Showing papers on "Isotopes of boron published in 1994"
TL;DR: It is shown that δ 11 B values of raw and treated sewage effluents from the Dan Region Sewage Reclamation Project overlap those of natural nonmarine sodium borate minerals but differ significantly from those of regional uncontaminated groundwater and seawater.
Abstract: Boron isotope composition and concentration of sewage effluent and pristine and contaminated groundwater from the Coastal Plain aquifer of Israel have been determined. The application of boron compounds, especially sodium perborate as a bleaching agent in detergents, leads to an enrichment of boron in wastewaters. Anthropogenic boron in wastewater is isotopically distinct from natural boron in groundwater and thus can be utilized to identify the source of contamination. It is shown that δ 11 B (where δ 11 B=[(( 11 B/ 10 B)sample/( 11 B/ 10 B) NBS-951S -1]×1000) values of raw and treated sewage effluents from the Dan Region Sewage Reclamation Project (δ 11 B=5.3-2.9‰) overlap those of natural nonmarine sodium borate minerals (0.9‰ to +10.2‰) but differ significantly from those of regional uncontaminated groundwater (∼30‰) and seawater (39‰)
311 citations
TL;DR: In this article, the boron content and δ11B values of 40 oceanic basalt glasses (N-MORB, E-MorB, BABB, OIB and OIB) were determined at ±10% relative, with values ranging from 0.34 to 0.74 ppm.
219 citations
TL;DR: The first high-field boron nuclear magnetic resonance spectra of sufficient resolution to detect multiple sites in borate glass were reported in this paper, where the more populated sites were assigned to borons in boroxol rings, and the less populated site was assigned to non-ring BORON trioxide units.
Abstract: The first high-field boron nuclear magnetic resonance spectra of sufficient resolution to detect multiple sites in borate glass are reported. These results are obtained by using dynamic angle spinning nuclear magnetic resonance spectroscopy, in fields of 4.7, 7.1 and 8.4 Tesla, to measure the boron-11 spectrum in samples enriched in boron-10. Two boron sites, which differ in quadrupole interaction strength by 5%, in chemical shift by 5 ppm, and have relative population of 3:1, were resolved. The more populated site is assigned to boron in boroxol rings, and the less populated site is assigned to non-ring boron trioxide units. The chemical shift difference between these sites suggests that the BO bond in the boroxol rings is somewhat longer than that in the boron trioxide groups.
120 citations
TL;DR: In this paper, a simple and precise technique for the measurement of boron isotopes in carbonates and natural waters is presented, which results in 100 ± 1% recovery of bboron from sample solutions.
119 citations
TL;DR: To measure boron transport in animal systems, 20 micrograms of 10B were fed to a fasted rat and 95% of the 10B was recovered from the urine and 4% from the feces.
Abstract: The commercial availability of inductively coupled plasma-mass spectrometry technology (ICP-MS) has presented the opportunity to measure the boron concentrations and isotope ratios in a large number of samples with minimal sample preparation. A typical analytical sequence for fecal samples consists of 25 acid blanks, 1 digestion blank, 5 calibration solutions, 4 standard reference material solutions, 10 samples, and 4 natural abundance bias standards. Boron detection limits (3 x 1 sigma) for acid blanks are 0.11 ppb for 10B, and 0.40 ppb for 11B. Isotope ratios were measured in fecal samples with 20 to 50 ppb boron with < 2% relative standard deviation. Rapid washout and minimal memory effects were observed for a 50 ppb beryllium internal standard, but a 200 ppb boron biological sample had a 1.0 ppb boron memory after a 6-min washout. Boron isotope ratios in geological materials are highly variable; apparently this variability is reflected in plants of a fixed natural abundance value for boron requires that a natural abundance ratio be determined for each sample or related data set. The natural abundance variability also prevents quantitation and calculation of isotope dilution by instrument-supplied software. To measure boron transport in animal systems, 20 micrograms of 10B were fed to a fasted rat. During the 3 days after a 10B oral dose, 95% of the 10B was recovered from the urine and 4% from the feces. Urinary isotope ratios, 11B/10B, changed from a natural abundance of 4.1140 to an enriched value of 0.95077, a 77% change.(ABSTRACT TRUNCATED AT 250 WORDS)
36 citations
TL;DR: In this paper, a boron isotope study was carried out on groundwaters from the northern Rift Valley, Israel, which is consistent with previous interpretations based on Na/Cl (0.58) and δ18O (−3‰) values.
