Energetics and vibrational states for hydrogen on Pt(111)

We present a combination of theoretical calculations and experiments for the low-lying vibrational excitations of H and D atoms adsorbed on the Pt(111) surface. The vibrational band states are calculated based on the full three-dimensional adiabatic potential energy surface obtained from first-principles calculations. For coverages less than three quarters of a monolayer, the observed experimental high-resolution electron peaks at 31 and 68 meV are in excellent agreement with the theoretical transitions between selected bands. Our results convincingly demonstrate the need to go beyond the local harmonic oscillator picture to understand the dynamics of this system.     

Determination of oxycodone hydrochloride in oral solutions by high-performance thin-layer chromatography/densitometry

A thin-layer chromatography/densitometry method was developed and validated for the determination of oxycodone hydrochloride in oral solutions by using silica gel plates. A horizontal technique was used for development of the plates. The optimum composition for the mobile phase, which provided a suitable Rf value of 0.6 for oxycodone, was propanol-acetic acid-water-25% ammonia-methanol (20 + 1 + 1 + 3 + 10). Detection was at 234 nm. Oxycodone hydrochloride was stable on the sorbent and was precisely and accurately measured in the range of 0.3-1.5 microg/band.     

X-ray study on the effect of moisture on the crystalline state of cellulose

A method is presented for measuring the change of the intensity of x-ray diffraction peaks of cellulose specimens as a consequence of humidity changes of the specimens. Measurements performed showed a decrease of this intensity after drying pulp specimens initially kept in humid air. Thus the order in cellulose decreased during drying.     

Weakly nonlinear model for oscillatory instability in Saturn's dense rings

Viscous overstability (oscillatory instability) may play an important role in the formation of small scale structure in dense planetary rings such as Saturn's B ring. We investigate the growth and saturation of such modes in local particle simulations. Starting from a hydrodynamic model, we develop a set of ordinary differential equations to model the evolution of the amplitudes of the linearly overstable modes in the nonlinear regime. The NASA/ESA space probe Cassini can make direct observations of these modes in Saturn's rings, including their sizes and temporal development.     

LR-CAHSQC: an application of a Carr-Purcell-Meiboom-Gill-type sequence to heteronuclear multiple bond correlation spectroscopy

A new pulse sequence, long-range CPMG-adjusted heteronuclear single quantum coherence (LR-CAHSQC), is proposed for the determination of long-range JCH coupling constants from a long-range 1H-13C correlation experiment. The long-range heteronuclear coupling constants can be directly extracted from COSY-type antiphase peak patterns. The current approach utilizes CPMG-sequences for polarization transfer, and thus avoids the evolution of homonuclear JHH couplings, which normally may introduce abnormalities into the cross peak pattern. The differences between LR-CAHSQC and normal LR-HSQC are discussed.     

High-performance thin-layer chromatography method for assessment of the quality of combinatorial libraries,and comparison with liquid chromatography-ultraviolet-mass spectrometry

A high-performance thin-layer chromatography (HPTLC) method was developed for fast evaluation of the purity of solid-phase synthesis products. The results obtained were in good agreement with results obtained by the LC-MS method (r(2) = 0.8404) or by the LC-UV method (r(2) = 0.8053), confirming the suitability of HPTLC for purity analysis of combinatorial syntheses. The synthesis products can be quantified and identified by measuring UV densitograms or in situ UV spectra or by ESI-MS after isolation of the zone of interest. A new, simple, and fast method for transferring the zone of the analyte from the plate to the ESI-MS equipment is described. The new HPTLC method enables rapid and efficient analysis of approximately 40 samples in parallel. As such, it offers a cheaper and easier way to analyze the purity of synthesis products than the commonly used LC-UV-MS.     

Measurement of Homonuclear J-Couplings from Spin-State Selective Double-/Zero-Quantum Two-Dimensional NMR Spectra

¹H-detected two-dimensional double-/zero-quantum experiments are described for measurement of homonuclear ²J_HH-couplings of NH₂ or CH₂ groups in proteins. These experiments utilize multiple-quantum coherence for determination of the size and the absolute sign of the geminal scalar and dipolar couplings in the presence of broad lines. Spectra are simplified by gradient selection and spin-state selective filters.     

Editorial

JPC – Journal of Planar Chromatography – Modern TLC -     

Multi-objective optimization by technical laws and heuristics

Common design principles apply to design of mechanical and biological machine structures. Most of the main properties of machines and creatures are determined by programmed genetics. These determine the geometry, material selection, functioning of machines and biological creatures and the fitness for service. The present approach of innovation and optimum design is based on basic mechanics with fuzzy goal formulations and heuristics, like axiomatic design. These models are combined synergistically to formulate the desired properties of the machines. First, engineering mechanics and heuristics are shown to have a finalistic guidance on the conceptual design of optimal fluid conveying channels consisting of a branch and a closing device. Then a multi-objective algorithm is tested in an industrial case study design of a preloaded screw fastened flange plate and it is shown to be a reliable tool for testing and innovating new solutions. The goals and constraints are modellled consistently by the same goal function form. The joints have to be reliable against risks of separation, relaxation, fatigue and creep fracture due to pressure differences. Compared to conventional results it gives nearly the same technical and safety functions even at half the cost. This approach is useful for optimizing new concepts and also existing machine designs showing possibilities for notable cost savings.     

A Storage Process with Local Time Input

In this paper we introduce a storage process with singular continuous input. The input process is defined as the local time of a stationary reflecting Brownian motion with drift. Many basic charateristics of the process are computed explicitly, e.g., stationary distribution, distributions of the starting and ending time of on-going busy and idle periods. We also consider the multifractal spectrum of the input process and observe that it is independent of system parameters.