A self-consistent theory for graphene transport

We demonstrate theoretically that most of the observed transport properties of graphene sheets at zero magnetic field can be explained by scattering from charged impurities. We find that, contrary to common perception, these properties are not universal but depend on the concentration of charged impurities n(imp). For dirty samples (250 x 10(10) cm(-2) < n(imp) < 400 x 10(10) cm(-2)), the value of the minimum conductivity at low carrier density is indeed 4e(2)/h in agreement with early experiments, with weak dependence on impurity concentration. For cleaner samples, we predict that the minimum conductivity depends strongly on n(imp), increasing to 8e(2)/h for n(imp) approximately 20 x 10(10) cm(-2). A clear strategy to improve graphene mobility is to eliminate charged impurities or use a substrate with a larger dielectric constant.     

Anyonic braiding in optical lattices

Topological quantum states of matter, both Abelian and non-Abelian, are characterized by excitations whose wavefunctions undergo nontrivial statistical transformations as one excitation is moved (braided) around another. Topological quantum computation proposes to use the topological protection and the braiding statistics of a non-Abelian topological state to perform quantum computation. The enormous technological prospect of topological quantum computation provides new motivation for experimentally observing a topological state. Here, we explicitly work out a realistic experimental scheme to create and braid the Abelian topological excitations in the Kitaev model built on a tunable robust system, a cold atom optical lattice. We also demonstrate how to detect the key feature of these excitations: their braiding statistics. Observation of this statistics would directly establish the existence of anyons, quantum particles that are neither fermions nor bosons. In addition to establishing topological matter, the experimental scheme we develop here can also be adapted to a non-Abelian topological state, supported by the same Kitaev model but in a different parameter regime, to eventually build topologically protected quantum gates.     

Virological and clinical cure in COVID-19 patients treated with hydroxychloroquine: A systematic review and meta-analysis

Following the demonstration of the efficacy of hydroxychloroquine against severe acute respiratory syndrome coronavirus 2 in vitro, many trials started to evaluate its efficacy in clinical settings. However, no systematic review and meta-analysis have addressed the issue of the safety and efficacy of hydroxychloroquine (HCQ) in coronavirus disease 2019. We conducted a systematic review and meta-analysis with the objectives of evaluation of safety and efficacy of HCQ alone or in combination in terms of “time to clinical cure,” “virological cure,” “death or clinical worsening of disease,” “radiological progression,” and safety. RevMan was used for meta-analysis. We searched 16 literature databases out of which seven studies (n = 1358) were included in the systematic review. In terms of clinical cure, two studies reported possible benefit in “time to body temperature normalization” and one study reported less “cough days” in the HCQ arm. Treatment with HCQ resulted in less number of cases showing the radiological progression of lung disease (odds ratio [OR], 0.31, 95% confidence interval [CI], 0.11-0.9). No difference was observed in virological cure (OR, 2.37, 95% CI, 0.13-44.53), death or clinical worsening of disease (OR, 1.37, 95% CI, 1.37-21.97), and safety (OR, 2.19, 95% CI, 0.59-8.18), when compared with the control/conventional treatment. Five studies reported either the safety or efficacy of HCQ + azithromycin. Although seems safe and effective, more data are required for a definitive conclusion. HCQ seems to be promising in terms of less number of cases with radiological progression with a comparable safety profile to control/conventional treatment. We need more data to come to a definite conclusion.     

Valsalva retinopathy with double ring sign: Laser membranotomy for twin bleeds

This report describes the case of a 27-year-old lady who presented with sudden decrease in vision in the right eye for one week. She was suffering from constipation and had a history of straining while passing stools. She was found to have two large sub-internal limiting membrane haemorrhages with the classical double ring sign, which were drained using laser membranotomy, following which her vision rapidly improved. This case of two sub-internal limiting membrane haemorrhages is reported for its rarity and also highlights the usefulness of laser hyaloidotomy or membranotomy in large haemorrhages of recent onset. The literature was also reviewed to discuss the other treatment options in brief.     

Mortality among epilepsy patients attending a tertiary referral center in a developing country.

Epilepsy is associated with excess mortality of two to three times in developed countries. Precise epidemiological data on mortality and cause of death are not available from India or most other developing countries. This study was carried out to estimate the mortality rates and to identify the demographic and clinical characteristics associated with mortality in a hospital based cohort of epilepsy patients. A cohort of patients enrolled in the epilepsy clinic in 1985 was followed up till 1997 (12 years). The mortality rate, demographic and clinical correlate of mortality were analysed for 246 patients (men 161, women 85) who had complete data. Cause of death was not examined in this study. Eighteen (men 15, women 3) of the 246 patients (7.3%) had died during the follow up period of 12 years. The crude death rate for the state of Kerala for the year 1990 (mid period of the study) was 5.9 per thousand population. The demographic and clinical characteristics of those who died (corresponding figures for survivors are given in brackets) were as follows: mean age 33.6 years (22.8 years), presence of abnormal neurological examination 38.9% (15.4%), mental retardation 33.3% (12.8%), abnormal CT scan 38% (21.5%). Regarding the seizure frequency at the time of enrollment and eventual mortality, there were no deaths among patients who had an Engel's seizure score of less than or equal to 4 (no seizures or nocturnal seizures only). The mortality was 5% for an Engel's score of 5 or 6 and 11% for an Engel's score greater than 6. Within the group with epilepsy, higher seizure frequency at the time of initial evaluation was associated with excess mortality. Abnormality on neurological examination, older age group and male sex were other factors that correlated with excess mortality.     

The use of heterogeneous acellular dermal matrix in the closure of hard palatal fistula

Objective

The aim of this study was to evaluate the efficacy of closure of hard palatal fistula using Heal-All^® Oral Biofilm, a heterogeneous acellular dermal matrix graft.

Patients and methods

Superior lip mucosal or myomucosal flap and buccal myomucosal flap were used in 20 patients (group 1) (2000–2005); whereas, heterogeneous acellular dermal matrix graft was performed in 18 patients (group 2) (2005–2013). The recurrence in the closed fistula and the obliteration of gingivolabial and gingivobuccal sulci were seen postoperatively with follow-up appointments at 1–3 months for all cases.

Results

The recurrence rate of hard palatal fistula has been reduced from 25 to 11.1% with the use of heterogeneous acellular dermal matrix graft, and the rate of the obliteration of gingivolabial and gingivobuccal sulci has been decreased from 90 to 5.5%.

Conclusions

Closure of hard palatal fistula using Heal-All^® Oral Biofilm graft is a useful method with high success rate. It is a day-case procedure especially to avoid dividing the pedical of the flap after follow-up, and the gingivolabial and gingivobuccal sulci do not need further procedures to deep with follow-up.