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1

The effects of low boron on growth, gas exchange, boron concentration and distribution of ‘Newhall’ navel orange ( Citrus sinensis Osb.) plants grafted on two rootstocks  

Microsoft Academic Search

The effects of low boron (B) on plant growth, photosynthesis, B concentration and distribution of ‘Newhall’ orange (Citrus sinensis Osb.) plants grafted on either Trifoliate orange (Poncirus trifoliata (L.) Raf.) or Carrizo citrange [C. sinensis (L.) Osb.×Poncirus trifoliata (L.) Raf.] rootstocks were investigated. One-year-old plants of the two scion-rootstock combinations were grown for 183 days in sand:perlite (1:1, v\\/v) medium

Ou Sheng; Shangwei Song; Shuang Peng; Xiuxin Deng

2009-01-01

2

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

3

Boron isotopic composition and concentration in modern marine carbonates  

Microsoft Academic Search

The boron isotopic compositions and boron concentrations of selected modern marine carbonates were analysed by negative thermal ionization mass spectrometry with a 2 reproducibility of standards and samples better than 0.7%. It was found that the boron isotopic compositions of modern marine carbonates fall within a relatively narrow range (+22.1 ± 3%. relative to NBS SRM951 boric acid standard) for

N. G. Hemming; G. N. Hanson

1992-01-01

4

Concentrations of Boron, Molybdenum, and Selenium in Chinook Salmon  

Microsoft Academic Search

The concentrations of boron, molybdenum, and selenium in young chinook salmon Oncorhynchus tshawytscha were determined in three partial life cycle chronic toxicity studies. In each study, fish were exposed to a mixture of boron, molybdenum, selenate, and selenite in the proportions found in subsurface agricultural drainage water in the basin of the San Joaquin Valley, California. Tests were conducted in

Steven J. Hamilton; Raymond H. Wiedmeyer

1990-01-01

5

Differentiation in boron distribution in adult male and female rats' normal brain: a BNCT approach.  

PubMed

Boron distribution in adult male and female rats' normal brain after boron carrier injection (0.005 g Boric Acid+0.005 g Borax+10 ml distilled water, pH: 7.4) was studied in this research. Coronal sections of control and trial animal tissue samples were irradiated with thermal neutrons. Using alpha autoradiography, significant differences in boron concentration were seen in forebrain, midbrain and hindbrain sections of male and female animal groups with the highest value, four hours after boron compound injection. PMID:22484141

Goodarzi, Samereh; Pazirandeh, Ali; Jameie, Seyed Behnamedin; Khojasteh, Nasrin Baghban

2012-06-01

6

Concentrations of arsenic, antimony, and boron in steam and steam condensate at The Geysers, California  

USGS Publications Warehouse

Studies at The Geysers Geothermal Field, California indicate that under some circumstances elements that are transported in the vapor phase can become enriched in the liquid phase. Waters from two condensate traps (steam traps) on steam lines at The Geysers are enriched with arsenic, antimony, and boron compared to the concentrations of these elements in coexisting steam. Concentrations of boron in condensate-trap waters were as high as 160 mg/L, arsenic as high as 35 mg/L, and antimony as high as 200 ??g/L. Enrichment of arsenic, antimony, and boron is at least partially controlled by the partitioning of these elements into the liquid phase, according to their vapor-liquid distribution coefficients, after they are transported in steam. Several of the elements that are most soluble in steam, including arsenic and antimony, are part of the trace-element suite that characterizes precious-metal epithermal ore deposits. ?? 1987.

Smith, C. L.; Ficklin, W. H.; Thompson, J. M.

1987-01-01

7

Influence of boron concentration on the oxidation-induced stacking fault ring in Czochralski silicon crystals  

NASA Astrophysics Data System (ADS)

The influence of the boron doping level in the range of 1 × 1015-2 × 1019 cm-3 on the position of the oxidation-induced stacking fault ring (R-OSF) in silicon crystals has been investigated by experiments and numerical simulation. For low boron-doped crystals, the position of the R-OSF is described by a critical value Ccrit defined by the ratio of the pull rate and the temperature gradient in the crystal at the solid/liquid interface. Boron concentrations higher than 1017 cm-3 shift the position of the R-OSF towards the wafer center without change of growth parameters. The critical value Ccrit converts into a function Ccrit(CB, depending linearly on the boron concentration CB. Crystal-originated particles (COP) and gate oxide integrity (GOI) yield distributions which are consistent with the R-OSF pattern. A low COP density and a high GOI yield are observed outside the ring; a high COP density and a medium GOI yield in the inner region bordered by the ring. It is assumed that boron atoms modify the thermodynamical properties of vacancies and self-interstitials.

Dornberger, E.; Gräf, D.; Suhren, M.; Lambert, U.; Wagner, P.; Dupret, F.; von Ammon, W.

1997-10-01

8

Quantitative Analysis of the Wide Range of Concentrations of Boron in Silicon by SIMS  

NASA Astrophysics Data System (ADS)

A direct measurement method of impurity concentrations in boron doped silicon by SIMS is reported. Boron concentrations in silicon in the range of 1014 to 1019 Bcm-3 are measured in comparison with photoluminescence studies, and the resistivity measurements are made in reference to a nuclear track technique. The background signal of boron ions due to origins other than doped silicon is related to the primary ion current. The detection limit of boron in silicon is as low as 1014 Bcm-3 and is expected to be lowered further by reducing the boron background.

Ochiai, Yuichi; Nannichi, Yasuo; Masuda, Kohzoh

1980-12-01

9

The influence of concentrate alkalinity on electrodialytic boron transport  

Microsoft Academic Search

Both pressure driven and electro-membrane processes show better boron removal efficiency when carried under alkaline conditions when the boric acid is ionized to a large extent. Even under such conditions the electrodialysis (ED) performance is, however, reported to be poor since low boron current efficiency and low boron fluxes are observed. In the present work the influence of the ED

M. Turek; B. Bandura; P. Dydo

2008-01-01

10

Fluorescence lifetime measurements of boronate derivatives to determine glucose concentration  

SciTech Connect

A novel investigation into the fluorescence lifetimes of molecules, both established and newly designed, was performed. These molecules are the basis of a continuous, minimally invasive, glucose sensor based on fluorescence lifetime measurements. This sensor, if coupled with an automated insulin delivery device, would effectively create an artificial pancreas allowing for the constant monitoring and control of glucose levels in a person with diabetes. The proposed sensor includes a fluorescent molecule that changes its' fluorescence properties upon binding selectively and reversibly to glucose. One possible sensor molecule is N-methyl-N-(9-methylene anthryl)-2-methylenephenylboronic acid (AB). The fluorescence intensity of AB was shown to change in response to changing glucose concentrations. (James, 1994) James proposed that when glucose binds to AB the fluorescence intensity increases due to an enhancement of the N{yields}B dative bond which prevents photoinduced electron transfer (PET). PET from the amine (N) to the fluorophore (anthracene) quenches the fluorescence. The dative bond between the boron and the amine can prevent PET by involving the lone pair of electrons on the amine in interactions with the boron rather than allowing them to be transferred to the fluorophore. Results of this research show the average fluorescence lifetime of AB also changes with glucose concentration. It is proposed that fluorescence is due to two components: (1) AB with an enhanced N{yields}B interaction, and no PET, and (2) AB with a weak N{yields}B interaction, resulting in fluorescence quenching by PET. Lifetime measurements of AB as a function of both the pH of the solvent and glucose concentration in the solution were made to characterize this two component system and investigate the nature of the N{yields}B bond. Measurements of molecules similar to AB were also performed in order to isolate behavior of specific AB constituents. These molecules are 9-(Methylaminomethyl)-anthracene (MAMA), and N-benzyl-N-methyl-N-methyl anthracene (AB-B). Fluorescence lifetime measurements confirmed the two species of AB, with and without PET. Fluorescence lifetimes were approximately 11 nsec without PET and 3 nsec with PET. The degree of the interaction between the N and the B atoms was also determined by fluorescence lifetime measurements. Electron transfer rates of AB were measured to be on the order of 10{sup 8} sec{sup -1}. Analysis of AB as a glucose sensor shows it has the potential for measuring glucose concentrations in solution with less than 5% error. Two novel glucose sensing molecules, Chloro-oxazone boronate (COB) and Napthyl-imide boronate (NIB), were synthesized. Both molecules have a N{yields}B dative bond similar to AB, but with longer wavelength fluorophores. COB and NIB were found to be unacceptable for use as glucose sensor molecules due to the small changes in average fluorescence lifetime.

Gable, J H

2000-06-01

11

Boron  

MedlinePLUS

... and muscle coordination. Women sometimes use capsules containing boric acid, the most common form of boron, inside the vagina to treat yeast infections. People also apply boric acid to the skin as an astringent or to ...

12

Boron distribution in the subsurface region of heavily doped IIb type diamond  

NASA Astrophysics Data System (ADS)

For the first time investigations of the boron distribution in the subsurface region of HPHT boron-doped diamond that is promising for applications in electronics were carried out by X-ray photoelectron (XPS) and Raman spectroscopy. It was found from XPS data that the boron content decreased gradually more than one order of magnitude in depth of surface. The first-principle calculations have shown that the Raman polarizability in the crossed polarization configuration should increase considerably with boron doping. The Raman spectra from as-grown and polished surfaces of heavily boron-doped diamond are discussed in the context of theoretical results.

Mavrin, B. N.; Denisov, V. N.; Popova, D. M.; Skryleva, E. A.; Kuznetsov, M. S.; Nosukhin, S. A.; Terentiev, S. A.; Blank, V. D.

2008-05-01

13

Effect of boron concentration on recombination at the p-Si-Al2O3 interface  

NASA Astrophysics Data System (ADS)

We examine the surface passivation properties of Al2O3 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 × 1015 to 5.2 × 1019 cm-3. Atmospheric pressure chemical vapor deposition and thermal atomic layer deposition are used to deposit the Al2O3 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, Sn0, which describes the chemical passivation of the interface, is independent of the surface boron concentration Ns for Ns ? 3 × 1019 cm-3, and in excellent agreement with values calculated from the interface state density Dit and capture coefficients cn and cp measured on undiffused boron-doped surfaces. We conclude that the physical properties of the Si-Al2O3 interface are independent of the boron dopant concentration over this range.

Black, Lachlan E.; Allen, Thomas; McIntosh, Keith R.; Cuevas, Andres

2014-03-01

14

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

15

Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial ?-doped diamond layers  

NASA Astrophysics Data System (ADS)

To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 1020 cm-3 were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p-/p++/p- multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.

Araújo, D.; Alegre, M. P.; Piñero, J. C.; Fiori, A.; Bustarret, E.; Jomard, F.

2013-07-01

16

Boron concentration profiling by high angle annular dark field-scanning transmission electron microscopy in homoepitaxial ?-doped diamond layers  

SciTech Connect

To develop further diamond related devices, the concentration and spatial location of dopants should be controlled down to the nanometer scale. Scanning transmission electron microscopy using the high angle annular dark field mode is shown to be sensitive to boron doping in diamond epilayers. An analytical procedure is described, whereby local boron concentrations above 10{sup 20} cm{sup ?3} were quantitatively derived down to nanometer resolution from the signal dependence on thickness and boron content. Experimental boron local doping profiles measured on diamond p{sup ?}/p{sup ++}/p{sup ?} multilayers are compared to macroscopic profiles obtained by secondary ion mass spectrometry, avoiding reported artefacts.

Araújo, D.; Alegre, M. P.; Piñero, J. C. [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain)] [Dpto Ciencia de los Materiales, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain); Fiori, A.; Bustarret, E. [Institut Néel, CNRS-Université Joseph Fourier, 25 av. des Martyrs, 38042 Grenoble (France)] [Institut Néel, CNRS-Université Joseph Fourier, 25 av. des Martyrs, 38042 Grenoble (France); Jomard, F. [Groupe d'Etude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 av. des Etats-Unis, 78035 Versailles Cedex (France)] [Groupe d'Etude de la Matière Condensée (GEMaC), UMR 8635 du CNRS, UVSQ, 45 av. des Etats-Unis, 78035 Versailles Cedex (France)

2013-07-22

17

Indirect electrochemical oxidation of reverse osmosis membrane concentrates at boron-doped diamond electrodes  

Microsoft Academic Search

The treatment or disposal of concentrates generated from the filtrative treatment of water is rapidly becoming a factor of major environmental concern. This preliminary study discusses a novel approach in the abatement of reverse osmosis membrane retentate i.e. electrochemical oxidation. The recalcitrant organic constituents as well as the ammonia nitrogen in the retentate could be readily oxidised using boron-doped diamond

K. Van Hege; M. Verhaege; W. Verstraete

2002-01-01

18

Influence of boron concentration on growth characteristic and electro-catalytic performance of boron-doped diamond electrodes prepared by direct current plasma chemical vapor deposition  

NASA Astrophysics Data System (ADS)

A series of boron-doped diamond (BDD) electrodes were prepared by direct current plasma chemical vapor deposition (DC-PCVD) with different compositions of CH 4/H 2/B(OCH 3) 3 gas mixture. A maximum growth rate of 0.65 mg cm -2 h -1 was obtained with CH 4/H 2/B(OCH 3) 3 radio of 4/190/10 and this growth condition was also a turning point for discharge plasma stability which arose from the addition of B(OCH 3) 3 that changed electron energy distribution and influenced the plasma reaction. The surface coating structure and electro-catalytic performance of the BDD electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Hall test, and electrochemical measurement and electro-catalytic oxidation in phenol solution. It is suggested that the boron doping level and the thermal stress in the films are the main factors affecting the electro-catalytic characteristics of the electrodes. Low boron doping level with CH 4/H 2/B(OCH 3) 3 ratio of 4/199/1 decreased the films electrical conductivity and its electro-catalytic activity. When the carrier concentration in the films reached around 10 20 cm -3 with CH 4/H 2/B(OCH 3) 3 ratio over a range of 4/195/5-4/185/15, the thermal stress in the films was the key reason that influenced the electro-catalytic activity of the electrodes for its effect on diamond lattice expansion. Therefore, the BDD electrode with modest CH 4/H 2/B(OCH 3) 3 ratio of 4/190/10 possessed the best phenol removal efficiency.

Feng, Yujie; Lv, Jiangwei; Liu, Junfeng; Gao, Na; Peng, Hongyan; Chen, Yuqiang

2011-02-01

19

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

20

The measurement of thermal neutron flux depression for determining the concentration of boron in blood.  

PubMed

Boron neutron capture therapy (BNCT) is a form of targeted radiotherapy that relies on the uptake of the capture element boron by the volume to be treated. The treatment procedure requires the measurement of boron in the patient's blood. The investigation of a simple and inexpensive method for determining the concentration of the capture element 10B in blood is described here. This method, neutron flux depression measurement, involves the determination of the flux depression of thermal neutrons as they pass through a boron-containing sample. It is shown via Monte Carlo calculations and experimental verification that, for a maximum count rate of 1 x 10(4) counts/s measured by the detector, a 10 ppm 10B sample of volume 20 ml can be measured with a statistical precision of 10% in 32 +/- 2 min. For a source activity of less than 1.11 x 10(11) Bq and a maximum count rate of less than 1 x 10(4) counts/s, a 10 ppm 10B sample of volume 20 ml can be measured with a statistical precision of 10% in 58 +/- 3 min. It has also been shown that this technique can be applied to the measurement of the concentration of any element with a high thermal neutron cross section such as 157Gd. PMID:11277219

Brooke, S L; Green, S; Charles, M W; Beddoe, A H

2001-03-01

21

Variation of carbon concentration, ion energy, and ion current density of magnetron-sputtered boron carbonitride films  

Microsoft Academic Search

Diamond, cubic boron nitride and also ternary materials consisting of boron, carbon and nitrogen exhibit an extraordinary combination of extreme mechanical and physical properties due to their bonding characteristics and crystal structure. This results in a high application potential in protective and functional layers. Taking into account the special properties of these phases, the compositions inside the B?C?N concentration triangle

S. Ulrich; A. Kratzsch; H. Leiste; M. Stüber; P. Schloßmacher; H. Holleck; J. Binder; D. Schild; S. Westermeyer; P. Becker; H. Oechsner

1999-01-01

22

Direct visualization of boron dopant distribution and coordination in individual chemical vapor deposition nanocrystalline B-doped diamond grains  

NASA Astrophysics Data System (ADS)

The boron dopant distribution in individual heavily boron-doped nanocrystalline diamond film grains, with sizes ranging from 100 to 350 nm in diameter, has been studied using a combination of high resolution annular dark field scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy. Using these tools, the boron distribution and local boron coordination have been determined. Quantification results reveal embedding of B dopants in the diamond lattice, and a preferential enrichment of boron at defective areas and twin boundaries. Coordination mapping reveals a distinct difference in coordination of the B dopants in ``pristine'' diamond areas and in defective regions.

Lu, Ying-Gang; Turner, Stuart; Verbeeck, Johan; Janssens, Stoffel D.; Wagner, Patrick; Haenen, Ken; Van Tendeloo, Gustaaf

2012-07-01

23

Quantitative relationships between boron and mannitol concentrations in phloem exudates of Olea europaea leaves under contrasting boron supply conditions  

Microsoft Academic Search

Boron remobilization (BR) occurs in plants that form and export phloem–mobile borate–polyol complexes. Previous studies demonstrate\\u000a that a quantitative relationship exists between polyol translocation and BR. Here we investigate if mannitol translocation\\u000a is quantitatively related to BR in olive plants thus allowing acclimation to boron limiting conditions. Plants were cultivated\\u000a under different boron supply ranging from adequate (23 ?M) to insufficient

Georgios Liakopoulos; Sotiria Stavrianakou; Dimosthenis Nikolopoulos; Evangelos Karvonis; Kornilios-Andrianos Vekkos; Varvara Psaroudi; George Karabourniotis

2009-01-01

24

How does the boron concentration affect hydrogen storage in lithium decorated zero- and two-dimensional boron-carbon compounds?  

PubMed

A balance between the hydrogen capacity and reversibility is a big challenge in the search for hydrogen storage materials. Using van der Waals-corrected density functional theory, we perform a detailed study of the hydrogen molecules adsorption on lithium (Li) decorated zero- and two-dimensional boron-carbon (B-C) compounds. It is found that not only the Li bond strength but also the number of adsorbed hydrogen molecules depends on the B concentration. First, the binding of Li on the B-C compounds strengthens with the increase of the B concentration due to the stronger hybridization between the lowest unoccupied molecular orbitals of the B-C compounds and Li 2p orbitals. Thus, Li atoms are not likely to form clusters, indicating a good reversible hydrogen storage. Second, higher B concentration results in weaker electric field produced by the charge transfer from Li to the B-C compounds. Therefore, one Li atom can adsorb up to 5H(2) molecules with the B concentration less than 50%. In contrast, the adsorption number of H(2) molecules is reduced to 4 when the B concentration is greater than or equal to 50%. Third, using a statistical model parametrized by the results of ab initio calculations, the adsorption and desorption of molecular hydrogens are calculated at ambient temperature and pressure. We find that the usable number of adsorbed H(2) per Li under ambient conditions decreases with the increase of B concentration. These results can serve as a guide in the design of new hydrogen storage materials based on B-C compounds. PMID:23318411

Ye, Xiao-Juan; Liu, Chun-Sheng; Jia, Ran; Zeng, Zhi; Zhong, Wei

2013-02-21

25

BLOOD BORON CONCENTRATIONS IN PREGNANT RATS FED BORIC ACID THROUGHOUT GESTATION  

Microsoft Academic Search

Timed-mated Sprague-Dawley rats (28 to 32\\/group) were exposed to boric acid (BA) in the diet from Gestational Day (GD) 0 to 20. Dietary concentrations of added BA (0%, 0.025%, 0.050%, 0.075%, O.lOO%, or 0.200%) yielded average daily intakes equivalent to 0,3, 6, 10, 13, or 25 mg boron\\/kg body weight\\/d. Dams and their fetuses were evaluated for evidence of maternal

CATHERINE J. PRICE; PHILIP L. STRONG; F. JAY MURRAY; MARGARET M. GOLDBERGS

26

OsNIP3;1, a rice boric acid channel, regulates boron distribution and is essential for growth under boron-deficient conditions.  

PubMed

Boron is an essential micronutrient for higher plants. Boron deficiency is an important agricultural issue because it results in loss of yield quality and/or quantity in cereals and other crops. To understand boron transport mechanisms in cereals, we characterized OsNIP3;1, a member of the major intrinsic protein family in rice (Oryza sativa L.), because OsNIP3;1 is the most similar rice gene to the Arabidopsis thaliana boric acid channel genes AtNIP5;1 and AtNIP6;1. Yeast cells expressing OsNIP3;1 imported more boric acid than control cells. GFP-tagged OsNIP3;1 expressed in tobacco BY2 cells was localized to the plasma membrane. The accumulation of OsNIP3;1 transcript increased fivefold in roots within 6 h of the onset of boron starvation, but not in shoots. Promoter-GUS analysis suggested that OsNIP3;1 is expressed mainly in exodermal cells and steles in roots, as well as in cells around the vascular bundles in leaf sheaths and pericycle cells around the xylem in leaf blades. The growth of OsNIP3;1 RNAi plants was impaired under boron limitation. These results indicate that OsNIP3;1 functions as a boric acid channel, and is required for acclimation to boron limitation. Boron distribution among shoot tissues was altered in OsNIP3;1 knockdown plants, especially under boron-deficient conditions. This result demonstrates that OsNIP3;1 regulates boron distribution among shoot tissues, and that the correct boron distribution is crucial for plant growth. PMID:24654769

Hanaoka, Hideki; Uraguchi, Shimpei; Takano, Junpei; Tanaka, Mayuki; Fujiwara, Toru

2014-06-01

27

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

28

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

29

Investigation of boron distribution in a TiAl-based alloy using particle-tracking  

SciTech Connect

One of the key shortcomings of current TiAl intermetallic alloy is the inverse relationship between tensile properties and fracture/creep resistance. TiAl-based alloys with a fully lamellar structure generally display`s high fracture toughness and creep resistance, but poor ductility. Inversely, material with a duplex microstructure has very good ductility, but poor fracture toughness and creep resistance. Research efforts have focused on overcoming this deficiency. Now that it is widely accepted that the poor ductility of lamellar structures originates from the large grain size, refining the lamellar structure of TiAl-based alloys presents itself as a feasible solution. The question remains as to how to accomplish this goal. Microalloying is considered one approach for refining the fully lamellar structure. The present authors have reported that the addition of boron can effectively refine the grain size of fully lamellar structure. However, the distribution of boron in TiAl alloys and the mechanism in boron that suppresses grain growth are not yet clear. In the present paper, the distribution of boron in a Ti-rich TiAl-based alloy, as a function of the bulk boron content, annealing temperature, and thermomechanical process, is analyzed using a Particle-Tracking Autoradiography (PTA) technique.

Pu, Z.; Wu, K.H. [Florida International Univ., Miami, FL (United States)] [Florida International Univ., Miami, FL (United States)

1996-01-01

30

Concentric shelled and plate-like graphitic boron nitride nanoparticles produced by CO 2 laser pyrolysis  

NASA Astrophysics Data System (ADS)

The morphology of graphitic boron nitride nanometric particles produced from the reaction between ammonia and borontrichloride heated by a CO 2 laser is investigated by high resolution electron microscopy. A variety of roughly spherical particles are revealed, consisting of concentric graphitic shells and ranging in size from 20 to more than 100 nm and in shape from hollow to filled-to-the-center. This onion-like configuration is very similar to that observed in carbon materials. Another morphology made of stackings of a few perfectly flat graphitic sheets (10 to 50 layers, 50 nm in length) is developed after heat treatment.

Boulanger, L.; Andriot, B.; Cauchetier, M.; Willaime, F.

1995-03-01

31

Helium-3 and boron-10 concentration and depth measurements in alloys and semiconductors using NDP  

NASA Astrophysics Data System (ADS)

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 the residual energy of the charged particles or the recoil atoms. The NDP technique has became an increasingly important method to measure depth profiles of 3He and 10B in alloys and semiconductor materials. A permanent NDP facility has been installed on the tangential beam port of the University of Texas (UT) TRIGA Mark-II research reactor. One of the standard applications of the UT-NDP facility involves the determination of boron profiles of borophosphosilicate glass (BPSG) samples. NDP is also being used in combination with electron microscopy measurements to determine radiation damage and microstructural changes in stainless steel samples. This is done to study the long-term effects of high-dose alpha irradiation for weapons grade plutonium encapsulation. Measurements of implanted boron-10 concentration and depth profiles of semiconductor materials in order to calibrate commercial implanters is another application at the UT-NDP facility. The concentration and depth profiles measured with NDP and SIMS are compared with reported data given by various vendors or different implanters in order to verify implant quality of semiconductor wafers. The results of the measurements and other possible applications of NDP are presented.

Ünlü, Kenan; Saglam, Mehmet; Wehring, Bernard W.

1999-02-01

32

Isotopic phonon effects in ?-rhombohedral boron—non-statistical isotope distribution  

NASA Astrophysics Data System (ADS)

On the basis of the spectra of IR- and Raman-active phonons, the isotopic phonon effects in ?-rhombohedral boron are analysed for polycrystalline 10B- and 11B-enriched samples of different origin and high-purity natB single crystals. Intra- and inter-icosahedral B-B vibrations are harmonic, hence meeting the virtual crystal approximation (VCA) requirements. Deviations from the phonon shift expected according to the VCA are attributed to the anharmonic share of the lattice vibrations. In the case of icosahedral vibrations, the agreement with calculations on ?-rhombohedral boron by Shirai and Katayama-Yoshida is quite satisfactory. Phonon shifts due to isotopic disorder in natB are separated and determined. Some phonon frequencies are sensitive to impurities. The isotopic phonon effects yield valuable specific information on the nature of the different phonon modes. The occupation of regular boron sites by isotopes deviates significantly from the random distribution.

Werheit, H.; Filipov, V.; Kuhlmann, U.; Schwarz, U.; Armbrüster, M.; Antadze, M.

2012-05-01

33

Influence of Boron Concentration on the Surface Properties of TEOS-PDMS Hybrid Materials  

Microsoft Academic Search

The influence of the concentration of triethylborate (TEB) on the surface properties of hybrid materials prepared from tetraethylortosilicate (TEOS) and polydimethylsiloxane (PDMS) has been studied. TEB concentration has been varied between 0 and 30 wt.% respect to the total amount of alkoxyde whereas PDMS concentration has been set at 40 wt.% in all the hybrid samples. Pore size distributions (PSDs),

R. Peña-Alonso; A. Tamayo; F. Rubio; J. Rubio

2005-01-01

34

Calculated responses to a thermal neutron beam for hamster and HeLa cells containing boron-10 at different concentrations  

Microsoft Academic Search

Cells were irradiated by a thermal neutron beam from a reactor. The survival curves were calculated according to the Katz and Sharma theory of track structure for heavy charged particles (1971). The thickness of cell specimens irradiated was taken to be 0.02 cm to enable the first collision dose to be used. The boron-10 concentrations were 0, 2, 5, 10,

T. Saigusa; Y. Ueno

1978-01-01

35

Boron distribution in silicon after multiple pulse excimer laser annealing  

SciTech Connect

We have studied B redistribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted with energies of 1 and 10 keV and doses of 1x10{sup 14} and 1x10{sup 15} cm{sup -2}. ELA with the number of pulses from 1 to 100 was performed at room temperature and 450 deg. C in vacuum. Irrespective of the implantation parameters and the ELA conditions used, a pile-up in the B concentration is observed near the maximum melting depth after ten pulses of ELA. Moreover, a detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. Besides, an increase in the carrier concentration is observed at the maximum melt depth, suggesting electrical activity of the accumulated B. Formation of Si-B complexes and vacancy accumulation during multiple ELA are discussed as possible mechanisms for the B build-up.

Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L. [Department of Physics, Physical Electronics, University of Oslo, P.O. Box 1048, Blindern, N-0316 Oslo (Norway); Royal Institute of Technology, Lab of Materials and Semiconductor Physics, P.O. Box Electrum 229, SE-164 40 Kista (Sweden); CNR-IMM, Stradale Primosole 50, 95121 Catania (Italy); CNR-IFN, Via Cineto Romano 42, 00156 Rome (Italy)

2005-08-22

36

Chemical mechanical polishing of PSG and BPSG dielectric films: the effect of phosphorus and boron concentration  

Microsoft Academic Search

Chemical-mechanical polishing of blanket and patterned oxide films doped with phosphorus and boron has been studied. FTIR was used to characterize the film microstructure. Experimental results show that an increase of phosphorus level promoted the polish rate of PSG film. We also found that increasing the boron content enhanced the polish rate of BPSG films although phosphorus contents is decreased.

Chi-Wen Liu; Bau-Tong Dai; Ching-Fa Yeh

1995-01-01

37

Self-compensation property of ?-rhombohedral boron doped with high Li concentration  

NASA Astrophysics Data System (ADS)

A high concentration of Li (up to LiB5.8; 18 Li/cell) was doped into ?-rhombohedral boron (?-B), which has a crystalline structure built up from B12 icosahedral clusters, by sealing the raw materials in a stainless-steel tube. The relation between the structure and the electronic properties was clarified and a self-compensation property of Li- or Mg-doped ?-B was discussed. The Li concentration was analyzed by atomic absorption spectrometry. The changes in the structure and the electronic properties were investigated by X-ray diffraction using the Rietveld method and by electrical conductivity measurements, respectively. Li occupies the A1, D, E and F sites, and the occupancies of the B sites (B13, B16 and B4) decrease with increasing Li doping. In Li- or Mg-doped ?-B, electron doping is compensated by the removal of interstitial B atoms at the B16 site and by the generation of vacancies at the B13 and B4 sites. There have been no reports of self-compensation in other crystalline elemental semiconductors.

Hyodo, H.; Nezu, A.; Soga, K.; Kimura, K.

2012-11-01

38

Concentration Distributions during Pulse Jet Mixing  

SciTech Connect

Obtaining real-time, in situ slurry concentration measurements during unsteady mixing can provide increased understanding into mixer performance. During recent tests an ultrasonic attenuation sensor was inserted into a mixing vessel to measure the slurry concentration during unsteady mixing in real time during pulse jet mixer operation. These pulse jet mixing tests to suspend noncohesive solids in Newtonian liquid were conducted at three geometric scales. To understand the solids suspension process and resulting solids distribution, the concentration of solids in the cloud was measured at various elevations and radial positions during the pulse jet mixer cycle. In the largest scale vessel, concentration profiles were measured at three radial locations: r = 0, 0.5 and 0.9 R where R is the vessel radius. These radial concentration data are being analyzed to provide a model for predicting concentration as a function of elevation. This paper describes pulse jet mixer operation, provides a description of the concentration probe, and presents transient concentration data obtained at three radial positions: in the vessel center (O R), midway between the center and the wall (0.5 R) and near the vessel wall (0.9 R) through out the pulse to provide insight into pulse jet mixer performance.

Bamberger, Judith A.; Meyer, Perry A.

2010-08-05

39

Effect of carbon species on the reduction and melting behavior of boron-bearing iron concentrate/carbon composite pellets  

NASA Astrophysics Data System (ADS)

Iron nugget and boron-rich slag can be obtained in a short time through high-temperature reduction of boronbearing iron concentrate by carbonaceous material, both of which are agglomerated together as a carbon composite pellet. This is a novel flow sheet for the comprehensive utilization of boron-bearing iron concentrate to produce a new kind of man-made boron ore. The effect of reducing agent species (i.e., carbon species) on the reduction and melting process of the composite pellet was investigated at a laboratory scale in the present work. The results show that, the reduction rate of the composite pellet increases from bituminite, anthracite, to coke at temperatures ranging from 950 to 1300°C. Reduction temperature has an important effect on the microstructure of reduced pellets. Carbon species also affects the behavior of reduced metallic iron particles. The anthracite-bearing composite pellet melts faster than the bituminitebearing composite pellet, and the coke-bearing composite pellet cannot melt due to the high fusion point of coke ash. With anthracite as the reducing agent, the recovery rates of iron and boron are 96.5% and 95.7%, respectively. This work can help us get a further understanding of the new process mechanism.

Wang, Guang; Ding, Yin-gui; Wang, Jing-song; She, Xue-feng; Xue, Qing-guo

2013-06-01

40

Experimental boron neutron capture therapy for melanoma: Systemic delivery of boron to melanotic and amelanotic melanoma  

SciTech Connect

The boron-containing melanin precursor analogue p-boronophenylalanine (BPA) has previously been shown to selectively deliver boron to pigmented murine melanomas when administered in a single intragastric dose. If boron neutron capture therapy is to become a clinically useful method of radiation therapy for human malignant melanoma, the boron carrier must be capable of delivering useful amounts of boron to remote tumor sites (metastases) and to poorly pigmented melanomas. The authors have now determined the ability of BPA to accumulate in several nonpigmented melanoma models including human melanoma xenografts in nude mice. The absolute amount of boron in the nonpigmented melanomas was about 50% of the observed in the pigmented counterparts but was still selectively concentrated in the tumor relative to normal tissues in amounts sufficient for effective neutron capture therapy. Single intragastric doses of BPA resulted in selective localization of boron in the amelanotic Greene melanoma carried in the anterior chamber of the rabbit eye and in a pigmented murine melanoma growing in the lungs. The ratio of the boron concentration in these tumors to the boron concentration in the immediately adjacent normal tissue was in the range of 3:1 to 4:1. These distribution studies support the proposal that boron neutron capture therapy may be useful as a regional therapy for malignant melanoma.

Coderre, J.A.; Glass, J.D.; Micca, P.; Greenberg, D. (Brookhaven National Lab., Upton, NY (United States)); Packer, S. (Brookhaven National Lab., Upton, NY (United States) North Shore University Hospital Manhasset, NY (United States))

1990-01-01

41

A preliminary investigation on boron and metal concentrations of the main drainage channel in Konya-Turkey.  

PubMed

In this work, the wastewaters and sediments of the main drainage channel in Konya (Turkey) were collected from three different sampling points and analyzed for metals, including iron, chromium, copper, lead, zinc and nickel by using inductively coupled plasma-atomic emission spectrometry (ICP-AES). It was found that for all sampling points sediment samples show a decrease in concentrations in the order Fe > Zn > Cr > Ni > Cu > Pb. For all sampling points, heavy metal concentrations in wastewater did not exceed the maximum admissible discharge levels regulated by the Institute of Turkish Standards. However, it was found that boron concentration of wastewaters exceed the safe level for irrigation of farmland. PMID:17203608

Aydin, M E; Yildiz, S; Tor, A

2006-11-01

42

Trace element concentration and distribution in ivory  

NASA Astrophysics Data System (ADS)

The trace element content and distribution in ivory from elephants and hippopotami were measured for both natural elements and elements present due to pollution. The National Accelerator Centre Nuclear Microprobe was used to investigate trace elements heavier than Ca, and distributions of these trace elements were measured over small areas (ca. 1 mm 2), using the Dynamic Analysis imaging method in the GeoPIXE software package. Quantitativity of elemental maps was checked by complementary point analyses in the same area as where the elemental maps were taken from and found to be accurate to within around 10%. The possibility of locating ivory on the basis of the trace element concentrations, determined by the environment in which these animals live, was demonstrated by using correspondence analysis.

Prozesky, V. M.; Raubenheimer, E. J.; Van Heerden, W. F. P.; Grotepass, W. P.; Przybylowicz, W. J.; Pineda, C. A.; Swart, R.

1995-09-01

43

Studies on distribution of element contents in transient layer at interface between boron-doped diamond film electrode and tantalum substrate  

NASA Astrophysics Data System (ADS)

The boron-doped diamond film (BDD) grown on tantalum (Ta) substrate as an electrode (BDD/Ta) was prepared by hot filament chemical vapor deposition method. The experimental results demonstrated that our BDD/Ta had high current efficiency, strong ability to degrade wastewater, good corrosion stability and long lifetime. These excellent characteristics of BDD/Ta have been explained in terms of Rutherford backscattering (RBS) experiments. RBS investigation revealed that the continuous transient layer at the interface between boron-doped diamond film and Ta-substrate was formed and the microstructure of the continuous transient layer given by the continuous distribution of all element contents at the interface was obtained. The thicknesses of boron-doped diamond film and the continuous transient layer were about equal to 8000 × 10 15 atoms/cm 2 and 5800 × 10 15 atoms/cm 2, respectively. The formation of the continuous transient layer at the interface can eliminate the mismatch of thermal expansion coefficients (TEC) at the interface and only lead to the slow change of TEC because of the continuous distribution of element contents of the film and substrate in the transient layer at the interface. Thus, there is no residual stress to concentrate on the interface and the stress-corrosion delamination of the film disappears. Therefore, the corrosion stability and lifetime of BDD/Ta increase and last well, that have been verified by X-ray diffraction (XRD) experiments.

Liang, Jiachang; Gao, Chengyao; Zhang, Liping; Jiang, Lihui; Yang, Zhengquan; Wang, Zhiping; Ji, Chaohui; Le, Xiaoyun; Rong, Cuihua; Zhang, Jian

2011-05-01

44

Quantitative SIMS measurement of high concentration of boron in silicon (up to 20 at.%) using an isotopic comparative method  

NASA Astrophysics Data System (ADS)

Highly boron doped (up to 20 at.%) silicon samples have been analysed by SIMS with the aim of quantifying the boron concentration in a range where the dilute regime may not be valid any more. An original method is used based on the simultaneous analysis of two different isotopes, namely B10 and B11, in order that the known concentration of the first isotope (initially present with a far lower, constant concentration) is the basis of the quantification of the concentration of the second, present with a very high dose. Argon and oxygen beams have been used and conclusions are drawn about the presence of matrix effects in the case of the analysis of highly doped samples. It appears that only the use of a 8 keV O2+ beam leads to a significant matrix effect, whereas it is nearly absent in the case of an analysis under 8 keV Ar + beam. The proposed method may be applied to any element showing at least two isotopes in any binary alloys under any primary beam.

