected to remain constant. The nitrogen, aluminum, and titanium abundances in SiC X grains are well reproduced by the condensation calculations. Given the similarity of the boron and aluminum condensation chemistry and the generally expected high B/Al ratios (relative to solar) in Type II supernova mixtures with C/O>1, the observed difference between measured and predicted B/Al ratios must be considered a serious problem. Possible solutions include (1) lower than predicted boron production from Type II supernovae, (2) complex mixing scenarios in supernova ejecta involving only sublayers of the C-rich zones, and (3) formation of silicon carbide under conditions with C/O<0.1.

Hoppe, P.; Lodders, K.; Strebel, R.; Amari, S.; Lewis, R. S.

2001-04-01

324

The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces  

NASA Astrophysics Data System (ADS)

Boron oxide has been added to commercial silicate glasses for many years to aid in lowering melting temperatures, lowering thermal expansion, and controlling chemical durability. The fact that simple borate glasses have rather high thermal expansion and low chemical durability attests to the unique influence of boron oxide additions upon the properties of silicate glasses. However, the impact of boron oxide additions upon surface properties of multicomponent borosilicates such as adsorption and reactivity is not yet well understood. In particular, the presence of multiple coordination states for boron is expected to introduce adsorption sites with different acidic or basic behavior, but their existence is yet unproven. To investigate these effects, multicomponent sodium aluminosilicate glasses have been prepared with varying sodium and boron concentrations and drawn into moderately high-surface-area continuous filament fibers. A relatively new technique, boron K-edge Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is applied to study the local boron coordination at fracture and melt-derived fiber surfaces of these glasses. This structural information is combined with surface compositional information by X-ray Photoelectron Spectroscopy (XPS) to characterize the local atomic structure of boron at the as-formed glass surface. Finally, this information is used to interpret the adsorptivity of these as-formed and leached surfaces toward short-chain alcohol molecules through a new Inverse Gas Chromatography---Temperature Programmed Desorption (IGC-TPD) experiment. The results clearly show that boron additions to alkali-free glass surfaces introduce a unique adsorption site which is not present on boron-free glass surfaces and is easily removed by leaching in acidic solutions.

Schaut, Robert A.

325

Boronated porhyrins and methods for their use  

DOEpatents

The present invention covers boronated porphyrins containing multiple carborane cages which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies such as boron neutron capture therapy and photodynamic therapy. 3 figs.

Miura, M.; Shelnutt, J.A.; Slatkin, D.N.

1999-03-02

326

Synthesis and photocurrent of amorphous boron nanowires.  

PubMed

Although theoretically feasible, synthesis of boron nanostructures is challenging due to the highly reactive nature, high melting and boiling points of boron. We have developed a thermal vapor transfer approach to synthesizing amorphous boron nanowire using a solid boron source. The amorphous nature and chemical composition of boron nanowires were characterized by high resolution transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. Optical properties and photoconduction of boron nanowires have not yet been reported. In our investigation, the amorphous boron nanowire showed much better optical and electrical properties than previously reported photo-response of crystalline boron nanobelts. When excited by a blue LED, the photo/dark current ratio (I/I?) is 1.5 and time constants in the order of tens of seconds. I/I? is 1.17 using a green light. PMID:25061013

Ge, Liehui; Lei, Sidong; Hart, Amelia H C; Gao, Guanhui; Jafry, Huma; Vajtai, Robert; Ajayan, Pulickel M

2014-08-22

327

Volatilization of methyl borate in iron matrix. Determination of boron in steel by ICP atomic emission spectrometry.  

PubMed

A rapid and reliable method for the determination of boron by ICP-AES in steels is described. The procedure is based on a discontinuous generation of methyl borate, in concentrated sulphuric acid and phosphoric acid medium, after injecting 45 microl of methanol in 20 microl of sample. The gaseous methyl borate and excess methanol are fed into the ICP torch via the intermediate tube by a flow of 430 ml/min Ar carrier gas, without disturbing the discharge. This work simplifies drastically the existing methodology of boron analysis in steels. Acid-soluble boron has been determined, but acid-insoluble boron can also be determined. The determination is carried out without iron interferences, with a reproducibility of 1.90% r.s.d. for a concentration of 20 microg/ml, and an absolute detection limit of 20 ng of total boron, working with a solution volume of 20 microl. PMID:18965797

Lopez Molinero, A; Ferrer, A; Castillo, J R

1993-09-01

328

Temporal variability of the bioaerosol background at a subway station: concentration level, size distribution, and diversity of airborne bacteria.  

PubMed

Naturally occurring bioaerosol environments may present a challenge to biological detection-identification-monitoring (BIODIM) systems aiming at rapid and reliable warning of bioterrorism incidents. One way to improve the operational performance of BIODIM systems is to increase our understanding of relevant bioaerosol backgrounds. Subway stations are enclosed public environments which may be regarded as potential bioterrorism targets. This study provides novel information concerning the temporal variability of the concentration level, size distribution, and diversity of airborne bacteria in a Norwegian subway station. Three different air samplers were used during a 72-h sampling campaign in February 2011. The results suggested that the airborne bacterial environment was stable between days and seasons, while the intraday variability was found to be substantial, although often following a consistent diurnal pattern. The bacterial levels ranged from not detected to 10(3) CFU m(-3) and generally showed increased levels during the daytime compared to the nighttime levels, as well as during rush hours compared to non-rush hours. The airborne bacterial levels showed rapid temporal variation (up to 270-fold) on some occasions, both consistent and inconsistent with the diurnal profile. Airborne bacterium-containing particles were distributed between different sizes for particles of >1.1 ?m, although ?50% were between 1.1 and 3.3 ?m. Anthropogenic activities (mainly passengers) were demonstrated as major sources of airborne bacteria and predominantly contributed 1.1- to 3.3-?m bacterium-containing particles. Our findings contribute to the development of realistic testing and evaluation schemes for BIODIM equipment by providing information that may be used to simulate operational bioaerosol backgrounds during controlled aerosol chamber-based challenge tests with biological threat agents. PMID:24162566

Dybwad, Marius; Skogan, Gunnar; Blatny, Janet Martha

2014-01-01

329

Distributions and determinants of mercury concentrations in toenails among American young adults: the CARDIA Trace Element Study.  

PubMed

Since data on mercury (Hg) levels in Caucasians and African Americans (AAs) of both genders are lacking, this study aims to present toenail Hg distributions and explore the potential determinants using data from the Coronary Artery Risk Development in Young Adults Trace Element Study. Data from 4,344 Americans, aged 20-32 in 1987, recruited from Oakland, Chicago, Minneapolis, and Birmingham were used to measure toenail Hg levels by instrumental neutron-activation method. The Hg distribution was described with selected percentiles and geometric means. Multivariable linear regression (MLR) was used to examine potential determinants of Hg levels within ethnicity-gender subgroups. The geometric mean of toenail Hg was 0.212 (95 % CI?=?0.207-0.218)??g/g. Hg levels varied geographically with Oakland the highest [0.381 (0.367-0.395) ?g/g] and Minneapolis the lowest [0.140 (0.134-0.147) ?g/g]. MLR analyses showed that male gender and AA ethnicity were negatively associated with toenail Hg levels, and that age, living in Oakland city, education level, alcohol consumption, and total fish intake were positively associated with toenail Hg concentrations within each ethnicity-gender subgroup. Current smokers were found to have higher Hg only in AA men. This study suggested age, gender, ethnicity, study center, alcohol, education level, and fish consumption consistently predict toenail Hg levels. As fish consumption was the key determinant, avoiding certain types of fish that have relatively high Hg levels may be crucial in reducing Hg intake. PMID:22926255

Xun, Pengcheng; Liu, Kiang; Morris, J Steve; Jordan, Joanne M; He, Ka

2013-03-01

330

Mineral resource of the month: boron  

USGS Publications Warehouse

What does boron have to do with baseball, apple pie, motherhood and Chevrolet? Boron minerals and chemicals are used in the tanning of leather baseballs and gloves; in micro-fertilizer to grow apples and in the glass and enamels of bakewares to cook apple pie; in boron detergents for soaking baby clothes and diapers; and in fiberglass parts for the Chevrolet Corvette.

Lyday, Phyllis A.

2005-01-01

331

Communications CVD Growth of Boron Nitride Nanotubes  

E-print Network

Communications CVD Growth of Boron Nitride Nanotubes Oleg R. Lourie, Carolyn R. Jones, Bart M to their all-carbon analogues, boron nitride nanotubes are predicted to exhibit electronic properties that are insensitive to tube diameter and chirality.9 Boron nitride nanotubes are known to have a wide band gap of 5 e

332

Influence of trans-boundary biomass burning impacted air masses on submicron particle number concentrations and size distributions  

NASA Astrophysics Data System (ADS)

Submicron particle number concentration (PNC) and particle size distribution (PSD) in the size range of 5.6-560 nm were investigated in Singapore from 27 June 2009 through 6 September 2009. Slightly hazy conditions lasted in Singapore from 6 to 10 August. Backward air trajectories indicated that the haze was due to the transport of biomass burning impacted air masses originating from wild forest and peat fires in Sumatra, Indonesia. Three distinct peaks in the morning (08:00-10:00), afternoon (13:00-15:00) and evening (16:00-20:00) were observed on a typical normal day. However, during the haze period no distinct morning and afternoon peaks were observed and the PNC (39,775 ± 3741 cm-3) increased by 1.5 times when compared to that during non-haze periods (26,462 ± 6017). The morning and afternoon peaks on the normal day were associated with the local rush hour traffic while the afternoon peak was induced by new particle formation (NPF). Diurnal profiles of PNCs and PSDs showed that primary particle peak diameters were large during the haze (60 nm) period when compared to that during the non-haze period (45.3 nm). NPF events observed in the afternoon period on normal days were suppressed during the haze periods due to heavy particle loading in atmosphere caused by biomass burning impacted air masses.

Betha, Raghu; Zhang, Zhe; Balasubramanian, Rajasekhar

2014-08-01

333

Explorations of mechanisms regulating ectomycorrhizal colonization of boron-fertilized pine  

SciTech Connect

The present study examined the effects of foliar boron fertilization and inoculation with an ectomycorrhizal fungus (Pisolithus tinctorius) on {sup 14}C-photosynthate partitioning to various tissues of shortleaf pine seedlings, placing special emphasis on the {sup 14}C distribution to the root systems. Specifically, the hypotheses tested are: (a) {sup 14}C allocation to the root systems will increase with inoculation, and (b) {sup 14}C partitioning will be enhanced by foliar boron application. 13 refs., 3 tabs.

Garrett, H.E.; Begonia, G.; Sword, M.A.

