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1

Conceptual study of a compact accelerator-driven neutron source for radioisotope production, boron neutron capture therapy and fast neutron therapy  

Microsoft Academic Search

The feasibility of a compact accelerator-driven device for the generation of neutron spectra suitable for isotope production by neutron capture, boron neutron capture therapy and fast neutron therapy, is analyzed by Monte Carlo simulations. The device is essentially an extension of the activator proposed by Rubbia [CERN\\/LHC\\/97-04(EET)], in which fast neutrons are diffused and moderated within a properly sized lead

M. Angelone; S. Atzeni; S. Rollet

2002-01-01

2

Linear accelerator for radioisotope production  

SciTech Connect

A 200- to 500-..mu..A source of 70- to 90-MeV protons would be a valuable asset to the nuclear medicine program. A linear accelerator (linac) can achieve this performance, and it can be extended to even higher energies and currents. Variable energy and current options are available. A 70-MeV linac is described, based on recent innovations in linear accelerator technology; it would be 27.3 m long and cost approx. $6 million. By operating the radio-frequency (rf) power system at a level necessary to produce a 500-..mu..A beam current, the cost of power deposited in the radioisotope-production target is comparable with existing cyclotrons. If the rf-power system is operated at full power, the same accelerator is capable of producing an 1140-..mu..A beam, and the cost per beam watt on the target is less than half that of comparable cyclotrons.

Hansborough, L.D.; Hamm, R.W.; Stovall, J.E.

1982-02-01

3

Radioisotope Production for Medical and Physics Applications  

NASA Astrophysics Data System (ADS)

Radioisotopes are critical to the science and technology base of the US. Discoveries and applications made as a result of the availability of radioisotopes span widely from medicine, biology, physics, chemistry and homeland security. The clinical use of radioisotopes for medical diagnosis is the largest sector of use, with about 16 million procedures a year in the US. The use of ^99Mo/^99mTc generator and ^18F make up the majority, but ^201Tl, ^123I, ^111In, and ^67Ga are also used routinely to perform imaging of organ function. Application of radioisotopes for therapy is dominated by use of ^131I for thyroid malignancies, ^90Y for some solid tumors, and ^89Sr for bone cancer, but production of several more exotic species such as ^225Ac and ^211At are of significant current research interest. In physics ^225Ra is of interest for CP violation studies, and the actinides ^242Am, ^249Bk, and ^254Es are needed as targets for experiments to create superheavy elements. Large amounts of ^252Cf are needed as a fission source for the CARIBU experiment at ANL. The process of radioisotope production is multidisciplinary. Nuclear physics input based on nuclear reaction excitation function data is needed to choose an optimum target/projectile in order to maximize desired isotope production and minimize unwanted byproducts. Mechanical engineering is needed to address issues of target heating, induced mechanical stress and material compatibility of target and claddings. Radiochemists are involved as well since chemical separation to purify the desired final radioisotope product from the bulk target and impurities is also usually necessary. Most neutron rich species are produced at a few government and university reactors. Other radioisotopes are produced in cyclotrons in the commercial sector, university/hospital based facilities, and larger devices at the DOE labs. The landscape of US facilities, the techniques involved, and current supply challenges will be reviewed.

Mausner, Leonard

2012-10-01

4

Alternate Applications of Fusion - Production of Radioisotopes  

SciTech Connect

A major effort to find near-term, non-electric applications of fusion energy has shown that the production of radioisotopes is attractive. The use of the D{sup 3}He fusion reaction to produce Positron Emission Tomography (PET) isotopes is described. An Inertial Electrostatic Confinement (IEC) device is particularly well suited to produce low levels of high-energy (14.7 MeV) protons, which in turn, can produce short-lived PET isotopes. The IEC device at University of Wisconsin has been modified to investigate the potential of this process to be commercially attractive.

Kulcinski, G.L.; Weidner, J.; Cipiti, B.; Ashley, R.P.; Santarius, J.F.; Murali, S.K.; Piefer, G.; Radel, R. [University of Wisconsin-Madison (United States)

2003-09-15

5

Production of medical radioisotopes with linear accelerators.  

PubMed

In this study, we discuss producing radioisotopes using linear electron accelerators and address production and separation issues of photoneutron (?,n) and photoproton (?,p) reactions. While (?,n) reactions typically result in greater yields, separating product nuclides from the target is challenging since the chemical properties of both are the same. Yields of (?,p) reactions are typically lower than (?,n) ones, however they have the advantage that target and product nuclides belong to different chemical species so their separation is often not such an intricate problem. In this paper we consider two examples, (100)Mo(?,n)(99)Mo and (68)Zn(?,p)(67)Cu, of photonuclear reactions. Monte-Carlo simulations of the yields are benchmarked with experimental data obtained at the Idaho Accelerator Center using a 44MeV linear electron accelerator. We propose using a kinematic recoil method for photoneutron production. This technique requires (100)Mo target material to be in the form of nanoparticles coated with a catcher material. During irradiation, (99)Mo atoms recoil and get trapped in the coating layer. After irradiation, the coating is dissolved and (99)Mo is collected. At the same time, (100)Mo nanoparticles can be reused. For the photoproduction method, (67)Cu can be separated from the target nuclides, (68)Zn, using standard exchange chromatography methods. Monte-Carlo simulations were performed and the (99)Mo activity was predicted to be about 7MBq/(g(?)kW(?)h) while (67)Cu activity was predicted to be about 1MBq/(g(?)kW(?)h). Experimental data confirm the predicted activity for both cases which proves that photonuclear reactions can be used to produce radioisotopes. Lists of medical isotopes which might be obtained using photonuclear reactions have been compiled and are included as well. PMID:24374071

Starovoitova, Valeriia N; Tchelidze, Lali; Wells, Douglas P

2014-02-01

6

Development of Water Target for Radioisotope Production  

NASA Astrophysics Data System (ADS)

Ongoing studies of plant physiology at TUNL require a supply of nitrogen-13 for use as a radiotracer. Production of nitrogen-13 using a water target and a proton beam follows the nuclear reaction 16-O(p,a)13-N. Unfortunately the irradiation of trace amounts of oxygen-18 within a natural water target produces fluorine-18 by the reaction 18-O(p, n)18-F. The presence of this second radioisotope reduces the efficacy of nitrogen-13 as a radiotracer. Designing a natural water target for nitrogen-13 production at TUNL required the design of several new systems to address the problems inherent in nitrogen-13 production. A heat exchanger cools the target water after irradiation within the target cell. The resulting improved thermal regulation of the target water prevents the system from overheating and minimizes the effect of the cavitations occurring within the target. Alumina pellets within a scrubbing unit remove the fluorine-18 contamination from the irradiated water. The modular design of the water target apparatus makes the system highly adaptable, allowing for easy reuse and adaptation of the different components into future projects. The newly designed and constructed water target should meet the current and future needs of TUNL researchers in the production of nitrogen-13.

Tripp, Nathan

2011-10-01

7

Safety evaluation for regulatory management of Australian radioisotope production facilities.  

PubMed

This paper describes the approach of Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) in the regulatory management of Radioisotope Production facilities in Australia. ARPANSA is the regulatory authority for commonwealth entities operating nuclear installations including Radioisotope Production facilities. In assessing the application for operating nuclear installations the ARPANSA assessors prepare a Safety Evaluation Report, which is a recommendation to the Chief Executive Officer (CEO) of ARPANSA whether to issue a licence to site, construct, operate and decommission facilities. In particular, the CEO must take into account international best practice in radiation protection and nuclear safety when making licence decisions. PMID:19285422

Sarkar, S

2009-01-01

8

Radioisotope production and management at Oak Ridge National Laboratory  

Microsoft Academic Search

The production of radioisotopes has been one of the basic activities at Oak Ridge since the end of World War II. The importance of this work was best described by Alvin Weinberg, former Laboratory Director, when he wrote ``... If God has a golden book and writes down what it is that Oak Ridge National Laboratory did that had the

E. D. Collins; W. S. Aaron; C. W. Alexander; J. E. Bigelow; J. T. Parks; J. G. Tracy; R. M. Wham

1994-01-01

9

Production capabilities in US nuclear reactors for medical radioisotopes  

SciTech Connect

The availability of reactor-produced radioisotopes in the United States for use in medical research and nuclear medicine has traditionally depended on facilities which are an integral part of the US national laboratories and a few reactors at universities. One exception is the reactor in Sterling Forest, New York, originally operated as part of the Cintichem (Union Carbide) system, which is currently in the process of permanent shutdown. Since there are no industry-run reactors in the US, the national laboratories and universities thus play a critical role in providing reactor-produced radioisotopes for medical research and clinical use. The goal of this survey is to provide a comprehensive summary of these production capabilities. With the temporary shutdown of the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) in November 1986, the radioisotopes required for DOE-supported radionuclide generators were made available at the Brookhaven National Laboratory (BNL) High Flux Beam Reactor (HFBR). In March 1988, however, the HFBR was temporarily shut down which forced investigators to look at other reactors for production of the radioisotopes. During this period the Missouri University Research Reactor (MURR) played an important role in providing these services. The HFIR resumed routine operation in July 1990 at 85 MW power, and the HFBR resumed operation in June 1991, at 30 MW power. At the time of the HFBR shutdown, there was no available comprehensive overview which could provide information on status of the reactors operating in the US and their capabilities for radioisotope production. The obvious need for a useful overview was thus the impetus for preparing this survey, which would provide an up-to-date summary of those reactors available in the US at both the DOE-funded national laboratories and at US universities where service irradiations are currently or expected to be conducted.

Mirzadeh, S.; Callahan, A.P.; Knapp, F.F. Jr. [Oak Ridge National Lab., TN (United States); Schenter, R.E. [Westinghouse Hanford Co., Richland, WA (United States)

1992-11-01

10

Radioisotope production at ORNL - past, present, and future  

SciTech Connect

A wide variety of radioisotopes have been and are being produced at Oak Ridge National Laboratory (ORNL). Facilities previously used have included the Bulk Shielding (BSR), Oak Ridge Research (ORR), and High Flux Isotope (HFIR) reactors and the hot cells located in the Fission Products Development Laboratory (FPDL), the Isotopes Circle, and hot cell facilities formerly called the Transuranium Processing Plant (TRU or TPP) and the Thorium-Uranium Recycle Facility (TURF). The HFIR and the TPP were built as part of the national heavy element production program, sponsored by the DOE Office of Energy Research. This program has been and continues to be the major isotope program at ORNL. The production of Cf-252 for uses in portable neutron sources is an important secondary project. A wide variety of other radioisotopes is planned using a new 21st century reactor, called the Advanced Neutron Source, and upgraded hot cell processing facilities located in the Melton Valley area of ORNL.

Collins, E.D.; Alexander, C.W.; Bigelow, J.E.; Ottinger, C.L. [Oak Ridge National Laboratory, TN (United States)

1993-12-31

11

Radio-isotope production using laser Wakefield accelerators  

SciTech Connect

A 10 Hz, 10 TW solid state laser system has been used to produce electron beams suitable for radio-isotope production. The laser beam was focused using a 30 cm focal length f/6 off-axis parabola on a gas plume produced by a high pressure pulsed gas jet. Electrons were trapped and accelerated by high gradient wakefields excited in the ionized gas through the self-modulated laser wakefield instability. The electron beam was measured to contain excesses of 5 nC/bunch. A composite Pb/Cu target was used to convert the electron beam into gamma rays which subsequently produced radio-isotopes through (gamma, n) reactions. Isotope identification through gamma-ray spectroscopy and half-life time measurements demonstrated that Cu{sup 61} was produced which indicates that 20-25 MeV gamma rays were produced, and hence electrons with energies greater than 25-30 MeV. The production of high energy electrons was independently confirmed using a bending magnet spectrometer. The measured spectra had an exponential distribution with a 3 MeV width. The amount of activation was on the order of 2.5 uCi after 3 hours of operation at 1 Hz. Future experiments will aim at increasing this yield by post-accelerating the electron beam using a channel guided laser wakefield accelerator.

Leemans, W.P.; Rodgers, D.; Catravas, P.E.; Geddes, C.G.R.; Fubiani, G.; Toth, C.; Esarey, E.; Shadwick, B.A.; Donahue, R.; Smith, A.; Reitsma, A.

2001-07-27

12

Target optimization for the photonuclear production of radioisotopes.  

PubMed

In this paper we discuss the optimum shape of a target for photonuclear production of radioisotopes using an electron linear accelerator. Different target geometries such as right cylinder, conical frustum, Gaussian volume of revolution and semi-ellipsoid have been considered for the production of (67)Cu via (68)Zn(?,p)(67)Cu photonuclear reaction. The specific activity (SA) of (67)Cu was simulated for each target shape. Optimum ratio of radius to height for cylindrical targets was found to be between 0.2 and 0.25 for target masses ranging from 20g to 100g. It was shown that while some unconventional target shapes, such as semi-elliptical volume of revolution, result in slightly higher specific activities than cylindrical targets, the advantage is not significant and is outweighed by the complexity of the target production and handling. Power deposition into the target was modeled and the trade-off between the maximization of (67)Cu yield and the minimization of target heating has been discussed. The (67)Cu case can easily be extended for production of many other isotopes. PMID:25497325

Howard, Sean; Starovoitova, Valeriia N

2015-02-01

13

Novel production techniques of radioisotopes using electron accelerators  

NASA Astrophysics Data System (ADS)

Non-traditional radioisotope production techniques using a compact, high power linear electron accelerator have been demonstrated and characterized for the production of 18F, 47Sc, 147 Pm, and 99mTc from a variety of target candidates. These isotopes are used extensively in the medical field as diagnostic and therapy radioisotopes, as well as the space industry as RTG's. Primary focus was placed on 99mTc as it constitutes approximately 80% of all diagnostic procedures in the medical community that use radioactive tracers. It was also the prime focus due to recent events at the Chalk River nuclear reactor, which caused global shortages of this isotope a few years ago. A Varian K15 LINAC was first used to show proof of principle in Las Vegas. Various samples were then taken to the Idaho Accelerator Center where they were activated using an electron LINAC capable of electron energies from 4 to 25 MeV at a beam power of approximately 1 kW. Production rates, cross sections, and viability studies were then performed and conducted to assess the effectiveness of the candidate target and the maximum production rate for each radioisotope. Production rates for 18F from lithium fluoride salts were shown to be ideal at 21MeV, namely 1.7 Ci per kg of LiF salt, per kW of beam current, per 10 hour irradiation time. As the typical hospital consumption of 18F is around 500 mCi per day, it is clear that a large amount of 18F can be made from a small (300 gram) sample of LiF salt. However, since there is no current separation process for 18F from 19F, the viability of this technique is limited until a separations technique is developed. Furthermore, the calculated cross section for this reaction is in good agreement with literature, which supports the techniques for the isotopes mentioned below. Production rates for 47Sc from vanadium oxide targets were shown to be a maximum at 25 MeV with a production rate of 2 mCi per day, assuming a 2 kW beam and a 10 kg target. While this production rate would be able to support a research environment where a single patient per day would be addressed, it is unlikely that this method would produce enough material to support a large hospital. The production of 147Pm from europium oxide targets showed that due to the large spin state differences between 151Eu and 147Pm, a negligible amount of 147Pm can be created using the (gamma,alpha) process. The minimum detectable limit for these experiments, given this specific isotope, was 10 nCi. The (gamma, gamma') reaction was studied on 99mTc to determine the production rates and cross sections for this reaction. It was found that the average production rate between 12 and 25 MeV was approximately 3 uCi/(kg*kW). Given that a single patient dose of 99mTc is approximately 20 mCi, we find that we need many kilograms of technetium metal. This would produce toxic levels of technetium in the patient; therefore this method is not likely viable. It was also found, however, that the (n,n') reaction may play a significant role in the activation from ground state technetium to the metastable state. Finally, the (gamma, alpha) reaction that will produce 99m Tc from rhodium oxide targets was quantified from energies of 12 to 25 MeV. The production rate was found to be 64 and 113 mCi/(kg*kW*day) for 19 and 25 MeV, respectively. Given a 2 kW beam and a 2 kg target, we find this technique to be a feasible method to create 99mTc in a local setting using a LINAC. By using a fast separations technique, such as selective volatilization, a process in which technetium oxide is volatilized off of rhodium oxide in a carrier gas could provide a turn-key solution for entities looking to create this radioisotope on site. A cost-benefit analysis was performed and it was found that a system such as this could produce over $1M in revenue per year given a standard hospital usage of 40 patient doses per day.

Lowe, Daniel Robert

14

Apparatus for the production of boron nitride nanotubes  

SciTech Connect

An apparatus for the large scale production of boron nitride nanotubes comprising; a pressure chamber containing; a continuously fed boron containing target; a source of thermal energy preferably a focused laser beam; a cooled condenser; a source of pressurized nitrogen gas; and a mechanism for extracting boron nitride nanotubes that are condensed on or in the area of the cooled condenser from the pressure chamber.

Smith, Michael W; Jordan, Kevin

2014-06-17

15

Boron modified molybdenum silicide and products  

DOEpatents

A boron-modified molybdenum silicide material is disclosed having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo{sub 5}Si{sub 3} phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi{sub 2} heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo{sub 5}Si{sub 3} for structural integrity. 7 figs.

Meyer, M.K.; Akinc, M.

1999-02-02

16

Boron modified molybdenum silicide and products  

DOEpatents

A boron-modified molybdenum silicide material having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo.sub.5 Si.sub.3 phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi.sub.2 heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo.sub.5 Si.sub.3 for structural integrity.

Meyer, Mitchell K. (Idaho Falls, ID); Akinc, Mufit (Ames, IA)

1999-02-02

17

BORON  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

18

The plasma separation process as a pre-cursor for large scale radioisotope production  

NASA Astrophysics Data System (ADS)

Radioisotope production generally employs either accelerators or reactors to convert stable (usually enriched) isotopes into the desired product species. Radioisotopes have applications in industry, environmental sciences, and most significantly in medicine. The production of many potentially useful radioisotopes is significantly hindered by the lack of availability or by the high cost of key enriched stable isotopes. To try and meet this demand, certain niche enrichment processes have been developed and commercialized. Calutrons, centrifuges, and laser separation processes are some of the devices and techniques being employed to produce large quantities of selective enriched stable isotopes. Nevertheless, the list of enriched stable isotopes in sufficient quantities remains rather limited and this continues to restrict the availability of many radioisotopes that otherwise could have a significant impact on society. The Plasma Separation Process is a newly available commercial technique for producing large quantities of a wide range of enriched isotopes and thereby holds promise of being able to open the door to producing new and exciting applications of radioisotopes in the future.

Stevenson, Nigel R.

2001-07-01

19

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...

20

Production and supply of radioisotopes with high-energy particle accelerators current status and future directions  

SciTech Connect

Although the production of radioisotopes in reactors or in low to medium energy cyclotrons appears to be relatively well established, especially for those isotopes that are routinely used and have a commercial market, certain isotopes can either be made only in high-energy particle accelerators or their production is more cost effective when made this way. These facilities are extremely expensive to build and operate, and isotope production is, in general, either not cost-effective or is in conflict with their primary mandate or missions which involve physics research. Isotope production using high-energy accelerators in the US, therefore, has been only an intermittent and parasitic activity. However, since a number of isotopes produced at higher energies are emerging as being potentially useful for medical and other applications, there is a renewed concern about their availability in a continuous and reliable fashion. In the US, in particular, the various aspects of the prediction and availability of radioisotopes from high-energy accelerators are presently undergoing a detailed scrutiny and review by various scientific and professional organizations as well as the Government. A number of new factors has complicated the supply/demand equation. These include considerations of cost versus needs, reliability factors, mission orientation, research and educational components, and commercial viability. This paper will focus on the present status and projected needs of radioisotope production with high-energy accelerators in the US, and will compare and examine the existing infrastructure in other countries for this purpose.

Srivastava, S.C.; Mausner, L.F.

1994-03-01

21

A prototype on-line work procedure system for radioisotope thermoelectric generator production  

SciTech Connect

An on-line system to manage work procedures is being developed to support radioisotope thermoelectric generator (RTG) assembly and testing in a new production facility. This system implements production work procedures as interactive electronic documents executed at the work site with no intermediate printed form. It provides good control of the creation and application of work procedures and provides active assistance to the worker in performing them and in documenting the results. An extensive prototype of this system is being evaluated to ensure that it will have all the necessary features and that it will fit the user's needs and expectations. This effort has involved the Radioisotope Power Systems Facility (RPSF) operations organization and technology transfer between Westinghouse Hanford Company (Westinghouse Hanford) and EG G Mound Applied Technologies Inc. (Mound) at the US Department of Energy (DOE) Mound Site. 1 ref.

Kiebel, G.R.

1991-09-01

22

Student research with 400keV beams: {sup 13}N radioisotope production target development  

SciTech Connect

The AN400 Van de Graaff accelerator at the Minnesota State University, Mankato, Applied Nuclear Science Lab has demonstrated utility as an accessible and versatile platform for student research. Despite the limits of low energy, the research team successfully developed projects with applications to the wider radioisotope production community. A target system has been developed for producing and extracting {sup 13}N by the {sup 12}C(d,n){sup 13}N reaction below 400keV. The system is both reusable and robust, with future applications to higher energy machines producing this important radioisotope for physiological imaging studies with Positron Emission Tomography. Up to 36({+-}1)% of the {sup 13}N was extracted from the graphite matrix when 35 A current was externally applied to the graphite target while simultaneously flushing the target chamber with CO{sub 2} gas.

Fru, L. Che; Clymer, J.; Compton, N.; Cotter, J.; Dam, H.; Lesko, Z.; Pautzke, J.; Prokop, C.; Swanson, L.; Roberts, A. D. [Department of Physics and Astronomy, Minnesota State University, Trafton Science Center N141, Mankato MN 56001 (United States)

2013-04-19

23

Production of defects in hexagonal boron nitride monolayer under ion irradiation O. Lehtinen a,  

E-print Network

Production of defects in hexagonal boron nitride monolayer under ion irradiation O. Lehtinen a, , E: Hexagonal boron nitride monolayer Ion irradiation Defect a b s t r a c t Atomistic computer simulations based on analytical potentials are employed to investigate the response of a hexagonal boron nitride

Krasheninnikov, Arkady V.

24

Conceptual design of a new homogeneous reactor for medical radioisotope Mo-99/Tc-99m production  

NASA Astrophysics Data System (ADS)

To partly solve the global and regional shortages of Mo-99 supply, a conceptual design of a nitrate-fuel-solution based homogeneous reactor dedicated for Mo-99/Tc-99m medical radioisotope production is proposed. The modified LEU Cintichem process for Mo-99 extraction which has been licensed and demonstrated commercially for decades by BATAN is taken into account as a key design consideration. The design characteristics and main parameters are identified and the advantageous aspects are shown by comparing with the BATAN's existing Mo-99 supply chain which uses a heterogeneous reactor (RSG GAS multipurpose reactor).

Liem, Peng Hong; Tran, Hoai Nam; Sembiring, Tagor Malem; Arbie, Bakri

2014-09-01

25

Production of Beryllium and Boron by Spallation in Supernova Ejecta  

E-print Network

The abundances of beryllium and boron have been measured in halo stars of metallicities as low as [Fe/H] =-3. The observations show that the ratios Be/Fe and B/Fe are independent of metallicity and approximately equal to their solar values over the entire range of observed metallicity. These observations are in contradiction with the predictions of simple models of beryllium and boron production by spallation in the interstellar medium of a well mixed galaxy. We propose that beryllium and boron are produced by spallation in the ejecta of type II supernovae. In our picture, protons and alpha particles are accelerated early in the supernova event and irradiate the heavy elements in the ejecta long before the ejecta mixes with the interstellar medium. We follow the propagation of the accelerated particles with a Monte-Carlo code and find that the energy per spallation reaction is about 5 GeV for a variety of initial particle spectra and ejecta compositions. Reproducing the observed Be/Fe and B/Fe ratios requires roughly 3 times 10^{47} ergs of accelerated protons and alphas. This is much less than the 10^{51} ergs available in a supernova explosion.

Deepa Majmudar; James H. Applegate

1997-08-01

26

Integrated rig for the production of boron nitride nanotubes via the pressurized vapor-condenser method  

DOEpatents

An integrated production apparatus for production of boron nitride nanotubes via the pressure vapor-condenser method. The apparatus comprises: a pressurized reaction chamber containing a continuously fed boron containing target having a boron target tip, a source of pressurized nitrogen and a moving belt condenser apparatus; a hutch chamber proximate the pressurized reaction chamber containing a target feed system and a laser beam and optics.

Smith, Michael W; Jordan, Kevin C

2014-03-25

27

Proton linac for hospital-based fast neutron therapy and radioisotope production  

SciTech Connect

Recent developments in linac technology have led to the design of a hospital-based proton linac for fast neutron therapy. The 180 microamp average current allows beam to be diverted for radioisotope production during treatments while maintaining an acceptable dose rate. During dedicated operation, dose rates greater than 280 neutron rads per minute are achievable at depth, DMAX = 1.6 cm with source to axis distance, SAD = 190 cm. Maximum machine energy is 70 MeV and several intermediate energies are available for optimizing production of isotopes for Positron Emission Tomography and other medical applications. The linac can be used to produce a horizontal or a gantry can be added to the downstream end of the linac for conventional patient positioning. The 70 MeV protons can also be used for proton therapy for ocular melanomas. 17 refs., 1 fig., 1 tab.

Lennox, A.J.; Hendrickson, F.R.; Swenson, D.A.; Winje, R.A.; Young, D.E. (Fermi National Accelerator Lab., Batavia, IL (USA); Rush Univ., Chicago, IL (USA); Science Applications International Corp., Princeton, NJ (USA); Fermi National Accelerator Lab., Batavia, IL (USA))

1989-09-01

28

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

PubMed Central

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

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

1999-01-01

29

Radio-isotope production scale-up at the University of Wisconsin  

SciTech Connect

Our intent has been to scale up our production capacity for a subset of the NSAC-I list of radioisotopes in jeopardy, so as to make a significant impact on the projected national needs for Cu-64, Zr-89, Y-86, Ga-66, Br-76, I-124 and other radioisotopes that offer promise as PET synthons. The work-flow and milestones in this project have been compressed into a single year (Aug 1, 2012- July 31, 2013). The grant budget was virtually dominated by the purchase of a pair of dual-mini-cells that have made the scale-up possible, now permitting the Curie-level processing of Cu-64 and Zr-89 with greatly reduced radiation exposure. Mile stones: 1. We doubled our production of Cu-64 and Zr-89 during the grant period, both for local use and out-bound distribution to ? 30 labs nationwide. This involved the dove-tailing of beam schedules of both our PETtrace and legacy RDS cyclotron. 2. Implemented improved chemical separation of Zr-89, Ga-66, Y-86 and Sc-44, with remote, semi-automated dissolution, trap-and-release separation under LabView control in the two dual-mini-cells provided by this DOE grant. A key advance was to fit the chemical stream with miniature radiation detectors to confirm the transfer operations. 3. Implemented improved shipping of radioisotopes (Cu-64, Zr-89, Tc-95m, and Ho-163) with approved DOT 7A boxes, with a much-improved FedEx shipping success compared to our previous steel drums. 4. Implemented broad range quantitative trace metal analysis, employing a new microwave plasma atomic emission spectrometer (Agilent 4200) capable of ppb sensitivity across the periodic table. This new instrument will prove essential in bringing our radiometals into FDA compliance needing CoA’s for translational research in clinical trials. 5. Expanded our capabilities in target fabrication, with the purchase of a programmable 1600 oC inert gas tube furnace for the smelting of binary alloy target materials. A similar effort makes use of our RF induction furnace, allowing small scale metallurgy with greater control. This alloy feedstock was then used to electroplate cyclotron targets with elevated melting temperatures capable of withstanding higher beam currents. 6. Finished the beam-line developments needed for the irradiation of low-melting target materials (Se and Ga) now being used for the production of Br-76, and radioactive germanium (68, 69, 71Ge). Our planned development of I-124 production has been deferred, given the wide access from commercial suppliers. The passing of these milestones has been the subject of the previous quarterly reports. These signature accomplishments were made possible by the DOE support, and have strengthened the infrastructure at the University of Wisconsin, provided the training ground for a very talented graduate research assistant (Mr. Valdovinos) and more than doubled our out-shipments of Cu-64 and Zr-89.

Nickles, Robert Jerome [Univ of Wisconsin] [Univ of Wisconsin

2014-06-19

30

Development of a cryogenic gas target system for intense radioisotope beam production at CRIB  

NASA Astrophysics Data System (ADS)

A cryogenic gas target system was developed for the radioisotope (RI) beam production at CNS Radio Isotope Beam separator (CRIB). Hydrogen gas was cooled to 85-90 K using liquid nitrogen and used as a secondary beam production target having a thickness of 2.3 mg/cm2. An intense 7Be beam ( 2×108 particles per second) was successfully produced using this target. We observed a density-reduction effect at the gas target for high-current primary beams with about 7.5 W heat deposition. One main feature of the target system is forced circulation of the target gas. We have found that the circulation of the target gas at a rate of 55 standard liters per minute (slm) was effective in eliminating the density reduction. The extent to which the forced flow can prevent the density reduction had not been known well. In this work, the relation between the density reduction and the forced circulation rate was quantitatively studied.

Yamaguchi, H.; Wakabayashi, Y.; Amadio, G.; Hayakawa, S.; Fujikawa, H.; Kubono, S.; He, J. J.; Kim, A.; Binh, D. N.

2008-05-01

31

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

32

Production of Medical Radioisotopes with High Specific Activity in Photonuclear Reactions with $?$ Beams of High Intensity and Large Brilliance  

E-print Network

We study the production of radioisotopes for nuclear medicine in $(\\gamma,x{\\rm n}+y{\\rm p})$ photonuclear reactions or ($\\gamma,\\gamma'$) photoexcitation reactions with high flux [($10^{13}-10^{15}$)$\\gamma$/s], small diameter $\\sim (100 \\, \\mu$m$)^2$ and small band width ($\\Delta E/E \\approx 10^{-3}-10^{-4}$) $\\gamma$ beams produced by Compton back-scattering of laser light from relativistic brilliant electron beams. We compare them to (ion,$x$n$ + y$p) reactions with (ion=p,d,$\\alpha$) from particle accelerators like cyclotrons and (n,$\\gamma$) or (n,f) reactions from nuclear reactors. For photonuclear reactions with a narrow $\\gamma$ beam the energy deposition in the target can be managed by using a stack of thin target foils or wires, hence avoiding direct stopping of the Compton and pair electrons (positrons). $(\\gamma,\\gamma')$ isomer production via specially selected $\\gamma$ cascades allows to produce high specific activity in multiple excitations, where no back-pumping of the isomer to the ground state occurs. We discuss in detail many specific radioisotopes for diagnostics and therapy applications. Photonuclear reactions with $\\gamma$ beams allow to produce certain radioisotopes, e.g. $^{47}$Sc, $^{44}$Ti, $^{67}$Cu, $^{103}$Pd, $^{117m}$Sn, $^{169}$Er, $^{195m}$Pt or $^{225}$Ac, with higher specific activity and/or more economically than with classical methods. This will open the way for completely new clinical applications of radioisotopes. For example $^{195m}$Pt could be used to verify the patient's response to chemotherapy with platinum compounds before a complete treatment is performed. Also innovative isotopes like $^{47}$Sc, $^{67}$Cu and $^{225}$Ac could be produced for the first time in sufficient quantities for large-scale application in targeted radionuclide therapy.

D. Habs; U. Köster

2010-09-08

33

Production of medical radioisotopes in the ORNL High Flux Isotope Reactor (HFIR) for cancer treatment and arterial restenosis therapy after PTCA  

SciTech Connect

The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) represents an important resource for the production of a wide variety of medical radioisotopes. In addition to serving as a key production site for californium-252 and other transuranic elements, important examples of therapeutic radioisotopes which are currently routinely produced in the HFIR for distribution include dysprosium-166 (parent of holmium-166), rhenium-186, tin-117m and tungsten-188 (parent of rhenium-188). The nine hydraulic tube (HT) positions in the central high flux region permit the insertion and removal of targets at any time during the operating cycle and have traditionally represented a major site for production of medical radioisotopes. To increase the irradiation capabilities of the HFIR, special target holders have recently been designed and fabricated which will be installed in the six Peripheral Target Positions (PTP), which are also located in the high flux region. These positions are only accessible during reactor refueling and will be used for long-term irradiations, such as required for the production of tin-117m and tungsten-188. Each of the PTP tubes will be capable of housing a maximum of eight HT targets, thus increasing the total maximum number of HT targets from the current nine, to a total of 57. In this paper the therapeutic use of reactor-produced radioisotopes for bone pain palliation and vascular brachytherapy and the therapeutic medical radioisotope production capabilities of the ORNL HFIR are briefly discussed.

Knapp, F.F. Jr.; Beets, A.L.; Mirzadeh, S.; Alexander, C.W.; Hobbs, R.L.

1998-06-01

34

Production of medical radioisotopes in the ORNL high flux isotope reactor (HFIR) for cancer treatment and arterial restenosis therapy after PICA  

NASA Astrophysics Data System (ADS)

The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) represents an important resource for the production of a wide variety of medical radioisotopes. First beginning operation in 1965, the high thermal neutron flux (2.5×1015 neutrons/cm2/sec at 85 MW) and versatile target irradiation and handling facilities provide the opportunity for production of a wide variety of neutron-rich medical radioisotopes of current interest for therapy. In addition to serving as a key production site for californium-252 and other transuranic elements, important examples of therapeutic radioisotopes which are currently routinely produced in the HFIR for distribution include dysprosium-166 (parent of holmium-166), rhenium-186, tin-117m and tungsten-188 (parent of rhenium-188). The nine hydraulic tube (HT) positions in the central high flux region permit the insertion and removal of targets at any time during the operating cycle (22 24 days) and have traditionally represented a major site for production of medical radioisotopes. To increase the irradiation capabilities of the HFIR, special target holders have recently been designed and fabricated which will be installed in the six Peripheral Target Positions (PTP), which are also located in the high flux region. These positions are only accessible during reactor refueling and will be used for long-term irradiations, such as required for the production of tin-117m and tungsten-188. Each of the PTP tubes will be capable of housing a maximum of eight HT targets, thus increasing the total maximum number of HT targets from the current nine, to a total of 57. In this paper the therapeutic use of reactor-produced radioisotopes for bone pain palliation and vascular brachytherapy and the therapeutic medical radioisotope production capabilities of the ORNL HFIR are briefly discussed.

Knapp, F. F.; Beets, A. L.; Mirzadeh, S.; Alexander, C. W.; Hobbs, R. L.

1999-01-01

35

Production of medical radioisotopes in the ORNL high flux isotope reactor (HFIR) for cancer treatment and arterial restenosis therapy after PICA  

NASA Astrophysics Data System (ADS)

The High Flux Isotope Reactor ( HFIR) at the Oak Ridge National Laboratory ( ORNL) represents an important resource for the production of a wide variety of medical radioisotopes. First beginning operation in 1965, the high thermal neutron flux (2.5×1015 neutrons/cm2/sec at 85 MW) and versatile target irradiation and handling facilities provide the opportunity for production of a wide variety of neutron-rich medical radioisotopes of current interest for therapy. In addition to serving as a key production site for californium-252 and other transuranic elements, important examples of therapeutic radioisotopes which are currently routinely produced in the HFIR for distribution include dysprosium-166 (parent of holmium-166), rhenium-186, tin-117 m and tungsten-188 (parent of rhenium-188). The nine hydraulic tube ( HT) positions in the central high flux region permit the insertion and removal of targets at any time during the operating cycle (22-24 days) and have traditionally represented a major site for production of medical radioisotopes. To increase the irradiation capabilities of the HFIR, special target holders have recently been designed and fabricated which will be installed in the six Peripheral Target Positions ( PTP), which are also located in the high flux region. These positions are only accessible during reactor refueling and will be used for long-term irradiations, such as required for the production of tin-117 m and tungsten-188. Each of the PTP tubes will be capable of housing a maximum of eight HT targets, thus increasing the total maximum number of HT targets from the current nine, to a total of 57. In this paper the therapeutic use of reactor-produced radioisotopes for bone pain palliation and vascular brachytherapy and the therapeutic medical radioisotope production capabilities of the ORNL HFIR are briefly discussed.

Knapp, F. F.; Beets, A. L.; Mirzadeh, S.; Alexander, C. W.; Hobbs, R. L.

1999-01-01

36

Masters Thesis- Criticality Alarm System Design Guide with Accompanying Alarm System Development for the Radioisotope Production Laboratory in Richland, Washington  

SciTech Connect

A detailed instructional manual was created to guide criticality safety engineers through the process of designing a criticality alarm system (CAS) for Department of Energy (DOE) hazard class 1 and 2 facilities. Regulatory and technical requirements were both addressed. A list of design tasks and technical subtasks are thoroughly analyzed to provide concise direction for how to complete the analysis. An example of the application of the design methodology, the Criticality Alarm System developed for the Radioisotope Production Laboratory (RPL) of Richland, Washington is also included. The analysis for RPL utilizes the Monte Carlo code MCNP5 for establishing detector coverage in the facility. Significant improvements to the existing CAS were made that increase the reliability, transparency, and coverage of the system.

Greenfield, Bryce A.

2009-12-20

37

Production of {sup 17}F, {sup 15}O and other radioisotopes for PET using a 3 MV electrostatic tandem accelerator  

SciTech Connect

Target systems for the production of positron emitting radioisotopes used for medical research with positron emission tomography (PET) are under development for a 3 MV electrostatic tandem accelerator (NEC 9SDH-2). This machine is intended primarily for the continuous production of short lived tracers labeled with {sup 15}O (t{sub 1/2}=122 s) or {sup 17}F (t{sub 1/2}=65 s) for determining regional cerebral blood flow in humans. Simple gas, liquid, and solid target systems are presented for the production of [{sup 15}O]H{sub 2}O (yield at saturation 13 mCi/{mu}A), [{sup 17}F]F{sub 2} (22 mCi/{mu}A), [{sup 17}F] fluoride (aq.) (12 mCi/{mu}A), [{sup 18}F]fluoride (aq.) (21 mCi/{mu}A), [{sup 13}N] in graphite (25 mCi/{mu}A), and [{sup 11}C]CO{sub 2} (2.3 mCi/{mu}A). Current limitations on single window targets for each production are discussed.

Roberts, A. D. [Medical Physics Department, University of Wisconsin, Madison, Wisconsin 53706 (United States); Psychology Department, University of Wisconsin, Madison, Wisconsin 53706 (United States); Davidson, R. J. [Psychology Department, University of Wisconsin, Madison, Wisconsin 53706 (United States); Nickles, R. J. [Medical Physics Department, University of Wisconsin, Madison, Wisconsin 53706 (United States)

1999-06-10

38

Production of Lithium, Beryllium, and Boron by Hypernovae  

E-print Network

We investigate a possible nucleosynthetic signature of highly energetic explosions of C-O cores ("hypernovae," HNe) which might be associated with gamma-ray bursts (GRBs). We note that the direct impact of C- and O-enriched hypernova ejecta on the ambient hydrogen and helium leads to spallation reactions which can produce large amounts of the light nuclides lithium, beryllium, and boron (LiBeB). Using analytic velocity spectra of the hypernova ejecta, we calculate the LiBeB yields of different exploding C-O cores associated with observed hypernovae. The deduced yields are $\\sim 10^3$ times higher than those produced by similar (direct) means in normal Type II supernovae, and are higher than the commonly used ones arising from shock wave acceleration induced by Type II supernova (SN) explosions. To avoid overproduction of these elements in our Galaxy, hypernovae should be rare events, with $\\la 10^{-3}$ hypernovae per supernova, assuming a constant HN/SN ratio over time. This rate is in good agreement with that of long duration GRBs if we assume that the gamma-ray emission is focussed with a beaming factor $\\Omega/4\\pi \\la 10^{-2}$. This encouraging result supports the possible HN-GRB association. Thus, Galactic LiBeB abundance measurements offer a promising way to probe the HN rate history and the possible HN-GRB correlation. On the other hand, if hypernovae are associated to very massive pregalactic stars (Population III) they would produce a LiBeB pre-enrichment in proto-galactic gas, which could show up as a plateau in the lowest metallicities of the Be-Fe relation in halo stars.

Brian D. Fields; Frederic Daigne; Michel Casse; Elisabeth Vangioni-Flam

2001-07-25

39

FOLIAR BORON ENHANCES LEAF CHLOROSIS AND DOES NOT AFFECT PECAN PRODUCTION AND NUT QUALITY  

Microsoft Academic Search

The narrow range between boron (B) deficiency and toxicity compared with other micronutrients is a serious problem for sustainable production of pecan throughout the southwest United States of America. However, performance of pecan under foliar B is lacking. Five B treatments (0, 0.5, 1.0, 1.5 kg B ha, water spray) were applied to 27 years old trees of pecan variety

Shad Khan Khalil; John Mexal; Abdur Rehman; Amanullah; Fida Muhammad; Amir Zaman Khan

2011-01-01

40

Production and blast-furnace smelting of boron-alloyed iron-ore pellets  

SciTech Connect

Industrial test data are presented regarding the production (at Sokolovsk-Sarbaisk mining and enrichment enterprise) and blast-furnace smelting (at Magnitogorsk metallurgical works) of boron-alloyed iron-ore pellets (500000 t). It is shown that, thanks to the presence of boron, the compressive strength of the roasted pellets is increased by 18.5%, while the strength in reduction is doubled; the limestone consumption is reduced by 11%, the bentonite consumption is halved, and the dust content of the gases in the last section of the roasting machines is reduced by 20%. In blast-furnace smelting, the yield of low-sulfur (<0.02%) hot metal is increased from 65-70 to 85.1% and the furnace productivity from 2.17-2.20 to 2.27 t/(m{sup 3} day); coke consumption is reduced by 3-8 kg/t of hot metal. The plasticity and stamping properties of 08IO auto-industry steel are improved by microadditions of boron.

A.A. Akberdin; A.S. Kim [Abishev Chemicometallurgical Institute, Abishev (Kazakhstan)

2008-08-15

41

The Spallagenic Production Rates of Lithium, Beryllium and Boron  

E-print Network

We calculate the production rates of Li6, Li7, Be9, B10 and B11 via spallation of Carbon, Nitrogen and Oxygen nuclei by protons and alpha-particles and by alpha-alpha fusion reactions. We include recent measurements of the cross sections of alpha-alpha fusion reactions and find that the computations yield rates of Li6 and Li7 production that are nearly a factor of two smaller than previously calculated. We begin by using the `straight ahead' approximation for the fragment energy and the `leaky-box' model for product capture in the Galaxy. In addition we test the straight ahead approximation by recalculating the production rates using an empirical description of the fragment energy distribution and find that the results closely match. We have also calculated the rates for various cosmic ray spectra and find that the hardest spectra tested decrease the rates with CR CNO by approximately an order of magnitude relative to our chosen standard. Finally we have computed the Population I elemental ratios and the Population II scaling relations for our standard and find that our computations predict an abundance of Lithium for a given abundance of Beryllium that is 1/4 smaller than previously derived.

J. P. Kneller; J. R. Phillips; T. P. Walker

2000-08-04

42

Annual Technical Progress Report of Radioisotope Power System Materials Production and Technology Tasks for October 1, 2003 through September 30, 2004  

SciTech Connect

The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, ORNL produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. This report reflects program guidance from the Office of Space and Defense Power Systems for fiscal year (FY) 2004. Production and production maintenance activities for flight quality (FQ) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. In all three cases, production maintenance is assured by the manufacture of limited quantities of FQ components. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new radioisotope power systems.

None listed

2005-06-01

43

Five Years of Cyclotron Radioisotope Production Experiences at the First PET-CT in Venezuela  

SciTech Connect

Five years operation of a compact cyclotron installed at PET-CT facility in Caracas, Venezuela is given. Production rate of {sup 18}F labeled FDG, operation and radiation monitoring experience are included. We conclude that {sup 18}FDG CT-PET is the most effective technique for patient diagnosis.