Dubois, Christiane; Prudon, Gilles; Gautier, Brice; Dupuy, Jean-Claude

2008-12-01

45

Use of novel methods for the investigation of the boron distribution in CVD diamond[Chemical Vapor Deposition  

SciTech Connect

Previous work on boron-doped CVD diamond films has indicated inhomogeneity of boron distribution. A variety of methods has been used to investigate the nature of these inhomogeneities. The methods used include electron irradiation in a transmission electron microscope followed by helium cooled microscopic photoluminescence studies, imaging SIMS and micro-Raman imaging. A number of sharp B-related photoluminescence lines has been identified and found to vary considerably from one location to another. This evidence of inhomogeneity is confirmed by B mapping using imaging SIMS and micro-Raman microscopy.

Steeds, J.W.; Gilmore, A.; Charles, S.; Heard, P.; Howarth, B.; Butler, J.E.

1999-11-12

46

Electron Density Distributions in Derivative Crystals of alpha-Rhombohedral Boron  

Microsoft Academic Search

Boron carbide (B12C3) and boron phosphide (B12P2) have the similar structures to alpha-rhombohedral boron (alpha-B12) and are considered to be derivative crystals of it. The peculiar bonds in these two derivative crystals are visualized by MEM\\/Rietveld analysis, which involves a combination of the maximum entropy method (MEM) and Rietveld refinement for powder X-ray diffraction (XRD) data. The distinctive bending of

Shizuka Hosoi; Hongki Kim; Tomohiro Nagata; Kazuhiro Kirihara; Kohei Soga; Kaoru Kimura; Kenichi Kato; Masaki Takata

2007-01-01

47

On processes controlling the distribution and fluxes of boron in natural waters and air along transects across the South Island of New Zealand  

Microsoft Academic Search

The concentrations of boron were measured in rain, air and soil water along transects across the Southern Alps, New Zealand, during southern autumn and early winter 1999. Estimates of wet deposition, dry deposition, and flux of boron leaving the soil in soil water are presented. At the Main Divide of the Southern Alps, strong and constant orographic effects on rain-bearing

Reimer Herrmann

2001-01-01

48

Tourmaline in the 3.7-3.8 Ga Isua Supracrustal Belt, West Greenland - A window to Boron Concentrations in the Eoarchean Eon  

NASA Astrophysics Data System (ADS)

The distribution and mineralogical context of trace elements in Earth's oldest rocks provide insights on Earth's accretion, differentiation, and primordial evolution. One example is boron, which is highly concentrated in Earth's crust and oceans relative to primitive mantle, and, thus the amount of boron on Earth's surface should increase with increasing volume of crust. The earliest B mineral reported in the geological record is metamorphic tourmaline in the Isua Supracrustal Belt, where its abundance belies the notion of there being less boron in the Eoarchean than in more recent time. Chaussidon & Appel (1997, Chem. Geol., 136, 171-180) reported ?11B = --17.3 to --25.0‰ in tourmaline in Isua metachert ("conglomerate"), and ?11B = --12.6 to +5.8 ‰ on tourmaline in Isua metamorphosed mafic volcaniclastics. The large range in the latter rocks was attributed to fractionation during hydrothermal reworking, whereas the more negative values in the metacherts suggested metamorphic tourmaline formed from breakdown of clays with an average ?11B calculated to be about -8 × 7‰ deposited in an ocean having ?11B = +27×11‰, compared to +40 ‰ today, consistent with ?11B = +28‰ calculated from the Chaussidon & Albarède (1992, EPSL, 108, 229-241) model relating increase in sea-water ?11B to proportion of B extracted from Earth's mantle into the oceans and crust. This estimate of Eoarchean seawater ?11B is consistent with fractionation associated with illitization of smectite formed in a marine environment (estimated to be about --35‰) and with crystallization of metamorphic tourmaline from intergranular fluid having the same ?11B as the host metachert (another --2‰ at 500 °C based on tourmaline-water fractionation from Meyer et al. 2008, Contrib. Mineral. Petrol., 156, 259-267). However, this scenario does not adequately explain three rock types in the Isua supracrustals: (1) a tourmaline-quartz lens with ~50% modal tourmaline; (2) a dolomite-tourmaline lens with ~20% modal tourmaline containing accessory chromite, chalcopyrite and gersdorffite, (Ni,Co,Fe)AsS; (3) 'green-mica' schist containing Cr- and Ba-bearing muscovite and accessory tourmaline, sphalerite, chalcopyrite, galena, pentlandite, arsenopyrite and gersdorffite. These sulfides suggest that hydrothermal fluid associated with volcanism introduced B, As and Pb into sedimentary rocks together with Cr, Co and Ni remobilized from associated ultramafic rocks. Crystallization of tourmaline in (1) with ?11B =--22‰ (Swihart & Moore, 1989, Geochim. Cosmochim. Acta, 53, 911-916) implies ?11B of --17 ‰ to--19 ‰ in the hydrothermal fluid from which it crystallized (assuming tourmaline-water fractionation at 200-350 °C based on Meyer et al. 2008). These fluid ?11B suggest a continental source of the boron, since ?11B of continental detritus averages -10 × 5‰, i.e., more negative (lighter) than oceanic crust (Leeman & Sisson, 1996, Rev. Mineral., 33, 645-707). As the tourmaline-bearing rocks are part of the younger (ca. 3700 Ma) of two terranes in the Isua supracrustal belt (Nutman & Friend, 2009, Precamb. Res., 172, 189-211), we suggest that boron isotopic composition and abundance resulted from recycling of boron in supracrustal rocks of the older (ca. 3800 Ma) terrane and its remobilization in a volcanic system prior to precipitation as tourmaline in rocks of the younger terrane.

Grew, E. S.; Dymek, R. F.; De Hoog, J. C.; Harley, S. L.; Hazen, R. M.; Yates, M. G.

2013-12-01

49

Developmental effects of boric acid in rats related to maternal blood boron concentrations  

Microsoft Academic Search

Timed-mated Sprague-Dawley rats (60\\/group) were exposed to boric acid (BA) from gestational days (gd) 0 to 20. BA added to\\u000a the diet (0, 0.025, 0.050, 0.075, 0.1, or 0.2%) yielded boron (B) intakes of <0.35 (control), 3, 6,10,13, or 25 mg B\\/kg body\\u000a wt\\/d. Approximately one-half of the dams\\/group were terminated on gd 20, maternal whole blood collected and frozen,

Catherine J. Price; Philip L. Strong; F. Jay Murray; Margaret M. Goldberg

1998-01-01

50

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

51

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

52

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

53

Concentration Distributions during Pulse Jet Mixing  

Microsoft Academic Search

Obtaining real-time, in situ slurry concentration measurements during unsteady mixing can provide increased understanding into mixer performance. During recent tests an ultrasonic attenuation sensor was inserted into a mixing vessel to measure the slurry concentration during unsteady mixing in real time during pulse jet mixer operation. These pulse jet mixing tests to suspend noncohesive solids in Newtonian liquid were conducted

Judith A. Bamberger; Perry A. Meyer

2010-01-01

54

Distribution of Boron Between Silicon and CaO-MgO-Al2O3-SiO2 Slags  

NASA Astrophysics Data System (ADS)

Production of solar-grade silicon through metallurgical refining methods can be less expensive than current production methods both in terms of energy use and capital cost. Slag refining is a potential metallurgical refining method for removal of boron from silicon. The distribution of boron between silicon and binary CaO-SiO2 and MgO-SiO2 slags, and between silicon and ternary CaO-MgO-SiO2 and CaO-Al2O3-SiO2 slags has been investigated in this work at 1873 K (1600 °C). The distribution coefficient of boron has been found to be between 2 and 2.5 in the binary CaO-SiO2 and MgO-SiO2 systems. It has also been found to be in the same range across the entire CaO-MgO-SiO2 system. In these systems the distribution coefficient is unaffected by slag composition. The distribution coefficient has been found to decrease with increasing Al2O3 content in the slag in the ternary CaO-Al2O3-SiO2 system.

Jakobsson, Lars Klemet; Tangstad, Merete

2014-05-01

55

Concentration distribution of sediment mixtures in open-channel flow  

Microsoft Academic Search

Rouse's equation and some of the recently developed equations for concentration distribution in the case of flow in an open channel have been checked for their accuracy with the help of data ofsuspended-sediment concentration-distribution of the individual fractions in a mixture. The agreement between predictions and measurements is not found to be satisfactory. It is found that the sediment distribution

B. R. Samaga; K. G. Ranga Raju; R. J. Garde

1985-01-01

56

Electrochemical destruction of N-nitrosodimethylamine in reverse osmosis concentrates using Boron-doped diamond film electrodes.  

PubMed

Boron-doped diamond (BDD) film electrodes were use to electrochemically destroy N-nitrosodimethylamine (NDMA) in reverse osmosis (RO) concentrates. Batch experiments were conducted ito investigate the effects of dissolved organic carbon (DOC), chloride (Cl(-)), bicarbonate (HCO(3-) and hardness on rates of NDMA destruction via both oxidation and reduction. Experimental results showed that NDMA oxidation rates were not affected by DOC, Cl(-), or HCO(3-) at concentrations present in RO concentrates. However, hydroxyl radical scavenging at 100 mM concentrations of HCO(3-) and Cl(-) shifted the reaction mechanism of NDMA oxidation from hydroxyl radical mediated to direct electron transfer oxidation. In the 100 mM Cl(-) electrolyte experimental evidence suggests that the in situ production of ClO(3)(.)also contributes to NDMA oxidation. Density functional theory calculations support a reaction mechanism between ClO(3)(.) and NDMA, with an activation barrier of 7.2 kJ/mol. Flow-through experiments with RO concentrate yielded surface area normalized first-order rate constants for NDMA (40.6 +/- 3.7 L/m(2) h) and DOC (as C) (38.3 +/- 2.2 L/m(2) h) removal that were mass transfer limited at a 2 mA/cm(2) current density. This research shows that electrochemical oxidation using BDD electrodes has an advantage over other advanced oxidation processes, as organics were readily oxidized in the presence of high HCO(3-) concentrations. PMID:20441141

Chaplin, Brian P; Schrader, Glenn; Farrell, James

2010-06-01

57

Sources and atmospheric distribution of particulate and gas-phase boron  

NASA Astrophysics Data System (ADS)

Atmospheric samples were collected during warm and cold weather conditions at continental, coastal and marine sites. Source sampling was performed at a coal-fired power plant and several volcanic sites. Atmospheric gas-phase and particulate boron concentrations were determined by neutron capture prompt-gamma activation analysis and compared to measurements from other studies. Rain and snow samples collected at one continental site were analysed for soluble and insoluble B. Volcanic deposit and ash samples were also analysed for B. The tropospheric burdens for particulate and gas-phase B were estimated to be 0.6 × 10 10 g and (6-11) × 10 10 g, respectively, with the latter about a factor of 3 lower than previous estimates. Global anthropogenic particulate and gas-phase B source estimates were consistent with previous estimates, and natural particulate and gas-phase B source estimates agreed reasonably well with previously reported upper limits. About 65-85 % of total B source strength can be attributed to the oceans, and 8-20% to coal, agricultural, fuelwood and refuse burning. Volcanism may contribute 6-15% of the total, but accurate source estimates are difficult. Total global B removal from the atmosphere by wet and dry deposition was estimated to be (530-700) × 10 10 g yr -1, a factor of 2 lower than previously reported but in fairly good agreement with the global total B source estimate of (200-530) × 10 10 g yr -1.

Anderson, David L.; Kitto, Michael E.; McCarthy, Lauren; Zoller, William H.

58

A benchmark analysis of radiation flux distribution for Boron Neutron Capture Therapy of canine brain tumors  

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 work describes 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 tissues of interest. The resulting geometry and tissue composition data were then used to construct a detailed heterogeneous calculational model of the Labrador Retriever head. Calculations of three-dimensional radiation flux distributions pertinent to BNCT were performed for the 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 the 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.

1992-02-01

59

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

60

Boron in the marine atmosphere  

NASA Astrophysics Data System (ADS)

Atmospheric boron was simultaneously separated into gaseous and particulate components for the first time by passing air through a simple impregnated filter sampling system. A Nuclepore filter collected particular boron and preceded KOH impregnated Whatman 41 filters for gaseous boron collection. Boron was determined by visible spectrophotometry. The method was developed to allow daily measurements of atmospheric boron. The results show that boron exists in the atmosphere primarily in the gas phase. Gaseous boron concentrations collected at several sites in the Northern Hemisphere ranged from 1-233 ng/cu m while particulate boron ranged from 0.02-8 ng/cu m. A four month series of daily samples collected at Narragansett, R.I. revealed gaseous boron variations to exist on a time scale of several days. Estimate of inputs of boron to the troposphere reveal that the ocean and vulcanism are the major natural sources, dominating anthropogenic sources, such as coal combustion, by a factor of approx 10.

Fogg, T. R.

61

Ligands of boron in Pisum sativum nodules are involved in regulation of oxygen concentration and rhizobial infection.  

PubMed

Boron (B) is an essential nutrient for N(2)-fixing legume-rhizobia symbioses, and the capacity of borate ions to bind and stabilize biomolecules is the basis of any B function. We used a borate-binding-specific resin and immunostaining techniques to identify B ligands important for the development of Pisum sativum-Rhizobium leguminosarum 3841 symbiotic nodules. arabinogalactan-extensin (AGPE), recognized by MAC 265 antibody, appeared heavily bound to the resin in extracts derived from B-sufficient, but not from B-deficient nodules. MAC 265 stained the infection threads and the extracellular matrix of cortical cells involved in the oxygen diffusion barrier. In B-deprived nodules, immunolocalization of MAC 265 antigens was significantly reduced. Leghaemoglobin (Lb) concentration largely decreased in B-deficient nodules. The absence of MAC 203 antigens in B-deficient nodules suggests a high internal oxygen concentration, as this antibody detects an epitope on the lipopolysaccharide (LPS) of bacteroids typically expressed in micro-aerobically grown R. leguminosarum 3841. However, B-deprived nodules did not accumulate oxidized lipids and proteins, and revealed a decrease in the activity of the major antioxidant enzyme ascorbate peroxidase (APX). Therefore, B deficiency reduced the stability of nodule macromolecules important for rhizobial infection, and for regulation of oxygen concentration, resulting in non-functional nodules, but did not appear to induce oxidative damage in low-B nodules. PMID:20132519

Reguera, María; Wimmer, Monika; Bustos, Pilar; Goldbach, Heiner E; Bolaños, Luis; Bonilla, Ildefonso

2010-06-01

62

Grain growth mechanism in boron doped polycrystalline silicon  

NASA Astrophysics Data System (ADS)

The mechanism of grain growth in heavily boron doped polycrystalline silicon has been studied for various boron concentrations, annealing times and annealing temperatures by proposing a kinetic model based on thermodynamical concepts. A computer simulation technique has been used to determine the grain boundary self-diffusion of silicon atoms. Our theoretical predictions have been compared with available experimental reports. This model has been extended to evaluate the grain size distribution in boron doped polysilicon for various dopant concentrations, annealing times and temperatures. The results are discussed in detail.

Kalainathan, S.; Dhanasekaran, R.; Ramasamy, P.

1990-10-01

63

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

64

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

65

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

66

Concentration of cesium and francium by distribution and adsorption chromatography  

Microsoft Academic Search

Methods were developed for concentrating cesium and francium from nuclear reaction products using distribution and adsorption\\u000a chromatography. The feasibility of obtaining concentrated solutions of cesium and francium, both on carriers and carrier-free,\\u000a has been demonstrated.

N. S. Maltseva; K. A. Gavrilov

1972-01-01

67

Distributed-fibre-optic methane gas concentration detection  

Microsoft Academic Search

A novel method for detecting methane gas concentration distribution is proposed, based on the characteristics of supported catalytic sensors (SCS) and optical fibers. The feasibility, performance, and applications prospects of this system are also discussed. After analyzing the operating procedure of SCS theoretically, the linear relationship between methane concentration and its working temperature was established. The response of temperature to

Yi-Wei Shi; Yao-Cai Wang; Hong-Tao Jiang; Cheng-Shan Yao; Zhen-Chun Wu

1991-01-01

68

Trace element concentration distributions in breast, lung and colon tissues  

NASA Astrophysics Data System (ADS)

The concentrations of Fe, Cu, Zn and Se in cancerous and benign tissues of breast, lung and intestine (colon) have been determined. In the cases when the element concentration has not been determined in all samples the Kaplan-Meier method has been used for the reconstruction of the original concentration distributions and estimation of the true mean concentrations and medians. Finally, the log-rank test has been applied to compare the elemental concentration distributions between cancerous and benign tissues of the same organ, between cancerous tissues and between benign tissues taken from different organs. Comparing benign and malignant neoplastic tissues, statistically significant differences have been found between Fe and Se concentration distributions of breast as well as for Cu and Zn in the case of lung tissues and in the case of colon tissues for Zn. The concentrations of all elements have been found to be statistically different in cancer tissues as well as in benign ones when comparing the different organs, i.e. groups 'breast-colon' and 'breast-lung'. Concentrations of Fe and Cu have been found to be statistically different in lung and colon cancerous tissues. For benign tissues of lung and colon a statistically significant difference has been found only for Zn.

Majewska, Urszula; Banas, Dariusz; Braziewicz, Janusz; Gózdz, Stanislaw; Kubala-Kukus, Aldona; Kucharzewski, Marek

2007-07-01

69

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

70

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

SciTech Connect

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, {alpha}) 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 {sup 10}B/g blood.

Zasneda, Sabriani; Widita, Rena [Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung, 40132 (Indonesia)

2010-06-22

71

Pre-irradiation spatial distribution and stability of boride particles in rapidly solidified boron-doped stainless steels  

SciTech Connect

The time temperature behavior of boride particles has been studied in rapidly solidified ultra low carbon and nitrogen modified 316 stainless steel with 0.088% boron and 0.45% zirconium. The results show that the as-splat-cooled specimens exhibit precipitates at the grain boundaries and triple junctions. For temperatures up to about 750/sup 0/C no significant microstructural changes occur for short heat treatment times. In the temperature range of 750 to 950/sup 0/C, however, particles typically 100 to 500 A in diameter containing Zr and B are formed within the grains. Higher temperatures enhance the formation of such particles and give rise to particle networks. The results show that a fine and uniform distribution of the boride particles almost exclusively within the grains can be achieved if proper annealing conditions are chosen. This type of distribution is an important requirement for the homogeneous production of helium during neutron irradiation in fast reactors.

Kanani, N.; Arnberg, L.; Harling, O.K.

1981-01-01

72

Pre-irradiation spatial distribution and stability of boride particles in rapidly solidified boron doped stainless steels  

NASA Astrophysics Data System (ADS)

The time temperature behavior of boride particles has been studied in rapidly solidified ultra low carbon and nitrogen modified 316 stainless steel with 0.088% boron and 0.45% zirconium. The results show that the as-splat-cooled specimens exhibit precipitates at the grain boundaries and triple junctions. For temperatures up to about 750°C no significant microstructural changes occur for short heat treatment times. In the temperature range of 750-950°C, however, particles typically 100-500 Å in diameter containing Zr and B are formed within the grains. Higher temperatures enhance the formation of such particles and give rise to particle networks. The results show that a fine and uniform distribution of the boride particles almost exclusively within the grains can be achieved if proper annealing conditions are chosen. This type of distribution is an important requirement for the homogeneous production of helium during neutron irradiation in fast reactors.

Kanani, N.; Arnberg, L.; Harling, O. K.

73

Boron Neutron Capture Therapy for Cancer  

Microsoft Academic Search

Boron neutron capture therapy (BNCT) bring together two components that when kept separate have only minor effects on normal cells. The first component is a stable isotope of boron (boron 10) that can be concentrated in tumor cells. The second is a beam of low-energy neutrons that produces short-range radiation when absorbed, or captured, by the boron. The combination of

Rolf F. Barth; Albert H. Soloway; Ralph G. Fairchild

1990-01-01

74

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

75

An introduction to boron: history, sources, uses, and chemistry.  

PubMed Central

Following a brief overview of the terrestrial distribution of boron in rocks, soil, and water, the history of the discovery, early utilization, and geologic origin of borate minerals is summarized. Modern uses of borate-mineral concentrates, borax, boric acid, and other refined products include glass, fiberglass, washing products, alloys and metals, fertilizers, wood treatments, insecticides, and microbiocides. The chemistry of boron is reviewed from the point of view of its possible health effects. It is concluded that boron probably is complexed with hydroxylated species in biologic systems, and that inhibition and stimulation of enzyme and coenzymes are pivotal in its mode of action. Images Figure 1.

Woods, W G

1994-01-01

76

Estival Distribution of Dissolved Metal Concentrations in Liaodong Bay  

Microsoft Academic Search

Abstact  The temporal and spatial distributions of Cu, Pb, Zn, and Cd in surface water of the Liaodong Bay were studied based on samples\\u000a collected at 16 sites in June and August from 2001 to 2005. The temporal distribution showed decreasing trends. The concentrations\\u000a of dissolved metals in the Liaodong Bay were 4.34, 3.21, 31.54, and 0.995 ?g\\/L for Cu, Pb, Zn,

L. Wan; N. B. Wang; Q. B. Li; Z. C. Zhou; B. Sun; K. Xue; Z. Q. Ma; J. Tian; N. Du

2008-01-01

77

Kinetics of the formation of Fe 2B layers in gray cast iron: Effects of boron concentration and boride incubation time  

NASA Astrophysics Data System (ADS)

The growth kinetics of Fe 2B layers formed at the surface of gray cast iron were evaluated in this study. The pack-boriding process was applied to produce the Fe 2B phase at the material surface, and the variables included three temperatures (1173, 1223 and 1273 K) and four exposure times (2, 4, 6 and 8 h). Taking into account the growth fronts obtained at the surface of the material and the mass balance equation at the Fe 2B/substrate interface, the boron diffusion coefficient on the borided phase was estimated for the range of treatment temperatures. Likewise the parabolic growth constant, the instantaneous velocity of the Fe 2B/substrate interface, and the weight gain in the borided samples were established as a function of the parameters ?( t) and ?( C), which are related to the boride incubation time ( t0( T)) and boron concentration at the Fe 2B phase, respectively. Observation of the growth kinetics of the Fe 2B layers in gray cast irons suggest an optimum value of boron concentration that is in good agreement with the set of boriding experimental conditions used in this work.

Campos-Silva, I.; Ortiz-Domínguez, M.; Keddam, M.; López-Perrusquia, N.; Carmona-Vargas, A.; Elías-Espinosa, M.

2009-08-01

78

Boron recovery, application and economic significance: A review  

Microsoft Academic Search

Boron compounds are widely used raw materials in various industries. However, high boron concentration in aqueous systems may be harmful to both humans and plants. Many treatment technologies have shown wide limitations in the removal of boron from wastewater and boronic wastes due to the complex boron chemistry. Boron exists as boric acid at pH9.2. Recovery of boron is one

Ezerie Henry Ezechi; Mohamed Hasnain Isa; Shamsul Rahman Kutty; Nasiman B. Sapari

2011-01-01

79

Heavily boron-doped effect on the etch rates of single-crystal silicon in TMAH solutions  

Microsoft Academic Search

The purpose of this paper is to study the heavily boron-doped effect on the etch rates of boron-doped single-crystal silicon in different TMAH solutions. The boron atoms were heavily doped in single-crystal silicon by using diffusion process. We change the pre-deposition time and annealing time of diffusion process to form different concentration distributions. The samples were pre-deposited at 1100°C and

Yong-Yi Chen; Chung-Nan Chen; Wen-Chie Huang

2009-01-01

80

Distribution of boron and its forms in young “Newhall” navel orange (Citrus sinensis Osb.) plants grafted on two rootstocks in response to deficient and excessive boron  

Microsoft Academic Search

Boron (B) deficiency is widespread and serious in navel orange orchards in southern Jiangxi in China and has been considered an important soil constraint to citrus yield and quality. It has been observed that there was great variation in responses to different B supply levels between “Newhall” navel orange grafted on citrange and trifoliate orange. The aim of this work

Liu Guidong; Jiang Cuncang; Wang Yunhua

2011-01-01

81

Concentration distribution around a growing gas bubble in tissue.  

PubMed

This paper presents the concentration distribution around a growing nitrogen gas bubble in the blood and other tissues of divers who surface too quickly, when the ambient pressure through the decompression process is variable and constant. This effort is a modification of Sirinivasan et al. model (1999) [9]. The mathematical model is solved analytically to find the growth rate of a gas bubble in a tissue after decompression in the ambient pressure. Moreover, the concentration distribution around the growing bubble is introduced. The growth process is affected by ascent rate alpha (t), tissue diffusivity D(T), initial concentration difference DeltaC(0), surface tension sigma and void fraction varphi(0). PMID:20085775

Mohammadein, S A; Mohamed, K G

2010-05-01

82

Activated boron and its concentration profiles in heavily doped Si studied by soft x-ray photoelectron spectroscopy and Hall measurements  

SciTech Connect

The chemical bonding states of boron (B) in shallow P{sup +}/N junctions on Si substrates were studied by soft x-ray photoelectron spectroscopy (SXPES). This study revealed three chemical bonding states of B embedded in bulk Si. The concentration profiles of B were successfully determined by combining SXPES with step-by-step etching of Si substrates. The concentration profiles of B thus determined were in good agreement with those determined by secondary ion mass spectroscopy. The concentration profiles of holes were also determined by combining Hall measurements with the step-by-step etching of Si substrates. The concentration profiles of B having the lowest binding energy were found to agree well with the concentration profiles of holes. Therefore, B with the lowest binding energy can be assigned as activated B and those having the middle and highest binding energies can be attributed to deactivated B having chemical bonding states different from that of activated B.

Tsutsui, Kazuo; Watanabe, Masamitsu; Kakushima, Kuniyuki [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, J2-69, 4259 Nagatsuta, Midoriku, Yokohama 226-8502 (Japan); Matsuda, Toru; Maruizumi, Takuya; Nohira, Hiroshi [Musashi Institute of Technology, 1-28-1 Tamazutsumi, Setagaya, Tokyo 158-8557 (Japan); Jin, Cheng-Guo; Sasaki, Yuichiro; Mizuno, Bunji [Ultimate Junction Technologies Inc., 3-1-1, Yagumo-Nakamachi, Moriguchi, Osaka 570-8501 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute /SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5918 (Japan); Ahmet, Parhat; Hattori, Takeo; Iwai, Hiroshi [Frontier Research Center, Tokyo Institute of Technology, J2-68, 4259 Nagatsuta, Midoriku, Yokohama 226-8502 (Japan)

2008-11-01

83

Concentration distribution of methyl chloride in the atmosphere  

NASA Technical Reports Server (NTRS)

Electron capture gas chromatography techniques were used to obtain measurements of methyl chloride concentrations in the atmosphere, at latitudes ranging from about 65 N to 90 S. Most of the measurements were made over the Pacific Ocean. Average global concentrations within the boundary layer were found to be 815 plus or minus 25 pptv in 1977 and 755 plus or minus 37 pptv in 1978. Lower concentrations were observed above the boundary layer with average values of 629 plus or minus 23 pptv and 618 plus or minus 23 pptv in 1977 and 1978, respectively. Within 20 deg of the equator, the boundary layer concentrations were significantly higher than those above the boundary layer. The sources, the sinks, the budgets, and the latitudinal distributions of methyl chloride are discussed in the paper.

Rasmussen, R. A.; Rasmussen, L. E.; Khalil, M. A. K.; Dalluge, R. W.

1980-01-01

84

Elemental concentration distribution in human fingernails - A 3D study  

NASA Astrophysics Data System (ADS)

The verification of pathologies has normally been based on analysis of blood (serum and plasma), and physiological tissue. Recently, nails and in particular human fingernails have become an important medium for pathological studies, especially those of environmental origin. The analytical technique of PIXE has been used extensively in the analysis of industrial samples and human tissue specimens. The application of the analytical technique to nails has been mainly to bulk samples. In this study we use micro-PIXE and -RBS, as both complementary and supplementary, to determine the elemental concentration distribution of human fingernails of individuals. We report on the 3D quantitative elemental concentration distributions (QECDs) of various elements that include C, N and O as major elements (10-20%), P, S, Cl, K and Ca as minor elements (1-10%) and Fe, Mn, Zn, Ti, Na, Mg, Cu, Ni, Cr, Rb, Br, Sr and Se as trace elements (less than 1%). For PIXE and RBS the specimens were bombarded with a 3 MeV proton beam. To ascertain any correlations in the quantitative elemental concentration distributions, a linear traverse analysis was performed across the width of the nail. Elemental distribution correlations were also obtained.

Pineda-Vargas, C. A.; Mars, J. A.; Gihwala, D.

2012-02-01

85

Boron neutron capture therapy for malignant melanoma: An experimental approach  

SciTech Connect

Previous studies have shown that some thioamides, e.g., thiouracil, are incorporated as false precursors into melanin during its synthesis. If boronated analogs of the thioamides share this property, the melanin of melanotic melanomas offers a possibility for specific tumoural uptake and retention of boron as a basis for neutron capture therapy. We report on the synthesis of boronated 1H-1,2,4-triazole-3-thiol (B-TZT), boronated 5-carboxy-2-thiouracil (B-CTU), and boronated 5-diethylaminomethyl-2-thiouracil (B-DEAMTU) and the localization of these substances in melanotic melanomas transplanted to mice. The distribution in the mice was studied by boron neutron capture radiography. B-TZT and B-CTU showed the highest tumour:normal tissue concentration ratios, with tumour:liver ratios of about 4 and tumour:muscle ratios of about 14; B-DEAMTU showed corresponding ratios of 1.4 and 5, respectively. The absolute concentration of boron in the tumours, however, was more than three times higher in the mice injected with B-TZT, compared with B-CTU. The results suggest that B-TZT may be the most promising compound of the three tested with regard to possible therapy of melanotic melanomas.

Larsson, B.S.; Larsson, B.; Roberto, A. (Uppsala Univ. (Sweden))

1989-07-01

86

Relationship between apolipoprotein concentrations and HDL subclasses distribution.  

PubMed

Alterations in plasma apolipoproteins levels can influence the composition, content, and distribution of plasma lipoproteins that affect the risk of atherosclerosis. This study assessed the relationship between plasma apolipoproteins levels, mainly apoAI, and HDL subclass distribution. The contents of plasma HDL subclasses were determined by two-dimensional gel electrophoresis coupled with immunodetection in 545 Chinese subjects. Compared with a low apoAI group, the contents of all HDL subclasses increased significantly both in middle and high apoAI group, and the contents of large-sized HDL(2b) increased more significantly relative to those of small-sized prebeta(1)-HDL in a high apoAI group. When apoAI and HDL-C levels increased simultaneously, in comparison to a low apoAI along with HDL-C concentration group, a significant increase (116%) was shown in HDL2b but only a slight increase (26%) in prebeta1-HDL. In addition, Pearson correlation analysis revealed that apoAI levels were positively and significantly correlated with all HDL subclasses. Multiple liner regression demonstrated that the apoAI concentrations were the most powerful predictor for HDL subclass distribution. With the elevation of apoAI concentrations, the contents of all HDL subclasses increased successively and significantly, especially, an increase in large-sized HDL(2b). Further, when apoAI and HDL-C concentrations increased simultaneously, the shift to larger HDL size was more obvious. Which, in turn, indicated that HDL maturation might be enhanced and, the reverse cholesterol transport might be strengthened along with apoAI levels which might be a more powerful factor influencing the distribution of HDL subclasses. PMID:17476546

Tian, Li; Fu, Mingde; Jia, Lianqun; Xu, Yanhua; Long, Shiyin; Tian, Haoming; Tian, Ying

2007-05-01

87

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

88

Concentration distributions of arbitrary shaped particles in microfluidic channel flows  

NASA Astrophysics Data System (ADS)

We are interested in the study of the transient and steady state concentration distribution of orientable Brownian particles across channels at low Reynolds numbers. This is important in understanding margination of blood ``particles'' including platelets as well as new drug delivery and cancer nanotechnology particles which are involved in hemostasis as well as delivering drugs to the vascular endothelial cells. Although our formulation is general, the particles we consider are rigid Brownian ``surfboards'' which have been found to be effective in drug delivery since they are resistant to leukocyte attack [1]. The Stokes flow in the channel around the particles, driven by a mean pressure gradient, is computed using the Boundary Element method within the single layer formulation. The particle motion is calculated using rigid body dynamics with a contribution due to Brownian motion that satisfies the Fluctuation-Dissipation theorem. Finite concentrations are considered, and all hydrodynamic interactions are included. The concentration distribution is computed and interpreted as a balance between the concentration dependent variation in the non-equilibrium particle osmotic pressure and the cross stream particle normal stresses. [4pt] [1] J. A. Champion, S. Mitragotri, ``Role of target geometry in phagocytosis'', PNAS 103, 4930-4934, (2006)

Saibaba, Arvind; Shaqfeh, Eric; Darve, Eric

2009-11-01

89

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

90

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

91

BORON IS REQUIRED FOR ZEBRAFISH EMBRYOGENESIS  

Microsoft Academic Search

Boron is the only element known to be essential for plants, but only circumstantial evidence for essentiality exists in animals. We report here that boron is essential for the embryonic development of zebrafish (Danio rerio). Zebrafish were maintained in water with a boron concentration of 0.1 ?mol l-1 or supplemented to a concentration of 45 ?mol l-1 using ultrapure boric

RUBY I. ROWE; CURTIS D. ECKHERT

92

Boron removal from geothermal waters by electrocoagulation  

Microsoft Academic Search

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

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

2008-01-01

93

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

94

Direct assessment of the mechanical modulus of graphene co-doped with low concentrations of boron-nitrogen by a non-contact approach.  

PubMed

Boron and nitrogen co-doping has been shown to be an effective way to induce a band gap in graphene for electrical applications but only a few theoretical studies have been done to understand the elastic and mechanical properties of the modified graphene. Until now, no experimental assessment of the mechanical modulus of boron-nitrogen-doped graphene (BNG) has been reported in the literature. Here, we demonstrate a novel non-contact approach to determine the in-plane stiffness of BNG at low BN concentrations. The in-plane stiffness of BNG with 2 at% BN concentration was estimated to be about 309 N m(-1), which is lower than that of pristine graphene, in good agreement with some theoretical studies. Moreover, we correlated the conductivity of BNG with induced strain and found the BNG to be more sensitive than pristine graphene in response to externally applied strain. This result indicates that BNG is a more suitable material than graphene for strain sensor applications. PMID:24882359

Pan, Shun-Hsien; Medina, Henry; Wang, Sheng-Bo; Chou, Li-Jen; Wang, Zhiming M; Chen, Kuei-Hsien; Chen, Li-Chyong; Chueh, Yu-Lun

2014-07-10

95

3D concentration distributions of ion implants in amorphous solids  

NASA Astrophysics Data System (ADS)

Spatial distributions of implanted ions have been derived from depth profiles of implants at varied incidence angle by applying tomographic techniques. To this end we have developed a new version of an algorithm known as simultaneous iterative reconstruction technique (SIRT), which covers the experimental concentration range of about three decades. In addition, the finite depth resolution of the nuclear reaction analysis (NRA) is accounted for in our computer program. In this way, we have reconstructed the three-dimensional implantation distributions of 0.15 MeV 1H, 1.5 and 6 MeV 15N, and 4 MeV 30Si in amorphized Ge layers. The agreement with TRIM calculations is reasonable: 10% ± 0.5% for the first and 10% ± 5% for the second range moments. Consequences of the longitudinal and lateral tailing for ion beam applications to large scale integration problems are discussed.

Günzler, R.; Weiser, M.; Kalbitz, S.

1992-01-01

96

Concentrations and size distributions on Antarctic stratospheric aerosols  

SciTech Connect

Particle Measuring Systems laser particle spectrometer (ASAS-X and FSSP) probes were used to measure aerosol particle concentrations and size distributions during 11 out of 12 ER-2 flights between Punta Arenas (53{degree}S) and Antarctica (up to 72{degree}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 {mu}m 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 did the authors measure a depletion of small particles during a polar stratospheric cloud (PSC) encounter, 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 {mu}m radius, corresponding to type I PSCs, and occasionally, a second mode at 2.0 {mu}m radius, corresponding to type II PSCs.

Ferry, G.V.; Pueschel, R.F. (NASA Ames Research Center, Moffett Field, CA (United States)); Neish, E. (Neish Automation, Steamboat Springs, CO (United States)); Shultz, M. (Sterling Software, Palo Alto, CA (United States))

1989-11-30

97

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.

1997-08-05

98

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.

Miura, Michiko (Hampton Bays, NY); Slatkin, Daniel N. (Southold, NY)

1995-10-03

99

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

100

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.

Miura, Michiko (Hampton Bays, NY); Slatkin, Daniel N. (Southold, NY)

1997-08-05

101

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.

Miura, Michiko (Hampton Bays, NY); Slatkin, Daniel N. (Southold, NY)

1997-03-18

102

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.

1997-03-18

103

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

104

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

105

Synthesis of cross-linked chitosan possessing N-methyl-d-glucamine moiety (CCTS-NMDG) for adsorption/concentration of boron in water samples and its accurate measurement by ICP-MS and ICP-AES.  

PubMed

A chitosan resin derivatized with N-methyl-d-glucamine (CCTS-NMDG) was synthesized by using a cross-linked chitosan (CCTS) as base material. The N-methyl-d-glucamine (NMDG) moiety was attached to the amino group of CCTS through the arm of chloromethyloxirane. The adsorption behavior of 59 elements on the synthesized resin was systematically examined by using the resin packed in a mini-column, passing water samples through it and measuring the adsorbed elements in eluates by ICP-MS. The CCTS-NMDG resin shows high ability in boron sorption with the capacity of 0.61mmolml(-1) (=2.1mmol g(-1)). The sorption kinetics of this resin was faster than that of the commercially available resins. Other advantages of the synthesized resin are: (1) quantitative collection of boron at neutral pH regions; (2) complete removal of large amounts of matrices; (3) no loss of efficiency over prolonged usage; (4) effective collection of boron in wide range concentration using a mini column containing 1ml resin; (5) complete elution of boron with 1moll(-1) nitric acid. The resin was applied to the collection/concentration of boron in water samples. Boron in tap water and river water was found to be in the range of 6-8microgl(-1). The limit of detection (LOD) of boron after pretreatment with CCTS-NMDG resin and measurement by ICP-MS was 0.07microgl(-1) and the limit of quantification (LOQ) was 0.14microgl(-1) when the volume of each sample and eluent was 10ml. PMID:18969973

Sabarudin, Akhmad; Oshita, Koji; Oshima, Mitsuko; Motomizu, Shoji

2005-03-31

106

Boron reclamation  

SciTech Connect

A process to recover high purity /sup 10/B enriched crystalline boron powder from a polymeric matrix was developed on a laboratory basis and ultimately scaled up to production capacity. The process is based on controlled pyrolysis of boron-filled scrap followed by an acid leach and dry sieving operation to return the powder to the required purity and particle size specifications. Typically, the recovery rate of the crystalline powder is in excess of 98.5 percent, and some of the remaining boron is recovered in the form of boric acid. The minimum purity requirement of the recovered product is 98.6 percent total boron.

