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1

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

NASA Astrophysics Data System (ADS)

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

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

1999-11-01

2

Boron concentration measurement in biological tissues by charged particle spectrometry.  

PubMed

Measurement of boron concentration in biological tissues is a fundamental aspect of boron neutron capture therapy, because the outcome of the therapy depends on the distribution of boron at a cellular level, besides on its overall concentration. This work describes a measurement technique based on the spectroscopy of the charged particles emitted in the reaction (10)B(n,?)(7)Li induced by thermal neutrons, allowing for a quantitative determination of the boron concentration in the different components that may be simultaneously present in a tissue sample, such as healthy cells, tumor cells and necrotic cells. Thin sections of tissue containing (10)B are cut at low temperatures and irradiated under vacuum in a thermal neutron field. The charged particles arising from the sample during the irradiation are collected by a thin silicon detector, and their spectrum is used to determine boron concentration through relatively easy calculations. The advantages and disadvantages of this technique are here described, and validation of the method using tissue standards with known boron concentrations is presented. PMID:23835595

Bortolussi, S; Altieri, S

2013-11-01

3

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

SciTech Connect

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

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

1990-01-01

4

Boron concentration measurement system for the Czech BNCT project  

NASA Astrophysics Data System (ADS)

In the framework of the Czech Boron Neutron Capture Therapy (BNCT) project a Prompt Gamma Ray Analysis (PGRA) facility for the determination of the boron concentration in biological samples was built at light-water reactor at ?ež. The facility utilizes the beam of thermal neutrons from a neutron guide. The pure beam of thermal neutrons and background conditions enables the determination of 1 ppm with the reasonable statistical error 5% within 15 minutes.

Honzátko, J.; Tomandl, I.

2000-07-01

5

Boron distribution in the normal rat brain after intravenous injection of boronophenylalanine-fructose.  

PubMed

Boron neutron capture therapy (BNCT) is an experimental form of radiation therapy for malignant brain tumors and peripheral melanoma. The micro-distribution of the boron compound is critical to determine the radiation effects for both tumors and normal tissue. In the current dose calculation of BNCT, normal brain tissue is considered to have a homogeneous boron concentration. The purpose of this study was to examine the structure-specific boron concentration in normal rat neural tissue. At 10, 30 and 60 min after intravenous injection of 300 mg/kg boronophenylalanine-fructose to 10-week-old CD Fisher rats, neural tissue and blood were collected. Various neural structures were anatomically and histologically identified and specific boron concentrations were analyzed using high-resolution quantitative autoradiography. At 60 min after the injection, only the pituitary gland showed a higher boron concentration than that in blood, with the former being threefold higher. All other neural structures showed lower boron concentrations than that in blood. The present study thus demonstrated an extremely high boron concentration in the pituitary gland following intravenous injection of boronophenylalanine-fructose. In clinical trials of BNCT using an epithermal neutron beam, the radiation dose to the pituitary gland should be carefully evaluated. PMID:18026910

Shibata, Yasushi

2008-03-01

6

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

Microsoft Academic Search

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

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

2003-01-01

7

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

8

Characterization of the distribution of the sintering activator boron in powder metallurgical steels with SIMS.  

PubMed

Powder metallurgy is a well-established method for manufacturing ferrous precision parts. A very important step is sintering, which can be strongly enhanced by the formation of a liquid phase during the sintering process. Boron activates this process by forming such a liquid phase at about 1200 degrees C. In this work, the sintering of Fe-B was performed under the protective atmospheres of hydrogen, argon or nitrogen. Using different grain sizes of the added ferroboron leads to different formations of pores and to the formation of secondary pores. The effect of boron was investigated by means of Secondary Ion Mass Spectrometry (SIMS) supported by Scanning Electron Microscopy (SEM) and Light Microscopy (LM). To verify the influence of the process parameters on the mechanical properties, the microstructure (pore shape) was examined and impact energy measurements were performed. The concentrations of B in different samples were varied from 0.03-0.6 weight percent (wt%). Higher boron concentrations are detectable by EPMA, whereas the distributions of boron in the samples with interesting overall concentration in the low wt% range are only detectable by means of SIMS. This work shows that the distribution of boron strongly depends on its concentration and the sintering atmosphere used. At low concentration (up to 0.1 wt%) there are boride precipitations; at higher concentration there is a eutectic iron-boron grain boundary network. There is a decrease of the impact energy observed that correlates with the amount of eutectic phase. PMID:15004734

Krecar, Dragan; Vassileva, Vassilka; Danninger, Herbert; Hutter, Herbert

2004-06-01

9

Boron  

MedlinePLUS

... mineral that is found in food and the environment. People take boron supplements as medicine. Boron is ... Ineffective, and Insufficient Evidence to Rate. The effectiveness ratings for BORON are as follows:Preventing boron deficiency. ...

10

Mathematical Modeling and Experimental Validation of the Spatial Distribution of Boron in the Root of Arabidopsis thaliana Identify High Boron Accumulation in the Tip and Predict a Distinct Root Tip Uptake Function  

PubMed Central

Boron, an essential micronutrient, is transported in roots of Arabidopsis thaliana mainly by two different types of transporters, BORs and NIPs (nodulin26-like intrinsic proteins). Both are plasma membrane localized, but have distinct transport properties and patterns of cell type-specific accumulation with different polar localizations, which are likely to affect boron distribution. Here, we used mathematical modeling and an experimental determination to address boron distributions in the root. A computational model of the root is created at the cellular level, describing the boron transporters as observed experimentally. Boron is allowed to diffuse into roots, in cells and cell walls, and to be transported over plasma membranes, reflecting the properties of the different transporters. The model predicts that a region around the quiescent center has a higher concentration of soluble boron than other portions. To evaluate this prediction experimentally, we determined the boron distribution in roots using laser ablation-inductivity coupled plasma-mass spectrometry. The analysis indicated that the boron concentration is highest near the tip and is lower in the more proximal region of the meristem zone, similar to the pattern of soluble boron distribution predicted by the model. Our model also predicts that upward boron flux does not continuously increase from the root tip toward the mature region, indicating that boron taken up in the root tip is not efficiently transported to shoots. This suggests that root tip-absorbed boron is probably used for local root growth, and that instead it is the more mature root regions which have a greater role in transporting boron toward the shoots. PMID:25670713

Shimotohno, Akie; Sotta, Naoyuki; Sato, Takafumi; De Ruvo, Micol; Marée, Athanasius F.M.; Grieneisen, Verônica A.; Fujiwara, Toru

2015-01-01

11

Mathematical Modeling and Experimental Validation of the Spatial Distribution of Boron in the Root of Arabidopsis thaliana Identify High Boron Accumulation in the Tip and Predict a Distinct Root Tip Uptake Function.  

PubMed

Boron, an essential micronutrient, is transported in roots of Arabidopsis thaliana mainly by two different types of transporters, BORs and NIPs (nodulin26-like intrinsic proteins). Both are plasma membrane localized, but have distinct transport properties and patterns of cell type-specific accumulation with different polar localizations, which are likely to affect boron distribution. Here, we used mathematical modeling and an experimental determination to address boron distributions in the root. A computational model of the root is created at the cellular level, describing the boron transporters as observed experimentally. Boron is allowed to diffuse into roots, in cells and cell walls, and to be transported over plasma membranes, reflecting the properties of the different transporters. The model predicts that a region around the quiescent center has a higher concentration of soluble boron than other portions. To evaluate this prediction experimentally, we determined the boron distribution in roots using laser ablation-inductivity coupled plasma-mass spectrometry. The analysis indicated that the boron concentration is highest near the tip and is lower in the more proximal region of the meristem zone, similar to the pattern of soluble boron distribution predicted by the model. Our model also predicts that upward boron flux does not continuously increase from the root tip toward the mature region, indicating that boron taken up in the root tip is not efficiently transported to shoots. This suggests that root tip-absorbed boron is probably used for local root growth, and that instead it is the more mature root regions which have a greater role in transporting boron toward the shoots. PMID:25670713

Shimotohno, Akie; Sotta, Naoyuki; Sato, Takafumi; De Ruvo, Micol; Marée, Athanasius F M; Grieneisen, Verônica A; Fujiwara, Toru

2015-04-01

12

Determination of boron distribution in rat's brain, kidney and liver  

Microsoft Academic Search

To determine relative boron distribution in rat's brain, liver and kidney, a mixture of boric acid and borax, was used. After transcardial injection of the solution, the animals were sacrificed and the brain, kidney and liver were removed. The coronal sections of certain areas of the brain were prepared by freezing microtome. The slices were sandwiched within two pieces of

Ali Pazirandeh; Behnam Jameie; Maysam Zargar

2009-01-01

13

Boron  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

14

Determination of boron distribution in rat's brain, kidney and liver.  

PubMed

To determine relative boron distribution in rat's brain, liver and kidney, a mixture of boric acid and borax, was used. After transcardial injection of the solution, the animals were sacrificed and the brain, kidney and liver were removed. The coronal sections of certain areas of the brain were prepared by freezing microtome. The slices were sandwiched within two pieces of CR-39. The samples were bombarded in a thermal neutron field of the TRR pneumatic facility. The alpha tracks are registered on CR-39 after being etched in NaOH. The boron distribution was determined by counting these alpha tracks CR-39 plastics. The distribution showed non-uniformity in brain, liver and kidney. PMID:19375929

Pazirandeh, Ali; Jameie, Behnam; Zargar, Maysam

2009-07-01

15

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

E-print Network

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

Florida, University of

16

CAN BROCCOLI TOLERATE HIGHER CONCENTRATIONS OF BORON UNDER SALINE CONDITIONS?  

Technology Transfer Automated Retrieval System (TEKTRAN)

Reuse of saline drainage water is a management option that is necessary for reducing the volume of drainage water produced on the west side of California's San Joaquin Valley (SJV). A potential limitation in implementing a drainage water reuse system is determining the extent by which boron, a natur...

17

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

SciTech Connect

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

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

1986-02-01

18

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

19

Metabolic responses of postmenopausal women to supplemental dietary boron and aluminum during usual and low magnesium intake: boron, calcium, and magnesium absorption and retention and blood mineral concentrations.  

PubMed

Findings from animal studies indicate that dietary boron affects several aspects of mineral metabolism, especially when animals are subjected to nutritional stressors. Eleven postmenopausal volunteers living on a metabolic ward for 167 d (one 23-d equilibration period and six 24-d treatment periods) were fed a conventional basal diet that supplied a daily average intake of 0.36 mg B, 109 mg Mg, and < 0.10 mg A1/8400 kJ. They were given supplements of 0 (BB) or 3 mg B (SB, last two periods only), 0 (BMg) or 200 mg Mg (SMg) (with magnesium supplements held constant during the last two periods), or 0 (BAl) or 1000 mg A1 (SAl)/d. The SB treatment, compared with the BB treatment, provided a 9.0-fold increase in dietary boron but yielded only a 1.5-fold increase in plasma boron concentrations. Regardless of boron dietary treatment, fecal plus urinary excretion of boron accounted for nearly 100% of dietary boron intake with no evidence of boron accumulation over time. Lack of boron accumulation and relatively small changes in blood boron values during a substantial increase in dietary boron support the concept of boron homeostasis. In subjects fed BMg, SB decreased the percentage of dietary calcium lost in the urine but increased that percentage in volunteers fed SMg, a relation that may be important in understanding metabolic mineral disorders that perturb calcium balance. Reduced calcium absorption during SAl suggests that aluminum supplementation should be limited or at least monitored in postmenopausal women prone to excessive calcium loss. Decreased total urinary oxalate during SB in BMg subjects indicates a possible role for boron in the control of urolithiasis during low-magnesium nutriture. PMID:9062533

Hunt, C D; Herbel, J L; Nielsen, F H

1997-03-01

20

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

21

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

22

Subcellular boron and fluorine distributions with SIMS ion microscopy in BNCT and cancer research  

SciTech Connect

The development of a secondary ion mass spectrometry (SIMS) based technique of Ion Microscopy in boron neutron capture therapy (BNCT) was the main goal of this project, so that one can study the subcellular location of boron-10 atoms and their partitioning between the normal and cancerous tissue. This information is fundamental for the screening of boronated drugs appropriate for neutron capture therapy of cancer. Our studies at Cornell concentrated mainly on studies of glioblastoma multiforme (GBM). The early years of the grant were dedicated to the development of cryogenic methods and correlative microscopic approaches so that a reliable subcellular analysis of boron-10 atoms can be made with SIMS. In later years SIMS was applied to animal models and human tissues of GBM for studying the efficacy of potential boronated agents in BNCT. Under this grant the SIMS program at Cornell attained a new level of excellence and collaborative SIMS studies were published with leading BNCT researchers in the U.S.

Subhash Chandra

2008-05-30

23

Influence of carbon concentration on chemical behavior of energetic deuterium implanted into carbon-contained boron film  

NASA Astrophysics Data System (ADS)

Influence of carbon concentration on chemical behavior of energetic deuterium implanted into carbon-contained boron film was investigated by XPS and TDS. Total deuterium retention and the retention of deuterium trapped by boron were decreased as the carbon concentration was increased, although that by carbon was increased. 60% of the total deuterium retention was trapped by carbon for the sample at the carbon concentration of around 30%, suggesting that deuterium had more affinity with carbon than boron. Above the carbon concentration of 20%, the chemical states of carbon were clearly changed, which led to the deuterium trapping by carbon, indicating the chemical structure change would make a large influence on D trapping. It can be said that deuterium trapped by carbon should be taken into consideration for the evaluation of tritium inventory in the carbon-contained boron film with the carbon concentration above 20%.

Suzuki, Sachiko; Yang, Yu; Yoshikawa, Akira; Kikuchi, Yohei; Sagara, Akio; Oya, Yasuhisa; Okuno, Kenji

2009-06-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

25

Oxyanion Concentrations in Eastern Sierra Nevada Rivers – 3. Boron, Molybdenum, Vanadium, and Tungsten  

Microsoft Academic Search

Water samples were collected from 10 locations along the Truckee River system, 14 locations along the Walker River system, and 12 locations along the Carson River, and analyzed for B, Mo, V, W, Na, Cl, and pH. Boron concentrations ranged from approximately 2 µmol\\/kg in the upper reaches of the Truckee River to almost 1,200 µmol\\/kg in Pyramid Lake. Molybdenum,

Kevin H. Johannesson; W. Berry Lyons; Elizabeth Y. Graham; Kathleen A. Welch

2000-01-01

26

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

27

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

PubMed

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

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

2010-02-01

28

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

SciTech Connect

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

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

2014-03-07

29

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

30

Electroextraction of boron from boron carbide scrap  

SciTech Connect

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

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

2013-10-15

31

Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor  

NASA Technical Reports Server (NTRS)

A process for producing polycrystalline silicon carbide includes heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

2000-01-01

32

Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor  

NASA Technical Reports Server (NTRS)

A process for producing polycrystalline silicon carbide by heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

2001-01-01

33

Comparison of the level of boron concentrations in black teas with fruit teas available on the Polish market.  

PubMed

The determination of boron by inductively coupled plasma-atomic emission spectrometry has been carried in water-soluble and acid soluble (total content) fractions of 36 samples of traditional black tea and fruit brew. The estimation of the impact of the type of tea on the concentration of boron in water-soluble and acid extracts and potential human health risk from the daily intake of boron was carried out in this study. The levels of boron differed significantly in black and fruit tea types. The mean total content of boron ranged from 8.31 to 18.40 mg/kg in black teas, from 12.85 to 15.13 mg/kg in black tea with fruit flavor, and from 12.09 to 22.77 mg/kg in fruit brews. The degree of extraction of boron in black tea ranged from 8% to 27% and for fruit tea from 17% to 69%. In addition, the values below 25% were of black teas with fruit flavors. The daily intake of B from tea infusions (three cups/day) is still within the average daily intake except for some of the fruit brews which exceed acceptable regulations of the daily intake of total boron by humans. Hence, it may not produce any health risks for human consumption, if other sources of metal contaminated food are not taken at the same time. PMID:25379551

Zio?a-Frankowska, Anetta; Frankowski, Marcin; Novotny, Karel; Kanicky, Viktor

2014-01-01

34

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

35

The distribution of boron and boric acid complexes in the sea  

E-print Network

LIBRARY A a m GOLLEGE 0F TEXAS THE DISTRIBUTION OF BORON AND BORIC ACID COMPLEXES IN THE SEA A Thesis By John Noakes o%e Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in Partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE January 1959 Major: Chemical Oceanography THE DISTRIBUTION OF BORON AND BORIC ACID COMPLEXES IN THE SEA A Thesis By John Noakes Approved as to style and content by: C irman of the C ittee Head...

Noakes, John Edward

1959-01-01

36

Relationships between boron concentrations and trout in the Firehole River, Wyoming: historical information and preliminary results of a field study.  

PubMed

The Firehole River (FHR) in Yellowstone National Park (YNP) is a world-renowned recreational fishery that predominantly includes rainbow trout (RBT, Oncorhynchus mykiss) and brown trout (BNT, Salmo trutta). The trout populations apparently are closed to immigration and have been self-sustaining since 1955. Inputs from hot springs and geysers increase the temperature and mineral content of the water, including elevating the boron (B) concentrations to a maximum of approximately 1 mg B/L. Both RBT and BNT reside in warm-water reaches, except when the water is extremely warm (> or = approximately 25 degrees C) during midsummer. They spawn in late fall and early winter, with documented spawning of BNT in the cold-water reach upstream from the Upper Geyser Basin and of RBT in the Lower Geyser Basin reach, where water temperatures presumably are the warmest; however, successful recruitment of RBT in waters containing approximately 1 mg B/L has not been demonstrated conclusively. Thus, we began investigating the relationships among temperature, B concentrations, other water-quality parameters, and the distribution and reproduction of trout in the FHR in spring 1997. However, atypical high water flows and concomitant lower than historical temperatures and B concentrations during summer 1997 preclude conclusions about avoidance of high B concentrations. PMID:10050918

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

1998-01-01

37

Disposition and tissue distribution of boron after infusion of borocaptate sodium in patients with malignant brain tumors  

Microsoft Academic Search

Purpose: In the frame of the Czech boron neutron capture therapy (BNCT) project, a clinical Phase I study of borocaptate sodium [Na2B12H11SH (BSH)] as the boron-10 delivery agent was performed to obtain data on disposition and tissue distribution of boron after an infusion of this compound, as well as to establish an optimal protocol for BNCT of malignant cerebral tumors.Methods

Vladim??r Horn; D Pharm; Josef Slánský; Ivo Janku; Old?ich Štrouf; Karel Šourek; František Tovaryš

1998-01-01

38

CONCENTRATION OF POSTERIOR DISTRIBUTIONS WITH MISSPECIFIED MODELS  

E-print Network

CONCENTRATION OF POSTERIOR DISTRIBUTIONS WITH MISSPECIFIED MODELS Christophe ABRAHAMa and Benoît investigate the asymptotic properties of posterior distributions when the model is misspecified, i the asymptotic of the posterior distribution when the model is correctly specified i.e. q is equal to h for some

Boyer, Edmond

39

Distribution of hydrocarbon concentrations from urban runoff.  

PubMed

Hydrocarbon runoff data from Madrid have been analysed in order to determine the effect of time, area characteristics and water flow on the runoff concentration frequency distribution. In this study, aliphatic and aromatic hydrocarbon concentrations obtained from runoff sampling from different areas of Madrid at different times of the year were used. The cumulative frequency distributions of a number of the hydrocarbons are characterized as modal lognormal distributions. The close correlation found between aliphatic and aromatic hydrocarbon concentrations can be expressed by a regression line. PMID:2360028

Bomboi, M T; Hernández, A; Mariño, F; Hontoria, E

1990-04-01

40

Decomposition and element concentrations of silver birch leaf litter as affected by boron status of litter and soil  

Microsoft Academic Search

Inadequate boron (B) nutrition can affect the structural integrity and chemical composition of plant tissues. The changes\\u000a in mass and element concentrations were studied using silver birch (Betula pendula Roth) leaf litter from seedlings grown with or without added B (Blitter+ or Blitter?). The litter was produced in a growth room, and it was incubated in either B fertilised or

Tarja Lehto; Aino Smolander; Pedro J. Aphalo

2010-01-01

41

Oligomer distribution in concentrated lactic acid solutions  

Microsoft Academic Search

Lactic acid (2-hydroxypropanoic acid) is a significant platform chemical for the biorenewable economy. Concentrated aqueous solutions of lactic acid (>30wt.%) contain a distribution of oligomers that arise via intermolecular esterification. As a result, the titratable acidity changes non-linearly with acid concentration. In this work, the oligomer distribution of lactic acid is characterized using GC, GC\\/MS, and HPLC to extend existing

Dung T. Vu; Aspi K. Kolah; Navinchandra S. Asthana; Lars Peereboom; Carl T. Lira; Dennis J. Miller

2005-01-01

42

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

43

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

44

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

45

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

USGS Publications Warehouse

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 of arsenic and fluoride above USEPA drinking-water standards of 10 ?g/L and 4 mg/L, respectively, and of boron above the USEPA health advisory level of 600 ?g/L were measured in ground water in an area along the northwestern edge of the Newark Basin. In 2003, the USEPA requested technical assistance from the U.S. Geological Survey (USGS) to help identify sources of arsenic, boron, and fluoride in the ground water in the Congo Road area, which included possible anthropogenic releases and naturally occurring mineralization in the local bedrock aquifer, and to identify other areas in the Newark Basin of southeastern Pennsylvania with similarly elevated concentrations of these constituents. The USGS reviewed available data and collected additional ground-water samples in the Congo Road area and four similar hydrogeologic settings. The Newark Basin is the largest of the 13 major exposed Mesozoic rift basins that stretch from Nova Scotia to South Carolina. Rocks in the Newark Basin include Triassic through Jurassic-age sedimentary sequences of sandstones and shales that were intruded by diabase. Mineral deposits of hydrothermal origin are associated with alteration zones bordering intrusions of diabase and also occur as strata-bound replacement deposits of copper and zinc in sedimentary rocks. The USGS review of data available in 2003 showed that water from about 10 percent of wells throughout the Newark Basin of southeastern Pennsylvania had concentrations of arsenic greater than the USEPA maximum contaminant level (MCL) of 10 ?g/L; the highest reported arsenic concentration was at about 70 ?g/L. Few data on boron were available, and the highest reported boron concentration in well-water samples was 60 ?g/L in contrast to concentrations over 5,000 ?g/L in the Congo Road area. Although concentrations of fluoride up to 4 mg/L were reported for a few well-water samples collected throughout the Newark Basin, about 90 percent of the samples had concentrations of 0.5 mg/L or less. The USGS sampled 58 wells primarily in 5 areas in the Newark Basin, southeastern Pennsylvania, from February 2004 through April 2005 to identify other possible areas of elevated arsenic, boron, and fluoride and to characterize the geochemical environment associated with elevated concentrations of these constituents. Sampled wells included 12 monitor wells at an industrial facility near Congo Road, 45 private-supply wells in Berks, Montgomery, and Bucks Counties, and 1 private-supply well near Dillsburg, York County, an area where elevated fluoride in ground water had been reported in the adjacent Gettysburg Basin. Wells were sampled in transects from the diabase through the adjacent hornfels and into the unaltered shales of the Brunswick Group. Field measurements were made of pH, temperature, dissolved oxygen concentration, and specific conductance. Samples were analyzed in the laboratory for major ions, nutrients, total organic carbon, dissolved and total concentrations of selected trace elements, and boron isotopic composition. Generally, the ground water from the 46 private-supply wells had relatively neutral to alkaline pH (ranging from 6.1 to 9.1) and moderate concentrations of dissolved oxygen. Most water samples were of the calcium-bicarbonate type. Concentrations of arsenic up to 60 ?g/L, boron up to 3,950 ?g/L, and fluoride up to 0.70 mg/L were measured. Drinking-water standards or health advisories (for constituents that do not have standards established) were exceeded most frequently (about 20 percent of samples) for arsenic and boron and less frequently (6 percent or less of samples) for total iron, manganese, sulfate, nitrate, lead, molybdenum, and strontium. In water from 12 monitor

Senior, Lisa A.; Sloto, Ronald A.

2006-01-01

46

Kinetics of Boron Sorption and Desorption in Boron Thermal Regeneration System  

Microsoft Academic Search

Boron is used in the primary coolant of pressurized water reactors in nuclear power generation for shim control. If boron concentration is decreased, fewer neutrons are adsorbed and more fission occurs. When boron concentration increases, less fission occurs. The boron concentration can be controlled by the use of ion-exchange resins operating in the Boron Thermal Regeneration System (BTRS). A better

JIDONG LOU; GARY L. FOUTCH; JUNG WON NA

2000-01-01

47

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

48

Improvement of dose distribution by central beam shielding in boron neutron capture therapy  

NASA Astrophysics Data System (ADS)

Since boron neutron capture therapy (BNCT) with epithermal neutron beams started at the Kyoto University Reactor (KUR) in June 2002, nearly 200 BNCT treatments have been carried out. The epithermal neutron irradiation significantly improves the dose distribution, compared with the previous irradiation mainly using thermal neutrons. However, the treatable depth limit still remains. One effective technique to improve the limit is the central shield method. Simulations were performed for the incident neutron energies and the annular components of the neutron source. It was clear that thermal neutron flux distribution could be improved by decreasing the lower energy neutron component and the inner annular component of the incident beam. It was found that a central shield of 4-6 cm diameter and 10 mm thickness is effective for the 12 cm diameter irradiation field. In BNCT at KUR, the depth dose distribution can be much improved by the central shield method, resulting in a relative increase of the dose at 8 cm depth by about 30%. In addition to the depth dose distribution, the depth dose profile is also improved. As the dose rate in the central area is reduced by the additional shielding, the necessary irradiation time, however, increases by about 30% compared to normal treatment.

Sakurai, Yoshinori; Ono, Koji

2007-12-01

49

Improvement of dose distribution by central beam shielding in boron neutron capture therapy.  

PubMed

Since boron neutron capture therapy (BNCT) with epithermal neutron beams started at the Kyoto University Reactor (KUR) in June 2002, nearly 200 BNCT treatments have been carried out. The epithermal neutron irradiation significantly improves the dose distribution, compared with the previous irradiation mainly using thermal neutrons. However, the treatable depth limit still remains. One effective technique to improve the limit is the central shield method. Simulations were performed for the incident neutron energies and the annular components of the neutron source. It was clear that thermal neutron flux distribution could be improved by decreasing the lower energy neutron component and the inner annular component of the incident beam. It was found that a central shield of 4-6 cm diameter and 10 mm thickness is effective for the 12 cm diameter irradiation field. In BNCT at KUR, the depth dose distribution can be much improved by the central shield method, resulting in a relative increase of the dose at 8 cm depth by about 30%. In addition to the depth dose distribution, the depth dose profile is also improved. As the dose rate in the central area is reduced by the additional shielding, the necessary irradiation time, however, increases by about 30% compared to normal treatment. PMID:18065847

Sakurai, Yoshinori; Ono, Koji

2007-12-21

50

The excess electron in a boron nitride nanotube: pyramidal NBO charge distribution and remarkable first hyperpolarizability.  

