SYNTHESIS AND ELECTRICAL CONDUCTIVITY OF SOLID SOLUTIONS OF THE SYSTEM PbF2–NdF3–SnF2

In the system PbF2–NdF3–SnF2 are formed solid solutions of the heterovalent substitution Pb0,86-хNdхSn1,14F4+х (0 < x ≤ 0,17) with structure of β–PbSnF4. At x > 0,17 on the X-ray diffractograms, in addition to the basic structure, additional peaks are recorded to the reflexes of the individual NdF3. For single-phase solid solutions, the calculated parameters of the crystal lattice are satisfactorily described by the Vegard rule. The introduction of ions of Nd3+ into the initial structure leads to an increase in the parameter с of the elementary cell from 51.267 Å for x = 0,03 to 51.577 Å for x = 0.17. The replacement of a part of leads ions to neodymium ions an increase in electrical conductivity compared with Pb0.86Sn1.14F4. The slight replacement (3.0 mol. %) of Pb2+ ions by Nd3+ in the structure of Pb0.86Sn1.14F4 causes an increase in the electrical conductivity at T> 530 K (6.88·10-2 S/cm compared to 2.41·10-2 S/cm for the initial sample compound Pb0.86Sn1.14F4). In the region of lower temperatures, the electrical conductivity of the samples of this composition decreases, and below that temperature, on the contrary, slightly reduces the electrical conductivity, approaching the values characteristic of β-PbSnF4. The activation energy of the conductivity thus increases over the entire temperature range. A further increase in the concentration of Nd3+ ions in the synthesized samples causes an increase in their fluoride-ion conductivity throughout the temperature range. It should be noted that samples with a content of 10-15 mol% NdF3 at T>500 K have comparable conductivity values. At lower temperatures, the higher the conductivity, the higher the concentration of the substituent. The highest conductivity and the lowest activation energy have the sample Pb0.69Nd0.17Sn1.14F4.17 (σ373=3.68·10-2 S/сm, Ea=0,1 eV). The fluorine anions in synthesized phases are in three structurally-equivalent positions. The charge transfer is provided by the highly mobile interstitial fluorine anions, whose concentration increases with increasing temperature and concentration of NdF3. The transfer numbers for fluorine anions are not less than 0.99, practically independent of the concentration of neodymium trifluoride.

Evaluating the effects of a peer-led suturing and wound management workshop for doctors working in a psychiatric hospital

BackgroundPsychiatric in-patients are often transferred to an emergency department for care of minor wounds, incurring significant distress to the patient and cost to the service.AimsTo improve superficial wound management in psychiatric in-patients and reduce transfers to the emergency department.MethodThirty-four trainees attended two peer-led suturing and wound management teaching sessions, and a suturing kit box was compiled and stored at the Royal Edinburgh Hospital. Teaching was evaluated using Kirkpatrick's model, and patient transfer numbers were acquired by reviewing in-patient Datix reports and emergency department case notes for 6 months before and after teaching.ResultsThe proportion of patients transferred to the emergency department decreased significantly from 90% 6 months before the workshop to 30% 6 months after (P < 0.05). Trainees engaged positively and there was a significant increase in self-confidence rating following the workshop (P < 0.05). The estimated cost saving per transfer was £183.76.ConclusionThe combination of a peer-led workshop and on-site suturing kit box was effective in reducing transfers to the emergency department and provided a substantial cost saving.Declaration of interestNone.

Effect of thiophene S on the enhanced ORR electrocatalytic performance of sulfur-doped graphene quantum dot/reduced graphene oxide nanocomposites

Thiophene S of sulfur-doped graphene quantum dots play an important role in electrocatalysis by increasing the electron transfer numbers.

Resistivity measured by direct and alternating current: why are they different?