Smith, R.M.

1980-07-01

107

Reducing Boron Toxicity by Microbial Sequestration  

SciTech Connect

While electricity is a clean source of energy, methods of electricity-production, such as the use of coal-fired power plants, often result in significant environmental damage. Coal-fired electrical power plants produce air pollution, while contaminating ground water and soils by build-up of boron, which enters surrounding areas through leachate. Increasingly high levels of boron in soils eventually overcome boron tolerance levels in plants and trees, resulting in toxicity. Formation of insoluble boron precipitates, mediated by mineral-precipitating bacteria, may sequester boron into more stable forms that are less available and toxic to vegetation. Results have provided evidence of microbially-facilitated sequestration of boron into insoluble mineral precipitates. Analyses of water samples taken from ponds with high boron concentrations showed that algae present contained 3-5 times more boron than contained in the water in the samples. Boron sequestration may also be facilitated by the incorporation of boron within algal cells. Experiments examining boron sequestration by algae are in progress. In bacterial experiments with added ferric citrate, the reduction of iron by the bacteria resulted in an ironcarbonate precipitate containing boron. An apparent color change showing the reduction of amorphous iron, as well as the precipitation of boron with iron, was more favorable at higher pH. Analysis of precipitates by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectroscopy revealed mineralogical composition and biologicallymediated accumulation of boron precipitates in test-tube experiments.

Hazen, T.; Phelps, T.J.

2002-01-01

108

Trace Elements concentration and distribution across the Lake Chad Basin  

NASA Astrophysics Data System (ADS)

The Lake Chad, which is the largest Lake in West Africa, is situated between the latitude 12 ½ and 14 ½ north and longitude 130 east of the Southern fringe of the Sahara Desert. About 25 % of the Lake Chad lies within Nigeria, while the Republic of Cameroon, Chad and Niger share the rest of it. Lake Chad is completely landlocked and has no outlets; therefore loss of water is mainly through high rates of evaporation unlike similar Lakes in other parts of the World. The Lake Chad waters are fresh and of good quality with very low salt content which makes it suitable for irrigated agriculture. This study was carried out from upper stream to lower stream leading from Kano to the Damaturu region which is one of several water bodies that supply Lake Chad. Soil samples were collected from over seventy five sites and analyzed for ten Trace Elements(Be, Cd, Co, Cu, Mn,Fe, Mo, Pb, Zn, and Cr) using the Inductively Coupled Plasma (ICP)-OES. Assessment and Monitoring of Trace Elements concentrations are vital because they impact environment and can affect the human healthy. Since little is known about the Trace Elements status in Lake Chad Basin. The result in this study provides baseline information on the distribution and concentration of Trace Elements along the Lake Chad Basin.

Ndunguru, G. G.; Goni, I. B.; Mulugeta, V.; Grindley, J.; Banks, M. L.; Lee, J.; Adegoke, J. O.

2009-12-01

109

Borocaptate sodium: a potential boron delivery compound for boron neutron capture therapy evaluated in dogs with spontaneous intracranial tumors.  

PubMed

Borocaptate sodium (Na2B12H11SH) is a boron-carrying compound under consideration for use in boron neutron capture therapy. The biodistribution of boron from borocaptate sodium administration will partly determine boron neutron capture therapy efficacy and normal tissue radiation tolerance. The biodistribution of boron was determined in 30 dogs with spontaneous intracranial tumors at 2, 6, or 12 hr after intravenous borocaptate sodium infusion. Blood and tissue boron concentrations were measured using inductively coupled plasma atomic emission spectroscopy. Mean tumor boron concentration (mean +/- standard error) was 35.9 +/- 4.6 (n = 15), 22.5 +/- 6.0 (n = 9), and 7.0 +/- 1.1 micrograms of boron per g (n = 6) at 2, 6, and 12 hr, respectively, after borocaptate sodium infusion. Peritumor boron concentrations were elevated above that of normal brain in half of the dogs. Normal brain boron concentration (mean +/- standard error) was 4.0 +/- 0.5, 2.0 +/- 0.4, and 2.0 +/- 0.3 micrograms of boron per g at 2, 6, and 12 hr after infusion, respectively. Some cranial and systemic tissues, and blood, had high boron concentration relative to tumor tissue. Geometric dose sparing should partly offset these relatively high normal tissue and blood concentrations. Borocaptate sodium biodistribution is favorable because tumor boron concentrations of recommended magnitude for boron neutron capture therapy were obtained and there was a high tumor-to-normal brain boron concentration ratio. PMID:1465427

Kraft, S L; Gavin, P R; DeHaan, C E; Leathers, C W; Bauer, W F; Miller, D L; Dorn, R V

1992-12-15

110

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

111

Methods for boron delivery to mammalian tissue  

DOEpatents

Boron neutron capture therapy can be used to destroy tumors. This treatment modality is enhanced by delivering compounds to the tumor site where the compounds have high concentrations of boron, the boron compounds being encapsulated in the bilayer of a liposome or in the bilayer as well as the internal space of the liposomes. Preferred compounds, include carborane units with multiple boron atoms within the carborane cage structure. Liposomes with increased tumor specificity may also be used.

Hawthorne, M. Frederick (Encino, CA); Feaks, Debra A. (Los Angeles, CA); Shelly, Kenneth J. (Los Angeles, CA)

2003-01-01

112

Modeling contaminant concentration distributions in China's centralized source waters.  

PubMed

Characterizing contaminant occurrences in China's centralized source waters can provide an understanding of source water quality for stakeholders. The single-factor (i.e., worst contaminant) water-quality assessment method, commonly used in Chinese official analysis and publications, provides a qualitative summary of the country's water-quality status but does not specify the extent and degree of specific contaminant occurrences at the national level. Such information is needed for developing scientifically sound management strategies. This article presents a Bayesian hierarchical modeling approach for estimating contaminant concentration distributions in China's centralized source waters using arsenic and fluoride as examples. The data used are from the most recent national census of centralized source waters in 2006. The article uses three commonly used source water stratification methods to establish alternative hierarchical structures reflecting alternative model assumptions as well as competing management needs in characterizing pollutant occurrences. The results indicate that the probability of arsenic exceeding the standard of 0.05 mg/L is about 0.96-1.68% and the probability of fluoride exceeding 1 mg/L is about 9.56-9.96% nationally, both with strong spatial patterns. The article also discusses the use of the Bayesian approach for establishing a source water-quality information management system as well as other applications of our methods. PMID:21692445

Wu, Rui; Qian, Song S; Hao, Fanghua; Cheng, Hongguang; Zhu, Dangsheng; Zhang, Jianyong

2011-07-15

113

Modelling trace metal concentration distributions in estuarine waters  

NASA Astrophysics Data System (ADS)

Details are given of a numerical model study of the fate and transport of trace metals in estuarine waters, with particular application to the Mersey Estuary, located along the northwest coast of England. A dynamically integrated model was first developed, including a two-dimensional depth-integrated model and a one-dimensional cross-sectional averaged model. This model was then refined to predict the hydrodynamic and sediment and trace metal transport processes in the Mersey Estuary. Details are given of the development of a governing equation of the total trace metal transport, including both dissolved and particulate metals. The model was first calibrated against field data, collected during spring and neap tidal cycles, for water levels, salinity and suspended sediment. The calibrated model was then used to investigate the trace metal transport processes in the Mersey Estuary, with the partition coefficient between the dissolved and adsorbed particulate phases being modelled as a function of salinity. Comparisons were also made between the model predictions and field-measured data along the estuary. Reasonable agreement between the model results and field data has been obtained, indicating that the novel approach to model metal concentration distributions is capable of representing the fate and transport of trace metals in estuarine environments and can be used as computer-based tool for the environment management of estuarine waters.

Wu, Yan; Falconer, Roger; Lin, Binliang

2005-09-01

114

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

115

Distribution and concentration of cyclosporin in human blood  

Microsoft Academic Search

In patients receiving cyclosporin to minimise graft versus host disease after allogeneic bone marrow transplantation, whole blood cyclosporin concentration was roughly twice the serum concentration when blood was separated at 37 degrees C. In turn, blood separation at 37 degrees C resulted in a doubling of serum cyclosporin concentration compared with separation at room temperature. In vitro studies showed that

K Atkinson; K Britton; J Biggs

1984-01-01

116

In vivo and in vitro effects of boron and boronated compounds.  

PubMed

Boron is ubiquitously present in soils and water. Associated with pectin it is essential for vascular plants as a component of cell walls, and it stabilizes cell membranes. It is required for the growth of pollen tubes and is involved in membrane transport, stimulating H(+)-pumping ATPase activity and K+ uptake. However, a high boron concentration in the soils is toxic to plants and some boronated derivatives are used as herbicides. An absolute requirement for boron has not been definitively demonstrated in animals and humans. However, experiments with boron supplementation or deprivation show that boron is involved in calcium and bone metabolism, and its effects are more marked when other nutrients (cholecalciferol, magnesium) are deficient. Boron supplementation increases the serum concentration of 17 beta-estradiol and testosterone but boron excess has toxic effects on reproductive function. Boron may be involved in cerebral function via its effects on the transport across membranes. It affects the synthesis of the extracellular matrix and is beneficial in wound healing. Usual dietary boron consumption in humans is 1-2 mg/day for adults. As boron has been shown to have biological activity, research into the chemistry of boronated compounds has increased. Boronated compounds have been shown to be potent anti-osteoporotic, anti-inflammatory, hypolipemic, anti-coagulant and anti-neoplastic agents both in vitro and in vivo in animals. PMID:9638606

Benderdour, M; Bui-Van, T; Dicko, A; Belleville, F

1998-03-01

117

Arsenic, Boron, and Fluoride Concentrations in Ground Water in and Near Diabase Intrusions, Newark Basin, Southeastern Pennsylvania.  

National Technical Information Service (NTIS)

During an investigation in 2000 by the U.S. Environmental Protection Agency (USEPA) of possible contaminant releases from an industrial facility on Congo Road near Gilbertsville in Berks and Montgomery Counties, southeastern Pennsylvania, concentrations o...

L. A. Senior R. A. Sloto

2006-01-01

118

Influence of surface treatment and dopant concentration on field emission characteristics of boron-doped diamond thin films  

SciTech Connect

Field emission characteristics of B-doped diamond thin films terminated with oxygen and hydrogen were investigated. The diamond thin films were prepared by microwave plasma chemical vapor deposition. The dependence of emission characteristics on the surface treatment and on the B concentration was investigated. The turn-on voltage required to extract a current of 0.1 nA depended on these preparation parameters. The emitters with lower B concentration emitted electrons at a lower turn-on voltage, and the H-terminated emitters had a lower turn-on voltage than O-terminated emitters. The analysis of the slope and the intercept of Fowler{endash}Nordheim plot revealed that the dependence of turn-on voltage on the surface treatment is due to the difference of emission barrier height, and that the dependence on B concentration is due not to the emission barrier height but to the surface morphology. {copyright} {ital 1997 American Institute of Physics.}

Nagao, M.; Kondo, T.; Gotoh, Y.; Tsuji, H.; Ishikawa, J. [Department of Electronic Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-01 (Japan)] [Department of Electronic Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-01 (Japan); Miyata, K.; Kobashi, K. [Kobe Steel, Ltd., Electronics and Information Technology Laboratory, 5-5, 1-chome, Takatsuka-dai, Nishi-ku, Kobe 651-22 (Japan)] [Kobe Steel, Ltd., Electronics and Information Technology Laboratory, 5-5, 1-chome, Takatsuka-dai, Nishi-ku, Kobe 651-22 (Japan)

1997-11-01

119

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

120

Relationship Between Apolipoprotein Concentrations and HDL Subclasses Distribution  

Microsoft Academic Search

Alterations in plasma apolipoproteins levels can influence the composition, content, and distribution of plasma lipoproteins\\u000a that affect the risk of atherosclerosis. This study assessed the relationship between plasma apolipoproteins levels, mainly\\u000a apoAI, and HDL subclass distribution. The contents of plasma HDL subclasses were determined by two-dimensional gel electrophoresis\\u000a coupled with immunodetection in 545 Chinese subjects. Compared with a low apoAI

Li Tian; Mingde Fu; Lianqun Jia; Yanhua Xu; Shiyin Long; Haoming Tian; Ying Tian

2007-01-01

121

Distribution of Indoor Radon Concentrations in Pennyslvania, 1990-2007.  

National Technical Information Service (NTIS)

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 ...

E. L. Gross

2013-01-01

122

Distribution and concentration of suspended matter in Delaware Bay  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. The problem of remote sensing of suspended matter in water was analyzed in terms of the single-scattering albedo, and a semiempirical relationship between satellite radiance measurements and the concentration of suspended matter in the water was developed. The relationship was tested using data from the 7 July 1973 LANDSAT overpass of Delaware Bay with good results. Suspended sediment concentration maps for the entire Delaware Bay were prepared using radiance values extracted from LANDSAT MSS imagery and correlating them with ground truth samples collected from boats and helicopter.

Klemas, V. (principal investigator); Philpot, W.

1977-01-01

123

The boron geochemistry of siliceous sponges  

NASA Astrophysics Data System (ADS)

The boron content and isotopic composition (?11B) of marine carbonate organisms can be linked to the pH of the seawater in which they have grown, making carbonates a useful tool for palaeo-seawater pH reconstruction. A study by Furst (1981) documented unusually high boron concentrations in siliceous sponge spicules, in range from hundreds to a thousand ppm. This observation and the potential for preferential incorporation of the tetrahedral borate species into biogenic silica raises the question as to whether the boron chemistry of biogenic silica might also be influenced by seawater pH. We have measured the boron concentration and isotopic composition of siliceous sponges from the Southern Ocean region, with a view to (1) confirming the observations of Furst (1981), (2) assessing the factors that control boron incorporation and isotopic compositions of sponge silica, and (3) investigating the potentially significant role of siliceous sponges in the marine boron cycle. The measured boron concentrations in a diverse range of both demosponge and hexactinellid sponges confirm the high boron concentrations previously reported. The boron isotope compositions of these sponges vary from around +2‰ to +25‰ and greatly exceed the range in marine carbonates. This isotopic variation is inconsistent with seawater pH control but is correlated with ambient seawater silicon concentration, in a manner that suggests a link to silicon uptake kinetics and demand by sponges.

de Leon, A.; Wille, M.; Eggins, S. M.; Ellwood, M. J.

2009-12-01

124

Depth analysis of boron diffusion in MgO\\/CoFeB bilayer by x-ray photoelectron spectroscopy  

Microsoft Academic Search

We have studied the boron (B) diffusion in MgO\\/CoFeB bilayer by x-ray photoelectron spectroscopy depth analysis. A large concentration of B (B\\/Mg=0.16) was found to diffuse into the MgO barrier after 350 °C annealing. The boron in MgO is in a highly oxidized B3+ state and is homogenously distributed in the whole barrier. The important B diffusion in MgO could

Y. Lu; B. Lépine; G. Jézéquel; S. Ababou; M. Alnot; J. Lambert; A. Renard; M. Mullet; C. Deranlot; H. Jaffrès; F. Petroff; J.-M. George

2010-01-01

125

Synthesis and characterization of boron-doped Si quantum dots for all-Si quantum dot tandem solar cells  

Microsoft Academic Search

Multiple layers of Si quantum dots (QDs) in SiO2 with a narrow size distribution were synthesized by a co-sputtering technique. Structural, electrical and optical properties of Si QD\\/SiO2 multilayer films with various boron (B) concentrations introduced during the sputtering process were studied. X-ray photoelectron spectroscopy (XPS) revealed B–B\\/B–Si bonding, which suggests possible boron inclusion in the nanocrystals. The addition of

X. J. Hao; E. C. Cho; C. Flynn; Y. S. Shen; S. C. Park; G. Conibeer; M. A. Green

2009-01-01

126

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

127

Effect of Kaolin concentration on distribution coefficient of copper  

Microsoft Academic Search

Varying amounts of H+-Kaolin were equilibrated with spiked (high activity radioactive64Cu) water and kept overnight in a constant temperature water bath shaker. After proper filtration, through 0.45 µm Millipore memberane, the amount of radioactivity on the filter paper and the filtrate was measured separately using a Gamma ray well counter. Adsorption of Cu (expressed as distribution coefficient – Kd) was

Gian C. Gupta; Florence L. Harrison

1980-01-01

128

Biodistribution of boron in dogs with spontaneous intracranial tumors following borocaptate sodium administration.  

PubMed

Borocaptate sodium (Na2B12H11SH) is a potentially useful compound for boron neutron capture therapy of intracranial tumors. Tumor and normal tissue boron concentrations were evaluated in 30 dogs with naturally occurring intracranial tumors after i.v. borocaptate sodium infusion (55 mg boron/kg). Postmortem tissue boron concentrations were measured for three postinfusion time periods (2, 6, and 12 h) by inductively coupled plasma atomic emission spectroscopy. Mean boron concentrations for extracerebral tumors were 40.6 +/- 16.9 (2 h; n = 8), 25.9 +/- 11.7 (6 h; n = 5), and 8.6 +/- 4.5 micrograms boron/g (12 h; n = 6). Mean boron concentrations for intracerebral tumors were 30.6 +/- 17.5 (2 h; n = 7) and 2.9 +/- 1.8 micrograms boron/g (6 h; n = 4). Mean tumor boron concentrations were lower at longer postinfusion times. The tumor:normal brain boron concentration ranged from 0.8 to 19.8. Tumor:blood boron concentrations were less than one for all but three dogs and ranged from 0.04 to 1.4. Mean peritumor boron concentrations were highly variable but exceeded that of normal brain in 10 of 20 dogs. In some dogs, the mean peritumor boron concentration was similar to or exceeded the tumor boron concentration. Distant or contralateral normal brain had consistently low boron concentrations. Some cranial and systemic tissues had high boron concentrations, indicating substantial extravascular boron. The spontaneous animal tumors provided a realistic spectrum of data and enabled extensive sampling of diseased and normal tissues. The biodistribution of boron from borocaptate sodium administration was partially favorable because of high tumor boron concentrations. Empirical radiation dose tolerance studies should be used to determine the impact of the unfavorably high boron concentration of blood and some cranial tissues. PMID:8118814

Kraft, S L; Gavin, P R; Leathers, C W; DeHaan, C E; Bauer, W F; Miller, D L; Dorn, R V; Griebenow, M L

1994-03-01

129

Boron-loaded liposomes in the treatment of hepatic metastases: preliminary investigation by autoradiography analysis.  

PubMed

Boronophenylalanine (BPA)-loaded conventional and stabilized liposomes were prepared by the reversed phase evaporation method to treat liver metastases by boron neutron capture therapy. Conventional vesicles were composed of phosphatidylcholine and cholesterol, molar ratio 1:1. To obtain stealth liposomes, GM1 or PEG were included in the lipidic bilayer at a concentration of 6.67 or 5 mol%, respectively. Large unilamellar vesicles were formulated encapsulating BPA in the liposome aqueous compartment as a complex with fructose; BPA free base also was embedded into the lipidic bilayer. In vivo experiments were carried out after intravenous injection of liposome suspensions in BD-IX strain rats in which liver metastases had been induced. Alpha particle spectroscopy associated with histological analysis was performed to visualize boron spatial distribution in liver. Simultaneously, tissue boron concentrations were determined using inductively coupled plasma-mass spectroscopy. Results showed that PEG-modified liposomes accumulated boron in therapeutic concentrations (> 30 micrograms boron/g tissue) in metastatic tissue. The PEG-liposomes could be further explored in enhancing boron delivery to tumor cells. PMID:10892410

Pavanetto, F; Perugini, P; Genta, I; Minoia, C; Ronchi, A; Prati, U; Roveda, L; Nano, R

2000-01-01

130

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) [Duryea, PA; Stokowski, Stanley E. (Danville, CA) [Danville, CA

1987-04-28

131

Boron Removal by Polymer-Assisted Ultrafiltration  

Microsoft Academic Search

Boron contamination of natural waters is a widespread environmental problem which lacks a cost-effective solution. Polymer-assisted ultrafiltration is a method of boron removal that is compatible with other water-treatment processes. This boron removal technique exploits the pH-dependent complexation between boric acid and a macromolecule containing vicinal diol groups to prevent boric acid from passing through an ultrafiltration membrane. The concentration

Bryan M. Smith; Paul Todd; Christopher N. Bowman

1995-01-01

132

Hydrogen concentration and distribution in high-purity germanium crystals  

SciTech Connect

High-purity germanium crystals used for making nuclear radiation detectors are usually grown in a hydrogen ambient from a melt contained in a high-purity silica crucible. The benefits and problems encountered in using a hydrogen ambient are reviewed. A hydrogen concentration of about 2 x 10/sup 15/cm/sup -3/ has been determined by growing crystals in hydrogen spiked with tritium and counting the tritium ..beta..-decays in detectors made from these crystals. Annealing studies show that the hydrogen is strongly bound, either to defects or as H/sub 2/ with a dissociation energy > 3 eV. This is lowered to 1.8 eV when copper is present. Etching defects in dislocation-free crystals grown in hydrogen have been found by etch stripping to have a density of about 1 x 10/sup 7/ cm/sup -3/ and are estimated to contain 10/sup 8/ H atoms each.

Hansen, W.L.; Haller, E.E.; Luke, P.N.

1981-10-01

133

Inverse identification of intensity distributions from multiple flux maps in concentrating solar applications  

Microsoft Academic Search

Radiative flux measurements at the focal plane of solar concentrators are typically performed using digital cameras in conjunction with Lambertian targets. To accurately predict flux distributions on arbitrary receiver geometries directional information about the radiation is required. Currently, the directional characteristics of solar concentrating systems are predicted via ray tracing simulations. No direct experimental technique to determine intensities of concentrating

Ben Erickson; Jörg Petrasch

2012-01-01

134

Simulation and experimental study of boron clustering in crystalline silicon  

NASA Astrophysics Data System (ADS)

The tight-binding (TB) method in conjunction with atomic-scale computer simulation methods is used to study boron and boron-defect clusters containing up to five boron atoms and four self-interstitials within a matrix of crystalline silicon. As a particularly important p-type dopant, boron exhibits some problematical phenomena during the fabrication of microelectronic devices, especially transient enhanced diffusion (TED) following ion implantation of boron and subsequent annealing steps. The major focus in this thesis involves a search for particularly stable boron clusters (up to B4I 4), an investigation of possible precipitation paths of boron atoms following ion implantation and the dissolution mechanism of boron-interstitial clusters in the subsequent annealing steps. Though no clear mechanism of dissolution of boron clusters is found, key events were identified, such as diffusion of self-interstitials, stranding boron atoms, and the formation of mobile interstitial boron atoms. The extensive atomic information on the energetics and kinetics of point defects and dopant defects accumulated by these studies are used in a continuum-level process simulator---ALAMODE---to simulate boron diffusion in predeposition cases. The only inputs to ALAMODE are the atomic-scale results from TB and Local Density Approximation (LDA) calculations. Diffusion profiles are produced that were within experimental uncertainty at high boron concentrations. The sheet resistance of boron-doped Si was measured by four-point probes to study the dependence of boron precipitation on temperatures and doping levels. The experiments show that laser annealing can activate boron atoms at concentrations up to 20 times the solid solubility of boron in Si. Loss of conductivity due to the precipitation of boron atoms at moderate annealing temperatures (below 850°C) is not pronounced (less than 15%). Thus laser annealing followed by a conventional thermal annealing can provide highly doped and electrically active regions of silicon without the complication of TED.

Luo, Weiwei

2000-10-01

135

Demonstration of inter- and intracellular distribution of boron and gadolinium using micro-proton-induced X-ray emission (Micro-PIXE).  

PubMed

Micro-proton-induced X-ray emission (Micro-PIXE) was applied to determine inter- and intracellular distribution of boron (10B) and gadolinium (157Gd), the capture atoms used to kill tumor cells in neutron capture therapy (NCT). Cultured 9L gliosarcoma cells on Mylar film were exposed to sodium borocaptate (BSH) and gadobenate dimeglumine (Gd-BOPTA). To analyze the inter- and intracellular distribution of 10B and 157Gd in 9L gliosarcoma cells, the cells were irradiated using a proton beam of 1.7 or 3 MeV energy collimated to 1 microm diameter and emission X-ray was detected. The distribution of 10B and 157Gd in 9L gliosarcoma cells was then examined. In this study, we could directly analyze the inter- and intracellular distribution of 10B and 157Gd elements in 9L gliosarcoma cells directly using Micro-PIXE. This is the first report on the distribution of 10B employing a method to detect gamma-rays resulting from the nuclear reaction of 10B using particle-induced gamma-ray emission (PIGE). These results show that the distribution of 157Gd elements was correctly measured using micro-PIXE. 157Gd should have the same tendency as 10B in cultured 9L gliosarcoma cells and agree with the distribution in 9L gliosarcoma cells. Further investigation is necessary for a higher spatial resolution and optimization of the measurement time or improvement of the sampling method. In the future, it will be possible to employ this method to analyze the intracellular microdistribution of the capture element and in the development of new drugs for NCT. PMID:16898266

Endo, K; Yamamoto, T; Shibata, Y; Tsuboi, K; Matsumura, A; Kumada, H; Yamamoto, K; Sakai, T; Sato, T; Oikawa, M; Ohara, Y; Ishii, K

2006-01-01

136

Combination of boron and gadolinium compounds for neutron capture therapy. An in vitro study.  

PubMed

In neutron capture therapy, the therapeutic effect of the boron compound is based on alpha particles produced by the B(n, alpha) reaction while with the gadolinium compound the main radiation effect is from gamma rays derived from the Gd(n, gamma) reaction. The uptake and distribution within the tumor may be different among these compounds. Thus, the combination of the boron and gadolinium compounds may be beneficial for enhancing the radiation dose to the tumor. Chinese hamster fibroblast V79 cells were used. For the neutron targeting compounds, 10B (BSH) at 0, 5, 10, and 15 ppm, and 157Gd (Gd-BOPTA) at 0, 800, 1600, 2400, 3200, and 4800 ppm, were combined. The neutron irradiation was performed with thermal neutrons for 30 min. (neutron flux: 0.84 x 10(8) n/cm2/s in free air). The combination of the boron and gadolinium compounds showed an additive effect when the gadolinium concentration was lower than 1600 ppm. This additive effect decreased as a function of gadolinium concentration at 2400 ppm and resulted in no additive effect at more than 3200 ppm of gadolinium. In conclusion, the combination of the boron and gadolinium compounds can enhance the therapeutic effect with an optimum concentration ratio. When the gadolinium concentration is too high, it may weaken the boron neutron capture reaction due to the high cross-section of gadolinium compound against neutrons. PMID:15943038

Matsumura, A; Zhang, T; Nakai, K; Endo, K; Kumada, H; Yamamoto, T; Yoshida, F; Sakurai, Y; Yamamoto, K; Nose, T

2005-03-01

137

Determination and Standardization of Analytical Conditions for Dissolved Boron in Coastal Waters of East Sea in Korea by ICP-OES  

NASA Astrophysics Data System (ADS)

The analysis of metals in seawaters has been an important subject for many years. Achieving low-level detection limits as well as overcoming high matrix effect are requested in seawater analysis especially elements of interest are present in various chemical forms. Among them, boron is one of the widely distributed elements in nature and its concentrations of about 10 ppm in the Earth's crust and about 4.5 ppm in the seawater as borates. In seawater boron concentration exhibit a linear relationship to the amount of chloride ion present. Boron had been considered as one of the valuable elements to recover from seawaters for commercial use. Currently, we launched research team for the production of valuable metals from seawaters in Korea that can be used commercially. Several metals including boron were already under serious studies. In this study we aim to prepare standardized operational procedures in analysis of boron during pilot study for boron recovery as pilot recovery process. Inductively coupled plasma Optical Emission Spectrometry (ICP-OES) method is preferred for the analysis of the low levels of boron found in environmental samples such as seawater. In order to develop test method for the determination of dissolved Boron from East Sea Seawater in Korea, all soluble boron present in seawater has been tested and accuracy of measurement was checked from the sampling step. The result of analysis of boron in seawaters presents many difficult problems, ionization of from the alkali and alkaline earth metals. And the problems also exist in handling nebulizer and injector tubes in high saline solutions. The scope of this study was to determine boron which can contain up to 35psu dissolved salt. The work also included comparing various analytical methods for better accurate results in several solution conditions. Dilution, standard addition, matrix matching calibration methods was thoroughly tested differently and detailed operating conditions for using auxiliary gases were also presented.

Yoon, H.; Shin, M.; Yoon, C.; Lee, J.

2005-12-01

138

Predicted Drug Concentration Distribution Using a Validated Finite Element Model in Locally Advanced Breast Cancer.  

National Technical Information Service (NTIS)

The long-term objective of this study is to develop methods to predict the concentration-distribution of liposomally encapsulated doxorubicin in locally advanced breast cancer. Chemotherapy is frequently ineffective in shrinking these tumors to the point ...

B. Viglianti M. W. Dewhirst

2004-01-01

139

Boron adsorption using a new boron-selective hybrid gel and the commercial resin D564  

Microsoft Academic Search

A new hybrid gel with boron-selective functional groups is prepared with tetraethoxysilane (TEOS), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and a new precursor (W) synthesized from GPTMS and N-methylglucamine (MG). We investigate the boron adsorption onto the hybrid gel and the commercial resin D564 in aqueous solution by varying the initial boron concentration, pH, ionic strength, and temperature. Adsorption of both the hybrid gel

Haining Liu; Xiushen Ye; Quan Li; Taehoon Kim; Binju Qing; Min Guo; Fei Ge; Zhijian Wu; Kangtaek Lee

2009-01-01

140

Boron Stress Activates the General Amino Acid Control Mechanism and Inhibits Protein Synthesis  

Microsoft Academic Search

Boron is an essential micronutrient for plants, and it is beneficial for animals. However, at high concentrations boron is toxic to cells although the mechanism of this toxicity is not known. Atr1 has recently been identified as a boron efflux pump whose expression is upregulated in response to boron treatment. Here, we found that the expression of ATR1 is associated

Irem Uluisik; Alaattin Kaya; Dmitri E. Fomenko; Huseyin C. Karakaya; Bradley A. Carlson; Vadim N. Gladyshev; Ahmet Koc

2011-01-01

141

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

142

Suspended solids distribution in agitated, baffled vessels containing three concentric cooling coils  

Microsoft Academic Search

New experimental data are presented on the axial and radial distribution of solid particles suspended in a baffled, agitated liquid for the common – but previously uninvestigated – geometry of multiple concentric cooling coils around the impeller. Particle distribution trends are identified in relation to impeller speed, liquid height, and number of radial flow impellers on a single shaft. Interpretation

A. H. P. Skelland; N. M. Hassan

1999-01-01

143

Serum leptin concentration is associated with total body fat mass, but not abdominal fat distribution  

Microsoft Academic Search

OBJECTIVE: The obese (ob) gene encodes leptin which inhibits appetite and stimulates thermogenesis. Serum leptin concentrations are determined by total body fat mass, but the influence of visceral fat accumulation and other metabolic factors have not been clinically determined. METHODS: We determined the correlations between serum leptin concentrations and the total body fat mass, abdominal fat mass, abdominal fat distribution

H Shimizu; Y Shimomura; R Hayashi; K Ohtani; N Sato; T Futawatari; M Mori

1997-01-01

144

Image reconstruction of 2D concentration distribution of particle flow with extinction optical tomography  

Microsoft Academic Search

Optical tomography, as a novel technique developed recently, has drawn more and more interest among imaging of biology tissue, astronomy and industrial process monitoring, and so on. Extinction method is one of traditional measurement for particle concentration, which can be improve a novel optical measurement with computed tomography (CT) to reconstruct image of particle concentration distribution. In this paper, the

Yang Li; Renhuang Wang; Yingna Zheng

2003-01-01

145

Simple model of the vertical distribution of electron concentration in the ionosphere  

Microsoft Academic Search

An idealized model of the vertical distribution of the electron ; concentration in the E and F regions of the ionosphere is developed in which the ; model parameters are given by simple empirical expressions in terms of the ; characteristics conventionally measured at ionospheric observatories. ; Differences in the heights with a given electron concentration, as indicated by ;

P. A. Bradley; J. R. Dudeney

1973-01-01

146

Concentrations and distributions of carbonaceous species in ambient particles in Kaohsiung City, Taiwan  

Microsoft Academic Search

Concentrations and distributions of elemental carbon (EC) and organic carbon (OC) in particles were measured in Kaohsiung City, Taiwan. PM10 and PM2.5 samples were collected using a dichotomous sampler from November 1998 to April 1999 and were analyzed for carbonaceous species with an elemental analyzer. The concentrations of carbonaceous species in Kaohsiung City were comparable to those at other urban

Jim J Lin; Hua-Shan Tai

2001-01-01

147

Characterization of boron tolerant bacteria isolated from a fly ash dumping site for bacterial boron remediation.  

PubMed

Boron is an essential micronutrient for plants, but can above certain concentrations be toxic to living organisms. A major environmental concern is the removal of boron from contaminated water and fly ash. For this purpose, the samples were collected from a fly ash dumping site, Nagasaki prefecture, Japan. The chemical characteristics and heavy metal concentration of the samples were performed by X-ray fluorescent analysis and leaching test. For bacterial analysis, samples were collected in sterile plastic sheets and isolation was carried out by serial dilution method. The boron tolerant isolates that showed values of maximum inhibitory concentration toward boron ranging from 100 to 260 mM level were screened. Based on 16S rRNA sequencing and phylogenetic analysis, the isolates were most closely related to the genera Bacillus, Lysinibacillus, Microbacterium and Ralstonia. The boron tolerance of these strains was also associated with resistant to several heavy metals, such as As (III), Cr (VI), Cd, Cu, Pb, Ni, Se (III) and Zn. Indeed, these strains were arsenic oxidizing bacteria confirmed by silver nitrate test. These strains exhibited their salt resistances ranging from 4 to 15 % were determined in Trypticase soy agar medium. The boron tolerant strains were capable of removing 0.1-2.0 and 2.7-3.7 mg l(-1) boron from the medium and fly ash at 168 h. Thus, we have successfully identified the boron tolerant and removal bacteria from a fly ash dumping site for boron remediation. PMID:23212536

Edward Raja, Chellaiah; Omine, Kiyoshi

2013-08-01

148

Cross-sections of 10B(?, p) 13C nuclear reaction for boron analysis  

NASA Astrophysics Data System (ADS)

The 10B(?, p) 13C nuclear reaction shows great potential in boron depth profiling due to its large cross-section and a narrow resonance in the MeV energy range. Unfortunately, the existing cross-section data on this reaction are too rough for depth profiling. We present an accurate measurement of the cross-section of the (?, p) reaction on 10B using a boron thin film on a Si substrate, high-resolution detection and careful analysis of the proton spectra. Angular distributions of the cross-section at the resonant energy Er=1512 keV are also presented. The sharp resonance at 1512 keV was used to measure the B depth distribution in a borophosphosilicate glass (BPSG) thin film. The boron concentration profiles are compared with SIMS measurement and are found in good agreement.

Chen, H.; Wang, X. M.; Shao, L.; Liu, J. R.; Yen, A. C.; Chu, Wei-kan

2003-09-01

149

Roles of ATR1 paralogs YMR279c and YOR378w in boron stress tolerance.  

PubMed

Boron is a necessary nutrient for plants and animals, however excess of it causes toxicity. Previously, Atr1 and Arabidopsis Bor1 homolog were identified as the boron efflux pump in yeast, which lower the cytosolic boron concentration and help cells to survive in the presence of toxic amount of boron. In this study, we analyzed ATR1 paralogs, YMR279c and YOR378w, to understand whether they participate in boron stress tolerance in yeast. Even though these genes share homology with ATR1, neither their deletion rendered cells boron sensitive nor their expression was significantly upregulated by boron treatment. However, expression of YMR279, but not YOR378w, from the constitutive GAPDH promoter on a high copy plasmid provided remarkable boron resistance by decreasing intracellular boron levels. Thus our results suggest the presence of a third boron exporter, YMR279c, which functions similar to ATR1 and provides boron resistance in yeast. PMID:21621519

Bozdag, Gonensin Ozan; Uluisik, Irem; Gulculer, Gulce Sila; Karakaya, Huseyin C; Koc, Ahmet

2011-06-17

150

Boron nitride nanotubes  

DOEpatents

Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

Smith, Michael W. (Newport News, VA); Jordan, Kevin (Newport News, VA); Park, Cheol (Yorktown, VA)

2012-06-06

151

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

152

Sensitivity of Vertebrate Embryos to Boron Compounds.  

National Technical Information Service (NTIS)

Developmental stages of rainbow trout, channel catfish, goldfish, leopard frog, and Fowler's toad were treated in a continuous flow system with boric acid and borax concentrations ranging from 0.001-300 ppm boron. Exposure was initiated subsequent to fert...