1989-01-01

334

Effect of pressure on the Raman spectra of synthetic diamonds with boron impurity  

SciTech Connect

The raman scattering technique is used for studying diamonds with a 0.04-0.1 at % boron impurity under a pressure up to 3 GPa in a chamber with sapphire anvils. The Raman frequency increases linearly with pressure for all samples with pressure coefficients of 2.947 cm{sup -1}/GPa for pure diamond and 3.01 cm{sup -1}/GPa for boron-doped samples. The Raman linewidths remain unchanged for pure diamond and for diamond with a boron concentration of about 0.04 at % and decrease linearly upon an increase in pressure for samples with a boron concentration of about 0.1 at %. The Raman spectra with a line profile corresponding to the Fano resonance do not change qualitatively up to a pressure of 3 GPa. In diamond samples with a boron impurity exceeding 0.1 at %, the boron concentration in the surface layer can be substantially higher than at the center of the sample.

Utyuzh, A. N., E-mail: anatu@ns.hppi.troitsk.ru; Timofeev, Yu. A.; Rakhmanina, A. V. [Russian Academy of Sciences, Vereshchagin Institute of High Pressures (Russian Federation)

2007-04-15

335

Experimental and theoretical study of concentration distributions in a model pore electrode; Measurement of two-dimensional concentration gradients in a zinc model pore  

SciTech Connect

The optical probe beam deflection technique has been employed to study two-dimensional concentration gradients within the electrolyte of a zinc model pore. This paper reports that the model pore cell constructed for this study retains the small, confined geometry and two-dimensional character of an actual pore within a porous zinc electrode. Refractive index gradients in the direction of the model pore axis showed that the concentration of zincate ion reaches a maximum between the model pore mouth and a position one-fourth of the distance toward the pore root during the anodic oxidation of the zinc electrode. Also, the variation in the refractive index gradient normal to the electrode along the length of the zinc anode allowed the authors to calculate the local current density within the model pore.

Weaver, J.K.; McLarnon, F.R.; Cairns, E.J. (Applied Science Div., Lawrence Berkeley Lab. and Dept. of Chemical Engineering, Berkeley, CA (US))

1991-09-01

336

Synergistic methods for the production of high-strength and low-cost boron carbide  

NASA Astrophysics Data System (ADS)

Boron carbide (B4C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B4C make it a nearly ideal material for personnel and vehicular armor. B4C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B4C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B4C powders. The boron carbide powder examined in this study was a sub-micron (0.6 mum median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form of phenolic resin, and titanium additives in the form of 32 nm and 0.9 mum TiO2 powders were selected. Parametric studies of sintering behavior were performed via high-temperature dilatometry in order to measure the in-situ sample contraction and thereby measure the influence of the additives and their amounts on the overall densification rate. Additionally, broad composition and sintering/post-HIPing studies followed by characterization and mechanical testing elucidated the effects of these additives on sample densification, microstructure de- velopment, and mechanical properties such as Vickers hardness and microindentation fracture toughness. Based upon this research, a process has been developed for the sintering of boron carbide that yielded end products with high relative densities (i.e., 100%, or theoretical density), microstructures with a fine (˜2-3 mum) grain size, and high Vickers microindentation hardness values. In addition to possessing these improved physical properties, the costs of producing this material were substantially lower (by a factor of 5 or more) than recently patented work on the pressureless sintering and post-HIPing of phase-pure boron carbide powder. This recently patented work developed out of our laboratory utilized an optimized powder distribution and yielded samples with high relative densities and high hardness values. The current work employed the use of titanium and carbon additives in specific ratios to activate the sintering of boron carbide powder possessing an approximately mono-modal particle size distribution. Upon heating to high temperatures, these additives produced fine-scale TiB2 and graphite inclusions that served to hinder grain growth and substantially improve overall sintered and post-HIPed densities when added in sufficient concentrations. The fine boron carbide grain size manifested as a result of these second phase inclusions caused a substantial increase in hardness; the highest hardness specimen yielded a hardness value (2884.5 kg/mm2) approaching that of phase-pure and theoretically-dense boron carbide (2939 kg/mm2). Additionally, the same high-hardness composition exhibited a noticeably higher fracture toughness (3.04 MPa

Wiley, Charles Schenck

2011-12-01

337

Subporphyrinato Boron(III) Hydrides.  

PubMed

Subporphyrinato boron(III) hydrides were prepared by reduction of subporphyrinato boron(III) methoxides with diisobutylaluminum hydride (DIBAL-H) in good yields. The authenticity of the B-H bond has been unambiguously confirmed by a (1)H NMR signal that appears as a broad quartet at -2.27 ppm with a large coupling constant with the central (11)B, characteristic B-H infrared stretching frequencies, and single crystal X-ray diffraction analysis. Red shifts in the corresponding absorption and fluorescence profiles are accounted for in terms of the electron-donating nature of the B-hydride. The hydridic character of subporphyrinato boron(III) hydrides has been demonstrated by the production of H2 via reaction with water or HCl, and controlled reductions of aromatic aldehydes and imines in the presence of a catalytic amount of Ph3C[B(C6F5)4]. PMID:25563966

Tsurumaki, Eiji; Sung, Jooyoung; Kim, Dongho; Osuka, Atsuhiro

2015-01-28

338

Risk factors of methane hydrate resource development in the concentrated zones distributed in the eastern Nankai Trough  

NASA Astrophysics Data System (ADS)

Some environmental and safety concerns on the offshore methane hydrate development have been raised, but the ground of such allegations are sometime not fully reasonable. The risks of methane hydrate resource development to environment and safety should be discussed upon methane hydrate occurrences condition, the production methods, and the designs of production system, under comprehensively scientific manners. In the Phase 1 of the Methane Hydrate Exploitation Program in Japan (FY2001-2008), the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) found methane hydrate concentrated zones in the eastern Nankai Trough that are potential prospects for resource development. The concentrated zones are consisted of turbidite-derived sandy sediments and hydrate crystals in pore spaces of sand grains (pore-filling type structure). The MH21 Research Consortium proposed the depressurization method as prime technique due to its efficiency of gas production in such concentrated zones, and has tried to develop conceptual designs of production systems based on the information of existing devices and facilities. Under the condition and circumstances described above, the authors tried to extract and evaluate some risk factors concerning methane hydrate development using depressurization in the area. Leakage of methane gas, that is less harmful substance to ecosystem than heavier hydrocarbons, from production system can be one possible risk. However, in the case of gas production through wellbore, even if catastrophic damages happen in the subsea production system during gas production, the leakages do not continue because the borehole could be filled by seawater and depressurization is stopped immediately. Another possible risk is a leakage of produced gas through seafloor. If methane hydrate production makes high pressure or temperature zones in sediments, the risk should be considered. However, depressurization method makes opposite condition, low pressure. Deformation and subsidence of the sea floor may be unavoidable but does not cause serious concern on the safety. Some have argued that hydrate dissociations in wide area may cause landslide due to weakened formation by dissociation. To manage the concern, the test site should be chosen carefully and formation property alternation should be well known. One common misunderstanding widespread in public is that methane hydrate is "unstable material." Indeed, the hydrate is stable in the original temperature and pressure conditions, and the endothermic process of hydrate dissociation leads negative feedback to the formation conditions from the altered states by artificial depressurization. Also the hydrate dissociation in the sandy sediments is governed by relatively slow heat and fluid transport phenomena in porous media, so the process is gradual. Therefore, a catastrophic chain reaction which many people imagine is surely unlikely. As mentioned above, at present, risks of methane hydrate resource development in the concentrated zones distributed in the eastern Nankai trough are not significant, and comparable or less serious than conventional oil and gas production, we concluded. Of course, this evaluation should be verified with offshore production tests in the future, and new knowledge should be reflected to the safe and environmentally friendly production system designs. The nature of unconsolidated formation after the hydrate dissociation is key issue of such investigation. MH21 consortium has studied the issue in many aspects, and will continue the investigation.

Yamamoto, K.; Nagakubo, S.

2009-04-01

339

Distributions  

NSDL National Science Digital Library

This online, interactive lesson on distributions provides examples, exercises, and applets which explore the basic types of probability distributions and the ways distributions can be defined using density functions, distribution functions, and quantile functions.

Siegrist, Kyle

340

Thermal conductivity of boron carbides  

NASA Technical Reports Server (NTRS)

Knowledge of the thermal conductivity of boron carbide is necessary to evaluate its potential for high-temperature thermoelectric energy conversion applications. Measurements have been conducted of the thermal diffusivity of hot-pressed boron carbide BxC samples as a function of composition (x in the range from 4 to 9), temperature (300-1700 K), and temperature cycling. These data, in concert with density and specific-heat data, yield the thermal conductivities of these materials. The results are discussed in terms of a structural model that has been previously advanced to explain the electronic transport data. Some novel mechanisms for thermal conduction are briefly discussed.

Wood, C.; Emin, D.; Gray, P. E.

1985-01-01

341

Metronidazole and Hydroxymetronidazole Central Nervous System Distribution: 1. Microdialysis Assessment of Brain Extracellular Fluid Concentrations in Patients with Acute Brain Injury  

PubMed Central

The distribution of metronidazole in the central nervous system has only been described based on cerebrospinal fluid data. However, extracellular fluid (ECF) concentrations may better predict its antimicrobial effect and/or side effects. We sought to explore by microdialysis brain ECF metronidazole distribution in patients with acute brain injury. Four brain-injured patients monitored by cerebral microdialysis received 500 mg of metronidazole over 0.5 h every 8 h. Brain dialysates and blood samples were collected at steady state over 8 h. Probe recoveries were evaluated by in vivo retrodialysis in each patient for metronidazole. Metronidazole and OH-metronidazole were assayed by high-pressure liquid chromatography, and a noncompartmental pharmacokinetic analysis was performed. Probe recovery was equal to 78.8% ± 1.3% for metronidazole in patients. Unbound brain metronidazole concentration-time curves were delayed compared to unbound plasma concentration-time curves but with a mean metronidazole unbound brain/plasma AUC0–? ratio equal to 102% ± 19% (ranging from 87 to 124%). The unbound plasma concentration-time profiles for OH-metronidazole were flat, with mean average steady-state concentrations equal to 4.0 ± 0.7 ?g ml?1. This microdialysis study describes the steady-state brain distribution of metronidazole in patients and confirms its extensive distribution. PMID:24277041

Frasca, Denis; Dahyot-Fizelier, Claire; Adier, Christophe; Mimoz, Olivier; Debaene, Bertrand; Couet, William

2014-01-01

342

Biodistribution of sodium borocaptate (BSH) for boron neutron capture therapy (BNCT) in an oral cancer model.  