Colmenter, L.; Coelho, D.; Esteves, L. M.; Ruiz, N.; Morales, L.; Lugo, I. [Centro Diagnostico Docente, Las Mercedes, Caracas (Venezuela); Sajo-Bohus, L.; Liendo, J. A.; Greaves, E. D.; Barros, H. [Universidad Simon Bolivar, Seccion de Fisica Nuclear, Caracas (Venezuela); Castillo, J. [University of Applied Science of Aachen (Germany)

2007-10-26

44

Cosmic Ray production of Beryllium and Boron at high redshift  

E-print Network

Recently, new observations of Li6 in Pop II stars of the galactic halo have shown a surprisingly high abundance of this isotope, about a thousand times higher than its predicted primordial value. In previous papers, a cosmological model for the cosmic ray-induced production of this isotope in the IGM has been developed to explain the observed abundance at low metallicity. In this paper, given this constraint on the Li6, we calculate the non-thermal evolution with redshift of D, Be, and B in the IGM. In addition to cosmological cosmic ray interactions in the IGM, we include additional processes driven by SN explosions: neutrino spallation and a low energy component in the structures ejected by outflows to the IGM. We take into account CNO CRs impinging on the intergalactic gas. Although subdominant in the galactic disk, this process is shown to produce the bulk of Be and B in the IGM, due to the differential metal enrichment between structures (where CRs originate) and the IGM. We also consider the resulting extragalactic gamma-ray background which we find to be well below existing data. The computation is performed in the framework of hierarchical structure formation considering several star formation histories including Pop III stars. We find that D production is negligible and that a potentially detectable Be and B plateau is produced by these processes at the time of the formation of the Galaxy (z ~ 3).

Emmanuel Rollinde; David Maurin; Elisabeth Vangioni; Keith A. Olive; Susumu Inoue

2007-07-13

45

LANL Activities Supporting Electron Accelerator Production of 99Mo for NorthStar Medical Radioisotopes, LLC  

SciTech Connect

Summary of LANL FY12 Activities are: (1) Preparation, performance, and data analysis for the FY12 accelerator tests at ANL - (a) LANL designed and installed a closed-loop helium target cooling system at ANL for the FY12 accelerator tests, (b) Thermal test was performed on March 27, (c) 24 h production test to follow the accelerator upgrade at ANL; (2) Local target shielding design and OTR/IR recommendations - (a) Target dose rate and activation products were calculated with MCNPX, (b) {sup 206}Pb({gamma},2n){sup 204m}Pb vs {sup 204g}Pb branching ratio unpublished, will measure using the LANL microtron, (c) OTR system nearing final configuration, (d) IR prototype system demonstrated during the recent thermal test at ANL; (3) Target housing lifetime estimation - Target housing material specifications and design to be finalized following the thermal test, lifetime not believed to be an issue; and (4) Target cooling system reliability - Long duration system characterizations will begin following the thermal test.

Dale, Gregory E. [Los Alamos National Laboratory; Kelsey, Charles T. IV [Los Alamos National Laboratory; Woloshun, Keith A. [Los Alamos National Laboratory; Holloway, Michael A. [Los Alamos National Laboratory; Olivas, Eric R. [Los Alamos National Laboratory; Dalmas, Dale A. [Los Alamos National Laboratory; Romero, Frank P. [Los Alamos National Laboratory; Hurtle, Kenneth P. [Los Alamos National Laboratory

2012-07-11

46

Radioisotope research, production, and processing at the University of Missouri Research Reactor  

SciTech Connect

The University of Missouri Research Reactor (MURR) is a 10 MW, light-water-cooled and moderated research reactor which first achieved criticality in 1996 and is currently the highest powered university-owned research reactor in the U.S. For many years a major supplier of reactor-produced isotopes for research and commercial purposes, in the last 15 years MURR has concentrated on development of reactor-produced beta-particle emitters for experimental use in nuclear medicine therapy of cancer and rheumatoid arthritis. MURR has played a major role in the development of bone cancer pain palliation with the agents {sup 153}Sm EDTMP and {sup 186}Re/{sup 188}Re HEDP, as well as in the use of {sup 186}Re, {sup 177}Lu, {sup 166}Ho, and {sup 105}Rh for radioimmunotherapy and receptor-agent-guided radiotherapy. MURR is also responsible for the development of therapeutic, {sup 90}Y-labeled glass microspheres for the treatment of liver tumors, a product ({sup 90}Y Therasphere{trademark}) which is currently an approved drug in Canada. MURR has also pioneered the development of {sup 188}W/{sup 188}Re and {sup 99}Mo/{sup 99m}Tc gel generators, which make the use of low specific activity {sup 188}W and {sup 99}Mo practical for such isotope generators.

Ehrhardt, G.J.; Ketring, A.R.; Ja, Wei; Ma, D.; Zinn, K.; Lanigan, J.

1995-12-31

47

Annual Technical Progress Report of Radioisotope Power System Materials Production and Technical Program Tasks for October 1, 2005 through September 30, 2006  

SciTech Connect

The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, ORNL produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. This report reflects program guidance from the Office of Space and Defense Power Systems for fiscal year (FY) 2006. Production activities for prime quality (prime) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new radioisotope power systems.

None

2007-04-02

48

ANNUAL TECHNICAL PROGRESS REPORT OF RADIOISOTOPE POWER SYSTEMS MATERIALS PRODUCTION AND TECHNOLOGY PROGRAM TASKS FOR OCTOBER 1, 2010 THROUGH SEPTEMBER 30, 2011  

SciTech Connect

The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration (NASA) for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, the Oak Ridge National Laboratory (ORNL) produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. These components were also produced for the Pluto New Horizons and Mars Science Lab missions launched in January 2006 and November 2011respectively. The ORNL has been involved in developing materials and technology and producing components for the DOE for nearly four decades. This report reflects program guidance from the Office of RPS for fiscal year (FY) 2011. Production activities for prime quality (prime) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new RPS. Work has also been initiated to establish fabrication capabilities for the Light Weight Radioisotope Heater Units.

King, James F [ORNL

2012-05-01

49

ANNUAL TECHNICAL PROGRESS REPORT OF RADIOISOTOPE POWER SYSTEM MATERIALS PRODUCTION AND TECHNOLOGY PROGRAM TASKS FOR OCTOBER 1, 2005 THROUGH SEPTEMBER 30, 2006  

SciTech Connect

The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, ORNL produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. This report reflects program guidance from the Office of Space and Defense Power Systems for fiscal year (FY) 2006. Production activities for prime quality (prime) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new radioisotope power systems.

King, James F [ORNL

2007-04-01

50

ANNUAL TECHNICAL PROGRESS REPORT OF RADIOISOTOPE POWER SYSTEM MATERIALS PRODUCTION AND TECHNOLOGY PROGRAM TASKS FOR OCTOBER 1, 2004, THROUGH SEPTEMBER 30, 2005  

SciTech Connect

The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, ORNL produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. This report reflects program guidance from the Office of Space and Defense Power Systems for fiscal year (FY) 2005. Production activities for prime quality (prime) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new radioisotope power systems.

None

2005-09-30

51

Surface-sensitive analysis of materials used in the production of PET radioisotopes  

SciTech Connect

The use of computer operated cyclotrons for clinical production of radiotracers for PET has made data on target performance (observed by a variety of users and with large statistics) recently available. The issues of consistent fluoride ion yields and repeatable FDG synthesis yields are of singular importance to the ordinary clinical user. For widespread manufacturing of compounds like FDG, it will be essential to have any issues affecting yield well understood. Much work has been done on water targets looking at the effect on yield of impurities in target water (before and after irradiation), dose rate, synthesis setup, overpressures, and cooling conditions. It is in this environment that the authors have begun to look at the surface chemistry of target body and window materials in order to better understand the mechanisms of target performance and lifetime. Ample anecdotal evidence exists for phenomena of {open_quotes}burn in,{close_quotes} slow or rapid deterioration due to contaminants in target water, and the required target rebuild or cleaning procedure for best yields. However quantitative methods for understanding the same phenomena are few. One of the most commonly used diagnostic tools for target failure analysis to date has been simple visual inspection of the windows and target body during target rebuilding. One can get a good idea of beam hot spots, contamination in helium recirculation systems, and accumulation of unwanted material in the beam strike. However, the color and finish of a deposit is subject to interpretation, and yields no chemical information or thickness of deposit. More quantitative methods exist. The work here focusing on the use of ESCA for target surface analysis.

Alvord, B. [CTI, Inc., Knoxville, TN (United States)

1994-12-31

52

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

NASA Astrophysics Data System (ADS)

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

Wiley, Charles Schenck

2011-12-01

53

Annual Technical Progress Report of Radioisotope Power Systems Materials Production and Technology Program Tasks for October 1, 2007 Through September 30,2008  

SciTech Connect

The Office of Radioisotope Power Systems (RPS) of the Department of Energy (DOE) provides RPS for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration (NASA) for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. For the Cassini Mission, ORNL produced carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS) used in the generators. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. This report reflects program guidance from the Office of RPS for fiscal year (FY) 2008. Production activities for prime quality (prime) CBCF insulator sets, iridium alloy blanks and foil, and CVS are summarized in this report. Technology activities are also reported that were conducted to improve the manufacturing processes, characterize materials, or to develop information for new RPS.

King, James F [ORNL

2009-04-01

54

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

55

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1982  

SciTech Connect

The radioisotope production and distribution activities by facilities at Argonne National Laboratory, Pacific Northwest Laboratory, Brookhaven National Laboratory, Hanford Engineering Development Laboratory, Idaho Operations Office, Los Alamos Scientific Laboratory, Oak Ridge National Laboratory, Savannah River Laboratory, and UNC Nuclear Industries, Inc. are listed. The information is divided into five sections: isotope suppliers, facility, contacts, and isotopes or services supplied; alphabetical list of customers, and isotopes purchased; alphabetical list of isotopes cross-referenced to customs numbers; geographical location of radioisotope customers; and radioisotope sales and transfers-FY 1982. (MHR)

Richards, M.P.

1983-08-01

56

Melt production beneath Mt. Shasta from boron data in primitive melt inclusions.  

PubMed

Most arc magmas are thought to be generated by partial melting of the mantle wedge induced by infiltration of slab-derived fluids. However, partial melting of subducting oceanic crust has also been proposed to contribute to the melt generation process, especially when young and hot lithosphere is being subducted. The isotopic composition of boron measured in situ in olivine-hosted primitive melt inclusions in a basaltic andesite from Mt. Shasta, California, is characterized by large negative values that are also highly variable (delta(11)B = -21.3 to -0.9 per mil). The boron concentrations, from 0.7 to 1.6 parts per million, are lower than in most other arc lavas. The relation between concentration and isotopic composition of boron observed here supports a hypothesis that materials left after dehydration of the subducting slab may have contributed to the generation of basaltic andesite lavas at Mt. Shasta. PMID:11452119

Rose, E F; Shimizu, N; Layne, G D; Grove, T L

2001-07-13

57

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1979  

SciTech Connect

The fifteenth edition of the radioisotope customer list was prepared at the request of the Division of Financial Services, Office of the Assistant Secretary for Environment, Department of Energy (DOE). This document lists DOE's radioisotope production and distribution activities by its facilities at Argonne National Laboratory; Pacific Northwest Laboratory; Brookhaven National Laboratory; Hanford Engineering Development Laboratory; Idaho Operations Office; Los Alamos Scientific Laboratory; Mound Facility; Oak Ridge National Laboratory; Rocky Flats Area Office; Savannah River Laboratory; and UNC Nuclear Industries, Inc. The information is divided into five sections: Isotope suppliers, facility, contracts and isotopes or services supplied; alphabetical list of customers, and isotopes purchased; alphabetical list of isotopes cross-referenced to customer numbers; geographical location of radioisotope customers; and radioisotope sales and transfers-FY 1979.

Burlison, J.S. (comp.)

1980-06-01

58

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1981  

SciTech Connect

The seventeenth edition of the radioisotope customer list was prepared at the request of the Office of Health and Environmental Research, Office of Energy Research, Department of Energy (DOE). This document lists DOE's radioisotope production and distribution activities by its facilities at Argonne National Laboratory: Pacific Northwest Laboratory; Brookhaven National Laboratory; Hanford Engineering Development Laboratory; Idaho Operations Office; Los Alamos Scientific Laboratory; Mound Facility; Oak Ridge National Laboratory; Savannah River Laboratory; and UNC Nuclear Industries, Inc. The information is divided into five sections: (1) isotope suppliers, facility, contracts and isotopes or services supplied; (2) alphabetical list of customers, and isotopes purchased; (3) alphabetical list of isotopes cross-referenced to customer numbers; (4) geographical location of radioisotope customers; and (5) radioisotope sales and transfers-FY 1980.

Burlison, J.S. (comp.)

1982-09-01

59

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1980  

SciTech Connect

The sixteenth edition of the radioisotope customer list was prepared at the request of the Office of Health and Environmental Research, Office of energy Research, Department of Energy (DOE). This document lists DOE's radioisotope production and distribution activities by its facilities at Argonne National Laboratory; Pacific Northwest Laboratory; Brookhaven National Laboraory; Hanford Engineering Development Laboratory; Idaho Operations Office; Los Alamos Scientific Laboratory; Mound Facility; Oak Ridge National Laboratory; Savannah River Laboratory; and UNC Nuclear Industries, Inc. The information is divided into five sections: (1) isotope suppliers, facility, contracts and isotopes or services supplied; (2) alphabetical list of customers, and isotopes purchased; (3) alphabetical list of isotopes cross-referenced to customer numbers; (4) geographical location of radioisotope customers; and (5) radioisotope sales and transfers-FY 1980.

Burlison, J.S. (comp.)

1981-08-01

60

Jaguar Procedures for Detonation Behavior of Explosives Containing Boron  

NASA Astrophysics Data System (ADS)

The Jaguar product library was expanded to include boron and boron containing products by analysis of Available Hugoniot and static volumetric data to obtain constants of the Murnaghan relationships for the components. Experimental melting points were also utilized to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX—boron mixtures calculated with these relationships using Jaguar are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that the boron does not react near the detonation front or that boron mixtures exhibit eigenvalue detonation behavior (as shown by some aluminized explosives), with higher detonation velocities at the initial points. Analyses of calorimetric measurements for RDX—boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the detonation properties of the formulation.

Stiel, L. I.; Baker, E. L.; Capellos, C.

2009-12-01

61

Experimental and theoretical investigations on the adsorption of 2'-deoxyguanosine oxidation products at oxidized boron-doped diamond electrodes.  

PubMed

Electrochemical oxidation of 2'-deoxyguanosine has been performed on boron-doped diamond (BDD) electrodes, resulting in a strong adsorption of the formed oxidized products onto the BDD surface. The adsorption behavior has been investigated by studying the electrochemical behavior of a redox probe ([IrCl6]3-) using cyclic voltammetry. The most probable situations are the formation of (A) an insulating adsorbed film resulting in a partially blocked electrode behavior, (B) a porous film, or (C) an overall conductive film. Different parameters such as the standard rate constant, the charge-transfer coefficient, the electrode/adsorbed products/solution interface resistance, and the formal potential of the redox couple were determined. Through comparison of theoretical current-potential curves obtained by analytical calculations with experimental cyclic voltammograms, we found that the oxidized products of 2'-deoxyguanosine form a continuous conductive film on BDD. PMID:17411007

Fortin, Elodie; Vieil, Eric; Mailley, Pascal; Szunerits, Sabine; Livache, Thierry

2007-05-15

62

Boron in the Small Magellanic Cloud: A Novel Test of Light Element Production  

E-print Network

Hubble Space Telescope STIS observations of the B III resonance line at 2066A have been obtained and analyzed for two Small Magellanic Cloud (SMC) B-type stars. While boron is not detected in either star, upper limits to the boron abundance are set, with 12+log(B/H) le 1.6 for both AV 304 and NGC 346-637. The upper limits are consistent with the relationship between boron and oxygen previously reported for Galactic disk stars. The SMC upper limits are discussed in light of that galaxy's star formation history, present oxygen abundance, and its present cosmic ray flux. The UV spectrum has also been used to determine the iron-group abundances in the SMC stars. For AV 304, [Fe/H]=-0.6 pm 0.2, from both an absolute and a differential analysis (with respect to the Galactic B-type star HD 36591). This is consistent with results from A-F supergiants in the SMC. A lower iron abundance is found for NGC 346-637, [Fe/H]=-1.0 pm 0.3, but this is in good agreement with the supergiant iron abundances in NGC 330,another young SMC cluster. We propose NGC 346-637 may be an unrecognized binary though, which complicates its spectral analysis.

A. M. Brooks; K. A. Venn; D. L. Lambert; M. Lemke; K. Cunha; V. V. Smith

2002-04-02

63

Boron in the Small Magellanic Cloud A Novel Test of Light Element Production  

E-print Network

Hubble Space Telescope STIS observations of the B III resonance line at 2066A have been obtained and analyzed for two Small Magellanic Cloud (SMC) B-type stars. While boron is not detected in either star, upper limits to the boron abundance are set, with 12+log(B/H) le 1.6 for both AV 304 and NGC 346-637. The upper limits are consistent with the relationship between boron and oxygen previously reported for Galactic disk stars. The SMC upper limits are discussed in light of that galaxy's star formation history, present oxygen abundance, and its present cosmic ray flux. The UV spectrum has also been used to determine the iron-group abundances in the SMC stars. For AV 304, [Fe/H]=-0.6 pm 0.2, from both an absolute and a differential analysis (with respect to the Galactic B-type star HD 36591). This is consistent with results from A-F supergiants in the SMC. A lower iron abundance is found for NGC 346-637, [Fe/H]=-1.0 pm 0.3, but this is in good agreement with the supergiant iron abundances in NGC 330,another you...

Brooks, A M; Lambert, D L; Lemke, M; Cunha, K; Smith, V V

2002-01-01

64

The production of patient dose level 99mTc medical radioisotope using laser-driven proton beams  

NASA Astrophysics Data System (ADS)

The medical isotope 99mTc (technetium) is used in over 30 million nuclear medical procedures annually, accounting for over 80% of the worldwide medical isotope usage. Its supply is critical to the medical community and a worldwide shortage is expected within the next few decades as current fission reactors used for its generation reach their end of life. The cost of build and operation of replacement reactors is high and as such, alternative production mechanisms are of high interest. Laser-accelerated proton beams have been widely discussed as being able to produce Positron Emission Tomography (PET) isotopes once laser architecture evolved to high repetition rates and energies. Recent experimental results performed on the Vulcan Laser Facility in the production of 99mTc through 100Mo (p,2n) 99mTc demonstrate the ability to produce this critical isotope at the scales required for patient doses using diode pumped laser architecture currently under construction. The production technique, laser and target requirements are discussed alongside a timeline and cost for a prototype production facility.

Clarke, R.; Dorkings, S.; Neely, D.; Musgrave, I.

2013-05-01

65

Taming Highly Charged Radioisotopes  

NASA Astrophysics Data System (ADS)

The precise and accurate mass of short-lived radioisotopes is a very important parameter in physics. Contribution to the improvement of nuclear models, metrological standard fixing and tests of the unitarity of the Caibbibo-Kobayashi-Maskawa (CKM) matrix are a few examples where the mass value plays a major role. TRIUMF's ion trap for atomic and nuclear physics (TITAN) is a unique facility of three online ion traps that enables the mass measurement of short-lived isotopes with high precision (˜10-8). At present TITAN's electron beam ion trap (EBIT) increases the charge state to increase the precision, but there is no facility to significantly reduce the energy spread introduced by the charge breeding process. The precision of the measured mass of radioisotopes is linearly dependent on the charge state while the energy spread of the charged radioisotopes affects the precision adversely. To boost the precision level of mass measurement at TITAN without loosing too many ions, a cooler Penning trap (CPET) is being developed. CPET is designed to use either positively (proton) or negatively (electron) charged particles to reduce the energy spread via sympathetic cooling. Off-line setup of CPET is complete. Details of the working principles and updates are presented

Chowdhury, Usman; Eberhardt, Benjamin; Jang, Fuluni; Schultz, Brad; Simon, Vanessa; Delheij, Paul; Dilling, Jens; Gwinner, Gerald

2012-10-01

66

Radioisotopes as Political Instruments, 1946-1953.  

PubMed

The development of nuclear "piles," soon called reactors, in the Manhattan Project provided a new technology for manufacturing radioactive isotopes. Radioisotopes, unstable variants of chemical elements that give off detectable radiation upon decay, were available in small amounts for use in research and therapy before World War II. In 1946, the U.S. government began utilizing one of its first reactors, dubbed X-10 at Oak Ridge, as a production facility for radioisotopes available for purchase to civilian institutions. This program of the U.S. Atomic Energy Commission was meant to exemplify the peacetime dividends of atomic energy. The numerous requests from scientists outside the United States, however, sparked a political debate about whether the Commission should or even could export radioisotopes. This controversy manifested the tension in U.S. politics between scientific internationalism as a tool of diplomacy, associated with the aims of the Marshall Plan, and the desire to safeguard the country's atomic monopoly at all costs, linked to American anti-Communism. This essay examines the various ways in which radioisotopes were used as political instruments-both by the U.S. federal government in world affairs, and by critics of the civilian control of atomic energy-in the early Cold War. PMID:20725612

Creager, Angela N H

2009-01-01

67

Waste minimization in the Los Alamos Medical Radioisotope Program  

SciTech Connect

Since the mid-1970s the Los Alamos Medical Radioisotope Program has been irradiating target materials to produce and recover radioisotopes for applications in medicine, environmental science, biology, physics, materials research, and other disciplines where radiotracers find utility. By necessity, the chemical processing of targets and the isolation of radioisotopes generates radioactive waste materials. Recent years have brought pressure to discontinue the use of hazardous materials and to minimize radioactive waste volumes. Substantial waste reduction measures have been introduced at the irradiation facility, in processing approaches, and even in the ways the product isotopes are supplied to users.

Taylor, W.A.; Jamriska, D.J.; Hamilton, V.T.; Heaton, R.C.; Phillips, D.R.; Staroski, R.C.; Garcia, J.B.; Garcia, J.G.; Ott, M.A.

1994-04-01

68

Blow-Out Velocities of Solutions of Hydrocarbons and Boron Hydride - Hydrocarbon Reaction Products in a 1 7/8-Inch-Diameter Combustor  

NASA Technical Reports Server (NTRS)

Blow-out velocities were determined for JP-4 solutions containing: (1) 10 % ethylene - decaborane reaction product, (2) 10% and 20% acetylene - diborane reaction product, and (3) 5.5%, 15.7%, and 30.7% methylacetylene - diborane reaction product. These were compared with blow-out velocities for JP-4, propylene oxide, and neohexane and previously reported data for JP-4 solutions of pentaborane. For those reaction products investigated, the blow-out velocities at a fixed equivalence ratio were higher for those materials containing higher boron concentrations; that is, blow-out velocity increased in the following order: (1) methylacetylene - diborane, (2) acetylene - diborane, and (3) ethylene - decaborane reaction products.

Morris, James F.; Lord, Albert M.

1957-01-01

69

High-Efficient Production of Boron Nitride Nanosheets via an Optimized Ball Milling Process for Lubrication in Oil  

NASA Astrophysics Data System (ADS)

Although tailored wet ball milling can be an efficient method to produce a large quantity of two-dimensional nanomaterials, such as boron nitride (BN) nanosheets, milling parameters including milling speed, ball-to-powder ratio, milling ball size and milling agent, are important for optimization of exfoliation efficiency and production yield. In this report, we systematically investigate the effects of different milling parameters on the production of BN nanosheets with benzyl benzoate being used as the milling agent. It is found that small balls of 0.1-0.2 mm in diameter are much more effective in exfoliating BN particles to BN nanosheets. Under the optimum condition, the production yield can be as high as 13.8% and the BN nanosheets are 0.5-1.5 ?m in diameter and a few nanometers thick and of relative high crystallinity and chemical purity. The lubrication properties of the BN nanosheets in base oil have also been studied. The tribological tests show that the BN nanosheets can greatly reduce the friction coefficient and wear scar diameter of the base oil.

Deepika; Li, Lu Hua; Glushenkov, Alexey M.; Hait, Samik K.; Hodgson, Peter; Chen, Ying

2014-12-01

70

Radioisotope powered light sources  

SciTech Connect

Radioisotopes have been used for a number of years to excite phosphors to produce visible light. The advent of the nuclear age, however, made possible the preparation of radionuclides in larger quantities at relatively low prices, and with radiation properties that greatly expanded the potential applications for such lights. Current energy conservation needs and inflation leading to even higher costs for maintenance and capital equipment has provided the incentive for development of illuminators for air field markers using both byproduct krypton-85 and processed tritium. Background and current status of these developments are discussed.

Case, F. N.; Remini, W. C.

1980-01-01

71

Alternative Radioisotopes for Heat and Power Sources  

NASA Astrophysics Data System (ADS)

Production of 238Pu requires considerable facilities including a nuclear reactor and reprocessing plants that are very expensive to build and operate. Thus, a more economical alternative is very attractive to the industry. There are many alternative radioisotopes that exist but few that satisfy the criteria of performance, availability and cost to produce. Any alternative to 238Pu must exist in a chemical form that is compatible with the materials required to safely encapsulate the heat source at the high temperatures of operation and potential launch failure scenarios. The chemical form must also have suitable thermal properties to ensure maximum energy conversion efficiencies when integrated into radioisotope thermoelectric generators over the required mission durations. In addition, the radiation dose must be low enough for operators during production and not so prohibitive that excessive shielding mass is required on the space craft. This paper will focus on the preferred European alternative of 241Am, and the issues that will need to be addressed.

Tinsley, T.; Sarsfield, M.; Rice, T.

72

Therapeutic clinical applications of reactor-produced radioisotopes  

SciTech Connect

One of the most rapidly growing areas of clinical nuclear medicine is the therapeutic use of radioisotopes for applications in oncology, rheumatology and, more recently, interventional cardiology. With the rapidly increasing development and evaluation of new agents, their introduction into clinical use, and commercialization, the availability of high levels of therapeutic reactor-produced neutron-rich radioisotopes is of increasing importance. The goals of this paper are to discuss the issues associated with optimization of the production and processing of reactor-produced radioisotopes for therapy, with special emphasis on {sup 188}W, and the optimization of the use of the {sup 188}W/{sup 188}Re generator. In addition, other key examples of therapeutic radioisotopes of current interest and their specific clinical applications are discussed.

Knapp, F.F. Jr. [Oak Ridge National Lab., TN (United States)

1997-12-01

73

Silicon Carbide Radioisotope Batteries  

NASA Technical Reports Server (NTRS)

The substantial radiation resistance and large bandgap of SiC semiconductor materials makes them an attractive candidate for application in a high efficiency, long life radioisotope battery. To evaluate their potential in this application, simulated batteries were constructed using SiC diodes and the alpha particle emitter Americium Am-241 or the beta particle emitter Promethium Pm-147. The Am-241 based battery showed high initial power output and an initial conversion efficiency of approximately 16%, but the power output decayed 52% in 500 hours due to radiation damage. In contrast the Pm-147 based battery showed a similar power output level and an initial conversion efficiency of approximately 0.6%, but no degradation was observed in 500 hours. However, the Pm-147 battery required approximately 1000 times the particle fluence as the Am-242 battery to achieve a similar power output. The advantages and disadvantages of each type of battery and suggestions for future improvements will be discussed.

Rybicki, George C.

2005-01-01

74

NASA: Radioisotope Power Systems  

NSDL National Science Digital Library

This is a multimedia overview of RPS (radioisotope power systems), a type of nuclear energy technology that uses heat to produce electricity for powering spacecraft. The heat is produced by the natural radioactive decay of plutonium-238. RPS systems have been in use for more than 50 years, and could continue to support missions to some of the most extreme environments in the solar system. Advantages of RPS include: continuous operation over long-duration space missions, largely independent of changes in sunlight, temperature, charged particle radiation, or surface conditions like thick clouds or dust. This resource is part of NASA's Solar System Exploration website. It includes videos, 3D interactive animations, illustrations, schematics of RPS components, and fact sheets about how the technology has been used in past missions.

2012-10-30

75

JAGUAR Procedures for Detonation Behavior of Explosives Containing Boron  

NASA Astrophysics Data System (ADS)

The JAGUAR product library was expanded to include boron and boron containing products. Relationships of the Murnaghan form for molar volumes and derived properties were implemented in JAGUAR. Available Hugoniot and static volumertic data were analyzed to obtain constants of the Murnaghan relationship for solid boron, boron oxide, boron nitride, boron carbide, and boric acid. Experimental melting points were also utilized with optimization procedures to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX - boron mixtures calculated with these relationships using JAGUAR are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that boron mixtures may exhibit eigenvalue detonation behavior, as observed by aluminized combined effects explosives, with higher detonation velocities than would be achieved by a classical Chapman-Jouguet detonation. Analyses of calorimetric measurements for RDX - boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the energy output obtained from the detonation of the formulation.

Stiel, Leonard; Baker, Ernest; Capellos, Christos

2009-06-01

76

Experimental results and model calculations of excitation functions relevant to the production of specific radioisotopes for metabolic radiotherapy and for pet  

NASA Astrophysics Data System (ADS)

First results are given from the comparison of experimental values and model calculations on accelerator-produced high specific activity radionuclides in no-carrier-added (NCA) form. The relevant radioisotopes are: 64Cu, produced by natZn(d, ?xn) and natZn(d,2p) reactions, for simultaneous positron/negatron metabolic radiotherapy and PET imaging; 66Ga high-energy positron emitter (4.2 MeV), produced by natZn(d, xn) reactions, for metabolic radiotherapy and for PET; 186gRe, produced by 186W(p,n) and 186W(d,2n) reactions, for negatron (1.1 MeV) metabolic radiotherapy; 211At/ 211Po, produced by 209Bi( ?,2n) reaction (with spike of gamma emitter 210At produced by 209Bi( ?,3n) reaction) and 225Ac/ 213Bi/ 213Po, produced by 226Ra(p,2n) reaction, both for high-LET radiotherapy.

Menapace, E.; Birattari, C.; Bonardi, M. L.; Groppi, F.

2004-10-01

77

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

78

Cosmic Ray Models for Early Galactic Lithium, Beryllium, and Boron Production  

E-print Network

To understand better the early galactic production of Li, Be, and B by cosmic ray spallation and fusion reactions, the dependence of these production rates on cosmic ray models and model parameters is examined. The sensitivity of elemental and isotopic production to the cosmic ray pathlength magnitude and energy dependence, source spectrum, spallation kinematics, and cross section uncertainties is studied. Changes in these model features, particularly those features related to confinement, are shown to alter the Be- and B-versus-Fe slopes {}from a na\\"{\\i}ve quadratic relation. The implications of our results for the diffuse $\\gamma$-ray background are examined, and the role of chemical evolution and its relation to our results is noted. It is also noted that the unmeasured high energy behavior of $\\alpha+\\alpha$ fusion can lead to effects as large as a factor of 2 in the resultant yields. Future data should enable Population II Li, Be, and B abundances to constrain cosmic ray models for the early Galaxy.

Brian Fields; Keith Olive; David Schramm

1994-05-11

79

Tautomerism of anthraquinones: X. Quinizarin boron complex  

Microsoft Academic Search

Products of reactions of hydroxyanthraquinones with boric acid exist as equilibrium mixtures of tautomeric boron complexes\\u000a and boric acid esters in which one or two boron atoms are not coordinated to carbonyl groups. Tautomerism is responsible for\\u000a the appearance of several ?l,? bands in the electronic absorption spectra and considerable differences in the data obtained by different authors. Boron-containing\\u000a quinizarin

V. Ya. Fain; B. E. Zaitsev; M. A. Ryabov

2010-01-01

80

III 1 BORON  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

81

Computation and Analysis of the Global Distribution of the Radioxenon Isotope 133Xe based on Emissions from Nuclear Power Plants and Radioisotope Production Facilities and its Relevance for the Verification of the Nuclear-Test-Ban Treaty  

NASA Astrophysics Data System (ADS)

Monitoring of radioactive noble gases, in particular xenon isotopes, is a crucial element of the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The capability of the noble gas network, which is currently under construction, to detect signals from a nuclear explosion critically depends on the background created by other sources. Therefore, the global distribution of these isotopes based on emissions and transport patterns needs to be understood. A significant xenon background exists in the reactor regions of North America, Europe and Asia. An emission inventory of the four relevant xenon isotopes has recently been created, which specifies source terms for each power plant. As the major emitters of xenon isotopes worldwide, a few medical radioisotope production facilities have been recently identified, in particular the facilities in Chalk River (Canada), Fleurus (Belgium), Pelindaba (South Africa) and Petten (Netherlands). Emissions from these sites are expected to exceed those of the other sources by orders of magnitude. In this study, emphasis is put on 133Xe, which is the most prevalent xenon isotope. First, based on the emissions known, the resulting 133Xe concentration levels at all noble gas stations of the final CTBT verification network were calculated and found to be consistent with observations. Second, it turned out that emissions from the radioisotope facilities can explain a number of observed peaks, meaning that atmospheric transport modelling is an important tool for the categorization of measurements. Third, it became evident that Nuclear Power Plant emissions are more difficult to treat in the models, since their temporal variation is high and not generally reported. Fourth, there are indications that the assumed annual emissions may be underestimated by factors of two to ten, while the general emission patterns seem to be well understood. Finally, it became evident that 133Xe sources mainly influence the sensitivity of the monitoring system in the mid-latitudes, where the network coverage is particularly good.

Wotawa, Gerhard; Becker, Andreas; Kalinowski, Martin; Saey, Paul; Tuma, Matthias; Zähringer, Matthias

2010-05-01

82

RADIOISOTOPES IN ANIMAL AND PLANT BIOLOGY  

Microsoft Academic Search

Chapters are included on the fundamentals of nucleonics and ; radiation, radiation effects and isotope applications, radioisotopes in animal ; physiology and veterinary medicine, and radioisotopes in the plant kingdom. ; (D.E.B.);

O. F. F

1958-01-01

83

Mineral resource of the month: boron  

USGS Publications Warehouse

The article offers information on the mineral, boron. Boron compounds, particularly borates, have more commercial applications than its elemental relative which is a metalloid. Making up the 90% of the borates that are used worldwide are colemanite, kernite, tincal, and ulexite. The main borate deposits are located in the Mojave Desert of the U.S., the Tethyan belt in southern Asia, and the Andean belt of South America. Underground and surface mining are being used in gathering boron compounds. INSETS: Fun facts;Boron production and consumption.

Crangle, Robert D., Jr.

2012-01-01

84

How to Handle Radioisotopes Safely.  

ERIC Educational Resources Information Center

This booklet is one in a series of instructional aids designed for use by elementary and secondary school science teachers. The various units and forms of radioactive materials used by teachers are first considered. Then, the quantities of radioisotopes that a person may possess without a license from the Atomic Energy Commission (AEC) are…

Sulcoski, John W.

85

Fluidized bed combustion by?product treatment and leaching of acid soil affects growth and boron acquisition of maize  

Microsoft Academic Search

Fluidized bed combustion bottom ash (FBCBA) from coal burning power plants often contain substances that detrimentally affect plant growth [(e.g., boron (B)] when applied to soil. Leaf symptoms similar to B toxicity appeared when maize (Zea mays L.) was grown during Year?1 of a field experiment where FBCBA was incorporated (6,790 and 13,580 kg ha) in an acidic soil (Aquic

M. Zaifnejad; K. D. Ritchey; R. B. Clark; V. C. Baligar; D. C. Martens

1998-01-01

86

Future Supply of Medical Radioisotopes for the UK Report 2014  

E-print Network

The UK has no research nuclear reactors and relies on the importation of 99Mo and other medical radioisotopes (e.g. Iodine-131) from overseas (excluding PET radioisotopes). The UK is therefore vulnerable not only to global shortages, but to problems with shipping and importation of the products. In this context Professor Erika Denton UK national Clinical Director for Diagnostics requested that the British Nuclear Medicine Society lead a working group with stakeholders including representatives from the Science & Technology Facilities Council (STFC) to prepare a report. The group had a first meeting on 10 April 2013 followed by a working group meeting with presentations on 9th September 2013 where the scope of the work required to produce a report was agreed. The objectives of the report are: to describe the status of the use of medical radioisotopes in the UK; to anticipate the potential impact of shortages for the UK; to assess potential alternative avenues of medical radioisotope production for the UK m...

Neilly, Brian; Ballinger, Jim; Buscombe, John; Clarke, Rob; Ellis, Beverley; Flux, Glenn; Fraser, Louise; Hall, Adrian; Owen, Hywel; Paterson, Audrey; Perkins, Alan; Scarsbrook, Andrew

2015-01-01

87

Experimental study of the 165Ho(d, 2n) and 165Ho(d, p) nuclear reactions up to 20 MeV for production of the therapeutic radioisotopes 165Er and 166gHo  

NASA Astrophysics Data System (ADS)

The radioisotope 165Er ( T1/2 = 10.36 h) is a candidate for Auger-electron therapy. The ? --emitting 166gHo ( T1/2 = 26.83 h) is now being explored for various therapeutic applications. In the frame of our systematic study of charged particle production routes of therapeutic radionuclides the excitation functions of the 165Ho(d, 2n) 165Er and 165Ho(d, p) 166gHo reactions were measured up to 20 MeV by using a stacked foil irradiation technique and X/?-ray spectroscopy. The excitation function of the 165Ho(d, 2n) 165Er reaction was measured for the first time while for the 165Ho(d, p) 166gHo reaction only a single dataset of earlier measured cross-sections was found. The measured excitation functions were compared to the results of different nuclear reaction model codes. The calculated thick target yield of the 165Ho(d, 2n) reaction is significantly higher over the optimal energy range than that for the 165Ho(p, n) reaction investigated earlier by us. The integral yield of the 165Ho(d, p) 166gHo reaction is rather low compared to the established 165Ho(n, ?) 166Ho reaction in a nuclear reactor.

Tárkányi, F.; Hermanne, A.; Takács, S.; Ditrói, F.; Király, B.; Kovalev, S. F.; Ignatyuk, A. V.

2008-08-01

88

Subporphyrinato Boron(III) Hydrides.  

PubMed

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

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

2015-01-28

89

Magnetron sputtered boron films and TI/B multilayer structures  

DOEpatents

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

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

1993-04-20

90

Efficient boron nitride nanotube formation via combined laser-gas flow levitation  

DOEpatents

A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B.sub.xC.sub.yN.sub.z. The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula B.sub.xC.sub.yN.sub.z.

Whitney, R. Roy; Jordan, Kevin; Smith, Michael

2014-03-18

91

Cross-sections for (p,x) reactions on natural chromium for the production of (52,52m,)(54)Mn radioisotopes.  

PubMed

The production of positron-emitting isotopes of manganese is potentially important for developing contrast agents for dual-modality positron emission tomography and magnetic resonance (PET/MR) imaging, as well as for in vivo imaging of the biodistribution and toxicity of manganese. The decay properties of (52)Mn make it an excellent candidate for these applications, and it can easily be produced by bombardment of a chromium target with protons or deuterons from a low-energy biomedical cyclotron. Several parameters that are essential to this mode of production-target thickness, beam energy, beam current, and bombardment time-depend heavily on the availability of reliable, reproducible cross-section data. This work contributes to the routine production of (52g)Mn for biomedical research by contributing experimental cross-sections for natural chromium ((nat)Cr) targets for the (nat)Cr(p,x)(52g)Mn reaction, as well as for the production of the radiocontaminants (52m,54)Mn. PMID:25497324

Wooten, A Lake; Lewis, Benjamin C; Lapi, Suzanne E

2015-02-01

92

Synthesis and Characterization of a Boronated Metallophthalocyanine for Boron Neutron Capture Therapy.  

PubMed

Synthesis of the first fully characterized, water-soluble boronated phthalocyanine is reported. Reaction of 4-nitrophthalonitrile with dimethyl malonate in the presence of base yielded dimethyl (3,4-dicyanophenyl)malonate which was converted into dimethyl (3,4-dicyanophenyl)propargylmalonate by sequential treatment with potassium hydroxide and propargyl bromide. Formation of the o-carborane cage was accomplished by reaction of the alkyne with decaborane in acetonitrile at reflux. High-temperature solid state condensation of the resulting o-carboranylphthalonitrile with cobalt(II) chloride followed by ester deprotection and cation exchange provided the water-soluble closo-carbonylphthalocyanine product. The product contains 40 boron atoms (27% boron by weight) and may be useful as a tumor-seeking boron delivery agent for boron neutron capture therapy of cancer. PMID:11666577

Kahl, Stephen B.; Li, Jing

1996-06-19

93

Optimizing the boron effect  

Microsoft Academic Search

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

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

1973-01-01

94

Optimizing the boron effect  

Microsoft Academic Search

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

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

1973-01-01

95

Nuclear model calculations on the production of {sup 125,123}Xe and {sup 133,131,129,128}Ba radioisotopes  

SciTech Connect

In this study, production rates of {sup 125,123}Xe and {sup 133,131,129,128}Ba medical isotopes produced by {sup 127}I(p, 3n){sup 125}Xe, {sup 127}I(p, 5n){sup 123}Xe, {sup 133}Cs(p, n){sup 133mg}Ba, {sup 133}Cs(p, 3n){sup 131mg}Ba, {sup 133}Cs(p, 5n){sup 129}Ba, and {sup 133}Cs(p, 6n){sup 128}Ba reactions have been investigated up to 100 MeV incident proton energy. The preequilibrium calculations involve the hybrid model, the geometry-dependent hybrid model and the cascade exciton model. The calculated results are compared with the experimental data taken from the literature.

Aydin, A., E-mail: aaydin@kku.edu.tr; Pekdogan, H. [Kirikkale University, Faculty of Arts and Sciences (Turkey); Tel, E. [Osmaniye Korkut Ata University, Faculty of Arts and Sciences (Turkey); Kaplan, A. [Sueleyman Demirel University, Faculty of Arts and Sciences (Turkey)

2012-03-15

96

Power from Radioisotopes, Understanding the Atom Series.  

ERIC Educational Resources Information Center

This 1971 revision deals with radioisotopes and their use in power generators. Early developments and applications for the Systems for Nuclear Auxiliary Power (SNAP) and Radioisotope Thermoelectric Generators (RTGs) are reviewed. Present uses in space and on earth are included. Uses in space are as power sources in various satellites and space…

Corliss, William R.; Mead, Robert L.

97

Radioisotopes and the Age of the Earth  

Microsoft Academic Search

RATE is an acronym applied to a research project investigating radioisotope dating sponsored by the Institute for Creation Research and the Creation Research Society. It stands for Radioisotopes and the Age of The Earth. This article summarizes the purpose, history, and intermediate findings of the RATE project five years into an eight-year effort. It reports on the latest status of

Larry Vardiman; Steven A. Austin; John R. Baumgardner; Eugene F. Chaffin; Donald B. DeYoung; D. Russell Humphreys; Andrew A. Snelling

2003-01-01

98

Lithium-Beryllium-Boron : Origin and Evolution  

E-print Network

The origin and evolution of Lithium-Beryllium-Boron is a crossing point between different astrophysical fields : optical and gamma spectroscopy, non thermal nucleosynthesis, Big Bang and stellar nucleosynthesis and finally galactic evolution. We describe the production and the evolution of Lithium-Beryllium-Boron from Big Bang up to now through the interaction of the Standard Galactic Cosmic Rays with the interstellar medium, supernova neutrino spallation and a low energy component related to supernova explosions in galactic superbubbles.

Elisabeth Vangioni-Flam; Michel Casse; Jean Audouze

1999-07-13

99

Radioisotopes for radioimmunodetection (RAID) and radioimmunotherapy (RAIT)---current and new perspectives  

SciTech Connect

In this paper the availability and properties of radioisotopes for both radioimmunodiagnosis (RAID) and radioimmunotherapy (RAIT) are discussed. Examples are provided for radioisotopes available via direct production in nuclear reactors and accelerators or as daughters obtained from radionuclide generator systems whose parents are either reactor or accelerator produced. Important factors which must be considered for the use of a particular radioisotope include availability, the physical half-life and decay properties, and chemical versatility for protein attachment. Although both direct'' and indirect'' methods are available for attachment of radioisotopes to antibodies, this broad field of research is not reviewed in detail. Practical issues related to the availability and use of a variety of radionuclides are described. 47 refs., 5 tabs.

