Study of a neutron radiography system using Cf neutron source

This paper presents a study about moderation and collimation of a neutron radiography system using ²⁵²Cf. A Monte Carlo Code, MCNP4B, has been used to obtain a maximum and more homogeneous thermal neutron flux in the collimator outlet next to the image plane. Among the various moderator materials investigated, high density polyethylene proved to be the most efficient, with a thermalization factor of 56 cm². Using a collimator design assembly it was possible to obtain a normalized thermal neutron flux, at the image plane of 6×10⁻⁶ n cm⁻² s⁻¹ at an effective collimator ratio of 7.5, or 3.2×10⁻⁷ n cm⁻² s⁻¹ at an effective collimator ratio of 50.     

Development of a new type multi-moderator neutron spectrometer

A multi-moderator spectrometer on which is mounted a pair of ⁶Li and ⁷Li glass scintillators has been developed as a new type neutron spectrometer which can measure the neutron spectrum in a mixed field of neutrons, charged particles and gamma-rays realized in space. The particle identification capability was investigated in neutron-gamma-ray and neutron-proton mixed fields and the neutron response functions of the spectrometer were obtained by calculations and experiments up to 200 MeV.     

Recent advances in neutron reflectivity studies of biological membranes

Biological membranes are critical living interfaces which not only compartmentalise cells but also provide specific surfaces on which biochemical reactions take place. Their study is essential for our understanding of life and disease and also for the development of new pharmaceuticals. Because they are dynamic structures reliant on the surrounding aqueous phase for their activity, techniques which can probe them at a molecular scale under physiological conditions are crucial to understand their function. Here, I describe some of the recent developments in neutron reflectivity in this research area and suggest where future developments in the technology might be usefully directed.     

Structural and dynamic single chain behaviour in a binary blend of low molecular mass poly(siloxanes) as studied by small angle neutron scattering and neutron spin echo spectroscopy

Elastic and quasi elastic neutron scattering investigations, using the small angle neutron scattering (SANS) and neutron spin echo (NSE) techniques, respectively, were performed in order to study the static and dynamic single chain behaviour in a binary blend of low molecular mass deuterated poly(dimethylsiloxane) (d-PDMS) and protonated poly(ethylmethylsiloxane) (p-PEMS) at the critical composition _c. Since the single chain observation requires that only a small amount of one of both components is labelled, the d-PDMS/p-PEMS system was modified in such a way that the major part of the protonated PEMS component was replaced by the corresponding deuterated material. Although the de-mixing of the PEMS isotopes occurs far below the de-mixing of the PDMS/PEMS system the resulting chemically binary d-PDMS/d-PEMS/p-PEMS blend with the volume composition 0.5/0.425/0.075 is strictly speaking a ternary system. This complication had to be taken into account, in particular with respect to the correct evaluation of the SANS data.The careful analysis of the SANS curves allows one to determine all three thermodynamic interaction parameters with reasonable reliability and gives evidence that the radii of gyration agree with those, which were determined in corresponding isotopic PDMS and PEMS blends. This is in contrast to the observation on real binary PDMS/PEMS blends at _c, where the collective conformational properties exhibit a considerable chain expansion. The NSE data of the ternary system follow completely the predictions of the Rouse model, which describes the dynamics of a dense low molecular mass polymeric system in a single chain approximation. The experimental observations are also in contrast to the results of former NSE measurements on binary PDMS/PEMS blends, where a transition from Rouse behaviour at short times to a much weaker relaxation at longer times became obvious.The results of the static and dynamic single chain behaviour presented here confirm the results of a computer simulation on a low molecular mass binary blend at the critical concentration, where explicitly the pure single chain behaviour was probed and no indications for chain expansion and deviations from the Rouse dynamics were found.Dedicated to Prof. Dr. Erhard W. Fischer on the occasion of the 75th anniversary of his birthday.     

Risk assessment of inhalation exposure for airborne toxic metals using instrumental neutron activation analysis

In order to study the effects of air pollution, about 1,300 samples of airborne particulate matter (APM) were collected at suburban and industrial sites, in Daejeon, Korea from 1998 to 2006. The concentrations of carcinogenic (As and Cr) and non-carcinogenic metals (Al, Mn, and Zn) were determined by using instrumental neutron activation analysis (INAA). These long-term metal concentration data were applied to a risk assessment of inhalation exposure using Monte Carlo analysis (MCA).     

Study of the nuclear recoil response of a NaI(Tl) scintillator detector with a Cf neutron source

This paper describes the behavior of the scintillation pulses induced in a NaI(Tl) crystal scintillator under excitation of a ²⁵²Cf neutron source and a ¹³⁷Cs gamma source and the possible identification of the incident particle by the study of the pulse shape. Furthermore, the energy dependence of the mean decay time is presented.     

