DFT insights into the electronic structure, mechanical behaviour, lattice dynamics and defect processes in the first Sc-based MAX phase Sc2SnC.

Here we employed the density functional theory calculations to investigate some physical properties of first Sc-based MAX phase Sc2SnC including defect processes to compare with those of existing M2SnC phases. The calculated structural properties are in good agreement with the experimental values. The new phase Sc2SnC is structurally, mechanically and dynamically stable. Sc2SnC is metallic with a mixture of covalent and ionic character. The covalency of Sc2SnC including M2SnC is mostly controlled by the effective valence. Sc2SnC in M2SnC family ranks second in the scale of deformability and softness. The elastic anisotropy level in Sc2SnC is moderate compared to the other M2SnC phases. The hardness and melting point of Sc2SnC, including M2SnC, follows the trend of bulk modulus. Like other members of the M2SnC family, Sc2SnC has the potential to be etched into 2D MXenes and has the potential to be a thermal barrier coating material.

Indirect to direct band gap transition through order to disorder transformation of Cs2AgBiBr6 via creating antisite defects for optoelectronic and photovoltaic applications.

Non-toxic lead free inorganic metal halide cubic double perovskites have drawn a lot of attention for their commercial use in optoelectronic and photovoltaic devices. Here we have explored the structural, electronic, optical and mechanical properties of lead-free non-toxic inorganic metallic halide cubic double perovskite Cs2AgBiBr6 in its ordered and disordered forms using first-principles density functional theory (DFT) to verify the suitability of its photovoltaic and optoelectronic applications. The indirect bandgap of Cs2AgBiBr6 is tuned to a direct bandgap by changing it from an ordered to disordered system following the disordering of Ag+/Bi3+ cations by creating antisite defects in its sublattice. In the disordered Cs2AgBiBr6, the Bi 6p orbital modifies the conduction band significantly and leads to a shift the conduction band minimum (CBM) from L to Γ-point. Consequently, the system changes from indirect to direct band gap material. At the same time the band gap reduces significantly. The band gap of Cs2AgBiBr6 decreases from 2.04 eV to 1.59 eV. The absorption edge towards the lower energy region and strong optical absorption in the visible to the UV region indicate that the disordered direct band gap material Cs2AgBiBr6 is appropriate for use in solar cells and optoelectronic and energy harvesting devices. Dielectric function, reflectivity and refractive index of disordered direct band gap material Cs2AgBiBr6 is favorable for its optoelectronic and photovoltaic applications. However, its stability and ductility favor its thin film fabrication. The creation of antisite defects in the sublattice of double perovskites opens a new avenue for the design of photovoltaic and optoelectronic materials.

Effects of Al substitution by Si in Ti3AlC2 nanolaminate.

Recently, a series of high-purity Ti3(Al1-xSix)C2 solid solutions with new compositions (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been reported with interesting mechanical properties. Here, we have employed density functional theory for Ti3(Al1-xSix)C2 solid solutions to calculate a wider range of physical properties including structural, electronic, mechanical, thermal and optical. With the increase of x, a decrease of cell parameters is observed. All elastic constants and moduli increase with x. The Fermi level gradually increases, moving towards and past the upper bound of the pseudogap, when the value of x goes from zero to unity, indicating that the structural stability reduces gradually when the amount of Si increases within the Ti3(Al1-xSix)C2 system. In view of Cauchy pressure, Pugh's ratio and Poisson's ratio all compositions of Ti3(Al1-xSix)C2 are brittle in nature. Comparatively, low Debye temperature, lattice thermal conductivity and minimum thermal conductivity of Ti3AlC2 favor it to be a thermal barrier coating material. High melting temperatures implies that the solid solutions Ti3(Al1-xSix)C2 may have potential applications in harsh environments. In the visible region (1.8-3.1 eV), the minimum reflectivity of all compositions for both polarizations is above 45%, which makes them potential coating materials for solar heating reduction.

Chemically stable new MAX phase V2SnC: a damage and radiation tolerant TBC material.

