Absorbed dose measurements from a 90Y radionuclide liquid solution using LiF:Mg,Cu,P thermoluminescent dosimeters.

In the last few years there has been an increasing interest in the measurement of the absorbed dose from radionuclides, with special attention devoted to molecular radiotherapy treatments. In particular, the determination of the absorbed dose from beta emitting radionuclides in liquid solution poses a number of issues when dose measurements are performed using thermoluminescent dosimeters (TLD). Finite volume effect, i.e. the exclusion of radioactivity from the volume occupied by the TLD is one of these. Furthermore, TLDs need to be encapsulated into some kind of waterproof envelope that unavoidably contributes to beta particle attenuation during the measurement. The purpose of this study is twofold: I) to measure the absorbed dose to water, Dw, using LiF:Mg,Cu,P chips inside a PMMA cylindrical phantom filled with a homogenous 90YCl3 aqueous solution II) to assess the uncertainty budget related to Dw measurements. To this purpose, six cylindrical PMMA phantoms were manufactured at ENEA. Each phantom can host a waterproof PMMA stick containing 3 TLD chips encapsulated by a polystyrene envelope. The cylindrical phantoms were manufactured so that the radioactive liquid environment surrounds the whole stick. Finally, Dw measurements were compared with Monte Carlo (MC) calculations. The measurement of absorbed dose to water from 90YCl3 radionuclide solution using LiF:Mg,Cu,P TLDs turned out to be a viable technique, provided that all necessary correction factors are applied. Using this method, a relative combined standard uncertainty in the range 3.1-3.7% was obtained on each Dw measurement. The major source of uncertainty was shown to be TLDs calibration, with associated uncertainties in the range 0.7-2.2%. Comparison of measured and MC-calculated absorbed dose per emitted beta particle provided good results, with the two quantities being in the ratio 1.08.

Experimental Assessment of Lithium Hydride's Space Radiation Shielding Performance and Monte Carlo Benchmarking.

The harmful effects of space radiation pose a serious health risk to astronauts participating in future long-term missions. Such radiation effects must be considered in the design phase of space vessels as well as in mission planning. Crew radioprotection during long periods in deep space (e.g., transit to Mars) represents a major challenge, especially because of the strong restrictions on the passive shielding load allowed on-board the vessel. Novel materials with better shielding performance compared to the "gold standard" high-density polyethylene are therefore greatly needed. Because of the high hydrogen content of hydrides, lithium hydride has been selected as a starting point for further studies of promising candidates to be used as passive shielding materials. In the current experimental campaign, the shielding performance of lithium hydride was assessed by measuring normalized dose, primary beam attenuation and neutron ambient dose equivalent using 430 MeV/u 12C, 600 MeV/u 12C and 228 MeV proton beams. The experimental data were then compared to predictions from the Monte Carlo transport codes PHITS and GRAS. The experimental results show an increased shielding effectiveness of lithium hydride compared to reference materials like polyethylene. For instance, the attenuation length for 600 MeV/u 12C primary particles in lithium hydride is approximately 20% shorter compared to polyethylene. Furthermore, the comparison results between both transport codes indicates that the standard Tripathi-based total reaction cross-section model of PHITS cannot accurately reproduce the presented experimental data, whereas GRAS shows reasonable agreement.

EVALUATION OF NEUTRON SCATTERING CORRECTION USING THE SEMI-EMPIRICAL METHOD AND THE SHADOW-CONE METHOD FOR THE NEUTRON FIELD OF THE KOREA ATOMIC ENERGY RESEARCH INSTITUTE.

When neutron survey metres are calibrated in neutron fields, the results for room- and air-scattered neutrons vary according to the distance from the source and the size, shape and construction of the neutron calibration room. ISO 8529-2 recommends four approaches for correcting these effects: the shadow-cone method, semi-empirical method, generalised fit method and reduced-fitting method. In this study, neutron scattering effects are evaluated and compared using the shadow-cone and semi-empirical methods for the neutron field of the Korea Atomic Energy Research Institute (KAERI). The neutron field is constructed using a 252Cf neutron source positioned in the centre of the neutron calibration room. To compare the neutron scattering effects using the two correction methods, measurements and simulations are performed using respectively KAERI's Bonner sphere spectrometer (BBS) and Monte Carlo N-Particle code at twenty different positions. Neutron spectra are measured by a europium-activated lithium iodide [6LiI(Eu)] scintillator in combination with the BBS. The calibration factors obtained using each methods show good agreement within 1.1%.

