The plasticity of the Cu(H2O) 6 2+ Jahn-Teller complex affected by lattice strains and cooperative interactions

The EPR spectra evolution of Cs₂Zn_1?x Cu_x(ZrF₆)₂ · 6H₂O (x=0.01, 0.6, 0.8, and 1.0) in the temperature range 4.2–330 K and the x-ray structure analysis of the compound with x=1.0 in the range 150–327 K show that the Jahn-Teller (JT) complex Cu(H₂O)₆ coordination sphere undergoes a plastic deformation. The observed effect is due to the combined influence of small lattice strains existing in the paraphase and a new one appearing as a result of a ferroelastic phase transition and increasing with decreasing temperature below T _c . It is proved that both cooperative interactions between JT complexes and ferroelastic strain stabilize a certain JT configuration. The problem of instability of a JT configuration compressed at T ～ 265 K is discussed.     

Probe measurements in a discharge with liquid nonmetallic electrodes in air at atmospheric pressure

Discharges with liquid nonmetallic electrodes of much interest for applications are investigated. It is found that a dc discharge between two streams of tap water in air at atmospheric pressure is stable at a currentof 40≤I≤100 mA. The discharge exists in the diffuse (volume) form with a relatively low current density (∼0.2 A/cm²) and a high (above one kilovolt) voltage drop across the air gap (∼1 cm) between the water electrodes. The current density and voltage depend only slightly on the discharge current. Probe measurements show that three regions can be distinguished in the discharge: two electrode regions (1–2 mm in length) and a discharge column with a constant electric field of ≈0.8 kV/cm (i.e., E/N≈20 Td, because the gas in the discharge is heated up to 1500–2000 K). The average electric field strength near the electrodes is E≈2–3×10³ V/cm (E/N≈60–80 Td). The charged particle density in the column is n ∼ 10¹² cm⁻³. The probe measurements of n agree with the previous microwave absorption measurements. The water vapor concentration in the column is also estimated from probe measurements.     

Resummation of the jet broadening in DIS

We calculate the leading and next-to-leading logarithmic resummed distribution for the jet broadening in deep inelastic scattering, as well as the power correction for both the distribution and mean value. A truncation of the answer at NLL accuracy, as is standard, leads to unphysical divergences. We discuss their origin and show how the problem can be resolved. We then examine DIS specific procedures for matching to fixed order calculations and compare our results to the data. One of the tools developed for the comparison is an NLO parton distribution evolution code. When compared to PDF sets from MRST and CTEQ it reveals limited discrepancies in both. Received: 16 October 2001 / Published online: 12 April 2002     

Gluon jets from quarkonia

A detailed analysis is made within perturbative QCD of the decays into gluon jets of P-wave and S-wave quarkonia (J^PC = 0⁺⁺, 1⁺⁺, 2⁺⁺, 1^+? and 0^?+, 1^??). For all those states we compute to leading non-trivial order in α_s the conventional fraction f(?, δ) of the jet-like hadronic final states, characterized by the back-to-back cone of half angle δ, in which all but a small fraction ? of the total energy is emitted. To the same order we give also the average values of thrust momenta and spherocity distributions.     

Diffusion from sessile droplets through membranes

We analyze diffusion from a periodic array of hemispherical droplets through a membrane. We find that the multiple sources do not interact strongly, even when the droplets are closely spaced, so that the flux through the membrane appears nearly additive.     

Advances in micro-perforated panel absorbers

Theoretical and experimental investigations on the performance of micro-perforated -panel absorbers are reviewed in this paper. By reviewing recent research work, this paper reveals a relationship between the maximum absorption coefficient and the limit of the absorption frequency bandwidth. It has been demonstrated that the absorption frequency bandwidth can be extended up to 3 or 4 octaves as the diameters of the micro-holes decrease. This has become possible with the development of the technologies for manufacturing micro-perforated panels, such as laser drilling, powder metallurgy, welded meshing and electro-etching to form micrometer order holes. In this paper, absorption characteristics of such absorbers in random fields and in high sound intensity are discussed both theoretically and experimentally. A new absorbing structure based on micro-perforated-panel absorbers demonstrate experimentally high sound absorption capability. This review shows that the micro-perforated-panel absorber has potentials to be one of ideal absorbing materials in the 21st century.