EXAFS study of local atomic order about iodine in thyroxine,rat, human and sheep thyroids

Radioactive ¹²⁵I emits short‐range Auger electrons and represents a human health risk when incorporated in thyroglobulin of the thyroid. Quantitative evaluation of this risk can only be realised if local atomic order about iodine in the thyroid is known. Here, extended X‐ray absorption fine structure (EXAFS) has been used to probe the local structure about iodine in pure thyroid hormone, thyroxine. These data are consistent with a model where iodine is bound to a single iodinated carbon ring linked to an oxygen atom, similar to a previously published model for monoiodotyrosine, a major iodinated residue in thyroglobulin. Several structural models for the local environment of iodine from rat, human and sheep have been tested and these data are found to be compatible with a slightly modified environment with respect to that found for thyroxine. The best‐fit models include the following three components: (i) iodine covalently bonded to a tyrosine ring, as found for thyroxine; (ii) iodine bonded quasi‐covalently to a carbonyl ligand in partially filled (50%) sites; (iii) partially filled sites (50–40%) of carbonyl ligands, with oxygen at van der Waals distances from iodine. Advantages of using Fourier‐filtered EXAFS for complex crystal structures are discussed.     

Determination of free iodine concentration in an X-ray contrast agent

Based on the analysis of the absorption spectra of solutions of iodine in ethanol, we propose a simple and sensitive (at a level of 1 μg/g) method for determination of the concentration of free (not bound to polymer) iodine in substances synthesized from ether oils and iodine. The method uses absorption of molecular iodine in the UV region. Iodine dissolved in alcohols has a rather large absorption cross section in the UV region. These absorption bands can be used to detect very small quantities of iodine. It is shown that, for iodine concentrations in the 1–50 μg/g range, the intensity of absorption band at a wavelength of 359 nm depends linearly on the iodine concentration, which allows one to use this band to determine the concentration of iodine not bound with the polymer in the X-ray contrast material.     

REVIEW: Iodine Determination by Inductively Coupled Plasma Spectrometry

Abstract

Iodine is a chemical element with critical physiological roles and its determination using instrumental analysis is not trivial. Inductively coupled plasma spectrometry associated with either optical emission (ICP-OES) or mass spectrometry (ICP-MS) may be employed, but each alternative presents limitations considering iodine behavior in argon plasma and the occurrence of interferences. Sample preparation is also a critical issue when using sample introduction by pneumatic nebulization due to memory effects. This critical review discusses the literature dealing with sample preparation followed by ICP-OES or ICP-MS for iodine determination in a plethora of samples. It is shown that the best figures of merit may be reached using sample preparation in alkaline medium followed by ICP-MS measurements.     

Determination of bromine and iodine in powder samples by spectra in the vacuum region

Methods for the introduction of nonconducting powder samples containing halogens into the corona of a low-voltage pulsed discharge in a vacuum are considered. It is shown that the spectra of the halogens can be obtained by using double layer pellets. Using the resonance lines in the spark spectra of bromine and iodine in the analysis enabled one to determine contents of down to 0.5 microgram which in combination with a preliminary enrichment corresponds to a relative sensitivity of 5 · 10^–5%.     

Effect of composition on properties of reactive Al·B·I2 powders prepared by mechanical milling

Metal-based fuels producing halogen-containing combustion products are being developed to enable rapid inactivation of harmful aerosolized spores and bacteria. Ternary reactive materials containing aluminum, boron, and iodine were prepared by mechanical milling with systematically varied Al:B ratio. The aluminum mass fraction varied from 0% to 70%, and most materials included 20 wt% of iodine. Prepared powders were inspected by electron microscopy; particle size distributions were measured using low angle laser light scattering. Stability of materials was studied using thermo-gravimetry and differential scanning calorimetry. As-prepared as well as pre-heated and quenched samples were analyzed using x-ray diffraction. Iodine was released upon heating in several stages. Low-temperature iodine release was relatively small. It overlapped with decomposition of B(OH)₃ releasing water. The most significant amounts of iodine were released when the samples were heated to 400–500 °C, when AlB₂ formed. Both AlB₂ formation and iodine release were further accelerated by melting of aluminum. For the boron-rich samples, in which boron remained after all aluminum was used to form AlB₂, an additional, high-temperature iodine release stage was observed near 900 °C. The results show that both boron and aluminum are capable of stabilizing substantial quantities of iodine in the metal matrix. The iodine is released at temperatures much greater than its boiling point. The mechanism by which iodine is retained in boron and aluminum remains unclear.     

On the possibility of writing thin amplitude-phase holograms in the near infrared range (λ=1315 nm) using polyimide-based fullerene-containing conjugated organic structures

The process of writing thin amplitude-phase holograms in polyimide-based fullerene-containing conjugated organic media using an iodine laser operating at λ=1315 nm was studied. It is shown that such polymeric structures are promising media for reversible optical data recording in the IR spectral range.     

