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.
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 γ-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.
The TOTEM experiment at LHC Baechler, J.; Antchev, G.; Aspell, P. ...
2011 IEEE Nuclear Science Symposium Conference Record,
2011-Oct.
Conference Proceeding
The TOTEM experiment is dedicated to the measurement of the total proton-proton cross-section with the luminosity-independent method and the study of elastic and diffractive scattering processes. Two ...tracking telescopes, T1 and T2, integrated in the CMS detector, cover the pseudo-rapidity region between 3.1 and 6.5 on both sides of the interaction point IP5. The Roman Pot (RP) stations are located at distances of ± 147m and ± 220 m with respect to the interaction point to measure the very forward scattered protons at very small angles. During the LHC technical stop in winter 2010/2011, the TOTEM experiment was completed with the installation of the T1 telescope and the RP stations at ± 147 m. In 2011, the LHC machine provided special optics with the large ß* = 90 m, allowing TOTEM to measure the elastic scattering differential cross section, down to the four-momentum transfer squared |t| = 2×10 -2 GeV 2 . Using the optical theorem and extrapolation of the differential cross section to t = 0 (optical point), the total p-p cross section at the LHC energy of √v = 7 TeV could be computed for the first time. The status of the experiment, the performance of the detectors with emphasis on the RPs are described and the first physics results are presented.
We have performed
O and
Cu NMR measurements in YBa
Cu
(δ ≈ 0.15) oriented powder samples at CuO
plane sites Cu(2) and 0(2, 3) in the temperature range 10-300 K. The temperature dependent Knight shift ...K(T) and spin lattice relaxation rate T
-(T) of O(2, 3) yield K
T = const in accordance with the presence of free carriers at plane oxygen sites. A sharp decrease of T
of Cu(2) below 120 K is associated with the opening of a gap in the spectrum of antiferromagnetic spin fluctuations of localized copper 3 d
electrons. The comparison of different temperature dependences of spin densities at the Cu and O sites shows the presence of two nearly independent spin systems. A close similarity of YBa
Cu
a with heavy fermion superconductors is discussed.
Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at \(\sqrt{s} = 7 \) TeV in special runs with the Roman Pot detectors placed as close to ...the outgoing beam as seven times the transverse beam size. The differential cross-section measurements are reported in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be (98.3 +- 0.2(stat) +- 2.8(syst)) mb.
A new acceleration–deceleration (AD) method for reducing and focusing ion kinetic energies in matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry ...(MALDI-FTICR) mass spectrometry has been developed. The aim of the method is to equalize and then reduce the initial kinetic energy of the MALDI-produced ions, distributed over a broad energy range, by means of delayed acceleration and deceleration of the ions. The focusing of the energy results in a more efficient trapping of high mass ions and, at the same time, improves the precision of mass measurements in the ICR trap. The experimental parameters for the acceleration–deceleration ion kinetic energy focusing were predicted by means of the SIMION 3D software, incorporating both the electric and magnetic fields. The deceleration of ions both outside and inside the ICR trap was studied. The theoretical treatment shows that by applying the acceleration–deceleration method it is possible to focus the initially high kinetic energies of 100,000 Da ions into a 1 eV range and register their mass spectrum at low trapping potentials. In order to put the new method into practice, the existing FTICR mass spectrometer was equipped with a MALDI source inside the magnet. To compare the acceleration– deceleration method with other methods, the optimal mass spectrum measurement conditions for several proteomic biopolymers were studied. By means of the acceleration–deceleration method, the MALDI-FTICR mass spectrum of substance P (protonated mass 1347.736 Da) was registered at 3 × 10−8 mbar with mass resolution close to 70,000. A resolution of 45,000 was achieved by the gated trapping method. Bovine insulin B-chain (protonated mass 3494.65 Da) was used to compare the gated trapping method with the deceleration and acceleration–deceleration methods (which also include the gated trapping method as an essential part) at different matrix-to-analyte ratios. The acceleration–deceleration method does not reject high energy ions and has therefore inherently high sensitivity particularly at low analyte concentration. Bovine insulin (protonated mass 5732.6 Da) is so far the highest mass ion registered in our spectrometer. It was possible to measure this ion only by the acceleration–deceleration method.
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