Double diffractive cross-section measurement in the forward region at the LHC

The first double diffractive cross-section measurement in the very forward region has been carried out by the TOTEM experiment at the LHC with a center-of-mass energy of sqrt[s]=7  TeV. By utilizing the very forward TOTEM tracking detectors T1 and T2, which extend up to |η|=6.5, a clean sample of double diffractive pp events was extracted. From these events, we determined the cross section σDD=(116±25)  μb for events where both diffractive systems have 4.7<|η|min<6.5.

Luminosity-independent measurement of the proton-proton total cross section at √s=8 TeV

The TOTEM collaboration has measured the proton-proton total cross section at √s=8 TeV using a luminosity-independent method. In LHC fills with dedicated beam optics, the Roman pots have been inserted very close to the beam allowing the detection of ~90% of the nuclear elastic scattering events. Simultaneously the inelastic scattering rate has been measured by the T1 and T2 telescopes. By applying the optical theorem, the total proton-proton cross section of (101.7±2.9) mb has been determined, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: σ(el)=(27.1±1.4) mb; σ(inel)=(74.7±1.7) mb.

Separation of the rotational contribution in fluorescence correlation experiments

The theory of fluorescence correlation spectroscopy is reexamined with the aim of separating the contribution of rotational diffusion. Under constant excitation, fluorescence correlation experiments are characterized by three polarizations: one of the incident beam and two of the two photon detectors. A set of experiments of different polarizations is proposed for study. From the results of the experiments the isotropic factor of the fluorescence intensity correlation functions can be determined, which is independent of the rotational motion of the sample molecule. This function can be used to represent each fluorescence intensity correlation function as the product of the isotropic and the rotational factors. The theory is illustrated by an experiment in which rotational diffusion of porcine pancreatic lipase labeled with Texas Red was observed Texas Red is a label that allows precise fluorescence correlation experiments even in the nanosecond time range.

1D and 2D MAS NMR spectra of a dipolar-coupled homonuclear spin-(1/2) pair

An analytical approach based on the average Hamiltonian theory is proposed for efficient calculation of the MAS NMR spectra of a dipolar-coupled homonuclear spin-(1/2) pair. For this purpose a superoperator formalism is developed which allows one to describe the spectra over a broad span of sample spinning rates, including the exact rotational resonances. This formalism can also be applied to the description of 2D polarization exchange spectra, which in many cases turns out to be useful for measuring the coupling strength. The experimental MAS NMR and the 2D spectra of doubly 13C-labeled zinc acetate were found to be in good agreement with the calculated spectra. Copyright 1997 Academic Press. Copyright 1997Academic Press

The first international intercomparison of EPR-dosimetry with teeth: first results

Intercomparison of EPR-dosimetric techniques using tooth enamel had been performed in order to check whether the results produced by different laboratories are consistent and accurate. Participants were supposed to evaluate doses applied to pulverized enamel samples, using routine techniques from their laboratories. The intercomparison has demonstrated a great variety of methods used for dose reconstruction. Peculiarities of experimental approaches are discussed systematically in terms of procedure for recording the EPR-spectra, determination of the amplitude of the radiation induced signal, determination of the dose, and error propagation.

Paramagnetic resonance in tooth enamel created by ultraviolet light

Paramagnetic centres are present in human tooth enamel after irradiation with ultraviolet light. Their thermal stability and electron spin resonance spectrum coincide with those of the ion radicals created with gamma-rays are used in geological or archaeological dating and accident dosimetry. The long wavelength tail of their creation spectrum intersects with the short wavelength tail of the solar spectrum reaching Earth's surface, thus raising the question about the possible effect of solar irradiation on dating and dosimetry.

Temperature and frequency effects in tooth enamel electron spin resonance dosimetry

Electron spin resonance of CO3(3-) molecule ions in human tooth enamel have been studied at various temperatures between 4 and 350 K and at various microwave powers in the 9 GHz (X) band. Signal saturation during cooling due to slowing down of the electron spin relaxation has been established. The 35 GHz (Q) band spectra of tooth enamel, irradiated with various gamma-ray doses, are also presented. Q band ESR dosimetry offers some advantages over the X-band dosimetry due to signal enhancement from the spin level population difference and especially due to a better filling factor which is important when only minute quantities (a few mg) of enamel are available.

13C and 15N NMR and time-resolved fluorescence depolarization study of bovine carbonic anhydrase--4-methylbenzenesulfonamide complex

The influence of the binding of the high-affinity inhibitor, 4-methylbenzenesulfonamide, to the active site of bovine carbonic anhydrase B was studied by 15N- and 13C-NMR spectroscopy. The rotational correlation time dependence on temperature and concentration of the complex was determined by time-resolved fluorescence depolarization measurements. Our experiment provides evidence that the stoichiometry of the interaction of 4-methylbenzenesulfonamide with carbonic anhydrase B is 1:1 and the inhibitor is bound in anionic form. The 15N-NMR relaxation parameters confirm our previous conclusions about the presence of librational motions in the active site of carbonic anhydrase and indicate that the internal motion in the enzyme-inhibitor complex is more restricted than the backbone motion in the uncomplexed native enzyme.

Fluorescence correlation spectroscopy in the nanosecond time range: rotational diffusion of bovine carbonic anhydrase B

A fluorescence correlation experiment for measurement of rotational diffusion in the nanosecond time scale is described. Using this method, the rotational diffusion coefficient of bovine carbonic anhydrase B labelled with tetramethylrhodamine isothiocyanate was estimated to be Dr = (1.14 +/- 0.15) X 10(7) s-1 at 22 degrees C. The experiment is based on a cw argon ion laser, a microfluorometer with local solution flow inside the sample cell, and two photon detectors. The fluorescence intensity autocorrelation function in the nanosecond time range is computed with the help of a time-to-amplitude converter and a multichannel pulse-amplitude analyser.