IMAGING OF PROTON BRAGG PEAKS IN LiF.

Lithium fluoride (LiF) is one of the most common thermoluminescent phosphors routinely used in radiation protection services. Another advantageous property of LiF is radiophotoluminescence, whose occurs after its irradiation due to the creation of color centers. Excitation of LiF samples with a blue light causes the emission of photoluminescence, which spectrum consists of two peaks at ~520 and ~670 nm. The work was focused on imaging of Bragg peaks of proton beams routinely applied at the proton eye radiotherapy facility operating at the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN) in Krakow by the measurement of the fluorescence light in LiF crystals excited with a 445 nm blue light after their previous irradiation with the proton beams of energies of 28, 30, 40 and 50 MeV. The range of proton beams in LiF crystals for different energies was calculated by Monte Carlo simulations.

NUCLEAR HEATING IN LIF DOSEMETERS IN A FUSION NEUTRON FIELD, TRIAL OF DIRECT COMPARISON OF EXPERIMENTAL AND SIMULATED RESULTS.

The results of nuclear heating measured by means of thermoluminescent dosemeters (TLD-LiF) in a Cu block irradiated by 14 MeV neutrons are presented. The integral Cu experiment relevant for verification of copper nuclear data at neutron energies characteristic for fusion facilities was performed in the ENEA FNG Laboratory at Frascati. Five types of TLDs were used: highly photon sensitive LiF:Mg,Cu,P (MCP-N), 7LiF:Mg,Cu,P (MCP-7) and standard, lower sensitivity LiF:Mg,Ti (MTS-N), 7LiF:Mg,Ti (MTS-7) and 6LiF:Mg,Ti (MTS-6). Calibration of the detectors was performed with gamma rays in terms of air-kerma (10 mGy of 137Cs air-kerma). Nuclear heating in the Cu block was also calculated with the use of MCNP transport code Nuclear heating in Cu and air in TLD's positions was calculated as well. The nuclear heating contribution from all simulated by MCNP6 code particles including protons, deuterons, alphas tritons and heavier ions produced by the neutron interactions were calculated. A trial of the direct comparison between experimental results and results of simulation was performed.

Risk assessment of lithium-ion battery explosion: chemical leakages.

Use of lithium-ion batteries has raised safety issues owing to chemical leakages, overcharging, external heating, or explosions. A risk assessment was conducted for hydrofluoric acid (HF) and lithium hydroxide (LiOH) which potential might leak from lithium-ion batteries. The inhalation no-observed-adverse-effect-level (NOAEL) for HF was 0.75 mg/kg/d. When a lithium-ion battery explodes in a limited space, HF emissions amount to 10-100 ppm. Assuming the worst-case scenario, the conversion rate was calculated to be 81.8 mg/m3, and the average daily dose (ADD) was 19.5 mg/kg/d. Consequently, the margin of exposure (MOE = NOAEL/ADD) was 0.034, a value which constitutes an unsafe inhalation exposure for HF. Conversely, skin toxicity NOAEL for LiOH was 41.35 mg/kg/d-. This LiOH value reflects the amount of lithium in the lithium-ion battery, which is generated upon contact between water and the electrolyte. The quantity of lithium in a mobile phone is approximately 295 mg, and systemic exposure dose (SED) was 4.92 mg/kg/d. Accordingly, the MOE (NOAEL/SED) value was 8.41, and skin exposure of LiOH was deemed as safe for humans. However, it is important that Energy Storage System batteries still require safety measures and technologies for next-generation batteries, to prevent any potential explosions of lithium-ion batteries.

Track-average LET of secondary electrons generated in LiF:Mg,Ti and liquid water by 20-300 kV x-ray, 137Cs and 60Co beams.