PubMed

Boron neutron capture therapy (BNCT) is based on selective accumulation of ¹?B carriers in tumor followed by neutron irradiation. We previously proved the therapeutic success of BNCT mediated by the boron compounds boronophenylalanine and sodium decahydrodecaborate (GB-10) in the hamster cheek pouch oral cancer model. Based on the clinical relevance of the boron carrier sodium borocaptate (BSH) and the knowledge that the most effective way to optimize BNCT is to improve tumor boron targeting, the specific aim of this study was to perform biodistribution studies of BSH in the hamster cheek pouch oral cancer model and evaluate the feasibility of BNCT mediated by BSH at nuclear reactor RA-3. The general aim of these studies is to contribute to the knowledge of BNCT radiobiology and optimize BNCT for head and neck cancer. Sodium borocaptate (50 mg ¹?B/kg) was administered to tumor-bearing hamsters. Groups of 3-5 animals were killed humanely at nine time-points, 3-12 h post-administration. Samples of blood, tumor, precancerous pouch tissue, normal pouch tissue and other clinically relevant normal tissues were processed for boron measurement by optic emission spectroscopy. Tumor boron concentration peaked to therapeutically useful boron concentration values of 24-35 ppm. The boron concentration ratio tumor/normal pouch tissue ranged from 1.1 to 1.8. Pharmacokinetic curves showed that the optimum interval between BSH administration and neutron irradiation was 7-11 h. It is concluded that BNCT mediated by BSH at nuclear reactor RA-3 would be feasible. PMID:23591915

Garabalino, Marcela A; Heber, Elisa M; Monti Hughes, Andrea; González, Sara J; Molinari, Ana J; Pozzi, Emiliano C C; Nievas, Susana; Itoiz, Maria E; Aromando, Romina F; Nigg, David W; Bauer, William; Trivillin, Verónica A; Schwint, Amanda E

2013-08-01

343

Commercial Clinical Application of Boron Neutron Capture Therapy  

SciTech Connect

CRADA No. 95-CR-09 among the LITCO--now Bechtel BWXT Idaho, LLC; a private company, Neutron Therapies Limited Liability Company, NTL formerly Ionix Corporation; and Washington State University was established in 1996 to further the development of BNCT. NTL has established a laboratory for the synthesis, under US FDA approved current Good Manufacturing Practices (cGMP) guidelines, of key boron intermediates and final boron agents for BNCT. The company has focused initially on the development of the compound GB-10 (Na{sub 2}B{sub 10}H{sub 10}) as the first boron agent of interest. An Investigational New Drug (IND) application for GB-10 has been filed and approved by the FDA for a Phase I human biodistribution trial in patients with non-small cell lung cancer and glioblastoma multiforme at UW under the direction of Professor Keith Stelzer, Principal Investigator (PI). These trials are funded by NTL under a contract with the UW, Department of Radiation Oncology, and the initial phases are nearing completion. Initial results show that boron-10 concentrations on the order of 100 micrograms per gram (100 ppm) can be achieved and maintained in blood with no indication of toxicity.

N /A

1999-09-03

344

Interactions between dietary boron and thiamine affect lipid metabolism  

SciTech Connect

An experiment was designed to test the hypothesis that dietary boron impacts upon the function of various coenzymes involved in energy metabolism. In a 2 {times} 7 factorially-arranged experiment, weanling, vitamin D{sub 3}-deprived rats were fed a ground corn-casein-corn oil based diet supplemented with 0 or 2 mg boron/kg and 50% of the requirement for thiamine (TM), riboflavin (RF), pantothenic acid (PA) or pyridoxine (PX); 0% for folic acid (FA) or nicotinic acid (NA). All vitamins were supplemented in adequate amounts in the control diet. At 8 weeks of age, the TM dietary treatment was the one most affected by supplemental dietary boron (SDB). In rats that were fed 50% TM, SDB increased plasma concentrations of triglyceride (TG) and activity of alanine transaminase (ALT), and the liver to body weight (L/B) ratio. However, in the SDB animals, adequate amounts of TM decreased the means of those variables to near that observed in non-SDB rats fed 50% TM. The findings suggest that an interaction between dietary boron and TM affects lipid metabolism.

Herbel, J.L.; Hunt, C.D. (Dept. of Agriculture, Grand Forks, ND (United States))

1991-03-15

345

DOES SALINITY REDUCE BORON’S TOXIC EFFECT IN BROCCOLI?  

Technology Transfer Automated Retrieval System (TEKTRAN)

High salinity and boron often occur together in irrigation water in arid climates, but very little research has been done to study the interaction of the two. A greenhouse experiment was conducted at the U.S. Salinity Laboratory in sand tanks to evaluate the interactions between B and saline draina...

346

Controls on methane concentration and stable isotope (?2HCH4 and ?13C-CH4) distributions in the water columns of the Black Sea and Cariaco Basin  

Microsoft Academic Search

Methane (CH4) concentration and stable isotope (?2H-CH4 and ?13C-CH4) depth distributions show large differences in the water columns of the Earth's largest CH4-containing anoxic basins, the Black Sea and Cariaco Basin. In the deep basins, the between-basin stable isotope differences are large, 83‰ for ?2H-CH4 and 9‰ for ?13C-CH4, and the distributions are mirror images of one another. The major

J. D. Kessler; W. S. Reeburgh; S. C. Tyler

2006-01-01

347

Boron-Containing Compounds for Liposome-Mediated Tumor Localization and Application to Neutron Capture Therapy  

SciTech Connect

Medical application of boron neutron capture therapy (BNCT) has been significantly hindered by the slow development of boron drug-targeting methodologies for the selective delivery of high boron concentration sto malignant cells. We have successfully sought to fill this need by creating liposomes suitable as in vivo boron delivery vehicles for BNCT. Delivery of therapeutic quantities of boron to tumors in murine models has been achieved with small unilamellar boron-rich liposomes. Subsequently, attempts have been made to improve delivery efficiency of liposomes encapsulating boron-containing water-soluble species into their hollow core by incorporating lipophilic boron compounds as addenda to the liposome bilayer, incorporating boron compounds as structural components of the bilayer (which however, poses the risk of sacrificing some stability), and combinations thereof. Regardless of the method, approximately 90% of the total liposome mass remains therapeutically inactive and comprised of the vehicle?s construction materials, while less than 5% is boron for neutron targeting. Following this laboratory's intensive study, the observed tumor specificity of certain liposomes has been attributed to their diminutive size of these liposomes (30-150 nm), which enables these small vesicles to pass through the porous, immature vasculature of rapidly growing tumor tissue. We surmised that any amphiphilic nanoparticle of suitable size could possess some tumor selectivity. Consequently, the discovery of a very boron-rich nanoparticle delivery agent with biodistribution performance similar to unilamellar liposomes became one of our goals. Closomers, a new class of polyhedral borane derivatives, attracted us as an alternative BNCT drug-delivery system. We specifically envisioned dodeca (nido-carboranyl)-substituted closomers as possibly having a great potential role in BNCT drug delivery. They could function as extraordinarily boron-rich BNCT drugs since they are amphiphilic unimolecular nanoparticles presenting several advantages: tunable size through functionalization and branching, spherical shape due to the icosahedral B122? core, promising water solubility resulting from degradation of all pendant closo-carborane groups to their hydrophilic nido anion substituents, and efficient boron delivery owing to the presence of 120 boron atoms which gives rise to a boron content as high as 40% by weight. Keeping the new objective in mind, we have focused on the design, synthesis and evaluation of new and very boron-rich closomer species. Additionally, progress has also been made toward the evaluation of a newly synthesized boron-rich lipid as a substitute for DSPC in bilayer construction, and the boron content of the resulting liposomes has been greatly enhanced. Related research involving the synthesis and self-assembly of carborane-containing amphiphiles has been systematically studied. Combined hydrophobic and hydrophilic properties of the single-chain amphiphiles allow their spontaneous self-assembly to form rods under a variety of variable conditions, such as concentration in the bilayer, carborane cage structure, chain-length, counterion identity, solvents, methods of preparation, and the ionic charge. On the other hand, the number of attached chains affects the self-assembly process. Particles having totally different shapes have been observed for dual-chain amphiphiles.

Professor M. Frederick Hawthorne

2005-04-07

348

Chemical composition, molecular weight distribution, secondary structure and effect of NaCl on functional properties of walnut (Juglans regia L) protein isolates and concentrates.  

PubMed

Chemical composition, molecular weight distribution, secondary structure and effect of sodium chloride concentration on functional properties of walnut protein isolates, concentrates and defatted walnut flour were study. Compared with walnut protein concentrates (75.6%) and defatted walnut flour (52.5%), walnut protein isolates contain a relatively high amount of protein (90.5%). The yield of walnut protein isolates and concentrates was 43.2% and 76.6%, respectively. In molecular weight distribution study, Walnut protein isolates showed one peak with molecular weight of 106.33 KDa (100%) and walnut protein concentrates showed four peaks with molecular weight of 16,725 KDa (0.8%),104.943 KDa(63.9%), 7.3 KDa (11.4%), 2.6 KDa (23.9%). The secondary structure of walnut protein isolates was similar to that of walnut protein concentrates, but was differ from that of defatted walnut flour. The addition of sodium chloride (0?~?1 M) could improve the functionality of walnut protein concentrates, isolates and defatted walnut flour. The maximum solubility, water absorption capacity, emulsifying properties and foaming properties of walnut protein isolates, concentrates and defatted walnut flour were at sodium chloride solutions of 1.0 M, 0.6 M, 0.4 M, 0.6 M, respectively. The solubility of walnut protein concentrates (32.5%) in distilled water with 0 M sodium chloride was lower than that of walnut protein isolates (35.2%). The maximum solubility of walnut protein isolates, concentrates and defatted walnut flour in solution were 36.8%, 33.7% and 9.6% at 1.0 M sodium chloride solutions, respectively. As compared with other vegetable proteins, walnut protein isolates and concentrates exhibited better emulsifying properties and foam stability. PMID:25114337

Mao, Xiao-Ying; Hua, Yu-Fei

2014-08-01

349

Maps showing distribution of thorium in heavy-mineral concentrates, Richfield 1 degree by 2 degrees Quadrangle, Utah  

USGS Publications Warehouse

These maps are part of a folio of maps of the Richfield 1° x 2 ° quadrangle, Utah, prepared under the Conterminuous United States Mineral Assessment Program. Other publications in this folio are listed in the selected references. Located in west-central Utah, the Richfield quadrangle covers the eastern part of the Plioche-Marysvale igneous and mineral belt, which extends from the vicinity of Plioche in southeastern Nevada east-northeastward for 250 km (155 mi) into central Utah. The western two-thirds of the Richfield quadrangle is in the Basin and Range province and the eastern third is in the High Plateaus of Utah, a subprovince of the Colorado Plateau. Bedrock in the northern part of the Richfield quadrangle consists predominantly of latest Precambrian and Paleozoic sedimentary strata that were thrust eastward during the Sevier orogeny in Cretaceous time onto an autochthon of Mesozoic sedimentary rocks in the eastern part of the quadrangle. The southern part of the quadrangle is largely underlain by Oligocene and younger volcanic rocks and related intrusions. Extensional tectonism in late Cenozoic time broke the bedrock terrane into a series of north-trending fault blocks; the uplifted mountain areas were deeply eroded and the resulting debris deposited in the adjacent basins. Most of the mineral deposits in the Pioche-Marysvale mineral belt were formed during igneous activity in middle and late Cenozoic time. The regional sampling program was designed to define broad geochemical patterns and trends which can be utilized along with geologic and geophysical data to assess the mineral resource potential for this quadrangle. These maps of the Richfield 1° x 2° quadrangle show the regional distributions of copper in two fractions of heavy-mineral concentrates of drainage sediments.