Using density functional theory, the phase stability and physical properties, including structural, electronic, mechanical, thermal and vibrational with defect processes, of a newly synthesized 211 MAX phase V2SnC are investigated for the first time. The obtained results are compared with those found in the literature for other existing M2SnC (M = Ti, Zr, Hf, Nb, and Lu) phases. The formation of V2SnC is exothermic and this compound is intrinsically stable in agreement with the experiment. V2SnC has potential to be etched into 2D MXene. The new phase V2SnC and existing phase Nb2SnC are damage tolerant. V2SnC is elastically more anisotropic than Ti2SnC and less than the other M2SnC phases. The electronic band structure and Fermi surface of V2SnC indicate the possibility of occurrence of its superconductivity. V2SnC is expected to be a promising TBC material like Lu2SnC. The radiation tolerance in V2SnC is better than that in Lu2SnC.

312 MAX Phases: Elastic Properties and Lithiation.

Interest in the Mn+1AXn phases (M = early transition metal; A = group 13-16 elements, and X = C or N) is driven by their ceramic and metallic properties, which make them attractive candidates for numerous applications. In the present study, we use the density functional theory to calculate the elastic properties and the incorporation of lithium atoms in the 312 MAX phases. It is shown that the energy to incorporate one Li atom in Mo3SiC2, Hf3AlC2, Zr3AlC2, and Zr3SiC2 is particularly low, and thus, theoretically, these materials should be considered for battery applications.

Public safety assessment of electromagnetic radiation exposure from mobile base stations.

Exposure of the general public to electromagnetic radiation originating from randomly selected GSM/WCDMA base stations in Riyadh, Kingdom of Saudi Arabia has been assessed in the context of the International Commission on Non-Ionising Radiation Protection (ICNIRP) guidelines. The purpose of the measurement was to record the maximum power density of signals to estimate possible worst case exposure at each measurement location. These power density measurements were carried out at 60 mobile base stations located in different regions of the city. For each of these sites, three sectors were operational, yielding a total of 180 sectors. Two positions were identified per site with the greatest power density values. Exposures from these base stations were generally found to be in the range of 0.313 to 0.00000149% of the ICNIRP general public reference level, and the greatest exposure near any of the base stations was 21.96 mW m(-2) for a wideband measurement in the 75-3000 MHz frequency range. Analysis of the measured data reveals several trends for different mobile bands with respect to maximum exposure in those locations. Additionally, a simplified calculation method for the electromagnetic fields was used to compare calculated and the measured data. It was determined, on the basis of both results of the measurements and calculations carried out for these selected base stations, that members of the public would not be exposed to in excess of a small fraction of the ICNIRP guidelines at any of those sites. These are first such measurements to be made in the Middle East and provide assurance that exposures in this region of the world do not seem to be any greater than elsewhere.

Do all ionic liquids need organic cations? Characterisation of [AlCl2·nAmide]+ AlCl4(-) and comparison with imidazolium based systems.

The addition of a simple amide to AlCl(3) causes the formation of a liquid of the form [AlCl(2)·nAmide](+) AlCl(4)(-). The material thus produced is liquid over a wide temperature range, is relatively insensitive to water and has the properties of an ionic liquid. This ionic liquid is shown to be a suitable medium for the acetylation of ferrocene and the electrodeposition of aluminium and demonstrated that quaternary ammonium cations are not always needed to form ionic liquids.

Double layer, diluent and anode effects upon the electrodeposition of aluminium from chloroaluminate based ionic liquids.

The deposition of aluminium from a chloroaluminate based ionic liquid was studied to elucidate the effect of a diluent (toluene) and electrolyte (LiCl) on the deposit morphology. A wide variety of analytical techniques was applied to this system to determine the speciation and mechanism of material growth. These included: (27)Al NMR, FAB-MS, cyclic voltammetry, chronocoulometry, chronopotentiometry, scanning electron microscopy and atomic force microscopy. It was found that under-potential deposition (upd) causes a change in the way in which metal grows on the electrode surface. Metal grows in two regimes which are believed to be nano-material and bulk material. The addition of toluene causes a change in speciation and a decrease in upd which in turn changes the morphology of the deposit obtained and can lead to mirror finish aluminium. The addition of LiCl has the opposite effect encouraging upd and leading to larger crystallites and a dark grey deposit. It is also shown for the first time that under many conditions the rate of the anodic dissolution process is overall rate controlling and one effect of the addition of toluene is to increase the rate of anodic dissolution.

A comparative study of intravenous patient-controlled analgesia morphine and tramadol in patients undergoing major operation.