35 citations
TL;DR: In this paper, a consistent description of the data in terms of neutrino resonant conversion admits Φ B / Φ b 0 = 0.4−2.5 in small mixing domain and ΦB / √ B 0 = 1−3 in large mixing domain (here Φb 0 ≡5.7·10 6 cm −2 s −1 is the flux in the reference SSM).
30 citations
TL;DR: In this article, the Coulomb energy depends on the discrete values for the pair separation in the expected manner, including a Bohr radius correction for the three closest pairs, likely candidates for the pairs are the nitrogen donor and the boron acceptor.
26 citations
TL;DR: Tissue studies designed to correlate ion microscopic boron images to microscopic structure are feasible using cryogenic sample preparation and ion microscopy, which demonstrates minimized redistribution artifact.
Abstract: A well-characterized in vitro cryogenic preparation for ion microscopic isotope imaging, which minimizes redistribution of diffusible species, was used to determine the distribution of boron in GS-9L gliosarcoma cells incubated with the boron neutron capture therapy agent, p-boronophenylalanine (BPA). At the subcellular level, boron from BPA distributes relatively homogeneously within the glioma cell. Boron from BPA was eliminated rapidly, indicating that most is unbound. Thus a large pool of boron is susceptible to diffusion artifact. Removal of this artifact increases the degree of confidence in microdosimetric results inferred from the homogeneous subcellular distribution. The ion microscopic imaging of boron in subcutaneous tumors cryofixed in situ was achieved in rats treated with BPA. Boron signals from BPA were adequate to image microdistributions at the 1-micron resolution level. As in the in vitro case, boron did not localize discretely at the subcellular level. However, boron heterogeneity was seen at the tissue level. Physiologically valid cellular potassium and sodium levels were seen, which demonstrates minimized redistribution artifact. Future tissue studies designed to correlate ion microscopic boron images to microscopic structure are feasible using cryogenic sample preparation and ion microscopy.
23 citations
TL;DR: In this article, the infrared spectra of boron trifluoride isolated in nitrogen and argon matrices have been recorded, and reasonable assignments have been made for all six infrared active modes of the most abundant isotopomer, (11 BF 3 ) 2, expected to appear above about 400 cm -1, as well as eight bands of the mixed isotopic species, 10 BF 3 · 11 BF 3, and five of the least abundant dimer.
22 citations
TL;DR: An extensive multiconfiguration Hartree-Fock (MCHF) calculation of the isotope shift and hyperfine structure in the resonance line of B II at 1362 angstrom has been performed as mentioned in this paper.
Abstract: An extensive multiconfiguration Hartree-Fock (MCHF) calculation of the isotope shift and hyperfine structure in the resonance line of B II at 1362 angstrom has been performed. The calculated B-11-B-10 isotope shift is 13.3 mangstrom with an estimated uncertainty of 1%. The calculated interaction constants A and B give a hyperfine structure splitting of less than 0.45 mangstrom for both isotopes. The size of the isotope shift in the B II line is similar to the limit of detection in high-resolution observations with the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope when side A becomes operational after the service mission.
TL;DR: In this article, the first time ketones were studied as donors in the boron isotope exchange reaction, the ideal single stage separation factors, α, measured for these ketones, were between 1.038 and 1.043 at 30°C.
Abstract: Chemical exchange between gaseous boron trifluoride (BF3) and the liquid BF3·dimethyl ether complex has been used extensively for the commercial fractionation of boron isotopes. Several compounds never before studied as donors in the isotope exchange reaction were examined to determine if they were viable replacements for the dimethyl ether system. For the first time, ketones were studied as donors in the boron isotope exchange reaction. The ketones examined were acetone, methyl isobutyl ketone, and diisobutyl ketone. The ideal single stage separation factors, α, measured for these ketones were between 1.038 and 1.043 at 30°C. The observed separation factor for a fourth donor system, nitromethane, was 1.067 at 30°C, well above that predicted by theory or observed for any known BF3/donor system. For each of the systems studied, the separation factors were greater than the value of α = 1.027 reported for the dimethyl ether/BF3 system at 30°C. In view of the experimentally observed separation factor...