Electrons generated in matter by photons could be a fundamental basis for an adequate analysis of radiation effects and damage. We have studied separately the 'primary electrons' generated directly by photons from the 'secondary electrons' (SE) produced by electron-electron interactions. In this work, track-average linear energy transfer, [Formula: see text], of SE in LiF:Mg,Ti and liquid water produced by twelve photon energy beams from 20 kV x-ray to 60Co gamma rays have been investigated using the EGSnrc Monte Carlo Code. The exposure of LiF:Mg,Ti in different phantom materials has been considered. Depending on the photon energy, SE represent 40%-90% of the total electron fluence (TEF) between 1 keV and 10 keV, being higher when the photon energy increases. Independent of the medium, [Formula: see text] versus mean photon energy displays a local minimum at around 40 keV, followed by a local maximum at ~80 keV-100 keV. The [Formula: see text] of SE generated by the x-ray beams are of order of 11 keV µm-1 to 19 keV µm-1 in LiF:Mg,Ti and 5 keV µm-1 to 9 keV µm-1 in liquid water which represent 3-5 times those produced by 60Co gamma rays in both media. These values were considerably greater than those of TEF, by factors of 3-8. Furthermore, [Formula: see text] of SE generated in liquid water by 20 kV-200 kV x-rays are similar to those of 76 MeV-120 MeV 3He ions. Contrary to the TEF, where [Formula: see text] were independent of the phantom material, at low photon energies [Formula: see text] of SE was found to be sensitive to the surrounding medium showing higher values within the phantom than in air. This result, which agrees with published experimental results, implies the importance of the SE ionization density for an understanding of dosimeter response induced by photon beams.

Lithium Hexamethyldisilazane Transformation of Transiently Protected 4-Aza/Benzimidazole Nitriles to Amidines and their Dimethyl Sulfoxide Mediated Imidazole Ring Formation.

Trimethylsilyl-transient protection successfully allowed the use of lithium hexamethyldisilazane to prepare benzimidazole (BI) and 4-azabenzimidazole (azaBI) amidines from nitriles in 58-88% yields. This strategy offers a much better choice to prepare BI/azaBI amidines than the lengthy, low-yielding Pinner reaction. Synthesis of aza/benzimidazole rings from aromatic diamines and aldehydes was affected in dimethyl sulfoxide in 10-15 min, while known procedures require long time and purification. These methods are important for the BI/azaBI-based drug industry and for developing specific DNA binders for expanded therapeutic applications.

Evaluation of LiF:Mg,Ti (TLD-100) for Intraoperative Electron Radiation Therapy Quality Assurance.

BACKGROUND: Purpose of the present work was to investigate thermoluminescent dosimeters (TLDs) response to intraoperative electron radiation therapy (IOERT) beams. In an IOERT treatment, a large single radiation dose is delivered with a high dose-per-pulse electron beam (2-12 cGy/pulse) during surgery. To verify and to record the delivered dose, in vivo dosimetry is a mandatory procedure for quality assurance. The TLDs feature many advantages such as a small detector size and close tissue equivalence that make them attractive for IOERT as in vivo dosimeters. METHODS: LiF:Mg,Ti dosimeters (TLD-100) were irradiated with different IOERT electron beam energies (5, 7 and 9 MeV) and with a 6 MV conventional photon beam. For each energy, the TLDs were irradiated in the dose range of 0-10 Gy in step of 2 Gy. Regression analysis was performed to establish the response variation of thermoluminescent signals with dose and energy. RESULTS: The TLD-100 dose-response curves were obtained. In the dose range of 0-10 Gy, the calibration curve was confirmed to be linear for the conventional photon beam. In the same dose region, the quadratic model performs better than the linear model when high dose-per-pulse electron beams were used (F test; p<0.05). CONCLUSIONS: This study demonstrates that the TLD dose response, for doses ≤10 Gy, has a parabolic behavior in high dose-per-pulse electron beams. TLD-100 can be useful detectors for IOERT patient dosimetry if a proper calibration is provided.