Rapid one-step derivatization of Se(VI) to a piazselenol for the spectrofluorimetric determination of selenium in biological material

A spectrofluorimetric method for the determination of total selenium in biological samples has been developed. After oxidative destruction, the sample is reacted with a mixture of bromide and 2,3-diamino-1,4-dibromonaphthalene (Br₂-DAN) without pH adjustment. Selenium(VI) is rapidly reduced by bromide to Se(IV) which then forms 4,7-dibromo-5,6-benzopiazselenol (Br₂-DAN-Se). The conversion of Se(VI) to Br₂-DAN-Se is completed in 6 min at 100°C. The piazselenol is extracted to cyclohexane and the fluorescence measured at 577 nm with excitation at 518 nm. The procedure has been validated by determinations on reference materials with selenium concentrations ranging from 4 to 1460 ng g⁻¹. The advantages of the method are the fast reduction of Se(VI) by hydrobromic acid and the properties of Br₂-DAN, which permit the piazselenol formation to be carried out in a strongly acidic medium and at high temperature. The limit of detection is 0.6 ng g⁻¹ as estimated by three times the standard deviation of the blank determination (n = 7).

The rate of reduction of Se(VI) to Se(IV) in hydrobromic acid was investigated as a function of concentration and temperature. The new kinetic data together with previous kinetic and equilibrium data for the piazselenol formation were used to model and optimize the simultaneous reduction-derivatization procedure.     

Challenges in determining perchlorate in biological tissues and fluids: implications for characterizing perchlorate exposure

The ability to measure environmental contaminants in biological tissues and fluids is important in the characterization of exposure. However, the analysis of certain contaminants in these matrices presents significant challenges. Perchlorate (ClO₄⁻) has emerged as a potential contaminant of concern primarily in drinking water and also in contaminated food. Significant advances have been made in the analysis of perchlorate in environmental matrices (water, soil) by ion chromatography (IC). In contrast, the analysis of perchlorate in extracts of biological tissues and fluids (vegetation, organs, milk, blood, urine, etc.) presents several challenges including small sample sizes, extracts with high matrix conductivity, and co-elution of other ions during IC analysis. To be able to detect low concentrations of perchlorate in biological samples, interferences must be removed or minimized, such as through the use of preparative chromatography cleanup techniques and/or alternative analytical methods less susceptible to common interferences (preconcentration or mass spectrometric detection). We present discussion and examples of the challenges encountered in the analysis of tissue extracts and fluids for perchlorate by IC and how some of those analytical challenges have been overcome.     

Metrological assessment of the high-accuracy RNAA method for determination of cobalt in biological materials

The paper summarizes work on the development of the high-accuracy RNAA method for the determination of trace amounts of cobalt in biological materials. The method is based on a combination of neutron activation with selective and quantitative isolation of the analyte in a state of high radiochemical purity by use of column chromatography followed by gamma-ray spectrometric measurements. The method was devised according to a set of rules, which were formulated to obtain high accuracy of the method. The procedure has been also equipped with several criteria as key factors in quality assurance. Qualification of the high-accuracy RNAA method as a primary ratio method has been demonstrated and its usefulness in the certification of the candidate reference materials tea leaves and mixed Polish herbs is presented.     

Solid solubilities of (La Nd,)2(Zr,Ti)2O7 phases deduced by neutron diffraction

Time-of-flight powder neutron diffraction has been performed on oxides with composition (La_1−xNd_x)₂Zr₂O₇ and Nd₂(Zr_1−xTi_x)₂O₇, where x=0, 0.2, 0.4,…1.0, in order to determine the solid solution behaviour across each series. Between La₂Zr₂O₇ and Nd₂Zr₂O₇, a cubic pyrochlore phase is observed (, Z=8). A linear decrease in the lattice parameter from 10.8047 to 10.6758 Å indicates complete miscibility of the two end-members. For the same series, the 48f oxygen x-parameter increases from 0.3313 to 0.3348, suggesting increased distortion of the 6 coordinate B sites and reduced distortion of the 8 coordinate A sites. There is limited solubility of Nd₂Ti₂O₇ in Nd₂Zr₂O₇. Exsolution of a monoclinic phase (P2₁, Z=8) rich in Nd₂Ti₂O₇ is observed at approximately x=0.56. The compositional range over which a solid solution exists is more extensive than that which has been previously reported. The solubility of Nd₂Zr₂O₇ in Nd₂Ti₂O₇ is very low.     