Patent•
01 Apr 1994TL;DR: In this paper, a process of and apparatus for the continuous and selective separation of boron-10 (B 10 ) isotope having high neutron capture cross-section from bboron-11 (B10) isotope by using a weak base ion exchange resin and water eluant in a continuous annular chromatograph is described.
Abstract: This invention relates to a process of and apparatus for the continuous and selective separation of boron-10 (B 10 ) isotope having high neutron capture cross-section from boron-11 (B 10 ) isotope from a mixture of boron isotopes in a boric acid solution by using a weak base ion exchange resin and water eluant in a continuous annular chromatograph. The invention is a continuous, steady-state, method for separating boron isotopes in aqueous boric acid solutions, including the steps of: (A) preparing an aqueous boric acid feed solution comprising a mixture of boron isotopes; (B) loading the boric acid feed solution onto an ion exchange resin, preferably a weak base anion exchange resin, contained in an ion exchange column of a continuous annular chromatograph at a location on the column, the ion exchange column having a sufficient length and width to resolve isotopes of boron, especially the boron-10 and the boron-11 isotopes into distinct product fractions; (C) feeding an aqueous eluant, preferably water, onto the ion exchange resin in the column of the continuous annular chromatograph at a location on the column to elute the boric acid feed solution along the length of the column of said continuous annular chromatograph and to effect separation of the isotopes in the feed solution.
Patent•
25 Jan 1994
TL;DR: The isotopes of boron, 10 B and 11 B are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF 3 and a liquid BF 3.
Abstract: The isotopes of boron, 10 B and 11 B, are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF 3 and a liquid BF 3 . donor molecular addition complex formed between BF 3 gas and a donor chosen from the group consisting of: nitromethane, acetone, methyl isobutyl ketone, or diisobutyl ketone.
Patent•
30 Dec 1994
TL;DR: The energy spectra of many isotopes of elements from Be to Ne were obtained and a two-parameter thermal model fits the angular distributions of the low-energy fragments.
Abstract: Inclusive fragment isotope spectra were measured at 15[degree], 30[degree], 45[degree], and 60[degree] for the [sup 36]Ar + Ag reaction at 35 MeV/nucleon. The energy spectra of many isotopes of elements from Be to Ne were obtained. A two-parameter thermal model fits the angular distributions of the low-energy fragments. One parameter, source kinetic energy/temperature, is proportional to fragment mass number. The other, total fragment production cross section, after adjustment for binding energy, has a decreasing exponential dependence on mass number.
01 Jan 1994
TL;DR: B, have a quite large relative mass difference from each other and show obvious isotope fractionation in nature （up to 50‰）, which can be used to study various kinds of geological problems.
Abstract: B, have a quite large relative mass difference from each other and show obvious isotope fractionation in nature （up to 50‰）,which can be used to study various kinds of geological problems.
Journal Article•
TL;DR: In this paper, the ability to quantitate boron in tissues is an important aspect to neutron capture therapy, and Boron determination in tissue utilizing various spectroscopic methods is described.
Abstract: The ability to quantitate boron in tissues is an important aspect to neutron capture therapy. Boron determination in tissue utilizing various spectroscopic methods is described.
Journal Article•
TL;DR: The model presented provides a rapid, quantitative, and cost-effective approach to the evaluation of the biological efficacy of these drugs.
Abstract: The resurgence of interest in boron neutron capture therapy (BNCT) as a treatment for malignant lesions has resulted in the synthesis of numerous boron compounds as candidates for clinical use. The model presented provides a rapid, quantitative, and cost-effective approach to the evaluation of the biological efficacy of these drugs.
TL;DR: The boron isotope effect (10B-11B) was investigated for the boride carbide superconductors YNi2B2C and YPd2B 2C as discussed by the authors.
Abstract: The boron isotope effect (10B-11B) was investigated for the boride carbide superconductors YNi2B2C and YPd2B2C. A sizable isotope effect was observed for both systems and values for the boron isotope exponent were similar in the two systsems (αB≈0.27).