PubMed

The unusual properties of species with excess electrons have attracted a lot of interest in recent years due to their wide applications in many promising fields. In this work, we find that the excess electron could be effectively bound by the B atoms of boron nitride nanotube (BNNT), which is inverted pyramidally distributed from B-rich edge to N-rich edge. Further, Li@B-BNNT and Li@N-BNNT are designed by doping the Li atom to the two edges of BNNT, respectively. Because of the interaction between the Li atom and BNNT, the 2s valence electron of Li becomes a loosely bound excess electron. Interestingly, the distribution of the excess electron in Li@N-BNNT is more diffuse and pyramidal from B-rich edge to N-rich edge, which is fascinating compared with Li@B-BNNT. Correspondingly, the transition energy of Li@N-BNNT is 0.99 eV, which is obviously smaller than 2.65 eV of Li@B-BNNT. As a result, the first hyperpolarizability (3.40×10(4) a.u.) of Li@N-BNNT is dramatically larger (25 times) than 1.35×10(3) a.u. of Li@B-BNNT. Significantly, we find that the pyramidal distribution of the excess electron is the key factor to determine the first hyperpolarizability, which reveals useful information for scientists to develop new electro-optic applications of BNNTs. PMID:22829460

Zhong, Rong-Lin; Xu, Hong-Liang; Sun, Shi-Ling; Qiu, Yong-Qing; Su, Zhong-Min

2012-09-01

51

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: Actual strain applied on pristine graphene and 2BNG; Raman spectra of CVD graphene and 2BNG transferred onto PDMS substrates; schematic of the atomic model; I2D/IG Raman ratio as a function of the PDMS strain for pristine graphene in the reversible deformation region; Raman information of the I2D/IG ratio for pristine graphene in the irreversible deformation region; Raman G band for graphene before and under applied strain; I2D/IG Raman ratio as a function of the PDMS strain for the 2BNG film in the reversible deformation region; Raman information of the I2D/IG ratio for 2BNG in the irreversible deformation region; Raman G band for 2BNG before and under applied strain; the schematic diagram of the deposition process for a strain sensor device; schematic diagram of the 2D stress applied to graphene and BNG films; actual strain on graphene and BNG measured by Raman versus PDMS strain; schematic diagrams of the strain distribution. See DOI: 10.1039/c4nr00495g

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

2014-07-01

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

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

54

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

PubMed

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

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

2014-08-30

55

Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.  

PubMed

The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 ?M) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. PMID:25660808

Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

2015-04-01

56

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

57

Role of boron oxide in growth of boron nitride grains  

SciTech Connect

Grain growth in sintered hexagonal boron nitride ceramics hot-pressed from microcrystalline and crystalline powders was studied. Boron oxide released during sintering, especially from the microcrystalline powder, had a crucial effect on the size and orientation of boron nitride grains and on the mechanical properties of the ceramics. The extraction of boron oxide from the boron nitride grains with elemental boron and subsequent conversion to a refractory suboxide resulted in a substantial rise in the refractoriness, preventing the undesirable growth of boron nitride grains, and reducing their response to the uniaxial effect of the external pressure. The migration mechanism of boron oxide ill hot-pressed boron nitride was also confirmed by measurements of the oxygen distribution ill the ceramics.

Hubacek, Milan; Ueki, Masanori [Nippon Steel Corp., Kawasaki (Japan)

1996-12-31

58

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

E-print Network

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

Harigaya, Kikuo

2011-01-01

59

The effect of nitrogen and boron soil applications on raspberry leaf N, B and Mn concentrations and on selected soil analyses  

Microsoft Academic Search

Four years after yearly applications of N (0, 67, 134 and 268 kg\\/ha in a N rate trial) soil pH and soil extractable K, Ca and Mg were reduced. Boron application (1 kg\\/ha in a N x B interaction trial) increased hot water extractable soil B and soil extractable Mg. Old and new cane leaf N concentration was increased by

C. G. Kowalenko

1981-01-01

60

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

61

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

62

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

63

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. PMID:7889881

Woods, W G

1994-01-01

64

Exact analytic flux distributions for two-dimensional solar concentrators.  

PubMed

A new approach for representing and evaluating the flux density distribution on the absorbers of two-dimensional imaging solar concentrators is presented. The formalism accommodates any realistic solar radiance and concentrator optical error distribution. The solutions obviate the need for raytracing, and are physically transparent. Examples illustrating the method's versatility are presented for parabolic trough mirrors with both planar and tubular absorbers, Fresnel reflectors with tubular absorbers, and V-trough mirrors with planar absorbers. PMID:23842256

Fraidenraich, Naum; Henrique de Oliveira Pedrosa Filho, Manoel; Vilela, Olga C; Gordon, Jeffrey M

2013-07-01

65

Dust size distribution and concentrations with cottonseed oil mills  

E-print Network

DUST SIZE DISTRIBUTION AND CONCENTRATIONS WITHIN COTTONSEED OIL MILLS A Thesis by LEE ROY WIEDERHOLD, JR. / I Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE August 1976 Major Subject: Aqricultural Engineering DUST SIZE DISTRIBUTION AND CONCENTRATIONS WITHIN COTTONSEED OIL MILLS A Thesis by LEE ROY WIEDERHOLD, JR. Approved as to style and content by: Chairman of Committee ~Hd fdp t Member ber...

Wiederhold, Lee Roy

1976-01-01

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

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

68

Distribution analysis of airborne nicotine concentrations in hospitality facilities.  

PubMed

A number of publications report statistical summaries for environmental tobacco smoke (ETS) concentrations. Despite compelling evidence for the data not being normally distributed, these publications typically report the arithmetic mean and standard deviation of the data, thereby losing important information related to the distribution of values contained in the original data. We were interested in the frequency distributions of reported nicotine concentrations in hospitality environments and subjected available data to distribution analyses. The distribution of experimental indoor airborne nicotine concentration data taken from hospitality facilities worldwide was fit to lognormal, Weibull, exponential, Pearson (Type V), logistic, and loglogistic distribution models. Comparison of goodness of fit (GOF) parameters and indications from the literature verified the selection of a lognormal distribution as the overall best model. When individual data were not reported in the literature, statistical summaries of results were used to model sets of lognormally distributed data that are intended to mimic the original data distribution. Grouping the data into various categories led to 31 frequency distributions that were further interpreted. The median values in nonsmoking environments are about half of the median values in smoking sections. When different continents are compared, Asian, European, and North American median values in restaurants are about a factor of three below levels encountered in other hospitality facilities. On a comparison of nicotine concentrations in North American smoking sections and nonsmoking sections, median values are about one-third of the European levels. The results obtained may be used to address issues related to exposure to ETS in the hospitality sector. PMID:11868665

Schorp, Matthias K; Leyden, Donald E

2002-02-01

69

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

70

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

71

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

PubMed

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

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

2010-01-01

72

Prediction of Concentration Distribution in Pipeline Flow of Highly Concentrated Slurry  

Microsoft Academic Search

Kaushal and Tomita (2002c) model, which has already been found satisfactory for broadly graded multisized particulate zinc tailings slurry with moderate concentration up to 26%, flow velocity up to 3.5 m\\/s in 105 mm diameter pipe, mean diameter and geometric standard deviation of particles as 140 ?m and 4.0, respectively, is tested for concentration distribution data collected by Kaushal et al. (2005)

D. R. Kaushal; Yuji Tomita

2012-01-01

73

A better steam engine: Designing a distributed concentrating  

E-print Network

by project basis not required · Increased overall solar utilization with CHP · Thermal storage is cheaper, h d thydrogen, etc. · Hydro · Wind · Solar - PV, Thermal ­ 5.4 GW of PV, 20 GW of solar thermalA better steam engine: Designing a distributed concentrating solar combined heat and power (DCS

Kammen, Daniel M.

74

Numerical prediction of concentration and current distributions in PEMFC  

Microsoft Academic Search

In this study, we present a rigorous 3-D mathematical model, to treat prediction and analysis of proton exchange membrane fuel cells (PEMFC) species concentration and current density distributions in different flow field patterns and operating conditions. The model is based on the solution of the conservation equations of mass, momentum, species and electric current in a fully integrated finite-volume solver

Fang-Bor Weng; Ay Su; Guo-Bin Jung; Yen-Chiao Chiu; Shih-Hung Chan

2005-01-01

75

In-phantom two-dimensional thermal neutron distribution for intraoperative boron neutron capture therapy of brain tumours.  

PubMed

The aim of this study was to determine the in-phantom thermal neutron distribution derived from neutron beams for intraoperative boron neutron capture therapy (IOBNCT). Gold activation wires arranged in a cylindrical water phantom with (void-in-phantom) or without (standard phantom) a cylinder styrene form placed inside were irradiated by using the epithermal beam (ENB) and the mixed thermal-epithermal beam (TNB-1) at the Japan Research Reactor No 4. With ENB, we observed a flattened distribution of thermal neutron flux and a significantly enhanced thermal flux delivery at a depth compared with the results of using TNB-1. The thermal neutron distribution derived from both the ENB and TNB-1 was significantly improved in the void-in-phantom, and a double high dose area was formed lateral to the void. The flattened distribution in the circumference of the void was observed with the combination of ENB and the void-in-phantom. The measurement data suggest that the ENB may provide a clinical advantage in the form of an enhanced and flattened dose delivery to the marginal tissue of a post-operative cavity in which a residual and/or microscopically infiltrating tumour often occurs. The combination of the epithermal neutron beam and IOBNCT will improve the clinical results of BNCT for brain tumours. PMID:12171329

Yamamoto, T; Matsumura, A; Yamamoto, K; Kumada, H; Shibata, Y; Nose, T

2002-07-21

76

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

77

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

2014-08-01

78

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

79

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

80

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

81

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

82

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

83

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

84

Velocity and concentration distribution in a Stefan diffusion tube  

NASA Technical Reports Server (NTRS)

Numerical solutions for the diffusion- and gravity-driven flow in a cylindrical Stefan tube were obtained from the coupled diffusion and Navier-Stokes equations of Peclet numbers 0.3, 1 and 5. Distributions of binary component concentrations and velocities were calculated. The mass average velocity is parabolic in nature, except at high Peclet numbers. The solvent is not stagnant but recirculates, even in the absence of gravity. Radial concentration gradients develop which act convectively destabilizing. Consequences for the deduction of diffusion coefficients from Stefan tube experiments are discussed.

Markham, B. L.; Rosenberger, F.

1980-01-01

85

Inhomogeneous Concentration Distribution in Obliquely Evaporated Fe-Cu Films  

NASA Astrophysics Data System (ADS)

A distribution of atoms or local concentration in FexCu1-x films prepared by an oblique incident beam is discussed based on the results of the magnetization, Mössbauer effect, X-ray diffraction and simulation of a film-formation process. From these experiments, it was concluded that an inhomogeneous concentration distribution takes place in a column which is formed by oblique incidence. In each column three kinds of regions (Fe, Fe-Cu and Cu) are found, depending on the iron contents (x) and the incidence angles (?). When ? is small, only an Fe-Cu region appears; this is an Fe-rich (bcc) or Cu-rich (fcc) alloy corresponding to large or small x, respectively. When ? is large, Fe and Cu regions appear instead of Fe-Cu regions; also, x affects the volume ratio of the Fe to Cu regions.

Keitoku, Susumu; Kamimori, Tatsuo; Goto, Mitita

1986-11-01

86

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

87

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

88

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

PubMed Central

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

1992-01-01

89

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

90

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

PubMed

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

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

2008-05-21

91

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

92

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

93

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. CI is an index related to the rainfall intensity and erosive capacity; therefore, this index is of great interest for studies on torrential rainfall and floods. 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 CI results allowed the identification of three climate 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, except for the region of Biskra (CI = 0.70); and the southern region of the country, with high rainfall concentrations with values between 0.62 and 0.69.

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

2015-03-01

94

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

95

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

E-print Network

(µ-XRF) and Fourier transformed infrared (µ-FTIR) spectroscopy. Even though µ-XRF and µ-FTIR can a smooth surface. The thin sections were then analyzed using µ-XRF on Beamline 10.3.1 and µ-FTIR concentrations. Additional FTIR scans were collected on various known soil minerals, including the B minerals

96

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

97

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

98

Some physical properties of compacted specimens of highly dispersed boron carbide and boron suboxide  

Microsoft Academic Search

Structure, shear modulus and internal friction (IF) of compacted specimens of boron carbide and boron suboxide have been investigated. Microtwins and stacking faults were observed along the {100} plane systems of polycrystalline specimens of boron carbide. Electrical conductivity of the specimens was that of p-type. Concentration of holes varied from 1017 to 1019cm?3. The IF was measured in the temperature

Otar Tsagareishvili; David Lezhava; Mamuka Tushishvili; Levan Gabunia; Marina Antadze; Luiza Kekelidze; Teimuraz Dzigrashvili

2004-01-01

99

Minimum inhibitory concentration distribution in environmental Legionella spp. isolates.  

PubMed

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

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

2014-12-01

100

Boron-10 concentration measurements using the solid-state nuclear track detector CR-39 and automatic image analysis  

SciTech Connect

Calibration curves are determined for measuring the concentration of /sup 10/B in the blood of rats using an autoradiographic procedure, with the polycarbonate solid-state nuclear track detector CR-39 and an image analysis system for automatic track counting. The calibration curves indicate that for the etch procedure used, the nitrogen concentration in the blood is an important interfering input for /sup 10/B concentration measurements. By discriminating against small racks, the sensitivity to the blood nitrogen concentration can be reduced to the point that a variation in the nitrogen weight fraction of 0.01 g N/g blood causes a variation in the predicted /sup 10/B concentration of 0.3 {mu}g /sup 10/B/ml blood.

Blue, T.E.; Roberts, T.C.; Barth, R.F.; Talnagi, J.W.; Alam, F. (Ohio State Univ., Columbus, OH (USA). Nuclear Engineering Program)

1987-05-01

101

Analysis of genetic factors that control shoot mineral concentrations in rapeseed ( Brassica napus ) in different boron environments  

Microsoft Academic Search

Mineral nutrients are essential for plant cell function, and understanding the genetic and physiological basis of mineral\\u000a concentration is therefore important for the development of nutrient-efficient crop varieties that can cope with a shortage\\u000a of mineral resources. In the present study, we investigated the profiles of B, Ca, Fe, Cu, Mg, P and Zn concentrations in\\u000a shoots and analyzed the

Jia Liu; Jinpeng Yang; Ruiyuan Li; Lei Shi; Chunyu Zhang; Yan Long; Fangsen Xu; Jinling Meng

2009-01-01

102

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

DOEpatents

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

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

1987-04-28

103

Sensitivity of regional ozone concentrations to temporal distribution of emissions  

NASA Astrophysics Data System (ADS)

Temporal representations of emissions bear large uncertainty. Before any costly efforts are undertaken to improve the accuracy of temporal emission profiles, however, the impact of their uncertainty on predictions of surface O 3 concentrations should be examined. In this study, a 3-D air quality modeling system was used to probe the sensitivity of regional surface O 3 concentrations to temporal allocation of emissions over the continental US. The raw emissions inventory was processed using SMOKE and was segmented into hourly intervals using both "time-varying" and "uniform" temporal profiles of anthropogenic sources. Our simulation results show that, on average and with the grid resolution (90 km) used, regional daytime O 3 concentrations are not sensitive to changes in the temporal allocation of emissions, while nighttime O 3 concentrations are lower under "uniform" profiles than under "time-varying" profiles.

Tao, Zhining; Larson, Susan M.; Williams, Allen; Caughey, Michael; Wuebbles, Donald J.

104

Direct current sputtering of boron from boron/boron 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. 2 figures.

Timberlake, J.R.; Manos, D.; Nartowitz, E.

1994-12-13

105

Some physical properties of compacted specimens of highly dispersed boron carbide and boron suboxide  

NASA Astrophysics Data System (ADS)

Structure, shear modulus and internal friction (IF) of compacted specimens of boron carbide and boron suboxide have been investigated. Microtwins and stacking faults were observed along the {100} plane systems of polycrystalline specimens of boron carbide. Electrical conductivity of the specimens was that of p-type. Concentration of holes varied from 10 17 to 10 19 cm -3. The IF was measured in the temperature range 80-300 K. It was shown that the IF of boron carbide and that of boron suboxide were characterized with a set of similar relaxation processes. Mechanisms of the relaxation processes in boron carbide and boron suboxide are discussed in terms of the Hasiguti model of interaction between dislocations and point defects.

Tsagareishvili, Otar; Lezhava, David; Tushishvili, Mamuka; Gabunia, Levan; Antadze, Marina; Kekelidze, Luiza; Dzigrashvili, Teimuraz

2004-02-01

106

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

107

Spatial distribution of on-road black carbon concentrations  

EPA Science Inventory

Large spatial variations of black carbon (BC) concentrations in the on-road and near-road environments necessitate measurements with high spatial resolution to assess exposure accurately. A series of measurements was made comparing the performance of several different BC instrume...

108

Characterization of electrodeposited elemental boron  

SciTech Connect

Elemental boron was produced through electrowinning from potassium fluoroborate dissolved in a mixture of molten potassium fluoride and potassium chloride. The characteristics of the electrodeposited boron (raw boron) as well as the water and acid-leached product (processed boron) were studied. The chemical purity, specific surface area, size distribution of particles and X-ray crystallite size of the boron powders were investigated. The morphology of the deposits was examined using scanning electron microscopy (SEM). The chemical state of the matrix, as well as the impurity phases present in them, was established using X-ray photoelectron spectroscopy (XPS). In order to interpret and understand the results obtained, a thermodynamic analysis was carried out. The gas-phase corrosion in the head space as well as the chemistry behind the leaching process were interpreted using this analysis. The ease of oxidation of these powders in air was investigated using differential thermal analysis (DTA) coupled with thermogravimetry (TG). From the results obtained in this study it was established that elemental boron powder with a purity of 95-99% could be produced using a high temperature molten salt electrowinning process. The major impurities were found to be oxygen, carbon, iron and nickel.

Jain, Ashish [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India); Anthonysamy, S. [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India)], E-mail: sas@igcar.gov.in; Ananthasivan, K.; Ranganathan, R. [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India); Mittal, Vinit; Narasimhan, S.V. [Water and Steam Chemistry Division, BARC (F), Kalpakkam, 603102 (India); Vasudeva Rao, P.R. [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India)

2008-07-15

109

Impact of Moving Objects on Contaminant Concentration Distributions in an Inpatient Ward with  

E-print Network

Moving objects can disturb stratified flow and contaminant concentration gradient in an inpatient ward1 Impact of Moving Objects on Contaminant Concentration Distributions in an Inpatient Ward's bed, and the swinging of the entrance door for up to four seconds, on the contaminant concentration

Chen, Qingyan "Yan"

110

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

SciTech Connect

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

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

1981-04-01

111

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

112

Boron-enhanced diffusion of boron from ultralow-energy boron implantation  

SciTech Connect

The authors have investigated the diffusion enhancement mechanism of BED (boron enhanced diffusion), wherein the boron diffusivity is enhanced three to four times over the equilibrium diffusivity at 1,050 C in the proximity of a silicon layer containing a high boron concentration. It is shown that BED is associated with the formation of a fine-grain polycrystalline silicon boride phase within an initially amorphous Si layer having a high B concentration. For 0.5 keV B{sup +}, the threshold implantation dose which leads to BED lies between 3 {times} 10{sup 14} and of 1 {times} 10{sup 15}/cm{sup {minus}2}. Formation of the shallowest possible junctions by 0.5 keV B{sup +} requires that the implant dose be kept lower than this threshold.

Agarwal, A.; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C. [Lucent Technologies, Murray Hill, NJ (United States). Bell Labs.; Haynes, T.E. [Oak Ridge National Lab., TN (United States). Solid State Div.; Erokhin, Y.E. [Eaton Corp., Beverly, MA (United States)

1998-05-03

113

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

114

Statistical distributions of airborne PCB and pesticide concentrations measured at regional sites on the Great Lakes  

SciTech Connect

The purpose of this paper is to report results of testing measured concentrations of total PCBs and ten chlorinated pesticides in air and precipitation in the Great Lakes area for goodness-of-fit to the log normal distribution. Samples were collected at sites on Lakes Superior, Michigan, Erie, and Ontario in 1991--1993. With very few exceptions, distributions of concentrations in the gas and particle phases and in precipitation were not significantly different from log normal.

Gatz, D.F.; Sweet, C.W.; Basu, I.; Harlin, K.S. [Illinois State Water Survey, Champaign, IL (United States)

1994-12-31

115

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

116

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

117

Pressure-dependent boron isotopic fractionation observed by column chromatography  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

118

Preparation and characterization of superhard boron-suboxide films  

Microsoft Academic Search

Boron-suboxide films with hardness reaching 44 GPa, the highest record ever achieved, were synthesized. The films with such high hardness had an oxygen\\/boron atomic concentration ratio of 0.05 and a carbon concentration of about 20 at. %. They were deposited on silicon at 750 °C by simple sputtering. In the range of oxygen\\/boron ratio varying from 0.06 to 0.3, the

H. Huang; C. W. Ong; B. Zheng; R. W. M. Kwok; W. M. Lau; J. W. He

2003-01-01

119

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

120

A Novel Method of Boron Delivery Using Sodium Iodide Symporter for Boron Neutron Capture Therapy  

PubMed Central

Boron Neutron Capture Therapy (BNCT) effectiveness depends on the preferential sequestration of boron in cancer cells relative to normal tissue cells. We present a novel strategy for sequestering boron using an adenovirus expressing the sodium iodide symporter (NIS). Human glioma grown subcutaneously in athymic mice and orthotopic rat brain tumors were transfected with NIS using a direct tumor injection of adenovirus. Boron bound as sodium tetrafluoroborate (NaBF4) was administered systemically several days after transfection. Tumors were excised hours later and assessed for boron concentration using inductively coupled plasma atomic emission spectroscopy. In the human glioma transfected with NIS, boron concentration was more than 10 fold higher with 100 mg/kg of NaBF4, compared to tumor not transfected. In the orthotopic tumor model, the presence of NIS conferred almost 4 times the boron concentration in rat tumors transfected with human virus compared with contralateral normal brain not transfected. We conclude that adenovirus expressing NIS has the potential to be used as a novel boron delivery agent and should be explored for future clinical applications. PMID:20921830

KUMAR, Sanath; FREYTAG, Svend O.; BARTON, Kenneth N.; BURMEISTER, Jay; JOINER, Michael C.; SEDGHI, Bijan; MOVSAS, Benjamin; BINNS, Peter J.; KIM, Jae Ho; BROWN, Stephen L.

2013-01-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

122

Unconventional charge distribution in the planar wheel-type M©B6H6(-/0/+) (M = Mn, Fe and Co): central M with negative charges and peripheral boron ring with positive charges.  

PubMed

Planar wheel-type D6h M©B6H6(-/0/+) (M = Mn, Fe and Co for anion, neutral and cation, respectively.) clusters with a planar hexacoordinate transition-metal at the center of the boron ring were designed and investigated by density functional theory. These planar clusters are chemically stable as a result of their large binding energy, vertical ionization potential, and vertical electron affinity. The detailed natural population and molecular orbital analyses suggest that not only does the M atom donate electrons to the boron ring for participation in the ?-delocalized bonding, but also the boron ring donates electrons back to the M atom for the formation of the ?-delocalized bonding, which leads to a strong aromaticity and unconventional charge distribution, i.e., the M atom is negatively charged, while the boron ring is positively charged. This study may open a new area in coordination chemistry for planar hexacoordinate transition metals and we expect further experimental exploration of their synthesis and potential applications. PMID:25830384

Hou, Jianhua; Duan, Qian; Qin, Jieming; Shen, Xiande; Zhao, Jianxun; Liang, Qingcheng; Jiang, Dayong; Gao, Shang

2015-04-01

123

Female offspring of rat dams fed low boron diets during pregnancy and lactation exhibit signs of the metabolic syndrome during early adulthood: increased body weight, & serum triglycerides and total cholesterol concentrations  

Technology Transfer Automated Retrieval System (TEKTRAN)

To expand on reports from this laboratory that low dietary boron may affect energy substrate utilization, we determined whether low dietary boron during early development promotes manifestation of the metabolic syndrome in adult offspring. Sprague-Dawley dams were fed either a boron-low (BL; ~0.1 mg...

124

Distribution of terbium and increase in calcium concentrations in organs of mice administered with terbium chloride.  

PubMed

To investigate the biological effects of terbium (Tb), male mice were intraperitoneally administered with TbCl3 at doses of 10, 50, or 250 mg Tb/kg. The Tb distribution in organs was determined after 18-20 h of injection by using a spectrofluorometer. The concentrations of Ca, Mg, Fe, and Zn in various organs were determined by atomic absorption spectrometer. Tb administered was mainly found in pancreas, seminal vesicles, spleen, liver, and testes. In each organ. Tb concentration increased according to the dosage of Tb. Contrary to our expectation, the increase of Ca concentration was obvious in organs in which high Tb concentrations were found. The correlation coefficients between Tb and Ca concentrations were from 0.863 in spleen to 0.986 in liver. In heart, lung, and blood. Tb was scarcely detected and insignificant change of Ca concentrations was observed. This result suggests that Tb induces increased Ca concentrations in organs. PMID:1996470

Shinohara, A; Chiba, M

1991-02-11

125

Effect of bevacizumab treatment on p-boronophenylalanine distribution in murine tumor  

PubMed Central

Previous studies have demonstrated that angiogenesis inhibitors can enhance tumor inhibitory effects of chemo- and radiotherapy via their action on tumor vessels. Here, we studied the effect of the angiogenesis inhibitor, bevacizumab (Avastin), on boron distribution in a murine tumor model. The human head and neck squamous cell carcinoma cell line was used for inoculation into mice. Boron-10 concentrations in tissues were measured by prompt ?-ray spectrometry (PGA). Hoechst 33342 perfusion and p-boronophenylalanine (BPA) distribution were determined by immunofluorescence staining. Our results revealed enhanced tumor blood perfusion and BPA accumulation in tumors after Avastin treatment, suggesting that combination of angiogenesis inhibition with treatment with boron compound administration may improve the efficacy of boron neutron capture therapy (BNCT) by modifying tumor vessels. In addition, our results also demonstrated the usefulness of immunofluorescence staining for investigating boron compound distribution at the cellular level. PMID:23135099

Liu, Yong; Suzuki, Minoru; Masunaga, Shin-ichiro; Chen, Yi-Wei; Kashino, Genro; Tanaka, Hiroki; Sakurai, Yoshinori; Kirihata, Mitsunori; ONO, Koji

2013-01-01

126

The Potential Distribution Between Parallel Plates and Concentric Cylinders Due to Any Arbitrary Distribution of Space Charge  

Microsoft Academic Search

Equations are derived for the electric potential and field intensity due to a distribution of space charge in a slab of dielectric between two infinite parallel conducting plates. The charge density may be any integrable function of the coordinate perpendicular to the plates. The corresponding solution for concentric cylinders is also given. A number of special cases are discussed, including

W. G. Cady

1935-01-01

127

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

128

PLIF measurement of fuel concentration distribution in transient hydrogen jet flame  

SciTech Connect

To know the concentration field of fuel spray or jet is very important because the following combustion process strongly depends on it. Recently, planar laser induced fluorescence (PLIF) measurement is often used to clarify two-dimensional concentration field of fuel and other species. In this study, PLIF measurement was applied to investigate the concentration distribution of a transient hydrogen jet with combustion. The jet penetrates with entraining ambient air and hydrogen is mixed with the air. Each experimental run of the jet shows different configuration and concentration distribution although averaged jet shows axisymmetric ones. Normalized concentration in radial direction presents Gaussian distribution and normalized concentration in axial direction is expressed by the relation inverse to the axial direction. The mixture was ignited near the nozzle exit after some delay time (t = 3.6ms) during injection ({approximately}11ms). For example, the fuel concentration in the transient jet at t = 1.0 and 1.4ms after the spark ignition (t = 4.6 and 5.0 ms respectively) was obtained as shown in a figure. The behavior of the flame development was measured in the transient flame jet by analyzing these images. The velocities of the jet and flame tips were also determined.

