Radiation-hardness studies of high OH content quartz fibres irradiated with 500 MeV electrons

We investigated the darkening of nine high OH⁻ fibre types irradiated with 500 MeV electrons from the Linac Injector of LEP (LIL) at CERN. The transmission of Xe light was measured in situ in the 350–800 nm range. The induced attenuation at 450 nm is typically 1.52±0.15 dB/m for a 100 Mrad absorbed dose. Two-parameter fits for darkening and recovery are presented. After irradiation the tensile strength remains essentially unchanged. For Polymicro quartz core fibres the tensile strength is typically 4.6±0.4 GPa.     

On the profile of temperature dependent series resistance in Al/Si3N4/p-Si (MIS) Schottky diodes

The temperature dependence of capacitance-voltage (C-V) and conductance-voltage (G/w-V) characteristics of metal-insulator-semiconductor (Al/Si₃N₄/p-Si) Schottky barrier diodes (SBDs) was investigated by considering series resistance effect in the temperature range of 80-300 K. It is found that in the presence of series resistance, the forward bias C-V plots exhibit a peak, and experimentally show that the peak positions with a maximum at 260 K shift toward lower voltages with increasing temperature. The C-V and (G/w-V) characteristics confirm that the interface state density (N_ss) and series resistance (R_s) of the diode are important parameters that strongly influence the electric parameters of MIS structures. The crossing of the G/w-V curves appears as an abnormality compared to the conventional behavior of ideal Schottky diode. It is thought that the presence of series resistance keeps this intersection hidden and unobservable in homogeneous Schottky diodes, but it appears in the case of inhomogeneous Schottky diode. In addition, the high frequency (C_m) and conductance (G_m/w) values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance.     

Evaluation of smear layer removal and marginal adaptation of root canal sealer after final irrigation using ethylenediaminetetraacetic,peracetic, and etidronic acids with different concentrations

The purpose of this study was to investigate the effects of different irrigation solutions on the smear layer removal and marginal adaptation of a resin‐based sealer to root canal dentine. A total of 152 instrumented roots were irrigated with the following irrigants: 9,18% etidronic acid (HEBP), 0.5, 1,2% peracetic acid (PAA), 17% ethylenediaminetetraacetic acid (EDTA), saline. The amount of smear layer was evaluated using scanning electron microscope (SEM) in seventy root samples. Eighty‐two roots were filled with AH Plus and gutta‐percha. Slices obtained from apical third of each specimen were viewed with SEM to assess marginal adaptation. Use of 9% and 18% HEBP resulted in more efficient smear layer removal in the apical third than the other chelators (p < 0.05). Higher smear layer scores in the coronal and middle thirds were obtained from 0.5%, 1% PAA groups. Regarding marginal adaptation, 18% HEBP group showed the lowest gap size values (p < 0.05), and better marginal adaptation. Etidronic acid is a promising candidate for final irrigation of root canals.     

Density functional modelling studies of chloride-substituted Schiff bases as corrosion inhibitors: Optimized geometries,atomic charges,solvent and non-linear optical effects

The anti-corrosive properties, optimized geometrical structures, atomic charges, molecular electrostatic potential (MEP) surfaces and non-linear optical (NLO) effects of some chloride-substituted Schiff bases salicylaldimine (R), N-(2-chlorophenyl)salicyaldimine (2Cl–R), N-(3-chlorophenyl)salicyaldimine (3Cl–R) and N-(4-chlorophenyl)salicyaldimine (4Cl–R) have been investigated by using density functional modelling calculations. The quantum chemical parameters, such as the highest occupied molecular orbital, the lowest unoccupied molecular orbital, gap energy and other parameters, including electronegativity, global hardness, the total charges on the whole molecules and the total energies have been calculated and discussed to obtain information about the relationships between the molecular and electronic structures of the studied inhibitors and their experimental corrosion inhibition efficiencies. The linear polarizability (α), and the firstorder hyperpolarizability (β) have been also predicted by the density functional theory (DFT) with different base sets 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) for investigating the effects of basis sets on the NLO properties.     

Occupational exposure to ionising radiation in the region of Anatolia, Turkey for the period 1995-1999

For this study, the individual annual dose information on classified workers who are occupationally exposed to extended radiation sources in Turkey, was assessed and analysed by the Ankara Nuclear Research and Training Centre dosimetry service at the Turkish Atomic Energy Authority for the years 1995-1999. The radiation workers monitored are divided into three main work sectors: conventional industry (8.24%), medicine (90.20%) and research-education (1.56%). The average annual dose for all workers in each particular sector was 0.14, 0.38 and 0.08 mSv, respectively, in 1995-1999. This paper contains the detailed analysis of occupational exposure. The statistical analysis provided includes the mean annual dose, the collective dose, the distributions of the dose over the different sectors and the number of workers who have exceeded any of the established dose levels.     