Miller, William R.; Motooka, Jerry M.; McHugh, John B.

1985-01-01

350

Maps showing distribution of tungsten in heavy-mineral concentrates, Richfield 1 degree by 2 degrees Quadrangle, Utah  

USGS Publications Warehouse

These maps are part of a folio of maps of the Richfield 1° x 2 ° quadrangle, Utah, prepared under the Conterminuous United States Mineral Assessment Program. Other publications in this folio are listed in the selected references. Located in west-central Utah, the Richfield quadrangle covers the eastern part of the Plioche-Marysvale igneous and mineral belt, which extends from the vicinity of Plioche in southeastern Nevada east-northeastward for 250 km (155 mi) into central Utah. The western two-thirds of the Richfield quadrangle is in the Basin and Range province and the eastern third is in the High Plateaus of Utah, a subprovince of the Colorado Plateau. Bedrock in the northern part of the Richfield quadrangle consists predominantly of latest Precambrian and Paleozoic sedimentary strata that were thrust eastward during the Sevier orogeny in Cretaceous time onto an autochthon of Mesozoic sedimentary rocks in the eastern part of the quadrangle. The southern part of the quadrangle is largely underlain by Oligocene and younger volcanic rocks and related intrusions. Extensional tectonism in late Cenozoic time broke the bedrock terrane into a series of north-trending fault blocks; the uplifted mountain areas were deeply eroded and the resulting debris deposited in the adjacent basins. Most of the mineral deposits in the Pioche-Marysvale mineral belt were formed during igneous activity in middle and late Cenozoic time. The regional sampling program was designed to define broad geochemical patterns and trends which can be utilized along with geologic and geophysical data to assess the mineral resource potential for this quadrangle. These maps of the Richfield 1° x 2° quadrangle show the regional distributions of copper in two fractions of heavy-mineral concentrates of drainage sediments.

Miller, William R.; Motooka, Jerry M.; McHugh, John B.

1985-01-01

351

Boron supplementation and activated factor VII in healthy men  

Microsoft Academic Search

Objective: The aim of the present study was to determine whether postprandial concentrations of the active component of serine protease coagulation factor VII (VIIa) were lowered by acute boron supplementation in vivo.Design: An acute, randomized, placebo-controlled, double blind, cross-over study.Setting: Free-living population.Subjects: Fifteen apparently healthy men, aged 45–65 y.Interventions: Subjects visited the centre on two occasions, with the study days

JMW Wallace; MPA Hannon-Fletcher; PJ Robson; WS Gilmore; SA Hubbard; JJ Strain

2002-01-01

352

Boron as a tracer of aerosol from combustion of coal  

Microsoft Academic Search

Atmospheric boron was found to be predominantly gaseous in ambient samples and in stacks of coal-fired power plants. In the stacks, B\\/SOâ ratios were lower than expected from bulk US coals, consistent with volatilisation of 20-80% of the B during combustion. Mid-western ambient B\\/SOâ ratios were at or above stack values, with the lowest ratios associated with highest concentrations. SOâ

Thomas R. Fogg; Kenneth A. Rahn

1984-01-01

353

Method of separating boron isotopes  

DOEpatents

A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)-dichloroborane as the feed material. The photolysis can readily by achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

Jensen, R.J.; Thorne, J.M.; Cluff, C.L.

1981-01-23

354

Method of separating boron isotopes  

DOEpatents

A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO.sub.2 laser radiation and using fluences significantly below those required to dissociate BCl.sub.3.

Jensen, Reed J. (Los Alamos, NM); Thorne, James M. (Provo, UT); Cluff, Coran L. (Provo, UT); Hayes, John K. (Salt Lake City, UT)

1984-01-01

355

Structure of boron nitride nanotubes  

NASA Astrophysics Data System (ADS)

The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

Buranova, Yu. S.; Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

2015-01-01

356

Research in boron neutron capture synovectomy  

NASA Astrophysics Data System (ADS)

Boron Neutron Capture Synovectomy (BNCS) is a novel application of the 10B(n, (alpha) )7Li reaction for the treatment of Rheumatoid Arthritis. This potential treatment modality is in its developmental stages; in this paper results of research in two aspects of BNCS are presented. First, quantification of 10B-uptake in samples of human arthritic tissue by Prompt Gamma Neutron Activation Analysis is presented. 10B concentrations from 1625 to 2726 ppm are readily achieved. Second, ideal neutron beam studies have been undertaken and indicate that neutrons from thermal energies to 1 keV are useful for BNCS. This information is of use in designing practical therapy beams should this treatment modality be realized.

Binello, E.; Shortkroff, S.; Jones, A.; Viveiros, C.; Ly, A.; Sledge, C. B.; Davison, A.; Shefer, Ruth E.; Yanch, Jacquelyn C.

1997-02-01

357

Transport properties of polycrystalline boron doped diamond  

NASA Astrophysics Data System (ADS)

The influence of doping level in the electronic conductivity and resistivity properties of synthetic diamond films grown by hot filament chemical vapor deposition (HFCVD) was investigated. Eight different doping level concentrations varied from 500 to 30,000 ppm were considered. The polycrystalline morphology observed by scanning electron microscopy and Raman spectra was strongly affected by the addition of boron. The electric characterization by Hall effect as a function of temperature and magnetic field showed that at sufficiently low temperatures, electrical conduction is dominated by variable range hopping (VRH) conducting process. The resistivity was also investigated by temperature-dependent transport measurements in order to investigate the conduction mechanism in the doped samples. The samples exhibited the VRH (m = 1/4) mechanism in the temperature range from 77 to 300 K. The interface between metal, and our HFCVD diamond was also investigated for the lower doped samples.

de Oliveira, J. R.; Berengue, O. M.; Moro, J.; Ferreira, N. G.; Chiquito, A. J.; Baldan, M. R.

2014-08-01

358

Drinking water health advisory for boron  

SciTech Connect

The Health Advisory Program, sponsored by the Environmental Protection Agency's Office of Water, has issued its report on the element boron: included are the compounds boric acid and borax(sodium tetraborate). It provides information on the health effects, analytical methodology, and treatment technology that would be useful in dealing with the contamination of drinking water. Health Advisories (HAs) describe nonregulatory concentrations of drinking water contaminants at which adverse health effects would not be anticipated to occur over specific exposure durations. HAs serve as informal technical guidance to assist Federal, State, and local officials responsible for protecting public health when emergency spills or contamination situations occur. They are not legally enforceable Federal Standards and are subject to change as new information becomes available.

Cantilli, R.

1991-04-01

359

Enhancement of electrical conductivity and electrochemical activity of hydrogenated amorphous carbon by incorporating boron atoms  

NASA Astrophysics Data System (ADS)

Conductive boron-doped hydrogenated amorphous carbon (B-DLC) thin films were successfully synthesized with RF plasma-enhanced CVD method. By incorporating boron atoms in amorphous carbon, conduction types were changed from n- to p-type, and volume resistivity was decreased from 30.4 (non-doped) to 6.36 × 10-2 ? cm (B/C = 2.500 atom%). B-DLC film with sp2/(sp2 + sp3) carbons of 75 atom% exhibited high resistance to electrochemically-induced corrosion in strong acid solution. Furthermore, it was clarified that boron atoms in DLC could enhance kinetics of hydrogen evolution during water electrolysis at B-DLC surface. B-DLC is, therefore, a promising electrode material for hydrogen production by increasing the concentration of boron atoms in B-DLC and enhancing the reactivity of H2 evolution.

Naragino, Hiroshi; Yoshinaga, Kohsuke; Nakahara, Akira; Tanaka, Sakuya; Honda, Kensuke

2013-06-01

360

28-Homobrassinolide mitigates boron induced toxicity through enhanced antioxidant system in Vigna radiata plants.  

PubMed

The objective of this study was to establish relationship between boron induced oxidative stress and antioxidant system in Vigna radiata plants and also to investigate whether brassinosteroids will enhance the level of antioxidant system that could confer tolerance to the plants from the boron induced oxidative stress. The mung bean (V. radiata cv. T-44) plants were administered with 0.50, 1.0 and 2.0 mM boron at 6 d stage for 7 d along with nutrient solution. At 13 d stage, the seedlings were sprayed with deionized water (control) or 10(-8) M of 28-homobrassinolide and plants were harvested at 21 d stage to assess growth, leaf gas-exchange traits and biochemical parameters. The boron treatments diminished growth, water relations and photosynthetic attributes along with nitrate reductase and carbonic anhydrase activity in the concentration dependent manner whereas, it enhanced lipid peroxidation, electrolyte leakage, accumulation of H(2)O(2) as well as proline, and various antioxidant enzymes in the leaves of mung bean which were more pronounced at higher concentrations of boron. However, the follow-up application of 28-homobrassinolide to the boron stressed plants improved growth, water relations and photosynthesis and further enhanced the various antioxidant enzymes viz. catalase, peroxidase and superoxide dismutase and content of proline. The elevated level of antioxidant enzymes as well as proline could have conferred tolerance to the B-stressed plants resulting in improved growth, water relations and photosynthetic attributes. PMID:21899875

Yusuf, Mohammad; Fariduddin, Qazi; Ahmad, Aqil

2011-11-01

361

Spectromicroscopy of boron in human glioblastomas following administration of Na2B12H11SH  

NASA Astrophysics Data System (ADS)

Boron neutron capture therapy (BNCT) is an experimental, binary treatment for brain cancer which requires as the first step that tumor tissue is targeted with a boron-10 containing compound. Subsequent exposure to a thermal neutron flux results in destructive, short range nuclear reaction within 10 ?m of the boron compound. The success of the therapy requires than the BNCT agents be well localized in tumor, rather than healthy tissue. The MEPHISTO spectromicroscope, which performs microchemical analysis by x-ray absorption near edge structure (XANES) spectroscopy from microscopic areas, has been used to study the distribution of trace quantities of boron in human brain cancer tissues surgically removed from patients first administered with the compound Na2B12H11SH (BSH). The interpretation of XANES spectra is complicated by interference from physiologically present sulfur and phosphorus, which contribute structure in the same energy range as boron. We addressed this problem with the present extensive set of spectra from S, B, and P in relevant compounds. We demonstrate that a linear combination of sulfate, phosphate and BSH XANES can be used to reproduce the spectra acquired on boron-treated human brain tumor tissues. We analyzed human glioblastoma tissue from two patients administered and one not administered with BSH. As well as weak signals attributed to BSH, x-ray absorption spectra acquired from tissue samples detected boron in a reduced chemical state with respect to boron in BSH. This chemical state was characterized by a sharp absorption peak at 188.3 eV. Complementary studies on BSH reference samples were not able to reproduce this chemical state of boron, indicating that it is not an artifact produced during sample preparation or x-ray exposure. These data demonstrate that the chemical state of BSH may be altered by in vivo metabolism.

