On the determination of thermal ionization energy of deep centers from ESR data

It is shown that the skin effect due to thermal generation of free carriers may affect the ESR signal more than deep center depopulation. Experimental results for 0.33 eV deep Eu²⁺ donor in CdF₂ crystals are presented, to show the way in which the thermal energy of deep centers is deduced from the ESR data.     

Photovoltaic cells based on nickel phthalocyanine and zinc oxide formed by atomic layer deposition

The introduction of an ultrathin zinc oxide (ZnO) layer formed by the atomic layer deposition (ALD) technique was found to improve the operation parameters of nickel phthalocyanine (NiPc) based photovoltaic cells with a transparent bottom electrode, indium tin oxide (ITO). This improvement is attributed to several reasons, such as I) increase of photovoltaic yield in ITO/p-NiPc/n-ZnO/Al cells incorporating a hybrid heterojunction as compared to single-layer ITO/NiPc/Al cells, II) enhancement of the overall spectral response in the double-layer cells and III) extension of long-term operational stability.     

Photo-enhancement of space-charge-limited currents (SCLC) under pressure

Abstract

Photo-enhanced SCLC (j_ph) have been studied as a function of pressure (p) in anthracene crystal. The plots of the trap-filling ratio θ (p) and characteristic trap parameter 1 (p) are derived from the measurements and the latter compared with theoretical one derived from pressure modification of intermolecular distances in molecular crystals. The application of an average, isotropic compressibility is questioned and local high-value compressibilities are postulated to explain the results.     

Unilateral Versus Bilateral Injections of Botulinum Toxin in Patients with Adductor Spasmodic Dysphonia

Both unilateral and bilateral thyroarytenoid muscle injections of Botox provide effective management of voice symptoms in patients with adductor spasmodic dysphonia; however, the preferred injection technique has not been established. In this study, 16 patients were treated with unilateral injections (72 injections total) and 33 patients were managed with bilateral injections (133 injections total). Individual assignments to injection type were based on treatment previously received and dose was adjusted according to the patient's previous treatment response. An optimal treatment included a benefit lasting 3 months or more with side effects lasting 2 weeks or less. Compared to patients receiving bilateral injections, those receiving unilateral injections more frequently noted a benefit of 3 months or more (p = 0.03), side effects of 2 weeks or less duration (p = 0.03), as well as both a 3-month benefit and a 2-week or less side effect (p = 0.0004). Injection type had no effect on optimal Botox dosing with repeat injections. Successive unilateral injections at the same dose were more likely (p = 0.012) than successive bilateral injections to produce the same or longer duration of benefit. We conclude that a unilateral injection routine has a more optimal and consistent treatment effect/side effect profile.     

Structural transitions in N-isopropylcarbazole single crystal monitored by pressure-induced luminescence

Abstract

Phase diagram for solid-solid transitions in N-isopropyl-carbazole single crystal is determined by monitroing pressure-induced-luminescence (PIL) pulses appearing at transition points. A comparison of the data obtained from PIL and from microcalorimetric measurements shows remarkable difference in the transition temperature at ambient pressure and enormous discrepancy in the transition enthalpy. These discrepances are discussed in terms of local strains influence on parameters of phase transitions.     

SIR Estimation in Hexagonal Cellular Networks with Best Server Policy

The evaluation of the Signal to Interference Ratio (SIR) in cellular networks is of primary importance for network dimensioning. For static studies, which evaluate cell capacity and coverage, as well as for dynamic studies, which consider arrivals and departures of mobile stations (MS), the SIR is always an important input. Contrary to most of the analytical works evaluating SIR, we assume in this paper that the MS is attached to the best server, i.e., to the base station (BS) from which it receives the highest power. This is a more realistic policy compared to the classical one that considers MSs to be attached to the nearest BS. The exact formulation of the SIR is however in this case uneasy to handle and numerical methods remain heavy. In this paper, we thus propose an approximate analytical study on the average SIR and SIR distribution in lognormally shadowed networks based on truncated lognormal distributions that provides very close results with respect to Monte Carlo simulations.     

ODMR investigations of recombination processes in ZnSe:Cu

New ODMR signals have been observed in ZnSe:Cu crystals by monitoring the Cu-green, Cu-red and the i.r. emissions. The results are interpreted in terms of direct D-A recombination involving Cu_Zn and Cu-X centres and indirect recombination via excited states of these centres.     

The photo-ESR studies of CdF2: Eu thermoluminescence processes

A model explaining the thermoluminescence (TL) in CdF₂: Eu is presented. We show that the energy barriers resulting from lattice relaxation govern the electron release and capture processes responsible for TL.     

Generation of charge carrier pairs in tetracene layers

The mechanism of negative and positive charge carrier generation by light absorption in tetracene layers has been studied. We conclude that there are different processes determining electron and hole production. Positive charge carriers are produced without recombination while the negative charge carrier generation depends strongly on the recombination process. The experimental data for charge carrier generation in tetracene layers are treated theoretically taking into account photogeneration, recombination of charge carriers, trapping and transport processes inside the sample.