Occupational exposure to ionising radiation with thermoluminescence dosimetry system in Turkey, in 2003

The individual annual dose information on classified workers who are occupationally exposed to extended radiation sources by using thermoluminescence dosimetry system, in Turkey, was assessed and analysed by the Ankara Nuclear Research and Training Centre (ANAEM) dosimetry service at the Turkish Atomic Energy Authority (TAEK) for the year 2003. A total of 3721 persons were monitored with TLD and the data presented in this report were obtained by using TLD technology in 2003. The annual mean effective doses received from external radiation in different fields of activities and the distribution of the annual effective dose by dose intervals are presented. The collective annual dose by field of activity is estimated and the contribution to the total annual collective dose is determined.     

Temperature dependence of characteristic parameters of the Au/C<Subscript>20</Subscript>H<Subscript>12</Subscript>/n-Si Schottky barrier diodes (SBDs) in the wide temperature range

Au/C₂₀H₁₂/n-Si SBD was fabricated and its characteristic parameters such as reverse-saturation current (I_o), ideality factor (n), zero-bias barrier height (Φ_bo), series and shunt resistances (R_s, R_sh) were found as 1.974 × 10^?7 A, 6.434, 0.351 eV, 30.22 Ω and 18.96 kΩ at 160 K and 1.061 × 10^?6 A, 2.34, 0.836 eV, 5.82 Ω and 24.52 kΩ at 380 K, respectively. While the value of n decreases with increasing temperature, Φ_bo increases. The change in Φ_bo with temperature is not agreement with negative temperature coefficient of forbidden band-gap of semiconductor (Si). Thus, Φ _bo versus n, Φ _bo and (n^?1 ? 1) versus q/2kT plots were drawn to obtain an evidence of a Gaussian distribution (GD) of the BHs and all of them have a straight line. The mean value of BH (\( \overline{\varPhi }_{bo} \)) was found as 0.983 eV from the intercept of Φ _bo versus n plot (for n = 1). Also, the value of \( \overline{\varPhi }_{bo} \) and standard deviation (σ_s) were found as 1.123 eV and 0.151 V from the slope and intercept of Φ_bo versus q/2kT plot. By using the modified Richardson plot, the \( \overline{\varPhi }_{bo} \) and Richardson constant (A*) values were obtained as 1.116 eV and 113.44 A cm^?2 K^?2 from the slope and intercept of this plot, respectively. It is clear that this value of A* (=113.44 A cm^?2 K^?2) is very close to their theoretical value of 112 A cm^?2 K^?2 for n-Si. In addition, the energy density distribution profile of surface states (D_it) was obtained from the forward bias I–V data by taking into account the bias dependent of the effective barrier height (Φ _e ) and ideality factor n(V) for four different temperatures (160, 200, 300, and 380 K). In conclusion, the I–V–T measurements of the Au/C₂₀H₁₂/n-Si SBD in the whole temperature range can be successfully explained on the basis of thermionic emission (TE) theory with GD of the BHs.     

Dose evaluation in criticality accidents using response of panasonic TL personal dosemeters (UD-809/UD-802)

This study gives the results of dosimetry measurements carried out in the Silène reactor at Valduc (France) with neutron and photon personal thermoluminescence dosemeters (TLDs) in mixed neutron and gamma radiation fields, in the frame of the international accident dosimetry intercomparison programme in 2002. The intercomparison consisted of a series of three irradiation scenarios. The scenarios took place at the Valduc site (France) by using the Silène experimental reactor. For neutron and photon dosimetry, Panasonic model UD-809 and UD-802 personal TLDs were used together.     

Positive and Negative Pressure Regimes in Anisotropically Strained V2O3 Films

The metal-insulator phase transitions in V₂O₃ are considered archetypal manifestations of Mott physics. Despite decades of research, the effects of doping, pressure, and anisotropic strains on the transitions are still debated. To understand how these parameters control the transitions, anisotropically strained pure V₂O₃ films are explored with nearly the same contraction along the c-axis, but different degrees of ab-plane expansion. With small ab-plane expansion, the films behave similar to bulk V₂O₃ under hydrostatic pressure. However, with large ab-plane expansion, the films are driven into the “negative pressure” regime, similar to that of Cr-doped V₂O₃, exhibiting clear coexistence of paramagnetic insulator and paramagnetic metal phases between 180–500 K. This shows that c-axis contraction alone, or an increase in c/a ratio is insufficient for inducing “negative pressure” effects. Actually, c-axis contraction alone destabilizes the two insulating phases of V₂O₃, whereas a-axis expansion tends to stabilize them. The effects of strain are modeled using density functional theory providing good agreement with experimental results. The findings show that chemical pressure alone cannot account for the phase diagram of (V_1−xCr_x)₂O₃. This work enables to manipulate a Mott transition above room temperature, thereby expanding the opportunities for applications of V₂O₃ in novel electronics.