Knapp, F.F. Jr.

1991-01-01

100

US Department of Energy radioisotope customers with summary of radioisotope shipments, FY 1988  

SciTech Connect

Pacific Northwest Laboratory (PNL) prepared this edition of the radioisotope customer list at the request of the Office of Health and Environmental Research (ER-73), Office of Energy Research, US Department of Energy (DOE). This is the 25th report in a series dating from 1964. This report covers DOE radioisotope sales and distribution activities by its facilities to domestic, foreign and other DOE facilities for FY 1988. The report is divided into five sections: radioisotope suppliers, facility contacts, and radioisotopes or services supplied; a list of customers, suppliers, and radioisotopes purchased; a list of radioisotopes purchased cross-referenced to customer numbers; geographic locations of radioisotope customers; and radioisotope sales and transfers -- FY 1988. Radioisotopes not previously reported in this series of reports were argon-37, arsenic-72, arsenic-73, bismuth-207, gadolinium-151, rhenium-188, rhodium-101, selenium-72, xenon-123 and zirconium-88. The total value of DOE radioisotope sales for FY 1988 was $11.1 million, an increase of 3% from FY 1987.

Van Houten, N.C.

1989-06-01

101

Miniature Radioisotope Thermoelectric Power Cubes  

NASA Technical Reports Server (NTRS)

Cube-shaped thermoelectric devices energized by a particles from radioactive decay of Cm-244 have been proposed as long-lived sources of power. These power cubes are intended especially for incorporation into electronic circuits that must operate in dark, extremely cold locations (e.g., polar locations or deep underwater on Earth, or in deep interplanetary space). Unlike conventional radioisotope thermoelectric generators used heretofore as central power sources in some spacecraft, the proposed power cubes would be small enough (volumes would range between 0.1 and 0.2 cm3) to play the roles of batteries that are parts of, and dedicated to, individual electronic-circuit packages. Unlike electrochemical batteries, these power cubes would perform well at low temperatures. They would also last much longer: given that the half-life of Cm-244 is 18 years, a power cube could remain adequate as a power source for years, depending on the power demand in its particular application.

Patel, Jagdish U.; Fleurial, Jean-Pierre; Snyder, G. Jeffrey; Caillat, Thierry

2004-01-01

102

Theoretical study on the selective emitter radioisotope micro battery  

Microsoft Academic Search

Radioisotope micro battery has the capability of meet the requirements of micropower. This paper investigated the two distinct parts and the structure characteristics of the selective emitter radioisotope micro battery. Compared with the conventional Back Surface Filed radioisotope micro battery, the selective emitter radioisotope micro battery has two distinct parts: (1) a deeply diffused region with high surface doping concentration

Xianggao Piao; Jinkui Chu; Peichao Wang; Limin Jian

2007-01-01

103

Hydrodynamics-assisted scalable production of boron nitride nanosheets and their application in improving oxygen-atom erosion resistance of polymeric composites  

NASA Astrophysics Data System (ADS)

Searching for a method for low-cost, easily manageable, and scalable production of boron nitride nanosheets (BNNSs) and exploring their novel applications are highly important. For the first time we demonstrate that a novel and effective hydrodynamics method, which involves multiple exfoliation mechanisms and thus leads to much higher yield and efficiency, can realize large-scale production of BNNSs. The exfoliation mechanisms that multiple fluid dynamics events contribute towards normal and lateral exfoliation processes could be applied to other layered materials. Up to ~95% of the prepared BNNSs are less than 3.5 nm thick with a monolayer fraction of ~37%. Compared to the conventional sonication and ball milling-based methods, the hydrodynamics method has the advantages of possessing multiple efficient ways for exfoliating BN, being low-cost and environmentally-friendly, producing high quality BNNSs in high yield and efficiency, and achieving concentrated BNNSs dispersions even in mediocre solvents. It is also shown for the first time that BNNSs can be utilized as fillers to improve the oxygen-atom erosion resistance of epoxy composites which are widely used for spacecraft in low earth orbit (LEO) where atom oxygen abounds. An addition of only 0.5 wt% BNNSs can result in a 70% decrease in the mass loss of epoxy composites after atom oxygen exposure equivalent to 160 days in an orbit of ~300 km. Overall, the demonstrated hydrodynamics method shows great potential in large-scale production of BNNSs in industry in terms of yield, efficiency, and environmental friendliness; and the innovative application of BNNSs to enhancing oxygen-atom erosion resistance of polymeric composites in space may provide a novel route for designing light spacecraft in LEO.Searching for a method for low-cost, easily manageable, and scalable production of boron nitride nanosheets (BNNSs) and exploring their novel applications are highly important. For the first time we demonstrate that a novel and effective hydrodynamics method, which involves multiple exfoliation mechanisms and thus leads to much higher yield and efficiency, can realize large-scale production of BNNSs. The exfoliation mechanisms that multiple fluid dynamics events contribute towards normal and lateral exfoliation processes could be applied to other layered materials. Up to ~95% of the prepared BNNSs are less than 3.5 nm thick with a monolayer fraction of ~37%. Compared to the conventional sonication and ball milling-based methods, the hydrodynamics method has the advantages of possessing multiple efficient ways for exfoliating BN, being low-cost and environmentally-friendly, producing high quality BNNSs in high yield and efficiency, and achieving concentrated BNNSs dispersions even in mediocre solvents. It is also shown for the first time that BNNSs can be utilized as fillers to improve the oxygen-atom erosion resistance of epoxy composites which are widely used for spacecraft in low earth orbit (LEO) where atom oxygen abounds. An addition of only 0.5 wt% BNNSs can result in a 70% decrease in the mass loss of epoxy composites after atom oxygen exposure equivalent to 160 days in an orbit of ~300 km. Overall, the demonstrated hydrodynamics method shows great potential in large-scale production of BNNSs in industry in terms of yield, efficiency, and environmental friendliness; and the innovative application of BNNSs to enhancing oxygen-atom erosion resistance of polymeric composites in space may provide a novel route for designing light spacecraft in LEO. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03714b

Yi, Min; Shen, Zhigang; Zhang, Wen; Zhu, Jinyang; Liu, Lei; Liang, Shuaishuai; Zhang, Xiaojing; Ma, Shulin

2013-10-01

104

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1986  

SciTech Connect

This document describes radioisotope distribution from DOE facilities to private firms including foreign and other DOE facilities. The information is divided into five sections: (1)isotope suppliers, facility contact, and isotopes or services supplied; (2) customers, suppliers, and isotopes purchased; (3) isotopes purchased cross-referenced with customer numbers; (4) geographic locations of radioisotope customers; and (5) radioisotope sales and transfers for fiscal year 1986.

Lamar, D.A.

1987-10-01

105

Serial coupling of RP and zwitterionic hydrophilic interaction LC-MS: suspects screening of diclofenac transformation products by oxidation with a boron-doped diamond electrode.  

PubMed

The presence of pollutants and their transformation products (TPs) in the water system is a big concern because of possible adverse effects on the aquatic environment. Their identification is still a challenge that requires the combination of different chromatographic techniques. In the current research, serial coupling of RPLC and zwitterionic hydrophilic interaction LC with TOF-MS was investigated as a single separation technique for the screening of suspected TPs from electrochemical oxidation of diclofenac using a boron-doped diamond electrode. Diclofenac oxidation was performed in three water matrices in order to study its transformation in different chemical contexts. 47 TPs resulting from similar oxidation methods were selected from the literature. As in most cases standards were not available, an identification procedure based on accurate mass data and chromatographic behavior was proposed. According to this procedure, 11 suspected TPs, previously analyzed by LC, GC, or ion chromatography, were detected in a single injection. The method was proved to be reliable and versatile and it could be efficiently employed as a comprehensive analytical tool for the simultaneous analysis of compounds in a wide polarity range. PMID:23857646

Rajab, Mohamad; Greco, Giorgia; Heim, Carolin; Helmreich, Brigitte; Letzel, Thomas

2013-09-01

106

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1984  

SciTech Connect

This edition of the radioisotope customer list was prepared at the request of the Office of Health and Environmental Research (ER-73), Office of Energy Research, Department of Energy (DOE). This document describes radioisotope distribution from DOE facilities to private firms including foreign and other DOE facilities. The information is divided into five sections: (1) isotope suppliers, facility contacts, and isotopes or services supplied; (2) customers, suppliers, and isotopes purchased; (3) isotopes purchased cross-referenced with customer numbers; (4) geographic locations of radioisotope customers; and (5) radioisotope sales and transfers - FY 1984.

Baker, D.A.

1985-08-01

107

List of DOE radioisotope customers with summary of radioisotope shipments, FY 1987  

SciTech Connect

This edition of the radioisotope customer list was prepared at the request of the Office of Health and Environmental Research (ER-73), Office of Energy Research, US Department of Energy (DOE). This document describes radioisotope distribution from DOE facilities to private firms, including foreign and other DOE facilities. The information is divided into five sections: 1) isotope suppliers, facility contact, and isotopes or services supplied; 2) customers, suppliers, and isotopes purchased; 3) isotopes purchased cross- referenced with customer numbers; 4) geographic locations of radioisotope customers; and 5) radioisotope sales and transfers for fiscal year 1987.

Lamar, D.A.; Van Houten, N.C.

1988-08-01

108

The prospects for composites based on boron fibers  

NASA Technical Reports Server (NTRS)

The fabrication of boron filaments and the production of composite materials consisting of boron filaments and organic or metallic matrices are discussed. Problem involving the use of tungsten substrates in the filament fabrication process, the protection of boron fibers with diffusion barrier cladings, and the application of alloy additives in the matrix to lessen the effects of diffusion are considered. Data on the kinetics of the boron fiber/matrix interaction at high temperatures, and the influence of the fiber/matrix interaction on the mechanical properties of the composite are presented.

Naslain, R.

1978-01-01

109

Advanced Radioisotope Power Systems Segmented Thermoelectric Research  

NASA Technical Reports Server (NTRS)

Flight times are long; - Need power systems with >15 years life. Mass is at an absolute premium; - Need power systems with high specific power and scalability. 3 orders of magnitude reduction in solar irradiance from Earth to Pluto. Nuclear power sources preferable. The Overall objective is to develop low mass, high efficiency, low-cost Advanced Radioisotope Power System with double the Specific Power and Efficiency over state-of-the-art Radioisotope Thermoelectric Generators (RTGs).

Caillat, Thierry

2004-01-01

110

Radioisotope thermoelectric generator licensed hardware package and certification tests  

NASA Astrophysics Data System (ADS)

This paper presents the Licensed Hardware package and the Certification Test portions of the Radioisotope Thermoelectric Generator Transportation System. This package has been designed to meet those portions of the Code of Federal Regulations (10 CFR 71) relating to 'Type B' shipments of radioactive materials. The detailed information for the anticipated license is presented in the safety analysis report for packaging, which is now in process and undergoing necessary reviews. As part of the licensing process, a full-size Certification Test Article unit, which has modifications slightly different than the Licensed Hardware or production shipping units, is used for testing. Dimensional checks of the Certification Test Article were made at the manufacturing facility. Leak testing and drop testing were done at the 300 Area of the US Department of Energy's Hanford Site near Richland, Washington. The hardware includes independent double containments to prevent the environmental spread of Pu-238, impact limiting devices to protect portions of the package from impacts, and thermal insulation to protect the seal areas from excess heat during accident conditions. The package also features electronic feed-throughs to monitor the Radioisotope Thermoelectric Generator's temperature inside the containment during the shipment cycle. This package is designed to safely dissipate the typical 4500 thermal watts produced in the largest Radioisotope Thermoelectric Generators. The package also contains provisions to ensure leak tightness when radioactive materials, such as a Radioisotope Thermoelectric Generator for the Cassini Mission, planned for 1997 by the National Aeronautics and Space Administration, are being prepared for shipment. These provisions include test ports used in conjunction with helium mass spectrometers to determine seal leakage rates of each containment during the assembly process.

Goldmann, L. H.; Averette, H. S.

1994-09-01

111

Metal-ceramics based on nanostructured boron carbide  

NASA Astrophysics Data System (ADS)

Boron carbide has unique physicochemical and mechanical properties such as: high modulus of elasticity, high value of a strength-to-density ratio, heightened wear-resistance in unfriendly environment, etc., however dense product of boron carbide is not widely used in the area of engineering due to low impact strength, brittleness and low thermal conductivity of this material. Recent efforts of the scientists working in this area are focused on creating the so-called hetero-modulus metal-ceramic composite materials comprised of high-modulus ceramic and a metallic phase as an elastic binder. Creation of effective boron carbide based hetero-modulus materials is possible when a) boron carbide has a high degree of dispersion; b) metallic binder has a high adhesion ability and low reactivity toward boron carbide. The technology developed for producing boron carbide based metal-ceramic materials provides pyrolysis (900-1100 °C) of the precursors comprised of amorphous boron, carbon-chain polymers and appropriate metal salts. Each particle of the obtained powder contains both - nanostructured components of boron carbide and of a binding metallic phase. The fabricated metal-ceramic product has heightened parameters of impact strength and thermal conductivity in parallel with the retained unique properties of boron carbide.

Antadze, M.; Chedia, R.; Tsagareishvili, O.; Mikeladze, A.; Gacheciladze, A.; Margiev, B.; Gabunia, D.; Tsuladze, T.; Khantadze, D.

2012-11-01

112

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

113

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

PubMed

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

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

2013-11-01

114

Inhomogeneous Big Bang Nucleosynthesis: Upper Limit on Omega_b and Production of Lithium, Beryllium, and Boron  

E-print Network

We examine the Big Bang nucleosynthesis (BBN) process in the presence of small-scale baryon inhomogeneities. Primordial abundance yields for D, He4, Li6, Li7, Be9, and B11 are computed for wide ranges of parameters characterizing the inhomogeneities taking account of all relevant diffusive and hydrodynamic processes. These calculations may be of interest due to (a) recent observations of the anisotropies in the cosmic microwave background radiation favoring slightly larger baryonic contribution to the critical density, Omega_b, than allowed by a standard BBN scenario and (b) new observational determinations of Li6 and Be9 in metal-poor halo stars. We find considerable parameter space in which production of D and He4 is in agreement with observational constraints even for Omega_b h^2 a factor 2-3 larger than the Omega_b inferred from standard BBN. Nevertheless, in this parameter space synthesis of Li7 in excess of the inferred Li7 abundance on the Spite plateau results. Production of Li6, Be9, and B11 in inhomogeneous BBN scenarios is still typically well below the abundance of these isotopes observed in the most metal-poor stars to date thus neither confirming nor rejecting inhomogeneous BBN. In an appendix we summarize results of a reevaluation of baryon diffusion constants entering inhomogeneous BBN calculations.

K. Jedamzik; Jan B. Rehm

2001-01-17

115

ADVANCED RADIOISOTOPE HEAT SOURCE AND PROPULSION SYSTEMS FOR PLANETARY EXPLORATION  

SciTech Connect

The exploration of planetary surfaces and atmospheres may be enhanced by increasing the range and mobility of a science platform. Fundamentally, power production and availability of resources are limiting factors that must be considered for all science and exploration missions. A novel power and propulsion system is considered and discussed with reference to a long-range Mars surface exploration mission with in-situ resource utilization. Significance to applications such as sample return missions is also considered. Key material selections for radioisotope encapsulation techniques are presented.

R. C. O'Brien; S. D. Howe; J. E. Werner

2010-09-01

116

A method for the deprotection of alkylpinacolyl boronate esters.  

PubMed

A two-step procedure for deprotection of alkylpinacolyl boronate esters via transesterification with diethanolamine followed by hydrolysis was successfully developed with the advantages of tolerance to various functional groups, short reaction time, and ease of product isolation. PMID:21449603

Sun, Jing; Perfetti, Michael T; Santos, Webster L

2011-05-01

117

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...

118

ILLUSTRATIONS OF RADIOISOTOPES--DEFINITIONS AND APPLICATIONS.  

ERIC Educational Resources Information Center

THIS PUBLICATION IS COMPOSED OF OVER 150 PAGES OF BLACK AND WHITE ILLUSTRATIONS DEALING WITH RADIOISOTOPES AND THEIR USES. THESE ILLUSTRATIONS CONSIST OF CHARTS, GRAPHS, AND PICTORIAL REPRESENTATIONS WHICH COULD BE PREPARED AS HANDOUTS, TRANSPARENCIES FOR OVERHEAD PROJECTION, OR WHICH COULD BE USED IN A NUMBER OF OTHER WAYS FOR PRESENTING SUCH…

Atomic Energy Commission, Oak Ridge, TN. Div. of Technical Information.

119

NASA Radioisotope Power Conversion Technology NRA Overview  

NASA Technical Reports Server (NTRS)

The focus of the National Aeronautics and Space Administration's (NASA) Radioisotope Power Systems (RPS) Development program is aimed at developing nuclear power and technologies that would improve the effectiveness of space science missions. The Radioisotope Power Conversion Technology (RPCT) NASA Research Announcement (NRA) is an important mechanism through which research and technology activities are supported in the Advanced Power Conversion Research and Technology project of the Advanced Radioisotope Power Systems Development program. The purpose of the RPCT NRA is to advance the development of radioisotope power conversion technologies to provide higher efficiencies and specific powers than existing systems. These advances would enable a factor of two to four decrease in the amount of fuel and a reduction of waste heat required to generate electrical power, and thus could result in more cost effective science missions for NASA. The RPCT NRA selected advanced RPS power conversion technology research and development proposals in the following three areas: innovative RPS power conversion research, RPS power conversion technology development in a nominal 100 W(sub e) scale; and, milliwatt/multi-watt RPS (mWRPS) power conversion research. Ten RPCT NRA contracts were awarded in 2003 in the areas of Brayton, Stirling, thermoelectric (TE), and thermophotovoltaic (TPV) power conversion technologies. This paper will provide an overview of the RPCT NRA, a summary of the power conversion technologies approaches being pursued, and a brief digest of first year accomplishments.

Anderson, David J.

2005-01-01

120

Radioisotope thermoelectric generator licensed hardware package and certification tests  

NASA Astrophysics Data System (ADS)

This paper presents the Licensed Hardware package and the Certification Test portions of the Radioisitope Themoelectric Generator Transportation System. This package has been designed to meet those portions of the Code of Federal Regulations (10 CFR 71) relating to ``Type B'' shipments of radioactive materials. The licensed hardware is now in the U. S. Department of Energy licensing process that certifies the packaging's integrity under accident conditions. The detailed information for the anticipated license is presented in the safety analysis report for packaging, which is now in process and undergoing necessary reviews. As part of the licensing process, a full-size Certification Test Article unit, which has modifications slightly different than the Licensed Hardware or production shipping units, is used for testing. Dimensional checks of the Certification Test Article were made at the manufacturing facility. Leak testing and drop testing were done at the 300 Area of the U.S. Department of Energy's Hanford Site near Richland, Washington. The hardware includes independent double containments to prevent the environmental spread of 238Pu, impact limiting devices to protect portions of the package from impacts, and thermal insulation to protect the seal areas from excess heat during accident conditions. The package also features electronic feed-throughs to monitor the Radioisotope Thermoelectric Generator's temperature inside the containment during the shipment cycle. This package is designed to safely dissipate the typical 4,500 thermal watts produced in the largest Radioisotope Thermoelectric Generators. The package also contains provisions to ensure leak tightness when radioactive materials, such as a Radioisotope Thermoelectric Generator for the Cassini Mission, planned for 1997 by the National Aeronautics and Space Administration, are being prepared for shipment. These provisions include test ports used in conjunction with helium mass spectrometers to determine seal leakage rates of each containment during the assembly process.

Goldmann, Louis H.; Averette, Henry S.

1995-01-01

121

Fine-tuning the nucleophilic reactivities of boron ate complexes derived from aryl and heteroaryl boronic esters.  

PubMed

Boron ate complexes derived from thienyl and furyl boronic esters and aryllithium compounds have been isolated and characterized by X-ray crystallography. Products and mechanisms of their reactions with carbenium and iminium ions have been analyzed. Kinetics of these reactions were monitored by UV/Vis spectroscopy, and the influence of the aryl substituents, the diol ligands (pinacol, ethylene glycol, neopentyl glycol, catechol), and the counterions on the nucleophilic reactivity of the boron ate complexes were examined. A Hammett correlation confirmed the polar nature of their reactions with benzhydrylium ions, and the correlation lg?k(20?°C)=sN (E+N) was employed to determine the nucleophilicities of the boron ate complexes and to compare them with those of other borates and boronates. The neopentyl and ethylene glycol derivatives were found to be 10(4) times more reactive than the pinacol and catechol derivatives. PMID:25604646

Berionni, Guillaume; Leonov, Artem I; Mayer, Peter; Ofial, Armin R; Mayr, Herbert

2015-02-23

122

Boron nitride housing cools transistors  

NASA Technical Reports Server (NTRS)

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

1965-01-01

123

Particle-beam accelerators for radiotherapy and radioisotopes  

SciTech Connect

The philosophy used in developing the new PIGMI technology was that the parameters chosen for physics research machines are not necessarily the right ones for a dedicated therapy or radioisotope machine. In particular, the beam current and energy can be optimized, and the design should emphasize minimum size, simplicity and reliability of operation, and economy in capital and operating costs. A major part of achieving these goals lay in raising the operating frequency and voltage gradient of the accelerator, which shrinks the diameter and length of the components. Several other technical innovations resulted in major system improvements. One of these is a radically new type of accelerator structure named the radio-frequency quadrupole (RFQ) accelerator. This allowed us to eliminate the large, complicated ion source used in previous ion accelerators, and to achieve a very high quality accelerated beam. Also, by using advanced permanent magnet materials to make the focusing elements, the system becomes much simpler. Other improvements have been made in all of the accelerator components and in the methods for operating them. These will be described, and design and costing information examples given for several possible therapy and radioisotope production machines.

Boyd, T.J.; Crandall, K.R.; Hamm, R.W.

1981-01-01

124

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

125

In Vivo Boron Uptake Determination for Boron Neutron Capture Synovectomy  

SciTech Connect

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

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

1999-06-06

126

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

SciTech Connect

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

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

2006-11-13

127

Microfabricated radioisotope-powered active RFID transponder  

Microsoft Academic Search

We demonstrate a microfabricated 63Ni radioisotope-powered RFID transponder realized with a SAW (surface acoustic wave) device as the transmission frequency selector. The transponder is powered by a 1.5 milli-Ci 63Ni source which has a half-life of 100 years. We have achieved a 5mW, 10-¿s long, 100MHz carrier envelope, RF pulses which occur every 3 minutes, across a 50¿ load. The

S. Tin; A. Lal

2009-01-01

128

The role of hydrothermal fluids in the production of subduction zone magmas: Evidence from siderophile and chalcophile trace elements and boron  

NASA Astrophysics Data System (ADS)

In order to evaluate the processes responsible for the enrichments of certain siderophile/ chalcophile trace elements during the production of subduction-related magmas, representative lavas from seven subduction zones have been analyzed for Pb, As, Sb, Sn, W, Mo, Tl, Cu, and Zn by inductively coupled plasma-mass spectrometry (ICP-MS), radiochemical epithermal neutron activation analysis (RENA), and atomic absorption (AA). The siderophile/chalcophile elements are compared to the highly fluid-mobile element B, the light rare earth elements (LREEs), U, and Th in order to place constraints on their behavior in subduction zones. Boron, As, Sb, and Pb are all enriched in arc lavas and continental crustal rocks more so than expected assuming normal magmatic processes (melting and crystallization). Tin, W, and Mo show little evidence of enrichment. Correlations of Pb/Ce, As/Ce, and Sb/Ce with B/La are statistically significant and have high correlation coefficients (and, more importantly, slopes approaching one) suggesting that Pb, As, and Sb behave similarly to B (i.e., that they are fluid-mobile). In addition, across-arc traverses show that B/La, As/Ce, Pb/Ce, and Sb/Ce ratios decrease dramatically with distance towards the back-arc basin. W/Th, Tl/La, Sn/Sm, and Mo/Ce ratios and Cu and Zn concentrations have much less systematic across-arc variations and correlations with B/La are not as strong (and in some cases, not statistically significant) and the regression lines have much lower slopes. Mixing models between upper mantle, slab-derived fluid, and sediment are consistent with a fluid-derived component in the arcs displaying extra enrichments of B, Pb, As, and Sb. These observations imply efficient mobilization of B, Pb, As, Sb, and possibly Tl into arc magma source regions by hydrothermal fluids derived from metamorphic dehydration reactions within the slab. Tin, W, and Mo show little, if any, evidence of hydrothermal mobilization. Copper appears to be slightly enriched in arc lavas relative to mid-ocean ridge basalts (MORBs) whereas Zn contents of arc lavas, MORB, ocean island basalts (OIBs), and continental crustal samples are similar suggesting that the bulk partition coefficient for Zn is approximately equal to one. However, Zn contents of the upper mantle are lower than these reservoirs implying an enrichment of the source region in Zn prior to melting. These nonigneous enrichments have implications not only for arc magma genesis but also for continental crust formation and crust-mantle evolution. The mobility of Pb, As, Sb, and B in hot, reducing, acidic hydrothermal fluids may be greatly enhanced relative to the large-ion lithophile elements (LILEs; including U) as a result of HS -, H 2S, OH -, or other types of complexing. In the case of Pb, continued transport of Pb from subducted slabs into arc magma source regions throughout Earth history coupled with a U fluxing of the mantle a the end of the Archean may account for the depletion of Pb in the upper mantle, the low U/Pb of most arc volcanics and continental crustal rocks, and provide an explanation for the Pb- Paradox (Hofmann et al., 1986;McCulloch, 1993;Miller et al., 1994). Recycled slabs will then retain high U/Pb ratios upon entering the deep mantle and may eventually become incorporated into the source regions of many OIBs; some with HIMU (high 238U/ 204Pb) signatures.

Noll, P. D.; Newsom, H. E.; Leeman, W. P.; Ryan, J. G.

1996-02-01

129

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

130

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

Microsoft Academic Search

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

Tareq Abu-Hamed; Jacob Karni; Michael Epstein

2007-01-01

131

Process for microwave sintering boron carbide  

DOEpatents

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

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

1993-01-01

132

Medical Radioisotope Data Survey: 2002 Preliminary Results  

SciTech Connect

A limited, but accurate amount of detailed information about the radioactive isotopes used in the U.S. for medical procedures was collected from a local hospital and from a recent report on the U.S. Radiopharmaceutical Markets. These data included the total number of procedures, the specific types of procedures, the specific radioisotopes used in these procedures, and the dosage administered per procedure. The information from these sources was compiled, assessed, pruned, and then merged into a single, comprehensive and consistent set of results presented in this report. (PIET-43471-TM-197)

Siciliano, Edward R.

2004-06-23

133

Radioisotope microbattery based on liquid semiconductor  

NASA Astrophysics Data System (ADS)

A liquid semiconductor-based radioisotope micropower source has been pioneerly developed. The semiconductor property of selenium was utilized along with a 166 MBq radioactive source of S35 as elemental sulfur. Using a liquid semiconductor-based Schottky diode, electrical power was distinctively generated from the radioactive source. Energetic beta radiations in the liquid semiconductor can produce numerous electron hole pairs and create a potential drop. The measured power from the microbattery is 16.2 nW with an open-circuit voltage of 899 mV and a short-circuit of 107.4 nA.

Wacharasindhu, T.; Kwon, J. W.; Meier, D. E.; Robertson, J. D.

2009-07-01

134

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

135

NASA Radioisotope Power Systems Program Update  

NASA Astrophysics Data System (ADS)

The use of Radioisotope Power Systems (RPS) represents a critical capability for exploration of the Solar System. RPS have been used for decades to power deep space missions and sometimes for the operation of landers or rovers on Mars. Modest power needs (<~1 KWe) for regions relatively far from the Sun (~>5 AU) make them attractive, and, in most cases, essential for a variety of missions. Even close by, such as on the surface of the Moon or Mars, RPS enhances operational capability. NASA's strategic planning now contemplates more ambitious missions than those of the past, with the likelihood of increasingly severe or more diverse environments in which to contend. We are at a crossroads in the application of radioisotope power, thanks partially to progress made, but also due to the realities of budget constraints and the availability of plutonium-238 fuel. Within a few years, investments in power conversion technologies could yield next generation flight systems with capability for multiple environments, and improved efficiency and specific power. However, for RPS, given the demands on reliability and system longevity (15+years), infusion of any new RPS technology is the challenge. We review progress made during the past year in development of RPS and note applications in NASA's Science Plan (2007).

Harmon, B. Alan; Lavery, David B.

2008-01-01

136

Rhenium Radioisotopes for Therapeutic Radiopharmaceutical Development  

SciTech Connect

The availability of therapeutic radioisotopes at reasonable costs is important for applications in nuclear medicine, oncology and interventional cardiology, Rhenium-186 (Re-186) and rhenium-1 88 (Re-188) are two reactor-produced radioisotope which are attractive for a variety of therapeutic applications, Rhenium-186 has a half-life of 90 hours and decays with emission of a &particle with a maximum energy of 1.08 MeV and a 135 keV (9Yo) gamma which permits imaging. In contrast, Re- 188 has a much shorter half-life of 16.9 hours and emits a p-particle with a much higher energy of 2.12 MeV (Em=) and a 155 keV gamma photon (15Yo) for imaging. While Re-186 is unavailable from a generator system and must be directly produced in a nuclear reactor, Re-188 can also be directly produced in a reactor with high specific activity, but is more conveniently and cost-effectively available as carrier-free sodium perrhenate by saline elution of the alumina-based tungsten-188 (W1 88)/Re-l 88 generator system [1-2]. Since a comprehensive overviewofRe-186 and Re-188 therapeutic agents is beyond the scope of this &tended Abstrac4 the goal is to provide key examples of various agents currently in clinical use and those which are being developed for important clinical applications.

Beets, A.L.; Knapp, F.F., Jr.; Kropp, J.; Lin, W.-Y.; Pinkert, J.; Wang, S.-Y.

1999-01-18

137

Reliability Issues in Stirling Radioisotope Power Systems  

NASA Technical Reports Server (NTRS)

Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

Shah, Ashwin R.; Schreiber, Jeffrey G.

2004-01-01

138

RADIOISOTOPE EXPERIMENTS IN HIGH SCHOOL BIOLOGY, AN ANNOTATED SELECTED BIBLIOGRAPHY.  

ERIC Educational Resources Information Center

SELECTED REFERENCES ON THE USE OF RADIOISOTOPES IN BIOLOGY ARE CONTAINED IN THIS ANNOTATED BIBLIOGRAPHY FOR SECONDARY SCHOOL STUDENTS. MATERIALS INCLUDED WERE PUBLISHED AFTER 1960 AND DEAL WITH THE PROPERTIES OF RADIATION, SIMPLE RADIATION DETECTION PROCEDURES, AND TECHNIQUES FOR USING RADIOISOTOPES EXPERIMENTALLY. THE REFERENCES ARE LISTED IN…

HURLBURT, EVELYN M.

139

Radioisotope Reduction Using Solar Power for Outer Planetary Missions  

Microsoft Academic Search

Radioisotope power systems have historically been (and still are) the power system of choice from a mass and size perspective for outer planetary missions. High demand for and limited availability of radioisotope fuel has made it necessary to investigate alternatives to this option. Low mass, high efficiency solar power systems have the potential for use at low outer planetary temperatures

James Fincannon

2008-01-01

140

Multi-mission radioisotope thermoelectric generator (MMRTG) program overview  

Microsoft Academic Search

Future NASA missions require safe, reliable, long-lived power systems for surface exploration of planetary bodies such as Mars as well as exploration of the solar system in the vacuum of space beyond Earth orbit. To address this need, the Department of Energy and NASA have initiated the development of radioisotope power systems, including the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). In

Fred Ritz; C. E. Peterson

2004-01-01

141

Advanced radioisotope power sources for future deep space missions  

Microsoft Academic Search

The use of Radioisotope Thermoelectric Generators (RTGs) has been well established for deep space mission applications. The success of the Voyager, Galileo, Cassini and numerous other missions proved the efficacy of these technologies in deep space. Future deep space missions may also require Advanced Radioisotope Power System (ARPS) technologies to accomplish their goals. In the Exploration of the Solar System

Erik N. Nilsen

2001-01-01

142

In situ boron nitride coating and comparison with existing boronizations  

NASA Astrophysics Data System (ADS)

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

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

1992-12-01

143

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

144

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

145

Status of the NASA Stirling Radioisotope Project  

NASA Technical Reports Server (NTRS)

Free-piston Stirling power conversion has been considered a candidate for radioisotope power systems for space for more than a decade. Prior to the free-piston Stirling architecture, systems were designed with kinematic Stirling engines that used linkages and rotary alternators to convert heat to electricity. These systems were able to achieve long life by lightly loading the linkages; however, the live was nonetheless limited. When the free-piston configuration was initially proposed, it was thought to be attractive due to the relatively high conversion efficiency, acceptable mass, and the potential for long life and high reliability based on wear-free operation. These features have consistently been recognized by teams that have studied technology options for radioisotope space power systems. Since free-piston Stirling power conversion was first considered for space power applications, there have been major advances in three general areas of development: hardware that has demonstrated long-life and reliability, the success achieved by Stirling cryocoolers in space, and the overall developmental maturity of the technology for both space and terrestrial applications. Based on these advances, free-piston Stirling convertors are currently being developed for space power, and for a number of terrestrial applications. They commonly operate with the power, efficiency, life, and reliability as intended, and much of the development now centers on system integration. This paper will summarize the accomplishments of free-piston Stirling power conversion technology over the past decade, review the status of development with regard to space power, and discuss the challenges that remain.

Schreiber, Jeffrey G.

2007-01-01

146

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

147

Phosphorus-containing derivatives of decaboranes(14) as precursors of boron-containing materials. Technical report  

SciTech Connect

Ceramic materials whose properties are attractive for high-technology applications often fail to realize their full potential of usefulness due to an inability to be fabricated into complex, durable shapes. One such class of materials is that of the boron-containing ceramics, e.g., boron carbide, boron nitride, boron phosphides, aluminum boride, and boron silicides. The authors report the results of an effort to extend the use of preceramic polymers to boron-containing materials. The motivation for this work was to utilize processable materials which give, in general, boron carbide as the major ceramic phase upon pyrolysis. A route to soluble boron-containing polymers has been developed. The synthesis and characterization of phosphorus-containing monomeric and polymeric derivatives of decaborane (B/sub 10/H/sub 14/) are given. Preparation and characterization of boron-containing ceramic materials from these molecular and macromolecular species are discussed. Success was achieved in the areas of ceramic-fiber and monolith production and in the area of binder applications for composites of advanced ceramic materials.

Rees, W.S. Jr.; Seyferth, D.

1988-06-25

148

Radioisotope Reduction Using Solar Power for Outer Planetary Missions  

NASA Technical Reports Server (NTRS)

Radioisotope power systems have historically been (and still are) the power system of choice from a mass and size perspective for outer planetary missions. High demand for and limited availability of radioisotope fuel has made it necessary to investigate alternatives to this option. Low mass, high efficiency solar power systems have the potential for use at low outer planetary temperatures and illumination levels. This paper documents the impacts of using solar power systems instead of radioisotope power for all or part of the power needs of outer planetary spacecraft and illustrates the potential fuel savings of such an approach.

Fincannon, James

2008-01-01

149

Report on audit of funding for advanced radioisotope power systems  

SciTech Connect

The U.S. Department of Energy`s (Department) Advanced Radioisotope Power Systems Program maintains the sole national capability and facilities to produce radioisotope power systems for the National Aeronautics and Space Administration (NASA), the Department of Defense, and other Federal agencies. Projects are conducted with these agencies in accordance with written agreements and are dependent on cost sharing by the user agencies. For the past seven years the program emphasis has been on providing power systems for NASA`s Cassini mission to Saturn, which was launched earlier this month. We initiated this audit to determine whether the Department received proper reimbursement from NASA for the radioisotope power systems produced.

NONE

1997-10-17

150

Semiconducting icosahedral boron arsenide crystal growth for neutron detection  

NASA Astrophysics Data System (ADS)

Semiconducting icosahedral boron arsenide, B12As2, is an excellent candidate for neutron detectors, thermoelectric converters, and radioisotope batteries, for which high quality single crystals are required. Thus, the present study was undertaken to grow B12As2 crystals by precipitation from metal solutions (nickel) saturated with elemental boron (or B12As2 powder) and arsenic in a sealed quartz ampoule. B12As2 crystals of 10-15 mm were produced when a homogeneous mixture of the three elements was held at 1150 °C for 48-72 h and slowly cooled (3.5 °C/h). The crystals varied in color and transparency from black and opaque to clear and transparent. X-ray topography (XRT), and elemental analysis by energy dispersive X-ray spectroscopy (EDS) confirmed that the crystals had the expected rhombohedral structure and chemical stoichiometry. The concentrations of residual impurities (nickel, carbon, etc.) were low, as measured by Raman spectroscopy and secondary ion mass spectrometry (SIMS). Additionally, low etch-pit densities (4.4×107 cm-2) were observed after etching in molten KOH at 500 °C. Thus, the flux growth method is viable for growing large, high-quality B12As2 crystals.

Whiteley, C. E.; Zhang, Y.; Gong, Y.; Bakalova, S.; Mayo, A.; Edgar, J. H.; Kuball, M.

2011-03-01

151

Nuclear energy in the service of biomedicine: the U.S. Atomic Energy Commission's radioisotope program, 1946-1950.  

PubMed

The widespread adoption of radioisotopes as tools in biomedical research and therapy became one of the major consequences of the "physicists' war" for postwar life science. Scientists in the Manhattan Project, as part of their efforts to advocate for civilian uses of atomic energy after the war, proposed using infrastructure from the wartime bomb project to develop a government-run radioisotope distribution program. After the Atomic Energy Bill was passed and before the Atomic Energy Commission (AEC) was formally established, the Manhattan Project began shipping isotopes from Oak Ridge. Scientists and physicians put these reactor-produced isotopes to many of the same uses that had been pioneered with cyclotron-generated radioisotopes in the 1930s and early 1940s. The majority of early AEC shipments were radioiodine and radiophosphorus, employed to evaluate thyroid function, diagnose medical disorders, and irradiate tumors. Both researchers and politicians lauded radioisotopes publicly for their potential in curing diseases, particularly cancer. However, isotopes proved less successful than anticipated in treating cancer and more successful in medical diagnostics. On the research side, reactor-generated radioisotopes equipped biologists with new tools to trace molecular transformations from metabolic pathways to ecosystems. The U.S. government's production and promotion of isotopes stimulated their consumption by scientists and physicians (both domestic and abroad), such that in the postwar period isotopes became routine elements of laboratory and clinical use. In the early postwar years, radioisotopes signified the government's commitment to harness the atom for peace, particularly through contributions to biology, medicine, and agriculture. PMID:17575955

Creager, Angela N H

2006-01-01

152

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

PubMed

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

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

1986-04-01

153

Thermal Model Predictions of Advanced Stirling Radioisotope Generator Performance  

NASA Technical Reports Server (NTRS)

This presentation describes the capabilities of three-dimensional thermal power model of advanced stirling radioisotope generator (ASRG). The performance of the ASRG is presented for different scenario, such as Venus flyby with or without the auxiliary cooling system.

Wang, Xiao-Yen J.; Fabanich, William Anthony; Schmitz, Paul C.

2014-01-01

154

Comparison of elemental boron and boron halide implants into silicon  

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

155

The Light-Weight Radioisotope Heater Unit (LWRHU): Development and application  

NASA Astrophysics Data System (ADS)

Radioisotope power sources have a long history of use in the American space program, both as components of radioisotope thermoelectric generators (RTGs), and as stand alone thermal power units. The primary goal of the LWRHU program was to develop a compact, second generation heat source that would offer improved performance and safety over previous radioisotope power units. The design objective fell into two categories: those relating to performance, such as thermal power, mass, lifetime, neutron emission, surface temperature, and thermodynamic stability; and those requirements related to safety, such as impact resistance, temperature resistance, corrosion resistance, and ablation control. The LWRHU program resulted in the design, development, and production of an improved, compact heat source suited for use in a variety of space missions. On the basis of the data generated during performance and safety verification testing, 100 LWRHUs were installed on the Galileo spacecraft. The extensive body of test data also makes the LWRHU a candidate for use in future civilian and military space missions.

George, T. G.; Tate, R. E.; Cull, T. A.

156

Implanted artificial heart with radioisotope power source.  

PubMed

An atomic artificial heart for orthotopic implantation was developed with the following characteristics: volume, 1.2 L; weight, 1.5 kg; radioisotope power, 45 W; operating life, up to 5 years; hemodynamics, similar to natural hemodynamics. The artificial heart includes a thermal drive with systems for regulating power, feeding steam into the cylinders, return of the condensate to the steam generator, and delivery of power to the ventricles and heat container. The artificial heart is placed in an artificial pericardium partially filled with physiologic solution. It uses a steam engine with two operating cylinders that separately drive the left and right ventricles. There is no electronic control system in the proposed design. The operation of the heat engine is controlled, with preservation of autoregulation by the vascular system of the body. The separate drives for the ventricles is of primary importance as it provides for operation of the artificial heart through control of cardiac activity by venous return. Experimental testing on a hydromechanical bench demonstrated effective autoregulation. PMID:6838394

Shumakov, V I; Griaznov, G M; Zhemchuzhnikov, G N; Kiselev, I M; Osipov, A P

1983-02-01

157

Reliability of Radioisotope Stirling Convertor Linear Alternator  

NASA Technical Reports Server (NTRS)

Onboard radioisotope power systems being developed and planned for NASA s deep-space missions would require reliable design lifetimes of up to 14 years. Critical components and materials of Stirling convertors have been undergoing extensive testing and evaluation in support of a reliable performance for the specified life span. Of significant importance to the successful development of the Stirling convertor is the design of a lightweight and highly efficient linear alternator. Alternator performance could vary due to small deviations in the permanent magnet properties, operating temperature, and component geometries. Durability prediction and reliability of the alternator may be affected by these deviations from nominal design conditions. Therefore, it is important to evaluate the effect of these uncertainties in predicting the reliability of the linear alternator performance. This paper presents a study in which a reliability-based methodology is used to assess alternator performance. The response surface characterizing the induced open-circuit voltage performance is constructed using 3-D finite element magnetic analysis. Fast probability integration method is used to determine the probability of the desired performance and its sensitivity to the alternator design parameters.

Shah, Ashwin; Korovaichuk, Igor; Geng, Steven M.; Schreiber, Jeffrey G.

2006-01-01

158

Neutron detectors comprising boron powder  

SciTech Connect

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

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

2013-05-21

159

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

SciTech Connect

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

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

1994-07-01

160

Development of a radioisotope heat source for the two-watt radioisotope thermoelectric generator  

NASA Astrophysics Data System (ADS)

Described is a radioisotope heat source for the Two-Watt Radioisotope Thermoelectric Generator (RTG) which is being considered for possible application by the U.S. Navy and for other Department of Defense applications. The heat source thermal energy (75 Wt) is produced from the alpha decay of plutonium-238 which is in the form of high-fired plutonium dioxide. The capsule is non-vented and consists of three domed cylindrical components each closed with a corresponding sealed end cap. Surrounding the fuel is the liner component, which is fabricated from a tantalum-based alloy, T-111. Also fabricated from T-111 is the next component, the strength member, which serves to meet pressure and impact criteria. The outermost component, or clad, is the oxidation- and corrosion-resistant nickel-based alloy, Hastelloy S. This paper defines the design considerations, details the hardware fabrication and welding processes, discusses the addition of yttrium to the fuel to reduce liner embrittlement, and describes the testing that has been conducted or is planned to assure that there is fuel containment not only during the heat source operational life, but also in case of an accident environment.