Gilbert, B.; Perfetti, L.; Fauchoux, O.; Redondo, J.; Baudat, P.-A.; Andres, R.; Neumann, M.; Steen, S.; Gabel, D.; Mercanti, Delio; Ciotti, M. Teresa; Perfetti, P.; Margaritondo, G.; de Stasio, Gelsomina

2000-07-01

362

40 CFR Table F-4 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution  

Code of Federal Regulations, 2010 CFR

40 ? Protection of Environment ? 5 ? 2010-07-01 ? 2010-07-01 ? false ? Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution ? F ? Table F-4 to Subpart F of Part 53 ? Protection of Environment ? ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ? AIR...

2010-07-01

363

Chemical contaminants in harbor porpoise ( Phocoena phocoena) from the North Atlantic coast: Tissue concentrations and intra- and inter-organ distribution  

Microsoft Academic Search

Concentrations of chlorinated hydrocarbons (CHs), such as polychlorinated biphenyls (PCBs), were measured in subsamples taken from different anatomical locations of blubber and liver of three apparently healthy harbor porpoises (Phocoena phocoena) incidentally caught in a gill-net fishery along the northwest Atlantic coast; selected elements (e.g., mercury) were measured in subsamples of liver. The vertical distribution (skin to muscle) of contaminants

Karen L. Tilbury; John E. Stein; James P. Meador; Cheryl A. Krone; Sin-Lam Chan

1997-01-01

364

40 CFR Table F-4 to Subpart F of... - Estimated Mass Concentration Measurement of PM 2.5 for Idealized Coarse Aerosol Size Distribution  

Code of Federal Regulations, 2014 CFR

...Idealized Coarse Aerosol Size Distribution F Table F-4 to Subpart F of Part 53 Protection of Environment ENVIRONMENTAL...Equivalent Methods for PM 2.5 Pt. 53, Subpt. F, Table F-4 Table F-4 to Subpart F of Part 53—Estimated Mass Concentration...

2014-07-01

365

40 CFR Table F-4 to Subpart F of... - Estimated Mass Concentration Measurement of PM 2.5 for Idealized Coarse Aerosol Size Distribution  

Code of Federal Regulations, 2013 CFR

...Idealized Coarse Aerosol Size Distribution F Table F-4 to Subpart F of Part 53 Protection of Environment ENVIRONMENTAL...Equivalent Methods for PM 2.5 Pt. 53, Subpt. F, Table F-4 Table F-4 to Subpart F of Part 53—Estimated Mass Concentration...

2013-07-01

366

Concentrations, viability, and distribution of Cryptosporidium genotypes in lagoons of swine facilities in Southern Piedmont and Coastal Plain watersheds of Georgia  

Technology Transfer Automated Retrieval System (TEKTRAN)

Waste lagoons of swine operations are a source of Cryptosporidium oocysts. Few studies, however, have reported on oocyst concentrations in swine waste lagoons; none have reported on oocyst viability status; nor has there been a systematic assessment of species/genotype distribution across different ...

367

Concentrating Information  

E-print Network

We introduce the concentrated information of tripartite quantum states. For three parties Alice, Bob and Charlie, it is defined as the maximal mutual information achievable between Alice and Charlie via local operations and classical communication performed by Charlie and Bob. The gap between classical and quantum concentrated information is shown to be an operational figure of merit for a state merging protocol involving shared mixed states and no distributed entanglement. We derive upper and lower bounds on the concentrated information, and obtain a closed expression for arbitrary pure tripartite states in the asymptotic setting. In this situation, one-way classical communication is shown to be sufficient for optimal information concentration.

Alexander Streltsov; Soojoon Lee; Gerardo Adesso

2014-10-23

368

Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718  

NASA Astrophysics Data System (ADS)

Susceptibility to heat-affected zone (HAZ) cracking during electron-beam welding was studied in two INCONEL 718-based alloys doped with different levels of boron. By lowering the carbon, sulfur, and phosphorous concentrations to be “as low as possible,” the occurrence of HAZ cracking was related directly to the level of segregation of boron at grain boundaries, which occurred by nonequilibrium segregation during a preweld heat treatment. The study has demonstrated a direct correlation between the amount of boron segregated at grain boundaries and their susceptibility to HAZ cracking, in terms of the total crack length and number of cracks observed in the HAZ. The analysis of results suggests that both the melting and resolidification temperatures of the boron-segregated grain boundaries can be about 100 °C to 200 °C lower than those of the grain boundaries that were susceptible to constitutional liquation of Nb carbides on them, making boron more deleterious in causing HAZ cracking.

Chen, W.; Chaturvedi, M. C.; Richards, N. L.

2001-04-01

369

Boron neutron capture therapy of ocular melanoma and intracranial glioma using p-boronophenylalanine  

SciTech Connect

During conventional radiotherapy, the dose that can be delivered to the tumor is limited by the tolerance of the surrounding normal tissue within the treatment volume. Boron Neutron Capture Therapy (BNCT) represents a promising modality for selective tumor irradiation. The key to effective BNCT is selective localization of {sup 10}B in the tumor. We have shown that the synthetic amino acid p-boronophenylalanine (BPA) will selectively deliver boron to melanomas and other tumors such as gliosarcomas and mammary carcinomas. Systemically delivered BPA may have general utility as a boron delivery agent for BNCT. In this paper, BNCT with BPA is used in treatment of experimentally induced gliosarcoma in rats and nonpigmented melanoma in rabbits. The tissue distribution of boron is described, as is response to the BNCT. 6 refs., 4 figs., 1 tab.

Coderre, J.A.; Greenberg, D.; Micca, P.L.; Joel, D.D.; Saraf, S. (Brookhaven National Lab., Upton, NY (USA)); Packer, S. (North Shore Univ. Hospital, Manhasset, NY (USA). Div. of Ophthalmology)

1990-01-01

370

Effect of boron and hydrogen on the electronic structure of Ni{sub 3}Al  

SciTech Connect

Using first-principles electronic structure calculations based on the Linear-Muffin-Tin Orbital (LMTO) method, we have investigated the effects of interstitial born and hydrogen on the electronic structure of the Ll{sub 2} ordered intermetallic Ni{sub 3}Al. When it occupies an octahedral interstitial site entirely coordinated by six Ni atoms, we find that boron enhances the charge distribution found in the strongly-bound ``pure`` Ni{sub 3}Al crystal: Charge is depleted at Ni and Al region. Substitution Al atoms for two of the Ni atoms coordinating the boron, however, reduces the interstitial charge density between atomic planes. In contrast to boron, hydrogen appears to deplete the interstitial charge, even when fully coordinated by Ni atoms. We suggest that these results are broadly consistent with the notion of boron as a cohesion enhancer and hydrogen as an embrittler.

Kioussi, N.; Watanabe, H.; Hemker, R.G. [California State Univ., Northridge, CA (United States). Dept. of Physics; Gourdin, W.: Gonis, A.; Johnson, P.E. [Lawrence Livermore National Lab., CA (United States)

1993-11-19

371

Elastic properties, sp3 fraction, and Raman scattering in low and high pressure synthesized diamond-like boron rich carbides  

NASA Astrophysics Data System (ADS)

Dense BCx phases with high boron concentration are predicted to be metastable, superhard, and conductors or superconductors depending on boron concentration. However, up to this point, diamond-like boron rich carbides BCx (dl-BCx) phases have been thought obtainable only through high pressure and high temperature treatment, necessitating small specimen volume. Here, we use electron energy loss spectroscopy combined with transmission electron microscopy, Raman spectroscopy, surface Brillouin scattering, laser ultrasonics (LU) technique, and analysis of elastic properties to demonstrate that low pressure synthesis (chemical vapor deposition) of BCx phases may also lead to the creation of diamond-like boron rich carbides. The elastic properties of the dl-BCx phases depend on the carbon sp2 versus sp3 content, which decreases with increasing boron concentration, while the boron bonds determine the shape of the Raman spectra of the dl-BCx after high pressure-high temperature treatment. Using the estimation of the density value based on the sp3 fraction, the shear modulus ? of dl-BC4, containing 10% carbon atoms with sp3 bonds, and dl-B3C2, containing 38% carbon atoms with sp3 bonds, were found to be ? = 19.3 GPa and ? = 170 GPa, respectively. The presented experimental data also imply that boron atoms lead to a creation of sp3 bonds during the deposition processes.

Zinin, Pavel V.; Liu, Yongsheng; Burgess, Katherine; Ciston, Jim; Jia, Ruth; Hong, Shiming; Sharma, Shiv; Ming, Li-Chung

2014-10-01

372

Concentration and distribution characteristic of main toxic metals in suspended particle material in Nanjing reach, Changjiang River  

Microsoft Academic Search

Six stations in the lower reach region of Changjiang River within Baguazhou Island, Nanjing reach were chosen to investigate\\u000a the toxic metals pollution characteristic in suspended particle material (SPM). SPM concentration, as well as reflectance\\u000a spectroscopy characteristic, toxic metal concentrations, and lead isotopes of suspended particle material were studied. SPM\\u000a concentrations were obtained from fluvial cross-sectional sampling near the surface

Li Hua; Hongrui Ma; Junfeng Ji

2011-01-01

373

Mass distribution and concentrations of negative chemiions in the exhaust of a jet engine: Sulfuric acid concentrations and observation of particle growth  

NASA Astrophysics Data System (ADS)

Measurements of negative-ion composition and density have been made in the exhaust of a J85-GE-5H turbojet, at ground level, as part of the NASA-EXCAVATE campaign. The mass spectrometer was placed 3 m from the exhaust plane of the engine. Measurements were done as a function of engine power in six steps from idle (50%) to military power (100%). Since the exhaust velocity changes with power, this also corresponds to a time evolution for ion growth. At 100% power most of the ions are HSO 4- with minor amounts of HSO 4-(H 2O) n. With decreasing engine power the degree of hydration increases. In addition, ions with a 139-amu core dominate the spectra at lower engine power. The chemical identity of this ion is unknown. Observation of a small amount of NO 3- core ions in the high-power spectra allows the determination of H 2SO 4 concentrations, which turn out to be a fraction-of-a-percent of the total sulfur in the fuel. Combining the present data with several previous composition measurements allows one to observe ion evolution from bare ions to ions with masses >8000 amu. Ion densities are derived and appear consistent with previous measurements used in modeling studies indicating that ion nucleation is a probable mechanism for volatile aerosol formation.

