Pseudogap in BaPbxBi1‒xO3(x = 0.7, 0.75 and 1.0)

In this work, we have investigated the crystal and electronic structure of the orthorhombic phase of BaPbxBi1-xO3(BPBO) forx = 0.7 (BPBO70), 0.75 (BPBO75) and 1.0 (BPO), using temperature dependent x-ray diffraction measurements, photoemission spectroscopy, and electronic structure calculations. Our results show the importance of particle size and strain in governing superconductivity. Interestingly, the temperature evolution of the structural parameters in the case of BPBO70 is similar to that of BPBO75 but the magnitude of the change is diminished. The BPBO75 and BPO compounds exhibit metallic nature, which is corroborated by the core level studies. The electronic structure calculations in conjunction with the core level studies suggest that oxygen vacancies play an important role for metallicity observed in the end compound. The exponent to the spectral line shape close to the Fermi level suggests the origin of pseudogap to be due to other contributions in addition to disorder in the case of BPBO70 and BPO. The core level studies also show that as one goes fromx = 0.70 to 1.0, there occurs chemical potential shift towards the valence band suggesting hole doping. Our results open the venue to further study these compounds as a function of particle size, nature of carriers for its transport behaviour, electronic structure belowTC, composition at the grain boundaries and microscopic origin of pseudogap in the non-superconducting phase. We believe that our results call for a revision of the temperature-doping phase diagram of BPBO to include the pseudogap phase.

Eustachian tube dysfunction in an intensive care unit: A prospective observational study

Background

Eustachain tube (ET) dysfunction can aggravate the morbidity in ICU patients, but is often ignored. In this prospective observational study we followed a cohort of patients (without pre-existing ET dysfunction) requiring in-patient management, hospitalized either to ICU or to non ICU wards, for any development of ET dysfunction during hospitalization.

Methods

Patients requiring hospitalization to ICU or non ICU wards from Dec 2018 to Jun 2019 were included. Those with pre-existing ET dysfunction, disease of ear/nose or sinuses, head neck tumours and history of radiotherapy or glucocorticoid therapy were excluded. All patients were evaluated by serial tympanometry. Type A curve was considered normal while type B, C1 and C2 were considered as ET dysfunction.

Results

There were 385 patients, 258 (67.01%) males and 127 (32.99%) females in the ICU group; while non ICU group comprised 129 patients, 86 (66.67%) males and 43 (33.33%) females. ET dysfunction developed in 107 (27.79%) patients in ICU group, but only in 3 (2.3%) in non ICU group (Relative risk 11.95, 95% CI 3.86 to 36.99, P < 0.0001). Within ICU, ET dysfunction showed significant positive association with endotracheal intubation, Ramsay sedation score and number of days on tracheostomy; but not with age, male gender, number of days in ICU, mechanical ventilation or route of feeding.

Conclusion

Our study demonstrates high incidence of ET dysfunction in patients admitted to ICU.

Evidence of lattice strain as a precursor to superconductivity in BaPb0.75Bi0.25O3

In this work, we have investigated the precursor effects to superconductivity in BaPb_0.75Bi_0.25O₃using temperature dependent resistivity, x-ray diffraction technique and photoemission spectroscopy. The present compound exhibits superconductivity around 11 K (TC). The synthesis procedure adopted is much simpler as compared to the procedure available in the literature. In the temperature range (10 K-25 K) i.e. aboveTC, our results show an increase in both the orthorhombic and tetragonal strain. The well screened features observed in Bi and Pb 4f7/2core levels are indicative of the metallic nature of the sample. The compound exhibits finite intensity at the Fermi level at 300 K and this intensity decreases with decrease in temperature and develops into a pseudogap; the energy dependence of the spectral density of states suggests disordered metallic state. Furthermore, our band structure calculations reveal that the structural transition upon Pb doping results in the closing of the band gap at the Fermi level.

Interplay of lattice distortion and electronic structure in BaBiO3

We investigate room temperature core level and valence band spectra of BaBiO₃ using x-ray photoemission spectroscopy and band structure calculations. The features in the valence band spectrum were studied using density functional theory (DFT) under local density approximation (LDA) and Tran Blaha modified Becke Johnson (TB mBJ) exchange potential. The calculations were performed for three different structural parameters; monoclinic, cubic and monoclinic (M[Formula: see text]). Our results of the core level spectrum and DFT calculations rule out charge disproportionation of the Bi ions. The valence band spectrum displays gap at the Fermi edge and fine structures in the region close to the Fermi edge. The DFT calculation under TB mBJ for the monoclinic structure is able to generate gap and match the energy positions of the fine structure in a better way. Our calculation results show that there are holes in the O 2[Formula: see text] states and unequal transfer of electrons to the states of the Bi ions. Such mechanism could lead to bond disproportionation and its association with the fine structures in the valence band. The current results reveal the significance of strong link between the lattice distortion and electronic structure and hence to its physical properties.

Prophylactic use of antibiotics as per SIGN 104 guidelines versus routine antibiotic prophylaxis for prevention of surgical site infection in clean and clean contaminated ENT surgical procedures: a comparative study

<p class="abstract"><strong>Background:</strong> Many clinicians continue to use antibiotic prophylaxis routinely in all surgical procedures, ignoring the guidelines issued by policy makers. In this prospective study we compared the rate of surgical site infection (SSI) in patients who received prophylactic antibiotics as a routine; with the rate of SSI in patients getting antibiotics strictly as per SIGN 104 Guidelines, for clean and clean contaminated procedures.</p><p class="abstract"><strong>Methods:</strong> The study population comprised 235 patients. Group A consisted of 119 patients having 77 (65%) males and 42 (35%) females while Group B had 116 patients - 71 (61%) males and 45 (39%) females. Group A received routine antibiotic prophylaxis in all cases, while Group B received antibiotic prophylaxis as per SIGN 104 guidelines only. Both the groups were followed up for one month post-operatively for SSI and complications.</p><p class="abstract"><strong>Results:</strong> SSI occurred in 2 patients (1.68%) in Group A and in 3 (2.59%) patients in Group B. There was no significant difference in the rate of SSI between the two groups (p=0.68). Procedure wise maximum SSI occurred in tympanoplasty and laryngectomy. Due to infection one case of tympanoplasty had graft failure and one case of laryngectomy had delayed wound healing. No major complications related to infection or antibiotic use occurred in either group.</p><p class="abstract"><strong>Conclusions:</strong> Selective use of antibiotic prophylaxis as per SIGN 104 Guidelines does not lead to increase in SSI in clean and clean contaminated ENT procedures.</p>

What factors predetermine the risk of having a high-order multiple pregnancy with gamete intra-fallopian transfer?

Limiting the number of oocytes transferred at gamete intra-Fallopian transfer (GIFT) has limited the incidence of high-order pregnancy but at the same time compromised the fertility potential of some patients. A review of 300 patients who have undergone GIFT using a flexible approach as to the number of oocytes transferred identifies the patients at risk of high-order pregnancy as those aged under 30 years in whom more than six oocytes are returned and whose partner's spermatozoa have high progressive motility.