A closed cycle iodine laser

It is shown that the energy decrease resulting from repeated shots with the same gas filling of an iodine laser is solely due to the accumulation of I₂ and the consumption of iodide. A closed cycle iodine laser is presented in which the molecular iodine is removed by cooling, and in which the iodide content is kept constant by means of the vapour pressure of a liquid supply.     

Energy loss straggling in collisions of fast finite-size ions with atoms

The influence of ion size on straggling of energy losses by fast partially stripped ions is studied using the nonperturbative approach based on the eikonal approximation. It is shown that such a consideration of collisions of ions with complex atoms can lead to considerable corrections in calculating root-mean-square straggling of energy losses by fast ions compared to the results obtained for point ions. The root-mean-square straggling of energy losses are calculated for bromide and iodine ions in collisions with copper, silver, and aluminum atoms. It is shown that allowance for the size of the electron “coat” of an ion noticeably improves the agreement with experimental data.     

On the determination of the statistical characteristics of the magnesium acceptor in GaN

The temperature dependence of the free hole concentration is studied in Ga:Mg samples grown by the MOCVD technique. Relevant parameters are determined, like the ionization energy, the degree of compensation and the concentrations of donors and acceptors. Methods for the determination of these parameters are discussed. It is shown that reliable data on the ionization energy and the compensation can be obtained while determination of the concentrations of donors and acceptors is much less reliable. The value of the degeneracy factor of the acceptor level is explored since it influences the degree of compensation and the free carrier concentration. The occurrence of the maximum in the free carrier concentration with the increase of Mg dopand concentration in MOCVD samples is examined. It is shown that multicharged donors are needed for the explanation, among which the complex formed by magnesium atom and the nitrogen vacancy is the plausible candidate.     

A re-interpretation of the LEED structures formed by iodine on W(l10)

The early work done by Avery on the adsorption of I₂ on W(110) has been re-interpreted using adatom models originally developed for the Cl₂/Br₂/I₂/Fe (100) systems. The experimental coverages and LEED patterns are described precisely using variable, non-coincident nets of halogen atoms. It is shown that the movement of spots within the diffraction pattern arises from the movements of iodine atoms along simple crystallographic directions. The model assumes repulsive lateral interactions between iodine adatoms which is consistent with the desorption behaviour. The reasons for structural changes within the adlayer are discussed using the model, and the internuclear spacings and geometry of the adlayer are shown to be consistent with previous work on Fe(100) and W(100).     

On-surface radical addition of triply iodinated monomers on Au(111)—the influence of monomer size and thermal post-processing

In the present study on-surface polymerisation of aromatic iodinated precursor molecules through radical addition is studied by scanning tunneling microscopy (STM) on Au(111) under ultra-high vacuum (UHV) conditions. Comparison of the two analogous monomers s-triiodobenzene and s-triiodophenylbenzene with similar symmetry and functionalization but differently sized organic backbones aimed to study the influence of monomer size on the morphology of resulting covalent networks. In contrast to previous studies on brominated monomers, here the reaction by-product, i.e., the split-off iodine atoms, was found to adsorb stably on Au(111) in ordered structures. The influence of post-processing by thermal annealing on both the covalent networks and the iodine structures was studied for different temperatures. DFT calculations were applied to evaluate formation energies of commonly observed topological defects and related to their experimental probability of occurrence.     

电感耦合等离子体-质谱法快速测定尿中的碘

在优化的仪器条件下,以In作内标,采用电感耦合等离子体-质谱法（ICP-MS）测定尿中碘元素.样品经稀释离心后直接上机测定.该方法线性范围为宽、灵敏度高、重现性好、线性相关系数为0.99997、回收率为95.3％-98.1％、精密度为1.15％-2.08％、用ICP-MS法和国标方法同时测定25份尿样中碘含量,结果经统计学分析,T为0.158小于2.021,P＞0.05,说明两种方法测定结果之间无显著性差异.ICP-MS方法简便快速且易于操作,适用于大批量尿样品中碘含量的测定.     

Absorption of Iodine on the Surface of Silica Modified by Polyvinylpyrrolidone and Albumin

The influence of modification of a fumed silica by polyvinylpyrrolidone (PVP) and bovine serum albumin (BSA) on its ability to adsorb iodine has been investigated by UV spectroscopy. It has been established that the adsorption of iodine molecules on the silica surface is increased several times after its modification by high-molecular compounds. The role of structural factors in complexing of iodine with macromolecules has been estimated. Using PVP and BSA as an example, it is shown that the structure of a modifying layer on the silica surface depends on the nature and structure of the polymer.     