Cost-Effective Hierarchical Catalysts for Promoting Hydrogen Release from Complex Hydrides.

Fe nanoparticles (∼10 nm), used to grow carbon nanotubes (CNTs), have an outstanding ability to catalyze the dehydrogenation of LiAlH4 . The CNTs help connect Fe and LiAlH4 and create microchannels among the composite, thus promoting the release of hydrogen. Inspired by these results, a supercritical-CO2 -fluid-assisted deposition technique is employed to decorate the Fe/CNTs with highly dispersed nanosized Ni (∼2 nm in diameter) for better performance. With the incorporation of 10 wt % of this hierarchical catalyst (Ni/Fe/CNTs), the initial dehydrogenation temperature of LiAlH4 is decreased from ∼135 to ∼40 °C. At 100 °C, this catalyzed LiAlH4 takes only ∼0.1 h to release 4.5 wt % hydrogen, which is more than 100 times faster than the time needed with pristine LiAlH4 . The dehydrogenation mechanism of the complex hydride is examined using in situ synchrotron X-ray diffraction.

Variation in the calibrated response of LiF, Al2O3, and silicon dosimeters when used for in-phantom measurements of source photons with energies between 30 KeV AND 300 KeV.

The MCNP5 radiation transport code was used to quantify changes in the absorbed dose conversion factor for LiF, Al2O3, and silicon-based electronic dosimeters calibrated in-air using standard techniques and summarily used to measure absorbed dose to water when placed in a water phantom. A mono-energetic photon source was modeled at energies between 30 keV and 300 keV for a point-source placed at the center of a water phantom, a point-source placed at the surface of the phantom, and for a 10-cm radial field geometry. Dosimetric calculations were obtained for water, LiF, Al2O3, and silicon at depths of 0.2 cm and 10 cm from the source. These results were achieved using the MCNP5 *FMESH photon energy-fluence tally, which was coupled with the appropriate DE/DF card for each dosimetric material studied to convert energy-fluence into the absorbed dose. The dosimeter's absorbed dose conversion factor was calculated as a ratio of the absorbed dose to water to that of the dosimeter measured at a specified phantom depth. The dosimeter's calibration value also was obtained. Based on these results, the absorbed dose conversion factor for a LiF dosimeter was found to deviate from its calibration value by up to 9%, an Al2O3 dosimeter by 43%, and a silicon dosimeter by 61%. These data therefore can be used to obtain LiF, Al2O3, and silicon dosimeter correction factors for mono-energetic and poly-energetic sources at measurement depths up to 10 cm under the irradiation geometries investigated herein.

Homologation of boronic esters with organolithium compounds: a computational assessment of mechanism.

Ab initio calculations are reported for the reaction of methyl boronic ester with organolithium reagents with α-leaving groups. The best calculations rely on density functional theory prediction of structures and coupled-cluster theory calculation of accurate potential energies. The results provide strong confirmation of the feasibility of a two-step mechanism with rapid initial formation of a boron-ate complex followed by slower migration of methyl from boron to carbon with loss of the leaving group. The calculated free energy of activation is consistent with observed kinetic behavior, and the calculations provide a framework for exploring substituent and other effects on reactivity. Obtaining reasonable agreement with experiment in this way is not trivial and requires careful treatment of level of theory (density functional theory calculations tend to yield inaccurate results), of conformational complexity, especially for the ate complexes, and of the nature of the microscopic model of reactants and solvent. The methodological challenges and possible pitfalls, many of which are relevant more broadly to computational modeling of organic reaction mechanisms, are discussed in detail.

Alpha particle and proton relative thermoluminescence efficiencies in LiF:Mg,Cu,P:is track structure theory up to the task?