Synthesis of novel ferrocene containing vic-dioxime ligands and their Ni(II), Cu(II) and Co(II) complexes: Spectral, electrochemical and biological activity studies

Two new vic-dioxime ligands bearing an important redox-active substituent, anti-β-ferrocenylethylaminoglyoxime (1a) and anti-β-ferrocenylethylaminophenylglyoxime (1b), have been synthesized, and their Ni(II), Cu(II) and Co(II) (2a-4a, 2b-4b) complexes were obtained. The composition and structure of the products were determined by elemental analysis, Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis), mass spectrometry (MS), one-dimensional (1D) ¹H, ¹³C NMR, and two-dimensional (2D) heteronuclear multiple bond correlation (HMBC) techniques. The redox behaviors of the ligands and their complexes were investigated by cyclic voltammetry (CV), which revealed that all the ferrocenyl redox centers are electrochemically independent and undergo a quasi-reversible oxidation at similar potentials. Also, antibacterial activity was studied against Staphylococcus aureus ATCC 29213, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. The antimicrobial test results indicated that all the compounds have mild levels of antibacterial activity against both gram negative and gram-positive bacterial species.     

Synthesis,characterization, semi-empirical study and biological activities of homobimetallic complexes of tranexamic acid with organotin(IV)

The Schiff base has been synthesized by reacting tranexamic acid with indol-3-carboxyaldehyde in the first step and then with carbon disulfide at room temperature in the second step. The homobimetallic complexes have been synthesized by reaction of Schiff base with R₂SnCl₂ and R₃SnCl in 1?:?2?M ratio under stirring, where R?=?methyl, n-butyl and phenyl. The ligand and complexes have been characterized by elemental analysis, FT-IR, multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn) and semi-empirical study. IR data reveal the bidentate nature of the ligand. Five- or six-coordinate geometry was confirmed in solution by NMR spectroscopy. The homobimetallic complexes and ligand were tested in vitro against some pathogenic bacteria and fungi to assess their antimicrobial properties. The complexes show biological activities with few exceptions.     

Structural studies and biological evaluation of Co (II), Ni (II) and Cu (II) complexes of carbohydrazone derived from ethyl acetoacetate in addition to crystallographic description of La (III) or Sm (III) catalytic activity abnormal product

New carbohydrazone ligand derived from the condensation of carbohydrazide and ethyl acetoacetate, diethyl 3,3′‐(carbonylbis (hydrazin‐2‐yl‐1‐ylidene))(3E,3′E)‐dibutyrate (H₄EBC), and its divalent Co, Ni and Cu chelates have been isolated and characterized utilizing convenient methods. ¹H‐NMR spectrum of H₄EBC revealed the abundance of the enol isomer in solution, which was the opposite to what was shown by the solid IR. This was supported by comparing the theoretical IR of both keto and enol forms. In [Ni(H₄EBC)Cl₂(H₂O)]·2H₂O, H₄EBC acts as a neutral NON tridentate ligand via the (C=O)_carbonyl oxygen atom besides the two (C=N)_azomethine nitrogen atoms, while in [Co(H₄EBC)Cl₂(2H₂O)]·2H₂O, H₄EBC behaves as a neutral NN bidentate ligand through the two azomethine groups. Magnetic measurements inherent to their electronic spectra show that both Ni (II) and Co (II) chelates have octahedron coordination frameworks. On the other hand, the ligand behaves as a binegative tetradentate in [Cu₂(H₄EBC)Cl₂]·H₂O via the deprotonated (C=O)_carbonyl groups of the ethyl acetoacetate framework and the two (C=N)_azomethine groups. In the latter complex, the carbonyl group of the carbohydrazide moiety is converted to hydroxyl group. Cu (II) complex has a tetrahedral geometry according to ESR and electronic spectral data. The reaction of H₄EBC with SmCl₃·6H₂O or LnCl₃·7H₂O gave single crystals of abnormal product (C₁₆H₁₆N₄O₄). The packing diagram of this crystal has a chain structure. The photoluminescence spectra of [Cu ₂ (H ₄ EBC)Cl ₂ ]·H ₂ O , [Co(H ₄ EBC)Cl ₂ (H ₂ O) ₂ ]·2H ₂ O and [Ni(H ₄ EBC)Cl ₂ (H ₂ O)]·2H ₂ O display emission broad‐bands at 342, 321 and 337 nm, respectively. The microbial behavior of the synthesized moieties was investigated against various bacterial and fungal strains. [Cu₂(H₄EBC)Cl₂]·H₂O complex shows the same activity as ampicillin towards Escherichia coli and Staphylococcus aureus with inhibition zones of 26 and 22 mm, respectively. Antioxidant activity is determined using bleomycin‐dependent DNA damage assay besides erythrocyte hemolysis. Finally, in vitro cytotoxic activities against two different cell lines have been examined.     