Howell, Edwin I.; McNeil, Dennis C.; Amos, Wayne R.

1992-01-01

161

Boron and Iron in AV 304: A B-dwarf in the SMC  

NASA Astrophysics Data System (ADS)

An upper limit in the boron abundance in AV 304 is determined as a test of cosmic ray spallation as the production of boron. Boron is determined from the B III resonance line at 2066 A from HST STIS data. AV 304 does not show signs of mixing or mass loss, which can destroy the fragile boron atom. The abundance othe boron seed nucleus, oxygen, is also well known in this star, and O is approximately the same from location to location in the SMC. Thus, the boron abundance from AV 304 should be representative of the abundance in ththe entire galaxy. We find an upper limit of 12+log(B/H)=1.7. This boron upper limit is lower than the oxygen depletion relative to the solar neighborhood by 0.3 dex. This is unlike the Galactic studies that suggest that boron scales linearly with oxygen. Additionally, the numerous Fe-group elements in the UV spectrum allows for a detailed Fe-group abundance determination. We find 12+log(Fe/H)=0.7+/-0.1, primarily from Fe III lines. The abundance is in excellent agreement with determinations from Fe I and Fe II lines in A-K supergiants in the SMC, and supports that O and Fe have the same underabundance in the SMC. We appreciate support for this project from NASA GO-08661, and Clare Boothe Luce research funds.

Brooks, A. M.; Venn, K. A.; Lambert, D. L.; Lemke, M.

2001-11-01

162

Considerations in the fabrication, assembly, and testing of radioisotopic thermo-photovoltaic (RTPV) generators for future space missions  

SciTech Connect

To increase energy output with a smaller size and mass than the radioisotopic thermoelectric generators (RTGs) that were previously used on deep space missions, a radioisotopic thermophotovoltaic (RTPV) system is being developed for the {open_quote}{open_quote}Pluto Express{close_quote}{close_quote} flyby mission. To minimize cost and development time, some facilities and components currently used for RTG production can be used to produce RTPVs. Production options also include out-sourcing and use of off-the-shelf hardware. Necessary modifications to tooling, production equipment, testing and shipping methods can be achieved in a timely manner so that the RTPV will be ready well before the planned launch of {open_quote}{open_quote}Pluto Express.{close_quote}{close_quote} {copyright} {ital 1996 American Institute of Physics.}

Barklay, C.D.; Miller, R.G. [EG& G Mound Applied Technologies, P.O. Box 3000, Miamisburg, Ohio 45343-3000 (United States); Frazier, T.A. [US Department of Energy, P.O. Box 66, Miamisburg, Ohio 45343-0066 (United States)

1996-03-01

163

Boron doped nanostructured diamond films  

NASA Astrophysics Data System (ADS)

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

Liang, Qi

164

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

Microsoft Academic Search

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

George W. Kabalka; Mark Davis; Peter Bendel

1988-01-01

165

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

166

Synthesis and photocurrent of amorphous boron nanowires.  

PubMed

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

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

2014-08-22

167

Synthesis of ?- and ?-Rhombohedral Boron Powders via Gas Phase Thermal Dissociation of Boron Trichloride by Hydrogen  

NASA Astrophysics Data System (ADS)

The ?-rhombohedral and ?-rhombohedral crystal structures of pure elemental boron powders have been synthesized via gas phase thermal dissociation of BCl3 by H2 on a quartz substrate. The parameters affecting the crystal structures of the final products and the process efficiency, such as BCl3/H2 molar ratio (1/2 and 1/4) and reaction temperature (1173 K to 1373 K [900 °C to 1100 °C]), have been examined. The experimental apparatus of original design has enabled boron powders to be obtained at temperatures lower than those in the literature. The surface/powder separation problem encountered previously with different substrate materials has been avoided. Boron powders have been synthesized with a minimum purity of 99.99 pct after repeated HF leaching. The qualitative analysis of exhaust gases has been conducted using a Fourier transform infrared spectroscope (FTIR). The synthesized powders have been characterized using an X-ray powder diffractometer (XRD) and scanning electron microscope (SEM) techniques. The results of the reactions have been compared with equilibrium predictions performed using the FactSage 6.2 (Center for Research in Computational Thermochemistry, Montreal, Canada) thermochemical software.

A?ao?ullar?, Duygu; Balc?, Özge; Duman, Ismail; Öveço?lu, M. Lütfi

2011-06-01

168

NASA Radioisotope Power System Program - Technology and Flight Systems  

NASA Technical Reports Server (NTRS)

NASA sometimes conducts robotic science missions to solar system destinations for which the most appropriate power source is derived from thermal-to-electrical energy conversion of nuclear decay of radioactive isotopes. Typically the use of a radioisotope power system (RPS) has been limited to medium and large-scale missions, with 26 U,S, missions having used radioisotope power since 1961. A research portfolio of ten selected technologies selected in 2003 has progressed to a point of maturity, such that one particular technology may he considered for future mission use: the Advanced Stirling Converter. The Advanced Stirling Radioisotope Generator is a new power system in development based on this Stirling cycle dynamic power conversion technology. This system may be made available for smaller, Discovery-class NASA science missions. To assess possible uses of this new capability, NASA solicited and funded nine study teams to investigate unique opportunities for exploration of potential destinations for small Discovery-class missions. The influence of the results of these studies and the ongoing development of the Advanced Stirling Radioisotope Generator system are discussed in the context of an integrated Radioisotope Power System program. Discussion of other and future technology investments and program opportunities are provided.

Sutliff, Thomas J.; Dudzinski, Leonard A.

2009-01-01

169

NASA's Advanced Radioisotope Power Conversion Technology Development Status  

NASA Technical Reports Server (NTRS)

NASA's Advanced Radioisotope Power Systems (ARPS) project is developing the next generation of radioisotope power conversion technologies that will enable future missions that have requirements that cannot be met by either photovoltaic systems or by current radioisotope power systems (RPSs). Requirements of advanced RPSs include high efficiency and high specific power (watts/kilogram) in order to meet future mission requirements with less radioisotope fuel and lower mass so that these systems can meet requirements for a variety of future space applications, including continual operation surface missions, outer-planetary missions, and solar probe. These advances would enable a factor of 2 to 4 decrease in the amount of fuel required to generate electrical power. Advanced RPS development goals also include long-life, reliability, and scalability. This paper provides an update on the contractual efforts under the Radioisotope Power Conversion Technology (RPCT) NASA Research Announcement (NRA) for research and development of Stirling, thermoelectric, and thermophotovoltaic power conversion technologies. The paper summarizes the current RPCT NRA efforts with a brief description of the effort, a status and/or summary of the contractor's key accomplishments, a discussion of upcoming plans, and a discussion of relevant system-level benefits and implications. The paper also provides a general discussion of the benefits from the development of these advanced power conversion technologies and the eventual payoffs to future missions (discussing system benefits due to overall improvements in efficiency, specific power, etc.).

Anderson, David J.; Sankovic, John; Wilt, David; Abelson, Robert D.; Fleurial, Jean-Pierre

2007-01-01

170

Evaluation of medical isotope production with the accelerator production of tritium (APT) facility  

SciTech Connect

The accelerator production of tritium (APT) facility, with its high beam current and high beam energy, would be an ideal supplier of radioisotopes for medical research, imaging, and therapy. By-product radioisotopes will be produced in the APT window and target cooling systems and in the tungsten target through spallation, neutron, and proton interactions. High intensity proton fluxes are potentially available at three different energies for the production of proton- rich radioisotopes. Isotope production targets can be inserted into the blanket for production of neutron-rich isotopes. Currently, the major production sources of radioisotopes are either aging or abroad, or both. The use of radionuclides in nuclear medicine is growing and changing, both in terms of the number of nuclear medicine procedures being performed and in the rapidly expanding range of procedures and radioisotopes used. A large and varied demand is forecast, and the APT would be an ideal facility to satisfy that demand.

Benjamin, R.W. [Westinghouse Savannah River Company, Aiken, SC (United States); Frey, G.D.; McLean, D.C., Jr; Spicer, K.M.; Davis, S.E.; Baron, S.; Frysinger, J.R. [Medical Univ. of South Carolina, Charleston, SC (United States); Blanpied, G.; Adcock, D. [South Carolina Univ., Columbia, SC (United States)

1997-07-10

171

Boron in Presolar Silicon Carbide Grains from Supernovae  

NASA Astrophysics Data System (ADS)

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

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

2001-04-01

172

Mineral resource of the month: boron  

USGS Publications Warehouse

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

Lyday, Phyllis A.

2005-01-01

173

Communications CVD Growth of Boron Nitride Nanotubes  

E-print Network

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

174

Hair radioactivity as a measure of exposure to radioisotopes  

NASA Technical Reports Server (NTRS)

Since many radioisotopes accumulate in hair, this tropism was investigated by comparing the radioactivity of shaved with plucked hair collected from rats at various time intervals up to 24 hrs after intravenous injection of the ecologically important radioisotopes, iodine-131, manganese-54, strontium-85, and zinc-65. The plucked hair includes the hair follicles where biochemical transformations are taking place. The data indicate a slight surge of each radioisotpe into the hair immediately after injection, a variation of content of each radionuclide in the hair, and a greater accumulation of radioactivity in plucked than in shaved hair. These results have application not only to hair as a measure of exposure to radioisotopes, but also to tissue damage and repair at the hair follicle.

Strain, W. H.; Pories, W. J.; Fratianne, R. B.; Flynn, A.

1972-01-01

175

Luminescent materials: locking ?-conjugated and heterocyclic ligands with boron(III).  

PubMed

Multidisciplinary research on novel organic luminescent dyes is propelled by potential applications in plastic electronics and biomedical sciences. The construction of sophisticated fluorescent dyes around a tetrahedral boron(III) center is a particular approach that has fueled the creativity of chemists. Success in this enterprise has been readily achieved with simple synthetic protocols, the products of which display unusual spectroscopic behavior. This account is a critical review of recent advances in the field of boron(III) complexes (excluding BODIPYs and acetylacetonate boron complexes) involving species displaying similar coordination features, and we outline their potential development in several disciplines. PMID:24482312

Frath, Denis; Massue, Julien; Ulrich, Gilles; Ziessel, Raymond

2014-02-24

176

Intraoperative Subareolar Radioisotope Injection for Immediate Sentinel Lymph Node Biopsy  

PubMed Central

Objective: To determine the identification of sentinel lymph node biopsy (SLNB) in breast cancer patients after intraoperative injection of unfiltered technetium-99m sulfur colloid (Tc-99) and blue dye. Background: SLNB guided by a combination of radioisotope and blue dye injection yields the best identification rates in breast cancer patients. Radioisotope is given preoperatively, without local anesthesia, whereas blue dye is given intraoperatively. We hypothesized that, because of the rapid drainage noted with the subareolar injection technique of radioisotope, intraoperative injection would be feasible and less painful for SLN localization in breast cancer patients. Methods: Intraoperative injection of Tc-99 and confirmation blue dye was performed using the subareolar technique for SLNB in patients with operable breast cancer. The time lapse between injection and axillary incision, the background count, the preincision and ex vivo counts of the hot nodes, and the axillary bed counts were documented. The identification rate was recorded. Results: Ninety-six SLNB procedures were done in 88 patients with breast cancer employing intraoperative subareolar injection technique for both radioisotope (all 96 procedures) and blue dye (93 procedures) injections. Ninety-three (97%) procedures had successful identification; all SLNs were hot; 91 (of 93 procedures with blue dye) were blue and hot. The mean time from radioisotope injection to incision was 19.9 minutes (SD 8.5 minutes). The mean highest 10 second count was 88,544 (SD 55,954). Three of 96 (3%) patients with failure of localization had previous excisional biopsies: 1 circumareolar and 2 upper outer quadrant incisions that may have disrupted the lymphatic flow. Conclusion: Intraoperative subareolar injection of radioisotope rapidly drains to the SLNs and allows immediate staging of the axilla, avoiding the need to coordinate diagnostic services and a painful preoperative procedure. PMID:15166963

Layeeque, Rakhshanda; Kepple, Julie; Henry-Tillman, Ronda S.; Adkins, Laura; Kass, Rena; Colvert, Maureen; Gibson, Regina; Mancino, Anne; Korourian, Soheila; Klimberg, V Suzanne

2004-01-01

177

Procurement of a fully licensed radioisotope thermoelectric generator transportation system  

SciTech Connect

A fully licensed transportation system for Radioisotope Thermoelectric Generators and Light-Weight Radioisotope Heater Units is currently being designed and built. The system will comply with all applicable US Department of Transportation regulations without the use of a DOE Alternative.'' The US Department of Transportation has special double containment'' requirements for plutonium. The system packaging uses a doubly contained bell jar'' concept. A refrigerated trailer is used for cooling the high-heat payloads. The same packaging is used for both high- and low-heat payloads. The system is scheduled to be available for use by mid-1992. 4 refs., 4 figs., 2 tabs.

Adkins, H.E.; Bearden, T.E.

1990-10-01

178

Small Radioisotope Power System Testing at NASA Glenn Research Center  

NASA Technical Reports Server (NTRS)

In April 2009, NASA Glenn Research Center (GRC) formed an integrated product team (IPT) to develop a Small Radioisotope Power System (SRPS) utilizing a single Advanced Stirling Convertor (ASC) with passive balancer. A single ASC produces approximately 80 We making this system advantageous for small distributed lunar science stations. The IPT consists of Sunpower, Inc., to provide the single ASC with a passive balancer, The Johns Hopkins University Applied Physics Laboratory (JHUAPL) to design an engineering model Single Convertor Controller (SCC) for an ASC with a passive balancer, and NASA GRC to provide technical support to these tasks and to develop a simulated lunar lander test stand. The single ASC with a passive balancer, simulated lunar lander test stand, and SCC were delivered to GRC and were tested as a system. The testing sequence at GRC included SCC fault tolerance, integration, electromagnetic interference (EMI), vibration, and extended operation testing. The SCC fault tolerance test characterized the SCCs ability to handle various fault conditions, including high or low bus power consumption, total open load or short circuit, and replacing a failed SCC card while the backup maintains control of the ASC. The integrated test characterized the behavior of the system across a range of operating conditions, including variations in cold-end temperature and piston amplitude, including the emitted vibration to both the sensors on the lunar lander and the lunar surface. The EMI test characterized the AC and DC magnetic and electric fields emitted by the SCC and single ASC. The vibration test confirms the SCCs ability to control the single ASC during launch. The extended operation test allows data to be collected over a period of thousands of hours to obtain long term performance data of the ASC with a passive balancer and the SCC. This paper will discuss the results of each of these tests.

Dugala, Gina; Bell, Mark; Oriti, Salvatore; Fraeman, Martin; Frankford, David; Duven, Dennis

2013-01-01

179

Concept for a radioisotope powered dual mode lunar rover  

NASA Technical Reports Server (NTRS)

Over three decades ago, the Apollo missions manifestly demonstrated the value of a lunar rover to expand the exploration activities of lunar astronauts. The stated plan of the new Vision for Space Exploration to establish a permanent presence on the moon in the next decades gives new impetus to providing long range roving and exploration capability in support of the siting, construction, and maintenance of future human bases. The incorporation of radioisotope power systems and telerobotic capability in the design has the potential to significantly expand the capability of such a rover, allowing continuous operation during the full lunar day/night cycle, as well as enabling exploration in permanently shadowed regions that may be of interest to humans for the resources they may hold. This paper describes a concept that builds on earlier studies originated in the Apollo program for a Dual Mode (crewed and telerobotic) Lunar Roving Vehicle (DMLRV). The goal of this vehicle would be to provide a multipurpose infrastructure element and remote science platform for the exploration of the moon. The DMLRV would be essential for extending the productivity of human exploration crews, and would provide a unique capability for diverse long-range, long-duration science exploration between human visits. With minimal reconfiguration this vehicle could also provide the basic platform to support a range of site survey and preparation activities in anticipation of the establishment of a permanent human presence on the moon. A conceptual design is presented for the DMLRV, including discussion of mission architecture, vehicle performance, representative science payload accommodation, and equipment and crew radiation considerations.

Elliott, John O.; Schriener, Timothy M.; Coste, Keith

2006-01-01

180

Thermal conductivity of boron carbides  

NASA Technical Reports Server (NTRS)

Knowledge of the thermal conductivity of boron carbide is necessary to evaluate its potential for high-temperature thermoelectric energy conversion applications. Measurements have been conducted of the thermal diffusivity of hot-pressed boron carbide BxC samples as a function of composition (x in the range from 4 to 9), temperature (300-1700 K), and temperature cycling. These data, in concert with density and specific-heat data, yield the thermal conductivities of these materials. The results are discussed in terms of a structural model that has been previously advanced to explain the electronic transport data. Some novel mechanisms for thermal conduction are briefly discussed.

Wood, C.; Emin, D.; Gray, P. E.

1985-01-01

181

DOES SALINITY REDUCE BORON’S TOXIC EFFECT IN BROCCOLI?  

Technology Transfer Automated Retrieval System (TEKTRAN)

High salinity and boron often occur together in irrigation water in arid climates, but very little research has been done to study the interaction of the two. A greenhouse experiment was conducted at the U.S. Salinity Laboratory in sand tanks to evaluate the interactions between B and saline draina...

182

Measured microdosimetric spectra and therapeutic potential of boron neutron capture enhancement of 252Cf brachytherapy.  

PubMed

Californium-252 is a neutron-emitting radioisotope used as a brachytherapy source for radioresistant tumors. Presented here are microdosimetric spectra measured as a function of simulated site diameter and distance from applicator tube 252Cf sources. These spectra were measured using miniature tissue-equivalent proportional counters (TEPCs). An investigation of the clinical potential of boron neutron capture (BNC) enhancement of 252Cf brachytherapy is also provided. The absorbed dose from the BNC reaction was measured using a boron-loaded miniature TEPC. Measured neutron, photon and BNC absorbed dose components are provided as a function of distance from the source. In general, the absorbed dose results show good agreement with results from other measurement techniques. A concomitant boost to 252Cf brachytherapy may be provided through the use of the BNC reaction. The potential magnitude of this BNC enhancement increases with increasing distance from the source and is capable of providing a therapeutic gain greater than 30% at a distance of 5 cm from the source, assuming currently achievable boron concentrations. PMID:16137204

Burmeister, J; Kota, C; Maughan, R L

2005-09-01

183

Advanced crystal growth techniques with III-V boron compound semiconductors  

NASA Astrophysics Data System (ADS)

Semiconducting icosahedral boron arsenide, B12As2, is an excellent candidate for neutron detectors and radioisotope batteries, for which high quality single crystals are required. Thus, the present study was undertaken to grow B12As2 crystals by precipitation from metal solutions (nickel) saturated with elemental boron and arsenic in a sealed quartz ampoule. B12As2 crystals of 8--10 mm were produced when a homogeneous mixture of the three elements was held at 1150 °C for 48--72 hours and slowly cooled (3°C/hr). The crystals varied in color and transparency from black and opaque to clear and transparent. X-ray topography (XRT), Raman spectroscopy, and defect selective etching confirmed that the crystals had the expected rhombohedral structure and a low density of defects (5x107 cm-2). The concentrations of residual impurities (nickel, carbon, etc) were found to be relatively high (1019 cm-3 for carbon) as measured by secondary ion mass spectrometry (SIMS) and elemental analysis by energy dispersive x-ray spectroscopy (EDS). The boron arsenide crystals were found to have favorable electrical properties (? = 24.5 cm2 / Vs), but no interaction between a prototype detector and an alpha particle bombardment was observed. Thus, the flux growth method is viable for growing large B12As2 crystals, but the impurity concentrations remain a problem.

Whiteley, Clinton E.

2011-12-01

184

Removal of boron from wastewater by the hydroxyapatite formation reaction using acceleration effect of ammonia.  

PubMed

The mechanism was discussed for the removal of boron by the hydroxyapatite (HAp) formation reaction using Ca(OH)(2) and (NH(4))(2)HPO(4) in room temperature. Time required to remove boron was 20 min by adding Ca(OH)(2) and (NH(4))(2)HPO(4) for the remaining boron to below 1mg/L. The removal rate of boron was controlled by the HAp precipitate formation and the presence of ammonia. From the XRD patterns and SEM images, HAp could be confirmed in the precipitate product. The reaction between borate ions and calcium hydroxide was accelerated by dehydration with ammonia; the borate-calcium hydroxide compound coprecipitated with resulting HAp. Although the removal of boron decreased in the presence of sulfate, phosphate, and aluminum, these effects could be prevented by adding excess Ca(OH)(2). Interference of fluoride ions was eliminated by adding Al(3+). Sodium alpha-olefin sulfonate was the most effective coagulant for HAp precipitation. The proposed boron removal method has several advantages about treating time and ability of boron removal. The method was successfully applied to the real hot spring wastewater. PMID:22981286

Yoshikawa, Eishi; Sasaki, Atsushi; Endo, Masatoshi

2012-10-30

185

The performance of a boron-loaded gel-fuel ramjet  

NASA Astrophysics Data System (ADS)

The present work focuses on the possibility of combining the advantages of ramjet propulsion with the high energetic potential of boron. However, the use of boron poses two major challenges. The first, common to all solid additives to liquid fuels is particle sedimentation and poor dispersion. This problem is solved through the use of a gel fuel. The second obstacle, specific to boron-enriched fuels, is the difficulty in realizing the full energetic potential of boron. This could be overcome by means of an aft-combustion chamber, where fuel-rich combustion products are mixed with cold bypass air. Cooling causes the gaseous boron oxide to condense and, as a consequence, the heat of evaporation trapped in the gaseous oxide is released. The merits of such a combination are assessed through its ability to power an air-to-surface missile of relatively small size, capable of delivering a large payload to over a distance of about 1000 km in short time. The paper presents a preliminary design of a ramjet missile using a gel fuel loaded with boron. The thermochemical aspects of the two-stage combustion of the fuel are considered. A comparison with a solid rocket motor (SRM) missile launched under the same conditions as the ramjet missile is made. The boron-loaded gel-fuel ramjet is found superior for this mission.

Haddad, A.; Natan, B.; Arieli, R.

2011-10-01

186

Method of separating boron isotopes  

DOEpatents

A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)-dichloroborane as the feed material. The photolysis can readily by achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

Jensen, R.J.; Thorne, J.M.; Cluff, C.L.

1981-01-23

187

Method of separating boron isotopes  

DOEpatents

A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO.sub.2 laser radiation and using fluences significantly below those required to dissociate BCl.sub.3.

Jensen, Reed J. (Los Alamos, NM); Thorne, James M. (Provo, UT); Cluff, Coran L. (Provo, UT); Hayes, John K. (Salt Lake City, UT)

1984-01-01

188

Structure of boron nitride nanotubes  

NASA Astrophysics Data System (ADS)

The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

Buranova, Yu. S.; Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

2015-01-01

189

Radioisotopes Applied to Lubrication Problems of Inertial Gyro Bearings  

Microsoft Academic Search

One of the most critical components of inertial guidance systems are the angular contact bearings of the gyro. The performance of these bearings is, in turn, critically dependent upon their lubrication, which must be derived from oil impregnated ball separators.Radioisotopic techniques have been applied to the study of the impregnation and bleedout characteristics of separators from gyro bearings of two

W. J. Mayer; W. H. Lange; T. F. Conners

1963-01-01

190

Reentry thermal testing of light-weight radioisotope heater unit  

NASA Astrophysics Data System (ADS)

Two Light-Weight Radioisotope Heater Units were exposed to thermal ramps simulating atmospheric reentry. The helium release rates were measured during each test and modeled after simple diffusion theory. The reentry pulses did not result in swelling of the claddings or degradation of fuel pellets.

Peterson, D. E.; Starzynski, J. S.

1982-03-01

191

The Modeling of Radioisotope Micro Batteries for Microsystems  

Microsoft Academic Search

Conventional direct conversion devices of radioisotope micro battery (RMB) suffer from small surface area and unreliability. In order to solve these problems, a method, which is verified with simulation results, is introduced for modeling the direct conversion devices. The fundamental structure of RMB is presented, and the equations of current are founded. The novel direct conversion device of vertical wall

Lei Sun; Wei Z. Yuan; Da Y. Qiao

2006-01-01

192

Anthropogenic radioisotopes to estimate rates of soil redistribution by wind  

Technology Transfer Automated Retrieval System (TEKTRAN)

Erosion of soil by wind and water is a degrading process that affects millions of hectares worldwide. Atmospheric testing of nuclear weapons and the resulting fallout of anthropogenic radioisotopes, particularly Cesium 137, has made possible the estimation of mean soil redistribution rates. The pe...

193

PROCESS ANALYSIS BY RADIOISOTOPES IN THE CHEMICAL AND METALLURGICAL INDUSTRIES  

Microsoft Academic Search

Applications of radioisotopes in process analysis in the chemical and ; metallurgical industries are reviewed. Applications discussed include studies in ; electrolysis of chlorine caustic; analysis of the flow pattern of electrolyte in ; the potassium chlorate cell; process analysis in an alumina plant, studies on the ; flow of glass in melting and working furnaces; the behavior of sulfur

1959-01-01

194

Studies of chemiluminescence in boron atom reactions  

SciTech Connect

Chemiluminescence has been observed in the single collision reactions of boron atoms with O/sub 2/, SO/sub 2/, N/sub 2/O, NO/sub 2/, and H/sub 2/O/sub 2/. The experiments were performed in a beam-gas apparatus using photon counting to detect the optical signals. The electronically excited A/sup 2/pi state of BO was observed in all the reactions. In addition the BO/sup -/ excited state, B/sup 2/..sigma../sup +/, was observed in the reaction of boron with N/sub 2/O. Excited BO/sub 2/ (A/sup 2/pi/sub u/) was observed in the reaction with SO/sub 2/ and excited OH (A/sup 2/..sigma../sup +/) was observed in the reaction with H/sub 2/O/sub 2/. Cross sections for the production of electronically excited molecules were determined. These cross sections for the reactions with O/sub 2/, SO/sub 2/, N/sub 2/O, NO/sub 2/, and H/sub 2/O/sub 2/ are, respectively, 0.048 A/sup 2/, 0.078 A/sup 2/, 0.011 A/sup 2/, 0.19 A/sup 2/, and 0.0058 A/sup 2/. In those reactions involving more than one chemiluminescent product channel, branching ratios were obtained for the observed products. The vibrational distributions in the electronically excited states of BO were determined for all the reactions and were analyzed using information theory. Some implications of the results are discussed.

DeHaven, J.J.

1982-01-01

195

Boron nitride: Composition, optical properties and mechanical behavior  

Microsoft Academic Search

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

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

1987-01-01

196

Wall Temperature Dependence of Boronization Using Decaborane and Diborane  

Microsoft Academic Search

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

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

1993-01-01

197

Boron stimulates embryonic trout growth.  

PubMed

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

Eckhert, C D

1998-12-01

198

Method and system for radioisotope generation  

DOEpatents

A system and a process for producing selected isotopic daughter products from parent materials characterized by the steps of loading the parent material upon a sorbent having a functional group configured to selectively bind the parent material under designated conditions, generating the selected isotopic daughter products, and eluting said selected isotopic daughter products from the sorbent. In one embodiment, the process also includes the step of passing an eluent formed by the elution step through a second sorbent material that is configured to remove a preselected material from said eluent. In some applications a passage of the material through a third sorbent material after passage through the second sorbent material is also performed.

Toth, James J.; Soderquist, Chuck Z.; Greenwood, Lawrence R.; Mattigod, Shas V.; Fryxell, Glen E.; O'Hara, Matthew J.

2014-07-15

199

Enhancement of electrical conductivity and electrochemical activity of hydrogenated amorphous carbon by incorporating boron atoms  

NASA Astrophysics Data System (ADS)

Conductive boron-doped hydrogenated amorphous carbon (B-DLC) thin films were successfully synthesized with RF plasma-enhanced CVD method. By incorporating boron atoms in amorphous carbon, conduction types were changed from n- to p-type, and volume resistivity was decreased from 30.4 (non-doped) to 6.36 × 10-2 ? cm (B/C = 2.500 atom%). B-DLC film with sp2/(sp2 + sp3) carbons of 75 atom% exhibited high resistance to electrochemically-induced corrosion in strong acid solution. Furthermore, it was clarified that boron atoms in DLC could enhance kinetics of hydrogen evolution during water electrolysis at B-DLC surface. B-DLC is, therefore, a promising electrode material for hydrogen production by increasing the concentration of boron atoms in B-DLC and enhancing the reactivity of H2 evolution.

Naragino, Hiroshi; Yoshinaga, Kohsuke; Nakahara, Akira; Tanaka, Sakuya; Honda, Kensuke

2013-06-01

200

Radiobiological evaluation of new boron delivery agents for boron neutron capture therapy  

E-print Network

This thesis evaluates the radiobiological effectiveness of three new boron compounds namely a boronated porphyrin (BOPP) and two liposome formulations for neutron capture therapy (BNCT). The methodology utilizes in vitro ...

Chung, Yoonsun

2008-01-01

201

Molecular basis of adaptation to high soil boron in wheat landraces and elite cultivars.  

PubMed

Environmental constraints severely restrict crop yields in most production environments, and expanding the use of variation will underpin future progress in breeding. In semi-arid environments boron toxicity constrains productivity, and genetic improvement is the only effective strategy for addressing the problem. Wheat breeders have sought and used available genetic diversity from landraces to maintain yield in these environments; however, the identity of the genes at the major tolerance loci was unknown. Here we describe the identification of near-identical, root-specific boron transporter genes underlying the two major-effect quantitative trait loci for boron tolerance in wheat, Bo1 and Bo4 (ref. 2). We show that tolerance to a high concentration of boron is associated with multiple genomic changes including tetraploid introgression, dispersed gene duplication, and variation in gene structure and transcript level. An allelic series was identified from a panel of bread and durum wheat cultivars and landraces originating from diverse agronomic zones. Our results demonstrate that, during selection, breeders have matched functionally different boron tolerance alleles to specific environments. The characterization of boron tolerance in wheat illustrates the power of the new wheat genomic resources to define key adaptive processes that have underpinned crop improvement. PMID:25043042

Pallotta, Margaret; Schnurbusch, Thorsten; Hayes, Julie; Hay, Alison; Baumann, Ute; Paull, Jeff; Langridge, Peter; Sutton, Tim

2014-10-01

202

Study of boron behaviour in two Spanish coal combustion power plants.  

PubMed

A full-scale field study was carried out at two Spanish coal-fired power plants equipped with electrostatic precipitator (ESP) and wet flue gas desulfurisation (FGD) systems to investigate the distribution of boron in coals, solid by-products, wastewater streams and flue gases. The results were obtained from the simultaneous sampling of solid, liquid and gaseous streams and their subsequent analysis in two different laboratories for purposes of comparison. Although the final aim of this study was to evaluate the partitioning of boron in a (co-)combustion power plant, special attention was paid to the analytical procedure for boron determination. A sample preparation procedure was optimised for coal and combustion by-products to overcome some specific shortcomings of the currently used acid digestion methods. In addition boron mass balances and removal efficiencies in ESP and FGD devices were calculated. Mass balance closures between 83 and 149% were obtained. During coal combustion, 95% of the incoming boron was collected in the fly ashes. The use of petroleum coke as co-combustible produced a decrease in the removal efficiency of the ESP (87%). Nevertheless, more than 90% of the remaining gaseous boron was eliminated via the FGD in the wastewater discharged from the scrubber, thereby causing environmental problems. PMID:21664037

Ochoa-González, Raquel; Cuesta, Aida Fuente; Córdoba, Patricia; Díaz-Somoano, Mercedes; Font, Oriol; López-Antón, M Antonia; Querol, Xavier; Martínez-Tarazona, M Rosa; Giménez, Antonio

2011-10-01

203

Potential Applications for Radioisotope Power Systems in Support of Human Exploration Missions  

NASA Technical Reports Server (NTRS)

Radioisotope power systems (RPS) for space applications have powered over 27 U.S. space systems, starting with Transit 4A and 4B in 1961, and more recently with the successful landing of the Mars Science Laboratory rover Curiosity in August 2012. RPS enable missions with destinations far from the Sun with faint solar flux, on planetary surfaces with dense or dusty atmospheres, and at places with long eclipse periods where solar array sizes and energy storage mass become impractical. RPS could also provide an enabling capability in support of human exploration activities. It is envisioned that with the higher power needs of most human mission concepts, a high efficiency thermal-to-electric technology would be required such as the Advanced Stirling Radioisotope generator (ASRG). The ASRG should be capable of a four-fold improvement in efficiency over traditional thermoelectric RPS. While it may be impractical to use RPS as a main power source, many other applications could be considered, such as crewed pressurized rovers, in-situ resource production of propellants, back-up habitat power, drilling, any mobile or remote activity from the main base habitat, etc. This paper will identify potential applications and provide concepts that could be a practical extension of the current ASRG design in providing for robust and flexible use of RPS on human exploration missions.

Cataldo, Robert L.; Colozza, Anthony J.; Schmitz, Paul C.

2013-01-01

204

Californium-252: a remarkable versatile radioisotope  

SciTech Connect

A product of the nuclear age, Californium-252 ({sup 252}Cf) has found many applications in medicine, scientific research, industry, and nuclear science education. Californium-252 is unique as a neutron source in that it provides a highly concentrated flux and extremely reliable neutron spectrum from a very small assembly. During the past 40 years, {sup 252}Cf has been applied with great success to cancer therapy, neutron radiography of objects ranging from flowers to entire aircraft, startup sources for nuclear reactors, fission activation for quality analysis of all commercial nuclear fuel, and many other beneficial uses, some of which are now ready for further growth. Californium-252 is produced in the High Flux Isotope Reactor (HFIR) and processed in the Radiochemical Engineering Development Center (REDC), both of which are located at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. The REDC/HFIR facility is virtually the sole supplier of {sup 252}Cf in the western world and is the major supplier worldwide. Extensive exploitation of this product was made possible through the {sup 252}Cf Market Evaluation Program, sponsored by the United States Department of Energy (DOE) [then the Atomic Energy Commission (AEC) and later the Energy Research and Development Administration (ERDA)]. This program included training series, demonstration centers, seminars, and a liberal loan policy for fabricated sources. The Market Evaluation Program was instituted, in part, to determine if large-quantity production capability was required at the Savannah River Laboratory (SRL). Because of the nature of the product and the means by which it is produced, {sup 252}Cf can be produced only in government-owned facilities. It is evident at this time that the Oak Ridge research facility can meet present and projected near-term requirements. The production, shipment, and sales history of {sup 252}Cf from ORNL is summarized herein.

Osborne-Lee, I.W.; Alexander, C.W.

1995-10-10

205

Boron in Marine Barite: A Potential Proxy for the Boron Isotopic Composition of Seawater  

NASA Astrophysics Data System (ADS)

Paleoceanographic reconstructions of past ocean pH facilitate predictions of the response of ocean chemistry to modern climate change and associated effects on marine ecosystems. Past ocean pH reconstructions rely on the analysis of boron stable isotopic ratios (?11B) in biogenic marine carbonates. The equations used to calculate pH from a measured carbonate ?11B value require an input for the ?11B composition of seawater. Since boron is well mixed throughout the ocean, this value is well-constrained for modern seawater and is thought to be robust for the last ~10 million years given the long residence time of B in the ocean. However, without long-term constraints on seawater ?11B, the accuracy of paleo-pH reconstructions for time periods earlier than ~10 Ma can be called into question. To address this issue, we are exploring the potential use of marine barite as an independent proxy for seawater ?11B. Marine barite forms as an inorganic precipitate in biologically productive regions of the ocean and is highly resistant to post-depositional dissolution. It has been shown to be a reliable proxy for seawater Sulfate, Sr, Ca, Ra, Selenate and Pb isotopes. We hypothesize that boron can also be incorporated into the barite crystal and that the isotopic signature of B in barite will reflect seawater pH. We will present and discuss the results of a labeling experiment in which barite will be precipitated from parent seawater solutions with differing ?11B. Potential incorporation mechanisms and fractionation effects will also be addressed.

Chrystal, A.; Paytan, A.

2012-12-01

206

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

SciTech Connect

The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 [mu] boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. (California Univ., Los Angeles, CA (United States). Inst. of Plasma and Fusion Research); Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. (Oak Ridge National Lab., TN (United States)); Jones, S. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1993-05-01

207

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

SciTech Connect

The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B{sub 4}C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 {mu} boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. [California Univ., Los Angeles, CA (United States). Inst. of Plasma and Fusion Research; Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. [Oak Ridge National Lab., TN (United States); Jones, S. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1993-05-01

208

An exceptionally high boron content supramolecular cuboctahedron.  

PubMed

A boron-rich supramolecular cuboctahedron containing an impressive 240 boron atoms has been synthesized via coordination-driven assembly. The cuboctahedron, which is composed of Cu(2+) paddle-wheel nodes and carborane-isophthalic acids, was obtained simply and in high purity. The ability to precisely characterize the nanostructure via X-ray diffraction makes it unique among boron-rich nanostructures. PMID:23863859

Clingerman, Daniel J; Kennedy, Robert D; Mondloch, Joseph E; Sarjeant, Amy A; Hupp, Joseph T; Farha, Omar K; Mirkin, Chad A

2013-12-21

209

Conduction mechanism in boron carbide  

NASA Technical Reports Server (NTRS)

Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

Wood, C.; Emin, D.

1984-01-01

210

Boron removal from geothermal waters by electrocoagulation.  

PubMed

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

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

2008-05-01

211

Experimental observation of boron nitride chains.  

PubMed

We report the formation and characterization of boron nitride atomic chains. The chains were made from hexagonal boron nitride sheets using the electron beam inside a transmission electron microscope. We find that the stability and lifetime of the chains are significantly improved when they are supported by another boron nitride layer. With the help of first-principles calculations, we prove the heteroatomic structure of the chains and determine their mechanical and electronic properties. Our study completes the analogy between various boron nitride and carbon polymorphs, in accordance with earlier theoretical predictions. PMID:25299068

Cretu, Ovidiu; Komsa, Hannu-Pekka; Lehtinen, Ossi; Algara-Siller, Gerardo; Kaiser, Ute; Suenaga, Kazu; Krasheninnikov, Arkady V

2014-12-23

212

New Applications of Boron Dihalides and Organotrifluoroborates in Organic Synthesis.  

E-print Network

??This dissertation summarizes research focused on the use of boron dihalides and organotrifluoroborates in organic synthesis. The boron dihalide mediated aryl propargyl ether cleavage reactions… (more)

Hall, Kelly Elizabeth

2013-01-01

213

Friction anisotropy in boronated graphite  

NASA Astrophysics Data System (ADS)

Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1-0.35 in the direction of basal plane and becomes high 0.2-0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

Kumar, N.; Radhika, R.; Kozakov, A. T.; Pandian, R.; Chakravarty, S.; Ravindran, T. R.; Dash, S.; Tyagi, A. K.

2015-01-01

214

Metal matrix composite fuel for space radioisotope energy sources  

NASA Astrophysics Data System (ADS)

Radioisotope fuels produce heat that can be used for spacecraft thermal control or converted to electricity. They must retain integrity in the event of destruction or atmospheric entry of the parent spacecraft. Addition of a metal matrix to the actinide oxide could yield a more robust fuel form. Neodymium (III) oxide (Nd2O3) - niobium metal matrix composites were produced using Spark Plasma Sintering; Nd2O3 is a non-radioactive surrogate for americium (III) oxide (Am2O3). Two compositions, 70 and 50 wt% Nd2O3, were mechanically tested under equibiaxial (ring-on-ring) flexure according to ASTM C1499. The addition of the niobium matrix increased the mean flexural strength by a factor of about 2 compared to typical ceramic nuclear fuels, and significantly increased the Weibull modulus to over 20. These improved mechanical properties could result in reduced fuel dispersion in severe accidents and improved safety of space radioisotope power systems.

Williams, H. R.; Ning, H.; Reece, M. J.; Ambrosi, R. M.; Bannister, N. P.; Stephenson, K.

2013-02-01

215

Emitted radiation characteristics of plutonium dioxide radioisotope thermoelectric generators  

NASA Technical Reports Server (NTRS)

The nuclear and emitted radiation characteristics of the radioisotope elements and impurities in commercial grade plutonium dioxide are presented in detail. The development of the methods of analysis are presented. Radioisotope thermoelectric generators (RTG) of 1575, 3468 and 5679 thermal watts are characterized with respect to neutron and gamma photon source strength as well as spatial and number flux distribution. The results are presented as a function of detector position and light element contamination concentration for fuel age ranging from 'fresh' to 18 years. The data may be used to obtain results for given O-18 and Pu-236 concentrations. The neutron and gamma photon flux and dose calculations compare favorably with reported experimental values for SNAP-27.

Gingo, P. J.; Steyn, J. J.

1971-01-01

216

Safety status of space radioisotope and reactor power sources  

NASA Technical Reports Server (NTRS)

The current overall safety criterion for both radioisotope and reactor power sources is containment or immobilization in the case of a reentry accident. In addition, reactors are designed to remain subcritical under conditions of land impact or water immersion. A very extensive safety test and analysis program was completed on the radioisotope thermoelectric generators (RTGs) in use on the Galileo spacecraft and planned for use on the Ulysses spacecraft. The results of this work show that the RTGs will pose little or no risk for any credible accident. The SP-100 space nuclear reactor program has begun addressing its safety criteria, and the design is planned to be such as to ensure meeting the various safety criteria. Preliminary mission risk analyses on SP-100 show the expected value population dose from postulated accidents on the reference mission to be very small. It is concluded that the current US nuclear power sources are the safest flown.

Bennett, Gary L.

1990-01-01

217

Process for radioisotope recovery and system for implementing same  

DOEpatents

A method of recovering daughter isotopes from a radioisotope mixture. The method comprises providing a radioisotope mixture solution comprising at least one parent isotope. The at least one parent isotope is extracted into an organic phase, which comprises an extractant and a solvent. The organic phase is substantially continuously contacted with an aqueous phase to extract at least one daughter isotope into the aqueous phase. The aqueous phase is separated from the organic phase, such as by using an annular centrifugal contactor. The at least one daughter isotope is purified from the aqueous phase, such as by ion exchange chromatography or extraction chromatography. The at least one daughter isotope may include actinium-225, radium-225, bismuth-213, or mixtures thereof. A liquid-liquid extraction system for recovering at least one daughter isotope from a source material is also disclosed.

Meikrantz, David H. (Idaho Falls, ID); Todd, Terry A. (Aberdeen, ID); Tranter, Troy J. (Idaho Falls, ID); Horwitz, E. Philip (Naperville, IL)

2009-10-06

218

Radioisotope Concentration in Lake Sediments of Maracaibo, Venezuela  

SciTech Connect

Maracaibo Lake is one of the most important water basing and oil producing regions in Venezuela. Changes in the local environment have been monitored for chemical pollution in the past. For this study we selected a set of sediment samples collected in the shore and analyzed for its radioisotope content. Results show the gamma emitting isotopes distribution. Isotopes concentrations have been determined within the natural K, Th and U families.

Salas, A. Rangel; Viloria, T. [La Universidad del Zulia (Venezuela); Sajo-Bohus, L.; Barros, H.; Greaves, E. D.; Palacios, D. [Universidad Simon Bolivar (Venezuela)

2007-10-26

219

Procurement of a fully licensed radioisotope thermoelectric generator transportation system  

NASA Astrophysics Data System (ADS)

The present transportation system for radioisotope thermoelectric generators and heater units is being developed to comply with all applicable U.S. DOT regulations, including a doubly-contained 'bell jar' concept for the required double-containment of plutonium. Modifications in handling equipment and procedures are entailed by this novel packaging design, and will affect high-capacity forklifts, overhead cranes, He-backfilling equipment, etc. Attention is given to the design constraints involved, and to the Federal procurement process.

Adkins, Harold E.; Bearden, Thomas E.