J. A. Black W. J. Birge

1977-01-01

153

Reactions of boron with soils  

Microsoft Academic Search

Boron is an essential micronutrient for plants, but the range between deficient and toxic B concentration is smaller than for any other nutrient element. Plants respond directly to the activity of B in soil solution and only indirectly to B adsorbed on soil constituents. Soil factors affecting availability of B to plants are: pH, texture, moisture, temperature, organic matter and

Sabine Goldberg

1997-01-01

154

Factors Controlling Droplet Concentration and Size Distribution in Clouds over Dominica  

NASA Astrophysics Data System (ADS)

Since precipitation in convective, tropical clouds, and the impact of these clouds on Earth's radiation budget, are dependent on the concentration and size distribution of the water droplets that make up the clouds, we are interested in understanding the factors controlling the droplet concentration and size distribution in these clouds. Previous studies from field campaigns have led to contradictory conclusions, with some research pointing to updraft velocity as the most influential factor, and other studies pointing to aerosol concentration. The 2011 Dominica Experiment (DOMEX) field campaign provides a wealth of data with which to study this problem, and to test existing models of droplet activation and growth; these data include aerosol and cloud droplet concentrations and size distributions, and wind speed measurements, from research flights above and upwind of the island of Dominica, as well as precipitation data from rain gauges installed on the island. Over 17 DOMEX research flights, cloud droplet concentrations averaged over flight legs above the island were positively correlated with aerosol concentrations from legs flown upwind of the island at 305 m altitude, while cloud droplet mean diameters were negatively correlated with oversea aerosol concentrations, supporting the idea that higher aerosol concentrations (if they are water soluble aerosols, such as sea salt) result in more droplets becoming activated and not growing as large. Meanwhile, average horizontal wind speeds in the oversea legs were negatively correlated with droplet concentrations in clouds over the island, and positively correlated with the mean diameter, the opposite of what would be expected if stronger convection accompanied the higher horizontal wind speeds. The horizontal wind speeds were also negatively correlated with the aerosol concentrations, especially at very low wind speeds, suggesting that the negative impact of wind speed on droplet concentration may have been due to a different aerosol regime that accompanied the lower wind speeds.

Russotto, R. D.; Storelvmo, T.; Smith, R. B.

2011-12-01

155

Anomalous kinetics in diffusion limited reactions linked to non-Gaussian concentration probability distribution function  

NASA Astrophysics Data System (ADS)

We investigate anomalous reaction kinetics related to segregation in the one-dimensional reaction-diffusion system A + B --> C. It is well known that spatial fluctuations in the species concentrations cause a breakdown of the mean-field behavior at low concentration values. The scaling of the average concentration with time changes from the mean-field t-1 to the anomalous t-1/4 behavior. Using a stochastic modeling approach, the reaction-diffusion system can be fully characterized by the multi-point probability distribution function (PDF) of the species concentrations. Its evolution is governed by a Fokker-Planck equation with moving boundaries, which are determined by the positivity of the species concentrations. The concentration PDF is in general non-Gaussian. As long as the concentration fluctuations are small compared to the mean, the PDF can be approximated by a Gaussian distribution. This behavior breaks down in the fluctuation dominated regime, for which anomalous reaction kinetics are observed. We show that the transition from mean field to anomalous reaction kinetics is intimately linked to the evolution of the concentration PDF from a Gaussian to non-Gaussian shape. This establishes a direct relationship between anomalous reaction kinetics, incomplete mixing and the non-Gaussian nature of the concentration PDF.

de Anna, Pietro; Le Borgne, Tanguy; Dentz, Marco; Bolster, Diogo; Davy, Philippe

2011-11-01

156

Boron doping a semiconductor particle  

SciTech Connect

A method (10,30) of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried (16), with the boron film then being driven (18) into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out (38) into piles and melted/fused (40) with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements.

Stevens, Gary Don (18912 Ravenglen Ct., Dallas, TX 75287); Reynolds, Jeffrey Scott (703 Horizon, Murphy, TX 75094); Brown, Louanne Kay (2530 Poplar Tr., Garland, TX 75042)

1998-06-09

157

Boron doping a semiconductor particle  

SciTech Connect

A method of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried, with the boron film then being driven into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out into piles and melted/fused with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements. 2 figs.

Stevens, G.D.; Reynolds, J.S.; Brown, L.K.

1998-06-09

158

Modeling of topside ionosphere electron concentration global distribution by satellite sounding data utilization  

NASA Astrophysics Data System (ADS)

The task of topside electron concentration empirical modeling usually consists of two parts: 1) global mapping of the main peak parameters and 2) adequate description of vertical distribution of ionization. Moreover, the initial information on global distribution of electron concentration can be obtained by means of ionosphere topside vertical sounding from satellite boards. The INTERCOSMOS-19 satellite specific peculiarities has allowed to construct LT-maps of critical frequencies foF2, to study the spatial and temporal characteristics large-scale inhomogeneities during the period of high solar activity. Two-parametrical approximation of electron concentration profile by Epstein function was used for altitude distribution of ionization description. ALOUETTE, INTERCOSMOS-19 and COSMOS-1809 satellite data utilization have allowed to obtain model coefficients for different levels of solar activity, seasons, local time.

Depuev, V. H.; Pulinets, S. A.

159

Boron toxicity in the rare serpentine plant, Streptanthus morrisonii.  

PubMed

The release of boron-laden mist from the cooling towers of some geothermal power stations in northern California potentially threatens nearby populations of the rare serpentine plant, Streptanthus morrisonii F. W. Hoffm. To assess the tolerance of S. morrisonii to high levels of boron, the effect of boron on leaf condition, life history, germination rate, growth rate, allocation and photosynthesis was measured on plants grown in a greenhouse. Relative to other species, S. morrisonii was tolerant of excess boron. On serpentine soil, mild to moderate toxicity symptoms (older leaves exhibiting chlorosis and necrosis, but few leaves killed) were apparent when the boron concentration in applied nutrient solutions was 240-650 microm. Severe toxicity symptoms (significant leaf loss, young leaves with toxicity symptoms) were apparent when the applied solution was over 1000 microm boron. Above 1000 microm boron, S. morrisonii appeared unable to complete its life cycle. On a tissue basis, boron toxicity was first observed when leaf boron content was 40-90 micromol g(-1) dry weight. In leaves with severe boron toxicity (> 35% injury), the boron content was generally above 130 micromol g(-1) dry weight. These levels were an order of magnitude above the tissue boron content of plants in the field. Prior to the onset of pronounced boron toxicity symptoms, growth rate, allocation patterns, and photosynthesis were unaffected by high boron. These results indicate that inhibition of growth and photosynthesis occurred because of a loss of viable tissue due to boron injury, rather than a progressive decline as leaf boron levels increased. PMID:15092365

Sage, R F; Ustin, S L; Manning, S J

1989-01-01

160

Generation of concentration gradient by controlled flow distribution and diffusive mixing in a microfluidic chip.  

PubMed

We have developed a simple method to generate a concentration gradient in a microfluidic device. This method is based on the combination of controlled fluid distribution at each intersection of a microfluidic network by liquid pressure and subsequent diffusion between laminas in the downstream microchannel. A fluid dynamic model taking into account the diffusion coefficient was established to simulate the on-chip flow distribution and diffusion. Concentration gradients along a distance of a few hundred micrometers were generated in a series of microchannels. The gradients could be varied by carefully regulating the liquid pressure applied to the sample injection vials. The observed concentration gradients of fluorescent dyes generated on the microfluidic channel are consistent with the theoretically predicted results. The microfluidic design described in this study may provide a new tool for applications based on concentration gradients, including many biological and chemical analyses such as cellular reaction monitoring and drug screening. PMID:15100827

Yang, Mengsu; Yang, Jun; Li, Cheuk-Wing; Zhao, Jianlong

2002-08-01

161

Preferential distribution and oxidation inhibiting\\/catalytic effects of boron in carbon fiber reinforced carbon (CFRC) composites  

Microsoft Academic Search

Two different batches of CFRC composites were prepared in the absence\\/presence of B with the expectation of increasing oxidation stability and improving the processing compatibility of CFRC composites in commercial applications. The composites were examined to reveal the nature of substitutional B in oxidation, crystallinity and distribution preference in the composites. Substitutional B acts both a catalyst and an inhibitor

Young-Jae Lee; Hyeok-Jong Joo; Ljubisa R Radovic

2003-01-01

162

Inverse identification of intensity distributions from multiple flux maps in concentrating solar applications  

NASA Astrophysics Data System (ADS)

Radiative flux measurements at the focal plane of solar concentrators are typically performed using digital cameras in conjunction with Lambertian targets. To accurately predict flux distributions on arbitrary receiver geometries directional information about the radiation is required. Currently, the directional characteristics of solar concentrating systems are predicted via ray tracing simulations. No direct experimental technique to determine intensities of concentrating solar systems is available. In the current paper, multiple parallel flux measurements at varying distances from the focal plane together with a linear inverse method and Tikhonov regularization are used to identify the directional and spatial intensity distribution at the solution plane. The directional binning feature of an in-house Monte Carlo ray tracing program is used to provide a reference solution. The method has been successfully applied to two-dimensional concentrators, namely parabolic troughs and elliptical troughs using forward Monte Carlo ray tracing simulations that provide the flux maps as well as consistent, associated intensity distribution for validation. In the two-dimensional case, intensity distributions obtained from the inverse method approach the Monte Carlo forward solution. In contrast, the method has not been successful for three dimensional and circular symmetric concentrator geometries.

Erickson, Ben; Petrasch, Jörg

2012-06-01

163

VELOCITY AND CONCENTRATION DISTRIBUTIONS IN SEDIMENT-MIXED FLUID: AN APPROACH WITH MIXING LENGTH CONCEPT  

Microsoft Academic Search

Mathematical models have been developed to predict the vertical velocity and sediment concentration distributions in a sediment-laden turbulent open channel flow taking into account a modified mixing length based on sediment-induced stratification. The coupled non-linear differential equations for vertical velocity and concentration arising out of the problem have been solved numerically and the results have been compared with the comprehensive

K. Ghoshal; B. S. Mazumder

2006-01-01

164

Concentration  

NSDL National Science Digital Library

Watch your solution change color as you mix chemicals with water. Then check molarity with the concentration meter. What are all the ways you can change the concentration of your solution? Switch solutes to compare different chemicals and find out how concentrated you can go before you hit saturation!

Simulations, Phet I.; Chamberlain, Julia; Malley, Chris; Lancaster, Kelly; Moore, Emily B.; Perkins, Kathy

2012-03-09

165

Application of wavelength scanning for measuring water vapour concentration by distributed laser diode  

NASA Astrophysics Data System (ADS)

A technique which takes advantage of distributed feedback laser diode (DFB-LD) wavelength scanning to measure water vapor concentration is presented. Concentration is gotten by peak absorption rate according to Beer-Lambert law and absorption coefficient of water vapor in HITRAN database. Theoretical work on the pressure affection to light intensity absorption rate has been done, a scheme is presented to cope with the affection of overlap of two adjacent lines, it takes advantage of the peak absorption difference between 1368.597nm and 1367.862 nm, and the difference value is used to calculate the water-vapor concentration.

Chang, Jun; Guangping, Lv; Zhou, Guoqing; Chen, Kun; Zhang, Yan; Wang, Zhongliang; Zhang, Shicong; Wang, Qiang; Song, Fujun

2011-09-01

166

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

NASA Astrophysics Data System (ADS)

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.

1984-02-01

167

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

168

Distribution of exposure concentrations and doses for constituents of environmental tobacco smoke.  

PubMed

The ultimate goal of the research reported in this series of three articles is to derive distributions of doses of selected environmental tobacco smoke (ETS)-related chemicals for nonsmoking workers. This analysis uses data from the 16-City Study collected with personal monitors over the course of one workday in workplaces where smoking occurred. In this article, we describe distributions of ETS chemical concentrations and the characteristics of those distributions (e.g., whether the distribution was log normal for a given constituent) for the workplace exposure. Next, we present population parameters relevant for estimating dose distributions and the methods used for estimating those dose distributions. Finally, we derive distributions of doses of selected ETS-related constituents obtained in the workplace for people in smoking work environments. Estimating dose distributions provided information beyond the usual point estimate of dose and showed that the preponderance of individuals exposed to ETS in the workplace were exposed at the low end of the dose distribution curve. The results of this analysis include estimations of hourly maxima and time-weighted average (TWA) doses of nicotine from workplace exposures to ETS (extrapolated from 1 day to 1 week) and doses derived from modeled lung burdens of ultraviolet-absorbing particulate matter (UVPM) and solanesol resulting from workplace exposures to ETS (extrapolated from 1 day to 1 year). PMID:10765411

LaKind, J S; Ginevan, M E; Naiman, D Q; James, A C; Jenkins, R A; Dourson, M L; Felter, S P; Graves, C G; Tardiff, R G

1999-06-01

169

Vertical profiles of black carbon concentration and particle number size distribution in the North China Plain  

NASA Astrophysics Data System (ADS)

The vertical distribution of aerosols is of great importance to our understanding in the impacts of aerosols on radiation balance and climate, as well as air quality and public health. To better understand and estimate the effects of atmospheric components including trace gases and aerosols on atmospheric environment and climate, an intensive field campaign, Vertical Observations of trace Gases and Aerosols in the North China Plain (VOGA-NCP), was carried out from late July to early August 2013 over a rural site in the polluted NCP. During the campaign, vertical profiles of black carbon (BC) concentration and particle number size distribution were measured respectively by a micro-Aethalometer and an optical particle counter attached to a tethered balloon within 1000 m height. Meteorological parameters, including temperature, relative humidity, wind speed and wind direction, were measured simultaneously by a radiosonde also attached to the tethered balloon. Preliminary results showed distinct diurnal variations of the vertical distribution of aerosol total number concentration and BC concentration, following the development of the mixing layer. Generally, there was a well mixing of aerosols within the mixing layer and a sharp decrease above the mixing layer. Particularly, a small peak of BC concentrations was observed around 400-500 m height for several profiles. Further analysis would be needed to explain such phenomenon. It was also found that measured vertical profiles of BC using the filter-based method might be affected by the vertical distribution of relative humidity.

Ran, L.; Deng, Z.

2013-12-01

170

Concentration and Size Distribution of Culturable Airborne Microorganisms in Outdoor Environments in Beijing, China  

Microsoft Academic Search

A one-year (from June 2003 to May 2004) study of airborne microbial concentration and size distribution was conducted systematically at three selected sampling sites in Beijing. Microbial samples were collected in triplicate for 3 min, 3 times per day, for 3 consecutive days of each month using FA-I sampler (imitated Andersen sampler, made by Applied Technical Institute of Liaoyang, China).

Zhiguo Fang; Zhiyun Ouyang; Hua Zheng; Xiaoke Wang

2008-01-01

171

Distribution and concentration of total phenolics, condensed tannins, and nordihydroguaiaretic acid (NDGA) in creosotebush ( Larrea tridentata)  

Microsoft Academic Search

This paper focuses on the presence and distribution of secondary phenolic compounds found within creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov.]. Total phenolics, condensed tannins and nordihydroguaiaretic acid (NDGA) were measured in nine categories of tissue within creosotebush. Total phenolic and condensed tannin concentrations were determined using colorimetric methods while NDGA content was determined with high performance liquid

Paul W. Hyder; E. L. Fredrickson; Rick E. Estell; Mario Tellez; Robert P. Gibbens

2002-01-01

172

The Spatial Distribution of Particulate Concentrations in the Denver Metropolitan Area  

Microsoft Academic Search

Geographers can provide information that is important to the establishment and revision of air quality standards. A spatial approach to the description of air quality can pinpoint segments of the population that are disproportionately exposed to potential health hazards. Temporal trends in the spatial distribution of given levels of pollutant concentration may not be the same as those determined from

David Greenland; Richard A. Yorty

1985-01-01

173

Concentration and Distribution of Six Trace Metals in Northern Kentucky Soils  

Microsoft Academic Search

Concentration and distribution of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) were determined in 26 soil profiles (n = 78) of northern Kentucky in response to environmental concerns about increasing anthropogenic inputs in a fast-paced urbanizing area. The selected sites represent alluvial, glacial till or residual soils that have not received any biosolid- or

J. R. V. PILS; A. D. KARATHANASIS; T. G. MUELLER

2004-01-01

174

Concentrations and size distributions of fine aerosol particles measured at roof level in urban zone  

Microsoft Academic Search

During the experimental Field Experiments to Constrain Models of Atmospheric Pollution and Transport of Emissions (ESCOMPTE) campaign in June–July 2001, concentrations and size distributions of fine particles (14–722 nm) were measured at roof level in downtown Marseille (France). Part of the campaign was dedicated to the study of aerosol behavior in relation to strong photochemical events (which were identified as

S. Despiau; D. Croci

2007-01-01

175

Prediction of Temperature and Concentration Distributions of Distillation Sieve Trays by CFD  

Microsoft Academic Search

A three-dimensional two-fluid computational fluid dynamics (CFD) model is developed to predict concentration and temperature distributions on sieve trays of distillation columns and good simulation results are obtained. The dispersed gas phase and continuous liquid phase are modeled in the Eulerian framework as two interpenetrating phases with interphase momentum, heat and mass transfer. Closure models are developed for interphase transfer

Mahmood-Reza Rahimi; Rahbar Rahimi; Farhad Shahraki; Morteza Zivdar

2006-01-01

176

Effect of stratification due to suspended sand on velocity and concentration distribution in unidirectional flows  

Microsoft Academic Search

Sediment-induced stratification effects on velocity profiles and sediment concentration distribution in a steady, uniform turbulent flow are examined in this paper. The early work concerning sediment stratification relates this to the von Karman constant's variability. Subsequent attempts to account for stratification were based on the stratified flow analogy, introducing the parameters ? and ?, whose values were assumed to be

Marine J. Herrmann; Ole S. Madsen

2007-01-01

177

Particle size concentration distribution and influences on exhaled breath particles in mechanically ventilated patients.  

PubMed

Humans produce exhaled breath particles (EBPs) during various breath activities, such as normal breathing, coughing, talking, and sneezing. Airborne transmission risk exists when EBPs have attached pathogens. Until recently, few investigations had evaluated the size and concentration distributions of EBPs from mechanically ventilated patients with different ventilation mode settings. This study thus broke new ground by not only evaluating the size concentration distributions of EBPs in mechanically ventilated patients, but also investigating the relationship between EBP level and positive expiratory end airway pressure (PEEP), tidal volume, and pneumonia. This investigation recruited mechanically ventilated patients, with and without pneumonia, aged 20 years old and above, from the respiratory intensive care unit of a medical center. Concentration distributions of EBPs from mechanically ventilated patients were analyzed with an optical particle analyzer. This study finds that EBP concentrations from mechanically ventilated patients during normal breathing were in the range 0.47-2,554.04 particles/breath (0.001-4.644 particles/mL). EBP concentrations did not differ significantly between the volume control and pressure control modes of the ventilation settings in the mechanically ventilated patients. The patient EBPs were sized below 5 µm, and 80% of them ranged from 0.3 to 1.0 µm. The EBPs concentrations in patients with high PEEP (> 5 cmH?O) clearly exceeded those in patients with low PEEP (? 5 cmH?O). Additionally, a significant negative association existed between pneumonia duration and EBPs concentration. However, tidal volume was not related to EBPs concentration. PMID:24475230

Wan, Gwo-Hwa; Wu, Chieh-Liang; Chen, Yi-Fang; Huang, Sheng-Hsiu; Wang, Yu-Ling; Chen, Chun-Wan

2014-01-01

178

Determination of selected heavy metal concentrations and distribution in a southwestern stream using macrophytes.  

PubMed

Since the reduction of the arsenic standard from 50 to 10 ?g L(-1) by the US Environmental Protection Agency in 2006 many small town and rural water municipalities were left with the task of preventing or mitigating arsenic contamination of drinking water supplies. In this study macrophytes and sediments were used to determine the concentration and distribution of heavy metals (As, Cd, Cu, Pb, and Zn) within the primary source of drinking water (Gallinas River watershed) to the residents of Las Vegas, New Mexico. Sampling was done in the spring and fall at four sites, two above the city and two below, and samples were analyzed using ICP-MS. Results showed significantly higher (p<.05) metal concentrations in plant roots than shoots for most metals. Spearman's correlation showed positive correlations (r>.3) between plant and sediment concentrations of Cd, Pb, Zn, As, and a negative correlation for Cu. The site above waste water treatment plant (AWWTP) had the highest plant tissue concentrations of Cd, Pb, Zn, and As. All of these concentrations attained critical toxicity levels exceeding sediment quality guidelines. High concentration factor values and levels of metals detected in macrophyte tissues indicate that heavy metals within sediments in the Gallinas River occur in bioavailable forms. Correlations between plant and sediment metal concentrations indicate that metal concentrations in macrophyte tissues are a good reflection of metal concentrations within the sediment in the Gallinas River. PMID:21621260

Martinez, Edward A; Shu-Nyamboli, Chemanji

2011-09-01

179

Reactivity of boron fullerenes  

Microsoft Academic Search

The properties of carbon and boron fullerenes are compared, and similarities and distinctions are pointed out. The ionization\\u000a potentials and electron affinities of boron nanoparticles are estimated, and the binding energy for these systems is calculated.

S. P. Ionov; G. V. Ionova; N. T. Kuznetsov

2011-01-01

180

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

2012-05-01

181

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

182

Occurrence and distribution of selected heavy metals and boron in groundwater of the Gulf of Khambhat region, Gujarat, India.  

PubMed

The concentration of selected heavy metals, like As, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn as well as B, was measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) in groundwater samples from various locations in the Gulf of Khambhat (GoK), an inlet of the Arabian Sea in the state of Gujarat, India, during post-monsoon, winter, and pre-monsoon seasons in a year. Most heavy elements are characterized by low mobility under slightly alkaline and reducing conditions; concentrations in confined aquifers are smaller than the maximum permissible values for drinking water. The temporal changes indicate that a majority of metals is entering the aquifer during monsoon. Principle component analysis of the heavy metal data suggests that Co, Cu, Cd, and Zn are interrelated with each other and derived significantly from anthropogenic route, while input of Pb and Cr may be due to atmospheric deposition in the study area. Both weathering of rocks and anthropogenic input were found to be main sources of elements in the groundwater. The heavy metal levels in groundwaters of the GoK region in comparison with some of the European and Asian sites were higher; however, these metal levels were found to be comparable with few urban sites in the world. PMID:24293301

Upadhyaya, Devang; Survaiya, Mayur D; Basha, Shaik; Mandal, Subir K; Thorat, R B; Haldar, Soumya; Goel, Sangita; Dave, Himal; Baxi, Krushnakant; Trivedi, Rohit H; Mody, Kalpana H

2014-03-01

183

[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

184

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

185

Distribution of indoor radon concentrations and elements of a strategy for control  

SciTech Connect

Indoor radon concentrations vary widely in the US housing stock, with normal concentrations estimated to cause a significant risk of lung cancer by comparison with environmental exposures normally considered, and high concentrations causing risks that exceed even those from cigarette smoking. The probability distribution, i.e., the number of houses at various concentrations, can be estimated from an analysis of the US indoor radon data accumulated to date. Such an analysis suggests that in about a million houses, occupants are receiving exposures greater than those experienced by uranium miners. The form of the frequency distribution, including not only the average concentration, but also the number of houses with high levels, has substantial influence on strategies for control of indoor radon. Such strategies require three major elements: formulation of control objectives in terms of guidelines for remedial action and for new houses; selection of means for identifying homes with high concentrations; and a framework for deciding what types of control measures are appropriate to particular circumstances and how rapidly they should be employed.

Nero, A.V. Jr.

1986-05-01

186

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

187

Distribution of exposure concentrations and doses for constituents of environmental tobacco smoke  

SciTech Connect

The ultimate goal of the research reported in this series of three articles is to derive distributions of doses of selected environmental tobacco smoke (ETS)-related chemicals for nonsmoking workers. This analysis uses data from the 16-City Study collected with personal monitors over the course of one workday in workplaces where smoking occurred. In this article, the authors describe distributions of ETS chemical concentrations and the characteristics of those distributions for the workplace exposure. Next, they present population parameters relevant for estimating dose distributions and the methods used for estimating those dose distributions. Finally, they derive distributions of doses of selected ETS-related constituents obtained in the workplace for people in smoking work environments. Estimating dose distributions provided information beyond the usual point estimate of dose and showed that the preponderance of individuals exposed to ETS in the workplace were exposed at the low end of the dose distribution curve. The results of this analysis include estimations of hourly maxima and time-weighted average (TWA) doses of nicotine from workplace exposures to ETS and doses derived from modeled lung burdens of ultraviolet-absorbing particulate matter (UVPM) and solanesol resulting from workplace exposures to ETS (extrapolated from 1 day to 1 year).

LaKind, J.S. [LaKind Associates (United States)] [LaKind Associates (United States); Ginevan, M.E. [M.E. Ginevan and Associates (United States)] [M.E. Ginevan and Associates (United States); Naiman, D.Q. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mathematical Sciences] [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mathematical Sciences; James, A.C. [A.C. James and Associates (United States)] [A.C. James and Associates (United States); Jenkins, R.A. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States); Dourson, M.L.; Felter, S.P. [TERA (United States)] [TERA (United States); Graves, C.G.; Tardiff, R.G. [Sapphire Group, Inc., Bethesda, MD (United States)] [Sapphire Group, Inc., Bethesda, MD (United States)

1999-06-01

188

[Interpretation of spatial distribution pattern for dissolved inorganic nitrogen concentration in coastal estuary using hyperspectral data].  

PubMed

Choosing dissolved inorganic nitrogen (DIN) as one of the representative nutritional salt monitoring indexes, a hyperspectral remotely sensed inversion model was built and applied to quantitatively retrieve water quality parameters with its spatial distribution patterns in coastal estuary with high suspended sediment concentration (SSC). It was found that when SSC was larger than 0.1 kg/m3, DIN concentration had a notable inverse correlation with SSC and the correlation coefficient R2 reached 0.617. Based on this conclusion, firstly the in-situ observed water surface remote sensing reflectance was resampled according to the spectral response characters of Hyperion sensor. And then, statistical correlation analysis between reflectance and DIN concentration was carried out. The results showed that band reflectance of R804 and R630 representing the second and first reflectance peak of water spectrum curve were sensitive to the variation of DIN concentration. And then, a pseudo remotely sensed sand parameter index R804 x R630/(R804 - R630) was calculated for the construction of the nonlinear DIN quantitative reversion model. Correlation coefficient R2 between observed and simulated DIN concentrations for 29 calibrating samples and 10 validating samples were 0.746 and 0.67, while their mean absolute errors reached 109.07 and 147.58 microg/L, respectively. The model was then applied on Hyperion hyperspectral image to get the spatial distribution character of DIN concentration in Sheyanghe river estuary and the DIN concentration was between 52 to 513 microg/L. Results indicated that in coastal estuary which was dominated by suspended sediments, the diffusive trends of DIN concentration reversed by remote sensing techniques had an intimate relationship with motions of tidal current and transportation attributes of SSC. As the hydrodynamic conditions were unclear, hyperspectral remote sensing technique was an effective technical way for dynamic survey of DIN concentration. PMID:20698253

Zhang, Dong; Xu, Yong; Zhang, Ying; Li, Huan

2010-06-01

189

Cadmium distribution in sediment and the lugworm Arenicola marina in a low concentration exposure experiment  

SciTech Connect

In the central and southern North Sea, and in the Dutch coastal zone, total cadmium (Cd) concentrations in water are 0.02 {+-} 0.01 {mu}g/L and 0.06 {+-} 0.02 {mu}g/L, respectively Cadmium in the estuarine waters of the Dutch Wadden Sea varied from 0.3 {+-} 0.01 {mu}g/L in the western part to 0.08 {+-} 0.03 {mu}g/L in the eastern part. In whole sediment, the Cd background concentration for the Wadden Sea is 0.5 {+-} 0.01 {mu}g/g dry weight (dw), whereas the reference concentration is 0.08 {+-} 0.02 {mu}g/g dw. The concentrations of total-Cd in surface bulk sediments (0-2 cm) of the central North Sea (Oyster Grounds), and of intertidal mud-flats in the western Wadden Sea varied from 0.05 to 0.15 {mu}g/g dw and from 0.13 to 0.46 {mu}g dw, respectively (calculated from Kahn et al. 1992). These concentration ranges match the reference Cd concentration for Wadden Sea whole sediment (0.5 {+-} 0.01) {mu}g/g dw. Cadmium concentrations in surface sediments of the Dutch coastal zone and estuaries are only slightly elevated compared to the 0.2 {mu}g/g dw, considered as the background concentrations in pristine areas, but well below the level of 10 {mu}g/g dw at heavily contaminated sites. This laboratory study reports on the distribution of cadmium in the sediment column, and the uptake in the blood/coelomic fluid, intestine and body-wall of lugworms at low cadmium concentration exposure. The aim was to determine possible interaction between the vertical distribution of sediment-bound cadmium and the bioturbating activity of lugworms. 14 refs., 3 figs., 2 tabs.

Everaarts, J.M. [Netherlands Institute for Sea Research, Den Burg-Texel (Netherlands)] [Netherlands Institute for Sea Research, Den Burg-Texel (Netherlands); SaralaDevi, K. [National Institute of Oceanography, Kerala (India)] [National Institute of Oceanography, Kerala (India)

1996-12-31

190

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

191

Boron removal from seawater reverse osmosis permeate utilizing selective ion exchange resin  

Microsoft Academic Search

A minimum of boron in irrigation water is required for certain metabolic activities, but if its concentration is only slightly higher, plant growth will exhibit effects of boron poisoning, which are yellowish spots on the leaves and fruits, accelerated decay and ultimately plant expiration. Seawater in general contains relatively high concentration of boron: 4 to 5 ppm. The Red Sea

Nissim Nadav

1999-01-01

192

Reconstruction of Air Contaminant Concentration Distribution in a Two-dimensional Plane by Computed Tomography and Remote Sensing FTIR Spectroscopy  

Microsoft Academic Search

This research combined open path FTIR (OP-FTIR) technique and computed tomography (CT) to reconstruct air contaminant concentration distribution in a two-dimensional plane. Remote sensing FTIR instrument was used to scan radial beam geometry and obtain path integrated concentration (PIC) data of acetone gas in the measuring plane. Smooth basis function minimization (SBFM) algorithm was adopted to reconstruct gaseous concentration distribution.

Yibo Ren; Yan Li; Junde Wang; Xiaofei Wang; Bingping Liu; Liming Zhang; Lin Zhang

2005-01-01

193

Chemical Behaviors of Energetic Deuterium Implanted into Boron Coatings  

SciTech Connect

To study chemical behaviors of energetic deuterium implanted into boron coating deposited by boronization in fusion devices, two types of boron coating film deposited on silicon and IG-430U were prepared by Plasma Chemical Vapor Deposition (PCVD) technique. Boron polycrystal was used as the reference sample. The chemical behavior of deuterium was investigated by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal adsorption spectroscopy).The 1.0 keV D{sub 2}{sup +} ions were implanted into the samples and the deuterium desorption behavior was studied by TDS. The TDS spectra showed that there were two deuterium release peaks at around 550 and 750 K, which were attributed to the release from deuterium trapped by boron and carbon, respectively. It was also found that most of implanted deuterium was trapped in carbon trapping site compared with boron one.In XPS measurements, the chemical shift of B-1s towards positive side was observed in the film on IG-430U after D{sub 2}{sup +} ion implantation. However, no chemical shifts were found in the film on silicon and boron polycrystal. In highly concentrated boron materials, even if deuterium was implanted into the boron materials, the amount of B-D bond was too low to be measured by XPS. This suggests that deuterium implanted into highly pure boron materials wasn't almost trapped, so that the retention of deuterium in the boron materials would be reduced, compared that in carbon materials.

Kodama, H. [Shizuoka University (Japan); Morimoto, Y. [Shizuoka University (Japan); Sasaki, M. [Shizuoka University (Japan); Oyaidu, M. [Shizuoka University (Japan); Oya, Y. [University of Tokyo (Japan); Sagara, A. [National Institute for Fusion Science (Japan); Noda, N. [National Institute for Fusion Science (Japan); Okuno, K. [Shizuoka University (Japan)

2003-09-15

194

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

195

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.

2014-01-01

196

Estimation of pore size distribution using concentric double pulsed-field gradient NMR.  

PubMed

Estimation of pore size distribution of well calibrated phantoms using NMR is demonstrated here for the first time. Porous materials are a central constituent in fields as diverse as biology, geology, and oil drilling. Noninvasive characterization of monodisperse porous samples using conventional pulsed-field gradient (PFG) NMR is a well-established method. However, estimation of pore size distribution of heterogeneous polydisperse systems, which comprise most of the materials found in nature, remains extremely challenging. Concentric double pulsed-field gradient (CDPFG) is a 2-D technique where both q (the amplitude of the diffusion gradient) and ? (the relative angle between the gradient pairs) are varied. A recent prediction indicates this method should produce a more accurate and robust estimation of pore size distribution than its conventional 1-D versions. Five well defined size distribution phantoms, consisting of 1-5 different pore sizes in the range of 5-25 ?m were used. The estimated pore size distributions were all in good agreement with the known theoretical size distributions, and were obtained without any a priori assumption on the size distribution model. These findings support that in addition to its theoretical benefits, the CDPFG method is experimentally reliable. Furthermore, by adding the angle parameter, sensitivity to small compartment sizes is increased without the use of strong gradients, thus making CDPFG safe for biological applications. PMID:23548563

Benjamini, Dan; Nevo, Uri

2013-05-01

197

Identification of a novel system for boron transport: Atr1 is a main boron exporter in yeast.  

PubMed

Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that atr1Delta mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron resistant. In addition, atr1Delta cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular levels of the element. Furthermore, atr1Delta cells showed stronger boron-dependent phenotypes than mutants deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is required for boron tolerance. PMID:19414602

Kaya, Alaattin; Karakaya, Huseyin C; Fomenko, Dmitri E; Gladyshev, Vadim N; Koc, Ahmet

2009-07-01

198

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

199

Influence of dissolved-air concentration on spatial distribution of bubbles for sonochemistry.  

PubMed

The pulsation of ultrasonic cavitation bubbles at various dissolved-air concentration in a sonochemical reaction field of standing-wave type is investigated experimentally by laser-light scattering. When a thin light sheet, finer than half the wavelength of sound, is introduced into the cavitation bubbles at an antinode of sound pressure, the scattered light intensity oscillates. The peak-to-trough light intensity is correlated with the number of bubbles that contribute to the sonochemical reaction. It is shown that as the dissolved air concentration becomes higher, the weighted center of the spatial distribution of the peak-to-trough intensity tends to shift towards the liquid surface. At higher concentration of the dissolved air, a great deal of bubbles with size distribution generated due to coalescence between bubbles disturbs sound propagation to change the sound phase easily. A standing wave to trap tiny oscillating bubbles is established only at the side which is nearer to the liquid surface. Also at higher concentration, liquid flow induced by drag motion of bubbles by the action of radiation force becomes apparent and position-unstable region of bubble is enlarged from the side of sound source towards the liquid surface. Therefore, the position of oscillating bubbles active for sonochemical reaction is limited at the side which is nearer to the liquid surface at higher concentration of the dissolved air. PMID:16780909

Tuziuti, Toru; Yasui, Kyuichi; Sivakumar, Manickam; Iida, Yasuo

2006-12-22

200

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

201

The level and distribution of ²²?Rn concentration in soil-gas in Guangdong Province, China.  

PubMed

In order to understand the level and distribution of (220)Rn concentrations in soil-gas in the high-radiation-background area, an (220)Rn survey was carried out for the first time using a RAD7 portable radon monitor at 67 locations covering a total area of 1800 km(2) in the South of China. (220)Rn concentrations were significantly different from that in the surface areas covered by the weathered granite of Yanshan Period or Quaternary sediments. The (220)Rn concentrations varied between 6.65 and 461 kBq m(-3) and the averages were 294.42 ± 81.36 and 23.30 ± 25.84 kBq m(-3) for weathered granite products and sediments, respectively. A high positive correlation between (220)Rn concentrations and (232)Th activity concentrations was found. (220)Rn concentrations had no statistically significant variations from depths of 20-140 cm with an interval of 20 cm. It is worth paying attention to the problem of such a high soil (220)Rn concentration in Zhuhai City and Zhongshan City. PMID:22923249

Wang, N; Peng, A; Xiao, L; Chu, X; Yin, Y; Qin, C; Zheng, L

2012-11-01

202

Boron-Loaded Silicone Rubber Scintillators  

SciTech Connect

Silicone rubber received attention as an alternative to polyvinyltoluene in applications in which the scintillator is exposed to high doses because of the increased resistance of the rubber to the formation of blue-absorbing color centers. Work by Bowen, et al., and Harmon, et al., demonstrated their properties under gamma/x-ray irradiation, and Bell, et al. have shown their response to thermal neutrons. This last work, however, provided an example of a silicone in which both the boron and the scintillator were contained in the rubber as solutes, a formulation which led to the precipitation of solids and sublimation of the boron component. In the present work we describe a scintillator in which the boron is chemically bonded to the siloxane and so avoids the problem of precipitation and loss of boron to sublimation. Material containing up to 18% boron, by weight, was prepared, mounted on photomultipliers, and exposed to both neutron and gamma fluxes. Pulse height spectra showing the neutron and photon response were obtained, and although the light output was found to be much poorer than from samples in which boron was dissolved, the higher boron concentrations enabled essentially 100% neutron absorption in only a few millimeters' thickness of rubber.

