Density functional study of chlorine–oxygen compounds related to the ClO self-reaction

Geometrical parameters, vibrational frequencies, relative stabilities, and dissociation energies of the three stable Cl₂O₂ isomers and the OClO and ClOO radicals were investigated by density functional theory (DFT). The present analysis shows that DFT using hybrid functionals is capable of describing these systems to at least the same degree of accuracy as ab initio methods. The average absolute bond-length deviation of ClClO₂, ClOOCl, and ClO₂ from experimental results is 0.024/0.027 Å, with a maximum deviation for the dichlorine peroxide O(SINGLE BOND)O bond equal to 0.072/0.063 Å, for the B3PW91 and B3LYP functionals, respectively. The average absolute bond-angle deviation for the hybrid functionals is 0.8°. Harmonic vibrational frequencies calculated with DFT give for all Cl(SINGLE BOND)O compounds good agreement with experiments. The dissociation energies of ClOOCl, OClO, and ClOO were found to be in good agreement with experiments, the average error being less than 1.2 kcal/mol. The two isomers chloryl chloride (ClClO₂) and dichlorine peroxide (ClOOCl) were found to be approximately 9 kcal/mol more stable than the chlorine chlorite (ClOClO) isomer. The ClOO isomer is predicted to be 3.0 kcal/mol more stable than OClO, in accordance with the experimental value of 4 kcal/mol. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 203–217, 1998     

A rotating phantom for the study of flow effects in MR imaging

A common type of phantom used for the study of flow effects in MR imaging is the tube phantom, where a liquid passes through a set of tubes placed in the main magnetic field of an MR scanner. Among the disadvantages with this type of phantom are that a distribution of velocities is present in each tube, and that quantifications of flow effects using tube phantoms may be very time-consuming. In this work, we describe the design and the properties of a rotating wheel flow phantom used for quantification of the effects of flow through the imaging plane as well as in the imaging plane. The proposed phantom is constructed as a rotating gel-filled wheel, surrounded by static volumes filled with the same gel, and the evaluation of the information from rotating and static parts is made with a specially designed computer program. The phantom can be used as a plug flow phantom covering simultaneously an interchangeable velocity interval, which at present has the range −52 mm/s, +52 mm/s. It is shown that the phantom gives adequate information on the dependence of pixel content on first-order motion in MR modulus and phase images. Among the fields of application are rapid calibration of MR imaging units for flow determination using phase information, as well as testing of pulse sequence characteristics and verification of theoretical predictions concerning the flow dependence in MR images.     

Comment on “Piezonuclear decay of thorium” [Phys. Lett. A 373 (2009) 1956]

Subjecting a solution of ²²⁸Th to ultrasound (20 kHz, 100 W), Cardone et al. [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956] claim to observe an increase in the transformation or decay rate of ²²⁸Th by a factor of 10⁴. The evidence provided seems however far from conclusive and in part contradictory to the claims made. In fact, looking at the presented data we find it cannot be taken as justification to discard the null hypothesis, namely, that the data from exposed and non-exposed samples are drawn from the same distribution. We suggest a number of additional tests that should be made in order to improve the quality of the study and test the hypothesis of so-called piezonuclear reactions.     

Sliding plate rheometry of planar oriented concentrated fiber suspension

The rheology of concentrated planar fiber suspensions is investigated. A new experimental technique for fiber suspensions based on a sliding plate rheometer incorporating a shear stress transducer is developed. It is shown that this instrument works well for the tested material systems. The rheological behavior in steady shear is subsequently investigated. The results can be largely explained by a combination of frictional and hydrodynamic interaction. Despite this evidence of friction no yield stress could be detected for the investigated shear rates. It was also found that the fiber aspect ratio did not influence the steady shear viscosity.     

A framework for valuing corporate securities

We suggest a methodology for valuing corporate securities that allows the straightforward derivation of closed form solutions for complex scenarios. The tractability of the framework stems from its modularity-we provide a number of intuitive building blocks that are sufficient for valuation in typical situations. A further advantage of our approach is that it makes economic interpretation far easier than what is typically possible with other approaches, such as solving systems of partial differential equations. As examples we consider a corporate coupon bond with discrete payments, and debt subject to strategic debt service.     

Progress in neutron diagnostics at JET

In the ITER tokamak, diagnosing the plasma neutron emission will be essential to characterise fusion burning process and determine the performance of the machine. JET, currently the world largest tokamak, is the most suitable test bed for development of the fusion-relevant neutron diagnostics due to its plasma parameters and unique tritium operation capability. Current works aim at improving the spatial and spectral characteristics of the neutron measurements at JET, as well as on technological tasks. The present enhancements of neutron diagnostics and data analyses at JET make-together with new fast particle measuring techniques and tritium retention studies-part of the “burning plasma” diagnostic developments towards reactor-grade fusion facilities.     

Field-induced local magnetic moments in γ (FCC) Fe–Ni anti-Invar alloys

Mössbauer spectroscopy in longitudinal external fields (up to 7 T) and SQUID magnetometry (up to 5 T) measurements have been carried out on mechanically alloyed (MA) γ (FCC) Fe_100−xNi_x (x=21, 24, and 27 at%) alloys at room temperature. The zero-field Mössbauer spectra of these alloys show only singlets. The high field Mössbauer results indicate that large amounts of the material is in the paramagnetic state, giving rise to two spectral components with their effective fields almost linearly depend on the external field, but with slopes that are smaller than unity. The in-field Mössbauer spectra of the x=27 at% alloy show an additional component with a hyperfine field of ≈21 T, which is attributed to Ni-rich (>30 at% Ni) clusters (domains) of ferromagnetically ordered HM phase that behaves superparamagnetically at room temperature and shows a non-linear character in the magnetization (M–H) curves at low fields. This HM phase is also present in the x=21 and 24 at% samples but with smaller amounts. The results suggest induced hyperfine fields and hence induced moments in the paramagnetic components, which increases with increasing Ni contents. Taenite-enriched samples from the metal particles of two stony meteorites, Al Kidirate (H6) and New Halfa (L4), are also studied by high field Mössbauer spectroscopy and the results are compared to that of MA samples.     

MRI measurements of the dependence on T1 of the echo amplitudes using a multiple spin-echo scheme

Analytical calculations using the Bloch formalism were performed to assess the dependence on T₁ of the echo amplitudes for the Phase-Alternating Phase-Shift (PHAPS) multiple spin-echo protocol. Measurements in a 0.5 T MR imaging unit were performed to ratify the analytical results. especially for low T₂ values, the echo amplitudes were erroneous, with an increasing contribution from stimulated echo components with increasing T₁. Apart from affecting T₂ estimates, stimulated echoes generated a non-monoexponential signal decay of the echo trains. The results confirmed previous simulation studies as regards the dependence on T₁ of T₂ estimates from PHAPS.     

Comparison of neutron emission spectra for D and DT plasmas with auxiliary heating

The DT experimental campaign on JET (1997) represents a major step forward for neutron emission spectroscopy (NES) diagnostic through the high quality data collected by the Magnetic Proton Recoil (MPR) spectrometer. These data for different DT plasma heating scenarios were analyzed here to determine the underlying fuel ion populations which in turn were used to project the 2.5-MeV neutron emission spectra for deuterium plasmas. The results on neutron spectra for DT and D plasmas in the same conditions were compared in order to determine the plasma information that could be expected from NES diagnosis of D plasmas and the instrumental characteristics that would be required. Future NES experiments would make dual sight line observations possible and the added diagnostic value is also assessed based on the present results.