220

Isotope identification in the GammaTracker handheld radioisotope identifier  

Microsoft Academic Search

GammaTracker is a portable handheld radioisotope identifier using position sensitive CdZnTe crystals. The device uses a peak-based method for isotope identification implemented on an embedded computing platform within the device. This paper presents the run-time optimized algorithms used in this peak-based method of analysis. Performance of the algorithms is presented using measured data from gamma-ray sources.

Michael T. Batdorf; Walter K. Hensley; Carolyn E. Seifert; Leslie J. Kirihara; Luke E. Erikson; David V. Jordan

2009-01-01

221

Isotope Identification in the GammaTracker Handheld Radioisotope Identifier  

SciTech Connect

GammaTracker is a portable handheld radioisotope identifier using position sensitive CdZnTe crystals. The device uses a peak-based method for isotope identification implemented on an embedded computing platform within the device. This paper presents the run-time optimized algorithms used in this peak-based approach. Performance of the algorithms is presented using measured data from gamma-ray sources.

Batdorf, Michael T.; Hensley, Walter K.; Seifert, Carolyn E.; Kirihara, Leslie J.; Erikson, Luke E.; Jordan, David V.

2009-11-13

222

Stimulus sensitive gel with radioisotope and methods of making  

DOEpatents

The present invention is a thermally reversible stimulus-sensitive gel or gelling copolymer radioisotope carrier that is a linear random copolymer of an [meth]acrylamide derivative and a hydrophilic comonomer, wherein the linear random copolymer is in the form of a plurality of linear chains having a plurality of molecular weights greater than or equal to a minimum gelling molecular weight cutoff. Addition of a biodegradable backbone and/or a therapeutic agent imparts further utility. The method of the present invention for making a thermally reversible stimulus-sensitive gelling copolymer radionuclcide carrier has the steps of: (a) mixing a stimulus-sensitive reversible gelling copolymer with an aqueous solvent as a stimulus-sensitive reversible gelling solution; and (b) mixing a radioisotope with said stimulus-sensitive reversible gelling solution as said radioisotope carrier. The gel is enhanced by either combining it with a biodegradable backbone and/or a therapeutic agent in a gelling solution made by mixing the copolymer with an aqueous solvent.

Weller, Richard E. (Selah, WA) [Selah, WA; Lind, Michael A. (Kent, WA) [Kent, WA; Fisher, Darrell R. (Richland, WA) [Richland, WA; Gutowska, Anna (Richland, WA) [Richland, WA; Campbell, Allison A. (Kennewick, WA) [Kennewick, WA

2001-10-02

223

Radioisotope Power: A Key Technology for Deep Space Exploration  

NASA Technical Reports Server (NTRS)

A Radioisotope Power System (RPS) generates power by converting the heat released from the nuclear decay of radioactive isotopes, such as Plutonium-238 (Pu-238), into electricity. First used in space by the U.S. in 1961, these devices have enabled some of the most challenging and exciting space missions in history, including the Pioneer and Voyager probes to the outer solar system; the Apollo lunar surface experiments; the Viking landers; the Ulysses polar orbital mission about the Sun; the Galileo mission to Jupiter; the Cassini mission orbiting Saturn; and the recently launched New Horizons mission to Pluto. Radioisotopes have also served as a versatile heat source for moderating equipment thermal environments on these and many other missions, including the Mars exploration rovers, Spirit and Opportunity. The key advantage of RPS is its ability to operate continuously, independent of orientation and distance relative to the Sun. Radioisotope systems are long-lived, rugged, compact, highly reliable, and relatively insensitive to radiation and other environmental effects. As such, they are ideally suited for missions involving long-lived, autonomous operations in the extreme conditions of space and other planetary bodies. This paper reviews the history of RPS for the U.S. space program. It also describes current development of a new Stirling cycle-based generator that will greatly expand the application of nuclear-powered missions in the future.

Schmidt, George; Sutliff, Tom; Dudzinski, Leonard

2008-01-01

224

Radioisotope Electric Propulsion Centaur Orbiter Spacecraft Design Overview  

NASA Technical Reports Server (NTRS)

Radioisotope electric propulsion (REP) has been shown in past studies to enable missions to outerplanetary bodies including the orbiting of Centaur asteroids. Key to the feasibility for REP missions are long life, low power electric propulsion (EP) devices, low mass radioisotope power systems (RPS) and light spacecraft (S/C) components. In order to determine what are the key parameters for EP devices to perform these REP missions a design study was completed to design an REP S/C to orbit a Centaur in a New Frontiers cost cap. The design shows that an orbiter using several long lived (approximately 200 kg Xenon throughput), low power (approximately 700 W) Hall thrusters teamed with six (150 W each) Advanced Stirling Radioisotope Generators (ASRG) can deliver 60 kg of science instruments to a Centaur in 10 yr within the New Frontiers cost cap. Optimal specific impulses for the Hall thrusters were found to be around 2000 sec with thruster efficiencies over 40%. Not only can the REP S/C enable orbiting a Centaur (when compared to an all chemical mission only capable of flybys) but the additional power from the REP system can be reused to enhance science and simplify communications.

Oleson, Steve; McGuire, Melissa; Sarver-Verhey, Tim; Juergens, Jeff; Parkey, Tom; Dankanich, John; Fiehler, Doug; Gyekenyesi, John; Hemminger, Joseph; Gilland, Jim; Colozza, Tony; Packard, Tom; Nguyen, Thahn; Schmitz, Paul; Ostdiek, Paul; Gold, Rob; Lisse, Carey; Hibbits, Karl

2009-01-01

225

Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Uranium dioxide-only and uranium dioxide-gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and then sintering at 1400 and 1525 K. The deposited boron was identified by infrared spectrum. The morphology of the coating was studied by using scanning electron microscope. The plate, grainy and string (fiber)-like boron structures were observed.

Durmazuçar, Hasan H.; Gündüz, Güngör

2000-12-01

226

Synthesis of vertically aligned boron nitride nanosheets using CVD method  

SciTech Connect

Highlights: ? The synthesized boron nitride nanosheets (BNNSs) are vertically aligned and very thin. ? No electrical field is applied in the CVD process. ? The thin BNNSs show a low turn-on field of 6.5 V ?m{sup ?1} and emit strong UV light. -- Abstract: Boron nitride nanosheets (BNNSs) protruding from boron nitride (BN) films were synthesized on silicon substrates by chemical vapor deposition technique from a gas mixture of BCl{sub 3}–NH{sub 3}–H{sub 2}–N{sub 2}. Parts of the as-grown nanosheets were vertically aligned on the BN films. The morphology and structure of the synthesized BNNSs were characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transformation infrared spectroscopy. The chemical composition was studied by energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Cathodoluminescence spectra revealed that the product emitted strong UV light with a broad band ranging from 250 to 400 nm. Field-emission characteristic of the product shows a low turn-on field of 6.5 V ?m{sup ?1}.

Zhang, Chao [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China)] [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China); Hao, Xiaopeng, E-mail: xphao@sdu.edu.cn [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China)] [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China); Wu, Yongzhong, E-mail: wuyz@sdu.edu.cn [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China)] [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China); Du, Miao [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China)] [State Key Laboratory of Crystal Materials, Shandong University, 27 Shandanan Road, Jinan 250100 (China)

2012-09-15

227

Hafnium radioisotope recovery from irradiated tantalum  

DOEpatents

Hafnium is recovered from irradiated tantalum by: (a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum; (b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution; (c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate; (d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution; (e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange; (f) separating fluoride ion complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride to obtain a second precipitate containing the hafnium and iron; (g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron; (h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange; (i) drying the ion exchanged hafnium solution to obtain hafnium isotopes. Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by cation exchange, then anion exchange, is performed.

Taylor, Wayne A. (Los Alamos, NM); Jamriska, David J. (Los Alamos, NM)

2001-01-01

228

A boron-boron coupling reaction between two ethyl cation analogues.  

PubMed

The design of larger architectures from smaller molecular building blocks by element-element coupling reactions is one of the key concerns of synthetic chemistry, so a number of strategies were developed for this bottom-up approach. A general scheme is the coupling of two elements with opposing polarity or that of two radicals. Here, we show that a B-B coupling reaction is possible between two boron analogues of the ethyl cation, resulting in the formation of an unprecedented dicationic tetraborane. The bonding properties in the rhomboid B? core of the product can be described as two B-B units connected by three-centre, two-electron bonds, sharing the short diagonal. Our discovery might lead the way to the long sought-after boron chain polymers with a structure similar to the silicon chains in ?-SiB?. Moreover, the reaction is a prime textbook example of the influence of multiple-centre bonding on reactivity. PMID:24256867

Litters, Sebastian; Kaifer, Elisabeth; Enders, Markus; Himmel, Hans-Jörg

2013-12-01

229

A boron-boron coupling reaction between two ethyl cation analogues  

NASA Astrophysics Data System (ADS)

The design of larger architectures from smaller molecular building blocks by element-element coupling reactions is one of the key concerns of synthetic chemistry, so a number of strategies were developed for this bottom-up approach. A general scheme is the coupling of two elements with opposing polarity or that of two radicals. Here, we show that a B-B coupling reaction is possible between two boron analogues of the ethyl cation, resulting in the formation of an unprecedented dicationic tetraborane. The bonding properties in the rhomboid B4 core of the product can be described as two B-B units connected by three-centre, two-electron bonds, sharing the short diagonal. Our discovery might lead the way to the long sought-after boron chain polymers with a structure similar to the silicon chains in ?-SiB3. Moreover, the reaction is a prime textbook example of the influence of multiple-centre bonding on reactivity.

Litters, Sebastian; Kaifer, Elisabeth; Enders, Markus; Himmel, Hans-Jörg

2013-12-01

230

Initial Boronization of JT-60U Tokamak Using Decaborane  

NASA Astrophysics Data System (ADS)

A decaborane-based boronization system has been installed in the JT-60U tokamak in order to reduce the influx of impurities during plasma discharges. Boronization has been performed under a glow discharge using a helium-decaborane gas mixture. The properties of the boron films deposited through boronization and the effects of boronization on the tokamak discharges were investigated. It was found that the deposition of a boron layer with high purity was achieved with few impurities other than hydrogen through boronization, and that the present boronization deposited toroidally nonuniform boron film. It was also found that the decaborane-based boronization resulted in good plasma performance similar to that of conventional boronization.

Saidoh, Masahiro; Ogiwara, Norio; Shimada, Michiya; Arai, Takashi; Hiratsuka, Hajime; Koike, Tsuneyuki; Shimizu, Masatsugu; Ninomiya, Hiromasa; Nakamura, Hiroo; Jimbou, Ryutarou; Yagyu, Jyunichi; Sugie, Tatsuo; Sakasai, Akira; Asakura, Nobuyuki; Yamage, Masashi; Sugai, Hideo; Jackson, Gary L.

1993-07-01

231

Initial boronization of JT-60U tokamak using decaborane  

NASA Astrophysics Data System (ADS)

A decaborane-based boronization system has been installed in the JT-60U tokamak in order to reduce the influx of impurities during plasma discharges. Boronization has been performed under a glow discharge using a helium-decaborane gas mixture. The properties of the boron films deposited through boronization and the effects of boronization on the tokamak discharges were investigated. It was found that the deposition of a boron layer with high purity was achieved with few impurities other than hydrogen through boronization and that the present boronization deposited toroidally nonuniform boron film. It was also found that the decaborane-based boronization resulted in good plasma performance similar to that of conventional boronization.

Saidoh, Masahiro; Ogiwara, Norio; Shimada, Michiya; Arai, Takashi; Hiratsuka, Hajime; Koike, Tsuneyuki; Shimizu, Masatsugu; Ninomiya, Hiromasa; Nakamura, Hiroo; Jimbou, Ryutarou

1993-07-01

232

Accumulation of 10Bin the Central Degenerative Areas of Human Glioma and Colon Carcinoma Spheroids after Sulfhydryl Boron Hydride Administration1  

Microsoft Academic Search

Sulfhydryl boron hydride (BSH) (IOBenriched) is presently used for boron neutron capture therapy of malignant gliomas. BSH must be close to the target cells to be effective in the inactivation of cell proliferation because of the short range of the reaction products (5-9 |tm). Clinical experience indicates that BSH is taken up in gliomas but it is not known to

Orn-Anong Pettersson; Erik Grusell

1992-01-01

233

Combustion characteristics of GAP-coated boron particles and the fuel-rich solid propellant  

SciTech Connect

A process was employed that permits the coating of energetic glycidyl azide polymer (GAP) on the boron surface. Ignition and combustion behavior of single particle pure crystalline boron and GAP-coated boron at atmospheric pressure was studied experimentally by injecting the particles into the stream of hot gaseous environment of a flat-flame burner using premixed propane-oxygen-nitrogen gases. Chopped streak photographic observation was used to measure the ignition and combustion time. The flame temperature was fixed around 2,343 K, but under wider O{sub 2} level range than previous investigations. Measurement results show that GAP coating can shorten boron particle ignition delay time, however, the effect diminishes as the O{sub 2} level in combustion gas decreases. Possible mechanisms based on relevant reactions and heat effects were proposed. Combustion characteristics of fuel-rich solid propellants based on GAP-coated amorphous boron particles and uncoated ones were compared using different techniques such as combustion phenomena observations by a windowed strand burner, quenched propellant surface morphology analysis by scanning electron microscope, and combustion residues size analysis from the quenched particle collection bomb experiments. It was concluded that GAP-coated amorphous-boron-based fuel-rich propellants exhibit more vigorous combustion phenomena, higher burning rates, and a lesser extent of residue agglomeration than the uncoated baseline propellant. Moreover, reaction mechanisms were proposed to elucidate the combustion products obtained in this study.

Shyu, I.M. [Chung Cheng Inst. of Technology, Tashi (Taiwan, Province of China). Dept. of Applied Chemistry] [Chung Cheng Inst. of Technology, Tashi (Taiwan, Province of China). Dept. of Applied Chemistry; Liu, T.K. [Chung Shan Inst. of Science and Technology, Lungtan (Taiwan, Province of China). Chemical System Research Division] [Chung Shan Inst. of Science and Technology, Lungtan (Taiwan, Province of China). Chemical System Research Division

1995-03-01

234

Low-energy radioisotope beam separator CRIB  

NASA Astrophysics Data System (ADS)

A low-energy in-flight type RI beam separator, called CRIB, has been installed for nuclear physics and nuclear astrophysics by the Center for Nuclear Study, the University of Tokyo in the RIKEN Accelerator Research Facility. It consists of a double achromatic system and an Wien filter. It is capable of providing RI beams at 5-10 MeV/nucleon. Since CRIB has been developed in the end of 2000, many proton-rich RI beams were successfully produced via the ( p, n), ( d, t), and ( 3He, n) reactions in inverse kinematics. In this paper, the design of the separator and its performance are discussed including the method of RI-beam production at low energies.

Yanagisawa, Y.; Kubono, S.; Teranishi, T.; Ue, K.; Michimasa, S.; Notani, M.; He, J. J.; Ohshiro, Y.; Shimoura, S.; Watanabe, S.; Yamazaki, N.; Iwasaki, H.; Kato, S.; Kishida, T.; Morikawa, T.; Mizoi, Y.

2005-02-01

235

Effect of microwave radiation on boron activation  

Microsoft Academic Search

Chemically reactive impurities such as oxygen and fluorine alter the diffusion and activation kinetics of boron during the anneal process. An examination of the role these impurities play during the anneal process indicates important differences between microwave and lamp-based rapid thermal processing (RTP) for low energy implants. The most notable differences for boron diffusion behavior during microwave annealing are: the

Keith Thompson; John H. Booske; D. F. Downey; E. A. Arevalo

2002-01-01

236

Porphyrins for boron neutron capture therapy  

DOEpatents

Novel compounds for treatment of brain tumors in Boron Neutron Capture Therapy are disclosed. A method for preparing the compounds as well as pharmaceutical compositions containing said compounds are also disclosed. The compounds are water soluble, non-toxic and non-labile boronated porphyrins which show significant uptake and retention in tumors.

Miura, Michiko (Center Moriches, NY); Gabel, Detlef (Bremen, DE)

1990-01-01

237

Phase evolution in boron nitride thin films  

Microsoft Academic Search

Boron nitride (BN) thin films were deposited on monocrystalline Si (100) wafers using electron beam evaporation of boron with simultaneous bombardment by nitrogen and argon ions. The effect of film thickness on the resultant BN phase was investigated using Fourier transform infrared (FTIR) spectroscopy and high resolution transmission electron microscopy (HRTEM). These techniques revealed the consecutive deposition of an initial

D. J. Kester; K. S. Ailey; R. F. Davis; K. L. More

1993-01-01

238

Boronated mesophase pitch coke for lithium insertion  

NASA Astrophysics Data System (ADS)

Boronated carbons from mesophase pitch have been used as materials for lithium storage in Li/carbon cells. Doping by boron has been realized by co-pyrolysis of coal tar pitch with the pyridine-borane complex. Amount of boron in mesocarbon microbeads (MCMB) varied from 1.4 to 1.8 wt.% affecting the texture of carbon. Optical microscopy and X-ray diffractograms have shown tendency to more disordered structure for boron-doped carbon. The values of specific reversible capacity ( x) varied from 0.7 to 1.1 depending significantly on the final temperature of pyrolysis (700-1150°C). The optimal charge/discharge performance was observed for boronated carbon heated at 1000°C.

Frackowiak, E.; Machnikowski, J.; Kaczmarska, H.; Béguin, F.

239

Stabilization of boron carbide via silicon doping  

NASA Astrophysics Data System (ADS)

Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

Proctor, J. E.; Bhakhri, V.; Hao, R.; Prior, T. J.; Scheler, T.; Gregoryanz, E.; Chhowalla, M.; Giulani, F.

2015-01-01

240

Stabilization of boron carbide via silicon doping.  

PubMed

Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping. PMID:25427850

Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

2015-01-14

241

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

242

Accelerator based Production of Auger-Electron-emitting Isotopes for  

E-print Network

-labeled radiopharmaceutical. The production method of these radioisotopes has been developed using a low-energy cyclotron via the nuclear reactions 119Sn(p,n)119Sb and 117Sn(p,n)117Sb including measurements of the excitation function the ability of producing therapeutic quantities of 119Sb and other radioisotopes for therapy with a low-energy

243

A Search for Boron in Damped Ly{\\alpha} Systems  

E-print Network

We present the first systematic study of boron beyond the Local Group. This analysis is performed on a sample of 30 damped Ly{\\alpha} systems (DLAs) with strong metal-lines, which are expected to trace the interstellar medium of high z galaxies. We report on two boron detections at > 3{\\sigma} significance; one new detection and one confirmation. The ratios of B/O and, for the first time, B/S are compared with previous stellar and interstellar measurements in the Milky Way and Small Magellanic Cloud. The novel comparison with sulphur, which tracks oxygen's abundance, alleviates the uncertainty associated with stellar oxygen measurements. For both detections, the inferred B/S ratio is in excess of the prediction of primary boron production from spallation processes. Possible sources of contamination are discussed, as well as physical effects that could impact the observed ratios. However taken at face value, the implication of these measurements suggest potentially higher cosmic ray fluxes in DLAs. The prospec...

Berg, Trystyn A M; Venn, Kim A; Prochaska, J Xavier

2013-01-01

244

Major NLTE Corrections to HST Boron Observations?  

NASA Astrophysics Data System (ADS)

A theoretical study of NLTE effects in the analysis of HST boron observations indicates that all currently-reported abundances are wrong by factors of 2.5-4X. (A systematic effect much larger than any measurement error). If true, this would force major changes in the modelling of Be and B abundances as products of cosmic ray spallation plus direct production by supernovae in the early galaxy. It would help explain why no simple model of galactic chemical evolution can yet explain the evolution of the light elements Li, Be, and B at the same time as the evolution of heavier elements such as Fe and O. We can test the NLTE prediction by observing the BII line at 1362 Angstrom in the star Procyon, whose BI abundance has been extremely well determined from two groups previous HST observations of the BI 2500Angstrom line. (The repaired GHRS opens the possibility of observing the BII line). Our calculations (see figures) demonstrate we should easily see if large amounts of B are being "hidden" (from BI observations) by being in the form of BII. We will use the star Sirius as a reference for differential analysis. BII was observed in Vega and Sirius by the Copernicus satellite 20 years ago, and our re-analysis of this data (see figure) shows we have an excellent chance of success in the present proposal.

Duncan, Douglas

1995-07-01

245

Boron-10 Lined Proportional Counter Model Validation  

SciTech Connect

The decreasing supply of 3He is stimulating a search for alternative neutron detectors; one potential 3He replacement is 10B-lined proportional counters. Simulations are being performed to predict the performance of systems designed with 10B-lined tubes. Boron-10-lined tubes are challenging to model accurately because the neutron capture material is not the same as the signal generating material. Thus, to simulate the efficiency, the neutron capture reaction products that escape the lining and enter the signal generating fill gas must be tracked. The tube lining thickness and composition are typically proprietary vendor information, and therefore add additional variables to the system simulation. The modeling methodologies used to predict the neutron detection efficiency of 10B-lined proportional counters were validated by comparing simulated to measured results. The measurements were made with a 252Cf source positioned at several distances from a moderated 2.54-cm diameter 10B-lined tube. Models were constructed of the experimental configurations using the Monte Carlo transport code MCNPX, which is capable of tracking the reaction products from the (n,10B) reaction. Several different lining thicknesses and compositions were simulated for comparison with the measured data. This paper presents the results of the evaluation of the experimental and simulated data, and a summary of how the different linings affect the performance of a coincidence counter configuration designed with 10B-lined proportional counters.

Lintereur, Azaree T.; Ely, James H.; Kouzes, Richard T.; Rogers, Jeremy L.; Siciliano, Edward R.

2012-11-18

246

Synthesis and ligand-based reduction chemistry of boron difluoride complexes with redox-active formazanate ligands.  

PubMed

Mono(formazanate) boron difluoride complexes (LBF2), which show remarkably facile and reversible ligand-based redox-chemistry, were synthesized by transmetallation of bis(formazanate) zinc complexes with boron trifluoride. The one-electron reduction product [LBF2](-)[Cp2Co](+) and a key intermediate for the transmetallation reaction, the six-coordinate zinc complex (L(BF3))2Zn were isolated and fully characterized. PMID:24853979

Chang, M-C; Otten, E

2014-07-18

247

CHARACTERISATION AND IMPLICATIONS OF THE BORON RICH LAYER RESULTING FROM OPEN-TUBE LIQUID SOURCE BBR3 BORON DIFFUSION PROCESSES  

E-print Network

CHARACTERISATION AND IMPLICATIONS OF THE BORON RICH LAYER RESULTING FROM OPEN-TUBE LIQUID SOURCE BBR3 BORON DIFFUSION PROCESSES Michael Andreas Kessler, Tobias Ohrdes, Bettina Wolpensinger, Robert, Germany ABSTRACT Boron diffusion is commonly associated with the formation of an undesirable boron rich

248

Development of Advanced Stirling Radioisotope Generator for Space Exploration  

NASA Technical Reports Server (NTRS)

Under the joint sponsorship of the Department of Energy and NASA, a radioisotope power system utilizing Stirling power conversion technology is being developed for potential future space missions. The higher conversion efficiency of the Stirling cycle compared with that of Radioisotope Thermoelectric Generators (RTGs) used in previous missions (Viking, Pioneer, Voyager, Galileo, Ulysses, Cassini, and New Horizons) offers the advantage of a four-fold reduction in PuO2 fuel, thereby saving cost and reducing radiation exposure to support personnel. With the advancement of state-of-the-art Stirling technology development under the NASA Research Announcement (NRA) project, the Stirling Radioisotope Generator program has evolved to incorporate the advanced Stirling convertor (ASC), provided by Sunpower, into an engineering unit. Due to the reduced envelope and lighter mass of the ASC compared to the previous Stirling convertor, the specific power of the flight generator is projected to increase from 3.5 to 7 We/kg, along with a 25 percent reduction in generator length. Modifications are being made to the ASC design to incorporate features for thermal, mechanical, and electrical integration with the engineering unit. These include the heat collector for hot end interface, cold-side flange for waste heat removal and structural attachment, and piston position sensor for ASC control and power factor correction. A single-fault tolerant, active power factor correction controller is used to synchronize the Stirling convertors, condition the electrical power from AC to DC, and to control the ASCs to maintain operation within temperature and piston stroke limits. Development activities at Sunpower and NASA Glenn Research Center (GRC) are also being conducted on the ASC to demonstrate the capability for long life, high reliability, and flight qualification needed for use in future missions.

Chan, Jack; Wood, J. Gary; Schreiber, Jeffrey G.

2007-01-01

249

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management  

NASA Technical Reports Server (NTRS)

One of the advantages of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used to maintain electronic components within a controlled temperature range, to warm propulsion tanks and mobility actuators, and to gasify liquid propellants. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated a very large quantity of waste heat due to the relatively low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-watt Stirling Radioisotope Generator (SRG110) will have much higher conversion efficiencies than their predecessors and therefore may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of approx. 6 to 7% and 200 C housing surface temperatures, would need to use large and heavy radiator heat exchangers to transfer the waste heat to the internal spacecraft components. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation by using the heat exchangers or additional shields. The SRG110, with an efficiency around 22% and 50 C nominal housing surface temperature, can use the available waste heat more efficiently by more direct heat transfer methods such as heat pipes, thermal straps, or fluid loops. The lower temperatures allow the SRG110 much more flexibility to the spacecraft designers in configuring the generator without concern of overheating nearby scientific instruments, thereby eliminating the need for thermal shields. This paper will investigate using a high efficiency SRG110 for spacecraft thermal management and outline potential methods in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander) to illustrate the advantages with regard to ease of assembly, less complex interfaces, and overall mass savings.

Pantano, David R.; Dottore, Frank; Geng, Steven M.; Schrieber, Jeffrey G.; Tobery, E. Wayne; Palko, Joseph L.

2005-01-01

250

Radioisotope Stirling Generator Options for Pluto Fast Flyby Mission  

NASA Astrophysics Data System (ADS)

The preceding paper (Schock 1994) described conceptual designs and analytical results for five Radioisotope Thermoelectric Generator (RTG) options for the Pluto Fast Flyby (PFF) mission, and the present paper describes three Radioisotope Stirling Generator (RSG) options for the same mission. The RSG options are based on essentially the same radioisotope heat source modules used in previously flown RTGs and on designs and analyses of a 75-Watt free-piston Stirling engine produced by Mechanical Technology Incorporated (MTI) for NASA's Lewis Research Center. The integrated system design options presented were generated in a Fairchild Space study sponsored by the Department of Energy's Office of Special Applications, in support of ongoing PFF mission and spacecraft studies that the Jet Propulsion Laboratory (JPL) is conducting for the National Aeronautics and Space Administration (NASA). That study's NASA-directed goal is to reduce the spacecraft mass from its baseline value of 166 kg to -110 kg, which implies a mass goal of less than 10 kg for a power source able to deliver 69 Watts(e) at the end of the 9.2-year mission. In general, the Stirling options were found to be lighter than the thermoelectric options described in the preceding paper. But they are less mature, requiring more development, and entailing greater programmatic risk. The Stirling power system mass ranged from 7.3 kg (well below the 10-kg goal) for a non-redundant system to 11.3 kg for a redundant system able to maintain full power if one of its two engines fails. In fact, the latter system could deliver as much as 115 Watts(e) if desired by the mission planners.

Schock, Alfred

1994-07-01

251

Boron Nitride Nanoribbons Becomes Metallic  

SciTech Connect

Standard spin-polarized density functional theory calculations have been conducted to study the electronic structures and magnetic properties of O and S functionalized zigzag boron nitride nanoribbons (zBNNRs). Unlike the semiconducting and nonmagnetic H edge-terminated zBNNRs, the O edge-terminated zBNNRs have two energetically degenerate magnetic ground states with a ferrimagnetic character on the B edge, both of which are metallic. In contrast, the S edge-terminated zBNNRs are nonmagnetic albeit still metallic. An intriguing coexistence of two different Peierls-like distortions is observed for S edge-termination that manifests as a strong S dimerization at the B zigzag edge and a weak S trimerization at the N zigzag edge, dictated by the band fillings at the vicinity of the Fermi level. Nevertheless, metallicity is retained along the S wire on theNedge due to the partial filling of the band derived from the pz orbital of S. A second type of functionalization with O or S atoms embedded in the center of zBNNRs yields semiconducting features. Detailed examination of both types of functionalized zBNNRs reveals that the p orbitals on O or S play a crucial role in mediating the electronic structures of the ribbons.We suggest that O and S functionalization of zBNNRs may open new routes toward practical electronic devices based on boron nitride materials.

Huang, Jingsong [ORNL; Terrones Maldonado, Humberto [ORNL; Sumpter, Bobby G [ORNL; Lopez-Benzanilla, Alejandro [Oak Ridge National Laboratory (ORNL)

2011-01-01

252

Initial Boronization of JT-60U Tokamak Using Decaborane  

Microsoft Academic Search

A decaborane-based boronization system has been installed in the JT-60U tokamak in order to reduce the influx of impurities during plasma discharges. Boronization has been performed under a glow discharge using a helium-decaborane gas mixture. The properties of the boron films deposited through boronization and the effects of boronization on the tokamak discharges were investigated. It was found that the

Masahiro Saidoh; Norio Ogiwara; Michiya Shimada; Takashi Arai; Hajime Hiratsuka; Tsuneyuki Koike; Masatsugu Shimizu; Hiromasa Ninomiya; Hiroo Nakamura; Ryutarou Jimbou; Jyunichi Yagyu; Tatsuo Sugie; Akira Sakasai; Nobuyuki Asakura; Masashi Yamage; Hideo Sugai; Gary L. Jackson

1993-01-01

253

Radioisotope X-ray fluorescence and neutron activation analyses of the trace element concentrations of the rainbow trout  

NASA Astrophysics Data System (ADS)

The muscles and livers of the ten rainbow trouts ( Oncorhynchus mykiss; N, 1752) obtained from Sapanca, Aquaculture Facility of Aquatic Products Faculty, The University of Istanbul (Turkey), have been analysed quantitatively for some minor elements using the radioisotope energy dispersive X-ray fluorescence (EDXRF) and neutron activation analysis (NAA) methods. It was found that samples contain Na, K, Ca, Sc, Cs, Fe, Co, Cu, Zn, Se, Br, Rb, Sr, Au, La and Ce in different amounts. Comparison of the results with those of reference river fish samples indicated that agricultural rainbow trout samples from Sapanca region have higher Fe level.

Akyuz, T.; Bassari, A.; Bolcal, C.; Sener, E.; Yildiz, M.; Kucer, R.; Kaplan, Z.; Dogan, G.; Akyuz, S.

1999-01-01

254

Pharmacokinetic study of polymeric drugs. Radioisotopic method for pharmacokinetic investigations  

SciTech Connect

The authors examine the radioisotopic procedure possibilities using as example a study of the pharmacokinetics of delta-chymotrypsin (I) labeled with /sup 125/I, (/sup 125/I-I). Labeled /sup 125/I-(I) was obtained by the electrochemical iodination of (I) at constant potential when no appreciable change in the enzymic activity of the preparation occurred. Rats were used in the experiments, and the results are shown of determining radioactivity in their blood and organs. The results of the pharmacokinetic investigation of (I) show the expediency of using the proposed pharmacokinetic model in an operative pharmacokinetic check of polymeric drugs.

Pimenova, G.N.; Matveev, V.A.; Kulakov, V.N.

1987-02-01

255

Improved synchronized accumulating radioisotope detector for gas chromatography.  

PubMed

A synchronized accumulating radioisotope detector for radio gas chromatography was developed. It comprised seven gas-flow proportional counters each with an inner volume of 10 ml. Every counter tube was connected by a mutual anti-coincidence circuit to reduce the background. The transit time of gas particles in one counter tube could be set to an optimal value between 1 and 4 s by regulating the flow-rate of the counting gas, according to analytical requirements. The improved detector maintained high chromatographic resolution, which suggested the applicability of the apparatus to capillary gas chromatography. PMID:2753949

Akira, K; Baba, S

1989-04-14

256

PREFACE: The 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008)  

NASA Astrophysics Data System (ADS)

This volume of Journal of Physics: Conference Series contains invited and contributed peer-reviewed papers that were presented at the 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008), which was held on 7-12 September 2008, at Kunibiki Messe, Matsue, Japan. This triennial symposium has a half-century long history starting from the 1st meeting in 1959 at Asbury Park, New Jersey. We were very pleased to organize ISBB 2008, which gathered chemists, physicists, materials scientists as well as diamond and high-pressure researchers. This meeting had a strong background in the boron-related Japanese research history, which includes the discovery of superconductivity in MgB2 and development of Nd-Fe-B hard magnets and of YB66 soft X-ray monochromator. The scope of ISBB 2008 spans both basic and applied interdisciplinary research that is centered on boron, borides and related materials, and the collection of articles defines the state of the art in research on these materials. The topics are centered on: 1. Preparation of new materials (single crystals, thin films, nanostructures, ceramics, etc) under normal or extreme conditions. 2. Crystal structure and chemical bonding (new crystal structures, nonstoichiometry, defects, clusters, quantum-chemical calculations). 3. Physical and chemical properties (band structure, phonon spectra, superconductivity; optical, electrical, magnetic, emissive, mechanical properties; phase diagrams, thermodynamics, catalytic activity, etc) in a wide range of temperatures and pressures. 4. Applications and prospects (thermoelectric converters, composites, ceramics, coatings, etc) There were a few discoveries of new materials, such as nanomaterials, and developments in applications. Many contributions were related to 4f heavy Fermion systems of rare-earth borides. Exotic mechanisms of magnetism and Kondo effects have been discussed, which may indicate another direction of development of boride. Two special sessions, 'Boron chemistry' and 'Superconductivity', were also held at the symposium. The session on Boron chemistry was planned to honor the scientific work in boron chemistry of Professor J Bauer on the occasion of his retirement. Many recent results were discussed in the session, and Professor Bauer himself introduced novel rare-earth-boron-carbon compounds RE10B7C10 (RE = Gd - Er) in his lecture. In the latter session, on the basis of recent discoveries of superconductivity in MgB2 and in ?-boron under high pressure, the superconductivity of boron and related materials was discussed and the superconductivity of boron-doped diamond was also addressed. More than 120 participants from 16 countries attended the ISBB 2008, and active presentations (22 invited, 33 oral and 68 posters) and discussions suggest that research on boron and borides is entering a new phase of development. This volume contains 46 articles from 52 submitted manuscripts. The reviewers were invited not only from symposium participants but also from specialists worldwide, and they did a great job of evaluating and commenting on the submitted manuscripts to maintain the highest quality standard of this volume. Recent discoveries of superconductivity in boron under high pressure, synthesis of a new allotrope of boron and of various boron and boride nanostructures will lead this highly interdisciplinary field of science, which will further grow and gain attention in terms of both basic and applied research. In this context, we are very much looking forward to the next symposium, which will be held in Istanbul, Turkey, in 2011, organized by Professor Onuralp Yucel, Istanbul Technical University. Turkey currently has the world highest share of borate production and is expected to be involved more in boron-related research. Acknowledgements We gratefully acknowledge the style improvement by Dr K Iakoubovskii, and sincerely thank Shimane Prefecture and Matsue City for their financial support. The symposium was also supported by Tokyo University of Science, Suwa and foundations including, the Kajima Foundat

Tanaka, Takaho

2009-07-01

257

Properties of vacuum-evaporated boron films  

NASA Technical Reports Server (NTRS)

The work on the properties of thin boron films made by vacuum evaporation of elemental boron using an electron beam as the energy source is reported. The program aimed at characterizing the properties of vacuum evaporated films. The work was directed toward those variables considered to be important in affecting the tensile strength of the boron films. In general, the thickness of the films was less than 0.002 in. The temperature of the substrate on which the boron was condensed was found to be most important. Three distinctly different forms of boron deposit were produced. Although the transition temperature was not sharply defined, at substrate temperatures of less than approximately 600 deg C the boron deposits were amorphous to X-ray. If the substrate were highly polished, the deposits were black and mirror-like. For substrates with coefficients of thermal expansion close to that of boron, the deposits were then continuous and uncracked. The studies suggest that the potential continues to exist for film-type composites to have both high strength and high modulus.

Feakes, F.

1973-01-01

258

Liposomes as drug delivery vehicles for boron agents.  

PubMed

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

Hawthorne, M F; Shelly, K

1997-05-01

259

Conditioning of Boron-Containing Low and Intermediate Level Liquid Radioactive Waste - 12041  

SciTech Connect

Improved cementation of low and intermediate level radioactive waste (ILW and LLW) aided by vortex electromagnetic treatment as well as silica addition was investigated. Positive effects including accelerated curing of boron-containing cement waste forms, improve end product quality, decreased product volume and reduced secondary LRW volume from equipment decontamination were established. These results established the possibility of boron-containing LRW cementation without the use of neutralizing alkaline additives that greatly increase the volume of the final product intended for long-term storage (burial). Physical (electromagnetic) treatment in a vortex mixer can change the state of LRW versus chemical treatment. By treating the liquid phase of cement solution only, instead of the whole solution, and using fine powder and nano-particles of ferric oxides instead of separable ferromagnetic cores for the activating agents the positive effect are obtained. VET for 1 to 3 minutes yields boron-containing LRW cemented products of satisfactory quality. Silica addition at 10 % by weight will accelerate curing and solidification and to decrease radionuclide leaching rates from boron-containing cement products. (authors)

Gorbunova, Olga A. [SUE SIA 'Radon', Moscow (Russian Federation); Kamaeva, Tatiana S. [Vernadsky Institute of Geochemistry and Analytical Chemistry Russian Academy of Sciences, Moscow (Russian Federation)

2012-07-01

260

Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition  

Microsoft Academic Search

Uranium dioxide-only and uranium dioxide–gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and

Hasan H. Durmazuçar; Güngör Gündüz

2000-01-01

261

Impurity behavior in boronized Heliotron E  

NASA Astrophysics Data System (ADS)

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

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

1995-04-01

262

Boron distribution in sintered silicon carbide  

SciTech Connect

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

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

1988-01-01

263

GRC Supporting Technology for NASA's Advanced Stirling Radioisotope Generator (ASRG)  

NASA Technical Reports Server (NTRS)

From 1999 to 2006, the NASA Glenn Research Center (GRC) supported a NASA project to develop a high-efficiency, nominal 110-We Stirling Radioisotope Generator (SRG110) for potential use on NASA missions. Lockheed Martin was selected as the System Integration Contractor for the SRG110, under contract to the Department of Energy (DOE). The potential applications included deep space missions, and Mars rovers. The project was redirected in 2006 to make use of the Advanced Stirling Convertor (ASC) that was being developed by Sunpower, Inc. under contract to GRC, which would reduce the mass of the generator and increase the power output. This change would approximately double the specific power and result in the Advanced Stirling Radioisotope Generator (ASRG). The SRG110 supporting technology effort at GRC was replanned to support the integration of the Sunpower convertor and the ASRG. This paper describes the ASRG supporting technology effort at GRC and provides details of the contributions in some of the key areas. The GRC tasks include convertor extended-operation testing in air and in thermal vacuum environments, heater head life assessment, materials studies, permanent magnet characterization and aging tests, structural dynamics testing, electromagnetic interference and electromagnetic compatibility characterization, evaluation of organic materials, reliability studies, and analysis to support controller development.

Schreiber, Jeffrey G.; Thieme, Lanny G.

2008-01-01

264

Technology Development for a Stirling Radioisotope Power System  

NASA Technical Reports Server (NTRS)

NASA Glenn Research Center and the Department of Energy are developing a Stirling convertor for an advanced radioisotope power system to provide spacecraft on-board electric power for NASA deep space missions. NASA Glenn is addressing key technology issues through the use of two NASA Phase II SBIRs with Stirling Technology Company (STC) of Kennewick, WA. Under the first SBIR, STC demonstrated a synchronous connection of two thermodynamically independent free-piston Stirling convertors and a 40 to 50 fold reduction in vibrations compared to an unbalanced convertor. The second SBIR is for the development of an Adaptive Vibration Reduction System (AVRS) that will essentially eliminate vibrations over the mission lifetime, even in the unlikely event of a failed convertor. This paper presents the status and results for these two SBIR projects and also discusses a new NASA Glenn in-house project to provide supporting technology for the overall Stirling radioisotope power system development. Tasks for this new effort include convertor performance verification, controls development, heater head structural life assessment, magnet characterization and thermal aging tests, FEA analysis for a lightweight alternator concept, and demonstration of convertor operation under launch and orbit transfer load conditions.

Thieme, Lanny G.; Qiu, Songgang; White, Maurice A.

2000-01-01

265

Utilizing Radioisotope Power Systems for Human Lunar Exploration  

NASA Technical Reports Server (NTRS)

The Vision for Space Exploration has a goal of sending crewed missions to the lunar surface as early as 2015 and no later than 2020. The use of nuclear power sources could aid in assisting crews in exploring the surface and performing In-Situ Resource Utilization (ISRU) activities. Radioisotope Power Systems (RPS) provide constant sources of electrical power and thermal energy for space applications. RPSs were carried on six of the crewed Apollo missions to power surface science packages, five of which still remain on the lunar surface. Future RPS designs may be able to play a more active role in supporting a long-term human presence. Due to its lower thermal and radiation output, the planned Stirling Radioisotope Generator (SRG) appears particularly attractive for manned applications. The MCNPX particle transport code has been used to model the current SRG design to assess its use in proximity with astronauts operating on the surface. Concepts of mobility and ISRU infrastructure were modeled using MCNPX to analyze the impact of RPSs on crewed mobility systems. Strategies for lowering the radiation dose were studied to determine methods of shielding the crew from the RPSs.

Schreiner, Timothy M.

2005-01-01

266

High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Astrophysics Data System (ADS)

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140° C while the heat losses caused by the addition of the VCHP are 1.8 W.

Tarau, Calin; Walker, Kara L.; Anderson, William G.

2009-03-01

267

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

PubMed

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

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

2001-07-01

268

Boron-10 loaded inorganic shielding material  

NASA Technical Reports Server (NTRS)

Shielding material containing Boron 10 and gadoliunium for neutron absorption has been developed to reduce interference from low energy neutrons in measurement of fission neutron spectrum using Li-6 fast neutron spectrometer.

Baker, S. I.; Ryskiewicz, R. S.

1972-01-01

269

Decreasing the leachibility of boron wood preservatives  

E-print Network

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

Gezer, Engin Derya

2012-06-07

270

Ni doping of semiconducting boron carbide  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

271

Boron strengthening in FeAl  

SciTech Connect

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

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

1998-11-01

272

Ground-state properties of boron-doped diamond  

SciTech Connect

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

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

2008-04-15

273

Boronline, a new generation of boron meter  

SciTech Connect

Rolls-Royce is a global business providing integrated power systems for use on land, at sea and in the air. The Group has a balanced business portfolio with leading market positions - civil aerospace, defence aerospace, marine and energy Rolls-Royce understands the challenges of design, procurement, manufacture, operation and in-service support of nuclear reactor plants, with over 50 years of experience through the Royal Navy submarine programme. Rolls-Royce can therefore offer full product life-cycle management for new civil nuclear installations, as well as support to existing installations, including plant lifetime extensions. Rolls-Royce produced for 40 years, Instrumentation and Control (I and C) systems of and associated services for nuclear reactors in Europe, including 58 French reactors and others situated in the United States and in others countries, such as China. Rolls-Royce equipped in this domain 200 nuclear reactors in 20 countries. Among all of its nuclear systems, Rolls Royce is presenting to the conference its new generation of on-line boron measurement system, so called Boronline. (authors)

Pirat, P. [Rolls-Royce Company, Meylan (France)

2011-07-01

274

Boron thermal/epithermal neutron capture therapy  

SciTech Connect

The development of various particle beams for radiotherapy represents an attempt to improve dose distribution, and to provide high LET radiations which are less sensitive to ambient physical and radiobiological factors such as oxygen tension, cell cycle, and dose rate. In general, a compromise is necessary as effective RBE is reduced in order to spread the dose distribution over the anticipated tumor volume. The approach of delivering stable non-toxic isotopes to tumor, and then activating these atoms subsequently via an external radiation beam has mator advantages; problems associated with high uptake of these isotopes in competing cell pools are obviated, and the general tumor volume can be included in the treatment field of the activating beam. As long as the normal tissues supporting tumor show a low uptake of the isotope to be activated, and as long as the range of the reaction products is short, dose will be restricted to tumor, with a consequent high therapeutic ratio. Neutron Capture Therapy (NCT) is generally carried out by activating boron-10 with low energy neutrons. The range of the high LET, low OER particles from the /sup 10/B(n, ..cap alpha..)/sup 7/Li reaction is approx. 10..mu.., or one cell diameter, a situation that is optimal for cell killing. Significant advantages may be gained by using the NCT procedure in conjunction with improved tissue penetration provided with epithermal or filtered beams, and new compounds showing physiological binding to tumor.