Bell, Z.W.; Maya, L.; Brown, G.M.; Sloop, F.V.Jr

2003-05-12

203

Oxidation resistance of boronized CoCrMo alloy  

Microsoft Academic Search

Boronizing of CoCrMo alloy has been performed by means of a powder-pack method using commercial LSB powders at 850, 900 and 950°C for 8h, respectively. In this study, the boronized CoCrMo alloy before and after oxidation tests were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The distribution of alloy elements of boronized samples from surface to interior

Dong Mu; Bao-luo Shen

2010-01-01

204

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

205

Relationship between apolipoprotein C-III concentrations and high-density lipoprotein subclass distribution  

Microsoft Academic Search

High-density lipoprotein (HDL) subclasses have different antiatherogenic potentials and functional properties. This work presents our findings and discussions on their metabolic implications on apolipoprotein (apo) C-III together with other apolipoprotein levels and HDL subclass distribution profile. Apolipoprotein A-I contents of plasma HDL subclasses were quantitated by 2-dimensional gel electrophoresis coupled with immunodetection in 511 subjects. Concentrations of triglycerides and of

Li Tian; Jin Wu; Mingde Fu; Yanhua Xu; Lianqun Jia

2009-01-01

206

Permanent magnet synchronous motor with exterior-rotor : Distributed or concentrated windings – motor performance comparison  

Microsoft Academic Search

Purpose – The paper aims to present the comparison between the performances of the exterior-rotor permanent magnet synchronous motors with distributed windings and the performances of the exterior-rotor permanent magnet synchronous motors with concentrated windings. Design\\/methodology\\/approach – Finite element method is used for motors performance determination. The BLDC operation mode for the motors with different slot and pole number combination

Bojan Štumberger; Gorazd Štumberger; Miralem Hadžiselimovi?; Ivan Zagradišnik; Anton Hamler; Mladen Trlep

2006-01-01

207

Distribution, inegalite et concentration des revenus chez les immigrants ages au Canada, 1990  

Microsoft Academic Search

Bien qu'il existe d'abondantes etudes exposant les differences de revenu entre les immigrants et les autochtones ou entre les groupes d'immigrants eux meme, ces etudes ne tiennent pas compte de la distribution ni de la concentration des revenus. Comme ces deux aspects sont importants pour comprendre la repartition du bien-etre economique et le comportement des consommateurs chez ces groupes, ils

K. G. Basavarajappa

1999-01-01

208

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 ?\\cdotcm2 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

209

Analysis of boron-10 in soft tissue by dynamic secondary ion mass spectrometry.  

PubMed

We report here a preliminary study in which dynamic secondary ion mass spectrometry (SIMS) has provided images of boron-10 (10B) in biological tissue as used in research into boron neutron capture therapy. Cultured tumour cells incubated in media containing known concentrations of a 10B-containing compound, p-boronophenylalanine (BPA), and intracranial tumour tissue from animals previously injected with BPA were analysed by an in-house constructed SIMS. Investigations were conducted in positive secondary ion detection mode using a 25-keV, 5-nA gallium primary ion source. For calibration purposes, tissue standards were also analysed and their boron-to-carbon signal ratios correlated to bulk boron concentrations measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Ion maps of 10B, 12C, 23Na and 39K showing gross tissue and cell features were acquired. SIMS and ICP-AES standard measurements were in good agreement. Tissue regions with high or low 10B concentrations were identified along with 10B hotspots in normal brain areas. Cultured cells revealed the intracellular localization of 10B. SIMS is capable of producing images showing the distribution of 10B at p.p.m. levels in cells and in normal and tumour-bearing brain tissue. PMID:14678511

Oyedepo, A C; Brooke, S L; Heard, P J; Day, J C C; Allen, G C; Patel, H

2004-01-01

210

The Sorption Capacity of Boron on Anionic-Exchange Resin  

Microsoft Academic Search

Boron sorption capacities on anionic-exchange resins vary with temperature, concentration, and resin crosslinkage. A semiempirical correlation, developed from boron solution chemistry, is presented to account for these variations. The relationship, based on boron chemistry and changes in Gibb's energy, can be stated approximately as Q = a1CBz exp[-(a4T + a5T + a6z )]. Correlation parameters, which vary with resin type,

JIDONG LOU; GARY L. FOUTCH; JUNG WON NA

1999-01-01

211

The association between spatial distribution of common malignancies and soil lead concentration in Isfahan, Iran  

PubMed Central

Background: Malignancies are primarily environmental diseases mostly attributed to environmental factors. By plotting the prevalence and spatial distribution maps, important differences can be observed in detail. This study aimed to determine the association between map distribution of malignancies and the geological phenomena of lead (Pb) accumulation in soil in the province of Isfahan, Iran. Methods: Spatial distribution maps of malignant diseases were plotted by using data recorded during 2007 to 2009 in the Isfahan Cancer Registry Program. Data on Pb accumulation in soil was obtained from the National Geological Survey and Mineral Exploration. Pb concentrations were documented in three parts of agricultural, non-agricultural, urban, and industrial land. The geographical mapping of cancers and soil Pb were then incorporated into a geographic information system (GIS) to create a spatial distribution model. Results: The spatial distributions of ten common malignant diseases in the province, i.e. skin cancers, hematological malignancies, and breast cancers, followed by other malignancies were scattered based on Pb distribution. In fact, common cancers were more prevalent in the parts of the province where soil Pb was more abundant. Conclusion: The findings of this study underscore the importance of preventing Pb exposure and controlling industrial production of Pb. The data is also important to establish further effects modeling for cancers. Moreover, physicians and health professionals should consider the impact of environmental factors on their patients’ health.

Rashidi, Masoumeh; Rameshat, Mohammad Hossein; Gharib, Hadi; Rouzbahani, Reza; Ghias, Majid; Poursafa, Parinaz

2012-01-01

212

Strontium concentrations in corrosion products from residential drinking water distribution systems.  

PubMed

The United States Environmental Protection Agency (US EPA) will require some U.S. drinking water distribution systems (DWDS) to monitor nonradioactive strontium (Sr(2+)) in drinking water in 2013. Iron corrosion products from four DWDS were examined to assess the potential for Sr(2+) binding and release. Average Sr(2+) concentrations in the outermost layer of the corrosion products ranged from 3 to 54 mg kg(-1) and the Sr(2+) drinking water concentrations were all ?0.3 mg L(-1). Micro-X-ray adsorption near edge structure spectroscopy and linear combination fitting determined that Sr(2+) was principally associated with CaCO3. Sr(2+) was also detected as a surface complex associated with ?-FeOOH. Iron particulates deposited on a filter inside a home had an average Sr(2+) concentration of 40.3 mg kg(-1) and the associated drinking water at a tap was 210 ?g L(-1). The data suggest that elevated Sr(2+) concentrations may be associated with iron corrosion products that, if disturbed, could increase Sr(2+) concentrations above the 0.3 ?g L(-1) US EPA reporting threshold. Disassociation of very small particulates could result in drinking water Sr(2+) concentrations that exceed the US EPA health reference limit (4.20 mg kg(-1) body weight). PMID:23600992

Gerke, Tammie L; Little, Brenda J; Luxton, Todd P; Scheckel, Kirk G; Maynard, J Barry

2013-05-21

213

Concentration  

NSDL National Science Digital Library

This NCTM iOS app of the familiar online Illuminations game, "Concentration" (cataloged separately) 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.

2011-09-15

214

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

215

Local distribution of PM2.5 concentration over Osaka based on space and ground measurements  

NASA Astrophysics Data System (ADS)

This work intends to estimate PM2.5 concentration over mega city Osaka in Japan based on both satellite and ground measurements. Our work is composed of the following steps. At first the relationship between PM2.5 and aerosol optical thickness (AOT) is derived by using the ground measurements with sun photometer and PM-sampler, respectively. In addition vertical distribution of aerosol particles are also investigated by LIDAR measurements. The second step is to retrieve columnar AOT distribution from the space-based reflectance information with CAI (cloud aerosol imager) on GOSAT (greenhouse gases observing satellite). Note that, the PM2.5 measurements indicate the surface level concentration of the atmospheric particles, and hence the columnar AOT distribution should be converted to the surface level aerosol optical depth (AOD) based on the aerosol extinction profile with LIDAR. Finally, PM2.5 distribution is obtained from the relationship derived at the first step. The obtained results of PM2.5 are partially validated with the sampling data of PM2.5 at the surface.

Sano, Itaru; Mukai, Sonoyo; Nakata, Makiko; Sugimoto, Nobuo; Holben, Brent N.

2012-11-01

216

On-Road measurement of particulate matter emissions from vehicles: particle concentration, size distribution and morphology  

NASA Astrophysics Data System (ADS)

During summer 2010, we conducted a field experiment in Southern Michigan to measure on-road vehicle emissions. During the campaign, particulate matter (PM) concentrations were monitored with a Light Detection and Ranging (Lidar) and transmissometer system. The Lidar and transmissometer system measures PM mass concentration of vehicle exhaust using backscatter and extinction of an ultraviolet laser beam directed across the road. Collocated with the Lidar system we deployed an extractive system inclusive of a LiCor 840 to monitor CO2 concentrations, a laser aerosol spectrometer to measure particle size distributions for PM with diameter larger than 0.1 µm, and a portable condensation particle counter to estimate the total particle number concentration for particles with diameters between~30nm and 1 µm. In addition, road-side vehicle exhaust particles were collected on nuclepore filters for scanning electron microscopy analysis during selected periods of time. In this study we analyze fuel-based mass and number PM emission factors from passing vehicles. The emission factors are estimated normalizing the PM data by the CO2 concentration. The morphology of the particulates is also investigated with electron microscopy analysis. Type of vehicles and traffic counts were recorded by one of the researchers during the sampling period to evaluate the influence on particle morphology due to traffic volume and fuel type. Image processing and fractal geometry are used to estimate various morphological parameters and fractal dimension. Diurnal variation of particle morphology descriptors and fractal dimension of soot particles are investigated and compared with CO2 emissions, particle size distribution and particle number concentration for selected subsets of the data. Variations of PM emission factors and PM morphology are also investigated for different traffic conditions and days of the week. The analysis of the PM data is of particular importance in monitoring vehicle emissions and in designing emission reduction strategies to improve air quality and public health.

Salvadori, N.; China, S.; Cook, J.; Kuhns, H. D.; Moosmuller, H.; Mazzoleni, C.

2010-12-01

217

Nuclear reaction microanalysis of boron doped steels  

NASA Astrophysics Data System (ADS)

The microanalysis of trace amounts of boron has been carried out using a 1 ?m proton microbeam from the 3 MV single-ended electrostatic accelerator of TIARA facility, JAEA Takasaki. Steel specimens containing 20-100 ppm boron have been bombarded by 1.7 MeV proton beam for ?-ray detection and 1.32 MeV H2+ beam for ?-particles. The maps of boron distribution have been measured by detecting 428 keV ?-rays emitted from the 10B (p, ?'?) 7Be nuclear reaction and 3.7 MeV ?-particles from the 11B (p, ?) 8Be nuclear reaction. As a result of imaging, segregation of several micron sized boron precipitates could be clearly seen.

Shibata, H.; Kohno, Y.; Shibata, K.; Sato, T.; Oikawa, M.; Haga, J.; Sakai, T.

2007-07-01

218

CVD boron on calcium chromate powder  

SciTech Connect

This study was an experimental effort to improve the compositional homogeneity of a pyrotechnic mixture of boron and calcium chromate (CaCrO/sub 4/). Boron was deposited onto calcium chromate powders at 350/sup 0/C from a diborane and hydrogen gas mixture at a pressure of 40 torr by Chemical Vapor Deposition (CVD). The B:CaCrO/sub 4/ ratio of the coated powders was analyzed by inductively-coupled plasma spectroscopy and the distribution of the two phases was observed by electron microprobe analysis. The pyrotechnic activity was determined by differential thermal analysis. In addition to varying the composition of the mixture, an attempt was made to vary the boron distribution by coating both sized and unsized CaCrO/sub 4/ powders. Boron was deposited for 2 h onto sized CaCrO/sub 4/ powder, which resulted in a higher weight percentage of boron in comparison to the unsized powder. CVD coated CaCrO/sub 4/ powders began their pyrotechnic activity at an auto ignition temperature that was lower than the auto ignition temperature observed for mechanically blended mixtures. The coating of sized CaCrO/sub 4/ powder improved the uniformity of boron deposition of CaCrO/sub 4/, but it also decreased the pyrotechnic activity.

Coonen, R.M.

1984-09-01

219

The effective distribution system for the concentration of patients to extra-large hospitals  

PubMed Central

Purpose In Korean society, extra-large hospitals are congested with the majority of patients. Because of the congestions, the urgent patients need to wait anywhere from as short as a month to around three months. These concentrations of the patients on the extra-large hospitals causes not only the economic problem in terms of loss of opportunity cost and resources of other medium and large hospitals but also the fear and the consequential stress of the patients and the families of the patients who are waiting for the surgeries. The phenomenon of the concentrations derived due to the insufficient information to the medical consumers. If the information on medical treatment services such as surgery schedule is provided before the selection of hospital, we expect that the selection of hospital for the patients and their family will differ, resulting in redistribution of concentration phenomenon. In this paper, we propose and verify the effective distribution system for the concentration on the extra-large hospitals. Methods Web simulation survey was conducted. A total 100 respondents were divided into 4 groups of 25 respondents and the different information was provided to each group. Results Through multiple comparisons among groups, only group which was provided with both information about 'the difference of surgical results' and 'the waiting time for surgery', had difference in significance. Conclusion By providing two sets of information to patients, reckless selection of extra-large hospitals can be spread to more appropriate hospitals and therefore achieve effective distribution of the population concentration on extra-large hospital.

Hong, Du Pyo

2011-01-01

220

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

221

Pharmacokinetics in melanoma-bearing mice of 5-dihydroxyboryl-6-propyl-2-thiouracil (BPTU), a candidate compound for boron neutron capture therapy.  

PubMed

Blood pharmacokinetics and tissue distribution of 5-dihydroxyboryl-6-propyl-2-thiouracil (BPTU), a boron carrier with postulated melanin-seeking properties for boron neutron capture therapy, were determined in C57/BL mice with subcutaneous pigmented or non-pigmented B16 melanomas. Borocaptate sodium (BSH) was used as a boron compound without melanin-seeking properties in a comparative biodistribution study in the same animal tumour models. Administration of single doses showed that BPTU was retained better in the pigmented B16 tumour than in the non-pigmented variant. BPTU was found in large concentrations in kidney and liver. Brain boron was approximately 10-fold lower than tumour boron. On a molar basis, BPTU demonstrated higher affinity for B16 tumours than BSH. Owing to solubility limits, tumour boron concentrations in this mouse study were too low for effective application of BNCT. However, the high tumour-to-blood and tumour-to-normal tissues ratios indicate that, with appropriate formulation, BPTU could be a promising candidate for clinical BNCT. PMID:8142252

Verrijk, R; Smolders, I J; Huiskamp, R; Gavin, P R; Philipp, K H; Begg, A C

1994-04-01

222

Boron toxicity  

Microsoft Academic Search

Whilst of lesser prevalence than B deficient soils, B-rich soils are important, causing B toxicity in the field and decreased crop yields in different regions of the world. The highest naturally occurring concentrations of soil B are in soils derived from marine evaporites and marine argillaceous sediment. In addition, various anthropogenic sources of excess B may increase soil B to

Ross O. Nable; Gary S. Bañuelos; Jeffrey G. Paull

1997-01-01

223

Testing an agent-based model of bacterial cell motility: How nutrient concentration affects speed distribution  

NASA Astrophysics Data System (ADS)

We revisit a recently proposed agent-based model of active biological motion and compare its predictions with own experimental findings for the speed distribution of bacterial cells, Salmonella typhimurium. Agents move according to a stochastic dynamics and use energy stored in an internal depot for metabolism and active motion. We discuss different assumptions of how the conversion from internal to kinetic energy d( v) may depend on the actual speed, to conclude that d 2 v ? with either ? = 2 or 1 < ? < 2 are promising hypotheses. To test these, we compare the model's prediction with the speed distribution of bacteria which were obtained in media of different nutrient concentration and at different times. We find that both hypotheses are in line with the experimental observations, with ? between 1.67 and 2.0. Regarding the influence of a higher nutrient concentration, we conclude that the take-up of energy by bacterial cells is indeed increased. But this energy is not used to increase the speed, with 40 ?m/s as the most probable value of the speed distribution, but is rather spend on metabolism and growth.

Garcia, V.; Birbaumer, M.; Schweitzer, F.

2011-08-01

224

Determination and Standardization of Analytical Conditions for Dissolved Boron in Coastal Waters of East Sea in Korea by ICP-OES  

Microsoft Academic Search

The analysis of metals in seawaters has been an important subject for many years. Achieving low-level detection limits as well as overcoming high matrix effect are requested in seawater analysis especially elements of interest are present in various chemical forms. Among them, boron is one of the widely distributed elements in nature and its concentrations of about 10 ppm in

H. Yoon; M. Shin; C. Yoon; J. Lee

2005-01-01

225

Modelling the distribution of detrital cosmogenic nuclide concentrations: a new tool to study drainage basin evolution.  

NASA Astrophysics Data System (ADS)

Cosmogenic nuclide concentrations (CNCs) in alluvial sediments are now routinely being used to estimate time- and space-averaged drainage basin denudation rates but have the potential to offer considerably more. This is because each grain leaving a drainage basin has a potentially unique history of erosion, transport and storage, meaning that the distribution of CNCs in large numbers of grains can provide an integrated signature of the basin's geomorphic history. We use a numerical model describing cosmogenic nuclide acquisition in sediments moving through an arid- zone drainage basin to explore the sensitivity of alluvial CNC distributions to assumptions about the geomorphic settings of the sediment's source areas. The model fully accounts for variations in nuclide production due to changes in latitude, altitude and topographic shielding and allows for spatially variable erosion and sediment transport rates. Data for model validation are provided by measurements of cosmogenic 21Ne concentrations in 32 16-22 mm diameter quartzite clasts from a 200 m reach of the Gaub river (a tributary of the Kuiseb, Namibia) along with measurements of cosmogenic 10Be in 12 amalgamated fluvial sediment samples from the outlets of the Gaub's tributaries. Model results show that detrital CNC distributions are highly sensitive to the geomorphic settings of the sediments' source areas and have the potential to be able to differentiate tectonic settings and/or geomorphic histories. The clast 21Ne concentrations vary between 2.6×106 and 1.6×108 atoms/g and exhibit a non-Gaussian distribution. The shape of this distribution, also predicted by the model, confirms the non-random nature of detrital CNC acquisition. These results also emphasise the importance of the assumptions made when using cosmogenic nuclides to estimate basin-wide denudation rates. The non- Gaussian distribution shows that the assumption of random inheritance of CNCs in the sediments cannot always be made, such that there may be scope for using this method for a priori estimates of inheritance that can be used in dating sedimentary deposits.

Codilean, A. T.; Hoey, T. B.; Bishop, P.; Stuart, F. M.; Fabel, D.; Willgoose, G. R.

2006-12-01

226

Boron-Doped Nanocrystalline Diamond.  

National Technical Information Service (NTIS)

A conductive boron doped nanocrystalline diamond is described. The boron doped diamond has a conductivity which uses the boron in the crystals as a charge carrier. The diamond is particularly useful for electrochemical electrodes in oxidation-reduction re...

G. M. Swain M. Witek P. Sonthalia Y. Show

2004-01-01

227

Distribution and concentrations of jumbo flying squid ( Dosidicus gigas) off the Peruvian coast between 1991 and 1999  

Microsoft Academic Search

Seasonal changes in the distribution and concentration of jumbo flying squid (Dosidicus gigas) off the Peruvian coast were assessed using catch and effort data from the jigging vessels that worked within the area between 1991 and 1999. The results showed a wide distribution of D. gigas along the coast, the highest concentrations occurred along the coast of northern Peru, from

Anatolio Taipe; Carmen Yamashiro; Luis Mariategui; Pablo Rojas; Cecilia Roque

2001-01-01

228

Role of RE Element Nd on Boronizing Kinetics of Steels  

NASA Astrophysics Data System (ADS)

Boronizing of AISI 1045 and ASTM W1-111/2 steels was carried out by pack boriding using Nd2O3-containing agent in the temperature range of 1053 to 1213 K. The effect of RE element Nd on boronizing kinetics was analyzed in terms of possible chemical reactions in boriding agent, surface elemental distribution and morphology evolution of the steels boronized at different temperatures. The results showed that the RE element Nd has two opposite effects on boronizing process, i.e., promoting effect at high temperatures and hindering effect at low temperatures. Boronizing using Nd2O3-containing agent can remarkably reduce the diffusion activation energy at higher temperatures. Empirical equations relating the boride layer thickness with processing time and temperature are established. Based on these equations, the contour diagrams of boride layer thickness for the studied steels boronized with addition of 5% Nd2O3 are presented.

Su, Z. G.; Lv, X. X.; An, J.; Yang, Y. L.; Sun, S. J.

2012-07-01

229

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

Microsoft Academic Search

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,

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

1999-01-01

230

BORLANMIAISI 1040 ÇEL ??? NN TRBOLOJK ÖZELLKLERNN ?NCELENMES ? INVESTIGATION OF TRIBOLOGICAL PROPERTIES OF BORONIZED AISI 1040 STEEL  

Microsoft Academic Search

In this paper, the tribological properties of AISI 1040 steel were researched. Samples were boronized in temperatures of 820°C, 860°C, 900°C in 2, 4 and 6 hour using Ekabor 2 powders by packed boriding method. Phases and depth of boronized samples were determined via microstructure analyses. Hardness distribution was detected depending on depth from surface. Tribological behaviours of boronizing samples

Simge GENÇALP

231

Influence of urban climate upon distribution of airborne Deuteromycete spore concentrations in Mexico City  

NASA Astrophysics Data System (ADS)

The effect of an urban climate upon the spatial and temporal distribution of Deuteromycete spores was studied during 1991 using Burkard volumetric spore traps in two areas of Mexico City with different degrees of urbanization. Deuteromycete conidia formed the largest component of the total airborne fungal spore load in the atmosphere of Mexico City, contributing 52% of the spores trapped in an urban-residential area (southern area) and 65% of those in an urban-commercial area (central area). Among the most common spore types, Cladosporium and Alternaria showed a marked seasonal periodicity with significant differences in concentration (P<0.05) between the dry and wet seasons. Maximum conidial concentrations were found during the end of the wet season and the beginning of the cool, dry season (October-December). Daily mean concentrations of the predominant airborne spore types did not differ significantly between the southern and central areas. Daily mean spore concentrations were significantly correlated (P<0.05) in southern and central areas with maximum temperature (south, r = -0.35 central, r = -0.40) and relative humidity (south, r = 0.43; central, r = 0.29) from the previous day. Moreover, multiple regression analysis of spore concentrations with several meteorological factors showed significant interactions between fungal spores, relative humidity and maximum temperature in both areas. The diurnal periodicity of Cladosporium conidia characteristically showed two or three peaks in concentration during the day at 0200-0400, 1400 and 2000-2200 hours, while that of Alternaria showed only one peak (1200 to 2000 hours) in both areas. Maximum concentrations of these spores generally occurred 2-4 h earlier in the southern than in the central area. The lag in reaching maximum concentrations in the central area probably resulted from differences in the local conditions between the study areas, and from spores transported aerially into the city from distant sources. The analysis of maximum hourly concentrations of Cladosporium and Alternaria spores during 1 month of the dry season (February), and another month of the wet season (September) showed significant differences between the two study areas. Environmental factors and sources (green areas) affected diurnal changes in conidial concentration in the southern area (urbanization index, UI, 0.25), but not in the central area (UI 0.97). In general, spore concentrations were greatest in the southern area when relative humidities were low, and temperatures and wind velocities were high. It was difficult to establish effects of climatic factors on the spore concentration in the city centre. This probably results from the large amounts of air pollution, the heat island phenomenon, and from the distant origin of trapped conidia obviating aerial transport. Nevertheless, the seasonal and diurnal distributions of conidia found were similar to those reported for other tropical regions of the world.

Calderón, C.; Lacey, J.; McCartney, A.; Rosas, I.

232

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

233

Branched polymeric media: boron-chelating resins from hyperbranched polyethylenimine.  

PubMed

Extraction of boron from aqueous solutions using selective resins is important in a variety of applications including desalination, ultrapure water production, and nuclear power generation. Today's commercial boron-selective resins are exclusively prepared by functionalization of styrene-divinylbenzene (STY-DVB) beads with N-methylglucamine to produce resins with boron-chelating groups. However, such boron-selective resins have a limited binding capacity with a maximum free base content of 0.7 eq/L, which corresponds to a sorption capacity of 1.16 ± 0.03 mMol/g in aqueous solutions with equilibrium boron concentration of ?70 mM. In this article, we describe the synthesis and characterization of a new resin that can selectively extract boron from aqueous solutions. We show that branched polyethylenimine (PEI) beads obtained from an inverse suspension process can be reacted with glucono-1,5-D-lactone to afford a resin consisting of spherical beads with high density of boron-chelating groups. This resin has a sorption capacity of 1.93 ± 0.04 mMol/g in aqueous solution with equilibrium boron concentration of ?70 mM, which is 66% percent larger than that of standard commercial STY-DVB resins. Our new boron-selective resin also shows excellent regeneration efficiency using a standard acid wash with a 1.0 M HCl solution followed by neutralization with a 0.1 M NaOH solution. PMID:22827255

Mishra, Himanshu; Yu, Changjun; Chen, Dennis P; Goddard, William A; Dalleska, Nathan F; Hoffmann, Michael R; Diallo, Mamadou S

2012-08-21

234

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

235

Effect of boron on the development of brown rot ( Monilinia laxa) on peaches  

Microsoft Academic Search

Requirements of consumers for products with low residues of pesticides have increased the need for alternative disease management practices. The concentration of boron in fruit affects its quality, shelf life and the development of physiological disorders. However, the effect of boron on the susceptibility of peach to fruit rots has not been reported. This study investigated the effect of boron

T. Thomidis; E. Exadaktylou

2010-01-01

236

Roles of ATR1 paralogs YMR279c and YOR378w in boron stress tolerance  

SciTech Connect

Highlights: {yields} ATR1 paralog YMR279c plays role in boron detoxification. {yields} YMR279c overexpression lowers cytoplasmic boron levels. {yields} ATR1 paralog YOR378w has no roles in boron stress response. -- Abstract: Boron is a necessary nutrient for plants and animals, however excess of it causes toxicity. Previously, Atr1 and Arabidopsis Bor1 homolog were identified as the boron efflux pump in yeast, which lower the cytosolic boron concentration and help cells to survive in the presence of toxic amount of boron. In this study, we analyzed ATR1 paralogs, YMR279c and YOR378w, to understand whether they participate in boron stress tolerance in yeast. Even though these genes share homology with ATR1, neither their deletion rendered cells boron sensitive nor their expression was significantly upregulated by boron treatment. However, expression of YMR279, but not YOR378w, from the constitutive GAPDH promoter on a high copy plasmid provided remarkable boron resistance by decreasing intracellular boron levels. Thus our results suggest the presence of a third boron exporter, YMR279c, which functions similar to ATR1 and provides boron resistance in yeast.

Bozdag, Gonensin Ozan; Uluisik, Irem; Gulculer, Gulce Sila; Karakaya, Huseyin C. [Izmir Institute of Technology, Department of Molecular Biology and Genetics, 35430 Urla, Izmir (Turkey)] [Izmir Institute of Technology, Department of Molecular Biology and Genetics, 35430 Urla, Izmir (Turkey); Koc, Ahmet, E-mail: ahmetkoc@iyte.edu.tr [Izmir Institute of Technology, Department of Molecular Biology and Genetics, 35430 Urla, Izmir (Turkey)] [Izmir Institute of Technology, Department of Molecular Biology and Genetics, 35430 Urla, Izmir (Turkey)

2011-06-17

237

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

238

Measurement technique for methane concentration by wavelength scanning of a distributed-feedback laser  

NASA Astrophysics Data System (ADS)

A new technique which takes advantage of distributed-feedback (DFB) laser wavelength scanning to measure methane concentration is presented. A wavelength scan of the methane absorption peak at 1665.9 nm is realized using sawtooth modulation of the current injected to a DFB laser. A reference methane gas cell is used to find the methane absorption peak around 1666 nm, and normalization is used to reduce outside influences such as power drift and fiber loss. The concentration is derived by arithmetic processing of the absorption coefficient of the methane gas. An application test is carried out in a coal mine and a long-term precision of 0.05% is achieved.

Wang, H.; Wang, Q.; Chang, J.; Zhang, X.; Zhang, S.; Ni, J.

2008-04-01

239

Imaging the Proton Concentration and Mapping the Spatial Distribution of the Electric Field of Catalytic Micropumps  

NASA Astrophysics Data System (ADS)

Catalytic engines can use hydrogen peroxide as a chemical fuel in order to drive motion at the microscale. The chemo-mechanical actuation is a complex mechanism based on the interrelation between catalytic reactions and electro-hydrodynamics phenomena. We studied catalytic micropumps using fluorescence confocal microscopy to image the concentration of protons in the liquid. In addition, we measured the motion of particles with different charges in order to map the spatial distributions of the electric field, the electrostatic potential and the fluid flow. The combination of these two techniques allows us to contrast the gradient of the concentration of protons against the spatial variation in the electric field. We present numerical simulations that reproduce the experimental results. Our work sheds light on the interrelation between the different processes at work in the chemomechanical actuation of catalytic pumps. Our experimental approach could be used to study other electrochemical systems with heterogeneous electrodes.

Farniya, A. Afshar; Esplandiu, M. J.; Reguera, D.; Bachtold, A.

2013-10-01

240

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

241

The response of atmospheric methane concentrations to meteorological forcings of wetland distribution and extent  

NASA Astrophysics Data System (ADS)

Both wetland extent and distribution across the globe are estimated on seasonal and inter-annual timescales in the Simple Biosphere Model. The method is presented and the results are compared with estimates of inundated extent from remote sensing. A model of methane production and consumption is parameterized with data from eddy-covariance measurements of surface methane exchange. Scaled by modeled wetland areas, global patterns of methane emission from wetlands are produced. Modeled methane emissions, along with EDGAR inventories of anthropogenic methane emissions and GFED estimates of methane emissions from biomass burning, drive the GEOS-Chem chemical transport model; producing estimates of atmospheric methane concentrations.

Kraus, P. M.; Denning, A.

2013-12-01

242

The concentrations, distribution and sources of PAHs in agricultural soils and vegetables from Shunde, Guangdong, China  

Microsoft Academic Search

The concentrations, distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in 30 agricultural\\u000a soil and 16 vegetable samples collected from subtropical Shunde area, an important manufacturing center in China. The total\\u000a PAHs ranged from 33.7 to 350 ?g\\/kg in soils, and 82 to 1,258 ?g\\/kg in vegetables. The most abundant individual PAHs are phenanthrene,\\u000a fluoranthene, chrysene, pyrene and benzo(b)fluoranthene

Yong Tao Li; Fang Bai Li; Jun Jian Chen; Guo Yi Yang; Hong Fu Wan; Tian Bin Zhang; Xiao Duo Zeng; Jian Ming Liu

2008-01-01

243

Spectrochemical analysis of boron carbide by powder techniques. Final report  

Microsoft Academic Search

A method for the determination of impurities in boron carbide was developed using powder techniques. The elements aluminum, calcium, iron, magnesium, manganese, nickel, silicon, titanium, and vanadium were determined over concentration ranges between 10 and 24,000 parts per million. The boron carbide powder was mixed with buffers including an internal standard. These sample mixtures were excited in a direct current

B. H. Strauss; F. G. Howell

1977-01-01

244

Coprecipitation and isotopic fractionation of boron in modern biogenic carbonates  

Microsoft Academic Search

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

Avner Vengosh; Yehoshua Kolodny; Abraham Starinsky; Allan R. Chivas; Malcolm T. McCulloch

1991-01-01

245

Successive saturation of carbon steels with aluminum and boron  

Microsoft Academic Search

1.Boronizing of aluminized steel is expedient in the case in which the aluminum content of the coating does not exceed the concentration in Fe3Al. Boronizing should be conducted at temperatures of 1000° and higher.2.Alloying of FeB and Fe2B with aluminum reduces the microhardness and increases the ductility of the coating.

N. G. Kaidash; P. P. Chastokolenko; L. N. Chastokolenko

1982-01-01

246

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

247

Boron removal from drinking water with a boron selective resin: is the treatment really selective?  

Microsoft Academic Search

Drinking water and even mineral water may contain boron until a few ppm and WHO has recommended a limit of 0.3mg boronl?1. The treatment by the resin Amberlite IRA743 seems to be the most convenient. Water deboronation with this resin has been revisited through laboratory column experiments, especially for low boron concentrations. Given that the resin bears weakly basic anion

Marie-Odile Simonnot; Christophe Castel; Miguel NicolaÏ; Christophe Rosin; Michel Sardin; Henri Jauffret

2000-01-01

248

Boronization in textor  

NASA Astrophysics Data System (ADS)

The liner and limiters of TEXTOR have been coated in situ with a boron containing carbon film using a RG discharge in a throughflow of 0.8 He + 0.1 B 2H 6 +0.1 CH 4. The average film thickness was 30-50 nm, the ratio of boron and carbon in the layer was about 1:1 according to Auger Electron Spectroscopy. Subsequent tokamak discharges are characterized by a small fraction of radiated power (< 0.3) even during high power ICRF heating (2.6 MW, 1.6 s). A concomitant strong increase of the convective power loading of the limiters is observed. Values of Z eff lower than 1.2 are derived from conductivity measurements. The most prominent change in the impurity concentration compared to good conditions in a carbonized surrounding is measured for oxygen. The value OVI/ n¯e of the OVI intensity normalized to the averaged plasma density overlinene decreases by more than a factor of four. The decrease in the oxygen content manifests itself also as a reduction of the CO and CO 2 partial pressures measured during and after the discharge with a sniffer probe. The carbon levels are reduced by a factor of about two as measured by the normalized intensity CII/ overlinene of the CII line and via the ratio of the C fluxes and deuterium fluxes measured at the limiter (CI/D ?). The wall shows a pronounced sorption of hydrogen from the plasma, easing the density control and the establishment of low recycling conditions. The beneficial conditions did not show a significant deterioration during more than 200 discharges, including numerous shots at ICRH power levels > 2 MW.

Winter, J.; Esser, H. G.; Könen, L.; Philipps, V.; Reimer, H.; Seggern, J. v.; Schlüter, J.; Vietzke, E.; Waelbroeck, F.; Wienhold, P.; Banno, T.; Ringer, D.; Vep?ek, S.

1989-04-01

249

Environmental boron contamination in waters of Hisarcik area in the Kutahya Province of Turkey.  

PubMed

Our aim was to determine boron levels in waters of rich boron mine areas in Turkey. There is a naturally occurring high level of boron in the ground waters of some parts of Turkey. Our study area is Hisarcik village in the Kutahya Province of Turkey which has a large number of boron mines. Boron occurs in combined form, usually borax (Na2B4O7 x 10H2O) and colemanite (Ca2B6O11 x 5H2O). Water samples were collected from many springs in order to determine boron concentrations and the amount of boron that is exposed to 88 samples from the drinking water (tap water), 37 from ground water and 257 from stream or pond water (surface water). Urine samples taken from 42 residents in this area were analyzed for boron and compared with its levels in drinking waters. The inductively coupled plasma/mass spectrometry (ICP/MS) method was used for the analysis of boron concentrations. Water boron contents at differing locations of this area ranged from 2.05 to 29.00 mg B/l. Mean value of boron was 10.20+/-4.08 mg B/l. Total urinary boron excretion was ranged from 0.04 to 50.70 mg B/l and mean value was 8.30+/-10.91 mg B/l. Current information on sources, occurrence, pollution potential and toxicity of environmental boron is discussed. PMID:12909276

Cöl, Meltem; Cöl, Cavit

2003-10-01

250

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

251

Roles of ATR1 paralogs YMR279c and YOR378w in boron stress tolerance  

Microsoft Academic Search

Boron is a necessary nutrient for plants and animals, however excess of it causes toxicity. Previously, Atr1 and Arabidopsis Bor1 homolog were identified as the boron efflux pump in yeast, which lower the cytosolic boron concentration and help cells to survive in the presence of toxic amount of boron. In this study, we analyzed ATR1 paralogs, YMR279c and YOR378w, to

Gonensin Ozan Bozdag; Irem Uluisik; Gulce Sila Gulculer; Huseyin C. Karakaya; Ahmet Koc

2011-01-01

252

A new methodology for removal of boron fro by coal and fly ash  

Microsoft Academic Search

High levels of boron concentrations in water present a serious problem for domestic and agriculture utilizationsThe recent EU drinking water directive defines an upper limit of 1 mgB\\/l. In addition, most crops are sensitive to boron levels >0.75 mg\\/l in irrigation water. The boron problem is magnified by the partial (-60%) removal of boron in reverse osmosis (RO) desalination due

H. Polat; A. Vengoshb; I. Pankratovb; M. Polat

253

A new methodology for removal of boron from water by coal and fly ash  

Microsoft Academic Search

High levels of boron concentrations in water present a serious problem for domestic and agriculture utilizations.The recent EU drinking water directive defines an upper limit of 1 mgB\\/l. In addition, most crops are sensitive to boron levels >0.75 mg\\/1 in irrigation water. The boron problem is magnified by the partial (?60%) removal of boron in reverse osmosis (RO) desalination due

H. Polat; A. Vengosh; I. Pankratov; M. Polat

2004-01-01

254

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

255

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.

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

2012-01-01

256

Distribution of genetic marker concentrations for fecal indicator bacteria in sewage and animal feces.  

PubMed

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 log(10) 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; Shanks, Orin C

2012-06-01

257

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

258

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

259

Trends in ozone concentration distributions in the UK since 1990: Local, regional and global influences  

NASA Astrophysics Data System (ADS)

Data from the UK automatic monitoring network have been analysed to investigate average trends in ozone concentrations, concentration distributions and exceedences of the public information threshold (180 ?g m -3) at 13 rural sites (over the period 1990-2006) and at five urban sites (over the period 1993-2006) throughout the UK. The data indicate that the observations at a given location in the UK can be influenced by a combination of global (hemispheric)-, regional- and local-scale effects. As a result, the observed trend in the ozone metrics is determined from the net trend of these three influences, the relative contributions of which can vary both spatially and temporally. Specifically, the data reflect the following three major influences: (i) a gradual increase in the hemispheric baseline ozone concentration resulting from global-scale effects, thereby influencing the baseline levels of ozone brought into the UK from the Atlantic Ocean; (ii) substantial short-term elevations in ozone concentrations during summertime episodes, resulting from the formation of additional ozone from regional-scale photochemical processing of emitted VOC and NO x over north-west Europe, with such events tending to be more frequent and intense towards the south and east of the UK. On average, the severity of such events has progressively decreased since about 1990, as a result of EU controls of anthropogenic VOC and NO x emissions; and (iii) local-scale removal of ozone by direct reaction with emitted NO has gradually decreased, as a result of the control of NO x emissions. This has resulted in a general increasing influence on ozone concentrations since about 1990, which is most apparent at urban sites, where NO x emissions are higher, but also influences the observations at the majority of rural locations.