Miller, Thomas M.; Ballenthin, John O.; Viggiano, A. A.; Anderson, Bruce E.; Wey, Chowen C.

374

First principle investigations on Boron doped Fe2VAl Heusler alloy  

NASA Astrophysics Data System (ADS)

The role of atomic size of sp-element is investigated through theoretical calculations and basic experiments to understand the physical properties of Boron doped Fe2VAl alloy. The results of ab-initio calculations on ordered L21 structure of Fe2VAl1-xBx (x=0, 0.5, 1) alloys have been compared to understand the role of sp-element size on the hybridization among their respective valance states. Interestingly, semi-metallic and paramagnetic like ground states were found in the Boron doped alloys in similar to Fe2VAl, eliminating the role of size of the doppent sp-atom. These calculations result in hybridization where the covalent distribution of valance states among the atoms is responsible to produce a finite pseudo-gap at the Fermi level. The observed features could be explained on the basis of covalent theory of magnetism in which an amount of spectral weight transfer occurs in the DOS spectrum among the same spin orbitals, leading to symmetric distribution of bonding and anti-bonding states. However, the obtained experimental findings on Boron doped alloys are in contrast with these calculations, indicating that experimentally the alloy formation into an ideal L21 lattice does not happen while doping with Boron. Further, the micro structural analysis shows Boron segregation across the grain boundaries that may form magnetic inhomogeneities in the lattice of Boron doped Fe2VAl alloys which preferably cause these experimental anomalies.

Venkatesh, Ch.; Srivastava, S. K.; Rao, V. V.

2014-09-01

375

The biochemical effects of physiologic amounts of dietary boron in animal nutrition models.  

PubMed Central

This review summarizes evidence that supports working hypotheses for the roles of boron in animal model systems. It is well established that vascular plants, diatoms, and some species of marine algal flagellates have acquired an absolute requirement for boron, although the primary role of boron in plants remains unknown. Recent research findings suggest that physiologic amounts of supplemental dietary boron (PSB) affect a wide range of metabolic parameters in the chick and rat model systems. Much of the current interest in boron animal nutrition began with the initial finding that PSB stimulates growth in cholecalciferol (vitamin D3)-deficient chicks, but does not markedly affect growth in chicks receiving adequate vitamin D3 nutriture. The finding suggests that boron affects some aspect of vitamin D3 metabolism or is synergistic with vitamin D3 in influencing growth. Vitamin D3 regulates energy substrate utilization, and current research findings indicate that dietary boron modifies that regulatory function. The concentration of circulating glucose, the most thoroughly investigated metabolite to date, responds to PSB, especially during concomitant vitamin D3 deficiency. In chicks, PSB substantially alleviated or corrected vitamin D3 deficiency-induced elevations in plasma glucose concentrations. The influence of vitamin D3 on cartilage and bone mineralization is mediated in part through its role as a regulator of energy substrate utilization; calcification is an energy-intensive process. There is considerable evidence that dietary boron alleviates perturbations in mineral metabolism that are characteristic of vitamin D3 deficiency. In rachitic chicks, PSB alleviated distortion of the marrow sprouts of the proximal tibial epiphysial plate, a distortion characteristic of vitamin D3 deficiency.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7889878

Hunt, C D

1994-01-01

376

Geochemistry of Major Constituents, Boron and Boron Isotopes in Pore Waters from ODP Site 1202, Okinawa Trough  

Microsoft Academic Search

geochemical results show that major constituents and boron content varied largely in pore fluids and possibly were affected by sulfate reduction, re- crystallization of biogenic carbonate or silica, ash alteration, and organic matter degradation. Mixing of fluids along high-porosity sandy layers or fracture zones also changes the pore water chemical compositions significantly. The down-core distribution of B and ?11B in

Kuo-Fang Huang; Chen-Feng You; Min-Lin Shen; Hui-Ling Lin

377

Boron neutron capture therapy of glioblastoma multiforme using the p- boronophenylalanine-fructose complex and epithermal neutrons  

SciTech Connect

The amino acid analogue p-boronophenylalanine (BPA) is under investigation as a neutron capture agent for BNCT of glioblastoma multiforme. A series of patients undergoing surgical removal of tumor received BPA orally as the free amino acid. Favorable tumor/blood boron concentration ratios were obtained but the absolute amount of boron in the tumor would have been insufficient for BNCT. BPA can be solubilized at neutral pH by complexation with fructose (BPA-F). Studies with rats suggest that intraperitoneal injection of BPA-F complex produces a much higher tumor boron concentration to rat intracerebral 9L gliosarcoma that were possible with oral BPA. Higher boron concentrations have allowed higher tumor radiation doses to be delivered while maintaining the dose to the normal brain vascular endothelium below the threshold of tolerance. The experience to date of the administration of BPA-F to one patient is provided in this report.

Coderre, J.A.; Chanana, A.D.; Joel, D.D.; Liu, H.B.; Slatkin, D.N.; Wielopolski, L. [Brookhaven National Lab., Upton, NY (United States); Bergland, R.; Elowitz, E. [Beth Israel Medical Center, New York, NY (United States). Dept. of Neurosurgery; Chadha, M. [Beth Israel Medical Center, New York, NY (United States). Dept. of Radiation Oncology

1994-12-31

378

Synthesis and characterization of boron-based one-dimensional nanostructures  

NASA Astrophysics Data System (ADS)

New synthetic methods for the preparation of boron-based one-dimensional nanostructures are developed that employ catalytic chemical vapor deposition. The structures, morphologies, and elemental compositions of the nanostructures are characterized using electron microscopy and spectroscopy. Electrical-transport measurements performed on individual boron nanowires assess their potential as nanoscale interconnects. Multi-walled boron nitride nanotubes are generated from a molten salt mixture containing (NH4)2SO4, NaBH4, and Co3O4 at 300--400°C. Volatile BN-containing species generated in the molten salt are transported via a carrier gas to a nickel boride catalyst at 1100°C, whereupon precursor decomposition upon the catalyst material results in the formation of crystalline boron nitride nanotubes. The BN nanotubes have concentric-tube structures, are free of internal closures, have crystalline walls, and exhibit lengths of up to ca. 5 mum. The nanotubes often possess bulbous, flag-like, or club-like tip closures. A root-growth mechanism is proposed for the catalyzed process. This work provides the first CVD synthesis of BN nanotubes not requiring the use of carbon nanotube templates. A theoretical prediction for the existence of conductive boron nanotubes inspired our next project in the search for ideal nanostructured electrical interconnects for nanoelectronics. Promising candidates should be highly refractory, covalently bonded, and conductive irrespective of their crystallographic orientation. We report the growth of crystalline boron nanowires from a nickel boride catalyst using diborane at temperatures of 1100°C. However, our one-dimensional boron nanostructures are dense nanowhiskers rather than hollow nanotubes. Electrical-conductivity measurements indicate the boron nanowires to be semiconductors, with properties consistent with bulk elemental boron. To our knowledge, these are the first measurements reported on crystalline boron nanowires. To probe the electrical-transport properties of boron nanowires, a separation strategy was developed to remove and untangle individual nanowires for subsequent nanowire-device fabrication. Experiments identified nickel as having a sufficiently high work function to make Ohmic contacts to boron nanowires, allowing subsequent conductivity measurements, observation of a gate effect, and calculations of the transconductance and carrier mobilities. Synthetic attempts to boost conductivities into the conducting regime via doping are also described.

Otten, Carolyn Jones

379

Risk assessment of erosion from concentrated flow on rangelands using overland flow distribution and shear stress partitioning  

Technology Transfer Automated Retrieval System (TEKTRAN)

Erosion rates of overland flow on rangelands tend to be relatively low, but under certain conditions where flow is concentrated, soil loss can be significant. Therefore, a rangeland site can be highly vulnerable to soil erosion where overland flow is likely to concentrate and exert high shear stress...

380

Simple model for predicting the flux distribution through the focal plane of a multifaceted-concentrator solar furnace  

Microsoft Academic Search

The authors describe a small doubly reflecting research furnace. Its optical components, a heliostat and a concentrating array of hexagonal-in-plan-form mirrors, focus sunlight at the aperture of a cavity receiver. A perfect paraboloid of revolution would have given higher concentration ratios. But large paraboloids are difficult to make and manipulate. Small hexagons are convenient and can be close packed. Spherical

D. E. E. Carlson; R. B. Diver; E. A. Fletcher

1984-01-01

381

FREQUENCY DISTRIBUTIONS OF 90SR AND 137CS CONCENTRATIONS IN AN ECOSYSTEM OF THE 'RED FOREST' AREA IN THE CHERNOBYL EXCLUSION ZONE  

SciTech Connect

In the most highly contaminated region of the Chernobyl Exclusion Zone: the 'Red Forest' site, the accumulation of the major dose-affecting radionuclides ({sup 90}Sr and {sup 137}Cs) within the components of an ecological system encompassing 3,000 m{sup 2} were characterized. The sampled components included soils (top 0-10 cm depth), Molina caerulea (blue moor grass), Camponotus vagus (carpenter ants) and Pelobates fuscus (spade-footed toad). In a comparison among the components of this ecosystem, the {sup 90}Sr and {sup 137}Cs concentrations measured in 40 separate grids exhibited significant differences, while the frequency distribution of the values were close to a logarithmically normal leptokurtic distribution with a significant right-side skew. While it is important to identify localized areas of high contamination or 'hot spots,' including these values in the arithmetic mean may overestimate the exposure risk. In component sample sets that exhibited logarithmically normal distribution, the geometrical mean more accurately characterizes a site. Ideally, risk assessment is most confidently achieved when the arithmetic and geometrical means are most similar, meaning the distribution approaches normal. Through bioaccumulation, the highest concentrations of {sup 90}Sr and {sup 137}Cs were measured in the blue moor grass and spade-footed toad. These components also possessed distribution parameters that shifted toward a normal distribution.

Farfan, E.; Jannik, T.; Caldwell, E.

2011-10-01

382

Radiobiological evaluation of new boron delivery agents for boron neutron capture therapy  

E-print Network

This thesis evaluates the radiobiological effectiveness of three new boron compounds namely a boronated porphyrin (BOPP) and two liposome formulations for neutron capture therapy (BNCT). The methodology utilizes in vitro ...