Low-energy alpha particle and proton heavy charged particle (HCP) relative thermoluminescence (TL) efficiencies are calculated for the major dosimetric glow peak in LiF:Mg,Cu,P (MCP-N) in the framework of track structure theory (TST). The calculations employ previously published TRIPOS-E Monte Carlo track segment values of the radial dose in condensed phase LiF calculated at the Instituto National de Investigaciones Nucleares (Mexico) and experimentally measured normalised (60)Co gamma-induced TL dose-response functions, f(D), carried out at the Institute of Nuclear Physics (Poland). The motivation for the calculations is to test the validity of TST in a TL system in which f(D) is not supralinear (f(D) >1) and is not significantly dependent on photon energy contrary to the behaviour of the dose-response of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100). The calculated HCP relative efficiencies in LiF:MCP-N are 23-87% lower than the experimentally measured values, indicating a weakness in the major premise of TST which exclusively relates HCP effects to the radiation action of the secondary electrons liberated by the HCP slowing down. However, an analysis of the uncertainties involved in the TST calculations and experiments (i.e. experimental measurement of f(D) at high levels of dose, sample light self-absorption and accuracy in the estimation of D(r), especially towards the end of the HCP track) indicate that these may be too large to enable a definite conclusion. More accurate estimation of sample light self-absorption, improved measurements of f(D) and full-track Monte Carlo calculations of D(r) incorporating improvements of the low-energy electron transport are indicated in order to reduce uncertainties and enable a final conclusion.

Response of LiF:Mg,Ti thermoluminescent dosimeters at photon energies relevant to the dosimetry of brachytherapy (<1 MeV).

PURPOSE: High energy photon beams are used in calibrating dosimeters for use in brachytherapy since absorbed dose to water can be determined accurately and with traceability to primary standards in such beams, using calibrated ion chambers and standard dosimetry protocols. For use in brachytherapy, beam quality correction factors are needed, which include corrections for differences in mass energy absorption properties between water and detector as well as variations in detector response (intrinsic efficiency) with radiation quality, caused by variations in the density of ionization (linear energy transfer (LET) -distributions) along the secondary electron tracks. The aim of this work was to investigate experimentally the detector response of LiF:Mg,Ti thermoluminescent dosimeters (TLD) for photon energies below 1 MeV relative to (60)Co and to address discrepancies between the results found in recent publications of detector response. METHODS: LiF:Mg,Ti dosimeters of formulation MTS-N Poland were irradiated to known values of air kerma free-in-air in x-ray beams at tube voltages 25-250 kV, in (137)Cs- and (60)Co-beams at the Swedish Secondary Standards Dosimetry Laboratory. Conversions from air kerma free-in-air into values of mean absorbed dose in the dosimeters in the actual irradiation geometries were made using EGSnrc Monte Carlo simulations. X-ray energy spectra were measured or calculated for the actual beams. Detector response relative to that for (60)Co was determined at each beam quality. RESULTS: An increase in relative response was seen for all beam qualities ranging from 8% at tube voltage 25 kV (effective energy 13 keV) to 3%-4% at 250 kV (122 keV effective energy) and (137)Cs with a minimum at 80 keV effective energy (tube voltage 180 kV). The variation with effective energy was similar to that reported by Davis et al. [Radiat. Prot. Dosim. 106, 33-43 (2003)] with our values being systematically lower by 2%-4%. Compared to the results by Nunn et al. [Med. Phys. 35, 1861-1869 (2008)], the relative detector response as a function of effective energy differed in both shape and magnitude. This could be explained by the higher maximum read-out temperature (350 °C) used by Nunn et al. [Med. Phys. 35, 1861-1869 (2008)], allowing light emitted from high-temperature peaks with a strong LET dependence to be registered. Use of TLD-100 by Davis et al. [Radiat. Prot. Dosim. 106, 33-43 (2003)] with a stronger super-linear dose response compared to MTS-N was identified as causing the lower relative detector response in this work. CONCLUSIONS: Both careful dosimetry and strict protocols for handling the TLDs are required to reach solid experimental data on relative detector response. This work confirms older findings that an over-response relative to (60)Co exists for photon energies below 200-300 keV. Comparison with the results from the literature indicates that using similar protocols for annealing and read-out, dosimeters of different makes (TLD-100, MTS-N) differ in relative detector response. Though universality of the results has not been proven and further investigation is needed, it is anticipated that with the use of strict protocols for annealing and read-out, it will be possible to determine correction factors that can be used to reduce uncertainties in dose measurements around brachytherapy sources at photon energies where primary standards for absorbed dose to water are not available.