Tomita, Eiji; Hamamoto, Yoshisuke; Yoshiyama, Sadami; Toda, Hitoshi

1999-07-01

129

Research and Design of Distributed Carbon Monoxide (CO) Concentration On-Line Detection System  

Microsoft Academic Search

A kind of carbon monoxide (CO) density distributed on-line detection system is designed based on single chip microprocessor (SCM) technology and CAN bus technology, etc. Collection signal by sensor is converted by conditioning circuit and sent into SCM AT89C51. When CO concentration beyond setting limits value, field alarming and ventilation equipment are droved to start, which assures CO concentration value

Xinling Wen

2008-01-01

130

Boron incorporation in the foraminifer Amphistegina lessonii under a decoupled carbonate chemistry  

NASA Astrophysics Data System (ADS)

A number of studies have shown that the boron isotopic composition (?11B) and the B/Ca ratio of biogenic carbonates (mostly foraminifers) can serve as proxies for two parameters of the ocean's carbonate chemistry, rendering it possible to calculate the entire carbonate system. However, the B incorporation mechanism into marine carbonates is still not fully understood and analyses of field samples show species specific and hydrographic effects on the B proxies complicating their application. Identifying the carbonate system parameter influencing boron incorporation is difficult due to the co-variation of pH, CO32-, and B(OH)4-. To shed light on the question which parameter of the carbonate system is related to the boron incorporation, we performed culture experiments with the benthic symbiont-bearing foraminifer Amphistegina lessonii using a decoupled pH-CO32- chemistry. The determination of the boron isotopic composition and B/Ca ratios was performed simultaneously by means of a new in situ technique combining optical emission spectroscopy and laser ablation MC-ICP-MS. The boron isotopic composition in the tests gets heavier with increasing pH and B/Ca increases with increasing BOH4-/HCO3- of the culture media. The latter indicates that boron uptake of A. lessonii features a competition between B(OH)4- and HCO3-. Furthermore, the simultaneous determination of B/Ca and ?11B on single specimens allows for assessing the relative variability of these parameters. Among different treatments the B/Ca shows an increasing variability with increasing boron concentration in the test whereas the variability in the isotope distribution is constant.

Kaczmarek, K.; Langer, G.; Nehrke, G.; Horn, I.; Misra, S.; Janse, M.; Bijma, J.

2014-12-01

131

Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column  

Microsoft Academic Search

The use of optical fibers in a fluorescence-detection scheme permits the accurate determination of the radial distribution of the transit time, the column efficiency, and the analyte concentration at the exit of a chromatographic axial-compression column (50 mmID). The results obtained demonstrate that the column is not homogeneous, but suggest a nearly cylindrical distribution of the packing density. The average

Tivadar Farkas; Michael J. Sepaniak; Georges Guiochon

1997-01-01

132

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

133

Controls on boron and germanium distribution in the low-sulfur Amos coal bed, Western Kentucky coalfield, USA  

USGS Publications Warehouse

The Duckmantian-aged Amos coal bed is a thin (<51 cm) coal bed that occurs in lobate southwest-trending pods separated by thin sandstones in the Western Kentucky coalfield. The coal bed, which is comprised of up to two benches and a rider coal, is low in ash yield (<6%) and sulfur content (<1%). The coal tends to be thin (<40 cm), but it was heavily mined in the 1980s because it could be combusted as mined. Geochemical analysis of the Amos coal bed shows higher concentrations of B and Ge than other Western Kentucky coal beds. High total B concentrations as well as high B/Be, both considered to be indicators of marine environments, increase toward the top of the coal bed. Most of the B values for the Amos samples range from 66 to 103 ppm (whole coal basis) indicating deposition in a brackish environment. High Ge concentrations in coals have been considered to be a function of seam thickness and proximity to the top and bottom of the coal bed. Thin coals, such as the Amos, are dominated by the coal bed margins and, therefore, have a tendency to have relatively high Ge concentrations. In the case of the Amos coal bed, the lower bench has a higher Ge content, suggesting that the substrate was a more important source of Ge than the roof rock. ?? 2002 Elsevier Science B.V. All rights reserved.

Hower, J.C.; Ruppert, L.F.; Williams, D.A.

2002-01-01

134

Effect of dietary boron on the aging process.  

PubMed Central

Total boron concentrations in Drosophila changed during development and aging. The highest concentration of boron was found during the egg stage, followed by a decline during the larval stages. Newly emerged flies contained 35.5 ppm boron. During the adult stage the boron concentration increased by 52% by 9 weeks of age. Adding excess dietary boron during the adult stage decreased the median life span by 69% at 0.01 M sodium borate and by 21% at 0.001 M sodium borate. Lower concentrations gave small but significant increases in life span. Supplementing a very low boron diet with 0.00025 M sodium borate improved life span by 9.5%. The boron contents of young and old mouse tissues were similar to those of Drosophila and human samples. Boron supplements of 4.3 and 21.6 ppm in the drinking water, however, did not significantly change the life span of old mice fed a diet containing 31.1 ppm boron. PMID:7889879

Massie, H R

1994-01-01

135

An experimental study of flow-induced fiber orientation and concentration distributions in a concentrated suspension flow through a slit channel containing a cylinder  

Microsoft Academic Search

Flow-induced fiber orientation and concentration distributions were measured in a concentrated fiber suspension (CFS) and a dilute one (DFS). The channel has a thin slit geometry containing a circular cylinder. In the previous work, many researchers have qualitatively studied fiber orientation and concentration distributions in injection-molded products of fiber-reinforced plastics. In the present work, however, they are quantitatively estimated by

Kazunori Yasuda; Tatsuro Kyuto; Noriyasu Mori

2004-01-01

136

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

137

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

138

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

EPA Science Inventory

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

139

The impact of variable hydraulic operation of water distribution networks on disinfection by-product concentrations  

Microsoft Academic Search

This study assessed the magnitude of variations in the concentrations of disinfection by-products, specifically trihalomethanes and haloacetic acids, which occur in two UK water distribution networks of different sizes due to changes in the hydraulic operation of the networks. These operational changes included varying the fill levels of water storage tanks and pumping conditions within the network. This was investigated

Emesomake Idornigie; Michael R. Templeton; Cedo Maksimovic; Suzan Sharifan

2010-01-01

140

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

E-print Network

of analysis of Distributed Concentrating Solar Combined Heat and Power (DCS-CHP) systems is a design of solar thermal (REN21 [29]), there is a large proven market for solar energy. With widespread marketWh electric and $0.03/kWh thermal), and cost of solar water purification/desalination ($1.40/m3

California at Berkeley, University of

141

Concentration and size distribution of ultrafine particles near a major highway.  

PubMed

Motor vehicle emissions usually constitute the most significant source of ultrafine particles (diameter <0.1 microm) in an urban environment, yet little is known about the concentration and size distribution of ultrafine particles in the vicinity of major highways. In the present study, particle number concentration and size distribution in the size range from 6 to 220 nm were measured by a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), respectively. Measurements were taken 30, 60, 90, 150, and 300 m downwind, and 300 m upwind, from Interstate 405 at the Los Angeles National Cemetery. At each sampling location, concentrations of CO, black carbon (BC), and particle mass were also measured by a Dasibi CO monitor, an aethalometer, and a DataRam, respectively. The range of average concentration of CO, BC, total particle number, and mass concentration at 30 m was 1.7-2.2 ppm, 3.4-10.0 microg/m3, 1.3-2.0 x 10(5)/cm3, and 30.2-64.6 microg/m3, respectively. For the conditions of these measurements, relative concentrations of CO, BC, and particle number tracked each other well as distance from the freeway increased. Particle number concentration (6-220 nm) decreased exponentially with downwind distance from the freeway. Data showed that both atmospheric dispersion and coagulation contributed to the rapid decrease in particle number concentration and change in particle size distribution with increasing distance from the freeway. Average traffic flow during the sampling periods was 13,900 vehicles/hr. Ninety-three percent of vehicles were gasoline-powered cars or light trucks. The measured number concentration tracked traffic flow well. Thirty meters downwind from the freeway, three distinct ultrafine modes were observed with geometric mean diameters of 13, 27, and 65 nm. The smallest mode, with a peak concentration of 1.6 x 10(5)/cm3, disappeared at distances greater than 90 m from the freeway. Ultrafine particle number concentration measured 300 m downwind from the freeway was indistinguishable from upwind background concentration. These data may be used to estimate exposure to ultrafine particles in the vicinity of major highways. PMID:12269664

Zhu, Yifang; Hinds, William C; Kim, Seongheon; Sioutas, Constantinos

2002-09-01

142

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

143

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

144

concentration  

Microsoft Academic Search

The rapid development in our under- standing of the regulation of enzyme activity makes it a high priority to ascertain whether the behavior of purified enzymes reflects their functional characteristics in vivo. Enzyme concentration is usually the most significant difference between routine in vitro assays and in vivo conditions, as it is well known that many intracel- lular enzymes are

JUAN J. ARAGON; ALBERTO SOLS

145

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

146

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

147

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

148

Studies on depth-dose-distribution controls by deuteration and void formation in boron neutron capture therapy.  

PubMed

Physical studies on (i) replacement of heavy water for body water (deuteration), and (ii) formation of a void in human body (void formation) were performed as control techniques for dose distribution in a human head under neutron capture therapy. Simulation calculations were performed for a human-head-size cylindrical phantom using a two-dimensional transport calculation code for mono-energetic incidences of higher-energy epi-thermal neutrons (1.2-10 keV), lower-energy epi-thermal neutrons (3.1-23 eV) and thermal neutrons (1 meV to 0.5 eV). The deuteration was confirmed to be effective both in thermal neutron incidence and in epi-thermal neutron incidence from the viewpoints of improvement of the thermal neutron flux distribution and elimination of the secondary gamma rays. For the void formation, a void was assumed to be 4 cm in diameter and 3 cm in depth at the surface part in this study. It was confirmed that the treatable depth was improved almost 2 cm for any incident neutron energy in the case of the 10 cm irradiation field diameter. It was made clear that the improvement effect was larger in isotropic incidence than in parallel incidence, in the case that an irradiation field size was delimited fitting into a void diameter. PMID:15379019

Sakurai, Yoshinori

2004-08-01

149

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

SciTech Connect

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

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

2000-08-15

150

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

151

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

PubMed Central

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.

1994-01-01

152

Characterization of ultrafine particle number concentration and size distribution during a summer campaign in southwest Detroit.  

PubMed

This paper presents results from a study conducted in southwest Detroit from July 20 to July 30, 2002, to characterize ambient ultrafine particles (dP < 0.1 microm), and to examine the effect of local sources and meteorological parameters on the ultrafine number concentration and size distribution. The number concentrations of ambient particles in the size range of 0.01-0.43 microm were obtained from a scanning mobility particle sizer (SMPS). Meteorological parameters including ambient temperature, relative humidity, wind speed, wind direction, rainfall, and solar radiation flux were also monitored concurrently atop a 10-m tower. On average, ultrafine particles ranged from 1.4 x 10(4) to 2.5 x 10(4) cm(-3), with significant diurnal and daily variations, and accounted for approximately 89% of the total number concentration (0.01 < dP < 0.43 microm). Time-series plots of the 5-min number concentrations revealed that peak concentrations often occurred during morning rush hour and/or around solar noon when photochemical activity was at a maximum. The morning traffic-related peak coincided with the NOx peak, whereas the photochemical-related peak correlated with solar radiation flux. On some days, the noon peak concentration was many times higher than the morning peak concentration. Although the number size distribution varied considerably over the course of the study, it typically exhibited one to three modes, with diameters around 0.01, 0.05, and 0.09 microm. Analysis of the influence of wind direction indicated that stationary sources could be one of the contributors to elevated ultrafine particle concentration. Overall, the data indicated that fossil fuel combustion and atmospheric gas-to-particle conversion of precursor gases are the major sources of ultrafine particles in the southwest Detroit area during the summer. PMID:15468661

Young, Li-Hao; Keeler, Gerald J

2004-09-01

153

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

PubMed

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

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

2014-09-01

154

Effects of microgravity on growth hormone concentration and distribution in plants  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

155

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

PubMed

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

Yao, Ling; Lu, Ning

2014-08-01

156

Boron nitride: Composition, optical properties and mechanical behavior  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

157

Boron nitride: composition, optical properties and mechanical behavior  

SciTech Connect

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

Pouch, J.J.; Alterovitz, S.A.; Miyoshi, K.; Warner, J.D.

1987-04-01

158

Boron nitride - Composition, optical properties, and mechanical behavior  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

159

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

160

Direct imaging of boron segregation to extended defects in silicon  

NASA Astrophysics Data System (ADS)

Silicon was implanted with a high boron dose (5×1015 at. cm-2) at 30 keV and further annealed at 950 °C for 30 s. The sample was analyzed using transmission electron microscopy (TEM) and atom probe tomography (APT). TEM images revealed the presence of a high density of dislocation loops (˜1011/cm-2) distributed around the projected range of implanted atoms. APT reconstructions showed local enrichment of boron in the form of loops that were interpreted as Cottrell atmosphere. Boron enriched rods, interpreted as the {113} defects, were also observed. Segregation energies of boron atoms to these defects were estimated to be ˜0.35 eV.

Duguay, S.; Philippe, T.; Cristiano, F.; Blavette, D.

2010-12-01

161

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

162

Quantitative Analysis of Boron with Solid State Track Detector  

Microsoft Academic Search

In a study aimed at the application of solid state track detectors to the quantitative analysis of boron, track detector plates of cellulose nitrate were set in polypropylene test tubes, filled with various concentrations of boron-agar solution, and irradiated with thermal neutrons. After irradiation, the cellulose track detectors were separated from the solution, and etched with suitable chemical reagents. The

Takao TSURUTA; Mitsuyoshi YAZAKI

1977-01-01

163

Boron-loaded photographic plates as detectors of slow neutrons  

Microsoft Academic Search

The variations with position in the plate of the emulsion thickness and of the number of slow neutrons recorded per unit area have been determined for a 10 in. × 8 in. × 100 ? boron-loaded plate that had been irradiated uniformly with slow neutrons. The measurements were consistent with a constant concentration of boron throughout the plate and upper

A R Baker

1954-01-01

164

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

165

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

166

Characterization of background concentrations of contaminants using a mixture of normal distributions.  

PubMed

We present a Bayesian approach for characterizing background contaminant concentration distributions using data from sites that may have been contaminated. Our method, focused on estimation, resolves several technical problems of the existing methods sanctioned by the U.S. Environmental Protection Agency (USEPA) (a hypothesis testing based method), resulting in a simple and quick procedure for estimating background contaminant concentrations. The proposed Bayesian method is applied to two data sets from a federal facility regulated under the Resource Conservation and Restoration Act. The results are compared to background distributions identified using existing methods recommended by the USEPA. The two data sets represent low and moderate levels of censorship in the data. Although an unbiased estimator is elusive, we show that the proposed Bayesian estimation method will have a smaller bias than the EPA recommended method. PMID:17051794

Qian, Song S; Lyons, Regan E

2006-10-01

167

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

Microsoft Academic Search

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

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

2006-01-01

168

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

169

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

NASA Astrophysics Data System (ADS)

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 be related to the CoFeB crystallization process which begins from the under CoFeB/Ru interface and pushes boron atoms to diffuse into the MgO barrier during annealing.

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

2010-08-01

170

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

171

B-scan ultrasound imaging measurement of suspended sediment concentration and its vertical distribution  

NASA Astrophysics Data System (ADS)

In this paper, a novel approach based on B-scan ultrasound imaging is presented to measure suspended sediment concentration (SSC) and its vertical distribution. The relationship between ultrasonic imaging signals and SSCs has been described by specially designed experiments on both natural and plastic sand. Three parameters for imaging measurement are introduced to characterise their relationships: imaging concentration (IC), greyscale concentration (GC) and energy concentration (EC). It is confirmed that these parameter values increase with the sand added in the case of low SSC. Compared with the IC and EC, GC is more suitable for expressing their relationships, which can be used to measure the unknown SSC. The possible influences of particle size, material quality and flow velocity on the relationships are also briefly discussed. Characterised by direct observation, high sensitivity and real-time processing performance, this method has proved suitable for the measurement of SSC below 5.0‰ by volume or approx. 10?kg?m?3 by weight, especially for the measurement of vertical sedimentary distribution in the movable-bed model experiment.

Zou, Xian-jian; Ma, Zhi-min; Zhao, Xiao-hong; Hu, Xiang-yang; Tao, Wei-liang

2014-11-01

172

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. PMID:23267396

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

2012-01-01

173

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

174

Electrical Properties of Silicon Containing Arsenic and Boron  

Microsoft Academic Search

Electrical conductivity and Hall effect have been measured from 10° to 1100° Kelvin on single-crystal silicon containing arsenic and boron. Extrinsic carrier concentration is computed from Hall coefficient. Analysis of extrinsic carrier concentration indicates the ionization energy of arsenic donor levels to be 0.049 ev and of boron acceptor levels to be 0.045 ev for low impurity concentrations. Fermi degeneracy

F. J. Morin; J. P. Maita

1954-01-01

175

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

176

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

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

177

Boron incorporation in the foraminifer Amphistegina lessonii under a decoupled carbonate chemistry  

NASA Astrophysics Data System (ADS)

A number of studies have shown that the boron isotopic composition (?11B) and the B / Ca ratio of biogenic carbonates (mostly foraminifers) can serve as proxies for two parameters of the ocean's carbonate chemistry, rendering it possible to calculate the entire carbonate system. However, the B incorporation mechanism into marine carbonates is still not fully understood and analyses of field samples show species-specific and hydrographic effects on the B proxies complicating their application. Identifying the carbonate system parameter influencing boron incorporation is difficult due to the co-variation of pH, CO32- and B(OH)4-. To shed light on the question which parameter of the carbonate system is related to the boron incorporation, we performed culture experiments with the benthic symbiont-bearing foraminifer Amphistegina lessonii using a decoupled pH-CO32- chemistry. The determination of the ?11B and B / Ca ratios was performed simultaneously by means of a new in situ technique combining optical emission spectroscopy and laser ablation MC-ICP-MS. The boron isotopic composition in the tests gets heavier with increasing pH and B / Ca increases with increasing B(OH)4- / HCO3- of the culture media. The latter indicates that boron uptake of A. lessonii features a competition between B(OH)4- and HCO3-. Furthermore, the simultaneous determination of B / Ca and ?11B on single specimens allows for assessing the relative variability of these parameters. Among different treatments the B / Ca shows an increasing variability with increasing boron concentration in the test whereas the variability in the isotope distribution is constant.

Kaczmarek, K.; Langer, G.; Nehrke, G.; Horn, I.; Misra, S.; Janse, M.; Bijma, J.

2015-03-01

178

Radial Velocity Distribution of the Galaxies in the Puppis Hidden Concentration Behind the Milky-Way  

NASA Astrophysics Data System (ADS)

We investigate the radial velocity distribution of the galaxies in the Puppis region behind the Milky Way around (l,b)~(245^deg^, 0^deg^), where a concentration of galaxies was recently recognized through the systematic search for galaxies behind the zone of avoidance. Using the lower limit sample of the 6O-micron flux-limited sample of IRAS galaxies brighter than f_60_ = 0.6 Jy, we find a large nearby clustering of galaxies at about 20 h^-1^ Mpc, whose peak spatial density at 7.5h^-1^ Mpc scale is at least twice the whole-sky average. This Puppis concentration is probably associated with the S1 supercluster at (l,b) = (220^deg^, - 15^deg^) detected in the QDOT survey, and this association is likely to be comparable to other nearby superclusters such as the Virgo, the Hydra, the Centaurus and the Fornax-Eridanus superclusters. Consequently, the effect of the Puppis concentration on the peculiar motions of the Local Group and other nearby galaxies should be considerable. There is no prominent individual cluster in the Puppis region, however, although some galaxies are concentrated into the regions around (l,b) = (245^deg^, - 7^deg^) and (237^deg^, - 15^deg^); the richness of these individual clusters in IRAS galaxies is as large as that of the Fornax cluster, and perhaps half or more of that of the Virgo cluster. We also study the radial velocity distribution of the galaxies selected by an optical limiting diameter, although uncertainty in the selection is large because of galactic extinction. The distribution of these diameter-selected galaxies shows good agreement with that of the IRAS-selected ones.

Yamada, T.; Tomita, A.; Saito, M.; Chamaraux, P.; Kazes, I.

1994-09-01

179

Accumulation and loss of arsenic and boron, alone and in combination, in mallard ducks  

SciTech Connect

Arsenic and boron are common in the environment, and wildlife can be exposed to toxic concentrations through both natural and human-influenced processes. The authors exposed adult male mallard ducks to dietary concentrations of 300 ppm arsenic as sodium arsenate, 1,600 ppm boron as boric acid, or both and estimated the tissue accumulation and loss rates when the ducks were returned to uncontaminated food. Both elements were accumulated rapidly; equilibrium levels were reached for arsenic in 10 to 30 d and for boron in 2 to 15 d. Accumulation of each element was slowed by the presence of the other in the diet. Boron was eliminated by mallards very rapidly, with few detectable residues {ge}1 d after removal of boron from the diet; arsenic was also rapidly lost with half-lives of 1 to 3 d (half-lives were not constant throughout the loss period). Arsenic loss rate was not affected by the presence of boron. Arsenic accumulated to the highest level in liver tissue, with blood and brain levels lower; concentrations in the liver and blood were proportional but affected by the presence of boron. Boron concentrations were highest in the blood, followed by the brain and liver; concentrations in the liver and blood were proportional but affected by the presence of boron. Boron concentrations were highest in the blood, followed by the brain and liver; concentrations in the blood and liver were proportional.

Pendleton, G.W.; Whitworth, M.R.; Olsen, G.H. [National Biological Service, Laurel, MD (United States). Patuxent Environmental Science Center

1995-08-01

180

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

181

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

182

Carbon dioxide detection by boron nitride nanotubes  

NASA Astrophysics Data System (ADS)

The effect of gas molecule adsorption is investigated on the density of states of (9,0) zigzag boron nitride nanotube within a random tight-binding Hamiltonian model. The Green function approach and coherent potential approximation have been implemented. The results show that the adsorption of carbon dioxide gas molecules by boron atoms only leads to a donor type semiconductor while the adsorption by nitrogen atoms only leads to an acceptor. Since the gas molecules are adsorbed by both boron and nitrogen atoms, a reduction of the band gap is found. In all cases, increasing the gas concentration causes an increase in the height of the peaks in the band gap. This is due to an increasing charge carrier concentration induced by adsorbed gas molecules.

Mousavi, Hamze; Kurdestany, Jamshid Moradi; Bagheri, Mehran

2012-08-01

183

Parameterization of Buoyancy Effects in Generic PWR Boron Dilution Scenarios  

SciTech Connect

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

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

2006-07-01

184

Spatial and annual temporal distribution of ozone concentrations in the madrid basin using passive samplers.  

PubMed

Passive samplers are useful tools for helping to describe the ozone distribution in complex terrain situations. They are also a good complement to continuous monitoring stations. This paper discusses the results of a pilot study that used ozone passive samplers to describe the spatial and annual temporal distribution of ozone in several forested areas around the city of Madrid. The ozone concentrations around Madrid were found to be higher on the elevated sites located at a certain distance from the city"s urban zone. A seasonal ozone cycle was observed, with maximum concentrations found in the basin in late spring or summer depending on the location. The information obtained allowed us to group the locations into four classes. Altitude and distance to the city during the summer and winter explained the observed ozone concentrations. However, during the transition periods, especially in early spring and to a lesser extent in autumn, there was not a good correlation between ozone levels and elevation or distance from precursor sources. These data strongly suggest that altitudinal gradients for ozone are not always the case in the Madrid Basin. PMID:12805774

Sanz, M J; Sanz, F; Sanchez-Peña, G

2001-11-30

185

The structure of boron in boron fibres  

NASA Technical Reports Server (NTRS)

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

Bhardwaj, J.; Krawitz, A. D.

1983-01-01

186

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

PubMed

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

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

2004-01-01

187

Concentration and size distribution of viable bioaerosols during non-haze and haze days in Beijing.  

PubMed

Accumulation of airborne particulate matter (PM) has profoundly affected the atmospheric environment of Beijing, China. Although studies on health risks have increased, characterization of specific factors that contribute to increased health risks remains an area of needed exploration. Chemical composition studies on PM can readily be found in the literature but researches on biological composition are still limited. In this study, the concentration and size distribution of viable airborne bacteria and fungi were determined in the atmosphere from May to July 2013 in Beijing, China. Samples were collected during non-haze days and haze days based on the value of air quality index (AQI) PM2.5. Multiple linear regression results indicated that concentrations of viable bioaerosol exhibited a negative correlation with PM2.5 (AQI) ranging from 14 to 452. There was a little difference in size distribution of bioaerosol between non-haze and haze days that all airborne bacteria showed skewed trends toward larger sizes and airborne fungi followed a Gaussian distribution. Spearman's correlation analysis showed that a fraction of bioaerosol with fine and coarse particles had negative and positive relations with PM2.5 (AQI), respectively. Moreover, the temporal variation of d g (aerodynamic diameter) of bioaerosol with PM2.5 (AQI) fluctuated from 9:00 to 21:00, which suggested that their deposition pattern would vary during a day. The primary research in this study implied that aerodynamic size variation should be considered in assessing the bioaerosol exposure during haze weather. PMID:25300183

Gao, Min; Qiu, Tianlei; Jia, Ruizhi; Han, Meilin; Song, Yuan; Wang, Xuming

2015-03-01

188

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

189

TIME-AVERAGED TURBULENT MIXING AND VERTICAL CONCENTRATION DISTRIBUTION OF HIGH-DENSITY SUSPENSIONS FORMED UNDER WAVES  

E-print Network

the phenomena of HDS, which showed that there existed an obvious vertical concentration gradient even though1 TIME-AVERAGED TURBULENT MIXING AND VERTICAL CONCENTRATION DISTRIBUTION OF HIGH-averaged suspended sediment concentration model for HDS was developed. To avoid the stability problems

190

Diffusion simulations of boron implanted at low energy (500 eV) in crystalline silicon  

NASA Astrophysics Data System (ADS)

Several models have been proposed for the simulation of boron diffusion during annealing after implantation in silicon. It has been shown that transient enhanced diffusion (TED) tends to disappear at sub-keV implant energies. Under these conditions boron concentration is higher than the boron solubility limit value, precipitation phenomena occur. Extended defects ({3 1 1}, EOR) formation and boron precipitation affect both the redistribution during the annealing and activation of the boron. For these reasons, we have investigated the diffusion of low energy boron implanted in crystalline silicon and tested a complete simulation program which takes into account the effects of type I defects as a sink for self-interstitials and of boron precipitation. Experimental results have been simulated and consistent parameters have been found to fit the data. Boron enhanced diffusion effect has been studied. Model parameter extractions have been discussed.

Ihaddadene-Le Coq, L.; Marcon, J.; Dush-Nicolini, A.; Masmoudi, K.; Ketata, K.

2004-02-01

191

Tight-Binding Quantum Chemical Molecular Dynamics Study on Depth Profile Prediction in Low Energy Boron Implantation Process  

NASA Astrophysics Data System (ADS)

Creation of shallow junction for the future generation LSI is a crucial step in semiconductor industry and low-energy boron implantation process is considered to be a key technology. In this study, we have statistically investigated the effects of orientation of implantation on the dynamic behavior of boron implantation process into hydrogen-terminated Si(001) 2× 1 surface by using our original tight-binding quantum chemical molecular dynamics method, which is over 5,000 times faster than conventional first-principle molecular dynamics method. It was found that depth profile of boron implantation can be controlled by orientation of boron implantation and the shallowest implantation depth was obtained in the case of tilt angle equal to 7° among the investigated tilt angles of 0°, 7°, 15°, 22.5°, 30° and 45° at the initial boron energy of 100 eV. At the boron implantation process of over 1 keV energy the tilt angle of 7° has been employed experimentally and the same tilt angle was predicted to be the best even at low-energy region of 100 eV. Furthermore, we investigated the effect of rotation angle on the depth profile and at all the investigated tilt angles the average implantation depth becomes shallower for rotation angle of 45° that is along < 011> direction, than for rotation angle of 0° that is along < 001>. Hence, the shallowest depth profile was obtained in the case of tilt angle of 7° and rotation angle of 45°, where the distribution of intruded boron atom was more concentrated than for the same tilt angle but rotation angle of 0°. The effect of tilt and rotation angles on the boron implantation process has not been clarified experimentally at low-energy boron implantation process of less than 1 keV and hence we concluded that theoretical optimization of low-energy boron implantation process has been succeeded by means of our original tight-binding quantum chemical molecular dynamics method.