Fairchild, R.G.

1982-01-01

275

High pressure ignition of boron in reduced oxygen atmospheres  

SciTech Connect

Boron ignition delay times for 24 {micro}m diameter particles have been measured behind the reflected shock at a shock tube endwall in reduced oxygen atmospheres and in a combustion bomb at higher pressures in the products of a hydrogen/oxygen/nitrogen reaction. The shock tube study independently varies temperature (1,400 -- 3,200 K), pressure (8.5, 34 atm), and ignition-enhancer additives (water vapor, fluorine compounds). A combustion chamber is used at a peak pressure of 157 atm and temperature in excess of 2,800 K to study ignition delays at higher pressures than are possible in the shock tube.

Foelsche, R.O.; Spalding, M.J.; Burton, R.L.; Krier, H. [Univ. of Illinois, Urbana, IL (United States)

1996-07-01

276

Magnetoresistive junctions based on epitaxial graphene and hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

We propose monolayer epitaxial graphene and hexagonal boron nitride (h-BN) as ultimate thickness covalent spacers for magnetoresistive junctions. Using a first-principles approach, we investigate the structural, magnetic, and spin transport properties of such junctions based on structurally well-defined interfaces with (111) fcc or (0001) hcp ferromagnetic transition metals. We find low resistance area products, strong exchange couplings across the interface, and magnetoresistance ratios exceeding 100% for certain chemical compositions. These properties can be fine tuned, making the proposed junctions attractive for nanoscale spintronics applications.

Yazyev, Oleg V.; Pasquarello, Alfredo

2009-07-01

277

Boron dose determination for BNCT using Fricke and EPR dosimetry  

SciTech Connect

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

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

1995-02-01

278

Molecular marker based characterization and genetic diversity of wheat genotypes in relation to boron efficiency  

Technology Transfer Automated Retrieval System (TEKTRAN)

Boron deficient soils pose a critical problem to wheat production in many areas of the world including Bangladesh and causes significant yield reduction. Therefore, in the present study, 21 diverse wheat (Triticum aestivum L.) genotypes collected from three different countries (Bangladesh, India, a...

279

Abrasive slurry composition for machining boron carbide  

DOEpatents

An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

Duran, E.L.

1984-11-29

280

Abrasive slurry composition for machining boron carbide  

DOEpatents

An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

Duran, Edward L. (Santa Fe, NM)

1985-01-01

281

Determination of boron by (p, a) reaction  

Microsoft Academic Search

A method for boron determination based on 11B(p, a)8Be reaction is described. The irradiations were performed with 800 keV protons and the alphas were counted with 2 PIPS detectors at an angle of 150° to the beam direction. The method is simple and permits the determination of boron at g\\/g level in biological materials and sub-g\\/g level in metals, alloys

C. S. Sastri; V. Iyengar; G. Blondiaux; T. Sauvage; Y. Tessier

2002-01-01

282

Boron Nitride Composites By Chemical Vapor Deposition  

Microsoft Academic Search

Composites of boron nitride (BN) have been made by the chemical vapor deposition (CVD) of a BN matrix on a BN felt fiber substrate. Reactant gases were boron trifluoride and ammonia. The composites have a relatively high density (1.70 g\\/cm3), a crystallite size LC = 150 A and an interlayer spacing d002 = 3.35 A. Measurements of elastic modulus and

Hugh O. Pierson

1975-01-01

283

Potential rare earth free permanent magnet: interstitial boron doped FeCo  

NASA Astrophysics Data System (ADS)

Using the full potential linearized augmented plane wave method, we investigated the structural and the magnetic properties of boron doped FeCo. After fully relaxing the lattice structure, the interatomic distances between boron and Fe atoms were found to be greatly enhanced and the tetragonal distortion was realized due to this increased interatomic distance. Nonetheless, both the unit cell volume and the total magnetic moment of the tetragonally distorted FeCo structure were weakly suppressed compared with those of ideal bulk FeCo. We found a magnetocrystalline anisotropy constant of 0.8 MJ m-3 and this was mainly due to the tetragonal distortion induced by boron impurity, not from the hybridization effect with Fe or Co, because no essential change in the magnetocrystalline anisotropy constant was found even without boron impurity in the lattice distorted system. Additionally, the estimated maximum energy product and coercive field were 100 MGOe and 745 kA m-1, respectively. These results may imply that the interstitial boron doped FeCo can be used for a potential rare earth free permanent magnet although those values are likely to be suppressed in real samples due to micromagnetic factors.

Khan, Imran; Hong, Jisang

2014-10-01

284

Fluorescent sensors based on boronic acids  

NASA Astrophysics Data System (ADS)

Sensor systems have long been needed for detecting the presence in solution of certain chemically or biologically important species. Sensors are used in a wide range of applications from simple litmus paper that shows a single color change in acidic or basic environments to complex biological assays that use enzymes, antibodies and antigens to display binding events. With this work the use of boronic acids in the design and synthesis of sensors for saccharides (diols) will be presented. The fluorescent sensory systems rely on photoinduced electron transfer (PET) to modulate the observed fluorescence. When saccharides form cyclic boronate esters with boronic acids, the Lewis acidity of the boronic acid is enhanced and therefore the Lewis acid-base interaction between the boronic acid and a neighboring amine is strengthened. The strength of this acid-base interaction modulates the PET from the amine (acting as a quencher) to anthracene (acting as a fluorophore). These compounds show increased fluorescence at neutral pH through suppression of the PET from nitrogen to anthracene on saccharide binding. The general strategy for the development of saccharide selective systems will be discussed. The potential of the boronic acid based systems will be illustrated using the development of glucose and glucosamine selective fluorescent sensors as examples.

Cooper, Christopher R.; James, Tony D.

1999-05-01

285

Boronization on NSTX using Deuterated Trimethylboron  

SciTech Connect

Boronization on the National Spherical Torus Experiment (NSTX) has proved to be quite beneficial with increases in confinement and density, and decreases in impurities observed in the plasma. The boron has been applied to the interior surfaces of NSTX, about every 2 to 3 weeks of plasma operation, by producing a glow discharge in the vacuum vessel using deuterated trimethylboron (TMB) in a 10% mixture with helium. Special NSTX requirements restricted the selection of the candidate boronization method to the use of deuterated boron compounds. Deuterated TMB met these requirements, but is a hazardous gas and special care in the execution of the boronization process is required. This paper describes the existing GDC, Gas Injection, and Torus Vacuum Pumping System hardware used for this process, the glow discharge process, and the automated control system that allows for remote operation to maximize both the safety and efficacy of applying the boron coating. The administrative requirements and the detailed procedure for the setup, operation and shutdown of the process are also described.

W.R. Blanchard; R.C. Gernhardt; H.W. Kugel; P.H. LaMarche

2002-01-28

286

Boosting activation of oxygen molecules on c60 fullerene by boron doping.  

PubMed

The activation of oxygen molecules on boron-doped C60 fullerene (C59 B) and the subsequent water formation reaction are systematically investigated by using hybrid density functional calculations. Results indicate that C59 B shows a favorable ability to activate oxygen molecules both kinetically and thermodynamically. The oxygen molecule is first adsorbed on the boron atom, which is identified to be the most reactive site in C59 B for O2 adsorption because of its high positive charge and spin density. The adsorption structure C59 B?O2 can further isomerize to form two products with small reaction barriers. Water formation reactions upon these two structures are energetically favorable and suggest a four-electron mechanism for the oxygen reduction reaction catalyzed by C59 B. This work provides a reliable theoretical insight into the catalytic properties of boron-doped fullerene, which is believed to be helpful to explore fullerene catalysts. PMID:25399745

Li, Qiao-Zhi; Zheng, Jia-Jia; Dang, Jing-Shuang; Zhao, Xiang

2015-02-01

287

Space radioisotope power source requirements update and technology status  

SciTech Connect

The requirements for a space advanced radioisotope power source are based on potential deep space missions being investigated for the NASA Advanced Space Systems Development Program. Since deep space missions have not been approved, updating requirements is a continuos parallel process of designing the spacecraft and the science instruments to accomplish the potential missions and developing the power source technology to meet changing requirements. There are at least two potential missions, Pluto/Kuiper Express and Europa Orbiter, which may require space advanced radioisotope power sources. The Europa Orbiter has been selected as the preferred first potential mission. However the final decision will depend on the technology readiness of all the subsystems and the project must be able to switch to Pluto Kuiper Express as the first mission as late as the beginning of fiscal year 2000. Therefore the requirements for the power source will cover both potential missions. As the deep space spacecraft design evolves to meet the science requirements and the Alkali Metal Thermal to Electric (AMTEC) technology matures the advanced radioisotope power source design requirements are updated The AMTEC technology developed to date uses stainless steel for the sodium containment material. The higher efficiency required for the space power system dictates that the AMTEC technology must operate at a higher temperature than possible with stainless steel. Therefore refractory materials have been selected as the baseline material for the AMTEC cell. These refractory materials are Nb1Zr for the hot side and Nb1Zr or Nb10Hf1Ti for the cold side. These materials were selected so the AMTEC cell can operate at 1150K to 1350K hot side temperature and 600K to 700K cold side temperature and meet the present power and mass requirements using four to six general purpose heat source modules as the heat source. The new containment materials and brazes will be evaluated as to lifetime, compatibility and performance with the AMTEC beta prime Alumina, the TiN electrodes, the sodium and the molybdenum current collectors. AMTEC cell components and cells will be built with the baseline containment materials and brazes and tested to determine the performance as a function of temperature. These containment materials will be also be tested with all the other AMTEC components to determine acceleration factors needed to predict AMTEC performance degradation and failure as a function of operating time at temperature.

Mondt, J.F.

1998-07-01

288

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management  

NASA Technical Reports Server (NTRS)

An advantage of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used for a number of beneficial purposes including: maintaining electronic components within a controlled temperature range, warming propulsion tanks and mobility actuators, and maintaining liquid propellants above their freezing temperature. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated large quantities of waste heat due to the low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-Watt Stirling Radioisotope Generator (SRG110) will have higher conversion efficiencies, thereby rejecting less waste heat at a lower temperature and may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of 6 to 7 percent, reject their waste heat at the relatively high heat rejection temperature of 200 C. This is an advantage when rejecting heat to space; however, transferring heat to the internal spacecraft components requires a large and heavy radiator heat exchanger. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation of the RTG. The SRG110, with an efficiency around 22 percent and 50 C nominal housing surface temperature, can readily transfer the available waste heat directly via heat pipes, thermal straps, or fluid loops. The lower temperatures associated with the SRG110 avoid the chances of overheating other scientific components, eliminating the need for thermal shields. This provides the spacecraft designers more flexibility when locating the generator for a specific mission. A common misconception with high-efficiency systems is that there is not enough waste heat for spacecraft thermal management. This paper will dispel this misconception and investigate the use of a high-efficiency SRG110 for spacecraft thermal management and outline potential methods of waste heat utilization in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander). The advantages associated with the SRG110 as they relate to ease of assembly, less complex interfaces, and overall mass savings for a spacecraft will be highlighted.

Pantano, David R.; Dottore, Frank; Tobery, E. Wayne; Geng, Steven M.; Schreiber, Jeffrey G.; Palko, Joseph L.

2005-01-01

289

Theoretical dosimetry estimations for radioisotopes produced by proton-induced reactions on natural and enriched molybdenum targets.  

PubMed

This study presents a summary of the dosimetry calculations performed for three technetium agents most commonly used in nuclear medicine diagnostic studies, namely sestamibi™, phosphonates and pertechnetate, labeled with cyclotron-produced technetium. Calculated patient doses were compared to those that would be delivered by the same radiotracers labeled with technetium obtained from a generator produced in a reactor. The main difference is that technetium from a generator is pure, i.e. contains only (99m)Tc and its decay product (99g)Tc, while in a cyclotron a large number of other stable and radioactive isotopes are created. In our calculations only technetium radioisotopes (ground and isomeric states) were considered as they will be included in the radiotracer labeling process and will contribute to the patient dose. Other elements should be removed by chemical purification. These dose estimates are based on our theoretical calculations of the proton-induced reaction cross sections and radioisotope production yields. Thick targets of enriched (three different compositions) and natural molybdenum, and three initial beam energies (16, 19 and 24 MeV) were considered for irradiation times of 3, 6 and 12 h with a beam current of 200 µA. The doses were calculated for injection times corresponding to 0, 2, 8, 12 and 24 h after the end of beam. PMID:22391011

Hou, X; Celler, A; Grimes, J; Bénard, F; Ruth, T

2012-03-21

290

Boron site preference in ternary Ta and Nb boron silicides  

SciTech Connect

X-ray single crystal (XSC) and neutron powder diffraction data (NPD) were used to elucidate boron site preference for five ternary phases. Ta{sub 3}Si{sub 1-x}B{sub x} (x=0.112(4)) crystallizes with the Ti{sub 3}P-type (space group P4{sub 2}/n) with B-atoms sharing the 8g site with Si atoms. Ta{sub 5}Si{sub 3-x} (x=0.03(1); Cr{sub 5}B{sub 3}- type) crystallizes with space group I4/mcm, exhibiting a small amount of vacancies on the 4a site. Both, Ta{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.568(3), and Nb{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.59(2), are part of solid solutions of M{sub 5}Si{sub 3} with Cr{sub 5}B{sub 3}-type into the ternary M-Si-B systems (M=Nb or Ta) with B replacing Si on the 8h site. The D8{sub 8}-phase in the Nb-Si-B system crystallizes with the Ti{sub 5}Ga{sub 4}-type revealing the formula Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292(3)) with B partially filling the voids in the 2b site of the Mn{sub 5}Si{sub 3} parent type. - Graphical abstract: The crystal structures of a series of compounds have been solved from X-ray single crystal diffractometry revealing details on the boron incorporation. Highlights: Black-Right-Pointing-Pointer Structure of a series of compounds have been solved by X-ray single crystal diffractometry. Black-Right-Pointing-Pointer Ta{sub 3}(Si{sub 1-x}B{sub x}) (x=0.112) crystallizes with the Ti{sub 3}P-type, B and Si atoms randomly share the 8g site. Black-Right-Pointing-Pointer Structure of Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292; Ti{sub 5}Ga{sub 4}-type) was solved from NPD.

Khan, Atta U. [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Nunes, Carlos A. [Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo (USP), Polo Urbo-Industrial Gleba AI-6, Caixa Postal 116, 12602-810 Lorena, SP (Brazil); Coelho, Gilberto C. [Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo (USP), Polo Urbo-Industrial Gleba AI-6, Caixa Postal 116, 12602-810 Lorena, SP (Brazil); Mestrado Profissional em Materiais, Centro Universitario de Volta Redonda, Av. Paulo Erlei Alves Abrantes 1325, 27240-560 Volta Redonda-RJ (Brazil); Suzuki, Paulo A. [Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo (USP), Polo Urbo-Industrial Gleba AI-6, Caixa Postal 116, 12602-810 Lorena, SP (Brazil); Grytsiv, Andriy [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Bourree, Francoise [Laboratoire L. Brillouin, CEA/Saclay, F-91191 Gif sur Yvette (France); Giester, Gerald [Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse14, A-1090 Wien (Austria); Rogl, Peter F., E-mail: peter.franz.rogl@univie.ac.at [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria)

2012-06-15

291

Development of a boron buffered solution culture system for controlled studies of plant boron nutrition  

Microsoft Academic Search

Chelated-buffered nutrient solutions are used for studies on micronutrient metals but so far no equivalent system exists for boron nutrition studies: the present investigation was initiated with that intention. From a literature review, it was noted that a range of substances form chelates with boron including polyhydric alcohols, sugars and phenolic compounds. However, none apart from hydrofluoric acid formed chelates

A. Asad; R. W. Bell; L. Huang

1997-01-01

292

Properties of thin boron coatings formed during deuterated-boronization in JT-60  

NASA Astrophysics Data System (ADS)

Since 1992, the boronization using B10H14 (decaborane-based boronization) has been utilized in JT-60 once or twice a year. It is very effective in reducing both the impurities, like oxygen and carbon, in the plasma and in recycling fuel particles. However, we needed ˜ 500 discharges to exchange hydrogen in the boron film for deuterium, after the boronization using only He for a dilution gas. Using a mixed-dilution gas of He and deuterium, we made the boronized film on JT-60 first wall (deuterated-boronization). A typical composition of working gas was 2% B 10H 14, 38% D 2 and 60% He, which was used in a flow through situation. The amounts of hydrogen and deuterium in the boronized film were evaluated to be ˜ 5 and ˜ 30 at%, respectively. In addition, the deuteration factor of {D}/{(H + D)} in the first plasma after the boronization increased from less than 0.2 to 0.8. Thus, we can drastically reduce the number of the conditioning discharges from ˜ 500 to ˜ 50 for the isotope-exchange before D plasma experiments.

Yagyu, J.; Ogiwara, N.; Saidoh, M.; von Seggern, J.; Okabe, T.; Miyo, Y.; Hiratsuka, H.; Yamamoto, S.; Goppelt-Langer, P.; Aoki, Y.; Takeshita, H.; Naramoto, H.

1997-02-01

293

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 ...

294

Cross section measurements of proton and deuteron induced reactions on natural europium and yields of SPECT-relevant radioisotopes of gadolinium.  

PubMed

The existing cross section data of the (nat)Eu(d,x) and (nat)Eu(p,x) reactions relevant for the production of (147,149)Gd were expanded up to 70.9 MeV and 44.8 MeV, respectively. Integral yields of radiogadolinium were calculated, showing production rates higher than for the earlier proposed irradiation of highly enriched (144)Sm with ?- or (3)He-particles. The formation of radioisotopic impurities like (151)Gd (T(1/2)=124 d) and (153)Gd (T(1/2)=240 d) was below 5%. Production of (147,)(149)Gd using enriched europium is also discussed. PMID:24880528

Buchholz, Martin; Spahn, Ingo; Coenen, Heinz H

2014-09-01

295

The energy landscape of fullerene materials: a comparison between boron, boron-nitride and carbon  

E-print Network

Using the minima hopping global geometry optimization method on the density functional potential energy surface we study medium size and large boron clusters. Even though for isolated medium size clusters the ground state is a cage like structure they are unstable against external perturbations such as contact with other clusters. The energy landscape of larger boron clusters is glass like and has a large number of structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers in our minima hopping runs. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found.

De, Sandip; Amsler, Maximilian; Pochet, Pascal; Genovese, Luigi; Goedecker, Stefan

2010-01-01

296

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions.  

PubMed

Diethanolamine complexed heterocyclic boronic acids (DABO boronates) are air-stable reagents that can be used directly in Suzuki-Miyaura reactions in the presence of water or a protic co-solvent. Interestingly, heterocyclic DABO boronates can be stored for extended periods of time at room temperature with no noticeable degradation, unlike their boronic acid counterparts. Heterocyclic DABO boronates constitute an operationally simple and efficient alternative to other boronic acid derivatives as coupling partners in palladium catalyzed cross-coupling reactions under standard Suzuki-Miyaura conditions. PMID:24371372

Reilly, Maureen K; Rychnovsky, Scott D

2011-10-01

297

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions  

PubMed Central

Diethanolamine complexed heterocyclic boronic acids (DABO boronates) are air-stable reagents that can be used directly in Suzuki-Miyaura reactions in the presence of water or a protic co-solvent. Interestingly, heterocyclic DABO boronates can be stored for extended periods of time at room temperature with no noticeable degradation, unlike their boronic acid counterparts. Heterocyclic DABO boronates constitute an operationally simple and efficient alternative to other boronic acid derivatives as coupling partners in palladium catalyzed cross-coupling reactions under standard Suzuki-Miyaura conditions. PMID:24371372

Reilly, Maureen K.

2013-01-01

298

Radioisotope cisternography in spontaneous CSF leaks: interpretations and misinterpretations.  

PubMed

A broadening of the clinical and imaging features of the spontaneous cerebrospinal fluid (CSF) leaks is now well recognized, far beyond what was thought only two decades ago. This has resulted in increasing number of patients with atypical and unusual features who, not unexpectedly, are directed to headache specialists and tertiary referral centers. In many cases, obviously the fundamental question of presence or absence of CSF leak will need to be addressed prior to proceeding with further and often more involved, more invasive, and more costly diagnostic and therapeutic considerations. Radioisotope cisternography often proves to be very helpful in these situations by demonstrating reliable, although indirect, evidences of CSF leak while it is less helpful in directly identifying the exact site of the CSF leakage. In this overview article, the expectations from and the limitations of this diagnostic method are described along with some personal observations in the past 25 years. PMID:25041119

Mokri, Bahram

2014-09-01

299

End-on radioisotope thermoelectric generator impact tests  

NASA Astrophysics Data System (ADS)

The General-Purpose Heat Source (GPHS) provides power for space missions by transmitting the heat of 238Pu decay to an array of thermoelectric elements in a radioisotope thermoelectric generator (RTG). The modular GPHS design was developed to address both survivability during launch abort and return from orbit. The first two RTG Impact Tests were designed to provide information on the response of a fully loaded RTG to end-on impact against a concrete target. The results of these tests indicated that at impact velocities up to 57 m/s the converter shell and internal components protect the GPHS capsules from excessive deformation. At higher velocities, some of the internal components of the RTG interact with the GPHS capsules to cause excessive localized deformation and failure.

Reimus, M. A. H.; Hinckley, J. E.

1997-01-01

300

AMTEC radioisotope power system for the Pluto Express mission  

SciTech Connect

The Alkali Metal Thermal to Electric Converter (AMTEC) technology has made substantial advances in the last 3 years through design improvements and technical innovations. In 1993 programs began to produce an AMTEC cell specifically for the NASA Pluto Express Mission. A set of efficiency goals was established for this series of cells to be developed. According to this plan, cell {number_sign}8 would be 17% efficient but was actually 18% efficient. Achieving this goal, as well as design advances that allow the cell to be compact, has resulted in pushing the cell from an unexciting 2 W/kg and 2% efficiency to very attractive 40 W/kg and 18% measured efficiency. This paper will describe the design and predict the performance of a radioisotope powered AMTEC system for the Pluto Express mission.

Ivanenok, J.F. III; Sievers, R.K. [Advanced Modular Power Systems, Inc., Ann Arbor, MI (United States)

1995-12-31

301

Development and Buildup of a Stirling Radioisotope Generator Electrical Simulator  

NASA Technical Reports Server (NTRS)

This paper describes the development of a Stirling Radioisotope Generator (SRG) Simulator for use in a prototype lunar robotic rover. The SRG developed at NASA Glenn Research Center (GRC) is a promising power source for the robotic exploration of the sunless areas of the moon. The simulator designed provides a power output similar to the SRG output of 5.7 A at 28 Vdc, while using ac wall power as the input power source. The designed electrical simulator provides rover developers the physical and electrical constraints of the SRG supporting parallel development of the SRG and rover. Parallel development allows the rover design team to embrace the SRG s unique constraints while development of the SRG is continued to a flight qualified version.

Prokop, Norman F.; Krasowski, Michael J.; Greer, Lawrence C.; Flatico, Joseph M.; Spina, Dan C.

2008-01-01

302

Reliability Demonstration Approach for Advanced Stirling Radioisotope Generator  

NASA Technical Reports Server (NTRS)

Developed for future space missions as a high-efficiency power system, the Advanced Stirling Radioisotope Generator (ASRG) has a design life requirement of 14 yr in space following a potential storage of 3 yr after fueling. In general, the demonstration of long-life dynamic systems remains difficult in part due to the perception that the wearout of moving parts cannot be minimized, and associated failures are unpredictable. This paper shows a combination of systematic analytical methods, extensive experience gained from technology development, and well-planned tests can be used to ensure a high level reliability of ASRG. With this approach, all potential risks from each life phase of the system are evaluated and the mitigation adequately addressed. This paper also provides a summary of important test results obtained to date for ASRG and the planned effort for system-level extended operation.

Ha, CHuong; Zampino, Edward; Penswick, Barry; Spronz, Michael

2010-01-01

303

Directionality in the GammaTracker Handheld Radioisotope Identifier  

SciTech Connect

Several computationally simple methods are presented for determining the direction to one or more point sources using the GammaTracker handheld radioisotope identifier. GammaTracker will display a heading indicating the direction to one or more sources; no gamma-ray images will be displayed to the user. The details of each directionality method are presented and performance is compared using radiation transport simulations of gamma-ray point sources at varying activity levels on a natural background. All methods achieved sufficiently high pointing accuracy and precision in the tested scenarios, which included background-to-source ratios up to 10:1. The prospects for implementation in the GammaTracker firmware architecture are discussed.

Seifert, Carolyn E.; Myjak, Mitchell J.

2009-06-01

304

Production, distribution and applications of californium-252 neutron sources.  

PubMed

The radioisotope 252Cf is routinely encapsulated into compact, portable, intense neutron sources with a 2.6-yr half-life. A source the size of a person's little finger can emit up to 10(11) neutrons s(-1). Californium-252 is used commercially as a reliable, cost-effective neutron source for prompt gamma neutron activation analysis (PGNAA) of coal, cement and minerals, as well as for detection and identification of explosives, land mines and unexploded military ordinance. Other uses are neutron radiography, nuclear waste assays, reactor start-up sources, calibration standards and cancer therapy. The inherent safety of source encapsulations is demonstrated by 30 yr of experience and by US Bureau of Mines tests of source survivability during explosions. The production and distribution center for the US Department of Energy (DOE) Californium Program is the Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory (ORNL). DOE sells 252Cf to commercial reencapsulators domestically and internationally. Sealed 252Cf sources are also available for loan to agencies and subcontractors of the US government and to universities for educational, research and medical applications. The REDC has established the Californium User Facility (CUF) for Neutron Science to make its large inventory of 252Cf sources available to researchers for irradiations inside uncontaminated hot cells. Experiments at the CUF include a land mine detection system, neutron damage testing of solid-state detectors, irradiation of human cancer cells for boron neutron capture therapy experiments and irradiation of rice to induce genetic mutations. PMID:11003521

Martin, R C; Knauer, J B; Balo, P A

2000-01-01

305

Pathway of radioisotopes from land surface to sewage sludge  

NASA Astrophysics Data System (ADS)

Radioactive surface contaminations will only partially remain at the original location - a fraction of the inventory will take part in (mainly terrestrial and aquatic) environmental transport processes. The probably best known and most important process comprises the food chain. Besides, the translocation of dissolved and particle-bound radioisotopes with surface waters plays an important role. These processes can have the effect of displacing large radioisotope amounts over considerable distances and of creating new sinks and hot spots, as it is already known for sewage sludge. We are reporting on a combined modeling and experimental project concerning the transport of I-131 and Cs-134/Cs-137 FDNPP 2011 depositions in the Fukushima Prefecture. Well-documented experimental data sets are available for surface deposition and sewage sludge concentrations. The goal is to model the pathway in between, involving surface runoff, transport in the sewer system and processes in the sewage treatment plant. Watershed runoff and sewer transport will be treated with models developed recently by us in other projects. For sewage treatment processes a new model is currently being constructed. For comparison and further validation, historical data from Chernobyl depositions and tracer data from natural and artificial, e.g. medical, isotopes will be used. First results for 2011 data from Fukushima Prefecture will be presented. The benefits of the study are expected to be two-fold: on one hand, the abundant recent and historical data will help to develop and improve environmental transport models; on the other hand, both data and models will help in identifying the most critical points in the envisaged transport pathways in terms of radiation protection and waste management.

Fischer, Helmut W.; Yokoo, Yoshiyuki

2014-05-01

306

A high power, Coated Particle Fuel Compact Radioisotope Heat Unit  

NASA Astrophysics Data System (ADS)

A Coated Particle Fuel Compact, Radioisotope Heater Unit (CPFC-RHU) is proposed, which is capable of generating thermal power in excess of 27 W. This power output is more than four times that of a Hexa-RHU, which generates only six watts of thermal power. The design of the CPFC-RHU is identical to that of the Hexa-RHU, except that the six Pt-30Rh clad fuel pellets and the POCO graphite support in the latter are replaced with single-sized, ZrC coated, 238PuO2 fuel particles ~500 ?m in diameter. In addition to fully retaining the helium gas generated by the radioactive decay of the fuel, the CPFC offers promise for enhanced safety. Thermal analyses of the CPFC-RHU show that while the Hexa-RHU is suitable for use in a radioisotope power system (RPS) operating at a converter hot-side temperature of 473 K, the CPFC-RHU could also be used at higher temperatures of 773 K and 973 K with a thermal efficiency >60%. Even at a 473 K converter hot-side temperature, the CPFC-RHU offers higher thermal efficiency (>90%) than the Hexa-RHU (~75%). The CPFC-RHU final design provides constant temperature, with almost uniform radial heat flux to the converter, for enhanced performance, better integration, and higher overall efficiency of the RPS. The present CPFC-RHU fills a gap in the power needs for future space missions requiring electric power of 1-15 W, from a single RPS. .

King, Jeffrey C.; El-Genk, Mohamed S.

2001-02-01

307

INTRACORPOREAL HEAT DISSIPATION FROM A RADIOISOTOPE-POWERED ARTIFICIAL HEART  

PubMed Central

The feasibility of radioisotope-fueled circulatory support systems depends on the ability of the body to dissipate the reject heat from the power source driving the blood pump as well as to tolerate chronic intracorporeal radiation. Our studies have focused on the use of the circulating blood as a heat sink. Initial in vivo heat transfer studies utilized straight tube heat exchangers (electrically and radioisotope energized) to replace a segment of the descending aorta. More recent studies have used a left ventricular assist pump as a blood-cooled heat exchanger. This approach minimizes trauma, does not increase the area of prosthetic interface with the blood, and minimizes system volume. Heat rejected from the thermal engine (vapor or gas cycle) is transported from the nuclear power source in the abdomen to the pump in the thoracic cavity via hydraulic lines. Adjacent tissue is protected from the fuel capsule temperature (900 to 1200°F) by vacuum foil insulation and polyurethane foam. The in vivo thermal management problems have been studied using a simulated thermal system (STS) which approximates the heat rejection and thermal transport mechanisms of the nuclear circulatory support systems under development by NHLI. Electric heaters simulate the reject heat from the thermal engines. These studies have been essential in establishing the location, suspension, surgical procedures, and postoperative care for implanting prototype nuclear heart assist systems in calves. The pump has a thermal impedance of 0.12°C/watt. Analysis of the STS data in terms of an electrical analog model implies a heat transfer coefficient of 4.7 × 10?3 watt/cm2°C in the abdomen compared to a value of 14.9 × 10?3 watt/cm2°C from the heat exchanger plenum into the diaphragm. Images PMID:15215968

Huffman, Fred N.; Hagen, Kenneth G.; Whalen, Robert L.; Fuqua, John M.; Norman, John C.

1974-01-01

308

Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Astrophysics Data System (ADS)

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) was designed to allow multiple stops and restarts of the Stirling engine. A VCHP was designed for the Advanced Stirling Radioisotope Generator, with a 850 °C heater head temperature. The VCHP turns on with a ?T of 30 °C, which is high enough to not risk standard ASRG operation but low enough to save most heater head life. This VCHP has a low mass, and low thermal losses for normal operation. In addition to the design, a proof-of-concept NaK VCHP was fabricated and tested. While NaK is normally not used in heat pipes, it has an advantage in that it is liquid at the reservoir operating temperature, while Na or K alone would freeze. The VCHP had two condensers, one simulating the heater head, and the other simulating the radiator. The experiments successfully demonstrated operation with the simulated heater head condenser off and on, while allowing the reservoir temperature to vary over 40 to 120 °C, the maximum range expected. In agreement with previous NaK heat pipe tests, the evaporator ?T was roughly 70 °C, due to distillation of the NaK in the evaporator.

Anderson, William G.; Tarau, Calin

2008-01-01

309

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

310

Boron in Very Metal-Poor Stars  

E-print Network

We have observed the B I 2497 A line to derive the boron abundances of two very metal-poor stars selected to help in tracing the origin and evolution of this element in the early Galaxy: BD +23 3130 and HD 84937. The observations were conducted using the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. A very detailed abundance analysis via spectral synthesis has been carried out for these two stars, as well as for two other metal-poor objects with published spectra, using both Kurucz and OSMARCS model photospheres, and taking into account consistently the NLTE effects on the line formation. We have also re-assessed all published boron abundances of old disk and halo unevolved stars. Our analysis shows that the combination of high effective temperature (Teff > 6000 K, for which boron is mainly ionized) and low metallicity ([Fe/H]<-1) makes it difficult to obtain accurate estimates of boron abundances from the B I 2497 A line. This is the case of HD 84937 and three other published objects (including two stars with [Fe/H] ~ -3), for which only upper limits can be established. BD +23 3130, with [Fe/H] ~ -2.9 and logN(B)_NLTE=0.05+/-0.30, appears then as the most metal-poor star for which a firm measurement of the boron abundance presently exists. The evolution of the boron abundance with metallicity that emerges from the seven remaining stars with Teff < 6000 K and [Fe/H]<-1, for which beryllium abundances were derived using the same stellar parameters, shows a linear increase with a slope ~ 1. Furthermore, the B/Be ratio found is constant at a value ~ 20 for stars in the range -3<[Fe/H]<-1. These results point to spallation reactions of ambient protons and alpha particles with energetic particles enriched in CNO as the origin of boron and beryllium in halo stars.

R. J. Garcia Lopez; D. L. Lambert; B. Edvardsson; B. Gustafsson; D. Kiselman; R. Rebolo

1998-01-16

311

Hypoxia-selective compounds for boron neutron capture therapy  

E-print Network

Boron neutron capture therapy (BNCT) is a biochemically targeted form of radiotherapy for cancer. In BNCT, a compound labeled with the stable isotope boron-10 is systemically administered, and tumor cells selectively uptake ...

Shah, Jungal (Jugal Kaushik)

2008-01-01

312

Doping and Raman Characterization of Boron and Phosphorus Atoms in  

E-print Network

Doping and Raman Characterization of Boron and Phosphorus Atoms in Germanium Nanowires Naoki Fukata. The chemical bonding states and electrical activity of boron (B) and phosphorus (P) atoms in germanium

Wang, Zhong L.

313

Edinburgh Research Explorer Organotrifluoroborate Hydrolysis: Boronic Acid Release  

E-print Network

Edinburgh Research Explorer Organotrifluoroborate Hydrolysis: Boronic Acid Release Mechanism, 'Organotrifluoroborate Hydrolysis: Boronic Acid Release Mechanism and an Acid­Base Paradox in Cross-Coupling' Journal immediately and investigate your claim. Download date: 16. Sep. 2014 #12;Organotrifluoroborate Hydrolysis

Millar, Andrew J.

314

Branched Polymeric Media: Boron-Chelating Resins from Hyperbranched Polyethylenimine  

E-print Network

-purity magnesium oxides by pyrohydrolysis of magnesium chloride (MgCl2.) brine, excess boron (>10 mg/ L magnesium oxide from brines, and (iv) nuclear power generation.1-4 Boron is an essential nutrient for plants

Goddard III, William A.

315

Pyrolytic decomposition of ammonia borane to boron nitride.  

PubMed

The thermal decomposition of ammonia borane was studied using a variety of methods to qualitatively identify gas and remnant solid phase species after thermal treatments up to 1500 °C. At about 110 °C, ammonia borane begins to decompose yielding H(2) as the major gas phase product. A two step decomposition process leading to a polymeric -[NH?BH](n)- species above 130 °C is generally accepted. In this comprehensive study of decomposition pathways, we confirm the first two decomposition steps and identify a third process initiating at 1170 °C which leads to a semicrystalline hexagonal phase boron nitride. Thermogravimetric analysis (TGA) was used to identify the onset of the third step. Temperature programmed desorption-mass spectroscopy (TPD-MS) and vacuum line methods identify molecular aminoborane (H(2)N?BH(2)) as a species that can be released in appreciable quantities with the other major impurity, borazine. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the chemical states present in the solid phase material after each stage of decomposition. The boron nitride product was examined for composition, structure, and morphology using scanning Auger microscopy (SAM), powder X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Thermogravimetric Analysis-Mass Spectroscopy (TGA-MS) and Differential Scanning Calorimetry (DSC) were used to identify the onset temperature of the first two mass loss events. PMID:21182274

Frueh, Samuel; Kellett, Richard; Mallery, Carl; Molter, Trent; Willis, William S; King'ondu, Cecil; Suib, Steven L

2011-02-01

316

Radioisotope generators for nuclear medicine based on Fajans adsorption on glass microspheres  

SciTech Connect

Several radioisotope generator systems exist in which the carrier-free daughter product would precipitate if present in macro amounts at pH levels at which the parent is soluble. Included among these are the {sup 68}Ge/{sup 68}Ga, {sup 90}Sr/{sup 90}Y, and {sup 47}Ca/{sup 47}Sc pairs. This paper reveals that in these systems, chemical separation can be achieved by Fajans adsorption of the radiocolloidal daughter products onto surfaces such as activated glass microspheres at an appropriate pH. This is followed by washing to remove the parent solution and desorption of the daughter crop by acid washes. Investigation of the Ge/Ga and Sr/Y systems demonstrated that this solid-phase extraction method is erratic, but can give daughter yields as high at 89% with separation factors up to {approximately} 10,000 form parent isotope. This method has the potential for producing daughter isotopes with a minimum of metal and organic impurities for labeling cells, receptor binding ligands, and antibodies for diagnostic and radiotherapeutic purposes.

Ehrhardt, G.J.; Symes, S.; Guimon, R.K.; Zinn, K.R. (Univ. of Missouri, Research Reactor, Columbia, MO (US))

1992-04-01

317

The ?-ray and cosmic ray connection: Ulysses HET secondary radioisotope measurements and cosmic ray propagation  

NASA Astrophysics Data System (ADS)

Cosmic rays constitute a super-thermal gas of charged particles magnetically confined within the Galaxy. Cosmic ray nuclei and electrons are a principal source of the diffuse ?-ray background in the Galaxy. Thus, understanding diffuse ?-ray production is directly related to understanding cosmic ray propagation in the Galaxy. While propagating though the interstellar medium (ISM), cosmic ray nuclei undergo nuclear spallation reactions, producing both stable and unstable secondary nuclei. Measurements of secondary radioisotopes are crucial tests of cosmic ray propagation. The abundances of some radioactive secondary isotopes (10Be, 26Al, 36Cl, etc.) measure the average density of material cosmic rays traverse and relate to the confinement times of cosmic rays in the Galaxy. The abundances of electron capture isotopes and their daughter nuclei (for example, 49V and 51V) test the role of cosmic ray reacceleration. The Ulysses High Energy Telescope (HET) is a cosmic ray isotope spectrometer with sufficient mass resolution (~0.28 u at Fe) and collecting area to measure these rare isotopes. The latest HET measurements of the radioactive secondary cosmic ray isotopes are given, and the implications for cosmic ray propagation and diffuse ?-ray production are discussed. .

Connell, J. J.; Simpson, J. A.

2000-04-01

318

The Modification of Polyurethane Foams Using New Boroorganic Polyols (II) Polyurethane Foams from Boron-Modified Hydroxypropyl Urea Derivatives  

PubMed Central

The work focuses on research related to determination of application possibility of new, ecofriendly boroorganic polyols in rigid polyurethane foams production. Polyols were obtained from hydroxypropyl urea derivatives esterified with boric acid and propylene carbonate. The influence of esterification type on properties of polyols and next on polyurethane foams properties was determined. Nitrogen and boron impacts on the foams' properties were discussed, for instance, on their physical, mechanical, and electric properties. Boron presence causes improvement of dimensional stability and thermal stability of polyurethane foams. They can be applied even at temperature 150°C. Unfortunately, introducing boron in polyurethanes foams affects deterioration of their water absorption, which increases as compared to the foams that do not contain boron. However, presence of both boron and nitrogen determines the decrease of the foams combustibility. Main impact on the decrease combustibility of the obtained foams has nitrogen presence, but in case of proper boron and nitrogen ratio their synergic activity on the combustibility decrease can be easily seen. PMID:24587721

2014-01-01

319

Investigations on boron levels in drinking water sources in China  

Microsoft Academic Search

To evaluate boron contamination of public drinking water in China, both dissolved and total boron contents in 98 public drinking\\u000a water sources from 49 cities, 42 brands of bottled water samples from supermarkets in several cities, and 58 water samples\\u000a from boron industrial area were measured by inductively coupled plasma-mass spectrometry (ICP-MS). Our experimental results\\u000a showed that boron existed in

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

2010-01-01

320

Physical and chemical properties of boronic acids: Formulation implications  

E-print Network

, The University of Kansas Background Effect of Polyols on Boronic Acid pKa Values Conclusions Purpose Solubility ReferencesAcknowledgements Boronic acid compounds are the focus of increasing interest as therapeutic agents due to their ability to inhibit enzyme... of this increased solubility is a pKa lowering effect that polyols impart to boronic acids (Figure 3). The mechanism by which polyols help solubilize boronic acid containing compounds is not completely understood and deserves further study. The authors would like...

Marinaro, W. A.; Stella, Valentino J.

2006-10-25

321

Polyethylene/Boron Composites for Radiation Shielding Applications  

NASA Astrophysics Data System (ADS)

Multifunctional composites made with boron are absorbers of low energy nuetrons, and could be used for structural shielding materials. Polyethylene/boron carbide composites were fabricated using conventional polymer processing techniques, and were evaluated for mechanical and radiation shielding properties. Addition of neat boron carbide (powder and nanoparticles) to an injection molding grade HPDE showed superior mechanical properties compared to neat HDPE. Radiation shielding measurements of a 2 wt% boron carbide composite were improved over those of the neat polyethylene.

Harrison, Courtney; Burgett, Eric; Hertel, Nolan; Grulke, Eric

2008-01-01

322

Polyethylene/Boron Composites for Radiation Shielding Applications  

SciTech Connect

Multifunctional composites made with boron are absorbers of low energy nuetrons, and could be used for structural shielding materials. Polyethylene/boron carbide composites were fabricated using conventional polymer processing techniques, and were evaluated for mechanical and radiation shielding properties. Addition of neat boron carbide (powder and nanoparticles) to an injection molding grade HPDE showed superior mechanical properties compared to neat HDPE. Radiation shielding measurements of a 2 wt% boron carbide composite were improved over those of the neat polyethylene.

Harrison, Courtney; Grulke, Eric [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States); Burgett, Eric; Hertel, Nolan [Neely Nuclear Research Center, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2008-01-21

323

Mechanical properties and stabilities of ?-boron monolayers.  

PubMed

We investigate the mechanical properties and stabilities of planar ?-boron monolayers under various large strains using density functional theory (DFT). ?-Boron has a high in-plane stiffness, about 2/3 of that of graphene, which suggests that ?-boron is four times as strong as iron. Potential profiles and stress-strain curves indicate that a free standing ?-boron monolayer can sustain large tensile strains, up to 0.12, 0.16, and 0.18 for armchair, zigzag, and biaxial deformations, respectively. Third, fourth, and fifth order elastic constants are indispensable for accurate modeling of the mechanical properties under strains larger than 0.02, 0.06, and 0.08 respectively. Second order elastic constants, including in-plane stiffness, are predicted to monotonically increase with pressure, while the trend of Poisson's ratio is reversed. The surface sound speeds of both the compressional and shear waves increase with pressure. The ratio of these two sound speeds increases with the increase of pressure and converges to a value of 2.5. Our results imply that ?-boron monolayers are mechanically stable under various large strains and have advanced mechanical properties - high strength and high flexibility. PMID:25481980

Peng, Qing; Han, Liang; Wen, Xiaodong; Liu, Sheng; Chen, Zhongfang; Lian, Jie; De, Suvranu

2015-01-21

324

Update on human health effects of boron.  

