Bi2Te2Se and Sb2Te3 heterostructure based photodetectors with high responsivity and broadband photoresponse: experimental and theoretical analysis.

Topological insulators have emerged as one of the most promising candidates for the fabrication of novel electronic and optoelectronic devices due to the unique properties of nontrivial Dirac cones on the surface and a narrow bandgap in the bulk. In this work, the Sb2Te3 and Bi2Te2Se materials, and their heterostructure are fabricated by metal-organic chemical vapour deposition and evaporation techniques. Photodetection of these materials and their heterostructure shows that they detect light in a broadband range of 600 to 1100 nm with maximum photoresponse of Sb2Te3, Bi2Te2Se and Sb2Te3/Bi2Te2Se at 1100, 1000, and 1000 nm, respectively. The maximum responsivity values of Sb2Te3, Bi2Te2Se, and their heterostructure are 183, 341.8, and 245.9 A W-1 at 1000 nm, respectively. A computational study has also been done using density functional theory (DFT). Using the first-principles methods based on DFT, we have systematically investigated these topological insulators and their heterostructure's electronic and optical properties. The band structures of Sb2Te3 and Bi2Te2Se thin films (3 QL) and their heterostructure are calculated. The bandgaps of Sb2Te3 and Bi2Te2Se are 26.4 and 23 meV, respectively, while the Sb2Te3/Bi2Te2Se heterostructure shows metallic behaviour. For the optical properties, the dielectric function's real and imaginary parts are calculated using DFT and random phase approximation (RPA). It is observed that these topological materials and their heterostructure are light absorbers in a broadband range, with maximum absorption at 1.90, 2.40, and 3.21 eV.

Proximity induced band gap opening in topological-magnetic heterostructure (Ni80Fe20/p-TlBiSe2/p-Si) under ambient condition.

The broken time reversal symmetry states may result in the opening of a band gap in TlBiSe2 leading to several interesting phenomena which are potentially relevant for spintronic applications. In this work, the quantum interference and magnetic proximity effects have been studied in Ni80Fe20/p-TlBiSe2/p-Si (Magnetic/TI) heterostructure using physical vapor deposition technique. Raman analysis shows the symmetry breaking with the appearance of A21u mode. The electrical characteristics are investigated under dark and illumination conditions in the absence as well as in the presence of a magnetic field. The outcomes of the examined device reveal excellent photo response in both forward and reverse bias regions. Interestingly, under a magnetic field, the device shows a reduction in electrical conductivity at ambient conditions due to the crossover of weak localization and separation of weak antilocalization, which are experimentally confirmed by magnetoresistance measurement. Further, the photo response has also been assessed by the transient absorption spectroscopy through analysis of charge transfer and carrier relaxation mechanisms. Our results can be beneficial for quantum computation and further study of topological insulator/ferromagnet heterostructure and topological material based spintronic devices due to high spin orbit coupling along with dissipationless conduction channels at the surface states.

Outcomes of inpatient rehabilitation of patients with multiple sclerosis.

BACKGROUND: Several trials have demonstrated improved outcomes following inpatient rehabilitation for Multiple Sclerosis patients. Two populations were studied: patients in relapse and patients with no active medical problems recruited from the community. In every day practice, most admissions for MS inpatient rehabilitation aim to improve function following sudden deterioration. The outcomes of inpatient rehabilitation for this population were never studied. METHOD: Retrospective case note analysis of consecutive admissions of MS patients from 2005 to 2009 to a specialist neurological rehabilitation unit. RESULTS: Forty-one cases were identified. 26 were females. Age 25-71 (mean 52 ± 12). Disease duration 0-39 years (mean 13 ± 11). 20 patients were admitted from the community and 21 were transferred from acute hospital beds. Length of stay ranged between 11 to 152 days (mean 49 ± 36). Mean length of stay for wheelchair dependent patients was approximately double the length of stay for ambulatory patients. Improving mobility, transfer or posture were the primary cause of admissions in 37 cases. Sixteen out of 21 ambulatory patients (76%) attained 100% mobility goals. Only 4 out of 20 wheelchair bound patients (20%) achieved 100% mobility goals (P 0.002). Neither the type of MS nor the duration of it influenced the overall outcome. CONCLUSION: Our results suggest that MS patients admitted for rehabilitation following deterioration secondary to a medical or surgical cause show the same favourable outcome that was demonstrated with MS stable patients or in relapse. Baseline mobility, but not type and duration of MS, seems to have a significant impact on the rehabilitation outcome in terms of gaol achievement.

Validation of the language component of the Addenbrooke's Cognitive Examination--Revised (ACE-R) as a screening tool for aphasia in stroke patients.

AIM: Several tests are available for aphasia screening following stroke. However, some of them have shortcomings such as need of specialist knowledge, low sensitivity and/or specificity and lengthy administration time. Our study aims to evaluate the language component of the Addenbrooke's Cognitive Examination--Revised (ACE-R) as a screening tool for aphasia in stroke patients. METHODS: The language component of ACE-R was administered to consecutive patients admitted to a post-acute stroke unit. Patients who were medically unstable or had a significant history of sensory impairment or mental health issues were excluded. The test was administered by two junior doctors with basic training in ACE-R administration. Patients recruited were also assessed by an experienced speech and language therapist (SLT). The results of the two assessments were documented by a different member of the team and the SLT results were used as the benchmark to calculate the ACE-R language component sensitivity and specificity. RESULTS: Fifty-nine participants were recruited and 27 of them were women. The mean age was 72 (SD 11.9). Thirty-four participants had left and 11 right hemisphere stroke. Fourteen had bilateral affection. Six participants were left handed. A cut-off value of 22/26 of ACE-R language component showed 100% specificity and 83.1% sensitivity, while a cut-off value of 16/26 had 88.2% specificity and 100% sensitivity. CONCLUSION: Our results suggest that the language component of ACE-R has a satisfactory sensitivity and specificity compared with other screening tests used in strokes. It is easy to administer and free to use.

Complete immobility as a potential biomechanical complication of Achilles tendon lengthening.

Proximal muscle weakness is a common association of muscular dystrophies. Knees and hip extensor weakness limit the patients' ability to counteract flexor knee joints' moments. Therefore, patients try to toe walk to move the ground reaction force (GRF) anteriorly to help to stabilise the knee. We report a case of a patient with Becker's muscular dystrophy who lost his ability to walk completely following a bilateral Achilles tendons operation. The patient's ability to heel-strike moved his GRF posteriorly resulting in creation of excessive knees flexion moments. Three years following the operation and following a lengthy rehabilitation programme, the patient managed to mobilise using an orthosis.