Tsuboi, Hideyuki; Sagawa, Ai; Iga, Hideki; Sasata, Katsumi; Masuda, Tsuyoshi; Koyama, Michihisa; Kubo, Momoji; Broclawik, Ewa; Yabuhara, Hidehiko; Miyamoto, Akira

2005-04-01

192

Imaging shear stress distribution and evaluating the stress concentration factor of the human eye  

PubMed Central

Healthy eyes are vital for a better quality of human life. Historically, for man-made materials, scientists and engineers use stress concentration factors to characterise the effects of structural non-homogeneities on their mechanical strength. However, such information is scarce for the human eye. Here we present the shear stress distribution profiles of a healthy human cornea surface in vivo using photo-stress analysis tomography, which is a non-intrusive and non-X-ray based method. The corneal birefringent retardation measured here is comparable to that of previous studies. Using this, we derive eye stress concentration factors and the directional alignment of major principal stress on the surface of the cornea. Similar to thermometers being used for monitoring the general health in humans, this report provides a foundation to characterise the shear stress carrying capacity of the cornea, and a potential bench mark for validating theoretical modelling of stresses in the human eye in future. PMID:25754336

Joseph Antony, S.

2015-01-01

193

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

PubMed Central

To investigate the distribution of monoamine transmitters at acupoints and effect of acupuncture on it. Take this experiment by means of microdialysis. Twenty rabbits were randomly assigned to two groups (Group A: acupuncture Guanyuan (RN4), Group B: acupuncture nonacupoint which is besides Guanyuan (RN4) 1?cm). Before and after acupuncture was taken, tissue fluids both at Zhongwan (RN12) which is on the same meridian as Guanyuan and at a nonacupoint 1?cm away from Zhongwan were collected through microdialysis, respectively. The collected samples were analyzed to determine concentrations of monoamine transmitters. Epinephrine and 5-HT were detected. An unknown substance was found. Its concentration at acupoint was significantly higher than that at nonacupoint and decreased after acupuncture. Its significant specificity at acupoints suggests that it may play an important role in meridian's activity. PMID:25544852

Guo, Yi

2014-01-01

194

Imaging shear stress distribution and evaluating the stress concentration factor of the human eye.  

PubMed

Healthy eyes are vital for a better quality of human life. Historically, for man-made materials, scientists and engineers use stress concentration factors to characterise the effects of structural non-homogeneities on their mechanical strength. However, such information is scarce for the human eye. Here we present the shear stress distribution profiles of a healthy human cornea surface in vivo using photo-stress analysis tomography, which is a non-intrusive and non-X-ray based method. The corneal birefringent retardation measured here is comparable to that of previous studies. Using this, we derive eye stress concentration factors and the directional alignment of major principal stress on the surface of the cornea. Similar to thermometers being used for monitoring the general health in humans, this report provides a foundation to characterise the shear stress carrying capacity of the cornea, and a potential bench mark for validating theoretical modelling of stresses in the human eye in future. PMID:25754336

Joseph Antony, S

2015-01-01

195

Imaging the proton concentration and mapping the spatial distribution of the electric field of catalytic micropumps  

E-print Network

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 chemo-mechanical actuation of catalytic pumps. Our experimental approach could be used to study other electrochemical systems with heteroge...

Farniya, A Afshar; Reguera, D; Bachtold, A

2013-01-01

196

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

197

Imaging the proton concentration and mapping the spatial distribution of the electric field of catalytic micropumps.  

PubMed

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. PMID:24182306

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

2013-10-18

198

Imaging shear stress distribution and evaluating the stress concentration factor of the human eye  

NASA Astrophysics Data System (ADS)

Healthy eyes are vital for a better quality of human life. Historically, for man-made materials, scientists and engineers use stress concentration factors to characterise the effects of structural non-homogeneities on their mechanical strength. However, such information is scarce for the human eye. Here we present the shear stress distribution profiles of a healthy human cornea surface in vivo using photo-stress analysis tomography, which is a non-intrusive and non-X-ray based method. The corneal birefringent retardation measured here is comparable to that of previous studies. Using this, we derive eye stress concentration factors and the directional alignment of major principal stress on the surface of the cornea. Similar to thermometers being used for monitoring the general health in humans, this report provides a foundation to characterise the shear stress carrying capacity of the cornea, and a potential bench mark for validating theoretical modelling of stresses in the human eye in future.

Joseph Antony, S.

2015-03-01

199

The concentration and distribution of organochlorine pesticides in the air from the karst cave, South China.  

PubMed

Organochlorine pesticides (OCPs) in the air of Dayan Cave in Guilin were analyzed, to investigate the source and contamination levels. Generally, air outside of the cave had much higher concentrations than inside air, and both outside and inside air showed much lower contamination levels than those observed in other regions in China and abroad. The ratios of ?-/?-HCHs and the percentages of ?-(or ?-)HCH implied a residue of historical local technical HCH contamination. The DDT concentrations, o,p'-DDT/p,p'-DDT, and p,p'-DDE/p,p'-DDT suggested fresh DDT-containing products acted as the primary source of DDT for the air in Dayan Cave. An intermediate level concentration of ?-endosulfan (156.00 pg/m(3)) was observed in the outside air, implying local source was dominant. Based on the similar sources of HCH and DDT and the relationships between outside and inside air, it appeared that outside air pollutants affected on inside HCH and DDT's distribution. For other OCPs, outside air might be major contributor to inside air contamination under conditions of high concentrations in outside air compared with low levels in inside air for semi-closed karstic caves. PMID:22161154

Wang, Yinghui; Guo, Songjun; Xu, Yiyin; Wang, Weisheng; Qi, Shihua; Xing, Xinli; Yuan, Daoxian

2012-08-01

200

Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column  

SciTech Connect

The use of optical fibers in a fluorescence-detection scheme permits the accurate determination of the radial distribution of the transit time, the column efficiency, and the analyte concentration at the exit of a chromatographic axial-compression column (50 mmID). The results obtained demonstrate that the column is not homogeneous, but suggest a nearly cylindrical distribution of the packing density. The average velocity close to the column wall is 7% lower than along its axis and the HETP 25% higher. The lack of homogeneity of the column packing is another source of band broadening not taken into account in chromatography so far. It causes the apparent HETP derived from the conventional elution chromatogram recorded on the bulk eluent to be larger than the local HETP and the band profile to be unsymmetrical with a slight tail reminiscent of kinetic tailing.

Farkas, T.; Sepaniak, M.J.; Guiochon, G. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry] [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; [Oak Ridge National Lab., TN (United States). Div. of Chemical and Analytical Sciences

1997-08-01

201

Microwave sintering of boron carbide  

DOEpatents

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.

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

1988-06-10

202

Estimation of the wild-type minimum inhibitory concentration value distribution.  

PubMed

Antimicrobial resistance has become one of the main public health burdens of the last decades, and monitoring the development and spread of non-wild-type isolates has therefore gained increased interest. Monitoring is performed based on the minimum inhibitory concentration (MIC) values, which are collected through the application of dilution experiments. In order to account for the unobserved population heterogeneity of wild-type and non-wild-type isolates, mixture models are extremely useful. Instead of estimating the entire mixture globally, it was our major aim to provide an estimate for the wild-type first component only. The characteristics of this first component are not expected to change over time, once the wild-type population has been confidently identified for a given antimicrobial. With this purpose, we developed a new method based on the multinomial distribution, and we carry out a simulation study to study the properties of the new estimator. Because the new approach fits within the likelihood framework, we can compare distinct distributional assumptions in order to determine the most suitable distribution for the wild-type population. We determine the optimal parameters based on the AIC criterion, and attention is also paid to the model-averaged approach using the Akaike weights. The latter is thought to be very suitable to derive specific characteristics of the wild-type distribution and to determine limits for the wild-type MIC range. In this way, the new method provides an elegant means to compare distinct distributional assumptions and to quantify the wild-type MIC distribution of specific antibiotic-bacterium combinations. PMID:23946200

Jaspers, Stijn; Aerts, Marc; Verbeke, Geert; Beloeil, Pierre-Alexandre

2014-01-30

203

Local impedance imaging of boron-doped polycrystalline diamond thin films  

NASA Astrophysics Data System (ADS)

Local impedance imaging (LII) was used to visualise surficial deviations of AC impedances in polycrystalline boron-doped diamond (BDD). The BDD thin film electrodes were deposited onto the highly doped silicon substrates via microwave plasma-enhanced CVD. The studied boron dopant concentrations, controlled by the [B]/[C] ratio in plasma, ranged from 1 × 1016 to 2 × 1021 atoms cm-3. The BDD films displayed microcrystalline structure, while the average size of crystallites decreased from 1 to 0.7 ?m with increasing [B]/[C] ratios. The application of LII enabled a direct and high-resolution investigation of local distribution of impedance characteristics within the individual grains of BDD. Such an approach resulted in greater understanding of the microstructural control of properties at the grain level. We propose that the obtained surficial variation of impedance is correlated to the areas of high conductance which have been observed at the grain boundaries by using LII. We also postulate that the origin of high conductivity is due to either preferential boron accumulation, the presence of defects, or sp2 regions in the intragrain regions. The impedance modulus recorded by LII was in full agreement with the bulk impedance measurements. Both variables showed a decreasing trend with increasing [B]/[C] ratios, which is consistent with higher boron incorporation into BDD film.

Zieli?ski, A.; Bogdanowicz, R.; Ryl, J.; Burczyk, L.; Darowicki, K.

2014-09-01

204

Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.  

PubMed

Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure. PMID:18585727

Musashi, Masaaki; Oi, Takao; Matsuo, Motoyuki; Nomura, Masao

2008-08-01

205

Preparation and characterization of superhard boron-suboxide films  

NASA Astrophysics Data System (ADS)

Boron-suboxide films with hardness reaching 44 GPa, the highest record ever achieved, were synthesized. The films with such high hardness had an oxygen/boron atomic concentration ratio of 0.05 and a carbon concentration of about 20 at. %. They were deposited on silicon at 750 °C by simple sputtering. In the range of oxygen/boron ratio varying from 0.06 to 0.3, the film hardness and elastic modulus decreased monotonically. Unlike other hard film formation, argon ion bombardment of the film during film growth reduced the film hardness.

Huang, H.; Ong, C. W.; Zheng, B.; Kwok, R. W. M.; Lau, W. M.; He, J. W.

2003-09-01

206

Drinking water health advisory for boron  

Microsoft Academic Search

The Health Advisory Program, sponsored by the Environmental Protection Agency's Office of Water, has issued its report on the element boron: included are the compounds boric acid and borax(sodium tetraborate). It provides information on the health effects, analytical methodology, and treatment technology that would be useful in dealing with the contamination of drinking water. Health Advisories (HAs) describe nonregulatory concentrations

Cantilli

1991-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

208

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.

209

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

USGS Publications Warehouse

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

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

1973-01-01

210

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

211

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

PubMed Central

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

Grossman, Judah D; Rice, Kevin J

2012-01-01

212

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

PubMed Central

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

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

2012-01-01

213

Boron Enrichment in Martian Clay  

PubMed Central

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

Nagashima, Kazuhide; Freeland, Stephen J.

2013-01-01

214

Boron enrichment in martian clay.  

PubMed

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

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

2013-01-01

215

Spatial distribution patterns of molybdenum (Mo) concentrations in potable groundwater in Northern Jordan.  

PubMed

Two hundred and three groundwater samples were collected during March 2011 to June 2012 from the B2/A7 aquifer water supply wells of northern part of Jordan. The physicochemical properties were analyzed in situ for the major cations, anions, while certain heavy metals were analyzed in the laboratory. Some oilshale rock samples were geochemically analyzed. The Upper Cretaceous aquifer (B2/A7) is used as water supply for most of the communities in the study area. It consists of limestone, marly limestone, bedded chert, and minor phosphorite. Hydrochemical results from the B2/A7 aquifer indicate two main water types: alkaline-earth water (CaHCO3) and alkaline-earth water with high alkaline component (NaHCO3 (-), Na2SO4). Standard column leaching experiments on oilshale rock samples and the R-mode factor analysis suggest that the sources for elevated Mo concentrations in the groundwater of certain parts of northern Jordan are attributed to water-oilshale interaction, mobility of Mo down to the groundwater and the extensive use of fertilizers within these areas. Molybdenum (Mo) concentrations in the groundwater water range from 0.07 to 1.44 mg/L with an average value of 98 ?g/L. They are found to exceed the JISM and WHO guidelines in two areas in northern part of Jordan. Spatial distribution of Mo, using ordinary kriging techniques and the resulting map, shows high Mo concentration in the northwestern part near Wadi Al Arab area reaching concentrations of 650 ?g/L and in the southeastern corner of the investigated area, south of Al Ukaydir village, with an average concentration of 468 ?g/L. Both areas are characterized by extensive oilshale exposures with average concentration of 11.7 mg/kg Mo and intensive agricultural activities. These two areas represent approximately 33 % of the groundwater in the northern part of Jordan. Mobility of Mo to the groundwater in northern part of Jordan is attributed to two mechanisms. First, there is reductive dissolution of Fe-oxide, which releases substantial adsorbed Mo concentrations. Secondly, there is oxidation of Mo into dissolved forms in sulfide organic-rich system. PMID:25720968

Al Kuisi, Mustafa; Al-Hwaiti, Mohammad; Mashal, Kholoud; Abed, Abdulkader M

2015-03-01

216

Synthesis, characterization and oxidation of boron-doped carbons  

NASA Astrophysics Data System (ADS)

The goal of this study was to gain a fundamental understanding of the role of boron in carbon oxidation. Boron-doped carbons were synthesized via CVD, ion implantation and high temperature doping and subsequently characterized. It was found that high temperature doped HOPG carbons were ideal for oxidation studies because their surface could be reproduced, their surface structures were determined and they were able to be characterized by XPS, AFM and SEM. The direct analysis of the chemical structures and atomic arrangements in boron-doped carbon or carbon surfaces by these techniques was critical in determining the effect of boron on carbon oxidation. XPS was utilized in this work to determine the local bonding environment of boron in carbon before and after oxidation. It was necessary to obtain an accurate calibration of the B1s binding energy scale which was accomplished by obtaining photoemission spectra of boron-doped carbons with known structures (local boron bonding environments), such as boron oxide, boron carbide, triphenylboroxine, tourmaline, boric acid, danburite and high temperature boron-doped graphite. All of the aforementioned standards contain boron in a unique bonding environment and thus their spectra formulated a complete conversion of B1s binding energies to boron chemical environments which had not been reported in the past. It was clearly established that a chemical shift for substitutional boron in graphite exists at 186.5 eV with a FWHM of 1.2. The chemical structures of the boron in the standards were related to the binding energy using a Pauling charge distribution model and a modification of the Sanderson electronegativity method. This approach was used to determine whether the B1s binding energy would change depending upon the specific location of boron in the graphite or graphite surface. This model was used, along with XPS, TEM and Raman results, to show that edge sites are preferred lattice sites in graphite for boron substitution. The oxidation behaviors of the synthesized high temperature doped samples were studied with TGA, SEM, XPS and AFM. It was found that boron caused the gasification rates of the carbons to decrease. The SEM and AFM results showed that the pits that were formed in the undoped and doped carbons were different in size, depth and orientation. A semi-empirical Molecular Orbital Package method and experimental results were used to show that the reactivity of the zig-zag edge sites of a pit wall could be reduced by the replacement of carbon atoms with boron atoms at these sites; hence, the oxidation would be inhibited in the a-direction of a graphene layer. Conversely, boron doping on an armchair edge surface of a pit wall results in increased reactivity at these sites and the subsequent formation of boron oxide during oxidation, which does not prevent oxidation in the a-direction of a graphene layer. Rather, the build-up of boron oxide clusters prevented oxidation in the c-direction. A model was proposed for the oxidation inhibition mechanism in boron-doped graphite based upon the stability of pits with boron substitution on the zig-zag sites.

Cermignani, William

217

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

218

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) PMID:7889870

Moseman, R F

1994-01-01

219

Global measurements of aerosols in remote continental and marine regions: concentrations, size distributions, and optical properties  

SciTech Connect

The phase I GAMETAG (global atmospheric measurements experiment of tropospheric aerosols and gases) aerosol measurements were to provide an initial assessment of the levels, types, and optical effects of tropospheric aerosols in remote marine and continental regions and examine the possible causal relationships between the observed distributions and the dominant factors controlling aerosol population. The aerosol population consists primarily of crustal aerosols with r less than or equal to 0.5 micrometer and sulfate and combustion aerosols with r < 0.5 micrometer, with only a minor sea salt component. Owing to vertical mixing, there are no qualitative differences between the boundary layer and the free troposphere. Our data indicate that crustal aerosols represent a significant component of a background tropospheric aerosol in western North America. Pacific marine measurements show a qualitative difference between the boundary layer and the free troposphere. The boundary-layer aerosol population is dominated by a bimodal sea spray aerosol; optical effects and mass concentration are dominated by a mode with a volume mean radius of approx 1 micrometer. Our measurements show only a small crustal component of the marine boundary-layer aerosol. We have inferred a background concentration of 0.2 ppBM for our measured particles that does not appear to be directly related to the sea spray aerosol. We have identified some of these particles as locally produced secondary aerosols; simultaneous measurements of gaseous species support this interpretation. Our Pacific free tropospheric aerosol measurements show a highly variable aerosol component, with local variations in concentration by 1 order of magnitude within a few kilometers. Our measured total aerosol and crustal component concentrations show a general decrease from north to south.

Patterson, E.M.; Kiang, C.S.; Delany, A.C.; Wartburg, A.F.; Leslie, A.C.D.; Hubert, B.J.

1980-01-01

220

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

221

NMR Study of Heavily Doped SILICON:BORON  

NASA Astrophysics Data System (ADS)

Pulsed nuclear magnetic resonance (NMR) has been used to study the hyperfine interactions in powdered Si:B. Samples from a variety of sources were examined to confirm the generality of our results. Room temperature carrier concentrations varied from about 3.4 times 10 ^{18} to 5.1 times 10^{19} cm ^{-3}. NMR measurements were carried out on the nuclei B^{11} and Si^{29} over a temperature range from 93 K to 463 K and an applied field strength of 8.0 T and 5.5 T. The B^{11} NMR frequency shift exhibits a Curie-like temperature dependence. A strong concentration dependence to the shift was observed. Lower concentration samples showed a more rapid rise in frequency than higher concentration samples as the temperature was lowered. Shift measurements on the highest concentration sample showed a linear dependence on applied field at lower temperatures. The Si^{29} NMR frequency showed relatively no shift over the same temperature range. B^{11} NMR in cubic NaBH_4 also showed no shift, thus ruling out the probe as a source of the shift. Both the B^{11} and Si^{29} line widths increase with decreasing temperature. We attribute all of the Si^{29} temperature dependence to a distribution of paramagnetic moments localized on a small fraction of the boron sites. Part of the B ^{11} line width temperature dependence is due a similar mechanism; other parts remain unexplained. The Si^{29}^in -lattice relaxation is due to interaction with itinerant carriers and shows a Korringa enhancement ranging from 7 to 10, possibly due to disorder. The B^ {11}^in-lattice relaxation rate is not linear in temperature in the two lower concentration samples, and is presumably associated with paramagnetic fluctuations localized on the boron sites. Relaxation in the highest concentration sample is due to interaction with itinerant carriers. We suggest that the source of the paramagnetism is transitory local moments which form on every boron site with a lifetime, tau_{rm loc}, such that T_1{rm (elec)} prec tau_{rm loc} prec 1/(2Deltaomega_ {rm sep}). T_1{ rm (elec)} is the electron spin-lattice relaxation time and Deltaomega_ {rm sep} is the separation in angular frequency space between the resonance frequency of the B^0 (paramagnetic) and the B ^{-}(diamagnetic) states. The observed shift is caused by a weighted average of the local magnetic fields at the B^0 and B ^{-} sites.

Fuller, Scott Edward

222

Multilayer graded boron carbide-aluminum composites  

NASA Astrophysics Data System (ADS)

Boron carbide aluminum composites with multi-layer microstructure were developed by molten aluminum infiltration of boron carbide preforms. A centrifugal casting process was employed to obtain preforms with multiple graded layer structure, where particles were distributed gradually from fine particles on one side to coarse particles on the other side within each layer. A tape casting process was also developed. Uniform or stepwise multiple gradient layer structures were obtained by stacking like tapes or different tapes in repeated patterns. A narrow range of preform densities was obtained by varying the densification conditions according to green forms. It has been previously reported that boron carbide and aluminum can form many different reaction products and contact angles between boron carbide and aluminum vary with temperature and time. Minimizing the reaction products might lead to better performance of composites. This study found that spontaneous infiltration can be achieved in minutes under rough vacuum (<100 muTorr) at 1200°C or higher. The amounts of reaction products could be effectively suppressed by rapid spontaneous infiltration. A low-temperature infiltration (LTI) scheme was designed and full infiltration of boron carbide by aluminum at T < 1000°C was achieved. Reaction products obtained by LTI were significantly less then that in composites obtained by spontaneous infiltration. The microstructure and mechanical properties of the resulting layered composites were evaluated and correlated to microstructure.

Zhang, Fuhong

223

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

224

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

225

Boron removal by electrocoagulation and recovery.  

PubMed

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

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

2014-03-15

226

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

227

Temporal and spatial PM10 concentration distribution using an inverse distance weighted method in Klang Valley, Malaysia  

NASA Astrophysics Data System (ADS)

PM10 is one of the air contaminants that can be harmful to human health. Meteorological factors and changes of monsoon season may affect the distribution of these particles. The objective of this study is to determine the temporal and spatial particulate matter (PM10) concentration distribution in Klang Valley, Malaysia by using the Inverse Distance Weighted (IDW) method at different monsoon season and meteorological conditions. PM10 and meteorological data were obtained from the Malaysian Department of Environment (DOE). Particles distribution data were added to the geographic database on a seasonal basis. Temporal and spatial patterns of PM10 concentration distribution were determined by using ArcGIS 9.3. The higher PM10 concentrations are observed during Southwest monsoon season. The values are lower during the Northeast monsoon season. Different monsoon seasons show different meteorological conditions that effect PM10 distribution.

Tarmizi, S. N. M.; Asmat, A.; Sumari, S. M.

2014-02-01

228

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

229

Boron and Plants  

Microsoft Academic Search

\\u000a Boron is found naturally in the earth’s crust in the oxidized form as borax and colemanite, particularly in the oceans, sedimentary\\u000a rocks, coal, shale, and some soils. It is never found in the elemental form in nature possessing a complex chemistry similar\\u000a to that of silicon, with properties switching between metals and non-metals. Boron has become an important and strategic

Munir Ozturk; Serdal Sakcali; Salih Gucel; Huseyin Tombuloglu

230

Processing of boron carbide  

Microsoft Academic Search

The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although

Namtae Cho

2006-01-01

231

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

232

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

233

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

SciTech Connect

Most studies of the geographic distribution of indoor radon levels are plotted by county or ZIP code. This method is used for the radon potential maps produced by the U.S. Environmental Protection Agency (EPA) and the New York State Department of Health (NYSDOH). The basis for the mapping is the mean or median indoor radon count for all the data provided by NYSDOH within each geographic area. While testing the indoor radon analyses provided to the authors by CMT Independent Laboratories, we discovered data that deviated markedly from the EPA and NYSDOH means for the Capital District of New York (Albany and surrounding counties). Their screening indoor radon average concentrations in pCi/L, indicate low potential for Schenectady (3.0), Saratoga (3.2), and Albany (3.7) counties; and moderate potential for Rensselaer (6.4) and Columbia (7.0) counties. Our database of over 3,000 analyses contains over 800 records of indoor radon counts above 4 pCi/L (14-47% of each county`s analyses), many high enough to be rated as a serious health hazard. In order to obtain greater precision of information, the authors plotted their indoor radon data by street address using MapInfo, a geographic Information System (GIS), and StreetInfo, MapInfo`s TIGER address database. We compared the geographic distribution of our data to both the Bedrock Geology and Surficial Geology Maps of New York State. The results show a striking relationship of radon concentrations to bedrock, faults and permeability of surficial material. Data being compiled and mapped by street address by the NYSDOH in Erie County in western New York, confirm our results.

Thomas, J.J. [Skidmore College, Saratoga Springs, NY (United States); Overeynder, H.M. [C.E.S., Gabon (Central African Republic); Thomas, B.R. [CMT Independent Laboratories, Clifton Park, NY (United States)

1995-09-01

234

Elemental concentrations and their size distributions of Beijing aerosol in January  

NASA Astrophysics Data System (ADS)

Aerosol sampling was carried out at a city centre site and a suburb site in Beijing in January 1983. PIXE (Proton Induced X-ray Emission) compatible cascade impactors were employed. The samples were analysed for 20 elements by PIXE in Fudan University. It has been found that most of the elements have bi-mode size distributions with a gradual progression from mainly coarse mode Ca, Ti and Al to mainly fine mode Zn, As and Pb. Elements Cl, K, S and Si show most obvious bi-mode, of which Si and S are particularly interesting. The concentrations of coarse mode aerosol in the city centre are about 1.4 times as large as that in the suburb for most of the elements, while the concentrations of fine mode aerosol in the city centre differ greatly from that in the suburb and vary significantly among elements, indicating some industrial sources. The enrichment factors of elements indicate that the coal smoke has a large-scale influence in North China.

Wang, Mingxing; Ren, Lixin; Lü, Weixiu; Chen, Jianxin; Zeng, Xianzhou; Che, Jianmei

1986-06-01

235

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

USGS Publications Warehouse

Fifty coal samples (28 anthracite and 22 lignites) were collected from both main and small coal mines in DPR Korea prioritized by resource distribution and coal production. The concentrations of 61 elements in 50 coal samples were determined by several multielement and element-specific techniques, including inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS), ion chromatogram (IC), cold-vapor atomic absorption spectrometry (CV-AAS), and hydride generation atomic absorption spectrometry (HGAAS). The ranges, arithmetic means and geometric means of concentrations of these elements are presented. A comparison with crustal abundances (Clarke values) shows that some potentially hazardous elements in the coals of DPR Korea are highly enriched Li, B, S, Cl, Zn, As, Se, Cd, Sn, Sb, W, Te, Hg, Ag, Pb, and La, Ce, Dy, Tm, Ge, Mo, Cs, Tl, Bi, Th and U are moderately enriched. A comparison of ranges and means of elemental concentrations in DPR Korea, Chinese, and world coals shows the ranges of most elements in DPR Korea coals are very close to the ranges of world coals. Arithmetic means of most elements in DPR Korea coals are close to that of American coals. Most elements arithmetic means are higher in Jurassic and Paleogene coals than coals of other ages. In DPR Korea coals, only seven elements in early Permian coals are higher than other periods: Li, Zn, Se, Cd, Hg, Pb, and Bi. Only five elements B, As, Sr, Mo, W in Neogene coals have arithmetic means higher than others. SiO2 and Al2O 3 in ashes are more than 70% except six samples. The correlation between ash yields and major elements from high to low is in the order of Si>Al>Ti>K>Mg>Fe>Na>Ca>P>S. Most elements have high positive correlation with ash (r>0.5) and show high inorganic affinity. ?? 2005 Elsevier Ltd. All rights reserved.

Hu, J.; Zheng, B.; Finkelman, R.B.; Wang, B.; Wang, M.; Li, S.; Wu, D.

