New technique for the determination of trace elements using multiparameter coincidence spectrometry

Multiparameter coincidence g-ray spectrometry based on g-g coincidence is widely used in the field of nuclear structure studies, and has produced many succesful results. In this paper, feasibility of the method for neutron activation analysis of trace elements was studied. Particularly, a long-lived radioisotope ¹²⁹I (T_1/2 = 1.57^.10⁷ y) in algae samples and iridium in geological samples has been determined.     

Vibration analysis and non-destructive testing with real-time shearography

Real-time laser speckle shearography coupled with vibration stressing is shown to be an effective means of vibration analysis and non-destructive testing. The shearograms are modulated by a system of live fringes. These fringes are shown to be described by the zeroth-order Bessel function of the first kind and their visibility decreases with increasing fringe order. In vibration analysis, the instantaneous fringe pattern depicts the out-of-plane surface displacement gradient of the object surface at various resonance modes. In non-destructive testing, the flaw depth in a component can be determined without having to determine fringe orders. There is good agreement between the results obtained using the method and those from theory and time-average holography. A major advantage of real-time shearography is its facility for continuous assessment of a vibrating object without the need for secondary shearogram reconstruction.     

Time delay and integration imaging for internal profile inspection

A time delay and integration imaging technique is presented and applied to internal surface contour measurement. Using the proposed optical arrangement, inspection of profiles of objects which are mounted on the internal surface of a hollow cylinder can be carried out. Tests conducted on objects with diameters ranging from 40 to 214 mm show good agreement with results obtained from conventional profilometer.     

Electrochemical polymerization of aniline monomers infiltrated into well-ordered truncated eggshell structures of polyelectrolyte multilayers

The use of nanosphere lithography to construct two-dimensional arrays of polystyrene (PS) particles coated with multilayered polyelectrolyte (PE) shells and truncated eggshell structures composed of PE thin layers is reported. The truncated eggshell PE structures were produced by extraction of the PS particle cores with toluene. The core-extraction process ruptures the apex of the PE coating and causes a slight expansion of the PE thin layers. Aniline hydrochloride was infiltrated into the PE shells and subsequently electropolymerized to yield an array of a composite containing polyaniline (PAni) and PE thin shells. Voltammetric, quartz crystal microbalance, and reflectance Fourier transform infrared spectroscopic measurements indicate that aniline monomers were confined within the thin PE shells and the electropolymerization occurred in the interior of the PE shell. The PE thickness governs the amount of infiltrated monomer and the ultimate loading of the PAni in the truncated eggshell structure. Surface-structure imaging by atomic force microscopy and scanning electron microscopy, carried out after each step of the fabrication process, shows the influence of the PE thickness on the organization and dimensions of the arrays. Thus, the PE thin shells composed of different layers can function as nanometer-sized vessels for the entrapment of charged species for further construction of composite materials and surface modifications. This approach affords a new avenue for the synthesis of new materials that combine the unique properties of conductive polymers and the controllability of template-directed surface reactions.     

Mechanism of antimicrobial activity of CdTe quantum dots

The antimicrobial activity and mechanism of CdTe quantum dots (QDs) against Escherichia coli were investigated in this report. Colony-forming capability assay and atomic force microscopy (AFM) images show that the QDs can effectively kill the bacteria in a concentration-dependent manner. Results of photoluminescence spectrophotometry, confocal microscopy, and antioxidative response tests indicate that the QDs bind with bacteria and impair the functions of a cell's antioxidative system, including down-regulations of antioxidative genes and decreases of antioxidative enzymes activities. The oxidative damage of protein and lipid is also observed with thiobarbituric reacting substances and protein carbonyl assays, respectively. On the basis of these results, it is proposed that the mechanism of the antimicrobial activity of CdTe QDs involves QDs-bacteria association and a reactive oxygen species-mediated pathway. Thus, CdTe QDs could have the potential to be formulated as a novel antimicrobial material with excellent optical properties.     

Development of multiple prompt gamma-ray analysis

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq)+NaL⁺(nb)⇔ML⁺(nb)+Na⁺(aq) taking place in the two-phase water-nitrobenzene system [M⁺=Li⁺, K⁺, Rb⁺, Cs⁺; L = p-tert-butylcalix[4]arene-tetrakis (N, N-dimethylthioacetamide); aq = aqueous phase, nb = nitrobenzene phase] were evaluated. Furthermore, the stability constants of the ML⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Cs⁺<Rb⁺<K⁺<Li⁺<Na⁺.     

Reduction of Compton background from hydrogen in prompt gamma-ray analysis by multiple photon detection

Low-energy photons produced by the Compton scattering from hydrogen increase the background in the lower-energy region of the gamma-ray spectrum. This results in an increase in the detection limit for trace elements. In multiple photon detection prompt gamma-ray analysis (MPGA), only those elements that simultaneously emit two or more prompt gamma-rays, which have cascade relation and are emitted within a short interval, can be measured. Therefore, the influence of hydrogen can be reduced. In this study, standard polymer and food samples are measured. The hydrogen background is reduced in MPGA.     

A variation of the Andrews–Stanley partition function and two interesting q-series identities

The Ramanujan Journal - In this paper we present a new formula for the number of unrestricted partitions of n. We do this by introducing a correspondence between the number of unrestrited...     

Hydrogen bond‐directed self‐assembly of peripherally modified cyclotriphosphazenes with a homeotropic liquid crystalline phase

The synthesis and characterization of hydrogen‐bonded star‐shaped complexes consisting of stilbazolyloxy, azopyridyl, and Schiff base‐substituted cyclotriphosphazenes ( 3a , 3b , and 3c , respectively) and monoalkyloxy, bis(dodecyloxy), and tris(dodecyloxy)benzoic acids are reported. The thermal behaviors of complexes are studied by the means of differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffractometry. Only 3a and 3b with monoalkyloxybenzoic acids show a homeotropic smectic A mesophase. The effect of azo and ethylene linkage of mesogenic groups in the cyclotriphosphazenes and the length of the flexible chain in monoalkyloxybenzoic acids on mesophase transition behaviors are investigated, revealing that the linkages in mesogenic groups governs the phase transition temperatures, and the length of flexible chain in proton donors plays an important role in controlling the magnitude of enthalpy and entropy of mesophase transitions in this supramolecular liquid crystal system. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4691–4703, 2008