Quantum size effects and tunable visible photoluminescence in a-Si:H/nc-Si:H superlattices

Quantum size effects are commonly observed in semiconductor nanocrystals and quantum dots. Here, we demonstrate unexpected quantum size effects in an unusual bulk system with multiple interfaces, consisting of alternating layers of nanocrystalline silicon (nc-Si:H) and amorphous silicon (a-Si:H) material thin films. The nc-Si:H layers consist of silicon nanocrystals embedded in an amorphous matrix, with an amorphous-crystalline interface separating the two structures. Plasma-enhanced chemical vapor deposition was utilized to grow nanocrystalline-amorphous silicon superlattices with a varying thickness of the nanocrystalline layer. Strong visible photoluminescence at room temperature was deconvoluted into individual peaks. As the nanocrystalline silicon layer thickness was increased from 5 to 20 nm, the photoluminescence spectra red-shifted with the emission wavelength varying as d2 (d is the size of the nanocrystallites), the characteristic signature underlying quantum size effects. The size d of the nanocrystals was estimated by the measured shift of the Raman peak, and could be tuned by varying the thickness of the nc-Si:H layers. High resolution transmission electron microscopy show nanocrystals with a narrow size distribution, in an amorphous matrix. We also observe long wavelength photoluminescence from interfacial states that leads to persistent photconductivity. Nanocrystalline-amorphous superlattices offer a unique pathway for synthesizing embedded nanocrystals with controlled sizes and photonic signatures

A hospital based retrospective study on hepatotropic viruses as a cause of acute viral hepatitis in children in Uttarakhand, India

Introduction: Acute viral hepatitis in children is a serious health problem throughout the world. Aims and Objective: To determine the profile of Hepatitis A, B, C and E as a cause of acute viral hepatitis in children in a tertiary care hospital of Uttarakhand, India. Material and Methods: In this retrospective study, data was collected from the records of paediatric patients who underwent testing for one or more of the hepatitis viruses. Serum samples were tested for Anti-HAV IgM and Anti-HEV IgM by Enzyme Linked Immunosorbent Assay (ELISA) and Hepatitis B surface antigen and Anti HCV antibodies by enhanced chemiluminiscence.  Results: Among total of 252 patients suffering from Acute Viral Hepatitis (AVH), males predominated over females with 72.2 % vs. 27.8 %. Hepatitis A virus (72.6 %) was found to be the leading cause of AVH in our hospital followed by HBV (16.7 %), HEV (9.5 %) and the least common was HCV (1.1 %). Co-infection was seen in only 2 cases i.e one as HAV-HEV (0.4%) and other as HAV- HBV (0.4%). Out of all the cases of AVH, 9.5 % were suffering from Acute Hepatic Failure. Hepatitis A virus was found to be the most common cause of acute hepatic failure (50 %), followed by Hepatitis B (37.5 %) and Hepatitis E (12.5 %).  Conclusions: Hepatotropic viruses are quite prevalent in children in our country. Thus to control faeco-orally transmitted viruses i.e Hepatitis A and hepatitis E, awareness about healthy hygienic practices should be emphasized upon. Also hepatitis A vaccination can be recommended to be included in national immunization schedule. To prevent parenterally transmitted viruses like Hepatitis B and hepatitis C, use of sterile needles and syringes while tattooing, ear piercing and avoiding injections through unregistered medical practitioners should be done. Vaccination for hepatitis B should be routinely done

Hemostasis in patients with acute kidney injury secondary to acute liver failure

Acute kidney injury (AKI) occurs in over half of patients with acute liver failure. Despite prolonged prothrombin times and thrombocytopenia, continuous renal replacement therapy circuits frequently develop clots during patient treatment. Here we assessed factors contributing to this by measuring coagulation parameters (standard coagulation tests, pro- and anticoagulant factors, thromboelastography, and thrombin generation) in 20 consecutive patients with acute liver failure; mean age 42 years. Within 48 h, 10 had developed stage 3 AKI and 9 required continuous renal replacement therapy, of whom 2 had frequent circuit clots. The patients with stage 3 AKI were found to have significantly lower platelet counts and levels of factor V and the natural anticoagulants antithrombin, Protein C and Protein S, but increased extrinsic pathway activation and von Willebrand factor levels. Tissue factor levels were greater in those with stage 3 AKI, as was microparticle activity. Although patients with acute liver failure and advanced AKI requiring continuous renal replacement therapy have an even more marked thrombocytopenia and more prolonged extrinsic pathway activation, this was not associated with increased bleeding. Thus, more frequent circuit clots during continuous renal replacement therapy appear to be due to a combination of increased tissue factor and microparticle release, endothelial activation, and reduction in natural anticoagulants.peer-reviewe

Nebulized Recombinant Tissue Plasminogen Activator (rt-PA) for Acute COVID-19-Induced Respiratory Failure : An Exploratory Proof-of-Concept Trial