2006-01-01

236

X-ray Microprobe Investigations of Elemental Distributions and Concentrations at Mineral-Microbe Interfaces  

NASA Astrophysics Data System (ADS)

Understanding the fate of heavy-metal contaminants in the environment is of fundamental importance in the development and evaluation of effective remediation and sequestration strategies. Bacteria and the extracellular material associated with them are thought to play a key role in determining a contaminant's speciation and thus its mobility in the environment. Additionally, the metabolism and surface properties of bacteria can be quite different depending upon whether the bacteria exhibit a planktonic (free-floating) or biofilm (surface adhered) habit. The microenvironment at and adjacent to actively metabolizing cells also can be significantly different from the bulk environment. Thus, to understand the microscopic physical, geological, chemical, and biological interfaces that determine a contaminant's macroscopic fate, the spatial distribution and chemical speciation of contaminants and elements that are key to biological processes must be characterized at micron and submicron lengthscales for bacteria in both planktonic and adhered states. Hard x-ray microimaging is a powerful technique for the element-specific investigation of complex environmental samples at the needed micron and submicron resolution. An important advantage of these techniques results from the large penetration depth of hard x-rays in water. This advantage minimizes the requirements for sample preparation and allows the detailed study of hydrated samples. The objectives of the studies to be presented are (1) to determine the spatial distribution, concentration, and chemical speciation of metals at, in, and near bacteria and bacteria-geosurface interfaces, (2) to use this information to identify the metabolic processes occurring within the microbes, and (3) to identify the interactions occurring near these interfaces among the metals, mineral surfaces, and bacteria under a variety of conditions. We have used x-ray fluorescence microscopy to investigate the spatial distribution of 3d elements in Pseudomonas fluorescens cells in both planktonic and surface-adhered states. We have used x-ray fluorescence spectromicroscopy to investigate the chemical speciation and distribution of Cr that was introduced to these cells as Cr(VI). Additionally, we have used these techniques to identify the distribution of an over expressed cytochrome c7 in individual E. coli. Finally, we have used x-ray fluorescence microscopy to investigate Shewanella oneidensis MR-1 cells adhered to iron oxyhydroxide thin films. The zone plate used in these microscopy experiments produced a focused beam with a cross section (and hence spatial resolution) of 100-300 nanometers. Results from x-ray fluorescence imaging experiments indicate that the distribution of P, S, Cl, Ca, Fe, Ni, Cu, and Zn can define the location of the microbe. Additionally, quantitative elemental analysis of individual microbes identified significant changes in concentration of 3d transition elements depending on the age of the culture and the type of electron acceptor presented to the microbes. These results and a discussion of the use of this technique for identifying metabolic states of individual microbes within communities and the chemical speciation of metal contaminants at the mineral-microbe interface will be presented.

Kemner, K. M.; Kelly, S. D.; O'Loughlin, E. J.; Lai, B.; Maser, J.; Cai, Z.; Londer, Y.; Schiffer, M.; Nealson, K.

2003-12-01

237

Evidence of the role of boron in undoped GaAs grown by liquid encapsulated Czochralski  

NASA Astrophysics Data System (ADS)

We provide experimental evidence of electrical activity correlated with residual boron impurities and native point defects in undoped liquid-encapsulated Czochralski GaAs crystals. In Ga-rich samples containing ?1017 cm-3 boron, an 0.073-eV acceptor level is observed in which the concentration increases with Ga and B content. An approximately quadratic increase in the concentration of the 0.073-eV defect acceptor is observed with increasing boron concentration, suggesting that a complex involving boron with an intrinsic defect (VAs, Gai, or GaAs ) is responsible for the observed acceptor behavior. No evidence of electrically active boron or boron complexes was found in semi-insulating GaAs pulled from stoichiometric or As-rich melts.

Ta, L. B.; Hobgood, H. M.; Thomas, R. N.

1982-12-01

238

Prey density, value, and spatial distribution affect the efficiency of area-concentrated search.  

PubMed

Searching individuals need to take decisions on where and how long to search. When food is spatially aggregated, detection of a food item signals a probability for the presence of further prey items in its surrounding. Organisms can thus intensify search effort upon detecting a prey item, but after unsuccessfully searching for a while, return to the previous, extensive search, this strategy is known as 'area-concentrated-search' (ACS). Here we present results of simulations where individuals perform ACS employing a correlated random walk with variable directional persistence. Switching between intensive and extensive search (with respectively low and high directional persistence) is a function of searcher's internal state represented as 'satiety' level depending on preceding consumption of prey items. We explore the effect of this function's control parameters ('switching level' i.e., the satiety at which the switching occurs, and the switchover shape parameter) on searching efficiency in dependence of (1) prey items' spatial distribution ranging from randomly uniform to highly contagious, (2) the overall prey density, and (3) prey 'caloric' value. Our main conclusions: (1) the form of the adopted switchover exerts an effect on searching efficiency, and this effect is most pronounced in landscapes with highly aggregated resources. Except for the most homogeneous prey distributions, there was a clear optimum area within the movement parameter space, yielding highest efficiency. (2) The optimal switching level is larger in heterogeneous landscapes, but optimum switchover shape is little affected by any of the landscape attributes. In most landscapes, it is most profitable to switch gradually rather than abruptly. (3) The success and optimal switching level depend not only on the prey's spatial distribution but also on average prey density while the value of prey items has little effect on the optimal movement parameters. PMID:22995820

Barto?, Kamil A; Hovestadt, Thomas

2013-01-01

239

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

240

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

241

Process for making boron nitride using sodium cyanide and boron  

DOEpatents

This a very simple process for making boron nitride by mixing sodium cyanide and boron phosphate and heating the mixture in an inert atmosphere until a reaction takes place. The product is a white powder of boron nitride that can be used in applications that require compounds that are stable at high temperatures and that exhibit high electrical resistance.

Bamberger, Carlos E. (Oak Ridge, TN)

1990-01-01

242

Ames positive boronic acids are not all eukaryotic genotoxins.  

PubMed

Boronic acids and their derivatives have been exploited for their pharmacological activity and their utility as intermediates in the synthesis of novel non-boron containing compounds. A recent study reported that boronic acids are bacterial mutagens. Here, results are reported from the testing of nine boronic acids using the pan-mechanistic eukaryotic GADD45a genotoxicity assays, BlueScreen HC and GreenScreen HC. Positive results were produced for one compound in GreenScreen and four compounds in BlueScreen. Only negative results were produced when tested with S9 metabolic activation. These data suggest that there is not a general genotoxic liability in eukaryotes, within this chemical domain. Furthermore, they are not potent eukaryotic genotoxins: positive results were produced only at concentrations between 1mM and 10mM. Their presence as low concentration contaminants or impurities would be unlikely to produce misleading positive results for a test material. PMID:25726177

Scott, Heather; Walmsley, Richard M

2015-01-01

243

Root Growth Inhibition in Boron-Deficient or Aluminum-Stressed Squash May Be a Result of Impaired Ascorbate Metabolism.  

PubMed Central

Although cessation of growth is the most apparent symptom of boron deficiency, the biochemical function of boron in growth processes is not well understood. We propose that the action of boron in root meristems is associated with ascorbate metabolism. Total inhibition of root growth in squash (Cucurbita pepo L.) plants transferred to boron-free medium coincided with a major decrease (up to 98%) in the ascorbate concentration of root apices. Under low-boron conditions, in which root growth was partially inhibited, ascorbate concentration declined in proportion to growth rate. The decline in ascorbate concentration in boron-deficient root tips was not related to ascorbate oxidation. Ascorbate added to the medium improved root growth in plants supplied with insufficient boron. Increasing concentrations of aluminum in the nutrient medium caused progressive inhibition of root growth and a parallel reduction in ascorbate concentration of root apices. Elevated boron levels improved root growth under toxic aluminum conditions and produced root apices with higher ascorbate concentrations. To our knowledge, this is the first report of a correlation between boron nutrition, ascorbate concentration in root apices, and growth. These findings show that root growth inhibition resulting from either boron deficiency or aluminum toxicity may be a consequence of disrupted ascorbate metabolism. PMID:12226437

Lukaszewski, K. M.; Blevins, D. G.

1996-01-01

244

Boronate-Mediated Biologic Delivery  

PubMed Central

Inefficient cellular delivery limits the landscape of macromolecular drugs. Boronic acids readily form boronate esters with the 1,2- and 1,3-diols of saccharides, such as those that coat the surface of mammalian cells. Here pendant boronic acids are shown to enhance the cytosolic delivery of a protein toxin. Thus, boronates are a non-cationic carrier that can deliver a polar macromolecule into mammalian cells. PMID:22303837

Ellis, Gregory A.; Palte, Michael J.; Raines, Ronald T.

2012-01-01

245

Effects of Boron and Salinity on Red Raspberry in Vitro  

Microsoft Academic Search

Raspberry (Rubus idaeus L.) explants were cultured in vitro under two boron concentrations (0.1 and 0.5 mM) and three levels of NaCl salinity (0, 5, and 10 mM) on an MS medium. The high boron and salt treatment (0.5 mM B and 10 mM NaCl) diminished mean shoot length and fresh and dry weights of the explants; however, fresh-to-dry weight

Damianos Neocleous; Miltiadis Vasilakakis

2008-01-01

246

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

247

Method for separating boron isotopes  

Microsoft Academic Search

A method of separating boron isotopes ¹°B and ¹¹B by laser-induced selective excitation and photodissociation of BClâ molecules containing a particular boron isotope is described. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BClâ, thus effecting the desired separation of the boron isotopes.

Rockwood

1978-01-01

248

Method for separating boron isotopes  

Microsoft Academic Search

A method of separating boron isotopes .sup.10 B and .sup.11 B by laser-induced selective excitation and photodissociation of BCl.sub.3 molecules containing a particular boron isotope. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BCl.sub.3, thus effecting the desired separation of the boron isotopes.

Rockwood; Stephen D

1978-01-01

249

Mineral of the month: boron  

USGS Publications Warehouse

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

Lyday, Phyllis A.

2005-01-01

250

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

251

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

252

Prediction of Late-Time Concentration Tailing Through Characterization of Hydrofacies Distributions  

NASA Astrophysics Data System (ADS)

Anomalous (non-Fickian) diffusion is often manifested in extra mass in the late-time tail of the breakthrough curve (BTC). Current non-local techniques, including the multi-rate mass transfer method (MRMT) and the continuous time random walk (CTRW) method, are a posteriori fitting procedures that assign an appropriate memory function or a transition time distribution function to account for the trapping of solute particles in relatively immobile domains. The MRMT and CTRW are functionally equivalent, but the MRMT method allows a straightforward, a priori construction of the memory function based on readily available information about the statistics of the immobile zone geometry. We explore the quantitative relationship between the memory function and aquitard material heterogeneity using Monte Carlo simulations of the regional-scale alluvial aquifer system at the Lawrence Livermore National Laboratory site. Particle tracking simulations show that the shape of the late-time BTC depends on the thickness and the associated volume fractions of immobile water in "blocks" of fine-grained material. The ensemble solute concentration at later time can be very accurately predicted using a small number of exponential functions with rates dictated by aquitard thicknesses. Specifically, if the volume fraction of immobile layer thicknesses has a power-law probability distribution function (pdf), then a power-law BTC late tail will be guaranteed. When the volume fraction of immobile blocks has an exponential pdf, the late-time BTC will have a transition from power-law to exponential decay. The MRMT solutions are easily generated and accurately predict the later BTC tails. Since the residence time dictated by diffusive motion in the silt and clay layers embedded in typical natural media far exceeds the residence time in a laboratory column, we anticipate that upscaling from lab studies is irrelevant in most cases. The observed relationship between the BTC late tail and the aquitard property implies that 1) it is possible to build the memory function given information of the distribution of fine-grained units, and 2) we may predict the general behavior of late-time, non-Fickian MRMT or CTRW transport by gleaning information from boring logs or outcrops.

Zhang, Y.; Benson, D. A.

2006-12-01

253

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

254

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

SciTech Connect

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

D.W. Nigg; Various Others

2014-06-01

255

Distribution, origin and contamination risk of coagulase-negative staphylococci from platelet concentrates.  

PubMed

Transfusion-associated bacterial sepsis is the most common microbiological risk of transfusion and is caused mostly by platelet concentrates (PCs). The most frequently identified bacterial contaminants of PCs are coagulase-negative staphylococci (CNS). In order to learn more about the distribution, source and risk of the CNS that are involved in bacterial contamination of PCs, CNS strains isolated during platelet screening were collected and characterized to the species level with three different methods: 16S rRNA and sodA gene sequencing, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and amplified fragment length polymorphism (AFLP) analysis. AFLP analysis was also used for the typing of the CNS strains. A total of 83 CNS strains were analysed by sequencing and 8 different CNS species were identified, with Staphylococcus epidermidis being the predominant species. MALDI-TOF MS and AFLP analysis confirmed these results to a large extent. However, MALDI_TOF MS could not identify all strains to the species level and AFLP analysis revealed an additional, likely novel, CNS species. The species identified are mainly recognized as being part of the normal skin flora. Typing of the CNS strains by AFLP analysis showed that there was not a unique strain which is significantly more often present during bacterial contamination of PCs. PMID:21212143

Rood, Ineke G H; de Korte, Dirk; Ramírez-Arcos, Sandra; Savelkoul, Paul H M; Pettersson, Annika

2011-05-01

256

An efficient numerical method for distributed-loop models of the urine concentrating mechanism.  

PubMed

In this study we describe an efficient numerical method, based on the semi-Lagrangian (SL) semi-implicit (SI) method and Newton's method, for obtaining steady-state (SS) solutions of equations arising in distributed-loop models of the urine concentrating mechanism. Dynamic formulations of these models contain large systems of coupled hyperbolic partial differential equations (PDEs). The SL method advances the solutions of these PDEs in time by integrating backward along flow trajectories, thus allowing large time steps while maintaining stability. The SI approach controls stiffness arising from transtubular transport terms by averaging these terms in time along flow trajectories. An approximate SS solution of a dynamic formulation obtained via the SLSI method can be used as an initial guess for a Newton-type solver, which rapidly converges to a highly accurate numerical approximation to the solution of the ordinary differential equations that arise in the corresponding SS model formulation. In general, it is difficult to specify a priori for a Newton-type solver an initial guess that falls within the radius of convergence; however, the initial guess generated by solving the dynamic formulation via the SLSI method can be made sufficiently close to the SS solution to avoid numerical instability. The combination of the SLSI method and the Newton-type solver generates stable and accurate solutions with substantially reduced computation times, when compared to previously applied dynamic methods. PMID:12445757

Layton, Anita T; Layton, Harold E

2003-02-01

257

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

PubMed Central

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

Blevins, D G; Lukaszewski, K M

1994-01-01

258

Phase-Field Simulation of Concentration and Temperature Distribution During Dendritic Growth in a Forced Liquid Metal Flow  

NASA Astrophysics Data System (ADS)

A phase-field model with convection is employed to investigate the effect of liquid flow on the dendritic structure formation of a Ni-Cu alloy during rapid solidification. Temperature and solute diffusion are significantly changed with induced liquid metal flow, and distribution changes of concentration and temperature are also analyzed and discussed. The solute segregation is affected due to the concentration diffusion layer thickness change caused by the liquid flow. The flow reduces the solute segregation in the upstream and leads to a fast dendrite growing, while solidifying in the downstream gets constrained with the large solute diffusion layer. Increasing flow velocity increases the asymmetry of dendrite morphology with much more suppressed growth in the downstream. The temperature distribution is also asymmetrical due to the non-uniform latent heat released during solidification coupling with heat diffusion changed by the liquid flow. Therefore, the forced liquid flow significantly affects the dendrite morphology, concentration, and temperature distributions in the solidifying microstructure.

Du, Lifei; Zhang, Rong

2014-12-01

259

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

260

Boron-carbide-aluminum and boron-carbide-reactive metal cermets  

DOEpatents

Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.

Halverson, Danny C. (Manteca, CA); Pyzik, Aleksander J. (Seattle, WA); Aksay, Ilhan A. (Seattle, WA)

1986-01-01

261

Boron Requirement in Cyanobacteria 1  

PubMed Central

The effect of boron on heterocystous and nonheterocystous dinitrogen fixing Cyanobacteria was examined. The absence of boron in culture media inhibited growth and nitrogenase activity in Nodularia sp., Chlorogloeopsis sp., and Nostoc sp. cultures. Examinations of boron-deficient cultures showed changes in heterocyst morphology. However, cultures of nonheterocystous Cyanobacteria, Gloeothece sp. and Plectonema sp., grown in the absence of boron did not show any alteration in growth or nitrogenase activity. These results suggest a requirement of boron only by heterocystous Cyanobacteria. A possible role for this element in the early evolution of photosynthetic organisms is proposed. Images Figure 4 Figure 5 Figure 6 PMID:16667889

Bonilla, Ildefonso; Garcia-González, Mercedes; Mateo, Pilar

1990-01-01

262

Boron hydride polymer coated substrates  

DOEpatents

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

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

1986-08-27

263

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

264

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

265

Boron and silicon: Effects on growth, plasma lipids, urinary cyclic AMP and bone and brain mineral composition of male rats  

SciTech Connect

Because boron resembles silicon in its chemical properties, an experiment was performed to determine if excessive dietary boron would affect the response to silicon deprivation and, conversely, if silicon would influence the effects of an excessive intake of boron. Male weanling Sprague-Dawley rats were assigned to groups of 6 or 12 in a two-by-two factorially arranged experiment. Supplemented to a ground corn/casein diet containing 1.2 [mu]g silicon and 3 [mu]g boron per gram were silicon as sodium metasilicate at 0 or 50 [mu]g/g and boron as orthoboric acid at 0 or 500 [mu]g/g diet. At nine weeks, animals fed high dietary boron had significantly decreased final body weights, liver-weight-to-body-weight ratios, urinary cAMP concentrations, plasma triglyceride, cholesterol, glycine, valine, leucine, and lysine concentrations and skull copper, sodium, and manganese concentrations. High dietary boron also significantly increased brain-weight-to-body-weight ratios, magnesium concentrations of femur, brain, and plasma, zinc concentration of femur, and iron concentration of skull. The bone mineral findings suggest that excess dietary boron exerts subtle effects on bone composition. Dietary silicon affected blood urea nitrogen, hematocrit, hemoglobin, and the concentrations of plasma threonine and aspartic acid in animals fed excess boron. Depression of the testes-weight-to-body-weight ratio of animals fed 500 [mu]g boron per gram diet was most marked in animals not fed silicon. Although excessive dietary boron did not markedly enhanced the response of rats to silicon deprivation, dietary silicon affected their response to high dietary boron. Thus, dietary silicon apparently can influence boron toxicity.

Seaborn, C.D.; Nielsen, F.H. (Dept. of Agriculture, Grand Forks, ND (United States). Grand Forks Human Nutrition Research Center)

1994-06-01

266

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

PubMed

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

Nanzetta, M Katherine; Holmén, Britt A

2004-05-01

267

Determination of phase stability of elemental boron.  

PubMed

Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (? or ?) is stable at ambient conditions. Through experiment, we quantify the relative stability of ?-boron and ?-boron as a function of temperature. The ground-state energies of ?-boron and ?-boron are nearly identical. For all temperatures up to 2000?K, the complicated ?-boron structure is more stable than the simpler ?-boron structure at ambient pressure. Below 1000?K, ?-boron is entropically stabilized with respect to ?-boron owing to its partially occupied sites, whereas at higher temperatures ?-boron is enthalpically stabilized with respect to ?-boron. We show that ?-boron only becomes stable on application of pressure. PMID:25619645

White, Mary Anne; Cerqueira, Anthony B; Whitman, Catherine A; Johnson, Michel B; Ogitsu, Tadashi

2015-03-16

268

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. PMID:7889885

Green, N R; Ferrando, A A

1994-01-01

269

The Spatial Distribution of Tropospheric Ozone Concentration Associated to Land Use in the Sao Paulo Metropolitan Area, Brazil  

NASA Astrophysics Data System (ADS)

Atmospheric Pollution presents a great challenge in the environmental and health management of the great urban centres, affecting all who reside in these locations. Presently, one of the most hazardous pollutants in the São Paulo Metropolitan Area (SPMA) is tropospheric ozone (O3). Its formation and control are influenced by a number of different factors, which involve precursor emission, atmospheric and environmental variables such as incoming shortwave solar radiation, and land use in the surroundings of the monitoring site (which alter atmospheric chemistry locally), creating a complex picture of temporal and spatial distribution of this pollutant in the study area. In addition to its complexity, O3 does not present a decreasing tendency through the years in the study area and its highest concentrations are measured in places often visited by the population, such as urban parks and squares, yet typical of having lower concentrations of vehicular pollution. In order to properly assess these issues, a better understanding of the processes related to the control of tropospheric ozone is required. Using data from the State Environmental Agency (CETESB), we intend to study the spatial distribution of tropospheric ozone in the SPMA. Previous works on the subject have shown that land use is an important factor in the control of O3 concentrations. From this understanding, we intend to look for associations between ozone concentrations and land use throughout the city, and also in specific locations, such as parks and squares, known for high ozone concentrations in the city. In order to assess the impact of land use change in the pollutant's concentration, the atmospheric model WRF/Chem will be used. This will be done by replacing, in the model, a typically urbanized area in the city by that of a park, and checking the impacts on ozone concentrations afterwards. Through sensitivity tests in the model, we also intend to work with other parametrizations that define the impact of urbanization in the concentration and spatial distribution of tropospheric ozone.

Chiquetto, Julio; Siqueira Silva, Maria Elisa

2013-04-01

270

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

PubMed Central

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

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

1995-01-01

271

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...

272

A measurement plan of gas concentration and temperature distribution reconstruction based on the tunable diode laser absorption tomography  

NASA Astrophysics Data System (ADS)

Based on the tunable diode laser absorption tomography, gas concentration and temperature two-dimensional distribution reconstruction is realized using algebraic iterative reconstruction technique (ART). A measurement plan is proposed based on the beam splitting lens, and the corresponding beam arrangement is put forward. The beam splitting lenses are used in the plan to making one laser beam cross the measurement area repeatedly. Thus can raise the utilization ratio of laser beam and simplify the structure of measurement platform. A model for H2O vapor concentration and temperature distribution is assumed, and numerical simulation is utilized using two absorption transitions. The feasibility of the measurement plan is proved by the simulation experiment. The influences of initial beam angle, the number of beams and grids on the reconstructed results are analyzed numerically. A concept of phantom description method using in simulation experiments is proposed in order to getting closer to the real experiments. The phantom description method is used in the numerical simulation to evaluating concentration and temperature field reconstruction. Through this method, expected data is sampled from initial data, and reconstructed result is obtained by interpolation. The influence of random errors in projections on distribution reconstruction is also analyzed. The measurement plan can reconstruct the gas concentration and temperature distribution with a simplified measurement platform using beam splitting lenses. The feasibility of the phantom description method is also proved by the simulation experiment.

Liu, Zhao-ran; Jin, Xing; Wang, Guang-yu; Song, Jun-ling

2014-11-01

273

The relationship of blood- and urine-boron to boron exposure in borax-workers and usefulness of urine-boron as an exposure marker.  

PubMed Central

Daily dietary-boron intake and on-the-job inspired boron were compared with blood- and urine-boron concentrations in workers engaged in packaging and shipping borax. Fourteen workers handling borax at jobs of low, medium, and high dust exposures were sampled throughout full shifts for 5 consecutive days each. Airborne borax concentrations ranged from means of 3.3 mg/m3 to 18 mg/m3, measured gravimetrically. End-of-shift mean blood-boron concentrations ranged from 0.11 to 0.26 microgram/g; end-of-shift mean urine concentrations ranged from 3.16 to 10.72 micrograms/mg creatinine. Creatinine measures were used to adjust for differences in urine-specific gravity such that 1 ml of urine contains approximately 1 mg creatinine. There was no progressive increase in end-of-shift blood- or urine-boron concentrations across the days of the week. Urine testing done at the end of the work shift gave a somewhat better estimate of borate exposure than did blood testing, was sampled more easily, and was analytically less difficult to perform. Personal air samplers of two types were used: one, the 37-mm closed-face, two-piece cassette to estimate total dust and the other, the Institute of Occupational Medicine (IOM) sampler to estimate inspirable particulate mass. Under the conditions of this study, the IOM air sampler more nearly estimated human exposure as measured by blood- and urine-boron levels than did the sampler that measured total dust.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7889874

Culver, B D; Shen, P T; Taylor, T H; Lee-Feldstein, A; Anton-Culver, H; Strong, P L

1994-01-01

274

The concentrations and distribution of mercury in aquatic ecosystem of Baihua Reservoir  

Microsoft Academic Search

Mercury species in water column, sediment and fish from the Hg-contaminated Baihua Reservoir were measured by trap pre-concentration\\u000a and CVAFS and CVAAS detection methods. The results showed that the highest average total Hg concentration is up to 73.36 ng\\/L\\u000a in the water column, 186.7 ng\\/L in pore water of surface sediment in the Baihua Reservoir. The total mercury concentrations\\u000a in

Haiyu Yan; Xinbin Feng; Hongmei Jiang; Guangle Qiu; Guanghui Li; Lihai Shang

2005-01-01

275

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

E-print Network

Advances in parabolic trough solar power technology. Journalthe concentrating solar power (CSP) troughs in the centraltrough coefficients are comparable to those for a dish collector). Direct normal solar

Norwood, Zachary Mills

2011-01-01

276

Boron suboxide: As hard as cubic boron nitride  

NASA Astrophysics Data System (ADS)

The Vickers hardness of boron suboxide single crystals was measured using a diamond indentation method. Under a loading force of 0.98 N, our test gave an average Vickers hardness of 45 GPa. The average fracture toughness was measured as 4.5 MPa m1/2. We also measured the hardness of the cubic boron nitride and sapphire single crystals for comparison. The average measured hardness for boron suboxide was found to be very close to that of cubic boron nitride under the same loading force. Our results suggest that the boron suboxide could be a new superhard material for industrial applications, surpassed in hardness only by diamond and cubic boron nitride.

He, Duanwei; Zhao, Yusheng; Daemen, L.; Qian, J.; Shen, T. D.; Zerda, T. W.

2002-07-01

277

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

PubMed Central

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

2015-01-01

278

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

PubMed Central

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

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

2013-01-01

279

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

280

Hard boron oxide thin-film deposition using electron cyclotron resonance microwave plasmas  

NASA Astrophysics Data System (ADS)

Hard boron suboxide thin films were deposited in an electron cyclotron resonance (ECR) microwave plasma system at substrate temperatures below 300 °C. A high-temperature effusion cell, operated at 2200°-2250 °C, was used for injection of boron downstream of an Ar/O2 ECR plasma. B ion bombardment is estimated to have been up to 6% of the total boron flux, and Ar ion bombardment is estimated to have contributed ˜100 eV/deposited atom. Boron suboxide films with oxygen concentrations of 11% exhibited hardnesses up to 30 GPa, equal to sapphire and near that of pure boron. The hardness/modulus ratio was 0.1, significantly better than that of sapphire (0.067) or solid boron (0.074), indicating these films may be of interest for a variety of tribological applications.

Gorbatkin, S. M.; Rhoades, R. L.; Tsui, T. Y.; Oliver, W. C.

1994-11-01

281

Hard boron oxide thin-film deposition using electron cyclotron resonance microwave plasmas  

SciTech Connect

Hard boron suboxide thin films were deposited in an electron cyclotron resonance (ECR) microwave plasma system at substrate temperatures below 300 [degree]C. A high-temperature effusion cell, operated at 2200[degree]--2250 [degree]C, was used for injection of boron downstream of an Ar/O[sub 2] ECR plasma. B ion bombardment is estimated to have been up to 6% of the total boron flux, and Ar ion bombardment is estimated to have contributed [similar to]100 eV/deposited atom. Boron suboxide films with oxygen concentrations of 11% exhibited hardnesses up to 30 GPa, equal to sapphire and near that of pure boron. The hardness/modulus ratio was 0.1, significantly better than that of sapphire (0.067) or solid boron (0.074), indicating these films may be of interest for a variety of tribological applications.