PubMed

In vitro, animal, and human experiments have shown that boron is a bioactive element in nutritional amounts that beneficially affects bone growth and central nervous system function, alleviates arthritic symptoms, facilitates hormone action and is associated with a reduced risk for some types of cancer. The diverse effects of boron suggest that it influences the formation and/or activity of substances that are involved in numerous biochemical processes. Several findings suggest that this influence is through the formation of boroesters in biomolecules containing cis-hydroxyl groups. These biomolecules include those that contain ribose (e.g., S-adenosylmethionine, diadenosine phosphates, and nicotinamide adenine dinucleotide). In addition, boron may form boroester complexes with phosphoinositides, glycoproteins, and glycolipids that affect cell membrane integrity and function. Both animal and human data indicate that an intake of less than 1.0mg/day inhibits the health benefits of boron. Dietary surveys indicate such an intake is not rare. Thus, increasing boron intake by consuming a diet rich in fruits, vegetables, nuts and pulses should be recognized as a reasonable dietary recommendation to enhance health and well-being. PMID:25063690

Nielsen, Forrest H

2014-10-01

325

Effects of boron on nodule development and symbiotic nitrogen fixation in soybean plants  

Microsoft Academic Search

Effects of boron (B) on soybean growth, nodule development, and nitrogen fixation were studied. When soybean plants were grown in B-free medium for 35,40, or 72 d, B deficiency symptoms appeared. Nodules of B-deficient soybeans were damaged and showed low acetylene reduction activities. Soybean seed production was seriously depressed. Production of whole plant, nodules and pods was maximum at concentrations

Masumi Yamagishi; Yukio Yamamoto

1994-01-01

326

Boron Neutron Capture Therapy of a Murine Melanoma1  

Microsoft Academic Search

Boron neutron capture therapy has been carried out on BALB\\/c mice carrying the Harding-Passey melanoma s.c. on the thigh. \\/7-Boronophen- ylalanine (BPA), a boronated analogue of natural melanin precursors, was used to target boron selectively to melanoma. BPA was administered to the mice either via i.p. injection or p.o. by intubation. '\\

Jeffrey A. Coderre; John A. Kalef-Ezra; Ralph G. Fairchild; Peggy L. Micca; Lawrence E. Reinstein; John D. Glass

327

Prediction of Orientational Phase Transition in Boron , W. P. Huhna  

E-print Network

Prediction of Orientational Phase Transition in Boron Carbide M. Widoma, , W. P. Huhna a-268-7645 Abstract The assessed binary phase diagram of boron-carbon exhibits a single intrinsi- cally disordered on carbon content. Keywords: Boron carbide, B4C, B13C2, phase diagram, orientational phase transition

Widom, Michael

328

Comprehensive Analysis of Chemical Bonding in Boron Clusters  

E-print Network

Comprehensive Analysis of Chemical Bonding in Boron Clusters DMITRY YU. ZUBAREV, ALEXANDER I a comprehensive analysis of chemical bonding in pure boron clusters. It is now established in joint experimental and theoretical studies that pure boron clusters are planar or quasi-planar at least up to twenty atoms

Simons, Jack

329

Aspects ol the Estimation ol Physical Properties ol Boron Compounds  

E-print Network

CHAPTER 21 Aspects ol the Estimation ol Physical Properties ol Boron Compounds by the Use ol Species Containing Boron, Hydrogen, and Sometimes Carbon. . . . . . . . . . . . . . . .. 495 3. Estimation ot the Heats ot Vaporization ot Boron-Containing SpecieswithIHetero"-atoms 501 4. Estimation ot

Simons, Jack

330

Boron-containing amino carboxylic acid compounds and uses thereof  

DOEpatents

Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

Kabalka, George W. (Knoxville, TN); Srivastava, Rajiv R. (Knoxville, TN)

2000-03-14

331

Boron nitride substrates for high-quality graphene electronics  

E-print Network

Boron nitride substrates for high-quality graphene electronics C. R. Dean1,2 *, A. F. Young3 , I with a suspended sample. Hexagonal boron nitride (h-BN) is an appealing substrate, because it has an atom- ically, where similar surface effects continue to cause problems16­18 . Hexagonal boron nitride (h-BN) isan

Hone, James

332

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride  

E-print Network

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride Gwan-Hyoung Lee://apl.aip.org/about/rights_and_permissions #12;Electron tunneling through atomically flat and ultrathin hexagonal boron nitride Gwan-Hyoung Lee,1 atomically flat and ultrathin hexagonal boron nitride (h-BN) on gold-coated mica was investigated using

Hone, James

333

Ultrahigh Torsional Stiffness and Strength of Boron Nitride Jonathan Garel,  

E-print Network

Ultrahigh Torsional Stiffness and Strength of Boron Nitride Nanotubes Jonathan Garel, Itai Leven of boron nitride nanotube (BNNT) torsional mechanics. We show that BNNTs exhibit a much stronger mechanical in nanoelectromechanical systems (NEMS), fibers, and nanocomposites. KEYWORDS: Nanotube, boron nitride (BN), atomic force

Hod, Oded

334

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride  

E-print Network

Electron tunneling through atomically flat and ultrathin hexagonal boron nitride Gwan-Hyoung Lee,1 atomically flat and ultrathin hexagonal boron nitride (h-BN) on gold-coated mica was investigated using and long term stability of MOSFETs.5,6 Recently, hexagonal boron nitride (h-BN), which is an iso- morph

Kim, Philip

335

Thermodynamics of yield in boron nitride nanotubes Traian Dumitrica,1  

E-print Network

Thermodynamics of yield in boron nitride nanotubes Traian Dumitrica,1 Holger F. Bettinger,2 investigate the atomistic mechanism of yield to mechanical tension in boron nitride nanotubes. The formation s : 61.48. c, 71.15.Pd I. INTRODUCTION Boron nitride nanotubes BNNT's are a new type of nanoparticles

Dumitrica,Traian

336

Boron neutron capture therapy of malignant brain tumors at the Brookhaven Medical Research Reactor  

SciTech Connect

Boron neutron capture therapy (BNCT) is a bimodal form of radiation therapy for cancer. The first component of this treatment is the preferential localization of the stable isotope {sup 10}B in tumor cells by targeting with boronated compounds. The tumor and surrounding tissue is then irradiated with a neutron beam resulting in thermal neutron/{sup 10}B reactions ({sup 10}B(n,{alpha}){sup 7}Li) resulting in the production of localized high LET radiation from alpha and {sup 7}Li particles. These products of the neutron capture reaction are very damaging to cells, but of short range so that the majority of the ionizing energy released is microscopically confined to the vicinity of the boron-containing compound. In principal it should be possible with BNCT to selectively destroy small nests or even single cancer cells located within normal tissue. It follows that the major improvements in this form of radiation therapy are going to come largely from the development of boron compounds with greater tumor selectivity, although there will certainly be advances made in neutron beam quality as well as the possible development of alternative sources of neutron beams, particularly accelerator-based epithermal neutron beams.

Joel, D.D.; Coderre, J.A.; Chanana, A.D. [Brookhaven National Lab., Upton, NY (United States). Medical Dept.

1996-12-31

337

A small, insertable oven for boronization  

SciTech Connect

A small insertable oven for benchmarking the boronizing characteristics of solid compounds, such as decaborane and carborane, has been developed for the Phaedrus-T tokamak. Assembly and installation of the oven are relatively easy as the oven design utilizes a Langmuir probe drive assembly, which is standard equipment on most tokamaks and allows the oven to be inserted into the tokamak without requiring a vent. Films deposited by heating carborane into the vapor state with the oven are found to be spatially nonuniform in both thickness and in the ratio of boron to carbon as compared to films deposited with trimethylboron, a gaseous compound. Overall plasma performance is not found to be greatly affected by whether decaborane, carborane or trimethylboron is used for boronization in Phaedrus-T. {copyright} {ital 1996 American Institute of Physics.} {lt}ii;010512{gt}

Brouchous, D.A.; Diebold, D.A.; Doczy, M.L. [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin, 1500 Johnson Drive, 337 ERB, Madison, Wisconsin 53706-1687 (United States)] [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin, 1500 Johnson Drive, 337 ERB, Madison, Wisconsin 53706-1687 (United States)

1996-04-01

338

A small, insertable oven for boronization  

NASA Astrophysics Data System (ADS)

A small insertable oven for benchmarking the boronizing characteristics of solid compounds, such as decaborane and carborane, has been developed for the Phaedrus-T tokamak. Assembly and installation of the oven are relatively easy as the oven design utilizes a Langmuir probe drive assembly, which is standard equipment on most tokamaks and allows the oven to be inserted into the tokamak without requiring a vent. Films deposited by heating carborane into the vapor state with the oven are found to be spatially nonuniform in both thickness and in the ratio of boron to carbon as compared to films deposited with trimethylboron, a gaseous compound. Overall plasma performance is not found to be greatly affected by whether decaborane, carborane or trimethylboron is used for boronization in Phaedrus-T.

Brouchous, D. A.; Diebold, D. A.; Doczy, M. L.

1996-04-01

339

Boron alloying of GaN  

NASA Astrophysics Data System (ADS)

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

Escalanti, Laurian; Hart, Gus L. W.

2003-03-01

340

Radioisotope Electric Propulsion (REP): A Near-Term Approach to Nuclear Propulsion  

NASA Technical Reports Server (NTRS)

Studies over the last decade have shown radioisotope-based nuclear electric propulsion to be enhancing and, in some cases, enabling for many potential robotic science missions. Also known as radioisotope electric propulsion (REP), the technology offers the performance advantages of traditional reactor-powered electric propulsion (i.e., high specific impulse propulsion at large distances from the Sun), but with much smaller, affordable spacecraft. Future use of REP requires development of radioisotope power sources with system specific powers well above that of current systems. The US Department of Energy and NASA have developed an advanced Stirling radioisotope generator (ASRG) engineering unit, which was subjected to rigorous flight qualification-level tests in 2008, and began extended lifetime testing later that year. This advancement, along with recent work on small ion thrusters and life extension technology for Hall thrusters, could enable missions using REP sometime during the next decade.

Schmidt, George R.; Manzella, David H.; Kamhawi, Hani; Kremic, Tibor; Oleson, Steven R.; Dankanich, John W.; Dudzinski, Leonard A.

2009-01-01

341

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

342

Cascaded Thermoelectric Converters for Advanced Radioisotope Power Systems  

NASA Astrophysics Data System (ADS)

Three Cascaded Thermoelectric Converters (CTCs) are optimized for potential use in Multi-Mission Advanced Radioisotope Power Systems (MM-ARPS) for electrical powers up to 1 kWe, or even higher, in support of 7-10 year missions. The peak efficiencies of these CTCs of 9.43% to 14.32% are 40% to 110% higher than that of SiGe in State-of-the-Art (SOA) Radioisotope Thermoelectric Generators (RTGs). Such high efficiencies would significantly reduce the amount of 238PuO2 fuel and the total system mass for a lower mission cost. Each CTC is comprised of a SiGe top unicouple that is thermally, but not electrically, coupled to a bottom unicouple with one of the following three choices of thermoelectric materials: (a) p-leg of TAGS-85 and n-leg of 2N-PbTe (b) p-leg of CeFe3.5Co0.5Sb12 and n-leg of CoSb3; and (c) segmented p-leg of CeFe3.5Co0.5Sb12 and Zn4Sb3 and n-leg of CoSb3. The length of the top and bottom unicouples is 10 mm, but the cross-sectional areas of the n- and p-legs of the unicouples are optimized for maximum efficiency operation. They vary with the thermal power inputs of 1, 2, and 3 Wth per SiGe unicouple, and the heat rejection temperature of 375 K, 475 K, and 575 K, from the bottom unicouple. Such geometrical optimization is at nominal hot shoe temperature of 1273 K for the SiGe unicouple and cold shoe temperature of either 780 K or 980 K, depending on the materials of the bottom unicouples. The hot shoe temperature of the bottom unicouples is 20 K lower than the cold shoe of the top SiGe unicouple, but the rate of heat input is the same as the rate of heat rejection from the top unicouple. The present results are conservative as they assume a contact resistance of 150 ??-cm2 per leg for the top and the bottom unicouples in the CTCs; however, decreasing this resistance to 50 ??-cm2 per leg could increase the current efficiency estimates by an additional 1 - 2 percentage points.

El-Genk, Mohamed S.; Saber, Hamed H.

2004-02-01

343

Radioisotope electric propulsion (REP): A near-term approach to nuclear propulsion  

Microsoft Academic Search

Studies over the last decade have shown radioisotope-based nuclear electric propulsion to be enhancing and, in some cases, enabling for many potential robotic science missions. Also known as radioisotope electric propulsion (REP), the technology offers the performance advantages of traditional reactor-powered electric propulsion (i.e., high specific impulse propulsion at large distances from the Sun), but with much smaller, affordable spacecraft.

George R. Schmidt; David H. Manzella; Hani Kamhawi; Tibor Kremic; Steven R. Oleson; John W. Dankanich; Leonard A. Dudzinski

2010-01-01

344

Ultrahard nanotwinned cubic boron nitride.  

PubMed

Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ?14?nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ?3.8?nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100?GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (?1,294?°C) and a large fracture toughness (>12?MPa?m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ?10?MPa?m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ?10-15?nm found in metals and alloys. PMID:23325219

Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan

2013-01-17

345

Boron nitride nanotubes for spintronics.  

PubMed

With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics. PMID:25248070

Dhungana, Kamal B; Pati, Ranjit

2014-01-01

346

Lithium-Beryllium-Boron and Oxygen in the early Galaxy  

E-print Network

Oxygen is a much better evolutionary index than iron to follow the history of Lithium-Beryllium-Boron (LiBeB) since it is the main producer of these light elements at least in the early Galaxy. The O-Fe relation is crucial to the determination of the exact physical process responsible for the LiBeB production. Calculated nucleosynthetic yields of massive stars, estimates of the energy cost of Be production, and above all recent observations reported in this meeting seem to favor a mechanism in which fast nuclei enriched into He, C and O arising from supernovae are accelerated in superbubbles and fragment on H and He in the interstellar medium.

Elisabeth Vangioni-Flam; Michel Casse

2000-11-24

347

Hot filament cvd of boron nitride films  

SciTech Connect

This patent describes a method for coating a substrate with a boron nitride film. It comprises: providing a substrate and a hot filament in a gas chamber; and introducing a borazine gas into the gas chamber so as to heat the borazine gas with the hot filament and deposit the boron nitride film on the substrate, wherein the hot filament is heated to a temperature of from about 1000[degrees] to 1800[degrees] C and the substrate is maintained at a temperature of from 100[degrees]C to 400[degrees]C.

Rye, R.R.

1992-01-07

348

Titanium reinforced boron-polyimide composite  

NASA Technical Reports Server (NTRS)

Processing techniques for boron polyimide prepreg were developed whereby composites could be molded under vacuum bag pressure only. A post-cure cycle was developed which resulted in no loss in room temperature mechanical properties of the composite at any time during up to 16 hours at 650 F. A design utilizing laminated titanium foil was developed to achieve a smooth transition of load from the titanium attachment points into the boron-reinforced body of the structure. The box beam test article was subjected to combined bending and torsional loads while exposed to 650 F. Loads were applied incrementally until failure occurred at 83% design limit load.

Clark, G. A.; Clayton, K. I.

1969-01-01

349

Boron aluminum crippling strength shows improvement  

NASA Technical Reports Server (NTRS)

Results are presented from an experimental program directed toward improving boron aluminum crippling strength. Laminate changes evaluated were larger filament diameter, improved processing, shape changes, adding steel-aluminum cross plies, reduced filament volume in corners, adding boron aluminum angle plies, and using titanium interleaves. Filament diameter and steel-aluminum cross plies have little effect on crippling. It is shown that better processing combined with appropriate shape changes improved crippling over 50 percent at both room temperature and 600 F. Tests also show that crippling improvements ranging from 20 to 40 percent are achieved using angle plies and titanium interleaves.

Otto, O. R.; Bohlmann, R. E.

1974-01-01

350

Boron Nitrides — Properties, Synthesis and Applications  

Microsoft Academic Search

\\u000a Boron nitride is a extraordinary topic in the area of materials science. Due to the special bonding behaviors of boron and\\u000a nitrogen the BN exists in many different structures. The well-defined crystallographic structures are hexagonal BN (h-BN),\\u000a rhombohedral BN (r-BN), wurtzitic BN (w-BN), and cubic BN (c-BN). Additionally, other crystalline and amorphous structures\\u000a exist. Exceptional is that there are still

R. Haubner; M. Wilhelm; R. Weissenbacher; B. Lux

2002-01-01

351

Picosecond laser structuration under high pressures: observation of boron nitride nanorods  

E-print Network

We report on picosecond UV-laser processing of hexagonal boron nitride (hBN) at moderately high pressures above 500 bar. The main effect is specific to the ambient gas and laser pulse duration in the ablation regime: when samples are irradiated by 5 ps or 0.45 ps laser pulses in nitrogen gas environment, multiple nucleation of a new crystalline product - BN nanorods - takes place. This process is triggered on structural defects, which number density strongly decreases upon recrystallization. Non-linear photon absorption by adsorbed nitrogen molecules is suggested to mediate the nucleation-growth. High pressure is responsible for the confinement and strong backscattering of ablation products. A strong surface structuring also appears at longer 150-ps laser irradiation in similar experimental conditions. However, the transformed product in this case is amorphous strongly contaminated by boron suboxides BxOy.

Museur, Luc; Michel, Jean Pierre; Marine, Wladimir; Anglos, Demetrios; Fotakis, Costa; Kanaev, Andrei; 10.1063/1.3000457

2008-01-01

352

Boron Doping Carbon Structures Using Decaborane? A Theoretical Study  

NASA Astrophysics Data System (ADS)

Boron-doped carbon materials have been shown to improve hydrogen storage. Boron-doped activated carbons have been produced using a novel process involving the pyrolysis of a boron containing compound and subsequent high-temperature annealing. A model for the boron doping process based on a Langmuir isotherm is presented. A theoretical study of the interaction of the boron containing compound with the undoped carbon precursor will be presented. Ab-initio calculations of the potential energy surface and the Langmuir isotherm parameters derived from them are also presented. The theoretical study outlines the unique capabilities and limits of this doping procedure.

Wexler, Carlos; Connolly, Matthew; Beckner, Matthew; Pfeifer, Peter

2012-02-01

353

Optical characteristic analysis of the boronization process by using carborane  

NASA Astrophysics Data System (ADS)

Boronization with carborane (C2B10H12) was archieved in a vacuum vessel coupled to a filament discharge system. Optical emission spectroscopy was employed to characterize the boronization process. The Balmer lines of hydrogen and deuterium were measured, and the boronization process was analyzed by using the intensity ratio of the H ? to the D ? line (IH/ID). The relation between the pressure and the intensity ratio was investigated, and the thickness of the deposited boron film was predicted. Also, the dilution ratio H/(H + D) of the boron film was analyzed and compared with the one predicted from an optical analysis of the emission spectrum.

Lee, Wonwook; Park, Kyungdeuk; Choi, Young-sun; Oh, Cha-Hwan

2014-09-01

354

Electrochemical oxidation of benzene on boron-doped diamond electrodes.  

PubMed

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H2SO4 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1x10(-2) M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10(-5) M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound. PMID:17126378

Oliveira, Robson T S; Salazar-Banda, Giancarlo R; Santos, Mauro C; Calegaro, Marcelo L; Miwa, Douglas W; Machado, Sergio A S; Avaca, Luis A

2007-02-01

355

Boron-containing organic pigments from a Jurassic red alga  

PubMed Central

Organic biomolecules that have retained their basic chemical structures over geological periods (molecular fossils) occur in a wide range of geological samples and provide valuable paleobiological, paleoenvironmental, and geochemical information not attainable from other sources. In rare cases, such compounds are even preserved with their specific functional groups and still occur within the organisms that produced them, providing direct information on the biochemical inventory of extinct organisms and their possible evolutionary relationships. Here we report the discovery of an exceptional group of boron-containing compounds, the borolithochromes, causing the distinct pink coloration of well-preserved specimens of the Jurassic red alga Solenopora jurassica. The borolithochromes are characterized as complicated spiroborates (boric acid esters) with two phenolic moieties as boron ligands, representing a unique class of fossil organic pigments. The chiroptical properties of the pigments unequivocally demonstrate a biogenic origin, at least of their ligands. However, although the borolithochromes originated from a fossil red alga, no analogy with hitherto known present-day red algal pigments was found. The occurrence of the borolithochromes or their possible diagenetic products in the fossil record may provide additional information on the classification and phylogeny of fossil calcareous algae. PMID:20974956

Wolkenstein, Klaus; Gross, Jürgen H.; Falk, Heinz

2010-01-01

356

The abundance of boron in diffuse interstellar clouds  

NASA Astrophysics Data System (ADS)

The origins of the stable isotopes of boron remain uncertain despite much theoretical and observational effort. Spallation reactions between relativistic Galactic cosmic rays (GCR) and interstellar nuclei can adequately account for the production of 10 B and contribute to the cosmic abundance of 11 B. However, an additional source of 11 B synthesis is required to raise the isotopic ratio of 11 B/ 10 B from its GCR spallation value (2.4) to the value measured in carbonaceous chondrites (4.0). The n-process, neutrino-induced spallation in Type II supernovae, is a potentially significant source of 11 B production. Since neutrino-induced spallation does not result in substantial yields for 10 B, this process could naturally explain the enhancement in 11 B/ 10 B over the predictions of standard GCR spallation. Without the n-process, enhanced 11 B production, relative to 10 B, could be attributed to an increased flux of low- energy (5-40 MeV nucleon -1 ) cosmic rays, which are unobservable from Earth due to magnetic shielding by the solar wind. In this thesis, I present a comprehensive survey of boron abundances in diffuse interstellar clouds from Space Telescope Imaging Spectrograph (STIS) observations made with the Hubble Space Telescope in an effort to identify the sources responsible for light element nucleosynthesis. The present sample of 56 Galactic sight lines is the result of a complete search of archival STIS data for the B II l1362 resonance line. Each detection is confirmed by the presence of absorption due to O I l1355, Cu II l1358, and Ga II l1414 (when available) at the same velocity. Like B + , these species represent the dominant ionization stage of their element in neutral diffuse clouds and therefore should coexist. Profile templates based on synthesized absorption profiles of O I, Cu II, and Ga II are fitted to the B II line, yielding the total boron column density along each line of sight. By synthesizing B II profiles with components seen in high-resolution ground-based observations of Ca II l3933 and K I l7698, I show that unresolved structure in the UV data has little influence on final boron abundances. Many sight lines exhibit multiple complexes of absorption components well separated in velocity. I interpret such sight lines as tracing both local gas, with velocity components near 0 km s -1 relative to the local standard of rest (LSR), and gas associated with a distant spiral arm, with components at more negative velocities. In these cases, profile templates are created for each complex and fitted to that portion of the B II profile independently, thereby enabling a comparative analysis of boron abundances in distinct physical regions within the Galaxy. With this procedure, I find suggestive evidence for a higher B/O ratio in the inner Sagittarius-Carina spiral arm than in the vicinity of the Sun. Abundances of secondary elements increase relative to those of primary elements toward the Galactic center due to enhanced rates of star formation and stellar nucleosynthesis. The finding that the B/O ratio is elevated toward the inner Galaxy may thus indicate the secondary nature of boron, which in turn would cast doubt on the efficiency of the n-process, a primary production mechanism. Measured line-of-sight abundance ratios of B/H and B/O firmly establish that boron is depleted (relative to the Sun) in diffuse gas. A comparison of these ratios with measures of gas density, namely the average line-of-sight hydrogen density [left angle bracket] n H [right angle bracket] and the fraction of hydrogen in molecular form f (H 2 ), further demonstrates that the depletion increases in high-density sight lines, a trend seen in the abundances of many other elements, including in the oxygen, copper, and gallium results presented here. Elemental depletion onto interstellar dust grains increases with average gas density due to the larger fraction of cold clouds, relative to warm gas, along the line of sight. In the case of boron, this amounts to an abundance difference of 0.8 dex between the warm and cold phases of the

Ritchey, Adam M.

357

Kinetics of radioisotope exchange between brine and rock in a geothermal system  

SciTech Connect

A wide range of isotopes in the /sup 238/U, /sup 235/U, and /sup 232/Th decay chains was measured in geothermal brines collected from two production zones at 1898 and 3220 m in the Salton Sea Scientific Drilling Project well. High concentrations of radium, radon, and lead isotopes are generated and maintained by the input of these isotopes from solid phases into brine by both recoil and leaching processes, by the high chloride content of the brine which complexes radium and lead, and by the apparent absence of suitable unoccupied adsorption sites. In contrast, uranium, thorium, actinium, bismuth, and polonium isotopes all have low concentrations due to their efficient sorption from brine to rock. Measurements of short-lived isotopes in these decay series yield insights regarding the mechanisms controlling radioisotope exchange, and they permit estimation of rates of brine-rock interaction. For example, the /sup 228/Ac//sup 228/Ra activity ratio of 0.2 in brines indicates that the mean residence time of actinium in solution before sorption onto solid surfaces is less than 2.5 hours.

Hammond, D.E.; Zukin, J.G.; Teh-Lung Ku

1988-11-10

358

"Stereo Compton cameras" for the 3-D localization of radioisotopes  

NASA Astrophysics Data System (ADS)

The Compton camera is a viable and convenient tool used to visualize the distribution of radioactive isotopes that emit gamma rays. After the nuclear disaster in Fukushima in 2011, there is a particularly urgent need to develop "gamma cameras", which can visualize the distribution of such radioisotopes. In response, we propose a portable Compton camera, which comprises 3-D position-sensitive GAGG scintillators coupled with thin monolithic MPPC arrays. The pulse-height ratio of two MPPC-arrays allocated at both ends of the scintillator block determines the depth of interaction (DOI), which dramatically improves the position resolution of the scintillation detectors. We report on the detailed optimization of the detector design, based on Geant4 simulation. The results indicate that detection efficiency reaches up to 0.54%, or more than 10 times that of other cameras being tested in Fukushima, along with a moderate angular resolution of 8.1° (FWHM). By applying the triangular surveying method, we also propose a new concept for the stereo measurement of gamma rays by using two Compton cameras, thus enabling the 3-D positional measurement of radioactive isotopes for the first time. From one point source simulation data, we ensured that the source position and the distance to the same could be determined typically to within 2 meters' accuracy and we also confirmed that more than two sources are clearly separated by the event selection from two point sources of simulation data.

Takeuchi, K.; Kataoka, J.; Nishiyama, T.; Fujita, T.; Kishimoto, A.; Ohsuka, S.; Nakamura, S.; Adachi, S.; Hirayanagi, M.; Uchiyama, T.; Ishikawa, Y.; Kato, T.

2014-11-01

359

Accelerator mass spectrometry for measurement of long-lived radioisotopes  

SciTech Connect

Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes /sup 10/Be, /sup 14/C, /sup 26/Al, /sup 36/Cl, and /sup 129/I can now be measured in small natural samples having isotopic abundances in the range 10/sup -12/ to 10/sup -15/ and as few as 10/sup 5/ atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archaeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of half-lives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences. 98 references, 4 figures, 2 tables.

Elmore, D.; Phillips, F.M.

1987-05-01

360

Assessment of dynamic energy conversion systems for radioisotope heat sources  

SciTech Connect

The use of dynamic conversion systems to convert the heat generated in a 7500 W(t) 90 Sr radioisotopic heat source to electricity is examined. The systems studies were Stirling; Brayton Cycle; three organic Rankines (ORCs) (Barber-Nichols/ORMAT, Sundstrand, and TRW); and an organic Rankine plus thermoelectrics. The systems were ranked for a North Warning System mission using a Los Alamos Multiattribute Decision Theory code. Three different heat source designs were used: case I with a beginning of life (BOL) source temperature of 640 C, case II with a BOL source temperature of 745/sup 0/C, and case III with a BOL source temperature of 945/sup 0/C. The Stirling engine system was the top-ranked system of cases I and II, closely followed by the ORC systems in case I and ORC plus thermoelectrics in case II. The Brayton cycle system was top-ranked for case III, with the Stirling engine system a close second. The use of /sup 238/Pu in heat source sizes of 7500 W(t) was examined and found to be questionable because of cost and material availability and because of additional requirements for analysis of safeguards and critical mass.

Thayer, G.R.; Mangeng, C.A.

1985-06-01

361

Accelerator mass spectrometry for measurement of long-lived radioisotopes.  

PubMed

Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes (10)Be, (14)C,(26)A1, 36Cl, and (129)1 can now be measured in small natural samples having isotopic abundances in the range 10(-12) to 10(- 5) and as few as 10(5) atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of halflives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences. PMID:17740475

Elmore, D; Phillips, F M

1987-05-01

362

Neptune Orbiters Utilizing Solar and Radioisotope Electric Propulsion  

NASA Technical Reports Server (NTRS)

In certain cases, Radioisotope Electric Propulsion (REP), used in conjunction with other propulsion systems, could be used to reduce the trip times for outer planetary orbiter spacecraft. It also has the potential to improve the maneuverability and power capabilities of the spacecraft when the target body is reached as compared with non-electric propulsion spacecraft. Current missions under study baseline aerocapture systems to capture into a science orbit after a Solar Electric Propulsion (SEP) stage is jettisoned. Other options under study would use all REP transfers with small payloads. Compared to the SEP stage/Aerocapture scenario, adding REP to the science spacecraft as well as a chemical capture system can replace the aerocapture system but with a trip time penalty. Eliminating both the SEP stage and the aerocapture system and utilizing a slightly larger launch vehicle, Star 48 upper stage, and a combined REP/Chemical capture system, the trip time can nearly be matched while providing over a kilowatt of science power reused from the REP maneuver. A Neptune Orbiter mission is examined utilizing single propulsion systems and combinations of SEP, REP, and chemical systems to compare concepts.

Fiehler, Douglas I.; Oleson, Steven R.

2004-01-01

363

Thermal vacuum life test facility for radioisotope thermoelectric generators  

NASA Astrophysics Data System (ADS)

In the late 1970's, the Department of Energy (DOE) assigned Monsanto Research Corporation, Mound Facility, now operated by EG and G Mound Applied Technologies, the responsibility for assembling and testing General Purpose Heat Source (GPHS) radioisotope thermoelectric generators (RTGs). Assembled and tested were five RTGs, which included four flight units and one non-flight qualification unit. Figure 1 shows the RTG, which was designed by General Electric AstroSpace Division (GE/ASD) to produce 285 W of electrical power. A detailed description of the processes for RTG assembly and testing is presented by Amos and Goebel (1989). The RTG performance data are described by Bennett, et al., (1986). The flight units will provide electrical power for the National Aeronautics and Space Administration's (NASA) Galileo mission to Jupiter (two RTGs) and the joint NASA/European Space Agency (ESA) Ulysses mission to study the polar regions of the sun (one RTG). The remaining flight unit will serve as the spare for both missions, and a non-flight qualification unit was assembled and tested to ensure that performance criteria were adequately met.

Deaton, R. L.; Goebel, C. J.; Amos, W. R.

364

Wall Temperature Dependence of Boronization Using Decaborane and Diborane  

NASA Astrophysics Data System (ADS)

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

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

1993-09-01

365

Hierarchical supramolecules and organization using boronic acid building blocks.  

PubMed

Current progress on hierarchical supramolecules using boronic acids has been highlighted in this feature article. Boronic acids can participate in "click reactions" with diols and their congeners with dynamic covalent functionality. By comprehensively exploring versatile sequential boronate esterification linkages between plural boronic acid-appended molecules and multiple hydroxyl counterparts, not only versatile supramolecular polymers but also structurally well-defined network nanostructures have been developed. In addition orthogonal interactions such as dative bonds of the boron center with Lewis bases have led to the formation of hierarchical nano/microstructures. Boronate systems have the potential to be used as materials for smart gels, chemosensors, active architectures for electronics, heterogeneous catalysts, chemical-stimulus responsive systems for drug delivery, etc. Here, we fully discuss the feasibility of the structure-directing ability of boronic acids from the standpoint of the generation of new smart materials. PMID:25465854

Kubo, Yuji; Nishiyabu, Ryuhei; James, Tony D

2015-01-22

366

The Effect of Boronizing on Metallic Alloys for Automotive Applications  

NASA Astrophysics Data System (ADS)

In this study the wear resistance, corrosion resistance, and oxidation resistance of boronized metallic alloys were investigated. Thermochemical treatment was performed by powder pack boronizing process at temperature 850-950 °C for 4 h. Saw-tooth morphology and smooth interface microstructures were observed with an optical microscope; microhardness was measured across the coating depth. The phases present in the boron coatings depend on the substrate material. High-temperature oxidation resistance was investigated and it was found that boron coating on ferrous alloys can resist temperatures up to 800 °C. The corrosion resistance of the boronized samples was improved and the corrosion rate was calculated for boronized and plain specimens. Wear testing was conducted by following the procedures of ASTM G99, ASTM D2526, and ASTM D4060. The obtained experimental results revealed that boronizing significantly improves the wear-resistance, corrosion-resistance, and oxidation resistance of metallic alloys.

Petrova, Roumiana S.; Suwattananont, Naruemon; Samardzic, Veljko

2008-06-01

367

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

Microsoft Academic Search

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

Danny C. Halverson; Aleksander J. Pyzik; Ilhan A. Aksay

1986-01-01

368

Phase and property studies of boron carbide-boron nitride composites  

Microsoft Academic Search

This paper reports on boron carbide-boron nitride particulate composites that were fabricated by vacuum hot-pressing. Near-theoretical densities of BâC were obtained, but percent theoretical densities decreased with increasing amounts of BN. The grain size of BâC and BN was not affected by composition, but the amount of twinning in BâC decreased with increasing BN content. No third phase was found

Robert Ruh; M. Kerns; Avigdor Zangvil; Youren Xu

1992-01-01

369

Boron isotope geochemistry as a tracer for the evolution of brines and associated hot springs from the Dead Sea, Israel  

NASA Astrophysics Data System (ADS)

A boron isotope study combined with analyses of elemental boron, lithium, and chlorine is used to suggest that brines from the Dead Sea and on-shore hypersaline thermal springs (Hamme Yesha, Hamme Zohar, and Hamme Mazor) are the products of interaction of evaporated seawater with detrital sediments. The high ?11B values of the Dead Sea brines (55.7 to 57.4%. versus NBS-951) and the hot springs (52.2 to 55.7%.), and low B/Li ratios (2.0 to 2.3 and 2.5 to 2.7, respectively), relative to seawater, indicate preferential removal of 10B from the brines and hence boron adsorption onto clay minerals. The brackish 'En Feshcha springs and the freshwater 'En Dawid and Nahal Arugot springs yield lower B contents and ?11B values (37.7 to 40.6%. and 33.8 to 36.9%., respectively). The ?11B values and B contents of diluted Dead Sea brines lie on calculated mixing lines between the composition of the brackish and freshwater springs with the composition of the Dead Sea. The ?11 B values of the hot springs, however, given their boron content, are significantly lower than those of the mixing lines. Thus, waters from the hot springs cannot be a mixing product of the Dead Sea brine with freshwater. Instead, the Dead Sea brine has evolved from the brines of the hot springs through further isotopic fractionation and boron adsorption onto detrital sediments.

Vengosh, Avner; Starinsky, Abraham; Kolodny, Yehoshua; Chivas, Allan R.

1991-06-01

370

Y:X sperm ratio in boron-exposed men.  

PubMed

Several epidemiologic investigations have shown shifts in sex ratios at birth toward females in populations with relatively high boron exposure. To investigate the paternal origin of these shifts, we assayed sperm Y:X ratio in men exposed to a range of environmental and workplace boron. Participants included 63 workers in boron industry: 39 men living in an area of high environmental boron but not employed in boron industry, and 44 controls living in an area of low environmental boron. Total daily boron exposure was calculated as the sum of boron in 24-hour duplicate food and fluid intakes plus personal air sampling for workplace inhalable dust. Internal dose was measured in blood, urine, and semen. Sperm were analyzed by fluorescence in situ hybridization for Y- versus X-bearing cells. Potential confounders were identified using a questionnaire. Total exposure was correlated with internal dose (Pearson correlation for total exposure and boron in blood = 0.63, P < .0001; semen = 0.80, P < .001; and urine = 0.79, P < .0001). Linear regression of logged boron in biologic fluids on Y:X ratio was significant for blood P = .02, semen P = .0003, and urine P = .005. Additionally, when subjects were categorized by exposure group, decreased Y:X sperm ratio was found for boron workers compared with men in a high boron environment and controls (P < .0001). Exogenous environmental or workplace boron exposures were associated with decreases in Y- versus X-bearing sperm. This may explain earlier findings from us and others showing changes in offspring sex ratios at birth for men exposed to boron. PMID:17881766

Robbins, Wendie A; Wei, Fusheng; Elashoff, David A; Wu, Guoping; Xun, Lin; Jia, Juan

2008-01-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

372

Intrinsic ferromagnetism in hexagonal boron nitride nanosheets.  

PubMed

Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized ? states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices. PMID:24880305

Si, M S; Gao, Daqiang; Yang, Dezheng; Peng, Yong; Zhang, Z Y; Xue, Desheng; Liu, Yushen; Deng, Xiaohui; Zhang, G P

2014-05-28

373

BORON AND MOLYBDENUM CONTENT IN INFANT FORMULAS  

Technology Transfer Automated Retrieval System (TEKTRAN)

There is new evidence that the content of boron (B) (Hunt, 2004) and molybdenum (Mo) (Friel, 1999) in human milk (HM) may be regulated homeostatically. Presently, the B and Mo content of infant formulas (F) is not standardized by either statute or manufacturing practice. Our analysis of 5 representa...

374

Implantation characteristics by boron cluster ion implantation  

NASA Astrophysics Data System (ADS)

Recently, boron cluster implantation (i.e. decaborane: B10Hx+) is regarded as a promising technology for the formation of P-type Ultra Shallow Junction (USJ) because of the equivalent high beam current with less beam divergence compared to the conventional B+ or BF2+ implantation. Also as-implanted and after-annealing characteristics are different due to the appearance of self-amorphized layer by the cluster ion bombardment, which suppresses the channeling and enhances the boron activation. However, it is anticipated that the properties caused by this amorphous layer will vary with different implantation conditions or a presence of Pre Amorphization Implantation (PAI) process, which should be understood well to maintain a good process control. From this point of view, we have measured the decaborane implantation characteristics by a couple of different related conditions, for instance, the beam energy and current. Sheet resistance vs junction depth (Rs-Xj) are also evaluated in different annealing methods with combination of PAI processes. In addition, a brief comparison is made by implanting the different boron cluster ions (i.e. B8Hx+) by mass selecting the ions extracted from decaborane ionization chamber. In this paper, these characteristics of boron cluster implantations are reviewed.

Nagayama, Tsutomu; Hamamoto, Nariaki; Umisedo, Sei; Tanjyo, Masayasu; Aoyama, Takayuki

2006-11-01

375

Axial residual stresses in boron fibers  

NASA Technical Reports Server (NTRS)

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

Behrendt, D. R.

1978-01-01

376

BORON, MANGANESE, MOLYBDENUM, AND OTHER TRACE ELEMENTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The nutritional importance of each of the mineral elements reviewed in this chapter is considered limited, unclear, or speculative. Three elements can be considered essential for higher animals and humans. These elements are manganese and molybdenum, which are known enzyme cofactors, and boron, whos...

377

Boron nitride as a lubricant additive  

Microsoft Academic Search

Hexagonal boron nitride (BN) has a graphite-like lamellar structure, but has been considered less effective than other solid lubricants except for high-temperature applications. The present paper describes a series of sliding experiments which show somewhat curious behavior of BN when added to lubricating oil, and discusses their results by comparing with the results of observation and analysis of sliding surfaces.

Yoshitsugu Kimura; Toshiaki Wakabayashi; Kazumi Okada; Tetsuya Wada; Hiroshi Nishikawa

1999-01-01

378

Intrinsic ferromagnetism in hexagonal boron nitride nanosheets  

SciTech Connect

Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized ? states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

Si, M. S.; Gao, Daqiang, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn; Yang, Dezheng; Peng, Yong; Zhang, Z. Y.; Xue, Desheng, E-mail: gaodq@lzu.edu.cn, E-mail: xueds@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Liu, Yushen [Jiangsu Laboratory of Advanced Functional Materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500 (China); Deng, Xiaohui [Department of Physics and Electronic Information Science, Hengyang Normal University, Hengyang 421008 (China); Zhang, G. P. [Department of Physics, Indiana State University, Terre Haute, Indiana 47809 (United States)

2014-05-28

379

Impurity control by boronization and optimization of the wall temperature in JT-60U  

NASA Astrophysics Data System (ADS)

In JT-60U, boronization using deuterated decaborane has been applied to suppress oxygen production. Boronization decreased the oxygen content in the core plasma from ~ 3% to ~ 0.5%. The oxygen content of ~ 0.5% was kept by additional boronization about every 100 shots. By lowering the vessel temperature from 540 K to 420 K, chemical sputtering yield decreased by ~ 40% at the carbon divertor plates. For hydrogen plasmas, the carbon content reduced from 3.1% to 1.8% in L-mode discharges with NB heating power of 13 MW ,and from 2.4% to 1.7% in reversed shear discharges. For deuterium plasmas, however, the carbon content did not depend on the vessel temperature. The different dependence of the carbon content on the vessel temperature is considered to be due to isotopic difference between chemical and physical sputtering yield. The effects of boronization and the vessel temperature will be discussed based on correlation between impurity content and impurity influx from the divertor plates and the first walls.

Nakano, T.; Higashijima, S.; Kubo, H.; Sugie, T.; Asakura, N.; Takenaga, H.; Itami, K.

2001-10-01

380

A technique to measure heats of reaction of titanium-boron, aluminim-titanium-boron, and aluminum-titanium-boron-carbon powder blends  

NASA Astrophysics Data System (ADS)

In this research, a modification to initiation aid ignition in bomb calorimetry that involves systemically blending levels of boron and potassium nitrate initiation aids with a bulk structural energetic elemental power blend is developed. A regression is used to estimate the nominal heat of reaction for the primary reaction. The technique is first applied to the synthesis of TiB 2 as a validation study to see if close proximity to literature values can be achieved. The technique is then applied to two systems of interest, Al-Ti-B, and Al-Ti-B4C. In all three investigations, x-ray diffraction is used to characterize the product phases of the reactions to determine the extent and identity of the product phases and any by-products that may have formed as a result of adding the initiation aid. The experimental data indicates the technique approximates the heat of reaction value for the synthesis of TiB2 from Ti-B powder blends and the formation of TiB2 is supported by volume fraction analysis by x-ray diffraction. Application to the Al-Ti-B and Al-Ti-B4C blends show some correlation with variation of the initiation aid, with x-ray diffraction showing the formation of equilibrium products. However, these blends require further investigation to resolve more complex interactions and rule out extraneous variables.

Baker, Andrew H.

381

Radioisotope Power System Delivery, Ground Support and Nuclear Safety Implementation: Use of the Multi-Mission Radioisotope Thermoelectric Generator for the NASA's Mars Science Laboratory  

SciTech Connect

Radioisotope power systems have been used for over 50 years to enable missions in remote or hostile environments. They are a convenient means of supplying a few milliwatts up to a few hundred watts of useable, long-term electrical power. With regard to use of a radioisotope power system, the transportation, ground support and implementation of nuclear safety protocols in the field is a complex process that requires clear identification of needed technical and regulatory requirements. The appropriate care must be taken to provide high quality treatment of the item to be moved so it arrives in a condition to fulfill its missions in space. Similarly it must be transported and managed in a manner compliant with requirements for shipment and handling of special nuclear material. This presentation describes transportation, ground support operations and implementation of nuclear safety and security protocols for a radioisotope power system using recent experience involving the Multi-Mission Radioisotope Thermoelectric Generator for National Aeronautics and Space Administration’s Mars Science Laboratory, which launched in November of 2011.

