Functionalized pyrolytic highly oriented graphite polymer film for surface‐assisted laser desorption/ionization mass spectrometry in environmental analysis

The pyrolytic highly oriented graphite polymer film (PGS) was first employed to analyze low‐mass analytes in environmental analysis by surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS). PGS is a synthetic uniform and highly oriented graphite polymer film with high thermal anisotropic conductivity. We have found that negative ion mode SALDI‐MS using oxidized PGS (PGS‐SALDI‐MS) can be used to detect [M–H]^? ions from perfluorooctanoic acid (PFOA) and other perfluoroalkylcarboxylic acids when the PGS surface is modified with the cationic polymer polyethyleneimine (PEI). The signal intensity of PFOA when employing the PEI modification showed a ten‐fold increase over that obtained from desorption/ionization on porous silicon (DIOS). PFOA was quantified using PGS‐SALDI‐MS and the calibration curve showed a wide linear dynamic range of response (20–1000 ppb). The combination of atmospheric pressure ionization and PGS (AP‐PGS‐SALDI) showed greater signal intensity than vacuum PGS‐SALDI for deprotonated PFOA. Several other environmentally important chemicals, including perfluoroalkylsulfonic acid, pentachlorophenol, bisphenol A, 4‐hydroxy‐2‐chlorobiphenyl, and benzo[a]pyrene, were also successfully used to evaluate PGS‐SALDI‐MS. In addition, we found that nonafluoro‐1‐butanesulfonic acid was able to produce protonated peptides in positive ion PGS‐SALDI‐MS, but that perfluoropentanoic acid and trifluoroacetic acid were not. It is suggested that perfluoroalkylsulfonic acids are better protonating agents than perfluoroalkylcarboxylic acids in SALDI‐MS. Copyright © 2009 John Wiley & Sons, Ltd.     

Aragonite twinning in gastropod nacre

Aragonite twinning in gastropod nacre has been investigated using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM) with the focused ion beam (FIB) sample preparation technique. At the growth front of nacre, Haliotis discus hannai and Omphalius rusticus form a “stack-of-coins” structures, which consist of pseudo-hexagonal and elliptical aragonite tablets, respectively. SEM, EBSD, and TEM analyses revealed that these tablets are monolithic single crystal and almost free of the {1 1 0} twins that are common in aragonite of biotic or abiotic origin. The longest diagonal of the hexagon and the longer axis of the ellipse are parallel to the a-axis of aragonite. The crystal orientation of each tablet in a stack, measured by TEM-Kikuchi pattern analysis, is almost the same but there is occasionally {1 1 0} twin-like relationship between adjacent tablets along the stacking. On the other hand, the fibrous aragonite layer formed prior to the nacreous structure is composed of polycrystalline aragonite with high density of {1 1 0} twins. TEM observation suggests that the interlamellar organic sheet prevents the inheritance of the twins, by selecting only single domain of the twins, through the mineral bridge.     

Theβ + decay of the new isotope86Mo and the first observation of86m Nb

Theβ ⁺ decay of⁸⁶Mo has been firstly investigated by means ofβγ spectroscopy. The⁸⁶Mo nuclei were produced by fusion-evaporation reactions of⁵⁴ Fe (³⁵Cl, 1 p2n) and⁵⁸Ni (³²S,2p 2n) at beam energies of 103 and 120 MeV, respectively. Threeγ rays of 47.3, 49.8 and 187.0 keV were unambiguously identified to follow theβ ⁺ decay of⁸⁶Mo by results ofXγ andβγ coincidence and cross-bombardment. A half life and a maximumβ ⁺-ray energy of⁸⁶Mo were determined to be 19.6±1.1 s and 3.9±0.4 MeV, respectively. A decay scheme of⁸⁶Mo is proposed in this article. Furthermore, a decay of⁸⁶Nb has been studied using the same combinations of projectiles and targets, and a newβ-decaying isomer^86m Nb was observed with a half life of 56.3±8.3 s.     

Determination of methylarsenic compounds in airborne particulate matter by gas chromatography with atomic absorption spectrometry

A sensitive method is described for the determination of mono-, di- and tri-methylarsenic compounds in airborne particulate matter by hydride-generation and gas-liquid chromatography with atomic absorption spectrometric detection. Interferences of various species are discussed. Absolute detection limits are 70, 80 and 100 pg As, respectively for the mono-, di- and tri-methylarsenic species. Recoveries of methylarsenic compounds added to airborne particulate matter are almost 100%. An iron/nitrate mixture interfered strongly but this was overcome by adding EDTA.     

A second-order method for unconstrained optimization

This paper presents a quadratically converging algorithm for unconstrained minimization. All the accumulation points that it constructs satisfy second-order necessary conditions of optimality. Thus, it avoids second-order saddle andinflection points, an essential feature for a method to be used in minimizing the modified Lagrangians in multiplier methods.The work of the first author was supported by NSF RANN AEN 73-07732-A02 and JSEP Contract No. F44620-71-C-0087; the work of the second author was supported by NSF Grant No. GK-37672 and the ARO Contract No. DAHCO4-730C-0025.     

Reduction of Chandrasekhar's planetary problem in the case of a specularly reflecting boundary to the standard problem

The reduction of Chandrasekhar's planetary problem to the standard problem has been made by several authors (cf. Chandrasekhar⁽¹⁾; Sobolev;⁽²⁾Van de Hulst;⁽³⁾Coulsonet al.; ⁽⁴⁾Ueno; ⁽⁵⁾Kagiwada and Kalaba;⁽⁶⁾. However, the diffuse reflection and transmission problem in a finite anisotropically scattering atmosphere bounded by a specular reflector has not been reduced to the standard problem. In the present paper, starting with an integral equation governing the source function for Chandrasekhar's planetary problem in the case of a specular reflector, we show how to express the required scattering and transmission functions in terms of the Chandrasekhar's scattering and transmission functions. So far as we know, the reduction formulae are new. They will be useful for the numerical study of Chandrasekhar's planetary problem in the case of a specular reflector with the aid of high-speed digital computer.     

Synthesis and physical properties of 6,12-diarylazuleno[1,2-b]azulenes

The structure of a minor dimer ($\text{2a}$) of 1-arylcycloheptatrienylidenethylene was determined by X-ray crystallography. Dehydration of $\text{2a}$ and $\text{2b}$ gave novel non-benzenoid aromatics---6,12-diarylazuleno[1,2-b]azulenes ($\text{3a}$ and $\text{3b}$), whose electronic and NMR spectral properties were reported.     

Optical absorption of Cu-centers in CdCl2 and CdBr2 single crystals

The absorption spectra of CdCl₂ and CdBr₂ single crystals doped with cuprous or cupric halides were measured. Optical bleaching of the absorption bands due to Cu⁺ gives rise to new absorption bands which suggest the conversion of Cu⁺→Cu²⁺. This was confirmed also by detecting the growth in ESR signals characteristic of Cu²⁺ centers.