Gorbatkin, S.M.; Rhoades, R.L.; Tsui, T.Y.; Oliver, W.C. (Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831 (United States))

1994-11-21

282

Experimental Microbiology of Saturated Salt Solutions and Other Harsh Environments. III. Growth of Salt-Tolerant Penicillium notatum in Boron-Rich Media 1  

PubMed Central

A stress-tolerant strain of Penicillium notatum, isolated by passage through a nutrient solution saturated with calcium acetate, was found to have a tolerance to boron in several states of oxidation. Growth in the presence of elementary boron, saturating amounts of boric acid, and with various concentrations of sodium borohydride was observed and mycelial mats were spectrographically analyzed for boron accumulation. PMID:6076112

Roberts, Karen; Siegel, S. M.

1967-01-01

283

Numerical study on determining formation porosity using a boron capture gamma ray technique and MCNP.  

PubMed

Formation porosity can be determined using the boron capture gamma ray counting ratio with a near to far detector in a pulsed neutron-gamma element logging tool. The thermal neutron distribution, boron capture gamma spectroscopy and porosity response for formations with different water salinity and wellbore diameter characteristics were simulated using the Monte Carlo method. We found that a boron lining improves the signal-to-noise ratio and that the boron capture gamma ray counting ratio has a higher sensitivity for determining porosity than total capture gamma. PMID:25255304

Liu, Juntao; Zhang, Feng; Wang, Xinguang; Han, Fei; Yuan, Zhelong

2014-12-01

284

Continuous monitoring of residual chlorine concentrations in response to controlled microbial intrusions in a laboratory-scale distribution system.  

PubMed

The objective of this work was to evaluate the efficacy of deploying free chlorine sensors as surrogate monitors for bacterial contamination events in drinking water distribution systems. An on-line sensor integral with a laboratory-scale distribution system (LDS) was shown to respond rapidly to changes in residual free chlorine concentrations induced by injected loads of Escherichia coli suspended in a chlorine demand free buffer. The magnitude of the residual response was proportional to the injected cell concentration, the background free chlorine concentration in the LDS, and the contact time between the chlorine residual and the injected suspension, consistent with previous results in batch reactors. The magnitude of the residual response was predicted when kinetic models developed from reaction kinetics between free chlorine and E. coli determined in batch systems were evaluated at contact times determined from LDS hydraulics. This result highlights the suitability of using batch kinetics when modeling contaminant-induced chlorine decay in the distribution system. Modeling the propagation of chlorine demand signals generated by specific pathogens could aid in the assessment of distribution system vulnerability. PMID:18433828

Helbling, Damian E; Vanbriesen, Jeanne M

2008-06-01

285

Inelastic properties of boron oxides  

Microsoft Academic Search

Temperature dependence of internal friction and dynamic shear modulus for boron anhydride (B2O3) and boron suboxide (B6O) have been investigated at frequencies of 1–10 Hz and over the temperature range 80–900 K. Absolute shear modulus for boron suboxide at 80 and 400 K was 0.9 and 0.85 GPa, respectively. Relaxation maximum of internal friction, accompanied with shear modulus defect had

M. Ch. Tushishvili; G. Sh. Darsavelidze; O. A. Tsagareishvili; I. A. Bairamashvili; J. Sh. Jobava

1991-01-01

286

Inelastic properties of boron oxides  

Microsoft Academic Search

Temperature dependence of internal friction and dynamic shear modulus for boron anhydride (B2O3) and boron suboxide (B6O) have been investigated at frequencies of 1-10 Hz and over the temperature range 80-900 K. Absolute shear modulus for boron suboxide at 80 and 400 K was 0.9 and 0.85 GPa, respectively. Relaxation maximum of internal friction, accompanied with shear modulus defect had

M. Ch. Tushishvili; G. Sh. Darsavelidze; O. A. Tsagareishvili; I. A. Bairamashvili; J. Sh. Jobava

1991-01-01

287

Natural Radioactivity of Boron Added Clay Samples  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

288

Natural Radioactivity of Boron Added Clay Samples  

SciTech Connect

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

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

2011-12-26

289

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

E-print Network

water in the manufacture of a concentrating solar system,DCS-CHP) system. Background of solar-water nexus Dublinsystem, including both electricity and heat production, is expected to be 27 months. Water and solar

Norwood, Zachary Mills

2011-01-01

290

Distribution of arsenic concentrations in groundwater of the Seymour Aquifer, Texas, USA.  

PubMed

The purpose of this study was to investigate arsenic concentrations in the Seymour Aquifer. Discontinuous alluvium of the aquifer occupies a broad, semi-arid region of northern Texas, USA. Throughout the formation's outcrop, permeable deposits and unconfined conditions may facilitate downward travel of contaminants applied to the land surface. Past agricultural practices are a potential source of arsenic to the aquifer. However, of 64 water samples analyzed from 2001-2004, only one exceeded the maximum contaminant level (MCL) of 10 microg/l for arsenic in drinking water. The median arsenic concentration was 2.7 microg/l, and 34% of samples had arsenic concentrations less than 2 microg/l. No relationship between arsenic concentration and well depth was observed. PMID:18231948

Hudak, Paul F

2008-02-01

291

Concentrations and distribution of organochlorine pesticides in shellfish from Changjiang estuary  

NASA Astrophysics Data System (ADS)

To analyze and evaluate the status of organochlorine pollutants in the Changjiang (Yangtze River) estuary and adjacent waters, the concentrations of hexachlorocyclohexane (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in shellfish collected in study area from 2006 to 2007 were determined with gas chromatography (GC). The concentration range of HCHs was (ND-12.13)×10-3 mg/kg wet weight and averaged at 0.54×10-3 mg/kg while the concentration of DDTs was in the range of (4.06-281.73) ×10-3 mg/kg with a mean of 57.52×10-3 mg/kg in the survey areas. The concentrations of DDTs in the shellfish were higher than HCHs’, so that DDTs could be considered as typical organochlorine pollutants in the areas. The concentrations of DDTs in the shellfish were higher than HCHs’, so that DDTs could be considered as typical organochlorines pollutants. The HCHs in all the shellfish conformed to the first level of criterion (0.02 mg/kg) of the Marion Biology Quality (GB 18421-2001), and that of DDTs in most samples were beyond the first level (0.01 mg/kg) but conformed to the second level (0.10 mg/kg). On average, ?-HCH and ?-HCH occupied the most part of HCHs, while O,P’-DDT and P,P’-DDT occupied the most part of DDTs. The concentrations of organocholorine pesticides in shellfish samples varied in site and in species. The highest level occurred at the Shengsi (SS), followed by Yangkougang (YKG), Lvsi (LS), Dongyuan (DY) and Beibayao (BBY), low concentrations were observed at Changsha (CS), Beidaodi (BDD), and Gouqi (GQ). The concentration of HCHs and DDTs in most sites decreased clearly from 2006 to 2007 except for YKG, DY, BDD, LYS, and SS. All of above results suggested that the study area was slightly affected by organochlorine pesticide, special by DDTs.

Ma, Jizhen; Shen, Xinqiang; Yuan, Qi; Jiang, Mei

2008-11-01

292

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

293

Boron Nitride Nanomesh  

Microsoft Academic Search

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

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

2004-01-01

294

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

SciTech Connect

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

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

2012-07-01

295

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

296

Boron Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review  

USGS Publications Warehouse

Ecological and toxicological aspects of boron (B) in the environment are reviewed, with emphasis on natural resources. Subtopics covered include environmental chemistry, background concentrations, effects, and current recommendations for the protection of living resources. Boron is not now considered essential in mammalian nutrition, although low dietary levels protect against fluorosis and bone demineralization. Excessive consumption (i.e., >1,000 mg B/kg diet, >15 mg B/kg body weight daily, >1.0 mg B/L drinking water, or >210 mg B/kg body weight in a single dose) adversely affects growth, survival, or reproduction in sensitive mammals. Boron and its compounds are potent teratogens when applied directly to the mammalian embryo, but there is no evidence of mutagenicity or carcinogenicity. Boron`s unique affinity for cancerous tissues has been exploited in neutron capture radiation therapy of malignant human brain tumors. Current boron criteria recommended for the protection of sensitive species include <0.3 mg B/L in crop irrigation waters, <1.0 mg B/L for aquatic life, <5.0 mg B/L in livestock drinking waters, <30 mg B/kg in waterfowl diets, and <100 mg B/kg in livestock diets.

Eisler, R.

1990-01-01

297

Facile Synthesis of Ternary Boron Carbonitride Nanotubes.  

PubMed

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 degrees C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B-C-N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor-liquid-solid (VLS) mechanism was proposed for the growth of the nanotubes. PMID:20596377

Luo, Lijie; Mo, Libin; Tong, Zhangfa; Chen, Yongjun

2009-01-01

298

[Concentration distribution of metal elements in atmospheric aerosol under different weather conditions in Qingdao Coastal Region].  

PubMed

To know the influence of different weather conditions on the concentration of metal elements in aerosols in the coastal region, total suspended particles (TSP) samples were collected from April to May 2012, and August 2012 to March 2013 in the Qingdao coastal region, and common trace metals were analyzed by using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The results showed that Al, Ca, Fe, Na, K and Mg were the dominant metal elements in TSP, and the sum of the six elements accounted for 94.2% of the sum of all metals. TSP and metal elements had significant monthly variations, Fe, Al, K, Ca, Mg, Zn, Ba, Mn, Ti, Sr and Li had the highest concentration in November and January, while Be, Sc, Co, Ni and Cr showed the highest value in January. Na had the highest concentration in August, November and February, and the lowest in December. Pb had the highest concentration in January and February, and the lowest in August and December. Enrichment factors indicated that Be, Co, Al, Ca, Fe, K, Mg, Mn, Sr and Ti were mainly affected by natural sources; Li, Cr, Ni, Zn, Ba and Na were affected by natural sources and part of anthropogenic sources; Pb was mainly from anthropogenic sources. Different weather conditions had great impact on TSP and metal elements concentrations, all the measured metals had the highest concentrations in smog except Ti. Compared with the sunny day, the concentration of atmospheric particulate Ti decreased, while the other elements increased by 1 to 4 times in smog. Li, Be, Cr, Ni, Al, Fe, Mg and Mn had little variation in concentration in foggy day, and the concentration of Pb and Na increased considerably. The concentration of Co, Ca and Ti reduced obviously in fog. Except for Cr, Co and Ti, the other elements increased by 1 to 3 times in haze. Most of the elements had the minimal enrichment factors in sunny day, while the other had the maximal enrichment factor in foggy day. Enrichment factors of Ni, Zn, Ba, K, Na, Pb and Sr varied in the order of sunny day < haze day < smog day

Chen, Xiao-Jing; Qi, Jian-Hua; Liu, Ning; Zhang, Xiang-Yu; Shen, Heng-Qing; Liu, Ming-Xu

2014-10-01

299

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

300

Boron removal from aqueous solutions using alginate gel beads in fixed-bed systems  

PubMed Central

Background A column sorption study was carried out using calcium alginate gel beads as adsorbent for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of pH, initial concentration of boron, feed flow rate, adsorbent mass and column diameter. The breakthrough capacity values and adsorption percentage of calcium alginate gel for boron were calculated. Column data obtained at different conditions were described using the Adams–Bohart model and bed-depth service time (BDST), derived from the Adams–Bohart equation to predict breakthrough curves and to determine the characteristic column parameters required for process design. Results The maximum adsorption percentage of boron on calcium alginate gel beads using an initial concentration of boron of 50 mg L?1 at pH 11 and room temperature (20±1°C) was calculated to be 55.14%. Conclusion The results indicated that calcium alginate can be used in a continuous packed-bed column for boron adsorption. The optimal conditions for boron adsorption were obtained at high pH, higher initial boron concentration, increased column depth and lower flow velocity. © 2014 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Demey-Cedeño, Hary; Ruiz, Montserrat; Barron-Zambrano, Jesús Alberto; Sastre, Ana Maria

2014-01-01

301

Extractive fixed-site polymer sorbent for selective boron removal from natural water.  

PubMed

Water contamination by boron is a widespread environmental problem. The World Health Organization (WHO) recommends maximum boron concentration of 2.4 mg L(-1) for drinking water. The paper presents a simple method for preparation of functionalized sheet sorbent for selective extraction of boron from natural water. The pores of commercially available poly(propylene) membrane were functionalized by room temperature in situ crosslinking of poly(vinylbenzyl chloride) with a cyclic diamine piperazine. The precursor membranes were chemically modified with N-methyl D-glucamine which is selective for boron. Characterization of membrane was carried out using scanning electron microscopy (SEM) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) techniques. The functionalized membrane has been characterized in terms of parameters that influence the sorption of boron from aqueous streams like pH, uptake capacity, contact time, effects of competing ions and reusability. The maximum boron sorption capacity determined experimentally was 28 mg g(-1). The studies showed that trace concentrations of boron were quantitatively removed from water at neutral pH. The developed fixed site polymer sorbent exhibited high sorption capacity and fast kinetics as compared to various sorbents reported in literature. It was successfully applied for the removal of boron from ground water and seawater samples in presence of high concentration of interfering ions. PMID:23892170

Thakur, Neha; Kumar, Sanjukta A; Shinde, Rakesh N; Pandey, Ashok K; Kumar, Sangita D; Reddy, A V R

2013-09-15

302

Thermal conductivity of boron carbide-boron nitride composites  

Microsoft Academic Search

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

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

1992-01-01

303

Boron Nitride Nanotube Films Grown From Boron Ink Painting  

Microsoft Academic Search

The growth of nanotube films on various substrates and surfaces is vital for applications in nanoscale functional devices. We report a simple and versatile boron (B) ink painting method that enables high-density boron nitride nanotube (BNNT) films with any desired pattern to be grown on, and firmly attached to, different surfaces. In the method, special B ink is first painted,

Lu Hua Li; Ying Chen; Alexey M. Glushenkov

2010-01-01

304

Estimation of the temporal and spatial distribution of dust concentration over China by combining PM10 and conventional meteorological observations.  

PubMed

In this paper, we will present a simple algorithm to estimate the temporal and spatial distribution of dust mass concentration by combining PM10 and conventional meteorological observations. The efficiency of the algorithm has been demonstrated by applying it to analyze the dust source, transport, and dissipation of the dust storm which occurred in the west region of Pa-tan-chi-lin Desert at 0200 BST 27 March, 2004. PMID:19882221

Zhao, Fengsheng; Li, Xiaoqing; Gai, Changsong; Gao, Wenhua

2010-11-01

305

Concentrations, sources and spatial distribution of polycyclic aromatic hydrocarbons in soils from Beijing, Tianjin and surrounding areas, North China  

PubMed Central

The concentrations, profiles, sources and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) were determined in 40 surface soil samples collected from Beijing, Tianjin and surrounding areas, North China in 2007, and all sampling sites were far from industrial areas, roadsides and other pollution sources, and across a range of soil types in remote, rural villages and urban areas. The total concentrations of 16 PAHs ranged from 31.6 to 1475.0 ng/g, with an arithmetic average of 336.4 ng/g. The highest PAH concentrations were measured in urban soils, followed by rural village soils and soils from remote locations. The remote–rural village–urban PAH concentration gradient was related to population density, gross domestic product (GDP), long-range atmospheric transport and different types of land use. In addition, the PAH concentration was well correlated with the total organic carbon (TOC) concentration of the soil. The PAH profile suggested that coal combustion and biomass burning were primary PAH sources. PMID:20199833

Wang, Wentao; Massey Simonich, Staci L.; Xue, Miao; Zhao, Jingyu; Zhang, Na; Wang, Rong; Cao, Jun; Tao, Shu

2013-01-01

306

Method of fabricating boron containing coatings  

DOEpatents

Hard coatings are fabricated from boron nitride, cubic boron nitride, and multilayer boron/cubic boron nitride, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron is formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/cubic boron nitride, is produced by depositing alternate layers of boron and cubic boron nitride, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be discrete or of a blended or graded composition.

Makowiecki, Daniel M. (Livermore, CA); Jankowski, Alan F. (Livermore, CA)

1999-01-01

307

Method of fabricating boron containing coatings  

DOEpatents

Hard coatings are fabricated from boron nitride, cubic boron nitride, and multilayer boron/cubic boron nitride, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron is formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/cubic boron nitride, is produced by depositing alternate layers of boron and cubic boron nitride, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be discrete or of a blended or graded composition. 3 figs.

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

1999-04-27

308

The loss of boron in ultra-shallow boron implanted Si under heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Heavy ion impact has been known to cause a loss of light elements from the near-surface region of the irradiated sample. One of the possible approaches to a better understanding of the processes responsible for the release of specific elements is to irradiate shallow-implanted samples, which exhibit a well-known depth distribution of the implanted species. In this work, the samples studied were produced by implantation of Si wafers with 11 B at implantation energies of 250 and 500 eV and fluence of 1.0x10(15) atoms/cm 2 . Elastic Recoil Detection Analysis was applied to monitor the remnant boron fluence in the sample. Irradiation of the samples by a 14.2 (MeVF4+)-F-19 beam resulted in a slow decrease of boron remnant fluence with initial loss rates of the order of 0.05 B atom per impact ion. Under irradiation with 12 (MeVS3+)-S-32 ions, the remnant boron fluence in Si decreased exponentially with a much faster loss rate of boron and became constant after a certain heavy ion irradiation dose. A simple model, which assumes a finite desorption range and corresponding depletion of the near-surface region, was used to describe the observations. The depletion depths under the given irradiation conditions were calculated from the measured data.

Pelicon, P.; El Bouanani, M.; Prasad, G. V. R.; Razpet, A.; Simcic, J.; Guo, B. N.; Birt, D.; Duggan, J. L.; McDaniel, F. D.

2006-08-01

309

The distributed dislocation method applied to the analysis of elastoplastic strain concentrations  

NASA Astrophysics Data System (ADS)

Conventionally, the use of continuous distributions of dislocations to model plasticity has been confined to the analysis of crack tip plasticity using linear arrays of dislocations, within the framework of plane analysis. By expanding this technique into a distribution of dislocation over an area, a method is developed to model the plasticity at stress raising features such as notches or holes under plane strain conditions. The method explicitly takes account of the boundary conditions by using a dislocation solution which accounts for the presence of the stress-raise itself. Other free boundaries may be modelled more approximately using boundary elements which also correctly include the presence of the stress raiser. The dislocations are distributed over finite sized cells, and the solutions found for the strain fields compare favourably with both finite element and bounding Neuber and Glinka results.

Blomerus, P. M.; Hills, D. a.; Kelly, P. a.

1999-04-01

310

Distribution of uranium concentration in groundwater samples from the Peddagattu/Nambapur and Seripally regions using laser fluorimetry.  

PubMed

Uranium is a naturally occurring element, which is widespread in nature. It is found in low levels within all rocks, soils and water. Peddagattu and Seripally areas of Nalgonda district, Andhra Pradesh, India were known as a rich uranium mineralised zone. Atomic mineral division and Baba Atomic Research Center proposed a uranium mine in this area. This study was carried out to know the distribution of uranium concentration in the groundwater samples by using laser fluorimetry. The observation reveals that the uranium concentration in the groundwater of this region ranges from 0.6 to 521.15 ppb. About 43 % of the groundwater samples had the uranium concentration above the standards set by United States Environmental Protection Agency (30 ppb). PMID:24048245

Raghavendra, T; Srilatha, K; Mahender, C; Elander, M; Vijayalakshmi, T; Himabindu, V; Prasad, Vishwa; Padma Savithri, P; Datta, D; Arunachalam, J

2014-01-01

311

Azomethine H colorimetric method for determining dissolved boron in water  

USGS Publications Warehouse

An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

Spencer, R.R.; Erdmann, D.E.

1979-01-01

312

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

313

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

314

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...

315

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...

316

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

PubMed

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

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

2014-01-01

317

The Cascade Centripeter: A Device for Determining the Concentration and Size Distribution of Aerosols  

Microsoft Academic Search

This paper describes the application of a new principle for the continuous size separation of airborne particles in which the coarser fraction of the dust is concentrated in the center of an air stream converging through an orifice, and is removed by a coaxial nozzle downstream. The design and calibration of a prototype instrument is described. This device consists of

R. F. Hounam; R. J. Sherwood

1965-01-01

318

DISTRIBUTION OF FINGERLING BROOK TROUT, SALVELINUS FONTINALIS (MITCHELL), IN DISSOLVED OXYGEN CONCENTRATION GRADIENTS  

EPA Science Inventory

A self-recording linear gradient tank and procedures are described in which individual brook trout fingerlings unstressed by recent transfer, unaccustomed surroundings or the presence of an observer could move freely in 16 oxygen concentration gradients within the limits of 1 and...

319

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

PubMed Central

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

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

2014-01-01

320

Oxidation-enhanced diffusion of ion-implanted boron in silicon in extrinsic conditions  

NASA Astrophysics Data System (ADS)

Oxidation-enhanced diffusion (OED) of ion-implanted boron has been studied in extrinsic conditions, i.e, in a high boron concentration range by a new isoconcentration method using secondary ion mass spectroscopy (SIMS). In the isoconcentration method, 10B has been used as a tracer and 11B as a base, considering the SIMS measurement sensitivity. For isoconcentration diffusion at 950 and 1000 °C, diffusion coefficients both in N2 ambient and in dry O2 ambient increase with boron concentration in extrinsic conditions. The diffusion coefficient in dry O2 is larger than that in N2, i.e., OED is observed for boron concentration from intrinsic conditions to 1020 cm-3. The increment in the diffusion coefficient due to OED is constant for the boron concentration range of 2×1019-1×1020 cm-3, and is 2-3.5 times larger than that in intrinsic conditions. On the other hand, for boron implantation into intrinsic substrates, i.e., nonisoconcentration diffusion at 950 and 1000 °C, OED decreases with the dose and disappears at a 1015 cm-2 dose which has a peak boron concentration of about 4×1019 cm-3. The OED disappearance at the 1015 cm-2 dose is attributed to the loss of silicon interstitials by the residual damage due to implantation.

Miyake, Masayasu

1985-03-01

321

Residual stresses in boron/tungsten and boron/carbon fibers  

NASA Technical Reports Server (NTRS)

Longitudinal residual stress distribution is determined for 102-micron diam B/W and B/C fibers. The 102-micron diam B/W fibers are deposited on a 12.7-micron diam tungsten wire resistively heated in a BCl3-H2 reactor. The 102-micron diam B/C fibers are made by deposition of boron on a pyrolytic graphite-coated carbon fiber. The longitudinal residual stress distribution is calculated from measurements of the change in length of the fiber produced by removal of the surface through electropolishing. It is found that for both types of fibers, the residual stress vary from a compressive stress at the surface to a tensile stress in the boron near the core. Closer to the core and in the core, significant differences in the residual stresses are observed for the B/W and B/C fibers.

Behrendt, D. R.

1977-01-01

322

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

PubMed Central

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 with expression of genes involved in amino acid biosynthesis. These mechanisms are strictly controlled by the transcription factor Gcn4 in response to boron treatment. Further analyses have shown that boron impaired protein synthesis by promoting phosphorylation of eIF2? in a Gcn2 kinase dependent manner. The uncharged tRNA binding domain (HisRS) of Gcn2 is necessary for the phosphorylation of eIF2? in the presence of boron. We postulate that boron exerts its toxic effect through activation of the general amino acid control system and inhibition of protein synthesis. Since the general amino acid control pathway is conserved among eukaryotes, this mechanism of boron toxicity may be of general importance. PMID:22114689

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

2011-01-01

323

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

PubMed

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

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

2015-03-01

324

SOIL PHOSPHORUS DISTRIBUTION AND CONCENTRATION FROM REPEATED STARTER PHOSPHORUS BAND APPLICATION  

Microsoft Academic Search

Soil sampling to determine soil phosphorus (P) availability is complicated by the presence of residual P bands that have not been disturbed by tillage. This study investigated the soil P distribution and longevity of P bands applied in no-tillage culture on a Mollic Endoaqualf soil (fine, montmorillonitic, mesic). Starter band P treatments of 0, 5, 10, and 20 kg P

John Stecker; James R. Brown

2001-01-01

325

Monitoring of Chlorine Concentration in Drinking Water Distribution Systems Using an Interval Estimator  

Microsoft Academic Search

This paper describes the design of an interval observer for the estimation of unmeasured quality state variables in drinking water distribution systems. The estimator utilizes a set bounded model of uncertainty to produce robust interval bounds on the estimated state variables of the water quality. The bounds are generated by solving two differential equations. Hence the numerical efficiency is sufficient

Rafal Langowski; Mietek A. Brdys

2007-01-01

326

Boron deprivation decreases liver S-adenosylmethionine and spermidine and increases plasma homocysteine and cysteine in rats.  

PubMed

Two experiments were conducted with weanling Sprague-Dawley rats to determine whether changes in S-adenosylmethionine utilization or metabolism contribute to the diverse responses to boron deprivation. In both experiments, four treatment groups of 15 male rats were fed ground corn-casein based diets that contained an average of 0.05 mg (experiment 1) or 0.15 mg (experiment 2) boron/kg. In experiment 2, some ground corn was replaced by sucrose and fructose to increase oxidative stress. The dietary variables were supplemental 0 (boron-deprived) or 3 (boron-adequate) mg boron/kg and different fat sources (can affect the response to boron) of 75 g corn oil/kg or 65 g fish (menhaden) oil/kg plus 10 linoleic acid/kg. When euthanized at age 20 (experiment 1) and 18 (experiment 2) weeks, rats fed the low-boron diet were considered boron-deprived because they had decreased boron concentrations in femur and kidney. Boron deprivation regardless of dietary oil increased plasma cysteine and homocysteine and decreased liver S-adenosylmethionine, S-adenosylhomocysteine, and spermidine. Plasma concentration of 8-iso-prostaglandin F2alpha (indicator of oxidative stress) was not affected by boron, but was decreased by feeding fish oil instead of corn oil. Fish oil instead of corn oil decreased S-adenosylmethionine, increased spermidine, and did not affect S-adenosylhomocysteine concentrations in liver. Additionally, fish oil versus corn oil did not affect plasma homocysteine in experiment 1, and slightly increased it in experiment 2. The findings suggest that boron is bioactive through affecting the formation or utilization of S-adenosylmethionine. Dietary fatty acid composition also affects S-adenosylmethionine formation or utilization, but apparently through a mechanism different from that of boron. PMID:19486830

Nielsen, Forrest Harold

2009-01-01

327

Effect of fluorine implantation dose on boron thermal diffusion in silicon  

SciTech Connect

This paper investigates how the thermal diffusion of boron in silicon is influenced by a high energy fluorine implant with a dose in the range 5x10{sup 14}-2.3x10{sup 15} cm{sup -2}. Secondary Ion Mass Spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine profiles to establish the conditions under which thermal boron diffusion is suppressed. The (SIMS) profiles show significantly reduced boron thermal diffusion above a critical F{sup +} dose of 0.9-1.4x10{sup 15} cm{sup -2}. Fitting of the measured boron profiles gives suppressions of the boron thermal diffusion coefficient by factors of 1.9 and 3.7 for F{sup +} implantation doses of 1.4x10{sup 15} and 2.3x10{sup 15} cm{sup -2}, respectively. The suppression of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the (SIMS) profile in the vicinity of the boron marker layer. This shallow fluorine peak is present in samples with and without boron marker layers, and hence it is not due to a chemical interaction between the boron and the fluorine. Analysis of the (SIMS) profiles and cross-section Transmission Electron Microscope micrographs suggests that it is due to the trapping of fluorine at vacancy-fluorine clusters, and that the suppression of the boron thermal diffusion is due to the effect of the clusters in suppressing the interstitial concentration in the vicinity of the boron profile.