Near-infrared spectroscopy (NIRS) reflectance technology for the determination of tocopherols in alfalfa

The vitamin E (α- and (β+γ)-tocopherol) contents present in alfalfa (fresh or dehydrated) were analysed using near-infrared spectroscopy (NIRS) technology together with a remote reflectance fibre-optic probe. The range of vitamin E was 0.55–5.16 mg/100 g for α-tocopherol and 0.07–0.48 for (β+γ)-tocopherol. The regression method employed was modified partial least squares (MPLS). The equations developed using the fibre-optic probe for 69 samples of alfalfa (dehydrated and fresh) to determine the content of vitamin E in feeds had multiple correlation coefficients (RSQs) and prediction corrected standard errors (SEP (C)) of 0.946 and 0.321 mg/100 g for α-tocopherol and 0.956 and 0.022 mg/100 g for (β+γ)-tocopherol. The predicted values of vitamin E in feeds using NIRS technology applying the fibre-optic probe directly on the sample with neither previous treatment nor manipulation are comparable to those obtained using the chemical method, which included alkaline hydrolysis and hexane extraction of the vitamin from the unsaponifiable fraction before chromatographic determination.     

Synthesis, characterisation and biological activity of gold(III) catecholate and related complexes

The reactions of the cyclometallated gold(III) complexes [LAuCl₂] [L=2-(dimethylaminomethyl)phenyl, 2-benzylpyridyl or 2-anilinopyridyl] with catechol, tetrachlorocatechol, or the cyclic α,β-diketone SCH(CO2Et)C(O)C(O)CH(CO2Et) give stable complexes containing five-membered Au-O-C-C-O rings. These represent the first examples of well-characterised gold(III) catecholate complexes. Similarly, reactions with 2-acetamidophenol [HOC₆H₄NHC(O)CH₃] give complexes with the related AuNCCO ring. The complexes were characterised by NMR spectroscopy, electrospray ionisation mass spectrometry, elemental microanalysis, and in the case of the complex [(2-benzylpyridyl)Au{OC₆H₄NC(O)CH₃}] by an X-ray crystal structure determination. Several complexes show high activity towards P388 murine leukemia cells.     

Determination of boron and lithium in diverse biological matrices using neutron activation-mass spectrometry (NA-MS)

Summary Essential features of the neutron activation-mass Spectrometry (NA-MS) technique are described. Applicability of this technique for the simultaneous determination of boron and lithium is demonstrated for a diverse group of biomaterials. NA-MS is a nondestructive analytical technique, and dynamic in nature since its coverage extends to a broad range of concentration levels. Contamination after the irradiation step, extraneous by natural lithium or boron is inconsequential, since only the activation products are the analyted assayed. Coupling the nuclear activation phenomenon which generates ⁴He and ³He (from ¹⁰B and ⁶Li, respectively), with the high precision potential of mass spectrometry forms the bases of this technique. Under ideal conditions the detection limit is extendable to pg g^–1 concentration ranges and therefore, it is extremely well suited to investigate the natural concentration levels of boron and lithium in biomaterials. The potential of this method for the determination of lithium in biomedical trace element research is of special significance since determination of sub-ppb levels of lithium by other analytical techniques faces serious analytical difficulties mainly due to contamination control and in some cases to insufficiently low detection limits.     

Synthesis,spectral characterization,electrochemical and biological studies of Co(II), Ni(II) and Cu(II) complexes with thiocarbohydrazone

A series of metal complexes of Co(II), Ni(II) and Cu(II) have been synthesized with the Schiff base derived from thiocarbohydrazide and 8-formyl-7-hydroxy-4-methylcoumarin. The structures of the complexes have been proposed by elemental analyses, molar conductance, spectral (IR, UV-Vis, ESR and FAB-mass), magnetic, thermal and electrochemical studies. These complexes are soluble in DMF and DMSO and molar conductance values indicate that they are non-electrolytes. Elemental analyses of the complexes confirm stoichiometry ML ·; 2H₂O [M=Co(II), Ni(II) and Cu(II)]. Spectroscopic studies indicate coordination occurs through phenolic oxygen after deprotonation and nitrogen of azomethine. The Schiff base and its complexes have also been screened for antibacterial (Escherichia coli, Streptococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and cladosporium) by the MIC method. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties.     

HRTEM and neutron diffraction study of LixMo5O17: From the ribbon (x=5) structure to the rock salt (x=12) structure

Structure determination of the fully intercalated phase Li₁₂Mo₅O₁₇ and of the deintercalated oxide Li₅Mo₅O₁₇ has been carried out by electron microscopy and neutron powder diffraction. The reversible topotactic transformation between the ordered rock salt structure of the former and the ribbon structure of the latter (closely related to that of Li₄Mo₅O₁₇) is explained on the following basis: both structures can be described as strips built up as an assembly of infinite ribbons of MoO₆ octahedra that are five octahedra thick, and that differ by slight displacements of the octahedral ribbons. We show that the electrochemical behavior of the Li_xMo₅O₁₇ system is based on two sorts of Li⁺ sites; those that are located within the strips between the ribbons, and those that are located at the border of the strips. The high rate of Li intercalation in this oxide and its reversibility are discussed in terms of its peculiar structure.