The success of major surgery depends partly on providing effective post-operative pain relief, which can be commonly achieved by morphine administration via patient- controlled analgesic (PCA) system. Alternatively, tramadol which is a weak opioid analgesic, can be used for post operative pain relief. The purpose of this study was to evaluate the effectiveness of intravenous PCA tramadol in comparison with PCA morphine in term of analgesic properties, sedation and side effects. A randomized, double-blinded study was conducted on 160 ASA I and II patients who underwent major operations. Eighty of them received a loading dose of intravenous morphine 0.1 mg/kg followed by PCA morphine bolus of 1 mg (1 mg/ml) as required, while the other 80 patients received a loading dose of 2.5 mg/kg of intravenous tramadol followed by PCA infusion of 10 mg (10 mg/ml) as required. Patients were monitored for pain, sedation and side effects as well as respiratory rate, nausea, vomiting, pruritus, blood pressure and pulse rate. Patients were evaluated 30 minutes, 4 hours, 24 hours and 48 hours post operation. There were no differences in the demographic data between the two groups (p > 0.05). The overall mean pain score in tramadol group was 0.70 +/- 0.60 as compared to 0.75 +/- 0.67 for morphine group. The mean pain score for tramadol and morphine groups at 30 minutes, 4 hours, 24 hours and 48 hours post operation were 1.32 +/- 0.79, 104 +/- 0.79, 0.35 +/- 0.48, 0.09 +/- 0.33 and 1.35 +/- 0.99, 1.14 +/- 0.81, 0.40 +/- 0.54, 0.10 +/- 0.34 respectively. The overall mean sedation score in tramadol and morphine group was 0.39 +/- 0.44 as compared to 0.35 +/- 0.43 for morphine group. The mean sedation score for tramadol and morphine group at 30 minutes, 4 hours, 24 hours and 48 hours post operation were 0.90 +/- 0.74, 0.56 +/- 0.59, 0.075 +/- 0.27, 0.025 +/- 0.16 and 0.84 +/- 0.70, 0.46 +/- 0.64, 0.08 +/- 0.27, 0.01 +/- 0.11 respectively. There was no significant difference in the overall mean pain and sedation score between the two groups as well as for each duration assessed (p > 0.05). There were also no significant differences between the two groups with regard to the blood pressure and heart rate. The incidence of nausea, vomiting and pruritus were the same in the two groups. This study indicates that PCA tramadol is as equally effective as PCA morphine control following major surgery. The incidences of sedation, nausea or pruritus were the same in the two groups.

The incidentally discovered asymptomatic adrenal tuberculous mass mimicking malignancy.

Tuberculous adrenal mass without any tuberculous changes in other sites is a rare entity. In this study we describe such a case. A male patient of 47 years with 6 months history of anorexia and weakness was presented. Ultrasonography and computed tomography revealed a mass in the right adrenal gland. It was mistaken as a malignant neoplasm and the diagnosis was confirmed by surgical exploration.

Spontaneous expulsion of intrabronchial metallic foreign body: a case report.

Inhalation of metallic foreign bodies is a rare event occurring mostly in children, and often requires early surgical intervention to avoid complications. We report a case of spontaneous expectoration of an intrabronchial metallic nail in an adult, 2 hours after inhalation.

Antibiotic compared with antiseptic prophylaxis for prostatic surgery.

Two different regimens of cephalosporin antibiotic prophylaxis were compared with antiseptic lubricating jelly to try to prevent infection and complications in 196 men after prostatic surgery. Pre-operative urine was cultured and prostatic chips (170 cases) were also cultured to define the source of any infection. The use of antibiotics was associated with a reduced risk of postoperative bacteriuria. No serious complications occurred, although 1 patient in the antiseptic treated group developed rigors; 79 of 170 patients (46%) had positive prostatic chip cultures, of whom 74 had sterile pre-operative urine. There was no association between the result of chip culture and the presence of a pre-operative catheter. Culture positive patients had an increased risk of post-operative urine infection, although the same organism was found in the prostate and urine in only 36% of cases of post-operative bacteriuria and in 43 (54%) the organism cultured from the prostate was Staphylococcus albus. This study provides further evidence of the benefit of true prophylactic antibiotic therapy for transurethral prostatic surgery and the prostatic chip data suggest that some of the risk is due to pre-operative contamination of the prostate in the absence of per-operative urinary infection or catheterisation.