The effect of pressure on the formation of alkali metal borate ion pairs at 25°C

Pressure dependent UV-visible spectrophotometric measurements were used to determine \(\Delta \bar V^ * \) and \(\Delta \bar \kappa ^ * \) for the formation of alkali metal borate ion pairs. The association constant for each ion pair was measured at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. The pressure dependence of the apparent association constants, K _A (P)/K _A (1), have been fitted to $$[RT/(P - 1)]ln[K_A (P)]/[K_A (1)] = - \Delta \bar V^0 + \Delta \bar \kappa ^0 [(P - 1)/2]$$ to determine \(\Delta \bar V^0 and \Delta \bar \kappa ^0 \) . The \(\Delta \bar V^0 \) for the alkali metal borate ion pairs range from 5–9 cm³-mol^?1. The association constants were also measured as a function of ionic strength at 1 atm. Extrapolation to I=0 yielded K _A of 2.12, 0.66, 0.76 and 1.12 for [LiB(OH)₄], [KB(OH)₄], [RbB(OH)₄] and [CsB(OH)₄], respectively. The trend generally indicates less ion pairing and a smaller volume change for the ion pair formation as the size of the cation increases. The concept of localized hydrolysis is used to explain the trend observed in the equilibrium constant of the ion pair as the cation size is changed.     

Photoemission and energy loss spectroscopy on semiconductor surfaces

The application of multiple experimental techniques to silicon surface studies is discussed. Two specific cases are considered: the chemisorption of oxygen on silicon at coverages up to one monolayer and the intrinsic surface states on cleaved and on annealed Si (111) surfaces. It is shown that by combining electron energy loss spectroscopy and ultraviolet photoemission spectroscopy, one can obtain an approximate energy level model for both occupied and unoccupied states     

Calculations of the giant dipole resonance for sd-shell nuclei in the open-shell random phase approximation

The systematics of the giant dipole resonance have been calculated in the open-shell RPA for all the self-conjugate sd-shell nuclei, using (i) a phenomenological Rosenfeld interaction, (ii) Barret, Hewitt and McCarthy G-matrix elements and (iii) Kuo G-matrix elements. The excitations are based on shell model ground states for all nuclei except ²⁸Si for which a projected Hartree-Fock ground state was used.     

Hydrogen adsorption and surface structures of silicon

The adsorption of atomic hydrogen on silicon (111)2 × 1 cleaved, (111) 7 × 7, and (100) 2 × 1 surfaces has been studied by using electron energy loss spectrscopy (ELS) and Photoemission spectroscopy (UPS). On all surfaces the hydrogen removes the “dangling bond” surface state and a new peak in the density of states at lower energies corresponding to the SiH bond is found. The LEED pattern of the equilibrium surfaces (111) 7 × 7 and (100) 2 × 1 is not altered by hydrogen adsorption, while on the cleaved (111) 2 × 1 surface the fractional order spots are extinguished. The Haneman surface-buckling model therefore provides an explanation for the surface reconstruction of the cleaved (111) 2 × 1 surfaces. For the equilibrium surfaces, (111) 7 × 7 and the (100) 2 × 1, the data are consistent with the Lander-Phillips model.     

Vectorial Approach to Fast Correlation Attacks

A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy     

On the Motion of a Dynamic System with Minimal Dissipation

The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail.     

Waves with random coupling and random propagation constants

We study the mathematical treatment of transmission statistics of coupled wave devices with random imperfections. Such devices include multi-mode waveguides or optical fibers, directional couplers at waveguide or optical frequencies, dominant-wave transmission lines (with the reflected wave the spurious mode), lumped filters composed of circuit or of waveguide elements, multi-layer optical coatings to achieve high or low reflectivity.If the random parameters have very rapid spatial variations, we assume they have white spectra. Exact results for transmission statistics are obtained in such cases. These exact results can be extended to random parameters with almost-white spectra, and narrow-band spectra that are far from white.These calculations are carried out in a simple way by using Kronecker matrix products.     

Giant piezoresistance effects in silicon nanowires and microwires

The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of depleted silicon nano- and microstructures. The resistance is shown to vary strongly with time due to electron and hole trapping at the sample surfaces independent of the applied stress. Importantly, this time-varying resistance manifests itself as an apparent giant PZR identical to that reported elsewhere. By modulating the applied stress in time, the true PZR of the structures is found to be comparable with that of bulk silicon.     

General Relativity in the Making, 1916–1918: Rudolf J. Humm in Göttingen and Berlin

Mathematische Semesterberichte - In 1916, the Swiss student Rudolf J. Humm arrived in Göttingen to study relativity theory under Hilbert. He enrolled in his courses, attended Klein’s...