Jenkin, Michael E.

260

How to study boron biodistribution in liver metastases from colorectal cancer.  

PubMed

The purpose of this study was to evaluate boron distribution for a safe and effective BNCT (Boron Neutron Capture Therapy) of liver metastases. Samples both from healthy and tumour liver parenchyma were analysed, after i.v. boron administration, by: alpha particles counting under neutron irradiation; morphological analysis by standard haematoxylin-eosin staining; neutron autoradiography. Our method was unaffected by the cytological heterogeneity inside tumour nodules; it demonstrated selective boron distribution in tumour tissue and predicted estimated mean therapeutic doses in tumour and safety doses in healthy tissue. The time interval for efficient BNCT was 2 to 4 hours after i.v. boron administration. PMID:15675469

Roveda, L; Prati, U; Bakeine, J; Trotta, F; Marotta, P; Valsecchi, P; Zonta, A; Nano, R; Facoetti, A; Chiari, P; Barni, S; Pinelli, T; Altieri, S; Braghieri, A; Bruschi, P; Fossati, F; Pedroni, P

2004-11-01

261

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

262

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.

2011-01-01

263

The investigation of parameters affecting boron removal by electrocoagulation method.  

PubMed

Boron removal from wastewaters by electrocoagulation using aluminum electrode material was investigated in this paper. Several working parameters, such as pH, current density, boron concentration and type and concentration of supporting electrolyte were studied in an attempt to achieve a higher removal capacity. The experiments were carried out by keeping the pH of solution constant and optimum pH of solution was determined 8.0 for the aluminum electrode. Although energy consumption increased with decreasing boron concentration, which conductivity of these solutions were low, boron removal efficiency was higher at 100 mg/L than that of 1000 mg/L. Current density was an important parameter affecting removal efficiency. Boron removal efficiency and energy consumption increased with increasing current density from 1.2 to 6.0 mA/cm2. The types of different supporting electrolyte were experimented in order to investigate to this parameter effect on boron removal. The highest boron removal efficiency, 97%, was found by CaCl2. Added CaCl2 increased more the conductivity of solution according to other supporting electrolytes, but decreased energy consumption. The results showed to have a high effectiveness of the electrocoagulation method in removing boron from aqueous solutions. PMID:15985328

Yilmaz, A Erdem; Boncukcuo?lu, Recep; Kocakerim, M Muhtar; Keskinler, Bülent

2005-10-17

264

Distribution of Airborne Radon-222 Concentrations in U.S. Homes  

NASA Astrophysics Data System (ADS)

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 an arithmetic mean of 1.5 picocurie per liter (55 becquerels per cubic meter) and a long tail with 1 to 3% of homes exceeding 8 picocuries per liter, or by a geometric mean of 0.9 picocurie per liter and a geometric standard deviation of about 2.8. The standard deviation in the means is 15%, estimated from the number and variability of the available data sets, but the total uncertainty is larger because these data may not be representative. Available dose-response data suggest that an average of 1.5 picocuries per liter contributes about 0.3% lifetime risk of lung cancer and that, in the million homes with the highest concentrations, where annual exposures approximate or exceed those received by under-ground uranium miners, long-term occupants suffer an added lifetime risk of at least 2%, reaching extraordinary values at the highest concentrations observed.

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

1986-11-01

265

Minerals Yearbook 1989: Boron  

Microsoft Academic Search

U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position

Lyday

1990-01-01

266

[The reconstruction of two-dimensional distributions of gas concentration in the flat flame based on tunable laser absorption spectroscopy].  

PubMed

The experimental method by using the tunable diode laser absorption spectroscopy combined with the model and algo- rithm was studied to reconstruct the two-dimensional distribution of gas concentration The feasibility of the reconstruction program was verified by numerical simulation A diagnostic system consisting of 24 lasers was built for the measurement of H2O in the methane/air premixed flame. The two-dimensional distribution of H2O concentration in the flame was reconstructed, showing that the reconstruction results reflect the real two-dimensional distribution of H2O concentration in the flame. This diagnostic scheme provides a promising solution for combustion control. PMID:23387144

Jiang, Zhi-Shen; Wang, Fei; Xing, Da-Wei; Xu, Ting; Yan, Jian-Hua; Cen, Ke-Fa

2012-11-01

267

Magnetron sputtered boron films  

DOEpatents

A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence. 8 figs.

Makowiecki, D.M.; Jankowski, A.F.

1998-06-16

268

Impairment of Growth and Immune Function of Avocet Chicks from Sites with Elevated Selenium, Arsenic, and Boron.  

National Technical Information Service (NTIS)

Avocet chicks hatched from eggs collected from the south Central Valley of California were studied to determine the impact of elevated concentrations of selenium, boron, and arsenic on the immune system and growth to maturity. Selenium, arsenic, and boron...

A. Fairbrother M. Fix T. O'Hara C. A. Ribic

1994-01-01

269

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

PubMed

In this investigation, 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 microm. 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 P(M2.5) 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 microm. 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. PMID:17004679

Yi, Honghong; Hao, Jiming; Duan, Lei; Li, Xinghua; Guo, Xingming

2006-09-01

270

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

271

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

272

Process for microwave sintering boron carbide  

Microsoft Academic Search

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

C. E. Holcombe; M. S. Morrow

1993-01-01

273

Metal concentrations and distribution in the household, stairs and entryway dust of some Egyptian homes  

NASA Astrophysics Data System (ADS)

Household, stairs and entryway dust samples were collected from 16 houses distributed across Greater Cairo by using vacuum cleaner and sweeping methods during summer season of 2009. Lead (Pb), nickel (Ni), cadmium (Cd), aluminum (Al), iron (Fe), zinc (Zn), cobalt (Co), chromium (Cr) and copper (Cu) were measured in different dust particle sizes: <38 ?m, >38-45 ?m and >45-63 ?m. The highest average concentrations of Pb, Ni, Cd, Co, Cu, and Cr in different particle sizes were found in entryway followed by household and stairs. Al, Fe and Zn concentrations followed the pattern of entryway > stairs > household. Pb, Ni, Cd, Zn, Co and Cr were found in significantly (p < 0.01) higher concentrations in dust of the small particle size (<38 ?m), whereas Al, Fe and Cu were detected in significantly (p < 0.01) higher concentrations in dust of the large particle size (>45-63 ?m). The average concentrations of the individual metals in dust of the small particle size (<38 ?m) were 268, 196.4 and 254.49 ?g gm-1 for Pb, 49.6, 43.5 and 46.66 ?g gm-1 for Ni, 2.86, 2.15 and 2.71 ?g gm-1 for Cd, 4340, 3796 and 2602 ?g gm-1 for Al, 2860, 2200 and 2004 ?g gm-1 for Fe, 209.25, 152.3 and 103.26 ?g gm-1 for Zn, 4.1, 2.88 and 1.96 ?g gm-1 for Co, 85.99, 74.06 and 83.17 ?g gm-1 for Cr and 168.2, 156.5 and 122.02 ?g gm-1 for Cu in entryway, stairs and household, respectively. The mean concentrations of Cu and Pb in the entryway, stairs and household dust exceeded the maximum permissible limit 100 ?g gm-1 for Cu and Pb in soil. The highest concentrations of Pb, Cd, Co and Ni were found in urban areas, Al and Fe in the residential areas, and Cu, Zn and Cr in the residential near to industrial area. Significant positive correlation (p < 0.001) were found between the metal concentrations in household and entryway dust, indicating that the metals in household dust may be derived from outdoor sources in addition to dust generated within the house itself. The contribution of anthropogenic sources, especially traffic emission, to metal levels in household, entryway and stairs dust was reflected by the high values of enrichment factors for Pb, Cd, Zn and Cu and Ni and Cr in fine dust particle compared to the average crustal composition. Insignificant positive correlation coefficients were found between the concentrations of Pb and other metals in household dust. However, the correlation coefficients between the concentrations of Cd, Ni, Cr, Cu, Zn and Fe were statistically significant.

Hassan, Salwa Kamal Mohamed

2012-07-01

274

Microwave sintering of boron carbide  

Microsoft Academic Search

A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

R. D. Blake; J. D. Katz; J. J. Petrovic; H. Sheinberg

1988-01-01

275

Effects of Boron Doping on the Properties of Ultrananocrystalline Diamond Films  

NASA Astrophysics Data System (ADS)

Boron-doped ultrananocrystalline diamond (UNCD) films were fabricated on silicon substrates by microwave plasma chemical vapor deposition. UNCD films containing different concentrations of boron were prepared by using trimethylboron (B(CH3)3, TMB) as boron doping source and varying the amount of boron in the gas mixture from 0 ppm to 1000 ppm. The effects of boron doping on morphology, lattice parameter, phase composition, crystal size, and residual stress of UNCD films were investigated. No obvious change of the morphology was observed on doping with boron, and all the films had the UNCD crystal grains. Boron doping enhanced (111) growth. The preferred growth direction of the UNCD films was . Residual tensile stress was present in all the films, and increased with increasing the amount of boron in the gas mixture.

Yuan, Wen-Xiang; WU, Q. X.; Luo, Z. K.; Wu, H. S.

2014-04-01

276

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

277

[Hemoglobin concentration, hematocrit and leukocyte distribution pattern in children with Down's syndrome].  

PubMed

Sixty-two children with Down's syndrome and twenty-five healthy children, aged 3 months to 10 years, were studied. It was found that the hematocrit values and concentrations of hemoglobin in Down's syndrome were insignificantly higher than in healthy children, while their leukocyte count was slightly lower. The leukocyte distribution patterns in children with Down's syndrome, aged 3 months to 3 years, were similar to those in healthy children. However, children aged 3.5-10 years with Down's syndrome had a slightly higher percentage of neutrophiles and a significantly lower percentage of lymphocytes. The percentage of E-rosette-forming cells and count of T-lymphocyte forming these rosettes in Down's syndrome were significantly lower than in healthy children. PMID:8692603

Bartelik, S

1995-06-01

278

Elastic-Plastic Response of Rooftop Frames to Distributed and Concentrated Shock Load: Experimental Results and Theoretical Predictions.  

National Technical Information Service (NTIS)

Aluminum and mild steel rooftop frames were subjected to distributed and concentrated impulsive loads respectively. It has been observed that the location of the point of application of the load and the presence of attached extra mass has significant effe...

M. S. J. Hashmi

1984-01-01

279

Isolation and characterization of indigenous Streptomyces and Lentzea strains from soils containing boron compounds in Argentina.  

PubMed

The Salta Province - in the northwest of Argentina - is the main worldwide producer of hydroboracite and leads in exports of boron mineral and its derivatives in Latin America. In addition to the natural presence of boron compounds in the soils, there are others contaminated due to the boron mining industry. Although some bacteria are known to require boron for their growth or to be capable of storing boron, no studies have been published about Streptomyces or Lentzea genera's capacity to tolerate high boron concentrations, or about their metabolic capacities in boron contaminated environments. The results of this research show the isolation and molecular characterization of eight strains belonging to the actinobacteria phylum collected from different soils contaminated with high boron concentration in Salta state. The boron tolerance assays, which show that three of the strains were able to tolerate up 60-80?mM boron, demonstrate the potential capability of this group of bacteria to grow and maybe to remove boron from the environment. They appear to be promising, considering that these microorganisms are infrequent pathogens, are metabolically versatile and many Streptomyces can synthesize boron containing metabolites. PMID:23686918

Moraga, Norma Beatriz; Poma, Hugo Ramiro; Amoroso, María Julia; Rajal, Verónica Beatriz

2014-06-01

280

Concentration profiles and spatial distribution of perfluoroalkyl substances in an industrial center with condensed fluorochemical facilities.  

PubMed

Jiangsu Hi-tech Fluorochemical Industry Park, China, is one of the largest fluorochemical industry centers in Asia and could be a point source of polyfluoroalkyl substances (PFASs) to the surrounding environment. Besides water, sediment and soil samples, tree leaves and bark were also collected to monitor airborne PFASs around the facilities. Perfluorooctanoic acid and short-chain perfluorocarboxylates including perfluorohexanoic acid and perfluoropentanoic acid were found predominantly in all the samples. The target ?PFASs were distributed in the dissolved phase with a proportion of 96.5±2.9%. High concentrations of ?PFASs (up to 12,700ng/L in surface water) were found at sites near and within the wastewater treatment plant and the facilities. The ?PFASs in the sediment/sludge were in the range of 3.33-324ng/gdw. For the first time, tree samples were used for bio-monitoring airborne PFASs in the environment. The ?PFASs in the tree leaf and bark samples were in the range of 10.0-276 and 6.76-120ng/gdw, respectively. The spatial distribution of ?PFASs in the tree leaves suggested that airborne PFASs could be transported from the center to the surrounding environment by prevailing wind. PMID:24867700

Shan, Guoqiang; Wei, Mingcui; Zhu, Lingyan; Liu, Zhengtao; Zhang, Yahui

2014-08-15

281

Image reconstruction of 2D concentration distribution of particle flow with extinction optical tomography  

NASA Astrophysics Data System (ADS)

Optical tomography, as a novel technique developed recently, has drawn more and more interest among imaging of biology tissue, astronomy and industrial process monitoring, and so on. Extinction method is one of traditional measurement for particle concentration, which can be improve a novel optical measurement with computed tomography (CT) to reconstruct image of particle concentration distribution. In this paper, the theoretical model of exctinction optical tomography was presented, the relationship between geometric structure of optical array sensors and section drawings of measured area was analyzed, and so did between the structure and spatial resolution. In experiments, 8 x 8 orthogonal array of optical sensors with two-directions projection are used for flow imaging by means of FBP, which is for capturing movement track of a glass canaliculus with arenaceous quartz inside in a section. Furthermore, image reconstructions based on optical array sensors with two-directional angles and four-directional angles are simulated numerically and some significant results can be found from the simulated results.

Li, Yang; Wang, Renhuang; Zheng, Yingna

2003-09-01

282

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

283

Particle size distribution and PAH concentrations of incense smoke in a combustion chamber.  

PubMed

The particle size distribution and the concentrations of polycyclic aromatic hydrocarbons (PAHs) in incense smoke were studied using a custom-designed combustion chamber. Among the nine types of incense investigated, the particle and the total PAH emission factors varied significantly. The average mass median aerodynamic diameter (MMAD) of the smoke aerosol was 262+/-49nm, which positively correlated to particle emission factor (mg/stick, p<0.05). Coagulation was a major mechanism that dictates the MMAD of the smoke. The total toxic equivalency (the sum of the benzo[a]pyrene equivalent concentration) of the solid-phase PAHs (S-PAHs) was over 40 times higher than that of the corresponding gas-phase PAHs, indicating that the S-PAHs in incense smoke may pose potential health risk. Experiments show that each lowered percentage of total carbon content in the raw incense helped decrease the particle emission factor by 2.6mg/g-incense, and the reduction of S-PAH emission factor ranged from 8.7 to 26% when the carbon content was lowered from 45 to 40%. PMID:17014940

Yang, Chi-Ru; Lin, Ta-Chang; Chang, Feng-Hsiang

2007-01-01

284

Influence Of Low Boron Core Design On PWR Transient Behavior  

SciTech Connect

In conventional pressurized water reactor (PWR) designs, the concentration of boron in primary coolant is limited by the requirement of having a negative moderator density coefficient. As high boron concentrations have significant impact on reactivity feedback properties, design changes to reduce boron concentration in the reactor coolant are of general interest in view of improving PWR inherent safety. In the framework of an investigation into the feasibility of low boron design, a PWR core configuration based on fuel with higher gadolinium (Gd) content has been developed which permits to reduce the natural boron concentration at begin of cycle (BOC) by approx. 50% compared to current German PWR technology. For the assessment of the potential safety advantages, a Loss-of-Feedwater Anticipated Transient Without Scram (ATWS LOFW) has been simulated with the system code ATHLET for two PWR core designs: a low boron design and a standard core design. The most significant difference in the transient performance of both designs is the total primary fluid mass released through the pressurizer (PRZ) valves. It is reduced by a factor of four for the low boron reactor, indicating its improved density reactivity feedback. (authors)

Aleksandrov Papukchiev, Angel; Yubo Liu [Technical University Munich, Arcisstrasse 21, 80333 Muenchen (Germany); Schaefer, Anselm [ISaR Institute for Safety and Reliability, Walther-Meissner-Str. 2 85748 Garching (Germany)

2006-07-01

285

Boron reclamation from neoprene matrix. Final report  

SciTech Connect

A process to recover enriched boron crystalline powder from a neoprene matrix was developed on a laboratory basis and was adapted for use in a reclamation facility. The process includes pyrolysis to break down the polymer, acid leaching to purify the powder, and dry sieving to adjust the particle size distribution of the powder. An estimated 98% of the powder is recovered.

Asper, G.R.

1982-12-01

286

Boron isotopic compositions of some boron minerals  

Microsoft Academic Search

Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the 11 B \\/ 10 B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher 11 B \\/ 10 B ratios than those of nonmarine origin. It has been found that the sequence of

Takao Oi; Masao Nomura; Masaaki Musashi; Tomoko Ossaka; Makoto Okamoto; Hidetake Kakihana

1989-01-01

287

Boron injection at natural circulation conditions in PWRs  

SciTech Connect

Combustion Engineering has performed a boron injection test at San Onofre Unit 2 to demonstrate the ability to borate to the cold shutdown concentration at natural circulation conditions. The test was run in July 1983 and it has been analyzed with the BITRAN code developed at BNL. The test results will demonstrate injection and cooldown capability and provide data for validating boron transport and mixing models. Extrapolation of the test to more severe emergency conditions indicates oscillations in boron concentration which are predicting to decay within one hour after injection.

Perkins, K.R.

1983-01-01

288

The systematics of boron abundances in young volcanic rocks  

Microsoft Academic Search

Boron behaves as a highly incompatible trace element in oceanic settings, while in arcs it shows unique systematics indicative of fluid-rock interactions. Boron analyses conducted on well-characterized mid-ocean ridge basalt (MORB) suites show that B approximates K most closely in its solid\\/ melt distribution behavior, with inferred bulk distribution coefficients of 0.004-0.009 during melting in the mantle and up to

Jeffrey G. Ryan; Charles H. Langmuir

1993-01-01

289

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

NASA Astrophysics Data System (ADS)

Total number concentration of particles having diameter larger than 10 nm (NCN) and cloud condensation nuclei (NCCN) at 0.4, 0.6 and 0.8 supersaturations, and number size distribution of particles within 10-414 nm were measured in Seoul between 2004 and 2010. Overall average values of NCN and geometric mean diameter are 17811+-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 concentrations, 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 the fixed supersaturation of 0.6% were measured in and around the Korean Peninsula. During the 2011 campaign, a nephelometer was also deployed to measure aerosol scattering coefficients and its relation with aerosol concentrations. NCN and NCCN decrease rapidly with increasing altitude, except for the cases when particle formation and growths are thought to be occurring aloft. NCCN has a positive correlation with aerosol scattering coefficients measured by the nephelometer but their correspondence tends to vary with height. Occasions of very low NCCN/NCN (< 0.3) in the boundary layer are found to be associated with particle formation and growth events. With the support of ground observation, the particle formation and growth event that takes place over the Yellow Sea on one of the flight days is found to have the spatial scale larger than 100 x 450 km2. With the combination of 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.

Yum, S.; Kim, J.; Park, M.; Yum, J.; Yoon, S.

2013-12-01

290

Prompt gamma activation analysis of boron in reference materials using diffracted polychromatic neutron beam  

NASA Astrophysics Data System (ADS)

Boron concentrations were analyzed for standard reference materials by prompt gamma activation analysis (PGAA). The measurements were performed at the SNU-KAERI PGAA facility installed at Hanaro, the research reactor of Korea Atomic Energy Research Institute (KAERI). The facility uses a diffracted polychromatic beam with a neutron flux of 7.9 × 10 7 n/cm 2 s. Elemental sensitivity for boron was calibrated from the prompt gamma-ray spectra of boric acid samples containing 2-45 ?g boron. The sensitivity of 2131 cps/mg-B was obtained from the linearity of the boron peak count rate versus the boron mass. The detection limit for boron was estimated to be 67 ng from an empty sample bag spectrum for a counting time of 10,000 s. The measured boron concentrations for standard reference materials showed good consistency with the certified or information values.

Byun, S. H.; Sun, G. M.; Choi, H. D.

2004-01-01

291

Boron in the major UK rivers entering the North Sea  

Microsoft Academic Search

Boron in the major UK rivers entering the North Sea is predominantly in dissolved form and concentrations show large variations in time and space. The time-dependent feature relates to seasonal patterns linked to flow. Boron concentrations are well described by a power relationship of the type [B]=a?flowb, where a and b are constants. In this equation, the a term varies

Colin Neal; Kay K Fox; Martin Harrow; Margaret Neal

1998-01-01

292

The investigation of parameters affecting boron removal by electrocoagulation method  

Microsoft Academic Search

Boron removal from wastewaters by electrocoagulation using aluminum electrode material was investigated in this paper. Several working parameters, such as pH, current density, boron concentration and type and concentration of supporting electrolyte were studied in an attempt to achieve a higher removal capacity. The experiments were carried out by keeping the pH of solution constant and optimum pH of solution

A. Erdem Yilmaz; Recep Boncukcuo?lu; M. Muhtar Kocakerim; Bülent Keskinler

2005-01-01

293

Boron heavy doping for Si molecular beam epitaxy using a HBO2 source  

Microsoft Academic Search

Boron doping with a high carrier concentration has been realized in Si molecular beam epitaxy (MBE) using a HBO2 source with the usual Knudsen cell. Maximum carrier concentration has reached 6×1020 cm?3 at crucible temperatures of 900 °C. From a comparison between activation energy for vapor pressure and carrier concentration dependence on crucible temperature, it was concluded that boron evaporated

Toru Tatsumi; Hiroyuki Hirayama; Naoaki Aizaki

1987-01-01

294

Boron absorption imaging in rat lung colon adenocarcinoma metastases  

NASA Astrophysics Data System (ADS)

Given the encouraging results from our previous work on the clinical application of BNCT on non-resectable, chemotherapy resistant liver metastases, we explore the possibility to extend our technique to lung metastases. A fundamental requirement for BNCT is achieving higher 10B concentrations in the metastases compared to those in healthy tissue. For this reason we developed a rat model with lung metastases in order to study the temporal distribution of 10B concentration in tissues and tumoral cells. Rats with induced lung metastases from colon adenocarcinoma were sacrificed two hours after intraperitoneal Boronphenylalanine infusion. The lungs were harvested, frozen in liquid nitrogen and subsequently histological sections underwent neutron autoradiography in the nuclear reactor Triga Mark II, University of Pavia. Our findings demonstrate higher Boron uptake in tumoral nodules compared to healthy lung parenchyma 2 hours after Boronphenylalanine infusion.

Altieri, S.; Bortolussi, S.; Bruschi, P.; Fossati, F.; Vittor, K.; Nano, R.; Facoetti, A.; Chiari, P.; Bakeine, J.; Clerici, A.; Ferrari, C.; Salvucci, O.

2006-05-01

295

A new adsorbent for boron removal from aqueous solutions.  

PubMed

A new adsorbent based on natural clinoptilolite and amorphous zirconium dioxide (ZrO2) was prepared for the uptake of boron from fresh water. The sorption behaviour of this adsorbent for boron was investigated using a batch system and found to obey Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The ZrO2 loading level, pH, temperature, contact time, initial boron concentration and adsorbent dose, on the removal of boron were studied. It was found that the removal of boron increased while the adsorbent dose increased and the temperature decreased at an optimum pH (pH = 8) and a contact time of 30 min. At optimum conditions, the maximum boron percentage removal was 75%. According to the D-R model, the maximum capacity was estimated to be > 3 mg B/g of the adsorbent. The adsorption energy value (calculated as 9.13 kJ/mol) indicated that the adsorption of boron on clinoptilolite modified with ZrO2 was physical in nature. The parameters of the adsorption models and the pH investigations pointed to the possibility of a chemisorption process. The thermodynamic parameters (standard entropy deltaS degrees, enthalpy deltaH degrees , and free energy deltaG degrees changes) of boron adsorption were also calculated. The negative value of deltaS degrees indicated a decreased randomness at the solid-solution interface during the boron adsorption. Negative values of deltaH degrees showed the exothermic nature of the process. The negative values of deltaG degrees implied that the adsorption of boron on clinoptilolite modified with amorphous ZrO2 at 25 degrees C was spontaneous. It was considered that boron dissolved in water had been adsorbed both physically and chemically on clinoptilolite modified with 30% ZrO2. PMID:24191469

Kluczka, Joanna; Korolewicz, Teofil; Zo?otajkin, Maria; Simka, Wojciech; Raczek, Malwina

2013-01-01

296

Chemical disposition of boron in animals and humans.  

PubMed Central

Elemental boron was isolated in 1808. It typically occurs in nature as borates hydrated with varying amounts of water. Important compounds are boric acid and borax. Boron compounds are also used in the production of metals, enamels, and glasses. In trace amounts, boron is essential for the growth of many plants, and is found in animal and human tissues at low concentrations. Poisoning in humans has been reported as the result of accidental ingestion or use of large amounts in the treatment of burns. Boron as boric acid is fairly rapidly absorbed and excreted from the body via urine. The half-life of boric acid in humans is on the order of 1 day. Boron does not appear to accumulate in soft tissues of animals, but does accumulate in bone. Normal levels of boron in soft tissues, urine, and blood generally range from less than 0.05 ppm to no more than 10 ppm. In poisoning incidents, the amount of boric acid in brain and liver tissue has been reported to be as high as 2000 ppm. Recent studies at the National Institute of Environmental Health Sciences have indicated that boron may contribute to reduced fertility in male rodents fed 9000 ppm of boric acid in feed. Within a few days, boron levels in blood and most soft tissues quickly reached a plateau of about 15 ppm. Boron in bone did not appear to plateau, reaching 47 ppm after 7 days on the diet. Cessation of exposure to dietary boron resulted in a rapid drop in bone boron.(ABSTRACT TRUNCATED AT 250 WORDS)

Moseman, R F

1994-01-01

297

First gaseous boronization during pulsed discharge cleaning  

NASA Astrophysics Data System (ADS)

The first successful gaseous boronization during a pulsed discharge is reported. Sublimation of o-carborane (C2B10H12) combined with pulsed discharge plasmas with a repetition rate of 1 Hz is used to produce a hard boron-containing coating for reversed field pinch (RFP) plasmas in the Madison Symmetric Torus. X-ray photoelectron spectroscopy with Ar ion beam etching for silicon coupons installed at the plasma boundary shows about 60% boron concentration in the deposited layer. Both profilometer and scanning electron microscope analyses of the silicon coupons imply a strong toroidally non-uniform deposition depending on the location of the o-carborane injection. The layer thickness ranges from 50 to 300 nm. Ellipsometry calibrated with the profilometer results yields a refractive index of 2.2-2.3 for the films. The high refractive index implies that the coating is hard and has a well-ordered morphology. A reduction in wall recycling has consistently been observed after all boronization sessions. Comparison of the X-ray spectra in standard RFP plasmas before and after boronization indicates a slight decrease in the effective ionic charge.

Ko, J.; Den Hartog, D. J.; Goetz, J. A.; Weix, P. J.; Limbach, S. T.

2013-01-01

298

Patterned boron nanowires and field emission properties  

NASA Astrophysics Data System (ADS)

Patterns of assembled Fe3O4 nanoparticles on Si(111) wafer were formed by the self-assembly technique. Three factors, concentration of the Fe3O4 nanoparticles solution, dosage of the solution, and temperature of the Si wafer, were found to affect the quality of the Fe3O4 nanoparticle patterns. The prepared Si(111) wafer was used as the substrate to grow the patterned boron nanowires by thermoreduction method. Furthermore, a notable field emission property with moderate turn on field was obtained on the patterned boron nanowires. Our results indicate that the patterned boron nanowires have a great potential of applications in flat plane display and electron emission nanodevices.

Tian, Jifa; Hui, Chao; Bao, Lihong; Li, Chen; Tian, Yuan; Ding, Hao; Shen, Chengmin; Gao, Hong-Jun

2009-02-01

299

Direct current sputtering of boron from boron/coron mixtures  

DOEpatents

A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod.

Timberlake, John R. (Allentown, NJ); Manos, Dennis (Williamsburg, VA); Nartowitz, Ed (Edison, NJ)

1994-01-01

300

Computational Studies of Physical Properties of Boron Carbide  

SciTech Connect

The overall goal is to provide valuable insight in to the mechanisms and processes that could lead to better engineering the widely used boron carbide which could play an important role in current plight towards greener energy. Carbon distribution in boron carbide, which has been difficult to retrieve from experimental methods, is critical to our understanding of its structure-properties relation. For modeling disorders in boron carbide, we implemented a first principles method based on supercell approach within our G(P,T) package. The supercell approach was applied to boron carbide to determine its carbon distribution. Our results reveal that carbon prefers to occupy the end sites of the 3-atom chain in boron carbide and further carbon atoms will distribute mainly on the equatorial sites with a small percentage on the 3-atom chains and the apex sites. Supercell approach was also applied to study mechanical properties of boron carbide under uniaxial load. We found that uniaxial load can lead to amorphization. Other physical properties of boron carbide were calculated using the G(P,T) package.

Lizhi Ouyang

2011-09-30

301

Molecular Structure of boron  

NSDL National Science Digital Library

Boron was founded in 1808 by Sir Humphry Davy and Gay-Lussac and Thenard. It occurs as orthoboric acid in volcanic spring waters and as borates in Boron and colematic. Some sources can also be found in the Mohave Desert. It is used when making glass to keep the glass from breaking under temperature stress. Also if combined with sodium hydroxide and hydrogen peroxide it makes bleach.

2002-08-26

302

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

303

Behavior of Boron Isotopes During Chemical Weathering: a Global Approach  

NASA Astrophysics Data System (ADS)

Boron has two isotopes (10B and 11B) that fractionate largely during Earth surface processes. The major fractionating step takes place during low temperature water-rock interactions. Up to 20-30 \\permil difference in ? 11B units are shown to occur during the adsorption of boron onto surfaces or its precipitation into solids. Light boron has a much greater affinity for neoformed solids while the residual solution is enriched in heavy boron. For example, seawater has a boron isotopic composition of 40 \\permil, mainly due to the preferential removal of 10B during oceanic seafloor weathering, adsorption onto fluvial sediments and chemical weathering reactions occurring in soils. The high sensitivity of boron isotopes fractionation to water rock interactions make it a valuable tool to constrain chemical weathering processes. To have a global picture of the behavior of boron isotopes during chemical weathering of rocks at the surface of the continents, we analyzed the largest rivers for both the dissolved and suspended load. Dissolved boron isotopic compositions were published earlier ([Lemarchand et al., 2000]) and we here focus on the results for the suspended load and for the bottom sands. Boron clearly appears as a mobile element when its abundance in suspended sediments is normalized to upper continental material. Boron depletion in suspended solids is climate dependent, with higher depletion is warm climates. On average, more than 50 % of boron is transported to the ocean in a solid form. While the dissolved load of boron is clearly enriched in 11B (0 \\permil) with respect to the mean upper continental crust (-10 \\permil), isotopic composition of the suspended load of major rivers does not differ significantly from that of the continental crust. This result indicates that suspended material is not significantly fractionated with respect to the continental crust by chemical weathering processes or that the mass budget of boron partitioning between solids and water does not allow the residual solids to be significantly different from bedrock. This is supported by a Rayleigh distillation model. Our boron data, both in concentration and isotopic composition, give strong support to the idea that shale erosion is a major source of suspended sediments in large river system, making thus boron isotopes a good tracer of intra-continental recycling. Lemarchand et al., 2000, Nature, vol 408, pp 951-954.

Gaillardet, J.; Chetelat, B.

2004-12-01

304

Boron diffusion in nanocrystalline 3C-SiC  

NASA Astrophysics Data System (ADS)

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-2 is determined. GB diffusion in the bulk of the films is Fickian and thermally activated with DGB(T)=(3.1-5.6)×107exp(-5.03±0.16 eV/kBT) cm2s-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; Weiss, Charlotte; Canino, Mariaconcetta; Rachow, Thomas; Löper, Philipp; Summonte, Caterina; Mirabella, Salvo; Janz, Stefan; Wilshaw, Peter R.

2014-05-01

305

Concentration and spatial distribution of lead in soil used for ammunition destruction.  

PubMed

Studies on heavy metal contamination in soils used for ammunition disposal and destruction are still emerging. The present study aimed to evaluate the contamination level and spatial distribution of lead in disposal and destruction areas. This site was used for ammunition disposal and destruction activities for 20 years. The ammunition destruction site (1,296 ha), a sampling system that followed a sampling grid (5 m × 5 m) with 30 points was adopted and samples were collected at the following five depths with a total of 150 samples. During the collection procedure, each sampling grid point was georeferenced using a topographic global positioning system. Data were validated through semivariogram and kriging models using Geostat software. The results demonstrated that the average lead value was 163 mg kg(-1), which was close to the investigation limit and the contamination levels were higher downstream than upstream. The results showed that there was lead contamination at the destruction site and that the contamination existed mainly at the surface layer depth. However, high lead concentrations were also found at deeper soil depths in the destruction area due to frequent detonations. According to the planimetry data, the areas that require intervention significantly decreased with increasing depths in the following order: 582.7 m(2) in the 0-20 cm layer; 194.6 m(2) in the 20-40 cm layer; 101.6 m(2) in the 40-60 cm layer; and 45.3 m(2) in the 60-80 cm layer. PMID:22903201

do Nascimento Guedes, Jair; do Amaral Sobrinho, Nelson Moura Brasil; Ceddia, Marcos Bacis; Vilella, André Luis Oliveira; Tolón-Becerra, Alfredo; Lastra-Bravo, Xavier Bolívar

2012-10-01

306

Stimulatory effect of boron and manganese salts on keratinocyte migration.  

PubMed

Keratinocyte proliferation and migration are essential for the reconstruction of the cutaneous barrier after skin injury. Interestingly, thermal waters which are rich in trace elements (e.g. boron and manganese), are known to be able to improve wound healing. In order to understand the mechanism of action of this effect, our study investigated the in vitro modulation of keratinocyte migration and proliferation by boron and manganese salts, which are present in high concentrations in a thermal water (Saint Gervais). Our in vitro study demonstrated that incubating keratinocytes for 24 h with boron salts at concentrations between 0.5 and 10 microg/ml or manganese salts at concentrations between 0.1 and 1.5 microg/ml accelerated wound closure compared with control medium (+20%). As this acceleration was not related to an increase in keratinocyte proliferation we suggest that boron and manganese act on wound healing mainly by increasing the migration of keratinocytes. PMID:15202834

Chebassier, Nathalie; Ouijja, El Houssein; Viegas, Isabelle; Dreno, Brigitte

2004-01-01

307

Depth distribution of soil organic carbon fractions and AMS 14C concentrations at different landscape positions  

NASA Astrophysics Data System (ADS)

On sloped arable land soil redistribution has a great impact on spatial patterns of soil organic carbon (SOC) stocks and on the lateral and vertical carbon fluxes between soil and atmosphere. While most studies focus on total SOC, the investigation of the impact of soil redistribution on SOC fractions and thus on different SOC quality can improve the knowledge about the processes controlling an erosion induced C sink or source. Some studies indicate that the labile SOC pool might be preferentially transported by water erosion, however others indicate that black carbon being considered as an inert pool is preferentially redistributed. Preferential erosion and/or deposition of specific SOC fractions must lead to a spatial differentiation of the SOC pool composition in areas prone to erosion. In this study we analysed differences in the depth distribution of particle-size SOC fractions and AMS 14C concentrations in relation to these fractions at different slope positions within an arable field in western Germany. Based on modelled soil redistribution, two soil profiles representing depositional, erosional and reference (with ignorable erosion or deposition) sites were analysed. Soil cores were taken to a maximum depth of 1.6 m and were divided into 0.05 m increments except for the actual tillage depth (0-0.15 m). For every second depth increment starting with the topsoil layer total SOC, particle-size SOC fractions and AMS 14C concentrations were determined. The fractionation scheme of Amelung et al. (1998) was applied resulting in three particulate organic carbon fractions (POC 1: 250 - 2000 µm, POC 2: 53-250 µm, POC 3: 20 -53 µm) and the remaining fine sized fraction (< 20 µm). Combining POC 1 and 2, which are often assumed to represent the labile carbon pool shows a decline of SOC in these fractions from reference to erosional to depositional sites. This indicates (i) a preferential detachment of these fractions at erosional sites, while (ii) the more pronounced depletion at depositional sites may result from a multitude of processes, namely selective deposition, mineralisation during transport and/or enhanced mineralisation of the labile SOC pool. More than 80% of total SOC was stored in the fine-sized fraction commonly assumed to represent the passive SOC pool. For the topsoil layers the amount of this SOC pool was relatively similar at all slope positions, while it substantially differed in the subsoil layers. Throughout the depositional profiles the relative contribution of this pool remained relatively high proving a substantial stabilisation of SOC in the subsoil at depositional sites. The depth distribution of AMS 14C confirmed the observed differences in SOC pool composition at different slope positions. At the reference sites 14C decreased with depth indicating a relatively high amount of young plant residues in the topsoil and increasing amounts of more passive components in the subsoil. This decrease was more pronounced at erosion sites, whereas 14C content remained relatively high up to a certain depth at depositional sites hinting to burial and preservation of relatively recent SOC below the plough layer. Our results show that soil redistribution not only leads to spatial patterns of total SOC, but also alters the SOC pool composition and 14C concentrations along soil profiles at different slope positions proving the usefulness of these data to improve the understanding of the involved processes.

Dlugoß, V.; Fiener, P.; Schneider, K.

2012-04-01

308

Effects of boron supplementation on bone mineral density and dietary, blood, and urinary calcium, phosphorus, magnesium, and boron in female athletes.  