Chung, Yoonsun

2008-01-01

383

Areal Distribution and Concentration of Contaminants of Concern in Surficial Streambed and Lakebed Sediments, Lake St. Clair and Tributaries, Michigan, 1990-2003  

USGS Publications Warehouse

As part of the Lake St. Clair Regional Monitoring Project, the U.S. Geological Survey evaluated data collected from surficial streambed and lakebed sediments in the Lake Erie-Lake St. Clair drainages. This study incorporates data collected from 1990 through 2003 and focuses primarily on the U.S. part of the Lake St. Clair Basin, including Lake St. Clair, the St. Clair River, and tributaries to Lake St. Clair. Comparable data from the Canadian part of the study area are included where available. The data are compiled into 4 chemical classes and consist of 21 compounds. The data are compared to effects-based sediment-quality guidelines, where the Threshold Effect Level and Lowest Effect Level represent concentrations below which adverse effects on biota are not expected and the Probable Effect Level and Severe Effect Level represent concentrations above which adverse effects on biota are expected to be frequent. Maps in the report show the spatial distribution of the sampling locations and illustrate the concentrations relative to the selected sediment-quality guidelines. These maps indicate that sediment samples from certain areas routinely had contaminant concentrations greater than the Threshold Effect Concentration or Lowest Effect Level. These locations are the upper reach of the St. Clair River, the main stem and mouth of the Clinton River, Big Beaver Creek, Red Run, and Paint Creek. Maps also indicated areas that routinely contained sediment contaminant concentrations that were greater than the Probable Effect Concentration or Severe Effect Level. These locations include the upper reach of the St. Clair River, the main stem and mouth of the Clinton River, Red Run, within direct tributaries along Lake St. Clair and in marinas within the lake, and within the Clinton River headwaters in Oakland County. Although most samples collected within Lake St. Clair were from sites adjacent to the mouths of its tributaries, samples analyzed for trace-element concentrations were collected throughout the lake. The distribution of trace-element concentrations corresponded well with the results of a two-dimensional hydrodynamic model of flow patterns from the Clinton River into Lake St. Clair. The model was developed independent from the bed sediment analysis described in this report; yet it showed a zone of deposition for outflow from the Clinton River into Lake St. Clair that corresponded well with the spatial distribution of trace-element concentrations. This zone runs along the western shoreline of Lake St. Clair from L'Anse Creuse Bay to St. Clair Shores, Michigan and is reflected in the samples analyzed for mercury and cadmium. Statistical summaries of the concentration data are presented for most contaminants, and selected statistics are compared to effects-based sediment-quality guidelines. Summaries were not computed for dieldrin, chlordane, hexachlorocyclohexane, lindane, and mirex because insufficient data are available for these contaminants. A statistical comparison showed that the median concentration for total DDT, hexachlorobenzene, anthracene, benz[a]anthracene, chrysene, and pyrene are greater than the Threshold Effect Concentration or Lowest Effect Level. Probable Effect Concentration Quotients provide a mechanism for comparing the concentrations of contaminant mixtures against effects-based biota data. Probable Effect Concentration Quotients were calculated for individual samples and compared to effects-based toxicity ranges. The toxicity-range categories used in this study were nontoxic (quotients 0.5). Of the 546 individual samples for which Probable Effect Concentration Quotients were calculated, 469 (86 percent) were categorized as being nontoxic and 77 (14 percent) were categorized as being toxic. Bed-sediment samples with toxic Probable Effect Concentration Quotients were collected from Paint Creek, Galloway Creek, the main stem of the Clinton River, Big Beaver Creek, Red

Rachol, Cynthia M.; Button, Daniel T.

2006-01-01

384

Ultra-high resolution mass spectroscopy of boron cluster ions  

NASA Astrophysics Data System (ADS)

Boron clusters have recently received considerable attention as a possible solution to the throughput dilemma associated with ultra-low energy (sub keV) p-type source drain extension implants required by cutting edge complimentary metal-oxide semiconductor (CMOS) technology. Boron cluster ion beams contain many masses due to the binomial distribution of the two naturally occurring isotopes (masses 10 and 11) of boron. The broadness of the mass distribution peak in the dispersive plane is further complicated by a plurality of ion states, due to the varying number of hydrogen atoms remaining attached to the borohydride molecule when it is ionized. The B18Hx+ cluster ion mass spectrum from an electron impact ionization source will be analyzed in detail. An ultra-high resolution mass spectrum, exhibiting 1 AMU resolution of a mass 220 cluster ion will be shown. It will be compared to high-resolution spectra of decaborane (B 10H 14) cluster ions obtained from natural abundance decaborane and from isotopically enriched material. The deconvolution of the binominal distribution from ion states present in the cluster ion beam reveals the hydrogen distribution function. The hydrogen distribution functions as well as the binomial distributions will be presented and discussed. Physical models will be presented that explain the origin of hydrogen distribution function for these high mass borohydride cluster ions. This ultra-high mass resolution is usually unavailable to the ion implant community, however our 120° mass analyzing magnet and the extremely low emittance of the ion beam extracted from the ClusterIon ® source coupled with a variable width beam defining aperture and variable width mass defining slits allow for superior mass resolution.

Jacobson, Dale; Horsky, Thomas; Krull, Wade; Milgate, Bob

2005-08-01

385

Jaguar Procedures for Detonation Behavior of Explosives Containing Boron  

NASA Astrophysics Data System (ADS)

The Jaguar product library was expanded to include boron and boron containing products by analysis of Available Hugoniot and static volumetric data to obtain constants of the Murnaghan relationships for the components. Experimental melting points were also utilized to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX—boron mixtures calculated with these relationships using Jaguar are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that the boron does not react near the detonation front or that boron mixtures exhibit eigenvalue detonation behavior (as shown by some aluminized explosives), with higher detonation velocities at the initial points. Analyses of calorimetric measurements for RDX—boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the detonation properties of the formulation.

Stiel, L. I.; Baker, E. L.; Capellos, C.

2009-12-01

386

Initial boronization of PBX-M using ablation of solid boronized probes  

SciTech Connect

The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 [mu] boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. (California Univ., Los Angeles, CA (United States). Inst. of Plasma and Fusion Research); Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. (Oak Ridge National Lab., TN (United States)); Jones, S. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1993-05-01

387

Initial boronization of PBX-M using ablation of solid boronized probes  

SciTech Connect

The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B{sub 4}C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 {mu} boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. [California Univ., Los Angeles, CA (United States). Inst. of Plasma and Fusion Research; Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. [Oak Ridge National Lab., TN (United States); Jones, S. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1993-05-01

388

Tautomerism of anthraquinones: X. Quinizarin boron complex  

Microsoft Academic Search

Products of reactions of hydroxyanthraquinones with boric acid exist as equilibrium mixtures of tautomeric boron complexes\\u000a and boric acid esters in which one or two boron atoms are not coordinated to carbonyl groups. Tautomerism is responsible for\\u000a the appearance of several ?l,? bands in the electronic absorption spectra and considerable differences in the data obtained by different authors. Boron-containing\\u000a quinizarin

V. Ya. Fain; B. E. Zaitsev; M. A. Ryabov

2010-01-01

389

An exceptionally high boron content supramolecular cuboctahedron.  

PubMed

A boron-rich supramolecular cuboctahedron containing an impressive 240 boron atoms has been synthesized via coordination-driven assembly. The cuboctahedron, which is composed of Cu(2+) paddle-wheel nodes and carborane-isophthalic acids, was obtained simply and in high purity. The ability to precisely characterize the nanostructure via X-ray diffraction makes it unique among boron-rich nanostructures. PMID:23863859

Clingerman, Daniel J; Kennedy, Robert D; Mondloch, Joseph E; Sarjeant, Amy A; Hupp, Joseph T; Farha, Omar K; Mirkin, Chad A

2013-12-21

390

First-order based cumulative distribution function for solute concentration in heterogeneous aquifers: Theoretical analysis and implications for human health risk assessment  

NASA Astrophysics Data System (ADS)

the uncertainty of solute concentration in heterogeneous aquifers is an important step in both human health and ecological risk analysis. The need for a probabilistic representation of transport is justified by the incomplete characterization of the subsurface. We derive the one-point concentration cumulative distribution function (CDF) while taking into account the spatial statistical structure of the hydraulic conductivity, space dimensionality, the injection source size, the Péclet number, and the sampling volume at the monitoring location. The CDF is application oriented and derived at first order in the log-conductivity variance. We illustrate how several key parameters control the shape of the concentration CDF. The CDF shape is important since it reflects both uncertainty and the dilution state of the plume. The transition from a bimodal to a unimodal CDF is examined and results are further supported by analyzing the concentration coefficient of variation. Results indicate the significance of the statistical anisotropy ratio (i.e., the ratio between the hydraulic conductivity correlation scales) in determining the CDF shape. The importance of the sampling volume in the tails of the concentration CDF and a comparison between the proposed model with the ?-CDF approach (i.e., beta distribution) are also shown. Finally, we illustrate how the framework could be used in applications by evaluating the human health risk CDF. Our results are formally valid for low to moderate heterogeneous aquifers and source sizes small as compared to the hydraulic conductivity correlation length. The proposed approach can serve as a benchmark tool for other methods.

Barros, F. P. J.; Fiori, A.

2014-05-01

391

Scalable, non-invasive glucose sensor based on boronic acid functionalized carbon nanotube transistors  

NASA Astrophysics Data System (ADS)

We developed a scalable, label-free all-electronic sensor for D-glucose based on a carbon nanotube transistor functionalized with pyrene-1-boronic acid. This sensor responds to glucose in the range 1 ?M-100 mM, which includes typical glucose concentrations in human blood and saliva. Control experiments establish that functionalization with the boronic acid provides high sensitivity and selectivity for glucose. The devices show better sensitivity than commercial blood glucose meters and could represent a general strategy to bloodless glucose monitoring by detecting low concentrations of glucose in saliva.

Lerner, Mitchell B.; Kybert, Nicholas; Mendoza, Ryan; Villechenon, Romain; Bonilla Lopez, Manuel A.; Charlie Johnson, A. T.

2013-05-01

392

Brain tumour and infiltrations dosimetry of boron neutron capture therapy combined with 252Cf brachytherapy.  

PubMed

This article presents a dosimetric investigation of boron neutron capture therapy (BNCT) combined with (252)Cf brachytherapy for brain tumour control. The study was conducted through computational simulation in MCNP5 code, using a precise and discrete voxel model of a human head, in which a hypothetical brain tumour was incorporated. A boron concentration ratio of 1:5 for healthy-tissue: tumour was considered. Absorbed and biologically weighted dose rates and neutron fluency in the voxel model were evaluated. The absorbed dose rate results were exported to SISCODES software, which generates the isodose surfaces on the brain. Analyses were performed to clarify the relevance of boron concentrations in occult infiltrations far from the target tumour, with boron concentration ratios of 1:1 up to 1:50 for healthy-tissue:infiltrations and healthy-tissue:tumour. The average biologically weighted dose rates at tumour area exceed up to 40 times the surrounding healthy tissue dose rates. In addition, the biologically weighted dose rates from boron have the main contribution at the infiltrations, especially far from primary tumour. In conclusion, BNCT combined with (252)Cf brachytherapy is an alternative technique for brain tumour treatment because it intensifies dose deposition at the tumour and at infiltrations, sparing healthy brain tissue. PMID:21705767

Brandão, Sâmia F; Campos, Tarcísio P R

2012-04-01

393

Conduction mechanism in boron carbide  

NASA Technical Reports Server (NTRS)

Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

Wood, C.; Emin, D.