Subject index

Lead iodide is known to dissociate under band gap illumination. We investigated the decomposition products from sintered samples by quadrupole mass spectrometry and found that neutral atomic and molecular iodine species desorb from the illuminated surface. The desorption rate was measured as a function of light intensity and surface temperature. Atomic iodine desorption seems to be thermally activated throughout the temperature range (300–500 K), while molecular iodine has that feature only up to 400 K. We performed measurements of the dark and photoconductivity of PbI₂ as functions of temperature and light intensity. Correlations of those results with the photolysis mass-spectrometric data indicate a possible model for the dissociation process. It suggests a diffusion-controlled mechanism of iodine desorption as well as of the dark conductivity, which seems to be ionic in that temperature range. The molecular iodine is apparently formed in surface sites, such as grain boundaries, which have a longer life-time for adsorbed iodine atoms as well as a dominant role in surface electronic conduction.     

Relaxation times and mean free paths of phonons in the boundary scattering regime for silicon single crystals

The phonon focusing in cubic dielectric crystals and its influence on the heat transfer in the boundary phonon scattering regime at low temperatures have been investigated. The mean free paths of phonons of different polarizations in samples of infinite and finite lengths with circular and square cross sections have been calculated in the anisotropic continuum model. For samples of infinite length with circular and square cross sections in the case of the equality of the cross-sectional areas, the angular dependences of the mean free paths normalized by the Casimir length almost completely coincide. It has been shown that the anisotropy of the mean free paths decreases significantly upon changing over from infinite samples to samples of finite length. For silicon crystals, the anisotropy of the phonon mean free paths has been analyzed for each of the branches of the phonon spectrum. It has been found that the mean free paths for phonons of each vibrational mode reach maximum values in the directions of focusing, and, in these directions, they exceed the mean free paths for phonons of the other vibrational modes.     

Thermal conductivity of selenium doped with indium and iodine in the solid and liquid states

We have measured the thermal conductivity in both the solid and liquid states for two amorphous samples. The first was selenium doped with indium and the second was selenium doped with iodine. The concentration of In and I in both samples was 50000 ppm in weight, which is equal to 3.33% for indium and 3.02% for iodine additives in atomic percent. The measurements were taken in the temperature range from 100 to 470°C and were carried out using the concentric cylindrical wall. It was found that the thermal conductivity of both samples is of the phonon type; its temperature dependence follows the relation K _ph T ^–1, and can be explained by the influence of thermal effects on the lattice structure.     

石墨炉T1I分子吸收光谱法测定地质样品中痕量碘

提出以五氧化二钒和 混合助融剂高温热解地质样品，平台石墨炉Ｔ１Ｉ分子吸收光谱法测定地质样品右痕量碘。方法简便，可靠，标准物质测定结果与推荐值吻合。     

ZnS:I单晶降阻条件的选择

本文叙述了对碘化学输运法生长的ZnS:I单晶扩散Al杂质,制备低阻ZnS:I晶体的实验方法。在制备低阻ZnS:I单晶过程中,根据晶体内含I的浓度选择热退火条件,可较重复地得到Al浓度在10-1g/g量级,电阻率在10—102Ω·cm范围的低阻ZnS单晶。讨论认为,在ZnS:I单晶退火过程中,I的存在有助于Al杂质的扩散。     

Magnetic susceptibility, heat capacity, and optical conductivity of LiPc and LiPcI

The magnetic susceptibility, using dc and electron spin resonance (ESR) methods, the specific heat, and the infrared properties of the one-dimensional molecular semiconductors lithium phthalocyanine (LiPc) and the iodinated compound LiPcI have been investigated for temperatures K. LiPc has a half-filled conduction band and is expected to be an organic metal. However, due to the strong Coulomb repulsion the system is a one-dimensional Mott-Hubbard insulator with a Hubbard gap of 0.75 eV as inferred from optical measurements. The localized electrons along the molecular stacks behave like a S = 1/2 antiferromagnetic spin chain. The spin susceptibility, as determined by ESR experiments, and the magnetic contribution to the heat capacity show a Bonner-Fisher type of behavior with an exchange constant K. LiPcI is an intrinsic narrow-gap semiconductor with an optical gap of 0.43 eV. In ESR experiments it is silent, indicating that all the unpaired electrons have been removed from the macrocycle via doping with iodine. Received: 16 June 1998 / Accepted: 14 July 1998     

Theoretical study of a new energy extraction scheme of a chemically pumped pulsed iodine laser amplifier

A new energy extraction scheme of a chemically pumped pulsed large-scale iodine laser based on a high-pressure pulsed singlet oxygen generator is proposed. In previous investigations only low-pressure oxygen generators have been considered. Since they require a high iodine density for an efficient amplifier operation, the lifetime of the stored energy is correspondingly small and thus only small-sized iodine amplifiers appear to be technically feasible. We found, however, that when the singlet oxygen is generated at high-pressure, the iodine density required can be considerably reduced so that the lifetime of the stored energy becomes sufficiently long to fill up large amplifier cells. A numerical model is developed and the extractable energy is theoretically estimated. It is shown that 0.2J/1·pass can be extracted when an input pulse of 20 ns duration (FWHM) and 1 J/cm² fluence is fed into the amplifying medium.