El Mubarek, H.A.W.; Bonar, J.M; Dilliway, G.D.; Ashburn, P.; Karunaratne, M.; Willoughby, A.F.; Wang, Y.; Hemment, P.L.F.; Price, R.; Zhang, J.; Ward, P. [School of Electronics and Computer Science, University of Southampton, Southampton (United Kingdom); Department of Materials, University of Southampton, Southampton (United Kingdom); School of Electrical and Electronic Engineering, University of Surrey, Guildford (United Kingdom); Department of Physics, Imperial College, University of London, London (United Kingdom); ST Microelectronics, Catania (Italy)

2004-10-15

328

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

PubMed Central

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). PMID:25750579

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

2015-01-01

329

Boron containing multilayer coatings and method of fabrication  

DOEpatents

Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition.

Makowiecki, Daniel M. (Livermore, CA); Jankowski, Alan F. (Livermore, CA)

1997-01-01

330

Spatial concentration distributions of sulfur dioxide and nitrogen oxides in Patras, Greece, in a winter period.  

PubMed

An economic and quick methodology for performing a preliminary spatial assessment of a city air quality with the purpose to identify locations and zones susceptible to high pollution levels is proposed. A Patras case-study is selected, regarding the air pollutants of sulfur dioxide (SO(2)) and oxides of nitrogen (NO(x)). A total number of 451 samples of short duration, of which 225 were randomly picked in morning rush hours and 226 within evening rush hours, were collected from 50 locations of the major Patras area during a year period, when peaks of primary air pollutants usually occur. Concentration measurements at prescribed locations used to statistically calculate spatial average concentrations approximating 1-h mean values with mean probable errors less than 25.9% for SO(2), NO and NO(x) and less than 15.5% for NO(2). Then iso-concentration contour diagrams plotted indicate high pollution zones and possibly appropriate locations for continuous or random monitoring according to the European Community (EC) Directives. The 1-h mean concentrations were in good correlation to the corresponding traffic rates and useful relationships are given (0.54

Yannopoulos, Panayotis C

2007-12-01

331

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 1,700 m from the MSWI stack. Total dl-PCN (dioxin-like PCN) concentrations in the stack gas samples ranged from 6898 and 89,032 pg m(-3), with a mean value of 36,241 pg m(-3). The total dl-PCN concentrations in the soil samples ranged from 30.35 to 280.9 pg g(-1), with a mean value of 87.03 and a median value of 70.32 pg g(-1), while the TEQ values were between 7.7 and 130.2 fg TEQ g(-1), with a mean value of 41.12 fg 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 (? 1,000 m 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

332

Concentration distributions of the drugs most frequently identified in post-mortem femoral blood representing all causes of death.  

PubMed

Interpreting the concentrations of drugs determined in post-mortem blood is not an easy task owing to poly-drug use, adverse drug-drug interactions, as well as a host of pre-analytical factors and various artefacts in post-mortem toxicology. Highly sensitive and specific methods (GC-FID, GC-NPD. GC-MS and LC-MS) were used to determine the concentrations of drugs in femoral blood from 24,876 autopsies representing all causes of death. Ethanol topped the list of psychoactive substances (N=8108 or 33%) at mean, median and highest concentrations of 1.43 g/L, 1.20 g/L and 8.0 g/L, respectively. In second place was paracetamol (N=2741 or 11%). Amphetamine and cannabis were the major illicit drugs at 13th and 15th positions, respectively. Newer antidepressants, citalopram (no 3), sertraline (no 14), venlafaxine (no 16) were prominent as were sedative-hypnotics, such as diazepam (no 4), zopiclone (no 5) and zolpidem (no 18). This compilation of drugs and their concentration distributions will be useful to identify and flag for a likely overdose or drug-related poisoning death. The drug concentration together with the findings at autopsy and the police report can then be used to reach a conclusion about the cause and manner of death. PMID:20025102

Jones, Alan Wayne; Holmgren, Anita

2009-10-01

333

Distributions and concentrations of thallium in surface waters of a region impacted by historical metal mining (Cornwall, UK).  

PubMed

Thallium is a highly toxic heavy metal whose concentrations and distributions in the aquatic environment are poorly defined. In this study, concentrations of aqueous and total Tl have been measured in water samples from a variety of rivers and effluents (the latter related to historical metal mining) in the county of Cornwall, SW England. Aqueous concentrations ranged from about 13 ng L(-1) in a river whose catchment contained no metal mines to 2,640 ng L(-1) in water abstracted directly from an abandoned mine shaft. Concentrations of Tl in rivers were greatest in the vicinity of mine-related effluents, with a maximum value measured of about 770 ng L(-1). Thallium was not efficiently removed by the conventional, active treatment of mine water, and displayed little interaction with suspended particles. Its mobility in surface waters, coupled with concentrations that are close to a quality guideline of 800 ng L(-1), is cause for concern. Accordingly, we recommend that the metal is more closely monitored in this and other regions impacted by mining activities. PMID:24368195

Tatsi, Kristi; Turner, Andrew

2014-03-01

334

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

PubMed Central

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

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

2013-01-01

335

Boron isotopes as an artificial tracer.  

PubMed

A field study was conducted using a combination of intrinsic and artificial tracers to estimate travel times and dilution during transport of infiltrate from a reclaimed water infiltration basin to nearby monitoring wells. A major study objective was to validate boric acid enriched in (10)B as an artificial tracer. Basin 10E at the Rio Hondo Spreading Grounds in Whittier, California, was the site of the test. The basin normally receives a mixture of treated municipal waste water, purchased State Project water, and local runoff from the San Gabriel River. Approximately 3.5 kg of (10)B-enriched boric acid was dispersed among 2.05 x 10(5) m(3) of basin water to initiate the experiment. The resultant median delta(11)B in the infiltration basin was -71 per thousand. Prior to tracer addition, the basin water had an intrinsic delta(11)B of +2 per thousand. Local monitoring wells that were used to assess travel times had delta(11)B values of +5 per thousand and +8 per thousand at the time of tracer addition. Analytic results supported an assumption that boron is conserved during ground water transport and that boron enriched in (10)B is a useful artificial tracer. Several intrinsic tracers were used to reinforce the boric acid tracer findings. These included stable isotopes of oxygen (delta(18)O) and hydrogen (deltaD), sulfate concentration, and the boron to chloride ratio. Xenon isotopes, (136)Xe and (124)Xe, also supported boron isotope results. Xenon isotopes were added to the recharge basin as dissolved gases by investigators from the Lawrence Livermore National Laboratory. PMID:16681525

Quast, Konrad W; Lansey, Kevin; Arnold, Robert; Bassett, Randy L; Rincon, Martha

2006-01-01

336

Distribution of terbium and increase of calcium concentration in the organs of mice i.v.-administered with terbium chloride.  

PubMed

To investigate the biological effects of terbium (Tb), male mice were intravenously administered with TbCl3 at 10, 25, or 50 mg Tb/kg. Time-course and dose-related changes in organ distributions of Tb were determined. More than 95% of the Tb in blood was in plasma, and the concentrations decreased rapidly. Contrary to normal pharmacokinetics, Tb concentrations in plasma were higher in the 10 mg/kg group than in the 50 mg/kg group. The concentrations after injection of 25 mg/kg were between 10 and 50 mg/kg injections. Tb was incorporated mainly in liver, lung, and spleen. In all groups more than 80% of Tb administered were found in these three organs. Disappearance of Tb in these organs was very slow. Tb was also found in kidney, heart and other organs. Coincidentally, it was found that the Ca concentration was increased in organs in which Tb was incorporated. After administration of Tb (50 mg/kg) the Ca concentration, compared to the controls, was 70-fold in spleen, 20-fold in lung, and 6-fold in liver. There were highly positive correlations between Tb and Ca concentrations in organs. Excretion of Tb in urine was 0.15-0.3% and that in feces was 1.7-12.5% for up to 7 days. These results indicate that liver, lung, and spleen are the main target organs of Tb administered intravenously, and that the increase in Ca concentrations is one of the important biological effects of Tb in target organs. PMID:9099429

Shinohara, A; Chiba, M; Inaba, Y

1997-03-01

337

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

PubMed

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

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

2014-09-01

338

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

339

Arabidopsis boron transporter for xylem loading  

Microsoft Academic Search

Boron deficiency hampers the productivity of 132 crops in more than 80 countries. Boron is essential in higher plants primarily for maintaining the integrity of cell walls and is also beneficial and might be essential in animals and in yeast. Understanding the molecular mechanism(s) of boron transport is crucial for alleviating boron deficiency. Here we describe the molecular identification of

Junpei Takano; Kyotaro Noguchi; Miho Yasumori; Masaharu Kobayashi; Zofia Gajdos; Kyoko Miwa; Hiroaki Hayashi; Tadakatsu Yoneyama; Toru Fujiwara

2002-01-01

340

Boron nitride nanotubes  

SciTech Connect

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 1, which is consistent with theoretical predictions of stable BN tube structures. 15 refs., 4 figs.

Chopra, N.G.; Luyken, R.J.; Cherrey, K. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)] [and others

1995-08-18

341

Functionalized boron nitride nanotubes  

DOEpatents

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

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

2014-04-22

342

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

Microsoft Academic Search

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

Nicholas V. C. Ralston; Curtiss D. Hunt

2004-01-01

343

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

SciTech Connect

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

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

2013-06-28

344

Characterization of Droplets and Vapor Concentration Distributions in Split-Injection Diesel Sprays by Processing UV and Visible Images  

NASA Astrophysics Data System (ADS)

Recent experimental studies have shown that with split injection strategy, the soot and NOx emissions from a diesel engine can be reduced significantly in comparison with a conventional non-split injection. To understand the mechanism of emissions reduction, it is essential to clarify the process of mixture formation in the diesel spray. For characterizing the droplets and vapor concentration distributions inside a fuel spray, a dual-wavelength laser absorption-scattering technique (LAS) was developed by using the 2nd harmonic (532nm) and the 4th harmonic (266nm) of an Nd: YAG laser and using dimethylnaphthalene as a test fuel. By applying the ultraviolet-visible LAS imaging technique, the distributions of droplets and vapor concentrations in the spray, which was injected into a high-temperature and high-pressure nitrogen ambient in a constant volume vessel by a common-rail diesel injection system, were measured and quantitatively analyzed. The effect of injection mass ratio of double-pulse injections on distributions of equivalence ratios of vapor and droplets in the sprays was examined.

Zhang, Yuyin; Nishida, Keiya; Yoshizaki, Takuo

345

Concentrations and distribution of organochlorine pesticides in pine needles of typical regions in Northern Xinjiang.  

PubMed

The residues of organochlorine pesticides (OCPs) in 29 pine needle samples of typical regions (including Shihezi, Beitun, and Kanas) in Northern Xinjiang was determined with a gas chromatograph equipped with an electron capture detector. Total OCPs concentrations in pine needles ranged from 2.94 to 186 ng/g dry weight, with a mean concentration of 39.63 ng/g. The results indicated that Beitun was the most polluted region while Kanas was the least polluted one. Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the predominant species in samples. Analysis of the sources of contamination showed that HCHs in the needles were derived from an old mixed source of technical HCHs or lindane. For DDTs, it was suspected to have recent application at some sites, which were derived mainly from a mixture of technical DDTs and dicofol containing DDT impurities. Categorical principal component analysis was performed in finding out more about the degradation behavior of DDTs and HCHs, which was identical with the results of source analysis. PMID:23740302

Lei, Xiaoning; Ran, Dan; Lu, Jianjiang; Du, Zhijian; Liu, Zilong

2015-02-01

346

Viscoelastic Behavior of PDMS Filled with Boron Nitrides  

Microsoft Academic Search

The addition of high thermal conductive filler particles such as boron nitride, aluminum nitride, or carbon fiber is an effective way to increase the thermal conductivity of polymeric materials for the industrial applications such as electronic packaging materials, encapsulants, and thermal fluids among others. The effects of particle dispersions, concentrations, and the interactions between BN and polymer matrix on the

J. F. Bian; D. H. Weinkauf; H. S. Jeon

2004-01-01

347

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

348

High precision chemical mechanical polishing of highly-boron-doped Si wafer used for epitaxial substrate  

Microsoft Academic Search

The surface waviness with concentric circular pattern is generated on highly-boron-doped Si wafer by chemical–mechanical polishing (CMP) with amine system polishing slurry. To investigate the generation mechanism of the waviness, the mechanical and chemical characteristics were clarified using the silicon crystal samples with various boron concentration level ranging from 2.9×1017cm?3 to 1.3×1020cm?3. The conventional silicon substrate used as epitaxial wafer

J. Watanabe; G. Yu; O. Eryu; I. Koshiyama; K. Izumi; K. Nakashima; M. Umeno; T. Jimbo; K. Kodama

2005-01-01

349

Boron doped diamond films: Electrical and optical characterization and the effect of compensating nitrogen  

Microsoft Academic Search

Polycrystalline diamond films were prepared by microwave plasma assisted chemical vapour deposition from CH4?H2 mixtures. For p-type doping with boron, trimethylborate was added at concentrations between 50 ppb and 500 ppm referred to the total gas phase. The boron concentration in the film, as determined by secondary ion mass spectrometry, varied between 1.1 × 1018 cm?3 and 2.1 × 1020

R. Locher; J. Wagner; F. Fuchs; C. Wild; P. Hiesinger; P. Gonon; P. Koidl

1995-01-01

350

Determination of Boron Contents in Water Samples Collected from the Neelum valley, Azad Kashmir, Pakistan  

Microsoft Academic Search

Intake of boron from food and drinking water may pose a risk to the public health above a certain concentration level. Therefore,\\u000a knowledge of boron concentration in drinking water and food items is essential. In this context, samples of drinking water\\u000a were collected from natural springs of the Neelum valley, Azad Kashmir, hit by devastating earthquake in 2005. In these

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

2011-01-01

351

Mineral oil in human tissues, Part I: concentrations and molecular mass distributions.  

PubMed

Of 37 subjects aged 25-91 y (mean 67 y), mineral oil hydrocarbons were measured in subcutaneous abdominal fat tissue, mesenteric lymph nodes (MLN), spleen, liver and lung, for some of them also in kidney, heart and brain. No mineral oil aromatic hydrocarbons (MOAH) were detected. The mean concentration of mineral oil saturated hydrocarbons (MOSH) in the mesenteric lymph nodes was 223 mg/kg, in liver 131 mg/kg, in fat tissue 130 mg/kg, in spleen 93 mg/kg and in lung 12 mg/kg. They were clearly lower in kidney, heart and brain. The maxima, found in MLN and spleen, were 1390 and 1400 mg/kg, respectively. For a quarter of the subjects a total amount of MOSH in the body above 5 g was calculated. The MOSH composition in the fat tissue and the MLN appeared virtually identical and varied little between the subjects. It was centered on the n-alkanes C23-C24, ranged from C16 to C35 and included hydrocarbons of plant origin. The MOSH in spleen and liver had almost the same composition for a given subject, but varied somewhat between subjects. They were centered between C25 and C27, ranged from C18 to beyond C45 and were without hydrocarbons of plant origin. Part of the MOSH seem to be strongly accumulated, resulting in far higher concentrations in human tissues related to exposure than observed in shorter term animal experiments. The composition of the accumulated MOSH does not support that Class I mineral oils, sometimes termed "food grade", are less accumulated in the human body than Class II and III oils, which questions the present classification. PMID:24780493

Barp, Laura; Kornauth, Christoph; Wuerger, Tanja; Rudas, Margaretha; Biedermann, Maurus; Reiner, Angelika; Concin, Nicole; Grob, Koni

2014-10-01

352

Effects of diesel exhaust aftertreatment devices on concentrations and size distribution of aerosols in underground mine air.  

PubMed

Three types of uncatalyzed diesel particulate filter (DPF) systems, three types of high-temperature disposable filter elements (DFEs), and one diesel oxidation catalytic converter (DOC) were evaluated in underground mine conditions for their effects on the concentrations and size distributions of diesel aerosols. Those effects were compared with the effects of a standard muffler. The experimental work was conducted directly in an underground environment using a unique diesel laboratory developed in an underground experimental mine. The DPF systems reduced total mass of aerosols in the mine air approximately 10-fold for light-load and 20-fold or more for high-load test conditions. The DFEs offered similar reductions in aerosol mass concentrations. The efficiency of the new DFEs significantly increased with accumulation of operating time and buildup of diesel particulate matter in the porous structure of the filter elements. A single laundering process did not exhibit substantial effects on performance of the filter element The effectiveness of DPFs and DFEs in removing aerosols by number was strongly influenced by engine operating mode. The concentrations of nucleation mode aerosols in the mine air were found to be substantially higher for both DPFs and DFEs when the engine was operated at high-load modes than at low-load modes. The effects of the DOC on mass and number concentrations of aerosols in mine air were relatively minor when compared to those of the DPF and DFE systems. PMID:19764243

Bugarski, Aleksandar D; Schnakenberg, George H; Hummer, Ion A; Cauda, Emanuele; Janisko, Samuel I; Patts, Larry D

2009-09-01

353

Chromium boron surfaced nickel-iron base alloys  

NASA Technical Reports Server (NTRS)

Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

1984-01-01

354

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

PubMed Central

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

2012-01-01

355

Structure and superconductivity of isotope-enriched boron-doped diamond  

SciTech Connect

Superconducting boron-doped diamond samples were synthesized with isotopes of {sup 10}B, {sup 11}B, {sup 13}C and {sup 12}C. We claim the presence of a carbon isotope effect on the superconducting transition temperature, which supports the 'diamond-carbon'-related nature of superconductivity and the importance of the electron-phonon interaction as the mechanism of superconductivity in diamond. Isotope substitution permits us to relate almost all bands in the Raman spectra of heavily boron-doped diamond to the vibrations of carbon atoms. The 500 cm{sup 01} Raman band shifts with either carbon or boron isotope substitution and may be associated with vibrations of paired or clustered boron. The absence of a superconducting transition (down to 1.6 K) in diamonds synthesized in the Co-C-B system at 1900 K correlates with the small boron concentration deduced from lattice parameters.

Thompson, Joe D [Los Alamos National Laboratory; Ekimov, E A [INSTIT OF HIGH PRESSURE; Sidorov, V A [INSTIT OF HIGH PRESSURE; Zoteev, A [MOSCOW SU; Lebed, Y [INST FOR NUCI RES; Stishov, S M [INST FOR HIGH PRESSURE

2008-01-01

356

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

357

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

SciTech Connect

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

Romero, V.J.

1994-03-01

358

Inhalation toxicology of red and violet mixtures. Chamber concentration and particle-size distribution report  

SciTech Connect

An inhalation exposure facility was developed at the U.S. EPA, RTP, NC to conduct inhalation exposures of rodents and guinea pigs to dye mixtures used by the U.S. Army in the manufacture of smoke munitions. Initially, an evaluation of the prototype chamber aerosol homogeneity was conducted to determine the uniformity and reproducibility of the concentration and particle size of dye aerosol throughout the breathing zone of the test animals. The three dyes, DR11, SR1, and DB3, were chemically analyzed for purity and optically examined for size and shape. All pure dyes appeared to be stable at room temperature except DB3, which decomposes if not stored at 4 C. The particle size ranges varied for each pure dye and structures were either amorphous (azo dye) or crystalline (anthraquinone dyes). The bulk red and violet dye mixtures were analyzed for composition. The chemical analysis of the relative composition of each dye mixture, collected by cascade impactor sampling, revealed fractionation of the mixtures into component dyes.

Higuchi, M.A.; Davies, D.W.

1991-07-01

359

Addition of oxygen to and distribution of oxides in tantalum alloy T-111 at low concentrations  

NASA Technical Reports Server (NTRS)

Oxygen was added at 820 and 990 C at an oxygen pressure of about .0003 torr. The technique permitted predetermined and reproducible oxygen doping of the tantalum alloy (T-111). Based on the temperature dependency of the doping reaction, it was concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the tantalum and tungsten oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and oxygen from other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990 C but not at 820 C. The vaporization of WO3 has no apparent effect on the doping reaction.

Stecura, S.

1975-01-01

360

Spectrophotometric determination of traces of boron in high purity silicon  

SciTech Connect

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

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

1989-07-01

361

Carbon-rich icosahedral boron carbide designed from first principles  

SciTech Connect

The carbon-rich boron-carbide (B{sub 11}C)C-C has been designed from first principles within the density functional theory. With respect to the most common boron carbide at 20% carbon concentration B{sub 4}C, the structural modification consists in removing boron atoms from the chains linking (B{sub 11}C) icosahedra. With C-C instead of C-B-C chains, the formation of vacancies is shown to be hindered, leading to enhanced mechanical strength with respect to B{sub 4}C. The phonon frequencies and elastic constants turn out to prove the stability of the carbon-rich phase, and important fingerprints for its characterization have been identified.

Jay, Antoine; Vast, Nathalie; Sjakste, Jelena; Duparc, Olivier Hardouin [Ecole Polytechnique, Laboratoire des Solides Irradiés, CEA-DSM-IRAMIS, CNRS UMR 7642, F-91120 Palaiseau (France)

2014-07-21

362

Boron neutron capture therapy (BNCT): A radiation oncology perspective  

SciTech Connect

Boron neutron capture therapy (BNCT) offers considerable promise in the search for the ideal cancer therapy, a therapy which selectively and maximally damages malignant cells while sparing normal tissue. This bimodal treatment modality selectivity concentrates a boron compound in malignant cells, and then [open quotes]activates[close quotes] this compound with slow neutrons resulting in a highly lethal event within the cancer cell. This article reviews this treatment modality from a radiation oncology, biology, and physics perspective. The remainder of the articles in this special issue provide a survey of the current [open quotes]state-of-the-art[close quotes] in this rapidly expanding field, including information with regard to boron compounds and their localization. 118 refs., 3 figs.

Dorn, R.V. III (Mountain States Tumor Institute, Boise, ID (United States) Idaho National Engineering Lab., Idaho Falls, ID (United States))

1994-03-30

363

Ordering of carbon atoms in boron carbide structure  

SciTech Connect

Boron carbide crystals have been obtained in the entire compositional range according to the phase diagram by self-propagating high-temperature synthesis (SHS). Based on the results of X-ray diffraction investigations, the samples were characterized by the unit-cell metric and reflection half-width in the entire range of carbon concentrations. A significant spread in the boron carbide unit-cell parameters for the same carbon content is found in the data in the literature; this spread contradicts the structural concepts for covalent compounds. The SHS samples have not revealed any significant spread in the unit-cell parameters. Structural analysis suggests that the spread of parameters in the literary data is related to the unique process of ordering of carbon atoms in the boron carbide structure.

Ponomarev, V. I., E-mail: i2212@yandex.ru; Kovalev, I. D.; Konovalikhin, S. V.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

2013-05-15

364

An evaluation of spot tests for boron and the development of a superior spot test for boron  

E-print Network

hydroxide, indicates the presence of boric acid. Limit of Identification& 0. 02 V boron Concentration Limit: 1:2, 500, 000 (b) " A 4rop of the test solution is placed on a microscope slide and acidified with a drop of hydrochloric acid. . A thread... hydroxyanthraquinones. The bydroxyanthraguinone test for boron was de- veloped from tests for hydroxyanthra ?uinones ucin& boric acid (1 &) ~ The probabls requirement for this test is that t;he hy. &roxyl groups be so placed as to be conducive to formation of 1nner...

Van Tuyl, Dixon Peacock

1954-01-01

365

TCAD modeling and simulation of boron deactivation in NMOS carbon-implanted channel  

NASA Astrophysics Data System (ADS)

Carbon co-implant is well known to suppress boron transient enhanced diffusion (TED) in silicon. The modeling of carbon-interstitial clusters (CICs) has been extensively studied and is now widely used in Technology Computer Aided Design (TCAD). It has already been reported in literature that carbon implant in the channel of NMOS transistor is highly effective for the suppression of oxidation-enhanced diffusion (OED) of boron while leading to poor boron activation. In order to account for this deactivation, we need to consider that the active boron equilibrium concentration is modified by the presence of carbon in non-amorphized silicon region with high concentration of interstitials. In this paper, for the first time, we show the effective TCAD modeling of boron deactivation in the presence of carbon in a NMOS transistor. The model is based on boron-carbon-interstitial clusters formed in the non-amorphized silicon region, thereby reducing active boron concentration. The model can be applied to accurately predict variations of threshold voltage as a function of channel length for NMOS devices with carbon implanted into the channel or halo regions. The tool used in this work is a commercial simulator based on the continuum approach.

Mok, K. R. C.; Benistant, F.; Teo, R. S.; Chu, S.

2009-06-01

366

Boron hazards to fish, wildlife, and invertebrates: A synoptic review  

SciTech Connect

Ecological and toxicological aspects of boron (B) in the environment are reviewed, with emphasis on natural resources. Subtopics covered include environmental chemistry, background concentrations, effects, and current recommendations for the protection of living resources. Boron is not now considered essential in mammalian nutrition, although low dietary levels protect against fluorosis and bone demineralization. Excessive consumption (i.e., >1,000 mg B/kg diet, >15 mg B/kg body weight daily, >1.0 mg B/L drinking water, or >210 mg B/kg body weight in a single dose) adversely affects growth, survival, or reproduction in sensitive mammals. Boron and its compounds are potent teratogens when applied directly to the mammalian embryo, but there is no evidence of mutagenicity or carcinogenicity. Boron's unique affinity for cancerous tissues has been exploited in neutron capture radiation therapy of malignant human brain tumors. Current boron criteria recommended for the protection of sensitive species include <0.3 mg B/L in crop irrigation waters, <1.0 mg B/L for aquatic life, <5.0 mg B/L in livestock drinking waters, <30 mg B/kg in waterfowl diets, and <100 mg B/kg in livestock diets.

Eisler, R.

1990-04-01

367

Boron suboxide: As hard as cubic boron nitride  

Microsoft Academic Search

The Vickers hardness of boron suboxide single crystals was measured using a diamond indentation method. Under a loading force of 0.98 N, our test gave an average Vickers hardness of 45 GPa. The average fracture toughness was measured as 4.5 MPa m1\\/2. We also measured the hardness of the cubic boron nitride and sapphire single crystals for comparison. The average

Duanwei He; Yusheng Zhao; L. Daemen; J. Qian; T. D. Shen; T. W. Zerda

2002-01-01

368

Synthesis of boron nitride nanotubes by boron ink annealing  

Microsoft Academic Search

Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing

Lu Hua Li; Ying Chen; Alexey M. Glushenkov

2010-01-01

369

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

370

Distribution of Microbial Arsenic Reduction, Oxidation and Extrusion Genes along a Wide Range of Environmental Arsenic Concentrations  

PubMed Central

The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations. PMID:24205341

Escudero, Lorena V.; Casamayor, Emilio O.; Chong, Guillermo; Pedrós-Alió, Carles; Demergasso, Cecilia

2013-01-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

372

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

E-print Network

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

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

2010-09-03

373

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

NASA Astrophysics Data System (ADS)

We perform a comparative study of the free energies and the density distributions in hard-sphere crystals using Monte Carlo simulations and density functional theory (employing Fundamental Measure functionals). Using a recently introduced technique [T. Schilling and F. Schmid, J. Chem. Phys. 131, 231102 (2009)10.1063/1.3274951] we obtain crystal free energies to a high precision. The free energies from fundamental measure theory are in good agreement with the simulation results and demonstrate the applicability of these functionals to the treatment of other problems involving crystallization. The agreement between fundamental measure theory and simulations on the level of the free energies is also reflected in the density distributions around single lattice sites. Overall, the peak widths and anisotropy signs for different lattice directions agree, however, it is found that fundamental measure theory gives slightly narrower peaks with more anisotropy than seen in the simulations. Among the three types of fundamental measure functionals studied, only the White Bear II functional [H. Hansen-Goos and R. Roth, J. Phys.: Condens. Matter 18, 8413 (2006)10.1088/0953-8984/18/37/002] exhibits sensible results for the equilibrium vacancy concentration and a physical behavior of the chemical potential in crystals constrained by a fixed vacancy concentration.