PubMed

The effects of boron supplementation on blood and urinary minerals were studied in female college students--17 athletes and 11 sedentary controls--over a one-year period. The athletes had lower percent body fat and higher aerobic capacities than sedentary controls. Athletic subjects consumed more boron in their normal diets than sedentary subjects; all other dietary measures were similar between the two groups. The athletes showed a slight increase in bone mineral density, whereas the sedentary group showed a slight decrease. Serum phosphorus concentrations were lower in boron-supplemented subjects than in subjects receiving placebos, and were lower at the end of the study period than during baseline analysis. Activity depressed changes in serum phosphorus in boron-supplemented subjects. Serum magnesium concentrations were greatest in the sedentary controls whose diets were supplemented with boron, and increased with time in all subjects. A group x supplement interaction was observed with serum magnesium; exercise in boron-supplemented subjects lowered serum magnesium. In all subjects, calcium excretion increased over time; in boron-supplemented subjects, boron excretion increased over time. In all subjects, boron supplementation affected serum phosphorus and magnesium, and the excretion of urinary boron. PMID:7889886

Meacham, S L; Taper, L J; Volpe, S L

1994-11-01

309

Effects of boron supplementation on bone mineral density and dietary, blood, and urinary calcium, phosphorus, magnesium, and boron in female athletes.  

PubMed Central

The effects of boron supplementation on blood and urinary minerals were studied in female college students--17 athletes and 11 sedentary controls--over a one-year period. The athletes had lower percent body fat and higher aerobic capacities than sedentary controls. Athletic subjects consumed more boron in their normal diets than sedentary subjects; all other dietary measures were similar between the two groups. The athletes showed a slight increase in bone mineral density, whereas the sedentary group showed a slight decrease. Serum phosphorus concentrations were lower in boron-supplemented subjects than in subjects receiving placebos, and were lower at the end of the study period than during baseline analysis. Activity depressed changes in serum phosphorus in boron-supplemented subjects. Serum magnesium concentrations were greatest in the sedentary controls whose diets were supplemented with boron, and increased with time in all subjects. A group x supplement interaction was observed with serum magnesium; exercise in boron-supplemented subjects lowered serum magnesium. In all subjects, calcium excretion increased over time; in boron-supplemented subjects, boron excretion increased over time. In all subjects, boron supplementation affected serum phosphorus and magnesium, and the excretion of urinary boron.

Meacham, S L; Taper, L J; Volpe, S L

1994-01-01

310

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

311

Physiological effects of a geothermal element: Boron excess in the epiphytic lichen Xanthoria parietina (L.) TH. FR  

Microsoft Academic Search

The results of a study aimed at investigating the effects of boron excess on a set of ecophysiological parameters in the lichen Xanthoria parietina, to set up a monitoring system to trace early biological effects of boron pollution in geothermal areas, are reported. To this purpose, lichen thalli have been incubated for 24h in solutions at boron concentrations of 0.1,

Tommaso Pisani; Silvana Munzi; Luca Paoli; Martin Ba?kor; Stefano Loppi

2009-01-01

312

Bor Madeninin Ah?ap Koruma Endüstrisinde De?erlendirilmesi Evaluation Boron Mine in Wood Protection Industry  

Microsoft Academic Search

Boron is the first element with five atomic number of tirth group in periodical system. It consist of two isotops, one having a mass number of 10, the other a mass number of 11. Boron is most common element in the soil, rock and water. Boron resource at high concentrations and economical is found plentiful in the arid, volcanic and

H. Sivrikaya

313

Boron-catalyzed multi-walled carbon nanotube growth with the reduced number of layers by laser ablation  

Microsoft Academic Search

Multi-walled carbon nanotubes with the reduced number of layers (2 or 3 layers) are dominantly produced by the laser ablation method using a carbon target mixed with boron. Chemical analysis with sub-nanometer resolution has revealed that the obtained nanotubes are composed of pure carbon layers with no boron concentration, while the boron carbide particle is found to be encapsulated at

K. Hirahara; K. Suenaga; S. Bandow; S. Iijima

2000-01-01

314

Investigation of the effects of soluble boron tracking on coupled CTF / NEM, LWR simulations  

SciTech Connect

The primary objective of this study is to evaluate the effects of introducing a boron tracking capability to the COBRA-TF / NEM code coupling. The Pennsylvania State University (PSU) versions of COBRA-TF - CTF, and Nodal Expansion Method (NEM) codes are utilized. Previous implementations of the CTF / NEM coupled code had no capability to model soluble boron feedback effects due to boron transport. This study builds upon the validation and qualification efforts of the boron tracking model implementation in CTF by modeling the boron feedback calculated by the CTF boron tracking model in NEM. The core model chosen for this study is the Purdue MOX/UO{sub 2} core model used in the 2007 OECD/NRC code benchmark study. Following the implementation of an explicit online coupling scheme and accompanying k-search routine, the newly coupled CTF / NEM code version with boron tracking is compared to prior results of the non-boron tracking CTF / NEM code version at steady-state hot full power and hot zero power conditions. It was found that the boron tracking model exhibited little influence on the hot zero power result as expected due to a smaller heat flux, which does not significantly change the moderator density and boron concentration as the moderator travels up the axial core length. Meanwhile the boron tracking model had a much greater impact on the hot full power results, predicting the critical inlet boron concentration to be 9.9 ppm below the non-boron tracking result due to greater and more rapid changes in boron concentration corresponding to the reduction in moderator density from being more rapidly heated. (authors)

Biery, M.; Avramova, M.; Ivanov, K. [Pennsylvania State University, Department of Mechanical and Nuclear Engineering, 331 Reber Building, University Park, PA 16802 (United States)] [Pennsylvania State University, Department of Mechanical and Nuclear Engineering, 331 Reber Building, University Park, PA 16802 (United States)

2013-07-01

315

Ionicities of Boron-Boron Bonds in B12 Icosahedra  

Microsoft Academic Search

First-principles calculations are used to investigate ionicities of boron-boron bonds in B12 icosahedra. It is observed that the geometrical symmetry breaking of B12 icosahedra results in the spatial asymmetry of charge density on each boron-boron bond, and further in the ionicity of B12 icosahedra. The results calculated by a new ionicity scale, a population ionicity scale, indicate that the maximum

Julong He; Erdong Wu; Huitian Wang; Riping Liu; Yongjun Tian

2005-01-01

316

Diffusion boronizing of molybdenum and niobium in boron carbide powder  

Microsoft Academic Search

1.A study was made of the boronizing of molybdenum and niobium in boron carbide powder with or without additions of halogen-containing activating agents.2.It was established that salts of hydrofluoboric acid are the most effective activating agents.3.The boronizing of refractory metals and alloys in commercial boron carbide powders ensures a comparatively high rate of coating formation and gives high quality of

L. A. Sosnovskii; A. P. Épik; A. P. Kraplya

1972-01-01

317

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

318

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

319

Targeting normal and neoplastic tissues in the rat jejunum and colon with boronated, cationic acrylamide copolymers.  

PubMed

A series of boronated cationic copolymers, composed of different ratios of acrylamide, N-acryloyl-3-aminophenylboronic acid and N-acryloyl-diaminoethane (the cationic moiety), were prepared with the intention of localizing boron neutron capture therapy (BNCT) in experimentally induced polyps on the luminal side of the gut of the rat. The goals of this study were to: (a) test the effect of cationization of the boronated copolymers on their uptake by polyps and normal adjacent epithelium; (b) compare the whole rat body distribution of aminophenylboronic acid (APB) and polymeric APB after local application; (c) measure the effect of micro-environmental parameters such as pH, the presence of mucin and cations on the interaction between the APB-copolymers and the epithelium of the rat intestines. Direct analysis of tissue boron levels showed that polymeric APB-uptake was higher in the colonic polyps than in the surrounding normal tissues. Free APB, however, was found in similar quantities in both. When tested in the normal jejunum and colon of the rat, polymeric APB uptake was directly proportional to the molar content of the cationic monomer in the copolymers. The presence of magnesium ions, free boron cationic monomer and mucin interfered with this uptake in a concentration-dependent manner. The uptake was pH-independent at pH 5, 7 and 10. APB accumulation in the colon polyps was inversely proportional to the cationic monomer content in the copolymers, suggesting an increased amount of mucus around the polyps, which probably impeded the electrostatic attachment of the polymer to the malignant tissue. The use polymeric APB for targeting BNCT in perioperative treatment of colorectal carcinoma is suggested, especially in the cases of microscopic residual disease after curative resection. PMID:16005094

Azab, Abdel-Kareem; Srebnik, Morris; Doviner, Victoria; Rubinstein, Abraham

2005-08-18

320

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

321

Determination of Boron and Carbon in Reactor Grade Boron Carbide.  

National Technical Information Service (NTIS)

The sealed tube method of dissolution at high temperature and pressure has been successfully applied in the analysis of reactor grade boron carbide for the determination of boron. A 50 mg sample of boron carbide is completely dissolved by heating with con...

D. Crossley A. J. Wood C. A. J. McInnes I. G. Jones

1978-01-01

322

Distribution of cetaceans and sea-surface chlorophyll concentrations in the California Current  

Microsoft Academic Search

A census of marine mammals was conducted off the coast of California (USA) in 1979–1980. The distribution of seasurface chlorophyll was determined at the same time by onboard fluorometry and by remote sensing using the Coastal Zone Color Scanner on the Nimbus-7 satellite. Comparisons of species and chlorophyll distributions indicate that marine mammals are not randomly distributed with respect to

R. C. Smith; P. Dustan; D. Au; K. S. Baker; E. A. Dunlap

1986-01-01

323

City breathability and its link to pollutant concentration distribution within urban-like geometries  

NASA Astrophysics Data System (ADS)

This paper is devoted to the study of pollutant concentration distribution within urban-like geometries. By applying efficiency concepts originally developed for indoor environments, the term ventilation is used as a measure of city "breathability". It can be applied to analyse pollutant removal within a city in operational contexts. This implies the evaluation of the bulk flow balance over the city and of the mean age of air. The influence of building packing density on flow and pollutant removal is, therefore, evaluated using those quantities. Idealized cities of regular cubical buildings were created with packing density ranging from 6.25% to 69% to represent configurations from urban sprawl to compact cities. The relative simplicity of these arrangements allowed us to apply the Computational Fluid Dynamics (CFD) flow and dispersion simulations using the standard k- ? turbulence model. Results show that city breathability within the urban canopy layer is strongly dependent from the building packing density. At the lower packing densities, the city responds to the wind as an agglomeration of obstacles, at larger densities (from about 44%) the city itself responds as a single obstacle. With the exception of the lowest packing density, airflow enters the array through lateral sides and leaves throughout the street top and flow out downstream. The air entering through lateral sides increases with increasing packing density. At the street top of the windward side of compact building configurations, a large upward flow is observed. This vertical transport reduces over short distance to turn into a downward flow further downstream of the building array. These findings suggest a practical way of identifying city breathability. Even though the application of these results to real scenarios require further analyses the paper illustrates a practical framework to be adopted in the assessment of the optimum neighbourhood building layout to minimize pollution levels.

Buccolieri, Riccardo; Sandberg, Mats; Di Sabatino, Silvana

2010-05-01

324

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

325

Microstructure Analysis of Boron Nanotubes.  

National Technical Information Service (NTIS)

Transmission electron microscopy and electron diffraction technique revealed boron nitride nanotube and nanoparticles in thin film boron nitride prepared by CVD method. Electron micrographs show single walled nanotubes containing these nonoparticles. The ...

E. Jelis S. Kerwien T. Chatterjee

2012-01-01

326

Analysis of spatial-temporal distributions of nitrate-N concentration in Shitoukoumen catchment in northeast China.  

PubMed

This article discusses the generation and migration process of nitrate-N pollution in shallow groundwater caused by agricultural nonpoint source pollution in the catchment area of Shitoukoumen Reservoir in northeast China. By monitoring the shallow groundwater nitrate-N in the low-water period, the normal season, and high-flow period in the study area for a year, it was found that the nitrate-N concentration in the shallow groundwater of this area had a seasonal variation in both spatial and time distribution. In the time distribution, the peak value appeared in July, the high-flow period, and the valley value appeared in April, the low-water period, and showed a significant correlation with the time distribution of fertilization rate and rainfall. In the spatial distribution of nitrate-N pollution, when the distribution in shallow groundwater was analyzed separately in the three different periods (low-water period, the normal season, and high-flow period) and the discipline transference and enrichment of nitrate-N pollution in shallow groundwater was determined, this indicated that the region in the southeast study area where runoff conditions were better was less contaminated, and the region where runoff conditions were poor, as well as the region along the river were seriously polluted. The nitrate-N concentration in shallow groundwater was distributed mainly along the path of groundwater flow and was excreted in the drainage region. This showed that the spatial distribution of nitrate-N concentration in the shallow groundwater of the entire region was mainly controlled by the groundwater flow system. At the same time, in the middle and lower reaches of the study area, the seasonal changes in the recharged-excreted relationship between groundwater and river caused seasonal differences in the spatial distribution of nitrate-N pollution in groundwater. The combined effects of the groundwater mobility and the surface river resulted in a poor correlation between the groundwater nitrate-N concentration and land-use types. Only in the plain area where there was little influence from groundwater runoff and the surface river did the groundwater nitrate-N concentration correlate with land-use types. The spatial and time distribution of nitrate-N concentration in the shallow groundwater of the study area was impacted by agricultural nonpoint source pollution, the groundwater flow system, and the surface river and formed a concentration response system which uses basins as a unit. PMID:19760082

Li, Jun; Lu, Wenxi; Zeng, Xiankui; Yuan, Jiehui; Yu, Furong

2010-10-01

327

Extending the Capabilities of Single Particle Mass Spectrometry: I. Measurements of Aerosol Number Concentration, Size Distribution, and Asphericity  

SciTech Connect

Single particle mass spectrometers have traditionally been deployed to measure the size and composition of individual particles at relatively slow sampling rates that are determined by the rate at which the ionization lasers can fire and/or mass spectra can be recorded. To take advantage of the fact that under most conditions SPLAT can detect and size particles at much higher rates we developed a dual data acquisition mode, in which particle number concentrations, size distributions, and asphericity parameters are measured at a particle concentration determined rate, all the while the instrument generates and records mass-spectra at an operator set rate. We show that with this approach particle number concentration and asphericity parameters are measured with 1 sec resolution and particle vacuum aerodynamic size distributions are measured with 10 sec to 60 sec resolution. SPLAT measured particle number concentrations are in perfect agreement with the PCASP. Particle asphericity parameters are based on measured particle beam divergence. We illustrate the effect that high particle concentrations can have on the measured size distributions and develop a method to remove these effects and correct the size distributions.

Vaden, Timothy D.; Imre, D.; Beranek, Josef; Zelenyuk, Alla

2011-01-04

328

[Study of arsenic concentration and distribution in shell sand of the shell ridge islands by hydride generation atomic fluorescence spectrometry].  

PubMed

The present paper determined the As concentration in shell sand of the shell ridge islands by hydride generation atomic fluorescence spectrometry, studied the distribution of As in shell sand of the shell ridge islands, analysed the correlations of As with other nutrient elements, and discussed the probably influencing factors affecting the As concentration and distribution in shell sand. The results showed that the range of the arsenic concentration in shell sand is between 0.78 and 8.76 mg x kg(-1), the average concentration is 3.11 mg x kg(-1), and this indicated that the As contamination of the shell ridge island is in clean level. The As concentration of the shell sand has a increasing trend followed by the increase with profile depth or the decrease with the particle size, and the difference in As concentrations in shell sand of different particle sizes reached the significant level (p < or = 0.05). The As concentration in shell sand has a very significant positive correlation with the concentrations of Cu, Zn and Mn as well as the TP and TK, whereas the correlations between As and TN or Fe are not significant. The pollutant of As in the shell sand mainly comes from the absorption and fixation by shell sand from the environment but not the accumulation of the shell organism during their growing up. PMID:24555397

Liu, Qing; Zhao, Xi-Mei; Xie, Wen-Jun; Sun, Jing-Kuan; Xia, Jiang-Bao; Lu, Zhao-Hua

2013-11-01

329

Unmitigated boron dilution events in a PWR. [During shutdown  

SciTech Connect

Dissolved boron is required for control of reactivity in a pressurized water reactor that is shut down. TRAC-PF1 calculations for a typical PWR for vessel-closed and vessel-open configurations show that a high-power excursion (approaching 20% of nominal operating power) is possible if dilution of the boron solution occurs. The calculations also show that sufficient heat capacity exists in the primary system to prevent a large temperature increase and that natural circulation flow of high concentration boron solution from the primary system into the core region will terminate the excursion.

Henninger, R.J.; Woodruff, S.B.

1982-03-01

330

Boron exposure assessment using drinking water and urine in the North of Chile.  

PubMed

Boron is an essential trace element for plants and humans however it is still an open question what levels of boron are actually safe for humans. This study, conducted between 2006 and 2010, measured exposure levels of boron in drinking water and urine of volunteers in Arica, an area in the North of Chile with high levels of naturally occurring boron. Samples were taken of tap and bottled water (173 and 22, respectively), as well as urine from 22 volunteers, and subsequently analyzed by inductively coupled plasma spectroscopy (ICP-OES). Boron varied in public tap water from 0.22 to 11.3mgL(-1), with a median value of 2.9mgL(-1), while concentrations of boron in bottled water varied from 0.01 to 12.2mgL(-1). Neither tap nor bottled water samples had concentrations of boron within WHO recommended limits. The concentration of boron in urine varied between 0.45 and 17.4mgL(-1), with a median of 4.28mgL(-1) and was found to be correlated with tap water sampled from the homes of the volunteers (r=0.64). Authors highly recommend that in northern Chile - where levels of boron are naturally high - that the tap and bottled water supplies be monitored in order to protect public health and that regulatory standards also be established for boron in drinking water in order to limit exposure. PMID:21978616

Cortes, S; Reynaga-Delgado, E; Sancha, A M; Ferreccio, C

2011-12-01

331

Boron incorporation into mullite  

NASA Astrophysics Data System (ADS)

Boron-doped mullites were synthesized using aluminium nitrate-nonahydrate, tetraethoxysilane and boric acid in a sol gel process with subsequent annealing at 950 and 1300 °C for five hours. Two different bulk compositions with constant Al2O3 contents (60 and 70 mol%, respectively) and varying SiO2 plus B2O3 contents were investigated. X-ray powder diffraction analyses yielded a linear decrease of the lattice parameters with increasing bulk B2O3 content, which was interpreted as to be due to boron incorporation. Related to the increasing boron content, corresponding infrared spectra revealed a slight and continuous shift for most of the absorption bands. These data show that mullite is able to incorporate large amounts of boron into its structure (up to about 20 mol% B2O3 depending on the bulk composition of the starting materials). Infrared analyses suggest that boron is incorporated into the mullite structure in form of planar three-fold coordinated BO3 groups.

Griesser, K. J.; Beran, A.; Voll, D.; Schneider, H.

2008-03-01

332

Estimates of microbial quality and concentration of copper in distributed drinking water are highly dependent on sampling strategy.  

PubMed

The numbers of bacteria generally increase in distributed water. Often household pipelines or water fittings (e.g., taps) represent the most critical location for microbial growth in water distribution systems. According to the European Union drinking water directive, there should not be abnormal changes in the colony counts in water. We used a pilot distribution system to study the effects of water stagnation on drinking water microbial quality, concentration of copper and formation of biofilms with two commonly used pipeline materials in households; copper and plastic (polyethylene). Water stagnation for more than 4h significantly increased both the copper concentration and the number of bacteria in water. Heterotrophic plate counts were six times higher in PE pipes and ten times higher in copper pipes after 16 h of stagnation than after only 40 min stagnation. The increase in the heterotrophic plate counts was linear with time in both copper and plastic pipelines. In the distribution system, bacteria originated mainly from biofilms, because in laboratory tests with water, there was only minor growth of bacteria after 16 h stagnation. Our study indicates that water stagnation in the distribution system clearly affects microbial numbers and the concentration of copper in water, and should be considered when planning the sampling strategy for drinking water quality control in distribution systems. PMID:17223387

Lehtola, Markku J; Miettinen, Ilkka T; Hirvonen, Arja; Vartiainen, Terttu; Martikainen, Pertti J

2007-12-01

333

A mathematical relationship for the explanation of ion exchange for boron adsorption  

Microsoft Academic Search

The present study was undertaken to investigate a method for boron removal from wastewaters from boric acid and borax plants. The ion-exchange method is effective for the removal of boron from solution. The experimental results under different initial concentrations are first converted into dimensionless variables by taking ratios of volumes and concentrations and subsequently plotted on double logarithmic graph papers.

Sami ?ahin

2002-01-01

334

The effect of boron on plasma testosterone and plasma lipids in rats  

Microsoft Academic Search

Recent studies have indicated that dietary boron can affect the concentration of steroid hormones in vivo. It has been suggested that the interaction between boron and steroid hormone metabolism is mediated by the hydroxylation process that steroids need to become biologically active. The increase in the concentration of some steroid hormones may impact favourably on cardiovascular and bone diseases. The

M. R. Naghii; S. Samman

1997-01-01

335

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

Microsoft Academic Search

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

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

2007-01-01

336

Micro-homogeneity studies of boron carbide powders  

Microsoft Academic Search

We have studied the micro-homogeneity of boron carbide powders by inductively coupled plasma optical emission spectrometry\\u000a (ICP-OES) and total reflection X-ray fluorescence spectrometry (TXRF) using slurry sampling. To get information on the particle\\u000a size distributions of the powders, the stabilized slurries of boron carbide powders were nebulized, the aerosols were transported\\u000a into a Batelle impactor and the droplets were collected

Alexander Kadenkin; Martin Amberger; Ursula E. A. Fittschen; José A. C. Broekaert

2011-01-01

337

Nitrogen concentrations in mosses indicate the spatial distribution of atmospheric nitrogen deposition in Europe  

Microsoft Academic Search

In 2005\\/6, nearly 3000 moss samples from (semi-)natural location across 16 European countries were collected for nitrogen analysis. The lowest total nitrogen concentrations in mosses (<0.8%) were observed in northern Finland and northern UK. The highest concentrations (?1.6%) were found in parts of Belgium, France, Germany, Slovakia, Slovenia and Bulgaria. The asymptotic relationship between the nitrogen concentrations in mosses and

H. Harmens; D. A. Norris; D. M. Cooper; G. Mills; E. Steinnes; E. Kubin; L. Thöni; J. R. Aboal; R. Alber; A. Carballeira; M. Co?kun; L. De Temmerman; M. Frolova; L. González-Miqueo; Z. Jeran; S. Leblond; S. Liiv; B. Ma?kovská; R. Pesch; J. Poikolainen; Å. Rühling; J. M. Santamaria; P. Simonèiè; W. Schröder; I. Suchara; L. Yurukova; H. G. Zechmeister

2011-01-01

338

Boron and silicon adsorption on an aluminum oxide  

Microsoft Academic Search

Boron and Si adsorption on the Al oxide, alon (delta-AlâOâ), were investigated under changing conditions of pH, total solution anion concentration, reaction time, and order of anion addition. Boron adsorption increased at low pH, exhibited a peak near pH 8, and decreased at high pH. The constant capacitance model was successfully used to describe B adsorption over the pH range

S. Goldberg; R. A. Glaudbig

2009-01-01

339

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

340

Use of boron waste as an additive in red bricks  

SciTech Connect

In boron mining and processing operations, large amounts of clay containing tailings have to be discarded. Being rich in boron, the tailings do not only cause economical loss but also pose serious environmental problems. Large areas have to be allocated for waste disposal. In order to alleviate this problem, the possibility of using clayey tailings from a borax concentrator in red brick manufacturing was investigated. Up to 30% by weight tailings addition was found to improve the brick quality.

Uslu, T.; Arol, A.I

2004-07-01

341

Modeling the U.S. national distribution of waterborne pathogen concentrations with application to Cryptosporidium parvum  

NASA Astrophysics Data System (ADS)

This paper provides a general statistical methodology for modeling environmental pathogen concentrations in natural waters. A hierarchical model of pathogen concentrations captures site and regional random effects as well as random laboratory recovery rates. Recovery rates were modeled by a generalized linear mixed model. Two classes of pathogen concentration models are differentiated according to their ultimate purpose: water quality prediction or health risk analysis. A fully Bayesian analysis using Markov chain Monte Carlo (MCMC) simulation is used for statistical inference. The applicability of this methodology is illustrated by the analysis of a national survey of Cryptosporidium parvum concentrations, in which 93% of the observations were zero counts.

Crainiceanu, Ciprian M.; Stedinger, Jery R.; Ruppert, David; Behr, Christopher T.

2003-09-01

342

Size distributions and exposure concentrations of nanoparticles associated with the emissions of oil mists from fastener manufacturing processes  

Microsoft Academic Search

The aims of the present study were set out to measure size distributions and estimate workers’ exposure concentrations of oil mist nanoparticles in three selected workplaces of the forming, threading, and heat treating areas in a fastener manufacturing plant by using a modified electrical aerosol detector (MEAD). The results were further compared with those simultaneously obtained from a nanoparticle surface

Ying-Fang Wang; Perng-Jy Tsai; Chun-Wan Chen; Da-Ren Chen; Yu-Tung Dai

343

Concentration and distribution of butyltin compounds in a heavy tanker route in the strait of Malacca and in Tokyo Bay  

Microsoft Academic Search

The distribution of butyltins was investigated in seawater at 20 stations (n=69) along the tanker route in the Strait of Malacca and in Tokyo Bay, areas of potential release of toxic organotin compounds to the aquatic environment from large vessels coated with antifouling paints containing tributyltin (TBT) compounds. Relatively high concentrations of butyltins were observed along the Strait of Malacca

Shinya Hashimoto; Masami Watanabe; Yasushi Noda; Toshihumi Hayashi; Yoshinobu Kurita; Yasusuke Takasu; Akira Otsuki

1998-01-01

344

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...

345

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

346

Minerals Yearbook 1989: Boron  

SciTech Connect

U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position as a source of sodium borate products and boric acid exported to foreign markets. Supplementary U.S. imports of Turkish calcium borate and calcium-sodium borate ores, borax, and boric acid, primarily for various glass uses, continued.

Lyday, P.A.

1990-08-01

347

The distribution and variability of simulated chlorophyll concentration over the tropical Indian Ocean from five CMIP5 models  

NASA Astrophysics Data System (ADS)

Performances of 5 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating the chlorophyll concentration over the tropical Indian Ocean are evaluated. Results show that these models are able to capture the dominant spatial distribution of observed chlorophyll concentration and reproduce the maximum chlorophyll concentration over the western part of the Arabian Sea, around the tip of the Indian subcontinent, and in the southeast tropical Indian Ocean. The seasonal evolution of chlorophyll concentration over these regions is also reproduced with significant amplitude diversity among models. All of 5 models is able to simulate the interannual variability of chlorophyll concentration. The maximum interannual variation occurs at the same regions where the maximum climatological chlorophyll concentration is located. Further analysis also reveals that the Indian Ocean Dipole events have great impact on chlorophyll concentration in the tropical Indian Ocean. In the general successful simulation of chlorophyll concentration, most of the CMIP5 models present higher than normal chlorophyll concentration in the eastern equatorial Indian Ocean.

Liu, Lin; Feng, Lin; Yu, Weidong; Wang, Huiwu; Liu, Yanliang; Sun, Shuangwen

2013-06-01

348

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.  

PubMed

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 (25-76ppm) for 3 protocols. Dosimetric calculations indicate that BNCT at RA-3 would be potentially therapeutic without exceeding radiotolerance in the lung. PMID:24360862

Trivillin, V A; Garabalino, M A; Colombo, L L; González, S J; Farías, R O; Monti Hughes, A; Pozzi, E C C; Bortolussi, S; Altieri, S; Itoiz, M E; Aromando, R F; Nigg, D W; Schwint, A E

2014-06-01

349

The concentration distribution around a growing gas bubble in a bio tissue under the effect of suction process.  

PubMed

The concentration distribution around a growing nitrogen gas bubble in the blood and other bio tissues of divers who ascend to surface too quickly is obtained by Mohammadein and Mohamed model (2010) for variant and constant ambient pressure through the decompression process. In this paper, the growing of gas bubbles and concentration distribution under the effect of suction process are studied as a modification of Mohammadein and Mohamed model (zero suction). The growth of gas bubble is affected by ascent rate, tissue diffusivity, initial concentration difference, surface tension and void fraction. Mohammadein and Mohamed model (2010) is obtained as a special case from the present model. Results showed that, the suction process activates the systemic blood circulation and delay the growth of gas bubbles in the bio tissues to avoid the incidence of decompression sickness (DCS). PMID:24813454

Mohammadein, S A

2014-07-01

350

Effects of Level and Distribution of Concentrate in Late Pregnancy on Ewe and Lamb Performance  

Microsoft Academic Search

During two different years, 1986 and 1989, 129 and 102 ewes, respectively, were used to compare the effects of level and feeding pattern of concentrate during the last eight weeks of pregnancy. The ewes were given hay to cover maintenance, with supplemental feeding for pregnancy based on different amounts of concentrate. The control groups were fed according to Swedish recommendations,

Inger Ledin

1995-01-01

351

On-Road measurement of particulate matter emissions from vehicles: particle concentration, size distribution and morphology  

Microsoft Academic Search

During summer 2010, we conducted a field experiment in Southern Michigan to measure on-road vehicle emissions. During the campaign, particulate matter (PM) concentrations were monitored with a Light Detection and Ranging (Lidar) and transmissometer system. The Lidar and transmissometer system measures PM mass concentration of vehicle exhaust using backscatter and extinction of an ultraviolet laser beam directed across the road.

N. Salvadori; S. China; J. Cook; H. D. Kuhns; H. Moosmuller; C. Mazzoleni

2010-01-01

352

Naturalized salmonid populations occur in the presence of elevated trace element concentrations and temperatures in the firehole river, yellowstone National Park, Wyoming, USA  

USGS Publications Warehouse

We investigated the effects of geothermally influenced waters on the distribution of rainbow trout, Oncorhynchus mykiss, and brown trout, Salmo trutta, in the Firehole River and its tributaries in Yellowstone National Park (WY, USA) from June 1997 to June 1998. Geothermal features in the Firehole River basin elevate mineral content and temperature in portions of the river and its tributaries. We found concentrations of boron and arsenic to be elevated in geothermally influenced areas compared with upstream sites. Boron concentrations occasionally exceeded 1,000 ??g/L, a proposed limit for the protection of aquatic organisms. Arsenic concentrations occasionally exceeded 190 ??g/L, the chronic ambient water quality criterion. Temperatures in geothermally influenced sites ranged up to 30??C and were consistently 5 to 10??C higher than upstream sites unaffected by geothermal inputs. Rainbow trout occurred at sites with elevated concentrations of boron, arsenic, and other trace elements and elevated water temperatures. Rainbow trout inhabited and spawned at sites with the most elevated trace element concentrations and temperatures; however, brown trout were absent from these sites. Water temperature may be the major factor determining brown trout distributions, but we cannot exclude the possibility that brown trout are more sensitive than rainbow trout to boron, arsenic, or other trace elements. Further investigations are needed to determine species-specific tolerances of boron, arsenic, and other trace elements among salmonids.

Goldstein, J. N.; Hubert, W. A.; Woodward, D. F.; Farag, A. M.; Meyer, J. S.

2001-01-01

353

Nitrogen concentrations in mosses indicate the spatial distribution of atmospheric nitrogen deposition in Europe.  

PubMed

In 2005/6, nearly 3000 moss samples from (semi-)natural location across 16 European countries were collected for nitrogen analysis. The lowest total nitrogen concentrations in mosses (<0.8%) were observed in northern Finland and northern UK. The highest concentrations (? 1.6%) were found in parts of Belgium, France, Germany, Slovakia, Slovenia and Bulgaria. The asymptotic relationship between the nitrogen concentrations in mosses and EMEP modelled nitrogen deposition (averaged per 50 km × 50 km grid) across Europe showed less scatter when there were at least five moss sampling sites per grid. Factors potentially contributing to the scatter are discussed. In Switzerland, a strong (r(2) = 0.91) linear relationship was found between the total nitrogen concentration in mosses and measured site-specific bulk nitrogen deposition rates. The total nitrogen concentrations in mosses complement deposition measurements, helping to identify areas in Europe at risk from high nitrogen deposition at a high spatial resolution. PMID:21620544

Harmens, H; Norris, D A; Cooper, D M; Mills, G; Steinnes, E; Kubin, E; Thöni, L; Aboal, J R; Alber, R; Carballeira, A; Co?kun, M; De Temmerman, L; Frolova, M; González-Miqueo, L; Jeran, Z; Leblond, S; Liiv, S; Ma?kovská, B; Pesch, R; Poikolainen, J; Rühling, A; Santamaria, J M; Simonèiè, P; Schröder, W; Suchara, I; Yurukova, L; Zechmeister, H G

2011-10-01

354

Synthesis of boron nitride powders  

NASA Astrophysics Data System (ADS)

In the materials science community there is much interest in the development of new, efficient approaches for preparing ceramic powders having properties or performance characteristics not found with powders produced by traditional metallurgical synthesis methods. In this regard, aerosol-based syntheses are finding general acceptance for the preparation of non-metal and metal oxide powders. In contrast, much less effort has been given to aerosol-type syntheses for non-oxide powders despite potentially useful benefits. This dissertation describes the application of two chemical systems in aerosol assisted vapor phase synthesis (AAVS) for the preparation of spherical morphology boron oxynitride, BNxOy, powders that are subsequently converted to spherical morphology boron nitride in a second nitridation step. Chapter 1 describes the AAVS synthesis of BNxOy powders using a reaction of an aqueous boric acid containing aerosol with ammonia at 1000°C. The effect of reactor tube material, total gas flow rate, ammonia concentration, boric acid concentration, and urea addition to the boric acid aerosol on the percent oxygen composition is described. The resulting BNxOy powders contain significant amounts of oxygen that require replacement in a second stage nitridation reaction at elevated temperature under ammonia. The influences of the reaction temperature profile, crucible geometry and transformation additive on final oxygen composition and powder crystallinity are described. Chapter 2 outlines the formation of BNxOy powders from an AAVS reaction between the boron precursor (MeO)3B and ammonia. The formation of the powders is studied as a function of total gas flow rate and ammonia concentration. In all cases the resulting powders contain lower levels of oxygen compared to powders produced from aqueous boric acid aerosols. The conversion of the BNxOy powders in the second stage nitridation reaction with ammonia is examined as a function of crucible geometry, temperature profile and ammonia flow rate. In support of this process, the molecular reaction between (MeO)3B and NH3 was reexamined. The adduct, (MeO)3B·NH3, was isolated and its molecular structure determined by single crystal X-ray diffraction techniques. The results of these studies provide guidance for more detailed studies that should result in industrial scale synthesis of spherical morphology BN which currently is not formed by standard metallurgical syntheses. This new material has potential applications in several areas including the formation of BN loaded organic polymer composites.

Dreissig, Dirk Horst

2002-09-01

355

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.

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

2013-01-01

356

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

357

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

358

Concentration and Distribution of Copper in Effluents from Three Freshwater Nuclear Power Stations.  

National Technical Information Service (NTIS)

The concentrations and physicochemical forms of copper were determined in samples from the water column and bedload sediments in the intake and discharge zones of the Vermont Yankee, Kewaunee, and Fort St. Vrain Nuclear Power Stations. These stations diff...

F. L. Harrison D. J. Bishop D. W. Rice R. Emerson B. J. Smith

1983-01-01

359

Boron-containing thiouracil derivatives for neutron-capture therapy of melanoma  

SciTech Connect

Boron-containing derivatives of 2-thiouracil and 2,4-dithiouracil and the corresponding 6-propyl compounds, containing a dihydroxyboryl group in the 5-position, have been prepared. These compounds accumulate in B16 melanoma in mice in concentrations up to 30 micrograms of boron per gram tissue. The uptake persists. The toxicity of both 2-thiouracil derivatives is low. These compounds are therefore good candidates for boron neutron-capture therapy of malignant melanoma.

Tjarks, W.; Gabel, D. (Univ. of Bremen (Germany, F.R.))

1991-01-01

360

Analysis of Airborne Boron and Phosphorus Contaminations on Wafer Surface by TOF-SIMS  

Microsoft Academic Search

Airborne boron and phosphorus contaminations on wafer surface has been analysed by TOF-SIMS. A known boron and phosphorus concentration BPSG sample was used as reference for the calibration of the TOF-SIMS. The detection limit reaches 1E8 at\\/cm2 for boron and 1E10 at\\/cm2 for phosphorus. This method is easy to applied and no sample preparation required. So TOF- SIMS is a

Mo Zhiqiang; Gui Dong; Hua Younan; Zhao Siping; Xing Zhenxiang

2006-01-01

361

Plasma boron and the effects of boron supplementation in males.  

PubMed Central

Recently, a proliferation of athletic supplements has been marketed touting boron as an ergogenic aid capable of increasing testosterone. The effect of boron supplementation was investigated in male bodybuilders. Ten male bodybuilders (aged 20 to 26) were given a 2.5-mg boron supplement, while nine male bodybuilders (aged 21 to 27) were given a placebo for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on day 1 and day 49 of the study. A microwave digestion procedure followed by inductively coupled argon plasma spectroscopy was used for boron determination. Twelve subjects had boron values at or above the detection limit with median value of 25 ng/ml (16 ng/ml lower quartile and 33 ng/ml upper quartile). Of the ten subjects receiving boron supplements, six had an increase in their plasma boron. Analysis of variance indicated no significant effect of boron supplementation on any of the other dependent variables. Both groups demonstrated significant increases in total testosterone (p < 0.01), lean body mass (p < 0.01), and one repetition maximum (RM) squat (p < 0.001) and one RM bench press (p < 0.01). The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser-trained bodybuilders, but boron supplementation affects these variables not at all.