Ground-state properties of LiH by reptation quantum Monte Carlo methods.

We apply reptation quantum Monte Carlo to calculate one- and two-electron properties for ground-state LiH, including all tensor components for static polarizabilities and hyperpolarizabilities to fourth-order in the field. The importance sampling is performed with a large (QZ4P) STO basis set single determinant, directly obtained from commercial software, without incurring the overhead of optimizing many-parameter Jastrow-type functions of the inter-electronic and internuclear distances. We present formulas for the electrical response properties free from the finite-field approximation, which can be problematic for the purposes of stochastic estimation. The α, γ, A and C polarizability values are reasonably consistent with recent determinations reported in the literature, where they exist. A sum rule is obeyed for components of the B tensor, but B(zz,zz) as well as ß(zzz) differ from what was reported in the literature.

Uncertainty assessment of a two element LiF:Mg,Ti TL personal dosemeter using Monte-Carlo techniques.

This paper presents the results of an uncertainty assessment and a comparison study of dose algorithms for H(p)(10) and H(p)(0.07) used for evaluating a routine two-element thermoluminescent whole-body dosemeter. Due to the photon-energy response of the two different filtered LiF:Mg,Ti detector elements, the application of a dose algorithm is necessary to assess the relevant photon doses over the rated energy range with an acceptable energy dependence. A linear dose algorithm with two different sets of parameters was designed to assess the personal dose equivalent in the relevant quantity H(p)(10) and H(p)(0.07). Based on the experimental results from calibrations on the ISO water slab phantom, a detailed uncertainty analysis was performed by means of Monte-Carlo (MC) techniques and other analytical methods. The uncertainty contribution of the individual detector element signals was taken into special consideration. For this analysis, realistic energy and angular distributions were applied to calculate the dosemeter response. It is concluded that the MC method is an appropriate tool to perform uncertainty calculations. The possibility to assign arbitrary probability density functions to the input quantities, as well as to define a complex model function (dose algorithm) allows the simulation of irradiation conditions close to reality.

Preliminary assessment of the dose to the interventional radiologist in fluoro-CT-guided procedures.

A preliminary assessment of the occupational dose to the intervention radiologist received in fluoroscopy computerised tomography (CT) used to guide the collection of lung and bone biopsies is presented. The main aim of this work was to evaluate the capability of the reading system as well as of the available whole-body (WB) and extremity dosemeters used in routine monthly monitoring periods to measure per procedure dose values. The intervention radiologist was allocated 10 WB detectors (LiF: Mg, Ti, TLD-100) placed at chest and abdomen levels above and below the lead apron, and at both right and left arms, knees and feet. A special glove was developed with casings for the insertion of 11 extremity detectors (LiF:Mg, Cu, P, TLD-100H) for the identification of the most highly exposed fingers. The H(p)(10) dose values received above the lead apron (ranged 0.20-0.02 mSv) depend mainly on the duration of the examination and on the placement of physician relative to the beam, while values below the apron are relatively low. The left arm seems to receive a higher dose value. H(p)(0.07) values to the hand (ranged 36.30-0.06 mSv) show that the index, middle and ring fingers are the most highly exposed. In this study, the wrist dose was negligible compared with the finger dose. These results are preliminary and further studies are needed to better characterise the dose assessment in CT fluoroscopy.

Mysteries of LiF TLD response following high ionisation density irradiation: nanodosimetry and track structure theory, dose response and glow curve shapes.