Acknowledgments We would like to extend our sincerest gratitude to all the colleagues and hospital staff who worked tirelessly throughout the pandemic and without whom this work would not have been possible. Firstly, we would like to thank our colleagues in the intensive care unit (ICU), in particular the matrons, Sean Carroll and Sinead Hanton, and research nurses, Filipe Helder and Amitaa Maharajh for their support, and bedside nurses who bore the responsibility of drug administration. We would also like to extend our thanks to ICU consultants who acted as professional legal consultees on behalf of critical care patients. Equally, we would like to thank colleagues within the respiratory team. Their expertise was instrumental to our role in treating patients on 8N and 8E wards. A special mention to lead Nurse Mary Emerson; we were grateful for her knowledge, support and for facilitating the training for the nebulizer and drug administration on the wards. We would like to thank Aarti Nandani and all the staff in the Royal Free clinical trials pharmacy for their immense support throughout the whole pandemic, especially considering their ever-increasing workload at the time. Thanks also to the HSL coagulation laboratory, the Trust R&D department and all the staff working to cover during a very challenging time. We are also very grateful to the Royal Free charity for funding this study. Finally, we would like to thank all the clinical nurses, physiotherapists, research data managers and healthcare professionals within the Haemophilia department (and wider hospital) for all their many efforts in supporting this study. This trial was overseen by an independent data monitoring committee, chaired by Najib Rahman, Director of the Oxford Respiratory Trials Unit, University of Oxford and comprises the following committee members: Mike Makris, Jonathan Silversides and Henry Watson. Funding Royal Free Charity Trust Fund 35 provided funding for this study. The study drug was provided by Boehringer Ingelheim (BI). BI had no role in the design, analysis, or interpretation of the results. They were given the opportunity to review the manuscript for medical and scientific accuracy since it relates to BI substances and intellectual property considerations.Peer reviewedPublisher PD

Transport and stability studies on high band gap a-Si : H films prepared by argon dilution

Device quality hydrogenated amorphous silicon films (a-Si:H) are deposited at a high deposition rate (4-5 angstrom/s) using a mixture of argon and hydrogen-diluted silane. The films exhibit good opto-electronic properties and show less degradation upon light soaking. Light-induced changes in conductivity could be annealed at much lower temperature. The presence of Ar* and atomic hydrogen in plasma replaces the weak Si-Si bonds, which are responsible for light-induced degradation by strong Si-Si bonds. This results in the improved stability of the films

From Phosphorous to Arsenic: Changing the Classic Paradigm for the Structure of Biomolecules

Biomolecules are composed primarily of the elements carbon, nitrogen, hydrogen, oxygen, sulfur, and phosphorus. The structured assembly of these elements forms the basis for proteins, nucleic acids and lipids. However, the recent discovery of a new bacterium, strain GFAJ-1 of the Halomonadaceae, has shaken the classic paradigms for the architecture of life. Mounting evidence supports the claim that these bacteria substitute arsenic for phosphorus in macromolecules. Herein, we provide a brief commentary and fuel the debate related to what may be a most unusual organism

Quantum size effects and tunable visible photoluminescence in a-Si:H/nc-Si:H superlattices

Quantum size effects are commonly observed in semiconductor nanocrystals and quantum dots. Here, we demonstrate unexpected quantum size effects in an unusual bulk system with multiple interfaces, consisting of alternating layers of nanocrystalline silicon (nc-Si:H) and amorphous silicon (a-Si:H) material thin films. The nc-Si:H layers consist of silicon nanocrystals embedded in an amorphous matrix, with an amorphous-crystalline interface separating the two structures. Plasma-enhanced chemical vapor deposition was utilized to grow nanocrystalline-amorphous silicon superlattices with a varying thickness of the nanocrystalline layer. Strong visible photoluminescence at room temperature was deconvoluted into individual peaks. As the nanocrystalline silicon layer thickness was increased from 5 to 20 nm, the photoluminescence spectra red-shifted with the emission wavelength varying as d2 (d is the size of the nanocrystallites), the characteristic signature underlying quantum size effects. The size d of the nanocrystals was estimated by the measured shift of the Raman peak, and could be tuned by varying the thickness of the nc-Si:H layers. High resolution transmission electron microscopy show nanocrystals with a narrow size distribution, in an amorphous matrix. We also observe long wavelength photoluminescence from interfacial states that leads to persistent photconductivity. Nanocrystalline-amorphous superlattices offer a unique pathway for synthesizing embedded nanocrystals with controlled sizes and photonic signatures.</p

Calvarial tuberculosis presenting as cystic lesion: An unusual presentation in two patients

Tuberculosis is a common disease in developing countries such as India, posing a major public health problem. With human immunodeficiency virus (HIV) infection being a global endemic, there has been a resurgence of tuberculosis even in developed countries. Tuberculosis may affect almost any part of the body. However, tuberculosis of the calvarium is very rare. Presentation of tuberculosis as a soft tissue swelling on the scalp poses a diagnostic problem. These two cases are being reported here to convey the utility of fine-needle aspiration cytology (FNAC) in providing the confirmatory diagnosis obviating the need for invasive surgical procedure

Safe perioperative opioid taper in cancer patients needs meticulous multimodal management

Opioid therapy plays a vital role in chronic pain management of advanced cancer patients. Some patients require discontinuation of opioids when an intervention appropriately controls the pain. Safe discontinuation of opioids poses a challenge among lack of evidence-based standardized taper protocol. We report a patient with a soft tissue sarcoma in whom opioid was tapered in the background of acute postoperative pain