S.G. Johnson; K.L. Lively; C.C. Dwight

2014-07-01

382

Boron carbide nanowires: Synthesis and characterization  

NASA Astrophysics Data System (ADS)

Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a solid orthorhombic phase catalyst. The status of a catalyst depends mainly on temperature. (3) Observation of "invisible" defects in boron carbide nanowires. The planar defects can only be seen under a transmission electron microscope when the electron beam is within the defect plane. Furthermore, there are only two directions within that plane, along which the orientation of defect can be told and clear TEM results can be taken. The challenge is that the TEM sample holder is limited to tilt +/-30° in each direction. A theory was developed based on lattice calculation and simulation to tell the orientation of defect even not from those unique directions. Furthermore, it was tested by experimental data and proved to be successful. (4) Preliminary exploration of structure-transport property of as-synthesized boron carbide nanowires. In collaboration with experts in the field of thermal science, thermal transport properties of a few boron carbide nanowires were studied. All measured nanowires were either pre-characterized or post-characterized by TEM to reveal their structural information such as diameter, fault orientations and chemical composition. The obtained structural information was then analyzed together with measured thermal conductivity to establish a structure-transport property relation. Current data indicate that TF ones have a lower thermal conductivity, which is also diameter-dependent.

Guan, Zhe

383

Thermal Model Predictions of Advanced Stirling Radioisotope Generator Performance  

NASA Technical Reports Server (NTRS)

This paper presents recent thermal model results of the Advanced Stirling Radioisotope Generator (ASRG). The three-dimensional (3D) ASRG thermal power model was built using the Thermal Desktop(trademark) thermal analyzer. The model was correlated with ASRG engineering unit test data and ASRG flight unit predictions from Lockheed Martin's (LM's) I-deas(trademark) TMG thermal model. The auxiliary cooling system (ACS) of the ASRG is also included in the ASRG thermal model. The ACS is designed to remove waste heat from the ASRG so that it can be used to heat spacecraft components. The performance of the ACS is reported under nominal conditions and during a Venus flyby scenario. The results for the nominal case are validated with data from Lockheed Martin. Transient thermal analysis results of ASRG for a Venus flyby with a representative trajectory are also presented. In addition, model results of an ASRG mounted on a Cassini-like spacecraft with a sunshade are presented to show a way to mitigate the high temperatures of a Venus flyby. It was predicted that the sunshade can lower the temperature of the ASRG alternator by 20 C for the representative Venus flyby trajectory. The 3D model also was modified to predict generator performance after a single Advanced Stirling Convertor failure. The geometry of the Microtherm HT insulation block on the outboard side was modified to match deformation and shrinkage observed during testing of a prototypic ASRG test fixture by LM. Test conditions and test data were used to correlate the model by adjusting the thermal conductivity of the deformed insulation to match the post-heat-dump steady state temperatures. Results for these conditions showed that the performance of the still-functioning inboard ACS was unaffected.

Wang, Xiao-Yen J.; Fabanich, William Anthony; Schmitz, Paul C.

2014-01-01

384

RADIOISOTOPE POWER SYSTEM CAPABILITIES AT THE IDAHO NATIONAL LABORATORY (INL)  

SciTech Connect

--Idaho National Laboratory’s, Space Nuclear Systems and Technology Division established the resources, equipment and facilities required to provide nuclear-fueled, Radioisotope Power Systems (RPS) to Department of Energy (DOE) Customers. RPSs are designed to convert the heat generated by decay of iridium clad, 238PuO2 fuel pellets into electricity that is used to power missions in remote, harsh environments. Utilization of nuclear fuel requires adherence to governing regulations and the INL provides unique capabilities to safely fuel, test, store, transport and integrate RPSs to supply power—supporting mission needs. Nuclear capabilities encompass RPS fueling, testing, handling, storing, transporting RPS nationally, and space vehicle integration. Activities are performed at the INL and in remote locations such as John F. Kennedy Space Center and Cape Canaveral Air Station to support space missions. This paper will focus on the facility and equipment capabilities primarily offered at the INL, Material and Fuel Complex located in a security-protected, federally owned, industrial area on the remote desert site west of Idaho Falls, ID. Nuclear and non-nuclear facilities house equipment needed to perform required activities such as general purpose heat source (GPHS) module pre-assembly and module assembly using nuclear fuel; RPS receipt and baseline electrical testing, fueling, vibration testing to simulate the launch environment, mass properties testing to measure the mass and compute the moment of inertia, electro-magnetic characterizing to determine potential consequences to the operation of vehicle or scientific instrumentation, and thermal vacuum testing to verify RPS power performance in the vacuum and cold temperatures of space.

Kelly Lively; Stephen Johnson; Eric Clarke

2014-07-01

385

Investigations on boron levels in drinking water sources in China.  

PubMed

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

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

2010-06-01

386

Microstructural characterization of superalloy 718 with boron and phosphorus additions  

SciTech Connect

Boron and phosphorus additions are known to improve the stress rupture properties of IN-718. One possible mechanism to explain this property improvement relies on the boron and phosphorus additions slowing down the growth of {gamma}{double_prime} and {gamma}{prime} precipitates during high temperature service or aging. However, atom probe analysis found no segregation of boron and phosphorus to {gamma}-{gamma}{double_prime} or to {gamma}-{gamma}{prime} interfaces in the alloys with the high boron and high phosphorus levels. No difference in growth rates were found by transmission electron microscopy in the sizes of the {gamma}{double_prime} or {gamma}{prime} in alloys with high phosphorus and high boron as compared to commercial alloys and to alloys with even lower levels of phosphorus and boron. Atom probe analysis further found that much of the phosphorus, boron, and carbon segregated to grain boundaries. Creep curves comparing the alloys with high levels of phosphorus and boron and alloys with low levels of phosphorus and boron show a large difference in strain rate in the first hours of the test. These results suggest that the boron and phosphorus may have a direct effect on dislocation mobility by some pinning mechanism.

Horton, J.A.; McKamey, C.G.; Miller, M.K. [Oak Ridge National Lab., TN (United States); Cao, W.D.; Kennedy, R.L. [Teledyne Allvac, Monroe, NC (United States)

1997-06-01

387

Synthesis of boron nitride nanotubes with SiC nanowire as template  

SciTech Connect

Highlights: {yields} Boron nitride nanotubes (BNNTs) have been fabricated using SiC nanowires as template. {yields} SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. {yields} A template self-sacrificing mechanism is responsible for the formation of BNNTs. -- Abstract: A novel template method for the preparation of boron nitride nanotubes (BNNTs) using SiC nanowire as template and ammonia borane as precursor is reported. We find out that the SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. The as-prepared products are well characterized by means of complementary analytical techniques. A possible formation mechanism is disclosed. The method developed here paves the way for large scale production of BNNTs.

Zhong, B.; Song, L. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China)] [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Huang, X.X. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)] [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wen, G.W., E-mail: g.wen@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xia, L. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China)] [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China)

2011-09-15

388

Kinetics and mechanism of the deep electrochemical oxidation of sodium diclofenac on a boron-doped diamond electrode  

NASA Astrophysics Data System (ADS)

The kinetics and mechanism of the deep oxidation of sodium diclofenac on a boron-doped diamond electrode are studied to develop a technique for purifying wastewater from pharmaceutical products. The products of sodium diclofenac electrolysis are analyzed using cyclic voltammetry and nuclear magnetic resonance techniques. It is shown that the toxicity of the drug and products of its electrolysis decreases upon its deep oxidation.

Vedenyapina, M. D.; Borisova, D. A.; Rosenwinkel, K.-H.; Weichgrebe, D.; Stopp, P.; Vedenyapin, A. A.

2013-08-01

389

Developments in Accelerator Based Boron Neutron Capture Therapy  

NASA Astrophysics Data System (ADS)

This paper will review the current status of Boron Neutron Capture Therapy (BNCT), from basic physical mechanisms and clinical indications, to neutron beam development and dosimetry. For in-hospital facilities, particle accelerators presently provide the favoured option, and this paper concentrates on this approach to neutron beam production for BNCT. Various accelerator-based approaches will be reviewed, but discussion will concentrate on the Birmingham programme, particularly the design of a suitable neutron beam delivery system and the experimental validation of Monte Carlo simulations on a mock-up neutron beam moderation system. The use of dose modifying factors to evaluate the likely clinical utility of an epithermal neutron beam will also be discussed, with illustrations from the Birmingham programme.

Green, Stuart

1998-06-01

390

Chemical vapor deposition of films in the boron and nitrogen system  

Microsoft Academic Search

The hot filament assisted chemical vapor deposition of B-N solids using different boron source gases (BClsb3 and Bsb2Hsb6) with NHsb3 and Hsb2 was demonstrated and the reaction conditions necessary to deposit well crystallized Bsb{x}N products established. These results are consistent with other results in that high temperatures and highly nitrogen rich atmosperes are necessary for the formation of a well

Katsuhito Yoshida

1997-01-01

391

Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes  

Microsoft Academic Search

Electrolysis in aqueous 1 M HClO4 and 1 M H2SO4 solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO4 the main reaction is oxygen evolution, while in H2SO4 the main reaction is the formation of H2S2O8. In both electrolytes small amounts of O3 and

P. A. Michaud; M. Panizza; L. Ouattara; T. Diaco; G. Foti; Ch. Comninellis

2003-01-01

392

Effect of Boron on Dynamic Change of Seed Yield and Quality Formation in Developing Seed of Brassica napus  

Microsoft Academic Search

Rapeseed (Brassica napus) is one of main oil crops in the world and also a potential bioenergy crop. Because of the sensitivity of Brassica napus to boron (B) deficiency and the wide distribution of low available-B soils in main areas of rapeseed production, more and more attention is being paid to the effect of B nutrition on yield and quality

M. Yang; L. Shi; F. S. Xu; Y. H. Wang

2009-01-01

393

Production, Distribution, and Applications of Californium-252 Neutron Sources  

SciTech Connect

The radioisotope {sup 252}Cf is routinely encapsulated into compact, portable, intense neutron sources with a 2.6-year half-life. A source the size of a person's little finger can emit up to 10{sup 11} neutrons/s. Californium-252 is used commercially as a reliable, cost-effective neutron source for prompt gamma neutron activation analysis (PGNAA) of coal, cement, and minerals, as well as for detection and identification of explosives, laud mines, and unexploded military ordnance. Other uses are neutron radiography, nuclear waste assays, reactor start-up sources, calibration standards, and cancer therapy. The inherent safety of source encapsulations is demonstrated by 30 years of experience and by U.S. Bureau of Mines tests of source survivability during explosions. The production and distribution center for the U. S Department of Energy (DOE) Californium Program is the Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory (ORNL). DOE sells The radioisotope {sup 252}Cf is routinely encapsulated into compact, portable, intense neutron sources with a 2.6- year half-life. A source the size of a person's little finger can emit up to 10 neutrons/s. Californium-252 is used commercially as a reliable, cost-effective neutron source for prompt gamma neutron activation analysis (PGNAA) of coal, cement, and minerals, as well as for detection and identification of explosives, laud mines, and unexploded military ordnance. Other uses are neutron radiography, nuclear waste assays, reactor start-up sources, calibration standards, and cancer therapy. The inherent safety of source encapsulations is demonstrated by 30 years of experience and by U.S. Bureau of Mines tests of source survivability during explosions. The production and distribution center for the U. S Department of Energy (DOE) Californium Program is the Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory(ORNL). DOE sells {sup 252}Cf to commercial reencapsulators domestically and internationally. Sealed {sup 252}Cf sources are also available for loan to agencies and subcontractors of the U.S. government and to universities for educational, research, and medical applications. The REDC has established the Californium User Facility (CUF) for Neutron Science to make its large inventory of {sup 252}Cf sources available to researchers for irradiations inside uncontaminated hot cells. Experiments at the CUF include a land mine detection system, neutron damage testing of solid-state detectors, irradiation of human cancer cells for boron neutron capture therapy experiments, and irradiation of rice to induce genetic mutations.

Balo, P.A.; Knauer, J.B.; Martin, R.C.

1999-10-03

394

Status of NASA's Advanced Radioisotope Power Conversion Technology Research and Development  

NASA Astrophysics Data System (ADS)

NASA's Advanced Radioisotope Power Systems (RPS) development program is funding the advancement of next generation power conversion technologies that will enable future missions that have requirements that can not be met by either the ubiquitous photovoltaic systems or by current Radioisotope Power Systems (RPS). Requirements of advanced radioisotope power systems include high efficiency and high specific power (watts/kilogram) in order to meet mission requirements with less radioisotope fuel and lower mass. Other Advanced RPS development goals include long-life, reliability, and scalability so that these systems can meet requirements for a variety of future space applications including continual operation surface missions, outer-planetary missions, and solar probe. This paper provides an update on the Radioisotope Power Conversion Technology Project which awarded ten Phase I contracts for research and development of a variety of power conversion technologies consisting of Brayton, Stirling, thermoelectrics, and thermophotovoltaics. Three of the contracts continue during the current Phase II in the areas of thermoelectric and Stirling power conversion. The accomplishments to date of the contractors, project plans, and status will be summarized.

Wong, Wayne A.; Anderson, David J.; Tuttle, Karen L.; Tew, Roy C.

2006-01-01

395

Feasibility Study of a Three-Stage Radioisotope-Powered Mars Ascent Vehicle  

NASA Astrophysics Data System (ADS)

Recent advancements in methods of housing radioisotopes at the Center for Space Nuclear Research have led to the concept of a radioisotope thermal rocket--a rocket powered by the accumulated heat of radioisotope decay. Heat energy from the decay can be accumulated over long periods of time in a material of high heat capacity to create a thermal capacitor. The capacitor can then be discharged at such a rate as to provide high power for short periods of time; in this case, the heat is transferred to a gas propellant. This paper explores the feasibility of using a radioisotope thermal rocket with in-situ atmospheric CO2 propellant to deliver a 10 kg payload from the Martian surface to a 200 km circular orbit about Mars. Models of heat transfer, gas dynamics, and ascent mechanics are constructed to test performance of different core materials and geometries. Of the configurations tested, the best simulation results fail to meet the altitude and velocity requirements by 12 km and 50 m/s respectively. The proximity to success indicates that the given models are capable of reaching orbital parameters if optimization algorithms and closed-loop guidance methods are employed. It is believed, however, that the current models underestimate expansion losses to the degree that if more realistic and computationally-intensive models are incorporated, the effect will definitively disprove the concept with currently available technology. Based on this preliminary research, radioisotope thermal rockets utilizing current technology are not capable of serving as Mars ascent vehicles.

Chalpek, T. M.; Allen, R. E.; Guan, J. Y.; Rao, S. S.; Howe, S. D.

396

Status of NASA's Advanced Radioisotope Power Conversion Technology Research and Development  

NASA Technical Reports Server (NTRS)

NASA s Advanced Radioisotope Power Systems (RPS) development program is funding the advancement of next generation power conversion technologies that will enable future missions that have requirements that can not be met by either the ubiquitous photovoltaic systems or by current Radioisotope Power Systems (RPS). Requirements of advanced radioisotope power systems include high efficiency and high specific power (watts/kilogram) in order to meet mission requirements with less radioisotope fuel and lower mass. Other Advanced RPS development goals include long-life, reliability, and scalability so that these systems can meet requirements for a variety of future space applications including continual operation surface missions, outer-planetary missions, and solar probe. This paper provides an update on the Radioisotope Power Conversion Technology Project which awarded ten Phase I contracts for research and development of a variety of power conversion technologies consisting of Brayton, Stirling, thermoelectrics, and thermophotovoltaics. Three of the contracts continue during the current Phase II in the areas of thermoelectric and Stirling power conversion. The accomplishments to date of the contractors, project plans, and status will be summarized.

Wong, Wayne A.; Anderson, David J.; Tuttle, Karen L.; Tew, Roy C.

2006-01-01

397

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

NASA Technical Reports Server (NTRS)

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

Chu, T. L.

1975-01-01

398

From Boron Cluster to Two-Dimensional Boron Sheet on Cu(111) Surface: Growth Mechanism and Hole Formation  

PubMed Central

As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster BN with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure continuous growth of two-dimensional (2D) boron cluster. During growth process, hexagonal holes can easily arise at the edge of a 2D triangular boron cluster and then diffuse entad. Hence, large-scale boron monolayer with mixed hexagonal-triangular geometry can be obtained via either depositing boron atoms directly on Cu(111) surface or soft landing of small planar BN clusters. Our theoretical predictions would stimulate further experiments of synthesizing boron sheets on metal substrates and thus enrich the variety of 2D monolayer materials. PMID:24241341

Liu, Hongsheng; Gao, Junfeng; Zhao, Jijun

2013-01-01

399

Asymmetric energy transport in defected boron nitride nanoribbons: Implications for thermal rectification  

E-print Network

Asymmetric energy transport in defected boron nitride nanoribbons: Implications for thermal) Asymmetric energy transport in defected boron nitride nanoribbons: Implications for thermal rectification simulations, the thermal transport properties of boron nitride nanoribbons (BNNR) containing geometrically

Deymier, Pierre

400

Journal of luminescence 127, 595 (2007) Photoluminescence of hexagonal boron nitride: effect of  

E-print Network

1 Journal of luminescence 127, 595 (2007) Photoluminescence of hexagonal boron nitride: effect : hexagonal boron nitride ; photoluminescence ; surface oxydation ; UV-laser irradiation. * Corresponding on the UV laser induced fluorescence of hexagonal boron nitride (h-BN) following nanosecond laser

Paris-Sud XI, Université de

401

Effects of Partial Hydrogenation on the Structure and Electronic Properties of Boron Nitride Nanotubes  

E-print Network

Effects of Partial Hydrogenation on the Structure and Electronic Properties of Boron Nitride and electronic properties of boron nitride nanotubes are investigated via density functional theory calculations achievable route for controlling the electronic properties of boron nitride nanotubes. INTRODUCTION

Hod, Oded

402

Tunneling characteristics in chemical vapor deposited graphene hexagonal boron nitride graphene junctions  

E-print Network

1 Tunneling characteristics in chemical vapor deposited graphene ­ hexagonal boron nitride Abstract: Large area chemical vapor deposited graphene and hexagonal boron nitride was used to fabricate graphene ­ hexagonal boron nitride ­ graphene symmetric field effect transistors. Gate control

Feenstra, Randall

403

Boron nitride: Composition, optical properties and mechanical behavior  

NASA Astrophysics Data System (ADS)

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

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

1987-04-01

404

Energy landscape of fullerene materials: A comparion of boron to boron nitride and carbon  

NASA Astrophysics Data System (ADS)

After the discovery of the C60 fullerene some 25 years ago, many more hollow and endohedrally doped structures made out of various elements have been proposed theoretically. However, since no other fullerenes have been synthesized up to date, the question arises whether experimentalists have just not yet found a way to synthesize these theoretically predicted fullerenes, or whether they do not exist at all in nature. Following the theoretical discovery of the B80 fullerene by Szwacki et al, various other fullereneand stuffed fullerene structures were proposed but none of them could be synthesized in the laboratory yet. Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glass like. Medium size boron clusters exhibit many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nano structures.

de, Sandip

2012-02-01

405

Synthesis of new boron-rich building blocks for boron neutron capture therapy or energy-filtering transmission electron microscopy.  

PubMed

The synthesis of a new ortho-carborane derivative, tetracarboranylketone 4, is reported here. Ketone 4 was prepared from a tetraalkynylated ketone by the addition of decaborane. The keto group was then easily modified to yield the glycosides 17alpha and 18beta, which contain glucose or galactose, respectively, and the nucleotide 13b. In addition to ketone 4, which is acyclic, cyclic ketone 8 was also synthesised. X-ray diffraction analysis of compound 4 indicated the presence of two toluene guest molecules per molecule of the host compound. Furthermore, compound 4 displays a rather low cytotoxicity. These novel products can be used as building blocks to create a new class of biomolecules containing high-density carborane clusters. Such molecules may constitute powerful tools for applications like Boron Neutron Capture Therapy or Energy-Filtering Transmission Electron Microscopy. PMID:15185371

Raddatz, Stefan; Marcello, Marco; Kliem, Hans-Christian; Tröster, Helmut; Trendelenburg, Michael F; Oeser, Thomas; Granzow, Christof; Wiessler, Manfred

2004-04-01

406

Research of boron films deposited on different substrates  

NASA Astrophysics Data System (ADS)

Semiconductor detector that incorporate neutron reactive material within the same detector demonstrates a new method for neutron dosimetry and boron neutron reactive therapy seems to be a promising treatment. Boron films were deposited on single crystalline silicon, glass, and CVD diamond film by magnetron sputtering, close-space sublimation and vacuum evaporation. The properties of the samples were characterized by SEM, which shows vacuum evaporation method is suitable for depositing high quality boron films.

Zhou, Jie; Wang, Linjun; Huang, Jian; Tang, Ke; Ren, Bing; Yao, Beiling; Xia, Yiben

2013-09-01

407

Low-loss binder for hot pressing boron nitride  

DOEpatents

Borazine derivatives used as low-loss binders and precursors for making ceramic boron nitride structures. The derivative forms the same composition as the boron nitride starting material, thereby filling the voids with the same boron nitride material upon forming and hot pressing. The derivatives have a further advantage of being low in carbon thus resulting in less volatile byproduct that can result in bubble formation during pressing.

Maya, Leon (Oak Ridge, TN)

1991-01-01

408

Ultrahigh resolution mass spectroscopy of boron cluster ions  

Microsoft Academic Search

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

Dale Jacobson; Thomas Horsky; Wade Krull; Bob Milgate

2005-01-01

409

Oxidation of boron nitride in an arc heated jet.  

NASA Technical Reports Server (NTRS)

Two grades of hot pressed boron nitride and a boron nitride composite were subjected to oxidation tests in a 2.5 megawatt atmospheric arc jet. The results showed that fabrication and/or composition influenced thermal shock and oxidation resistance. Changes in surface structure and recession due to oxidation suggest correlation with specimen composition. The boron nitride composite reacted with the oxygen in the hot subsonic airstream to produce a glassy coating on the hot face surface.

Buckley, J. D.

1971-01-01

410

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

411

Boron nitride nanotube: synthesis and applications  

NASA Astrophysics Data System (ADS)

Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA/JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800°C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

Tiano, Amanda L.; Park, Cheol; Lee, Joseph W.; Luong, Hoa H.; Gibbons, Luke J.; Chu, Sang-Hyon; Applin, Samantha; Gnoffo, Peter; Lowther, Sharon; Kim, Hyun Jung; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Kang, Jin Ho; Sauti, Godfrey; Thibeault, Sheila A.; Yamakov, Vesselin; Wise, Kristopher E.; Su, Ji; Fay, Catharine C.

2014-04-01

412

Asymmetric twins in rhombohedral boron carbide  

SciTech Connect

Superhard materials consisting of light elements have recently received considerable attention because of their ultrahigh specific strength for a wide range of applications as structural and functional materials. However, the failure mechanisms of these materials subjected to high stresses and dynamic loading remain to be poorly known. We report asymmetric twins in a complex compound, boron carbide (B{sub 4}C), characterized by spherical-aberration-corrected transmission electron microscopy. The atomic structure of boron-rich icosahedra at rhombohedral vertices and cross-linked carbon-rich atomic chains can be clearly visualized, which reveals unusual asymmetric twins with detectable strains along the twin interfaces. This study offers atomic insights into the structure of twins in a complex material and has important implications in understanding the planar defect-related failure of superhard materials under high stresses and shock loading.

Fujita, Takeshi, E-mail: tfujita@wpi-aimr.tohoku.ac.jp; Guan, Pengfei; Madhav Reddy, K.; Hirata, Akihiko; Guo, Junjie [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Chen, Mingwei, E-mail: mwchen@wpi-aimr.tohoku.ac.jp [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

2014-01-13

413

Dimerization of boron triiodide at high pressure  

NASA Astrophysics Data System (ADS)

High-pressure phase transition of boron triiodide (BI3) is investigated using first-principles methods, with the crystal structure of the high-pressure phase predicted. The structure is consistent with the information on this phase available from experiments. Significantly, the BI3 molecules are predicted to form B2I6 dimers that are structurally analogous to the D2h diborane molecules. Dimerization of BI3 molecules yields a notable volume drop that triggers a first-order phase transition. Using the predicted structure, the calculated equation of state, phase transition pressure, and the metallization transition pressure are in an excellent agreement with the experimental measurements. Dimerization in crystalline BI3 provides insight for the understanding of covalently bound boron halide dimers, which were previously unknown.

Yao, Yansun; Klug, Dennis D.; Marto?ák, Roman; Patchkovskii, Serguei

2011-06-01

414

Facile Synthesis of Ternary Boron Carbonitride Nanotubes  

PubMed Central

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

2009-01-01

415

Method for fabricating boron carbide articles  

DOEpatents

The present invention is directed to the fabrication of boron carbide articles having length-to-diameter or width ratios greater than 2 to 1. The process of the present invention is practiced by the steps comprising hot pressing boron carbide powder into article segments or portions in which the segments have a length-to-diameter or width ratio less than 1.5, aligning a plurality of the initially hot-pressed segments in a hot-pressing die with the end surfaces of the segments placed in intimate contact with one another, and then hot pressing the aligned segments into an article of the desired configuration. The resulting article exhibits essentially uniform density throughout the structure with the bonds between the segments being equivalent in hardness, strength, and density to the remainder of the article.

Ardary, Zane L. (Oak Ridge, TN); Reynolds, Carl D. (Clinton, TN)

1980-01-01

416

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

417

Hexagonal boron nitride grown by MOVPE  

NASA Astrophysics Data System (ADS)

Hexagonal boron nitride (h-BN) has a potential for optical device applications in the deep ultraviolet spectral region. For several decades, only amorphous and turbostratic boron nitride (BN) films had been grown by chemical vapor deposition and metalorganic vapor phase epitaxy. By introducing flow-rate modulation epitaxy (FME), which enables us to reduce parasitic reactions and lower the optimal growth temperature, we have succeeded in growing single-phase h-BN epitaxial films on nearly lattice-matched (1 1 1) Ni substrates. The h-BN epitaxial films exhibit near-band-gap ultraviolet luminescence at a wavelength of 227 nm in cathodoluminescence at room temperature. The combination of FME and the lattice-matched substrate paves the way for the epitaxial growth of high-quality h-BN.

Kobayashi, Y.; Akasaka, T.; Makimoto, T.

2008-11-01

418

Techniques for increasing boron fiber fracture strain  

NASA Technical Reports Server (NTRS)

Improvement in the strain-to-failure of CVD boron fibers is shown possible by contracting the tungsten boride core region and its inherent flaws. The results of three methods are presented in which etching and thermal processing techniques were employed to achieve core flaw contraction by internal stresses available in the boron sheath. After commercially and treatment induced surface flaws were removed from 203 micrometers (8 mil) fibers, the core flaw was observed to be essentially the only source of fiber fracture. Thus, fiber strain-to-failure was found to improve by an amount equal to the treatment induced contraction on the core flaw. Commercial feasibility considerations suggest as the most cost effective technique that method in which as-produced fibers are given a rapid heat treatment above 700 C. Preliminary results concerning the contraction kinetics and fracture behavior observed are presented and discussed both for high vacuum and argon gas heat treatment environments.

Dicarlo, J. A.

1977-01-01

419

Energy Conversion Options for Advanced Radioisotope Power Systems  

NASA Astrophysics Data System (ADS)

Static and dynamic energy conversion technologies for Advanced Radioisotope Power Systems (ARPSs) are reviewed and their impact on the system's total mass and specific electrical power and the amount of 238PuO2 fuel needed for the heat source are assessed and compared. Conversion technologies considered are Segmented and cascaded Thermoelectric, Alkali-Metal Thermal-to-Electric Conversion, and Free Piston Stirling Engines (FPSEs) and, for comparison, SiGe thermoelectric. Estimates for a 100 We ARPS indicate that when using SiGe thermoelectric, operating between 1273 K and 573 K, 8 General Purpose Heat Source (GPHS) modules would be required and the system's specific power is ~ 4.6 We/kg. Using STE converters, operating between 973 K and 373 K, 5 GPHS modules are required and the ARPS's specific power is ~ 7.28 We/kg. The next generation STE converters that could operate between 1273 K and 573 K, for a projected system efficiency of 13.8%, decrease the number of GPHS modules needed to 4 and increase the system's specific power to ~ 9.9 We/kg. With cascaded SiGe-STE converters, operating between 1273 K and 373 K, the system's efficiency could be as much as 16%, requiring only 3 GPHS modules, for an estimated specific power of 10.7 We/kg. This specific power is more than twice that for SOA RTG. With the current version 1.0 of FPSEs, the 100 We ARPS needs only two GPHS modules, but its specific power (4.1 we/kg) is slightly lower than that of SOA RTG (4.6 We/kg). Future introduction of versions 1.1 and 2.0 engines, with slightly higher conversion efficiency and significantly lower mass, could increase the system's specific power to ~ 7.5 We/kg, using the same number of GPHS modules as version 1.0 engines. With Na-AMTEC and K-AMTEC, the 100 We ARPS needs 3 and 4 GPHS modules, respectively, for an estimated specific power of 5.3 and 5.8 We/kg, respectively.

El-Genk, Mohamed S.

2003-01-01

420

Delivery of therapeutic radioisotopes using nanoparticle platforms: potential benefit in systemic radiation therapy  

PubMed Central

Radiation therapy is an effective cancer treatment option in conjunction with chemotherapy and surgery. Emerging individualized internal and systemic radiation treatment promises significant improvement in efficacy and reduction of normal tissue damage; however, it requires cancer cell targeting platforms for efficient delivery of radiation sources. With recent advances in nanoscience and nanotechnology, there is great interest in developing nanomaterials as multifunctional carriers to deliver therapeutic radioisotopes for tumor targeted radiation therapy, to monitor their delivery and tumor response to the treatment. This paper provides an overview on developing nanoparticles for carrying and delivering therapeutic radioisotopes for systemic radiation treatment. Topics discussed in the review include: selecting nanoparticles and radiotherapy isotopes, strategies for targeting nanoparticles to cancers, together with challenges and potential solutions for the in vivo delivery of nanoparticles. Some examples of using nanoparticle platforms for the delivery of therapeutic radioisotopes in preclinical studies of cancer treatment are also presented. PMID:24198480

Zhang, Longjiang; Chen, Hongwei; Wang, Liya; Liu, Tian; Yeh, Julie; Lu, Guangming; Yang, Lily; Mao, Hui

2010-01-01

421

Stirling Radioisotope Power System as an Alternative for NASAs Deep Space Missions  

NASA Astrophysics Data System (ADS)

The NASA Glenn Research Center (GRC) and the Department of Energy (DOE) are developing a free-piston Stirling convertor for a Stirling Radioisotope Power System (SRPS) to provide on-board electric power for future NASA deep space missions. The SRPS currently being developed provides about 100 watts and reduces the amount of radioisotope fuel by a factor of four over conventional Radioisotope Thermoelectric Generators (RTG). The present SRPS design has a specific power of approximately 4 W/kg which is comparable to an RTG. GRC estimates for advanced versions of the SRPS with improved heat source integration, lightweight Stirling convertors, composite radiators, and chip-packaged controllers improves the specific mass to about 8 W/kg. Additional information is contained in the original extended abstract.

Shaltens, R. K.; Mason, L. S.; Schreiber, J. G.

2001-01-01

422

Normal Modes in Hexagonal Boron Nitride  

Microsoft Academic Search

Pyrolytic boron nitride, a rather anisotropic material among the III-V compounds, has been investigated in reflection and transmission, using polarized infrared radiation in the spectral range from 100 cm-1 to 3000 cm-1. The reflection spectra have been analyzed by means of a Kramers-Kronig analysis and a classical oscillator fit. The results indicate one infrared active lattice mode for in-plane motion

R. Geick; C. H. Perry; G. Rupprecht

1966-01-01

423

Theory of graphitic boron nitride nanotubes  

Microsoft Academic Search

Based upon the similarities in properties between carbon- and BN-based (BN=boron nitride) materials, we propose that BN-based nanotubes can be stable and study their electronic structure. A simple Slater-Koster tight-binding scheme has been applied. All the BN nanotubes are found to be semiconducting materials. The band gaps are larger than 2 eV for most tubes. Depending on the helicity, the

Angel Rubio; Jennifer Corkill; Marvin Cohen

1994-01-01

424

Packing C60 in Boron Nitride Nanotubes  

Microsoft Academic Search

We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride nanotubes (BNNTs). For small-diameter BNNTs, the wire consists of a linear chain of C60 molecules. With increasing BNNT inner diameter, unusual C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) that are unknown for bulk or thin-film forms of C60. C60

W. Mickelson; S. Aloni; Wei-Qiang Han; John Cumings; A. Zettl

2003-01-01

425

Tandem Cycloisomerization/Suzuki Coupling of Arylethynyl MIDA Boronates  

PubMed Central

A tandem gold-catalyzed cycloisomerization/Suzuki cross coupling sequence involving arylethynyl-N-methyliminodiacetic acid boronates is described. Combining the mildness of homogeneous gold catalysis with the versatility of N-methyliminodiacetic acid (MIDA) boronates, this tandem two-step method enables the rapid assembly of various aryl-substituted heterocycles without having to isolate or purify any heterocyclic MIDA boronate intermediates. Another major advantage of this method is that a wide range of heterocycles bearing different aryl groups may be made from a single MIDA boronate alkyne precursor. PMID:21765556

Chan, Julian M. W.; Amarante, Giovanni W.; Toste, F. Dean

2011-01-01

426

Ecological risk assessment of a wetland exposed to boron  

SciTech Connect

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

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

1997-11-01

427

Novel rare earth boron-rich solids  

SciTech Connect

A new series of boron-rich solids ReB{sub 22}C{sub 2}N (Re: Y, Ho, Er, Tm, Lu) was synthesized by traditional solid-state reaction. The crystal structure of the representative compound YB{sub 22}C{sub 2}N was solved by direct method from powder X-ray diffraction (XRD) data and transmission electron microscope (TEM) analysis. The unit cell of the new structure is rhombohedral with space group R-3m (No. 166), lattice constant a = b = 5.623(0) {angstrom} and c = 44.785(3) {angstrom} with six formula units in one unit cell. The atoms of boron in the solids, like most of the boron-rich solids, exist with icosahedral and octahedral clusters, and the whole crystal shows a layered structure. The interconnected nine layers of icosahedron and three layers of octahedron in a unit cell build the whole framework of the new phase and rare earth metal atoms reside in voids of the octahedron layers. The neighboring icosahedral layers link through C-B-C chains besides the direct bonding of B-B. Both experimental and structural analysis indicated that the nitrogen atoms in the new phase can be replaced with carbon.

Zhang, Fuxiang; Leithe-Jasper, Andreas; Xu, Jun; Mori, Takao; Matsui, Yoshio, Tanaka, Takaho; Okada, Shigeru

2001-06-01

428

The Alcator C-Mod Boronization System  

NASA Astrophysics Data System (ADS)

A system for boronization of the Alcator C-Mod vacuum vessel and plasma facing components was installed and began routine operation in January of 1996. Significant suppression of impurity levels and record stored energy were achieved during ICRF heating following boronization. Electron cyclotron discharge cleaning in dilute diborane gas (10% D_2B_6, 90% helium) was selected as the simplest and most cost efficient method to achieve boronization in a short period of time. Safety of the diborane storage, delivery, and exhaust systems was the prime consideration in the overall design. In addition, complete remote operation of the system was required in order to minimize personnel exposure to potential gas leaks. The delivery system and its performance will be detailed, as well as discussion of unanticipated post operative clean up problems. Upgrades to the system utilizing multipoint diborane delivery and glow discharge paddles are currently being installed. Supported by U.S. DOE Contract No. DE-AC02-78ET51013

Reddy, C.; Fiore, C. L.; Irby, J.; Bosco, J.; Childs, R.; Marmar, E.; McCracken, G.; Esser, G.; Winter, J.; Hawthorne, M.; Watson, R.

1996-11-01

429

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

430

The effects of boron on the electron paramagnetic resonance spectra of alanine irradiated with thermal neutrons  

SciTech Connect

The effects of boric acid admixture on the intensity and line structure of EPR spectra of free radicals produced in alanine by thermal neutrons are presented. The EPR signal enhancement, up to a factor of 40 depending on the boron concentration, is related to additional energy deposition in alanine crystals by the disintegration products resulting from the capture of a thermal neutron by boron, {sup 10}B(n,{alpha}){sup 7}Li. The changes in the shape of the EPR spectra observed by changing the microwave power are due to the differences in the microwave power saturation of the free radicals produced by a low-LET radiation and those produced by the high-LET components of the radiation after the neutron capture reaction. 27 refs., 4 figs., 2 tabs.

Ciesielski, B.; Wielopolski, L. [Brookhaven National Lab., Upton, NY (United States)

1995-10-01

431

The Effect of Time, Temperature and Composition on Boron Carbide Synthesis by Sol-gel Method  

NASA Astrophysics Data System (ADS)

To minimize free carbon residue in the boron carbide (B4C) powder, a modified sol-gel process is performed where the starting materials as boric acid and citric acid compositions are adjusted. Because of boron loss in the form of B2O2(g) during the reduction reaction of the stoichiometric starting composition, the final B4C powders contain carbon residues. Thus, an excess H3BO3 is used in the reaction to compensate the loss and to obtain stoichiometric powders. Parameters of production have been determined using x-ray diffraction analysis and particle size analyses. The synthesized B4C powder using an excess boric acid composition shows no trace of carbon.

Hadian, A. M.; Bigdeloo, J. A.

2008-02-01

432

Early clinical experience of boron neutron capture therapy for glioblastoma multiforme  

SciTech Connect

Boron neutron capture therapy (BNCT) is a binary treatment modality that can selectively irradiate tumor tissue. BNCT uses drugs containing a stable isotope of boron. {sup 10}B, to sensitize tumor cells to irradiation by low energy (thermal) neutrons. The interaction of the {sup 10}B with a thermal neutron (neutron capture) causes the {sup 10}B nucleus to split, releasing an alpha particle and a lithium nucleus. These products of the {sup 10}B(n, {alpha}){sup 7}Li reaction are very damaging to cells but have a combined path length in tissue of approximately 14 {mu}m, or roughly the diameter of one or two cells. Thus, most of the ionizing energy imparted to tissue is localized to {sup 10}B-loaded cells.

Joel, D.D.; Bergland, R.; Capala, J. [and others

1995-12-31

433

Methods of Fabricating Scintillators with Radioisotopes for Beta Battery Applications  

NASA Technical Reports Server (NTRS)

Technology has been developed for a class of self-contained, long-duration power sources called beta batteries, which harvest the energy contained in the radioactive emissions from beta decay isotopes. The new battery is a significant improvement over the conventional phosphor/solar cell concept for converting this energy in three ways. First, the thin phosphor is replaced with a thick scintillator that is transparent to its own emissions. By using a scintillator sufficiently thick to completely stop all the beta particles, efficiency is greatly improved. Second, since the energy of the beta particles is absorbed in the scintillator, the semiconductor photodetector is shielded from radiation damage that presently limits the performance and lifetime of traditional phosphor converters. Finally, instead of a thin film of beta-emitting material, the isotopes are incorporated into the entire volume of the thick scintillator crystal allowing more activity to be included in the converter without self-absorption. There is no chemical difference between radioactive and stable strontium beta emitters such as Sr-90, so the beta emitter can be uniformly distributed throughout a strontium based scintillator crystal. When beta emitter material is applied as a foil or thin film to the surface of a solar cell or even to the surface of a scintillator, much of the radiation escapes due to the geometry, and some is absorbed within the layer itself, leading to inefficient harvesting of the energy. In contrast, if the emitting atoms are incorporated within the scintillator, the geometry allows for the capture and efficient conversion of the energy of particles emitted in any direction. Any gamma rays associated with secondary decays or Bremsstrahlung photons may also be absorbed within the scintillator, and converted to lower energy photons, which will in turn be captured by the photocell or photodiode. Some energy will be lost in this two-stage conversion process (high-energy particle to low-energy photons to electric current). The geometric advantage partially offsets this as well, since the absorption depth of high-energy beta radiation is much larger than the depth of a p-n junction. Thus, in a p-n junction device, much of the radiation is absorbed far away from the junction, and the electron- hole pairs are not all effectively collected. In contrast, with a transparent scintillator the radiation can be converted to light in a larger volume, and all of the light can be collected in the active region of the photodiode. Finally, the new device is more practical because it can be used at much higher power levels without unduly shortening its lifetime. While the crystal structure of scintillators is also subject to radiation damage, their performance is far more tolerant of defects than that of semiconductor junctions. This allows the scintillator- based approach to use both higher energy isotopes and larger quantities of the isotopes. It is projected that this technology has the potential to produce a radioisotope battery with up to twice the efficiency of presently used systems.

Rensing, Noa M.; Squillante, Michael R.; Tieman, Timothy C.; Higgins, William; Shiriwadkar, Urmila

2013-01-01

434

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

PubMed Central

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

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

1992-01-01

435

Boron containing amino acid compounds and methods for their use  

SciTech Connect

The present invention provides new boron containing amino acid compounds and methods for making these compounds by contacting melphalan or another nitrogen mustard derivative and sodium borocaptate. The present invention also provides a method of treating a mammal having a tumor by administering to the mammal a therapeutically effective amount of the new boron containing amino acid compounds.

Glass, J.D.; Coderre, J.A.

2000-01-25

436

Quantitative phase analysis of boron nitride nanotubes using Rietveld refinement  

Microsoft Academic Search

Crystalline boron nitride nanotubes (BNNTs) with an average outer diameter of about 40 nm and several micrometres in length were synthesized by chemical vapour deposition from boron and magnesium oxide. Rietveld refinement and 11B solid-state nuclear magnetic resonance (NMR) spectroscopy were employed to quantitatively determine the phase of synthesized BNNTs. The structural parameters for the BNNTs were determined by Rietveld

Yong-Il Kim; Jae Kap Jung; Kwon-Sang Ryu; Seung-Hoon Nahm; Duncan H. Gregory

2005-01-01

437

Boron reduction performance of reverse osmosis seawater desalination process  

Microsoft Academic Search

In recent years, seawater desalination systems using reverse osmosis (RO) membranes have been constructed to settle the lack of drinking water. RO desalination membranes have high rejection for most of solutes in seawater. Japanese drinking water standards for the water quality of the permeate can be achieved except for boron. Therefore, the boron rejection needs to be considered in the

Masahide Taniguchi; Masaru Kurihara; Shoji Kimura

2001-01-01

438

Modelling boron-lined proportional counter response to neutrons.  

PubMed

The detailed Monte Carlo simulation of a boron-lined proportional counter response to a neutron source has been presented. The MCNP4C and experimental data on different source-moderator geometries have been given for comparison. The influence of different irradiation geometries and boron-lining thicknesses on the detector response has been studied. PMID:23531556

Shahri, A; Ghal-Eh, N; Etaati, G R

2013-09-01

439

Predicting Boron, Molybdenum, Selenium, and Arsenic Adsorption in Soil Systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

A chemical surface complexation model was applied to boron, molybdenum, selenium, and arsenic adsorption on up to 49 soils selected for variation in soil properties. The surface complexation model was able to fit boron, molybdenum, selenite, and arsenate adsorption on the soils. General regression...

440

Method for removal of phosgene from boron trichloride  

DOEpatents

Selective ultraviolet photolysis using an unfiltered mercury arc lamp has been used to substantially reduce the phosgene impurity in a mixture of boron trichloride and phosgene. Infrared spectrophotometric analysis of the sample before and after irradiation shows that it is possible to highly purify commercially available boron trichloride with this method. 5 figs.

Freund, S.M.

1983-09-20