Shell-by-Shell Functionalization of Inorganic Nanoparticles

The current state of the hierarchical chemical functionalization of inorganic nanoparticles (NPs) by shell-by-shell (SbS)-assembly of organic layers around the NP cores is summarized. This supramolecular functionalization concept is based on two steps: 1) the covalent grafting of a first ligand–shell consisting of, for example, long chain phosphonic acids and 2) the noncovalent interdigitation of amphiphiles forming the second ligand shell. The latter process is guaranteed predominantly by solvophobic interactions. These highly order organic–inorganic hybrid architectures are currently an emerging field at the interface of synthetic chemistry, nanotechnology, and materials science. The doubly functionalized NPs display tunable materials properties, such a controlled dispersibility and stability in various solvents, highly efficient trapping of guest molecules in between the ligand shells (water cleaning) as well as compartmentalization and modification of electronic interactions between photoactive components integrated in such complex nano-architectures. Such SbS-functionalized NPs have a high potential as water-cleaning materials and also some first prototype applications as biomedicinal therapeutics have been presented.     

Isotope ratio monitoring gas chromatography/Mass spectrometry of D/H by high temperature conversion isotope ratio mass spectrometry

Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd.     

Void formation in irradiated Nickel 270

Nickel 270 (99.98 per cent nominal purity) was irradiated in EBR-II to fluences ranging from 1 × 10¹⁸ to 1.5 × 10²² neutrons/cm² at temperatures between 375 and 525°C. Voids were observed in all specimens in concentrations of 1 to 3 × 10¹⁴/cm³, independent of temperature and fluence. At low fluences the voids were non-homogeneously distributed. These observations are interpreted in terms of void nucleation on sites existing in the material prior to irradiation. The results are compared with other observations on nickel of comparable and higher purity. Large differences exist not only in the magnitude of void concentrations but also in temperature and fluence dependencies. These differences indicate that a single, void nucleation mechanism is not operative and that impurities play an important role in determining the nature and amount of damage produced by neutron irradiation at elevated temperatures.     

The axiomatic foundations of the theory of special relativity

In this paper it is shown that (1) linear transformations more general than the Lorentz transformation—containing the Palacios and the Lorentz transformation as special cases—(2) and the principle of the constancy of the velocity of light (taken originally by Einstein together with the supposition of the linearity of transformation as fundamental hypotheses of the theory of special relativity)—can be deduced from Maxwell's equations for the electromagnetic fieldin vacuo (A ₁), the principle of relativity (A ₂) and the two following axioms (which do not contain explicitly the hypothesis of the isotropy of space!): (A ₃) to every event in the Galilean reference systemS there corresponds one and only one event in the systemS so that these two systems are connected by reversible single-valued functions, continuously differentiable as their inverse transformations, (A ₄) the constant relative velocitiesv _ss andv _ss betweenS andS are each other equal in magnitude and opposite in signv _ss =–v _ss To obtain uniquely the Lorentz transformation the following axiom has to be added: (A ₅) the distanceD of any two points at rest inS, situated in a plane orthogonal to the relative velocity betweenS andS is measuredS as independent of the sense of the velocity, i.e. if one changesv _ss into –v _ss the distanceD does not vary for an observer inS. Results of our theory are the ideas that (a) the fact that the Lorentz transformation is not the unique transformation leaving Maxwell's equations for the electromagnetic field in all Galilean systems of reference invariant but that there exists a more general transformation (containing these two transformations as special cases) leaving Maxwell's equations invariant; (b) that the Michelson-Morley as well as the Fizeau experiment does not represent an experimental proof in favour of the theory of special relativity. At the end of the paper the mutual relations between the principle of relativity (the axiomA ₁ together with the axiomA ₂), the axiomA ₅ and the possibility of the discernibility as well as the indiscernibility of right and left at the macrocosmic level is discussed.