Green, N R; Ferrando, A A

1994-01-01

362

Distribution of trace metal concentrations in paired cancerous and non-cancerous human stomach tissues  

PubMed Central

AIM: To assess whether trace metal concentrations (which influence metabolism as both essential and non-essential elements) are increased or decreased in cancerous tissues and to understand the precise role of these metals in carcinogenesis. METHODS: Concentrations of trace metals including Cd, Ni, Cu, Zn, Fe, Mg and Ca in both cancerous and non-cancerous stomach tissue samples were determined by atomic absorption spectrometry (AAS). Tissue samples were digested using microwave energy. Slotted tube atom trap was used to improve the sensitivity of copper and cadmium in flame AAS determinations. RESULTS: From the obtained data in this study, the concentrations of nickel, copper and iron in the cancerous human stomach were found to be significantly higher than those in the non-cancerous tissues, by using t-test for the paired samples. Furthermore, the average calcium concentrations in the cancerous stomach tissue samples were found to be significantly lower than those in the non-cancerous stomach tissue samples by using t-test. Exceedingly high Zn concentrations (207-826 mg/kg) were found in two paired stomach tissue samples from both cancerous and non-cancerous parts. CONCLUSION: In contrast to the literature data for Cu and Fe, the concentrations of copper, iron and nickel in cancerous tissue samples are higher than those in the non-cancerous samples. Furthermore, the Ca levels are lower in cancerous tissue samples than in non-cancerous tissue samples.

Yaman, Mehmet; Kaya, Gokce; Yekeler, Hayrettin

2007-01-01

363

Atmospheric concentrations, gaseous-particulate distribution, and carcinogenic potential of polycyclic aromatic hydrocarbons in Assiut, Egypt.  

PubMed

The concentrations of 15 priority PAHs were determined in the atmospheric gaseous and particulate phases from nine sites across Assiut City, Egypt. While naphthalene, acenaphthene, and fluorene were the most abundant in the gaseous phase with average concentrations of 377, 184, and 181 ng/m(3), benzo[b]fluoranthene, chrysene, and benzo[g,h,i]perylene showed the highest levels in the particulate phase with average concentrations of 76, 6, and 52 ng/m(3). The average total atmospheric concentration of target PAHs (1,590 ng/m(3)) indicates that Assiut is one of the highest PAH-contaminated areas in the world. Statistical analysis revealed a significant difference between the levels of PAHs in the atmosphere of urban and suburban sites (P?=?0.029 and 0.043 for gaseous and particulate phases, respectively). Investigation of diagnostic PAH concentration ratios revealed vehicular combustion and traffic exhaust emissions as the major sources of PAHs with a higher contribution of gasoline rather than diesel vehicles in the sampled areas. Benzo[a]pyrene has the highest contribution (average?=?32, 4 % for gaseous and particulate phases) to the total carcinogenic activity (TCA) of atmospheric PAHs. While particulate phase PAHs have higher contribution to the TCA, gaseous phase PAHs present at higher concentrations in the atmosphere are more capable of undergoing atmospheric reactions to form more toxic derivatives. PMID:24664637

Abdallah, Mohamed Abou-Elwafa; Atia, Noha Nahedj

2014-07-01

364

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

365

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

PubMed

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

Li, Chunfang; Li, Dongxiang; Wan, Gangqiang; Xu, Jie; Hou, Wanguo

2011-01-01

366

Effects on environment and agriculture of geothermal wastewater and boron pollution in great Menderes basin.  

PubMed

Boron toxicity is an important disorder that can be limit plant growth on soils of arid and semi arid environments through the world. High concentrations of Boron may occur naturally in the soil or in groundwater, or be added to the soil from mining, fertilizers, or irrigation water. Off all the potential resources, irrigation water is the most important contributor to high levels of soil boron, boron is often found in high concentrations in association with saline soil and saline well water. Although of considerable agronomic importance, our understanding of Boron toxicity is rather fragment and limited. In this study, Boron content of Great Menderes River and Basin was researched. Great Menderes Basin is one of the consequence basins having agricultural potential, aspect of water and soil resources in Turkey. Great Menderes River, water resource of the basin was to be polluted by geothermal wastewater and thermal springs including Boron element. Great Menderes Basin has abundant geothermal water resources which contain high amounts of Boron and these ground water are brought to surface and used for various purposes such as power generation, heating or thermal spring and than discharged to Great Menderes River. In order to prevent Boron pollution and hence unproductively in soils, it is necessary not to discharged water with Boron to irrigation water. According to results, it was obtained that Boron content of River was as high in particular Upper Basin where there was a ground thermal water reservoir. Boron has been accumulated more than plant requirement in this area irrigated by this water. Boron content of River was relatively low in rainy months and irrigation season while it was high in dry season. Boron concentration in the River was to decrease from upstream to downstream. If it is no taken measure presently, about 130,000 ha irrigation areas which was constructed irrigation scheme in the Great Menderes basin will expose the Boron pollution and salinity. Even though Boron concentration of river water is under 0.5 ppm limit value, Boron element will store in basin soils, decrease in crop yields, and occur problematic soils in basin. PMID:17171286

Koç, Cengiz

2007-02-01

367

Element concentrations in aqueous equilibrates of coal and lignite fly ashes  

Microsoft Academic Search

A survey was conducted of the concentration of arsenic, boron, molybdenum, phosphorus, and selenium in aqueous equilibrates of fly ashes derived from a number of soft coals and lignites. concentrations of boron were much higher than those of the other elements. The concentrations of water-soluble boron and molybdenum in the soft coal ashes and water-soluble selenium in the lignite ashes

Dorothy J. Churey; Walter H. Gutenmann; Alina Kabata-Pendias; Donald J. Lisk

1979-01-01

368

Geochemical distribution of trace element concentrations in the vicinity of Boroo gold mine, Selenge Province, Mongolia.  

PubMed

The environmental impacts of Boroo gold mine project in Mongolia was evaluated by chemical characterization of trace element concentrations in water, soils and tailing dam sediment samples. The results showed that concentrations of B, Cd, Ni and Se in the water samples were within the accepted levels of the Mongolia water quality standard (MNS4586: 1998). However, the concentrations of Al, As, Cu, Mn, Fe, Pb, U and Zn were higher than the maximum allowable concentration especially in the monitoring and heap leach wells. The average concentrations of As, Cd, Cu, Ni, Pb and Zn in the tailing dam sediment were 4419, 58.5, 56.0, 4.8, 20.6 and 25.7 mg/kg, respectively. Generally, arsenic and heavy metals in the soil samples were within the acceptable concentrations of the soil standard of Mongolia (MNS 5850: 2008). The chemical characterization of As solid phase in tailing dam sediment showed that the majority of As were found in the residual fraction comprising about 74% of total As. Assessing the potential risk to humans, simple bioavailability extraction test was used to estimate bioavailability of arsenic and heavy metals, and the concentrations extracted from tailing dam sediment were; 288.2 mg/kg As, 7.2 mg/kg Cd, 41.1 mg/kg Cu, 13.5 mg/kg Pb, 4.7 mg/kg Ni and 23.5 mg/kg Zn, respectively. From these results, the Boroo gold mine project has presently not significantly impacted the environment, but there is a high probability that it may act as a source of future contamination. PMID:21046434

Inam, Edu; Khantotong, Supawan; Kim, Kyoung-Woong; Tumendemberel, Bulgan; Erdenetsetseg, Sugar; Puntsag, Tamir

2011-01-01

369

Surface dopant concentration monitoring using noncontact surface charge profiling  

Microsoft Academic Search

This study is concerned with variations of the concentration of active boron dopant in the near surface region of silicon wafers. Boron can be deactivated by pairing with hydrogen or metals, particularly Cu and Fe, all of which may originate from the surface polishing process. The temperature dependence of boron activation is studied using the surface charge profiling method. Based

P. Roman; J. Staffa; S. Fakhouri; M. Brubaker; J. Ruzyllo; K. Torek; E. Kamieniecki

1998-01-01

370

Pesticide distributions in surface water: The distribution of pesticide concentrations at two study sites points to herbicides that may affect management of public water supplies  

USGS Publications Warehouse

Distributions of concentrations of 46 pesticides were documented from May 1992 through March 1994 for Maple Creek near Nickerson, Neb., and Platte River at Louisville, Neb. As their source of public water supplies, Lincoln and the western part of Omaha withdraw groundwater from the adjacent alluvium near the Platte River site, which is hydraulically connected to the Platte River. Organonitrogen herbicides dominated the pesticide distributions at each site. Variations in the distributions of pesticides at the two sites partly reflect differences in land use and land management practices. Diazinon, an insecticide used in urban areas, was commonly detected at the Platte River site but not at the Maple Creek site. Of the 46 pesticides analyzed at the Platte River site, the herbicides atrazine and alachlor were more likely to exceed their respective maximum contaminant levels of 3.0 and 2.0 pg/L; cyanazine was more likely to exceed the health advisory level of 1.0 ??g/L.

Stamer, J. K.; Wieczorek, M. E.

1996-01-01

371

[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

372

[Seasonal variation of concentrations and distribution characteristics of PCDD/Fs in atmosphere of an industrial area, Guangzhou].  

PubMed

Atmospheric concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were measured seasonally in an industrial area of Guangzhou City. And seasonal variation of concentrations and distribution characteristics of 2,3,7,8- PCDD/Fs was investigated. The PCDD/Fs concentrations and corresponding I-TEQ (toxic equivalent quantity) values were in the range of 2.33-75.4 pg x m(-3) (mean = 23.2 pg x m(-3)) and 0.229-10.7 pg x m(-3) (mean = 2.00 pg x m(-3)), respectively. The seasonal variation of PCDD/Fs concentrations was obvious, with the highest concentration was found in spring (37.8 pg x m(-3)) and the lowest in summer (13.5 pg x m(-3)). However, no obvious difference of concentrations was observed for autumn (22.3 pg x m(-3)) and winter (19.1 pg x m(-3)). The seasonal variation of I-TEQ values is as follows: spring (5.58 pg x m(-3)) > summer (1.06 pg x m(-3)) > autumn (0.839 pg x m(-3)) > winter (0.525 pg x m(-3)). The influences of monsoon and rainfall on the concentration of PCDD/Fs in atmosphere are discussed. PMID:24812934

Qing, Xian; Su, Yuan; Su, Qing; Zhang, Su-Kun; Ren, Ming-Zhong

2014-02-01

373

Boron and nitrogen-doped single-walled carbon nanotube  

NASA Astrophysics Data System (ADS)

Boron nitride semiconducting zigzag single-walled carbon nanotube (SWCNT), BcbNcnC, as a potential candidate for making nanoelectronic devices is investigated by first-principle full potential density functional theory (DFT). In contrast to the previous DFT calculations, where just one boron and nitrogen doping configuration is considered, here for the average over all possible configurations density of states is calculated in terms of boron and nitrogen concentrations. For example in many body techniques (MBTs) [R. Moradian, Phys. Rev. B 89 (2004) 205425] it is found that semiconducting average gap, Eg, could be controlled by doping nitrogen and boron. But in contrast to MBTs where gap edge in the average density of states is sharp, the gap edge is smeared and impurity states appear in the SWCNT semiconducting gap.

Moradian, Rostam; Azadi, Sam

2006-10-01

374

Concentrations and geographic distribution of selected organic pollutants in Scottish surface soils.  

PubMed

Concentrations of selected persistent organic pollutants (POPs) representing three chemical classes (polycyclic aromatic hydrocarbons (PAH), polybrominated diphenyl ethers (PBDE) and polychlorinated biphenyls (PCB) and the organic pollutant diethylhexyl phthalate (DEHP), were determined in surface soil samples (0-5 cm) collected at 20 km grid intersects throughout Scotland over a three-year period. Detectable amounts of all chemical classes and most individual congeners were present in all samples. There were no consistent effects of soil or vegetation type, soil carbon content, pH, altitude or distance from centres of population on concentrations which exhibited extreme variation, even in adjacent samples. It is concluded that soil POPs and DEHP concentrations and associated rates of animal and human exposure were highly variable, influenced by multiple, interacting factors, and not clearly related to local sources but possibly related to wet atmospheric deposition and the organic carbon content of the soil. PMID:23892068

Rhind, S M; Kyle, C E; Kerr, C; Osprey, M; Zhang, Z L; Duff, E I; Lilly, A; Nolan, A; Hudson, G; Towers, W; Bell, J; Coull, M; McKenzie, C

2013-11-01

375

Distribution of copper, lead, cadmium and zinc concentrations in soils around Kabwe town in Zambia  

Microsoft Academic Search

The extent of pollution of the environment as a result of mining activities in Kabwe, the provincial capital of Central province in Zambia has not yet been evaluated. Mining of lead and zinc were the core activities of Kabwe mine while cadmium and silver were produced as by-products. The smelting processes produced a significant amount of copper. The spatial distribution

Backsion D. Tembo; Kwenga Sichilongo; Joseph Cernak

2006-01-01

376

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

Microsoft Academic Search

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:

Li Tian; Yanhua Xu; Mingde Fu; Tao Peng; Yinghui Liu; Shiyin Long

2011-01-01

377

Geogenic distribution and baseline concentration of heavy metals in sediments of the Ganges River, India  

Microsoft Academic Search

The search for a better understanding of heavy metal distribution in large river sediments is a major concern in the exogenic cycling of elements through fluvial processes and in assessing the effects of anthropogenic influences. From the Asian continent, the Ganges River contributes a significant amount of sediments to the world's ocean. Freshly deposited sediments of the Ganges River were

Munendra Singh; German Müller; I. B Singh

2003-01-01

378

Monte Carlo simulation of the concentration distribution of sputtered cathode material in glow discharge plasma  

Microsoft Academic Search

The Monte Carlo computer code for the determination of the spatial distribution of atoms sputtered from the cathode material is presented. The code calculates the trajectories of sputtered particles in the plasma region assuming their neutral charge status during the whole path, which means that only scattering by plasma gas particles is taken into account in this model. The Moliere

J Here?; J Sielanko; Z Wroñski

2001-01-01

379

Measurements of ultrafine particle concentration and size distribution in the urban atmosphere  

Microsoft Academic Search

Particle size distributions were measured at three adjacent sites in Birmingham: a busy roadside (A38); 30 m away from the road and a nearby urban background site. Two scanning mobility particle sizers (SMPS), an electrical low pressure impactor (ELPI), a condensation particle counter and a thermophoretic precipitator were employed to measure and collect particles. Excellent agreement on the number weighted

Ji Ping Shi; A. A. Khan; Roy M. Harrison

1999-01-01

380

Droplet Size Distribution and Liquid Volume Concentration in a Water Spray: Predictions and Measurements.  

National Technical Information Service (NTIS)

A water spray, from a twin-fluid atomizer, was studied at different air temperature and at atmospheric pressure. The Sauter Mean Diameter, D32, and the droplet volume distribution were measured at four different distances from the injector. An optical met...

G. P. Pita

1984-01-01

381

Distribution of nickel in the roach (Rutilus rutilus L. ) after exposure to lethal and sublethal concentrations  

Microsoft Academic Search

In order to evaluate the eventual impact of nickel in fish kills occuring in the river Meuse in Belgium, a series of experiments were performed in which the uptake and distribution of nickel in Rutilus rutilus L., one of the dominant species in the river was studied after administration of nickel alone and in combination with other metals. In decreasing

F. Van Hoof; J. P. Nauwelaers

1984-01-01

382

Development of Tunable Diode Laser Absorption Tomography for Determination of Spatially Resolved Distributions of Water Vapor Temperature and Concentration  

NASA Astrophysics Data System (ADS)

Optical diagnostic techniques used in high speed, high enthalpy flows, such as in a supersonic ramjet (scramjet) combustor, allow direct measurement of temperature and species concentration. Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a common laser based measurement technique for measuring temperature and species concentration in harsh environments such as chemically reacting flows. TDLAS is a one-dimensional, path integrated measurement that provides average values of the measured quantities and can be affected by gradients in the measurement space. By combining TDLAS with tomographic image reconstruction a two-dimensional spatially resolved distribution can be obtained. This technique is called Tunable Diode Laser Absorption Tomography. TDLAT has been developed for the purpose of making temperature and species concentration measurements on the supersonic combustion facility at the Aerospace Research Laboratory. TDLAT has been developed for the purpose of making two-dimensional measurements of water vapor concentration, which when combined with Stereoscopic Particle Image Velocimetry can be used to calculate supersonic combustion efficiency of a scramjet combustor. This measurement system has been used in measurements of a flat flame burner from which two-dimensional distributions of temperature and water vapor concentration have been calculated. The calculated temperatures were then compared to measurements made on the same flat flame burner. Reconstructions of temperature and concentration show the structure of the flat flame burner, resolving regions of ambient room air, nitrogen co-flow, mixing layer and hot burner core. The TDLAT system was then installed on the supersonic combustion facility, where measurements were made for a known mole fraction of steam injected into the free stream. The TDLAT system was then used to measure water vapor concentration and temperature for clean-air combustion for an equivalence ratio of 0.17. The resulting values were then used to calculate supersonic combustion efficiency of the scramjet combustor.

Bryner, Elliott

383

Low energy Auger transitions of boron in several boron compounds  

Microsoft Academic Search

Boron KVV Auger spectra of B4C, BN, and B2O3 are compared with that of pure boron. The observed characteristic changes in the low energy features of the spectra are shown to be dependent on the compound partner of boron, which supplies extra decay channels. The main features of the Auger multiplet can be described in terms of an interatomic transition

G. Hanke; K. Mueller

1984-01-01

384

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

EPA Science Inventory

The application of quantitative real-time PCR (qPCR) methods for the identification of fecal microorganisms in surface waters has the potential to revolutionize water quality monitoring worldwide. Unlike traditional cultivation methods, qPCR estimates the concentration of gen...

385

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...

386

Angular reflectance of suspended gold, aluminum and silver nanospheres on a gold film: Effects of concentration and size distribution  

Microsoft Academic Search

In this article, we describe a parametric study of the effects of the size distribution (SD) and the concentration of nanospheres\\u000a in ethanol on the angular reflectance. Calculations are based on an effective medium approach in which the effective dielectric\\u000a constant of the mixture is obtained using the Maxwell–Garnett formula. The detectable size limits of gold, aluminum, and silver\\u000a nanospheres

Mustafa M. Aslan; Thomas Wriedt

2010-01-01

387

Concentration distribution of Yb 2+ and Yb 3+ ions in YbF 3:CaF 2 crystals  

Microsoft Academic Search

Calcium fluoride crystals doped with YbF3 were grown using the Bridgman technique. The optical absorption spectra reveal the characteristic UV-absorption bands of divalent Ytterbium. The absorption coefficient of divalent Yb is more than ten times higher than that of trivalent Ytterbium. This shows that the developed crystal growth process achieves a good Yb3+–Yb2+ conversion. The concentration distribution of the Yb2+

Irina Nicoara; Nicolae Pecingina-Garjoaba; Octavian Bunoiu

2008-01-01

388

Influence of Stream Flow on Hydrogen Sulfide Concentrations and Distributions of Two Trout Species in a Rocky Mountains Tailwater  

Microsoft Academic Search

Geothermal springs in or adjacent to streams can contribute hydrogen sulfide (H 2S) and affect distributions of fish. We assessed the effects of H2S, relative to discharge, on the locations and movements of cutthroat trout Oncorhynchus clarki and brown trout Salmo trutta in a regulated river in northwestern Wyo- ming. Concentrations of H2S as low as 0.13 mg\\/L pre- vented

Matthew R. Dare; Wayne A. Hubert; Joseph S. Meyer

2001-01-01

389

Concentrations, spatial distributions and congener profiles of polychlorinated biphenyls in soils from a coastal city--Tianjin, China.  

PubMed

A total of 82 surface soil samples collected from central urban sites, surrounding rural sites, coastal sites and background sites in Tianjin were analyzed for 84 PCB congeners. The mean values of total PCBs concentrations for surrounding rural sites, central urban sites, coastal sites, background sites and the whole Tianjin region were 4.45, 3.20, 12.65, 1.96 and 4.02 ng g(-1), respectively. No "urban fractionation effect" was found in Tianjin, which reflected the influence of local emission sources for PCBs such as industries and township enterprises in surrounding rural sites. In contrast, a "primary fractionation effect" was found in Tianjin region. The PCBs concentrations for whole Tianjin region showed a strong east-west gradient and the percentages of lighter molecular weight PCBs homologs (sum of di- to tetra-PCBs) to the total PCBs concentrations increased from east to west. The seven indicator PCBs concentrations were well correlated with the total PCBs concentrations with the correlation coefficients as 0.76 for Tianjin region and 0.74 for central urban sites, respectively. Predominant PCB homolog groups were penta- and tri-PCBs for Tianjin region. 10 dioxin-like PCBs concentrations were well correlated with total PCBs concentrations for all the sampling sites (R=0.79, P<0.0001). The TEQ concentrations for 10 dioxin-like PCBs were 5.3424 ng kg(-1) for Tianjin region and showed a strong east to west gradient. The spatial distribution of PCBs levels, homolog composition patterns and TEQ concentrations were all obviously influenced by local emission sources for PCBs in the east part of Tianjin region. PMID:21880349

Li, Zhiyong; Kong, Shaofei; Chen, Li; Bai, Zhipeng; Ji, Yaqin; Liu, Jinwei; Lu, Bing; Han, Bin; Wang, Qianwen

2011-10-01

390

Concentration and distribution of platinum group elements (Pt, Pd, Rh) in airborne particulate matter in Frankfurt am Main, Germany.  

PubMed

The concentrations and distribution of platinum group elements (Pt, Pd, Rh) in airborne particulate matter were studied in a period of one year from August 2001 to July 2002 in urban and in nonurban areas. Airborne dust samples were collected as a total amount (particles with an aerodynamic diameter <22 microm) and classified using an eight-stage Andersen impactor (<10 microm) at three locations with different traffic density roads in the Frankfurt am Main and nonurban areas. Sampling at the three locations was performed simultaneously for total airborne dust and fractionated airborne dust. Pd was determined by total reflection X-ray fluorescence after Hg coprecipitation. Pt and Rh were analyzed by adsorptive striping voltammetry after HPA digestion. The results show that the PGE concentrations in airborne samples depend on the traffic density. The highest PGE concentrations in air were found in the vicinity of major roads with heavy traffic, and the lowest ones were found in the nonurban area. The presence of PGE at the sampling station relatively free of traffic in a nonurban area hints to a transport of some of the emitted PGE from the city to this station by wind. At all three sampling locations, a heterogeneous distribution of the Pd, Pt, and Rh concentrations during the sampling year can be observed. The sum of PGE concentrations in total airborne dust is comparable with the sum of impactor samples. However, the concentration of Pt and Rh in total airborne dust (<22 microm) is on average higher than in impactor samples (<10 microm). On the contrary, Pd concentration is higher in impactor samples in most cases. The airborne PGE distribution is dominated by Pt, followed by Pd and Rh. The impactor samples are dominated by Pd, followed by Pt and Rh. This fact indicates that palladium occurs mainly in relatively fine airborne particles. The main fraction of PGE is found on average in particle sizes between 1.1 and 4.7 microm. Knowledge of the size distribution of particles containing PGE is important with respect to risk assessment of human inhalation. PMID:15074676

Zereini, Fathi; Alt, Friedrich; Messerschmidt, Jürge; von Bohlen, Alex; Liebl, Karlheinz; Püttmann, Wilhelm

2004-03-15

391

Dynamic behavior and concentration distribution of granular sludge in a super-high-rate spiral anaerobic bioreactor.  

PubMed

Dynamic behavior and concentration distribution of granular sludge is highly dependent on the ecological environment of microbial communities and substrate degradation efficiency along bed height. Both were modeled and verified through experiments in a super-high-rate spiral anaerobic bioreactor (SSAB). The sludge transport efficiency of upmoving biogas (k(t),(n)(-1)) displaying dynamic behavior of granular sludge in SSAB were predicted and found to be much lesser than of upflow anaerobic sludge blanket (UASB). The bed concentration distribution (C(m),(n)(-1)/C(m),(n)) which represented concentration distribution of granular sludge were also quantitatively predicted in two feeding strategies. Parametric sensitivity suggested that k(t),(n)(-1) was significantly influenced by spiral angle, outer radii of spiral rectangular channel, settling velocity of granular sludge and superficial liquid velocity (v(l)), while C(m),(n)(-1)/C(m),(n) was affected by v(l) and superficial biogas velocity. In addition, some measures were also suggested to optimize designs and operations of such bioreactors. PMID:22401715

Chen, Xiao-Guang; Zheng, Ping; Qaisar, Mahmood; Tang, Chong-Jian

2012-05-01

392

Boron based complex wear-resistant coatings  

Microsoft Academic Search

Applying boron, boron-copper, and boron-nickel diffusion coatings to die steels, as well as the microhardness, microbrittleness\\u000a and wear resistance of the steels with the coatings are considered.

Yu. A. Balandin

2006-01-01

393

Indoor/outdoor radon decay products associated aerosol particle-size distributions and their relation to total number concentrations.  

PubMed

The activity size distributions of indoor and outdoor radioactive aerosol associated with short-lived radon decay products were observed at Nagoya, Japan, for some periods from 2010 to 2012, following the indoor observation by Mostafa et al. [Mostafa, A. M. A., Tamaki, K., Moriizumi, J., Yamazawa, H. and Iida, T. The weather dependence of particle size distribution of indoor radioactive aerosol associated with radon decay products. Radiat. Prot. Dosim. 146: (1-3), 19-22 (2011)]. The tendency of smaller indoor activity median aerodynamic diameter (AMAD) after rainfalls showed in the previous study was not consistently obtained, while the consistent tendency of less indoor radioactive particles with diameters in the accumulation mode was observed again after rainfalls. The indoor aerosols showed activity size distributions similar to the outdoor ones. Non-radioactive aerosol particle concentrations measured with a laser particle counter suggested a somewhat liner relationship with AMAD. PMID:24723191

Moriizumi, Jun; Yamada, Shinya; Xu, Yang; Matsuki, Satoru; Hirao, Shigekazu; Yamazawa, Hiromi

2014-07-01

394

Boronizing protects metals against wear  

SciTech Connect

Boronizing is a thermochemical surface treatment that involves diffusion of boron into a base metal at a high temperature. The resulting metallic boride provides high hardness and resistance to acid corrosion, and lengthens service life by a factor of three to ten. Boronizing fills a gap between conventional surface treatments and the more exotic chemical and physical vapor deposition. In a number of applications, boronizing has replaced such processes as carburizing, nitriding, and nitrocarburizing. It has even replaced hard chrome plating in some cases, while achieving similar service life improvements. Boron can be uniformly applied to irregular surfaces, and can be applied to specific areas of a surface. It is also suitable for high-volume production applications, as first demonstrated in the European automotive industry. This article describes the boronizing process, provides material selection/preparation criteria, and lists industrial applications.

Stewart, K. [Lindberg Heat Treating Co., Rochester, NY (United States)

1997-03-01

395

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

396

Atmospheric particulate matter size distribution and concentration in West Virginia coal mining and non-mining areas.  

PubMed

People who live in Appalachian areas where coal mining is prominent have increased health problems compared with people in non-mining areas of Appalachia. Coal mines and related mining activities result in the production of atmospheric particulate matter (PM) that is associated with human health effects. There is a gap in research regarding particle size concentration and distribution to determine respiratory dose around coal mining and non-mining areas. Mass- and number-based size distributions were determined with an Aerodynamic Particle Size and Scanning Mobility Particle Sizer to calculate lung deposition around mining and non-mining areas of West Virginia. Particle number concentrations and deposited lung dose were significantly greater around mining areas compared with non-mining areas, demonstrating elevated risks to humans. The greater dose was correlated with elevated disease rates in the West Virginia mining areas. Number concentrations in the mining areas were comparable to a previously documented urban area where number concentration was associated with respiratory and cardiovascular disease. PMID:24549227

Kurth, Laura M; McCawley, Michael; Hendryx, Michael; Lusk, Stephanie

2014-07-01

397

Concentrations and distributions of Al, Fe, Ba and Zn in soils of Pre-Littoral Range, Sector Sentmenat (Catalonia, Spain).  

NASA Astrophysics Data System (ADS)

The Pre-Littoral Range is one of the six morphological units of the Barcelona province parallel to the coast, formed to the SW of the Lobregat fault by conglomerates, sandstones, and limestones. This Mesozoic-Paleogene range covers Paleozoic sediments with outcrops showing mainly Silurian schists and also granites. The main soils are Alfisols, Inceptisols and Entisols. Concentrations and distributions of five elements - Al, Fe, Ba and Zn - in 28 Sentmenat soil profiles (117 soil samples) were investigated. Background data ranges were estimated with the box plot [median ±2 median absolute deviation (MAD)] procedure as follows: Al: 6115 - 13731 mg kg-1, Fe: 7322 - 15106 mg kg-1, Ba: 17.6 - 90.8 mg kg-1 and Zn: 16.3 - 40.7 mg kg-1. Median concentrations of Ba and Zn are lower than the concentration in other European countries. Al concentrations were correlated with clay content, and Ba and Zn were negative correlated with CaCO3. Element distributions in soils reflected parent materials and pedogenic factor determining variation between and within soil profiles. Generally, metal contents decreased in the order of Alfisols> Entisols > Inceptisols and A > B >C horizons.

Tume, Pedro; Bech, Jaume; Longan, Lluis; Roca, Nuria; Reverter, Ferrán; Sanchez, Pedro

2013-04-01

398

Flux Distribution in Phantom for Biomedical Use of Beam-Type Thermal Neutrons  

Microsoft Academic Search

For boron neutron capture therapy, the thermal neutron beam is worth using (1)as therapeutic neutron irradiation without useless and unfavorable exposure of normal tissues around tumor and (2) for microanalysis system to measure ppm-order B concentrations in tissue and to search for the location of the metastasis of tumor. In the present study, the thermal neutron flux distribution in a

Kazuhiko AOKI; Tooru KOBAYASHI; Keiji KANDA; Itsuro KIMURA

1985-01-01

399

Boron Neutron Capture Therapy (BCNT) for the Treatment of Liver Metastases: Biodistribution Studies of Boron Compounds in an Experimental Model  

SciTech Connect

Abstract We previously demonstrated the therapeutic efficacy of different boron neutron capture therapy (BNCT) protocols in an experimental model of oral cancer. BNCT is based on the selective accumulation of 10B carriers in a tumor followed by neutron irradiation. Within the context of exploring the potential therapeutic efficacy of BNCT for the treatment of liver metastases, the aim of the present study was to perform boron biodistribution studies in an experimental model of liver metastases in rats. Different boron compounds and administration conditions were assayed to determine which administration protocols would potentially be therapeutically useful in in vivo BNCT studies at the RA-3 nuclear reactor. A total of 70 BDIX rats were inoculated in the liver with syngeneic colon cancer cells DHD/K12/TRb to induce the development of subcapsular tumor nodules. Fourteen days post-inoculation, the animals were used for biodistribution studies. We evaluated a total of 11 administration protocols for the boron compounds boronophenylalanine (BPA) and GB-10 (Na210B10H10), alone or combined at different dose levels and employing different administration routes. Tumor, normal tissue, and blood samples were processed for boron measurement by atomic emission spectroscopy. Six protocols proved potentially useful for BNCT studies in terms of absolute boron concentration in tumor and preferential uptake of boron by tumor tissue. Boron concentration values in tumor and normal tissues in the liver metastases model show it would be feasible to reach therapeutic BNCT doses in tumor without exceeding radiotolerance in normal tissue at the thermal neutron facility at RA-3.

Marcela A. Garabalino; Andrea Monti Hughes; Ana J. Molinari; Elisa M. Heber; Emiliano C. C. Pozzi; Maria E. Itoiz; Veronica A. Trivillin; Amanda E. Schwint; Jorge E. Cardoso; Lucas L. Colombo; Susana Nievas; David W. Nigg; Romina F. Aromando

2011-03-01

400

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.

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

401

Fluoride Concentrations and Distribution in Premolars of Children from Low and Optimal Fluoride Areas  

Microsoft Academic Search

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

K. Takeuchi; H. Nakagaki; Y. Toyama; N. Kimata; F. Ito; C. Robinson; J. A. Weatherell; L. Stösser; W. Künzel

1996-01-01

402

Concentration level and distribution of polycyclic aromatic hydrocarbons in soil and grass around Mt. Qomolangma, China  

Microsoft Academic Search

High mountains may serve as a condenser for persistent organic pollutants. In the present study, soil and grass samples from\\u000a Mt. Qomolangma region, China were collected from 4600 to 5620 m a.s.l and were analyzed for polycyclic aromatic hydrocarbons\\u000a (PAHs) to determine if they are concentrated at colder, more elevated sites and to evaluate their possible resources and fractionation.\\u000a The

XiaoPing Wang; TanDong Yao; ZhiYuan Cong; XinLiang Yan; ShiChang Kang; Yong Zhang

2007-01-01

403

Concentration and distribution of PCNs in ambient soil of a municipal solid waste incinerator.  

PubMed

The impact of a typical municipal solid waste incinerator (MSWI) on polychlorinated naphthalene (PCN) concentrations in surrounding soil was studied. We collected 6 stack gas samples from the MSWI and 21 soil samples from sampling sites at distances of between 300 and 1700m from the MSWI stack. Total dl-PCN (dioxin-like PCN) concentrations in the stack gas samples ranged from 6898 and 89,032pgm(-3), with a mean value of 36,241pgm(-3). The total dl-PCN concentrations in the soil samples ranged from 30.35 to 280.9pgg(-1), with a mean value of 87.03 and a median value of 70.32pgg(-1), while the TEQ values were between 7.7 and 130.2fg TEQ g(-1), with a mean value of 41.12fg TEQ g(-1) and a median value of 31.52fg TEQ g(-1). The PCN homologue patterns and the results of Principal Component Analysis suggested that the MSWI may be a source of PCNs in the soils. A contour map, created using an ordinary Kriging interpolation technique, showed that a limited area (?1000m radius) surrounding the MSWI was influenced by the emissions from the MSWI. Furthermore, an exponential function equation was proposed to quantify the relationship between TEQs of PCNs and the distance from the stack. PMID:24457132

Tian, Zhenyu; Li, Haifeng; Xie, Huiting; Tang, Chen; Han, Ying; Liu, Wenbin

2014-09-01

404

Distribution of Elevated Nitrate Concentrations in Ground Water in Washington State  

USGS Publications Warehouse

More than 60 percent of the population of Washington State uses ground water for their drinking and cooking needs. Nitrate concentrations in ground water are elevated in parts of the State as a result of various land-use practices, including fertilizer application, dairy operations and ranching, and septic-system use. Shallow wells generally are more vulnerable to nitrate contamination than deeper wells (Williamson and others, 1998; Ebbert and others, 2000). In order to protect public health, the Washington State Department of Health requires that public water systems regularly measure nitrate in their wells. Public water systems serving more than 25 people collect water samples at least annually; systems serving from 2 to 14 people collect water samples at least every 3 years. Private well owners serving one residence may be required to sample when the well is first drilled, but are unregulated after that. As a result, limited information is available to citizens and public health officials about potential exposure to elevated nitrate concentrations for people whose primary drinking-water sources are private wells. The U.S. Geological Survey and Washington State Department of Health collaborated to examine water-quality data from public water systems and develop models that calculate the probability of detecting elevated nitrate concentrations in ground water. Maps were then developed to estimate ground water vulnerability to nitrate in areas where limited data are available.

Frans, Lonna

2008-01-01

405

Sampling and analysis of chemical element concentration distribution in rock units and orebodies  

NASA Astrophysics Data System (ADS)

Existing sampling techniques applied within known orebodies, such as sampling along mining drifts, yield element concentration values for larger blocks of ore if they are extended into their surroundings. The resulting average concentration values have relatively small "extension variance". These techniques can be used for multifractal modeling as well as ore reserve estimation approaches. Geometric probability theory can aid in local spatial covariance modeling. It provides information about increase of variability of element concentration over short distances exceeding microscopic scale. In general, the local clustering of ore crystals results in small-scale variability known as the "nugget effect". Parameters to characterize spatial covariance estimated from ore samples subjected to chemical analysis for ore reserve estimation may not be valid at local scale because of the nugget effect. The novel method of local singularity mapping applied within orebodies provides new insights into the nature of the nugget effect. Within the Pulacayo orebody, Bolivia, local singularity for zinc is linearly related with logarithmically transformed concentration value. If there is a nugget effect, moving averages resulting from covariance models or estimated by other methods that have a smoothing effect, such as kriging, can be improved by incorporating local singularities indicating local element enrichment or depletion. Although there have been many successful applications of the multifractal binomial/p model, its application within the Pulacayo orebody results in inconsistencies, indicating some shortcomings of this relatively simple approach. Local singularity analysis and universal multifractal modeling are two promising new approaches to improve upon results obtained by commonly used geostatistical techniques and use of the binomial/p model. All methods in this paper are illustrated using a single example (118 Pulacayo zinc values), and several techniques are applied to other orebody datasets (Whalesback copper deposit, Witwatersrand goldfields and Black Cargo titanium deposit). Additionally, it is discussed that nugget effects exist in a binary series of alternating mostly gneiss and metabasite previously derived from KTB borehole velocity and lithology logs, and within a series of 2796 copper concentration values from this same drill-hole.

Agterberg, F. P.

2012-01-01

406

Boron nitride nanotubes  

Microsoft Academic Search

The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order of 1 to 3 nanometers and with lengths up to 200 nanometers were produced in a carbon-free plasma discharge between a BN-packed tungsten rod and a cooled copper electrode. Electron energy-loss spectroscopy on individual tubes yielded B:N ratios of approximately

N. G. Chopra; R. J. Luyken; K. Cherrey; V. H. Crespi; M. L. Cohen; S. G. Louie; A. Zettl

1995-01-01

407

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

408

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

409

Influence of titanium to boron ratio on the ability to grain refine aluminium-silicon alloys  

Microsoft Academic Search

Grain refinement is achieved in aluminium alloys by inoculating the molten metal with small amounts of titanium and boron. Grain refiners containing high concentrations of titanium and boron are available commercially for this purpose. However, these grain refiners come in different chemical compositions giving rise to a variety of Ti\\/B ratios. Although it is accepted that increasing the amount of

T. Sritharan; H. Li

1997-01-01

410

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 nan