Markov processes in single molecule fluorescence

This article examines the current status of Markov processes in single molecule fluorescence. For molecular dynamics to be described by a Markov process, the Markov process must include all states involved in the dynamics and the first-passage time (FPT) distributions out of those states must be describable by a simple exponential law. The observation of non-exponential FPT distributions or other evidence of non-Markovian dynamics is common in single molecule studies and offers an opportunity to expand the Markov model to include new dynamics or states that improve understanding of the system.     

Measurement of the proton structure functionF2 from the 1993 HERA data

The ZEUS detector has been used to measure the proton structure functionF ₂. During 1993 HERA collided 26.7 GeV electrons on 820 GeV protons. The data sample corresponds to an integrated luminosity of 0.54 pb^–1, representing a twenty fold increase in statistics compared to that of 1992. Results are presented for 7Q ²<>⁴ GeV² andx values as low as 3×10^–4. The rapid rise inF ₂ asx decreases observed previously is now studied in greater detail and persists forQ ² values up to 500 GeV².supported by Worldlab, Lausanne, Switzerland     

Optical phonons in millerite (NiS) from single‐crystal polarized Raman spectroscopy

Although several fundamental physico‐chemical aspects of nickel sulfides have been studied in detail, particularly for millerite (nickel(II) monosulfide), the most common nickel sulfide mineral, no satisfactory investigation of optical vibrational modes has been reported previously. In this paper, we provide a definitive assignment of the optical phonons in millerite, investigated by polarized Raman spectroscopy on an oriented single crystal. The impact of the power of the incident laser beam on the spectra has also been investigated, revealing evidence for degradation in the quality of the spectra at sufficiently high laser power. Copyright © 2008 John Wiley & Sons, Ltd.     

Measurement of the proton structure function F 2 at low x and low Q 2 at HERA

We report on a measurement of the proton structure functionF ₂ in the range 3.5×10⁻⁵≤x≤4×10⁻³ and 1.5 GeV²≤Q ²≤15GeV² at theep collider HERA operating at a centre-of-mass energy of √s=300GeV. The rise ofF ₂ with decreasingx observed in the previous HERA measurements persists in this lowerx andQ ² range. TheQ ² evolution ofF ₂, even at the lowestQ ² andx measured, is consistent with perturbative QCD. supported by EU HCM contract ERB-CHRX-CT93-0376     

Experimental investigations of liquid flow in pipe with flat internal baffles

Liquid flow in a tubular reactor with flat internal baffles of various widths was investigated. On the basis of the laser Doppler anemometry (LDA) measurements, the main flow parameters, i.e. the mean and fluctuating velocity components and turbulent kinetic energy (TKE) were determined. The investigations demonstrated that the insertion of baffles into a pipe and a change in their width caused a generation of liquid stream whirls, induced liquid recirculation loops and intensified the flow considerably. The results can be useful in describing turbulent flow in tubular reactors with baffles and in optimising their design.