Oettel, M.; Görig, S.; Härtel, A.; Löwen, H.; Radu, M.; Schilling, T.

2010-11-01

374

Potential and current density distributions of cranial electrotherapy stimulation (CES) in a four-concentric-spheres model.  

PubMed

Cranial electrotherapy stimulation (CES) has been successfully used for treatment of many psychiatric diseases. Its noninvasive nature is its major advantage over other forms of treatments such as drugs. It is postulated that the low electric current of CES causes the release of neurotransmitters. However, the current pathways have not been extensively investigated. In the following paper, analytical and numerical methods are used to determine the distribution of potential and current density in a four zone concentric spheres model of the human head when excited by two electrodes diametrically opposite to each other. Because of the azimuthal symmetry, which is assumed in this study, a two-dimensional (2-D) finite difference approximation is derived in the spherical grid. The current density distribution is projected around the center of the model, where the thalamus is modeled as a concentric sphere. All dimensions and electrical properties of the model are adapted from clinical data. Results of this simulation indicate that, in contrast to previous beliefs, a small fraction of the CES current does reaches the thalamic area and may facilitate the release of neurotransmitters. PMID:9214809

Ferdjallah, M; Bostick, F X; Barr, R E

1996-09-01

375

Nano boron nitride flatland.  

PubMed

Recent years have witnessed many breakthroughs in research on two-dimensional (2D) nanomaterials, among which is hexagonal boron nitride (h-BN), a layered material with a regular network of BN hexagons. This review provides an insight into the marvellous nano BN flatland, beginning with a concise introduction to BN and its low-dimensional nanostructures, followed by an overview of the past and current state of research on 2D BN nanostructures. A comprehensive review of the structural characteristics and synthetic routes of BN monolayers, multilayers, nanomeshes, nanowaves, nanoflakes, nanosheets and nanoribbons is presented. In addition, electronic, optical, thermal, mechanical, magnetic, piezoelectric, catalytic, ecological, biological and wetting properties, applications and research perspectives for these novel 2D nanomaterials are discussed. PMID:24280706

Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

2014-02-01

376

Concentration and Distribution of Well Drilling in the Amargosa Desert Area of Southern Nevada  

NASA Astrophysics Data System (ADS)

The earliest sources of fresh water supply in the Amargosa Desert area of Southern Nevada were the abundant, naturally occurring (cold) springs. They initially sustained the indigenous Native American populations and later, Euro-American miners, farmers, and ranchers. Prior to 1900, the many local springs and a few (mostly shallow) hand-dug wells were the principal sources of water supply. The first hand-dug well in the area was the Franklin well; it was dug in 1852 for workers performing a survey of the California-Nevada State line. The first mechanically bored wells were drilled for local railroads, along their respective alignments, sometime between 1905-07. About 1917, the first irrigation well in the Amargosa Desert area was drilled for an experimental farm operated by the Tonopah and Tidewater Railroad. In the late 1940s-early 1950s, permanent interest in the area was established, in large measure because of a Federally sponsored desert reclamation program. For the period 1900-1999, a preliminary evaluation of publicly available information (collected principally by the State Engineer) indicates that more than 950 boreholes were drilled in the Amargosa Desert area. Almost half of these boreholes were drilled in the last 20 years. Forty-two percent of the boreholes were drilled to supply fresh drinking water; 26 percent were in support of irrigated agriculture; 21 percent of the wells were drilled for some non-water supply related purpose - ground-water monitoring and testing; and 11 percent were drilled to supply water for commercial or unspecified applications. Most of the well drilling has been concentrated in a parcel of land about 30-40 kilometers south of the proposed geologic repository at Yucca Mountain, Nevada. Most wells have been generally drilled to depths less than 30 meters (100 feet), although deeper wells are uncommon. The main reason is that drilling is expensive and the profitability of finding and extracting potable water, in sufficient quantity, generally declines with depth. However, during the last two decades, there has been a general decline in drilling for irrigation. Designation of local aquifers in the area as "protected" in 1979 has favored new well-permitting for residential or commercial uses. Moreover, in the 1990s, local farmers were required to forfeit unused water rights and these rights have been reallocated to new, non-farming residents by the State Engineer in Nevada's Department of Conservation and Natural Resources. Nevertheless, the general decline in irrigation permitting for farming over the last several decades most likely has more to do with the physical and/or economic factors that have historically controlled local farming rather than with recent water availability issues.

Lee, M. P.; Gross, A. J.; Coleman, N. M.

2002-05-01

377

Spatial Distribution of Lead Isotope Ratios and Inorganic Element Concentrations in Epiphytic Lichens from the Athabasca Oil Sands Region  

NASA Astrophysics Data System (ADS)

Coupled studies of inorganic element concentrations and lead (Pb) isotope ratios have been conducted on Hypogymnia physodes samples collected in the Athabasca Oil Sands Region (AOSR) in Alberta, Canada in 2002, 2008, and 2011. To investigate the spatial extent of air emissions, the lichens were collected from sites as far as 160 km from the mining and processing operations. 30 milligram sub-samples of the lichens were microwave digested, and the extracts were analyzed using DRC-ICPMS to determine elemental concentrations, and sector field ICPMS to measure Pb isotope ratios. Concentrations of elements in the lichens were found to reflect proximity to mining and oil processing sites as well as topography, ecosystem differences, and the metabolic biogeochemistry of the lichens. An exponential decrease in concentration of metals associated with fugitive dust (aluminum and others) versus distance from the mining sites, suggests elevated coarse particle emissions associated with mining operations. Near source concentrations of metals with an oil signature (vanadium and others) are less enhanced and more homogeneous than the metals in the fugitive dust, reflecting emission and deposition of smaller diameter particles at greater distances from oil processing sources. The mining and oil processing signatures are superimposed over elemental concentrations that reflect the nutrient needs of the lichens. These findings are being confirmed through ongoing studies using dichot samplers to collect coarse and fine particulate aerosol samples. The lichen samples collected beyond 50 km from the mining and processing sites cluster into a Pb isotope grouping with a 207Pb / 206Pb ratio of 0.8650 and a 208Pb / 206Pb ratio near 2.095. This grouping likely reflects the regional background Pb isotope ratio signature. 207Pb / 206Pb and 208Pb / 206Pb ratios decrease as one nears the mining and processing operations. This indicates that other Pb source(s), (e.g. Pb in the bitumen from the oil sands), are contributing to the Pb accumulated by the lichens. The Pb isotope ratios are a better indicator of the spatial distribution resulting from atmospheric deposition than the Pb concentrations because the Pb isotope ratios are not affected by the potential for canopy interactions or preferential metabolic processing of elements by the lichens.

Graney, J. R.; Landis, M. S.; Puckett, K.; Edgerton, E.; Krupa, S.; Percy, K.

2013-12-01

378

Processing of boron carbide  

NASA Astrophysics Data System (ADS)

The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although the relative densities of pressureless sintered specimens were lower than that of commercially produced hot-pressed B4C, their (Vickers) hardness values were comparable. For 4.45 cm dia. 1.35 cm height disk-shaped specimens, pressureless sintered to at least 93.0% relative density, post-hot isostatic pressing resulted in vast increases in relative densities (e.g. 100.0%) and hardness values significantly greater than that of commercially produced hot-pressed B 4C. The densification behavior of 20-40nm graphite-coated B4C nano-particles was studied using dilatometry, x-ray diffraction and electron microscopy. The higher than expected sintering onset from a nano-scale powder (˜1500°C) was caused by remnant B2O3 not removed by methanol washing, keeping particles separated until volatilization, and the carbon coatings, which imposed particle to particle contact of a substance more refractory than B4C. Solid state sintering (1500-1850°C) was followed by an arrest in contraction attributed to formation of eutectic liquid droplets of size more than 10X the original nano-particles. These droplets, induced to form well below known B4C-graphite eutectic temperatures by the high surface energy of nanoparticles, are interpreted to have quickly solidified to form a vast number of voids in particle packing, which in turn, impeded continued solid state sintering. Starting at 2200°C, a permanent liquid phase formed which facilitated a rapid measured contraction by liquid phase sintering and/or compact slumping.

Cho, Namtae

379

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

USGS Publications Warehouse

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

Opsahl, Stephen P.; Lambert, Rebecca B.

2013-01-01

380

Diel changes in trace metal concentration and distribution in coastal waters: Catalina Island as a study case.  

PubMed

Understanding biogeochemical cycling of trace metals in the ocean requires information about variability in metal concentrations and distribution over short, e.g., diel, time scales. Such variability and the factors that influence it are poorly characterized. To address this shortcoming, we measured trace metal concentrations in the total dissolved, colloidal, and soluble fractions every 3-4 h for several consecutive days and nights in surface waters from a coastal station. Our results show that both the concentration and the size partitioning of some biologically essential (Fe, Cu, Co, and Cd) and anthropogenic (Pb) metals are subjected to diel variations that may be related to both inorganic and biological processes (e.g., photolysis of high-molecular-weight dissolved organic matter, photoinduced reduction/oxidation of metal(hydrous)oxides, uptake by growing phytoplankton, degradation of organic matter, lysis, and grazing). The largest fluctuations were observed in the soluble and colloidal pools. Soluble Fe varied during the day-night cycle by a factor of 40, and the contribution of colloidal Pb to the total dissolved fraction increased from 6±3% during the day to as much as 70-80% during the night. Our results suggest that changes occurring over time scales of hours need to be considered when collecting and interpreting trace metal data from the surface ocean. PMID:24952958

Pinedo-Gonzalez, Paulina; West, A Joshua; Rivera-Duarte, Ignacio; Sañudo-Wilhelmy, Sergio A

2014-07-15

381

Molecular Structure of Boron trifluoride  

NSDL National Science Digital Library

Boron trifluoride has a trigonal pryamidal shape and dissolves in diethyl ether. Normally a gas, boron trifluoride is a hard and strong Lewis acid with a high affinity in displacement reactions and is therefore used mainly as a catalyst in alkylations, polymerizations and esterifications. It extracts bases bound to carbon and produces carbocations. Also it is used as a fumigant and in the magnesium industry because its anti-oxidant properties.

2002-08-15

382

Neutron detectors comprising boron powder  

DOEpatents

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

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

2013-05-21

383

The Boron Solar Neutrino Experiment  

Microsoft Academic Search

Neutrino excitation of the nuclear levels (NUEX) of 11B and charged-current (CC) excited inverse beta-decay of 11B to 11C, provide a double mode detection of solar nu's in a target of boron. Aspects of detector techniques and backgrounds in the Boron solar nu experiment, now under development, as well as its response to various non-standard nu scenarios are presented.

R. S. Raghavan

1987-01-01

384

Carbothermic formation of boron nitride  

Microsoft Academic Search

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

A. Aydo?du; N. Sevinç

2003-01-01

385

Boron-carbide-aluminum and boron-carbide-reactive metal cermets. [B/sub 4/C-Al  

DOEpatents

Hard, tough, lighweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidated step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modules of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi..sqrt..in. These composites and methods can be used to form a variety of structural elements.

Halverson, D.C.; Pyzik, A.J.; Aksay, I.A.

1985-05-06

386

IMPAIRMENT OF GROWTH AND IMMUNE FUNCTION OF AVOCET CHICKS FROM SITES WITH ELEVATED SELENIUM, ARSENIC, AND BORON  

EPA Science Inventory

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. elenium, arsenic, and boron residues were measured in...

387

Fine mapping the spatial distribution and concentration of unlabeled drugs within tissue micro-compartments using imaging mass spectrometry.  

PubMed

Readouts that define the physiological distributions of drugs in tissues are an unmet challenge and at best imprecise, but are needed in order to understand both the pharmacokinetic and pharmacodynamic properties associated with efficacy. Here we demonstrate that it is feasible to follow the in vivo transport of unlabeled drugs within specific organ and tissue compartments on a platform that applies MALDI imaging mass spectrometry to tissue sections characterized with high definition histology. We have tracked and quantified the distribution of an inhaled reference compound, tiotropium, within the lungs of dosed rats, using systematic point by point MS and MS/MS sampling at 200 microm intervals. By comparing drug ion distribution patterns in adjacent tissue sections, we observed that within 15 min following exposure, tiotropium parent MS ions (mass-to-charge; m/z 392.1) and fragmented daughter MS/MS ions (m/z 170.1 and 152.1) were dispersed in a concentration gradient (80 fmol-5 pmol) away from the central airways into the lung parenchyma and pleura. These drug levels agreed well with amounts detected in lung compartments by chemical extraction. Moreover, the simultaneous global definition of molecular ion signatures localized within 2-D tissue space provides accurate assignment of ion identities within histological landmarks, providing context to dynamic biological processes occurring at sites of drug presence. Our results highlight an important emerging technology allowing specific high resolution identification of unlabeled drugs at sites of in vivo uptake and retention. PMID:20644728

Nilsson, Anna; Fehniger, Thomas E; Gustavsson, Lena; Andersson, Malin; Kenne, Kerstin; Marko-Varga, György; Andrén, Per E

2010-01-01

388

Inelastic properties of boron oxides  

NASA Astrophysics Data System (ADS)

Temperature dependence of internal friction and dynamic shear modulus for boron anhydride (B2O3) and boron suboxide (B6O) have been investigated at frequencies of 1-10 Hz and over the temperature range 80-900 K. Absolute shear modulus for boron suboxide at 80 and 400 K was 0.9 and 0.85 GPa, respectively. Relaxation maximum of internal friction, accompanied with shear modulus defect had activation energy of 0.8 eV, and frequency factor of ˜1.1012 s-1. Measruements of absolute values of boron suboxide shear modulus at various temperatures showed deviations from linear decrease above 670 K. In the internal friction spectrum at temperatures of 410 and 700 K the maxima of origin have been revealed. At temperatures of 595 and 650-700 K an intense maxima of internal friction and shear modulus defects were observed. Many of the relaxation and hysteretic processes have been discussed accounting on the possiblity of formation of point defects (oxygen vacancies, unbonded boron atoms), split dislocations and polysynthetic twins in the (001) rhombohedral planes, lowering down the local symmetry in the boron suboxide crystal structure.

Tushishvili, M. Ch.; Darsavelidze, G. Sh.; Tsagareishvili, O. A.; Bairamashvili, I. A.; Jobava, J. Sh.

1991-07-01

389

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

PubMed

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

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

2014-04-01

390

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

EPA Science Inventory

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

391

On the vertical distribution of the chlorophyll a concentration in the Mediterranean Sea: a basin scale and seasonal approach  

NASA Astrophysics Data System (ADS)

The distribution of the chlorophyll a concentration ([Chl a]) in the Mediterranean Sea, which is mainly obtained from satellite surface observations or from scattered in situ experiments, is updated by analyzing a database of fluorescence profiles calibrated into [Chl a]. The database, which includes 6790 fluorescence profiles from various origins, was processed with a dedicated quality control procedure. To ensure homogeneity between the different data sources, 65% of fluorescence profiles have been inter-calibrated on the basis of their concomitant satellite [Chl a] estimation. The climatological pattern of [Chl a] vertical profile in four key sites of the Mediterranean Sea has been analyzed. Climatological results confirm previous findings on the range of [Chl a] values and on the main Mediterranean trophic regimes. It also provides new insights on the seasonal variability of the shape of the vertical [Chl a] profile, inaccessible from remote sensing observations. An analysis based on the recognition of the general shape of the fluorescence profile was also performed. Although the shape of [Chl a] vertical distribution characterized by a deep chlorophyll maximum (DCM) is ubiquitous during summer, different forms are observed during winter, suggesting thus that factors affecting the vertical distribution of the biomass are complex and highly variable. The [Chl a] distribution in the Mediterranean Sea mimics, at smaller scales, what is observed in the Global Ocean. As already evidenced by analyzing satellite surface observations, mid-latitude and subtropical like phytoplankton dynamics coexist in the Mediterranean Sea. Moreover, the Mediterranean DCM variability appears characterized by patterns already observed at global scale.

Lavigne, H.; D'Ortenzio, F.; Ribera D'Alcalà, M.; Claustre, H.; Sauzède, R.; Gacic, M.

2015-03-01

392

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

NASA Astrophysics Data System (ADS)

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

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

393

Inversion of population distribution of felodipine conformations at increased concentration in dimethyl sulfoxide is a prerequisite to crystal nucleation.  

PubMed

Knowledge of the preferred conformations of biologically active compounds is of the utmost importance for a better understanding of the structure-activity relationships underlying their biological activity, as well as their mechanism of action. Moreover, investigating the mechanism of nucleation from a saturated solution can facilitate the discovery and preparation of new polymorphic forms. To search regularities in the crystal nucleation of biologically active compounds (drugs) from a saturated solution, we studied the conformational preference of felodipine in dilute and saturated solution in dimethyl sulfoxide. The inversion of conformation distribution at increased concentration occurs: conformers that dominate in a dilute solution become the least abundant in the saturated one. Conformers that dominate in the saturated solution are of the same type as revealed in crystalline state by X-ray. PMID:24395609

Khodov, Ilya A; Efimov, Sergey V; Nikiforov, Michael Yu; Klochkov, Vladimir V; Georgi, Nikolaj

2014-02-01

394

Monte Carlo Calculations of Selected Dose Components in a Head Model for Boron Neutron Capture Therapy  

NASA Astrophysics Data System (ADS)

Boron Neutron Capture Therapy is a very promising form of cancer therapy, consisting in irradiating a stable isotope of boron (10B) concentrated in tumor cells with a low energy neutron beam. This technique makes it possible to destroy tumor cells, leaving healthy tissues practically unaffected. In order to carry out the therapy in the proper way, the proper range of the neutron beam energy has to be chosen. In this paper we present the results of the calculations, using the MCNP code, aiming at studying the energetic dependence of the absorbed dose from the neutron capture reaction on boron (the therapeutic dose), and hydrogen and nitrogen (the injuring dose).

Tymi?ska, Katarzyna

2007-01-01

395

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

NASA Astrophysics Data System (ADS)

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

Norwood, Zack; Kammen, Daniel

2012-12-01

396

Elementary Reactions of Boron Atoms with HydrocarbonssToward the Formation of Organo-Boron Compounds  

E-print Network

Boron Reactions 5112 2.3.1. Crossed Beam Machines with a Rotating QMS Detector 5113 2.3.2. Crossed BeamElementary Reactions of Boron Atoms with HydrocarbonssToward the Formation of Organo-Boron 96822 Received December 16, 2009 Contents 1. Introduction 5107 1.1. Organo-Boron Molecules in Combustion

Kaiser, Ralf I.

397

40 CFR Table F-4 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution  

Code of Federal Regulations, 2012 CFR

...Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution...of Class II Equivalent Methods for PM2.5 Pt. 53, Subpt. F, Table F-4...Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol...

2012-07-01

398

40 CFR Table F-4 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution  

Code of Federal Regulations, 2010 CFR

...Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution...of Class II Equivalent Methods for PM2.5 Pt. 53, Subpt. F, Table F-4...Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol...

2010-07-01

399

40 CFR Table F-6 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size Distribution  

Code of Federal Regulations, 2011 CFR

...Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size Distribution...of Class II Equivalent Methods for PM2.5 Pt. 53, Subpt. F, Table F-6...Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size...

2011-07-01

400

40 CFR Table F-6 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size Distribution  

Code of Federal Regulations, 2010 CFR

...Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size Distribution...of Class II Equivalent Methods for PM2.5 Pt. 53, Subpt. F, Table F-6...Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size...

2010-07-01

401

40 CFR Table F-4 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution  

Code of Federal Regulations, 2011 CFR

...Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol Size Distribution...of Class II Equivalent Methods for PM2.5 Pt. 53, Subpt. F, Table F-4...Estimated Mass Concentration Measurement of PM2.5 for Idealized Coarse Aerosol...

2011-07-01

402

40 CFR Table F-6 to Subpart F of... - Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size Distribution  

Code of Federal Regulations, 2012 CFR

...Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size Distribution...of Class II Equivalent Methods for PM2.5 Pt. 53, Subpt. F, Table F-6...Estimated Mass Concentration Measurement of PM2.5 for Idealized Fine Aerosol Size...

2012-07-01

403

Coprecipitation and isotopic fractionation of boron in modern biogenic carbonates  

SciTech Connect

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

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

1991-10-01

404

A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH.  

PubMed

Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka=3582.88M(-1)) and selectivity for fructose over glucose at pH=7.4. The sensor 1 showed a linear response toward d-fructose in the concentrations ranging from 2.5×10(-5) to 4×10(-4)molL(-1) with the detection limit of 1.3×10(-5)molL(-1). PMID:25748592

Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona; Eslami, Abbas; Emami, Saeed

2015-06-01

405

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

406

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

NASA Astrophysics Data System (ADS)

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

Costescu, Corneliu I.; Heuser, Brent J.

2000-04-01

407

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

408

[Mercury concentration and its distribution in Nycticorax nycticorax and Chinese Ardeola bacchus fledglings at Huangpu District of Guangzhou City, China].  

PubMed

In this study, live fledglings of Nycticorax nycticorax and Ardeola bacchus at the Huangpu District of Guangzhou City were collected, and their primary feather, breast feather, tail feather, liver, chest muscle and egg shell were sampled for mercury determination. The results showed that these two heron species had a very similar distribution pattern of mercury concentration in their tissues and organs, i. e., tail feather > breast and primary feather > liver > chest muscle > egg shell. Ardeola bacchus had higher levels of mercury in all its tissues than Nycticorax nycticorax. There were significant interspecific differences in mercury level for breast feather and primary feather. Because the collection of breast feather is easier and not harmful to birds, it is better to use it rather than primary or tail feather to monitor environmental pollution. The mercury level in breast feather was ten times higher than that in liver, lower than that in tail feather, but not significantly different to that in primary feather. The mercury concentrations in the tissues of Nycticorax nycticorax and Ardeola bacchus from Huangpu District of Guangzhou were similar to those from the suburbs of Chengdu, Sichuan Province, but lower than those from Taihu Lake, Jiangsu Province and higher than those from Hong Kong. PMID:15852945

Zou, Fasheng; Yang, Qiongfang; Li, Yanhong; Cui, Kunyan

2005-02-01

409

Modelling and experimental analysis of the angular distribution of the emitted light from the edge of luminescent solar concentrators  

NASA Astrophysics Data System (ADS)

Luminescent solar concentrators (LSCs) have the potential to provide cheap solar electricity by significantly reducing the solar cell area. However, these devices are still at the research level and several aspects of their behaviour need investigation in order to improve efficiencies. Understanding how light is absorbed/emitted and concentrated to the edge of LSCs is required to design a high efficiency device as well as identifying and overcoming the various losses present. One strategy for investigating the photon absorption and transport in LSCs as well as pinpointing the sources of losses in these devices is to look at the luminescence escaping the LSC as a function of angle. This paper presents a new model that reveals the main features of the angular distribution of light escaping a LSC edge. We compare this model with experimental measurements and provide an assessment of non-ideal losses and identify which emission angles are affected most by these losses. We investigated experimentally the effects of the absorption profile of the chromophores and re-absorption on the photon flux travelling at different angles. The effect of back surface reflectors, commonly used to 'recycle lost photons', on the edge emission of LSCs has also been investigated in this work.

Parel, Thomas S.; Pistolas, Christos; Danos, Lefteris; Markvart, Tomas

2015-04-01

410

Synthesis and photocurrent of amorphous boron nanowires  

NASA Astrophysics Data System (ADS)

Although theoretically feasible, synthesis of boron nanostructures is challenging due to the highly reactive nature, high melting and boiling points of boron. We have developed a thermal vapor transfer approach to synthesizing amorphous boron nanowire using a solid boron source. The amorphous nature and chemical composition of boron nanowires were characterized by high resolution transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. Optical properties and photoconduction of boron nanowires have not yet been reported. In our investigation, the amorphous boron nanowire showed much better optical and electrical properties than previously reported photo-response of crystalline boron nanobelts. When excited by a blue LED, the photo/dark current ratio (I/I0) is 1.5 and time constants in the order of tens of seconds. I/I0 is 1.17 using a green light.

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

2014-08-01

411

Boronated porhyrins and methods for their use  

DOEpatents

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

Miura, Michiko (Hampton Bays, NY); Shelnutt, John A. (Tijeras, NM); Slatkin, Daniel N. (Southhold, NY)

1999-03-02

412

Boronated porhyrins and methods for their use  

DOEpatents

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

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

1999-03-02

413

Decreasing the leachibility of boron wood preservatives  

E-print Network

The use of boron in wood preservatives has been growing since the 1930s, primarily in various boric acid/borax mixtures. Boron preservatives have several advantages for application as wood preservatives including a broad spectrum of activity...

Gezer, Engin Derya

1996-01-01

414

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

SciTech Connect

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

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

2012-01-04

415

An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water  

Microsoft Academic Search

Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally.\\u000a The results show the clear positive relationships between boron concentration and ?11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic\\u000a fractionation between inorganic calcite and seawater\\/saline water with pH are inconsistent

Yingkai Xiao; Shizhen Li; Haizhen Wei; Aide Sun; Weijian Zhou; Weiguo Liu

2006-01-01

416

Diffusion profiles of boron implanted into plasma-etched silicon surfaces  

Microsoft Academic Search

The diffusion of low-dose boron implanted into plasma-etched silicon surfaces is studied. The thermally grown oxide film on the silicon surface was plasma-etched in a CHF3\\/CO2 plasma. The samples were successively implanted and activated with boron and arsenic to form n+-p-n junctions to obtain a range of surface doping profiles and junction depths. The chemical and electrically active dopant concentrations

Krishna Shenai

1992-01-01

417

Infrared reflectivity and transmissivity of boron-implanted, laser-annealed silicon  

SciTech Connect

Analysis of the infrared reflectance and transmittance of boron-implanted, laser-annealed silicon shows that the Drude theory of free hole scattering provides a good description of the optical properties of these materials up to the highest doping levels obtainable. It was found that (1) the relaxation time (approx.7 x 10/sup -15/ s) was independent of the implant dose, and (2) the boron concentration affecting the optical properties varies essentially linearly with implant dose.

Engstrom, H.

1980-10-01

418

Experimental study of the Zeeman splitting of boron levels in silicon  

Microsoft Academic Search

The Zeeman effect of the first four photoexcitation lines of boron in silicon has been investigated in crystals with low boron concentration (~1014 atoms\\/cm3) and for magnetic fields up to 64 kG with E-->?B--> and E-->||B-->. As many as eleven discrete components have been resolved for line 1 for B-->||. No quadratic shift is observed for lines 1 and 2,

F. Merlet; B. Pajot; Ph. Arcas; A. M. Jean-Louis

1975-01-01

419

Damage removal and boron diffusion during solid phase epitaxial growth of SiGe alloy layers  

NASA Astrophysics Data System (ADS)

SiGe/Si heterostructures have been fabricated using germanium ion implantation into silicon and subsequent solid phase epitaxy (SPE) growth. The damage removal and boron diffusion in the SiGe/Si heterostructures formed by high-dose Ge + preamorphized and BF 2+ implanted Si(0 0 1) during SPE growth have been investigated by double-crystal X-ray diffraction (DCXRD) and secondary ion mass spectrometry (SIMS). The results show that annealing at 600°C for 60 min can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. Most damage induced by Ge + and BF 2+ ion implantation have been removed after annealing at 950°C for 60 min and accompanied by Ge diffusion, a boron diffusion has taken place. When annealing temperature rose to 1050°C, Ge diffusion has been slight while B diffusion has been deeper into the Si substrate with a very good distribution. The X-ray diffraction (0 0 4) rocking curves from the samples annealed at 1050°C for 60 min display two SiGe peaks, which may be related to the B and Ge concentration profiles.

Zou, L.-F.; Acosta-Ortiz, S. E.; Zou, LuXin; Luna, R. E.; Perez-Herr