Mathematical modeling of a little known model of IP referred to as "induced polarization caused by constrictivity of pores" was developed. Polarization occurs in all types of rocks if surface areas and transfer numbers are different for connected pores. The duration of the polarization process depends on two parameters: pore radii of connected capillaries and transfer numbers. During the polarization process all contacts between pores of different transfer numbers will be blocked and the electrical current will flow through the remaining canals. Two phenomena control the amplitude of potential difference at time-on: 1. Successive blockage of pores increases the resistivity of sediments and results in increased measured potential difference. 2. Excess concentration of electrolyte at the boundaries between pores with different radii provides an additional potential. The amplitude of the potential difference (voltage) of such rocks not only depends on solutions filling pore spaces, porosity and tourtuosity of pores channels, but also on ion mobility, diffusion coefficient, and difference of transfer numbers. During time-on a voltage is occurred due to flowing current Ucurr (t) and excess concentration Uexcess (t) at the contacts. However during the time-off only the excess of concentration Uexcess (t) is involved in the diffusion process which tends to level the ion concentration along the pores. It was found that the measured chargeability is proportional to the porosity. Blockage of pores and excess/loss ions at the contacted pores control this physical parameter. However the relationship between resistivity and porosity is very complicated. Mathematical modeling and laboratory measurements both confirmed the membrane IP effect diminishing with increasing salinity of fluid filled pores of rocks. Membrane polarization does not exist on high frequency of electrical current. As a result the resistivity measured by direct and alternating current is different. The new algorithm was tested on laboratory measurements data showing its good agreement with theory. The calculation of pore size distribution using IP laboratory data has been presented. The definition of the membrane IP effect is: "Membrane IP is the successive blockage of inter-pore connections due to the excess distribution of ions during current flow".

Transfer number in fine bubble diffused aeration systems

On the basis of full-scale data from 58 clean water tests performed in 26 activated sludge tanks equipped with fine bubble diffusers and of a theoretical approach, it can be stated that fine bubble aeration systems with total floor coverage arrangement provide higher kLa values and the lowest spiral liquid circulation. An efficiency criterion for oxygen transfer ( NT) was defined on the basis of the dimensional analysis. The transfer number NT allows us to take account of the impact of vertical liquid circulation movements on oxygen transfer. The values of NT calculated from the results of full scale nonsteady-state clean water tests vary from 5.3×10-5 to 9.1×10-5 and are directly dependent upon the arrangement of air diffusers. It has been shown that the highest transfer numbers corresponded to the total floor coverage arrangement and the average calculated NT values is 7.7×10-5, independently of the diffuser density and of the gas velocity, over the ranges studied. The lowest transfer numbers are obtained when the diffusers are located in separate grids, and the transfer number is reduced with increasing air flow rate.

Selection of Experimental Conditions for the Accurate Determination of Blood — Brain Transfer Constants from Single-Time Experiments: A Theoretical Analysis

Reliable blood–brain transfer constants can be determined from data obtained in single-time experiments (i.e., a single experimental time for tissue sampling). The accuracy of such measurements depends on factors such as the test molecule used and the experimental time chosen; therefore, the selection of optimal experimental conditions is important. In this presentation, a model of transport across the blood–brain barrier (BBB) was developed and used to determine appropriate experimental protocols for single-time experiments. Transfer numbers derived from published data with α-aminoisobutyric acid (AIB; a compound of low BBB permeability that is readily taken up by brain cells) and diethylenetriaminepentaacetic acid (DTPA; a compound of very low BBB permeability that is not taken up by brain cells) were inserted into the model and apparent blood-to-brain transfer constants ( K1) were obtained. In addition, the two basic sets of transfer numbers were altered to mimic various experimental and pathological changes in blood–brain transport. The results of this analysis indicate that moderate to large transfer rates across the BBB (0.01–1.0 ml g−1 min−1) are more easily and reliably measured by AIB-like compounds. In contrast, compounds like DTPA are better test-molecules for measuring small changes in the BBB transfer rate (0.0001–0.001 ml g−1 min−1), provided an appropriate experimental time is chosen.