Three outstanding effects of ionisation density on the thermoluminescence (TL) mechanisms giving rise to the glow peaks of LiF:Mg,Ti (TLD-100) are currently under investigation: (1) the dependence of the heavy charged particle (HCP) relative efficiency with increasing ionisation density and the effectiveness of its modelling by track structure theory (TST), (2) the behaviour of the TL efficiency, f(D), as a function of photon energy and dose. These studies are intended to promote the development of a firm theoretical basis for the evaluation of relative TL efficiencies to assist in their application in mixed radiation fields. And (3) the shape of composite peak 5 in the glow curve for various HCP types and energies and following high-dose electron irradiation, i.e. the ratio of the intensity of peak 5a to peak 5. Peak 5a is a low-temperature satellite of peak 5 arising from electron-hole capture in a spatially correlated trapping centre/luminescent centre (TC/LC) complex that has been suggested to possess a potential as a solid-state nanodosemeter due to the preferential electron/hole population of the TC/LC at high ionisation density. It is concluded that (1) the predictions of TST are very strongly dependent on the choice of photon energy used in the determination of f(D); (2) modified TST employing calculated values of f(D) at 2 keV is in agreement with 5-MeV alpha particle experimental results for composite peak 5 but underestimates the 1.5-MeV proton relative efficiencies. Both the proton and alpha particle relative TL efficiencies of the high-temperature TL (HTTL) peaks 7 and 8 are underestimated by an order of magnitude suggesting that the HTTL efficiencies are affected by other factors in addition to radial electron dose; (3) the dose-response supralinearity of peaks 7 and 8 change rapidly with photon energy: this behaviour is explained in the framework of the unified interaction model as due to a very strong dependence on photon energy of the relative intensity of localised recombination and (4) the increased width and decrease in T(max) of composite peak 5 as a function of ionisation density is due to the greater relative intensity of peak 5a (a low-temperature component of peak 5 arising from two-energy transfer events, which leads to localised recombination).

Assessment of the extent of starch dissolution in dimethyl sulfoxide by 1H NMR spectroscopy.

Complete dissolution is needed for the separation, characterization, or homogeneous labeling of whole starch molecules. A method is presented to quantify the extent of starch dissolution in DMSO for the first time; it is validated on a commercial rice starch. It is used directly on starch dispersions containing possible undissolved or co-dissolved species. High-amylose maize starches, known to be digested slowly in vivo, only quantitatively dissolve in the presence of high concentrations of an H-bond disrupter, LiBr, although they form clear dispersions at low LiBr concentrations. Starch quantitatively dissolves from waxy rice flours; non-starch components partially co-dissolve but do not interfere with the dissolution quantification.

Airborne monitoring to distinguish engineered nanomaterials from incidental particles for environmental health and safety.

Two methods were used to distinguish airborne engineered nanomaterials from other airborne particles in a facility that produces nano-structured lithium titanate metal oxide powder. The first method involved off-line analysis of filter samples collected with conventional respirable samplers at each of seven locations (six near production processes and one outdoors). Throughout most of the facility and outdoors, respirable mass concentrations were low (<0.050 mg/m(3)) and were attributed to particles other than the nanomaterial (<10% by mass titanium determined with inductively coupled plasma atomic emission spectrometry). In contrast, in a single area with extensive material handling, mass concentrations were greatest (0.118 mg m(-3)) and contained up to 39% +/- 11% lithium titanium, indicating the presence of airborne nanomaterial. Analysis of the filter samples collected in this area by transmission electron microscope and scanning electron microscope revealed that the airborne nanomaterial was associated only with spherical aggregates (clusters of fused 10-80 nm nanoparticles) that were larger than 200 nm. This analysis also showed that nanoparticles in this area were the smallest particles of a larger distribution of submicrometer chain agglomerates likely from welding in an adjacent area of the facility. The second method used two, hand-held, direct-reading, battery-operated instruments to obtain a time series of very fine particle number (<300 nm), respirable mass, and total mass concentration, which were then related to activities within the area of extensive material handling. This activity-based monitoring showed that very fine particle number concentrations (<300 nm) had no apparent correlation to worker activities, but that sharp peaks in the respirable and total mass concentration coincided with loading a hopper and replacing nanomaterial collection bags. These findings were consistent with those from the filter-based method in that they demonstrate that airborne nanoparticles in this facility are dominated by "incidental" sources (e.g., welding or grinding), and that the airborne "engineered" product is predominately composed of particles larger than several hundred nanometers. The methods presented here are applicable to any occupational or environmental setting in which one needs to distinguish incidental sources from engineered product.