1984-01-01

394

Experimental observation of boron nitride chains.  

PubMed

We report the formation and characterization of boron nitride atomic chains. The chains were made from hexagonal boron nitride sheets using the electron beam inside a transmission electron microscope. We find that the stability and lifetime of the chains are significantly improved when they are supported by another boron nitride layer. With the help of first-principles calculations, we prove the heteroatomic structure of the chains and determine their mechanical and electronic properties. Our study completes the analogy between various boron nitride and carbon polymorphs, in accordance with earlier theoretical predictions. PMID:25299068

Cretu, Ovidiu; Komsa, Hannu-Pekka; Lehtinen, Ossi; Algara-Siller, Gerardo; Kaiser, Ute; Suenaga, Kazu; Krasheninnikov, Arkady V

2014-12-23

395

Mineral resource of the month: boron  

USGS Publications Warehouse

The article offers information on the mineral, boron. Boron compounds, particularly borates, have more commercial applications than its elemental relative which is a metalloid. Making up the 90% of the borates that are used worldwide are colemanite, kernite, tincal, and ulexite. The main borate deposits are located in the Mojave Desert of the U.S., the Tethyan belt in southern Asia, and the Andean belt of South America. Underground and surface mining are being used in gathering boron compounds. INSETS: Fun facts;Boron production and consumption.

Crangle, Robert D., Jr.

2012-01-01

396

Molecular basis of adaptation to high soil boron in wheat landraces and elite cultivars.  

PubMed

Environmental constraints severely restrict crop yields in most production environments, and expanding the use of variation will underpin future progress in breeding. In semi-arid environments boron toxicity constrains productivity, and genetic improvement is the only effective strategy for addressing the problem. Wheat breeders have sought and used available genetic diversity from landraces to maintain yield in these environments; however, the identity of the genes at the major tolerance loci was unknown. Here we describe the identification of near-identical, root-specific boron transporter genes underlying the two major-effect quantitative trait loci for boron tolerance in wheat, Bo1 and Bo4 (ref. 2). We show that tolerance to a high concentration of boron is associated with multiple genomic changes including tetraploid introgression, dispersed gene duplication, and variation in gene structure and transcript level. An allelic series was identified from a panel of bread and durum wheat cultivars and landraces originating from diverse agronomic zones. Our results demonstrate that, during selection, breeders have matched functionally different boron tolerance alleles to specific environments. The characterization of boron tolerance in wheat illustrates the power of the new wheat genomic resources to define key adaptive processes that have underpinned crop improvement. PMID:25043042

Pallotta, Margaret; Schnurbusch, Thorsten; Hayes, Julie; Hay, Alison; Baumann, Ute; Paull, Jeff; Langridge, Peter; Sutton, Tim

2014-10-01

397

New Applications of Boron Dihalides and Organotrifluoroborates in Organic Synthesis.  

E-print Network

??This dissertation summarizes research focused on the use of boron dihalides and organotrifluoroborates in organic synthesis. The boron dihalide mediated aryl propargyl ether cleavage reactions… (more)

Hall, Kelly Elizabeth

2013-01-01

398

Friction anisotropy in boronated graphite  

NASA Astrophysics Data System (ADS)

Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1-0.35 in the direction of basal plane and becomes high 0.2-0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

Kumar, N.; Radhika, R.; Kozakov, A. T.; Pandian, R.; Chakravarty, S.; Ravindran, T. R.; Dash, S.; Tyagi, A. K.

2015-01-01

399

The concentration and distribution of selected heavy metals (Pb, Cd, Cu and Zn) in soils collected from the rice fields of MADA in Kedah, Malaysia  

NASA Astrophysics Data System (ADS)

The present study was carried out to determine the concentration and distribution status of some heavy metals (Pb, Cd, Cu and Zn) in the paddy field soil fractions of MADA in the state of Kedah, Malaysia. Five replicate samples were randomly collected from five paddy fields in the MADA area of Jitra. The heavy metals in the soil were extracted using sequential extraction method that was presented by Badri and Aston [1], which consisted of four different fractions using different reagents. The first fraction of extraction is the easily leachable and freely exchangeable fraction (ELFE), which uses ammonium acetate (NH4CH3COO). The second fraction is acid reduction fraction (AR), which uses hydroxylamine chloride (NH2OH_HCl), while the third fraction of extraction called the organic oxidation fraction (OO) was carried out using the combination of hydrogen peroxide (H2O2), and ammonium acetate (NH4CH3COO). The last fraction called the resistant fraction uses concentrated nitrate acid (HNO3) and perchlorate acid (HClO4). Generally, all the paddy soils in this study contained low levels of Pb, Cd, Cu and Zn concentration compared to the other paddy soils. The result showed that the concentration of heavy metals in the studied area was in the following decreasing order i.e.: Pb < Zn < Cu < Cd. The results also showed that the concentration of heavy metals in the paddy soil fractions were mainly concentrated in the RR fraction except for Pb, which was at the highest level in the OO fraction, whilst Cd was more evenly distributed throughout the whole soil fraction. In general, Pb was the highest metal concentration found in the OO fraction followed by Zn in the RR fraction of the soil fractions.

Alrawiq, Nasser; Khairiah, J.; Latif, T. M.; Ismail, S. B.

2013-11-01

400

Studies of chemiluminescence in boron atom reactions  

SciTech Connect

Chemiluminescence has been observed in the single collision reactions of boron atoms with O/sub 2/, SO/sub 2/, N/sub 2/O, NO/sub 2/, and H/sub 2/O/sub 2/. The experiments were performed in a beam-gas apparatus using photon counting to detect the optical signals. The electronically excited A/sup 2/pi state of BO was observed in all the reactions. In addition the BO/sup -/ excited state, B/sup 2/..sigma../sup +/, was observed in the reaction of boron with N/sub 2/O. Excited BO/sub 2/ (A/sup 2/pi/sub u/) was observed in the reaction with SO/sub 2/ and excited OH (A/sup 2/..sigma../sup +/) was observed in the reaction with H/sub 2/O/sub 2/. Cross sections for the production of electronically excited molecules were determined. These cross sections for the reactions with O/sub 2/, SO/sub 2/, N/sub 2/O, NO/sub 2/, and H/sub 2/O/sub 2/ are, respectively, 0.048 A/sup 2/, 0.078 A/sup 2/, 0.011 A/sup 2/, 0.19 A/sup 2/, and 0.0058 A/sup 2/. In those reactions involving more than one chemiluminescent product channel, branching ratios were obtained for the observed products. The vibrational distributions in the electronically excited states of BO were determined for all the reactions and were analyzed using information theory. Some implications of the results are discussed.

DeHaven, J.J.

1982-01-01

401

Short-term coral bleaching is not recorded by skeletal boron isotopes.  

PubMed

Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (?11B), carbon (?13C), oxygen (?18O) isotopes, Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca ratios, as well as chlorophyll a concentrations and calcification rates were measured on coral skeletal material corresponding to the period during and immediately after the elevated temperature treatment and again after 6 weeks of recovery on the reef. We show that under these conditions, coral bleaching did not affect the boron isotopic signature in any coral species tested, despite significant changes in coral physiology. This contradicts published findings from coral cores, where significant decreases in boron isotopes were interpreted as corresponding to times of known mass bleaching events. In contrast, ?13C and ?18O exhibited major enrichment corresponding to decreases in calcification rates associated with bleaching. Sr/Ca of bleached corals did not consistently record the 1.2°C difference in seawater temperature during the bleaching treatment, or alternatively show a consistent increase due to impaired photosynthesis and calcification. Mg/Ca, U/Ca, and Ba/Ca were affected by coral bleaching in some of the coral species, but the observed patterns could not be satisfactorily explained by temperature dependence or changes in coral physiology. This demonstrates that coral boron isotopes do not record short-term bleaching events, and therefore cannot be used as a proxy for past bleaching events. The robustness of coral boron isotopes to changes in coral physiology, however, suggests that reconstruction of seawater pH using boron isotopes should be uncompromised by short-term bleaching events. PMID:25396422

Schoepf, Verena; McCulloch, Malcolm T; Warner, Mark E; Levas, Stephen J; Matsui, Yohei; Aschaffenburg, Matthew D; Grottoli, Andréa G

2014-01-01

402

Short-Term Coral Bleaching Is Not Recorded by Skeletal Boron Isotopes  

PubMed Central

Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (?11B), carbon (?13C), oxygen (?18O) isotopes, Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca ratios, as well as chlorophyll a concentrations and calcification rates were measured on coral skeletal material corresponding to the period during and immediately after the elevated temperature treatment and again after 6 weeks of recovery on the reef. We show that under these conditions, coral bleaching did not affect the boron isotopic signature in any coral species tested, despite significant changes in coral physiology. This contradicts published findings from coral cores, where significant decreases in boron isotopes were interpreted as corresponding to times of known mass bleaching events. In contrast, ?13C and ?18O exhibited major enrichment corresponding to decreases in calcification rates associated with bleaching. Sr/Ca of bleached corals did not consistently record the 1.2°C difference in seawater temperature during the bleaching treatment, or alternatively show a consistent increase due to impaired photosynthesis and calcification. Mg/Ca, U/Ca, and Ba/Ca were affected by coral bleaching in some of the coral species, but the observed patterns could not be satisfactorily explained by temperature dependence or changes in coral physiology. This demonstrates that coral boron isotopes do not record short-term bleaching events, and therefore cannot be used as a proxy for past bleaching events. The robustness of coral boron isotopes to changes in coral physiology, however, suggests that reconstruction of seawater pH using boron isotopes should be uncompromised by short-term bleaching events. PMID:25396422

Schoepf, Verena; McCulloch, Malcolm T.; Warner, Mark E.; Levas, Stephen J.; Matsui, Yohei; Aschaffenburg, Matthew D.; Grottoli, Andréa G.

2014-01-01

403

Nuclear magnetic resonance study of Gd-based nanoparticles to tag boron compounds in boron neutron capture therapy  

SciTech Connect

We report the investigation of new organic complexes containing a magnetic moment (Gd-based molecular nanomagnets), which can serve the double purpose of acting as boron neutron capture therapy (BNCT) agents, and at the same time act as contrast agents to detect the molecule in the tissue by a proton magnetic resonance imaging (MRI). We also explore the possibility of monitoring the concentration of the BNCT agent directly via proton and boron NMR relaxation. The absorption of {sup 10}B-enriched molecules inside tumoral liver tissues has been shown by NMR measurements and confirmed by {alpha} spectroscopy. A new molecular Gd-tagged nanomagnet and BNCT ag