Private Index Coding

This paper has been presented at: 2018 IEEE International Symposium On Information Theory (ISIT)We study the problem of index coding under the privacy requirement that receivers do not learn anything more than the messages they already have as side information and the message they want from the server. To achieve this private index coding, we consider the use of secret keys that are shared among various subsets of users and the server. We characterize key access structures that allow private index coding. For up to three receivers, we characterize the rate region of transmission and key rates and show that scalar coding is optimal; we also show that scalar linear codes are sub-optimal for four receivers. Furthermore, when no keys are available, we consider a weaker notion of privacy analogous to weak security. Finally, for a different setting in which the server is allowed to send messages exclusively to a subset of users, we study the number of transmissions required to achieve error-free decoding and privacy.Prabhakaran and N. Karamchandani acknowledge initial discussions with Parathasarathi Panda and Vaishakh Ravi. V. Narayanan was supported by a travel fellowship from the Sarojini Damodaran Foundation. This work was done while Jithin Ravi was at Tata Institute of Fundamental Research and IIT Bombay. He has received funding from ERC grant 714161

Environmental effect on the mechanical properties of commingled-yarn-based carbon fibre/polyamide 6 composites

The main objective of this experimental investigation was to evaluate the changes from accelerated ageing on selected properties of carbon fibre/polyamide 6 composites based on hybrid yarns. In this study, two types of mechanical tests were performed to measure the environmental influence on the material properties. They are three-point bending to measure the flexural strength and stiffness, and short beam three-point bending to measure the interlaminar shear strength. The 10-mm-thick quasi-isotropic carbon fibre/polyamide 6 composites with 52% volume fraction of carbon fibre to be tested were manufactured by autoclave consolidation. The test samples were dried, and subsequently exposed to 60°C and 100% relative humidity at different lengths of time up to 2500�h, followed by drying at 23°C and 50% relative humidity. Few samples were additionally completely dried at 70°C in vacuum for 21 months. Tests were also performed on as manufactured and dried material at low temperature (�45°C) and high temperature (115°C). The measured mechanical properties decreased with exposure time at 60°C and 100% relative humidity. Both the bending stiffness and the strength degrade to a level of about 65%, whereas interlaminar shear strength drops to about 87% of the property values of the unexposed (initially dried) material. The bending stiffness and strength at �45°C are about 87% of the properties at room temperature, whereas at 115°C the stiffness drops to 75% and the strength drops to 60% of the properties at room temperature. The interlaminar shear strength values also drop to about 75% at both �45°C and 115°C. Extreme temperatures and long-time exposure to humidity of quasi-isotropic carbon fibre/polyamide 6 laminates can thus reduce the bending stiffness and strength by up to 35% and the interlaminar shear strength by up to 25%

Rationale and population-based prospective cohort protocol for the disadvantaged populations at risk of decline in eGFR (CO-DEGREE)

Introduction: A recently recognised form of chronic kidney disease (CKD) of unknown origin (CKDu) is afflicting communities, mostly in rural areas in several regions of the world. Prevalence studies are being conducted in a number of countries, using a standardised protocol, to estimate the distribution of estimated glomerular filtration rate (eGFR), and thus identify communities with a high prevalence of reduced glomerular filtration rate (GFR). In this paper, we propose a standardised minimum protocol for cohort studies in high-risk communities aimed at investigating the incidence of, and risk factors for, early kidney dysfunction. Methods and analysis: This generic cohort protocol provides the information to establish a prospective population-based cohort study in low-income settings with a high prevalence of CKDu. This involves a baseline survey that included key elements from the DEGREE survey (eg, using the previously published DEGREE methodology) of a population-representative sample, and subsequent follow-up visits in young adults (without a pre-existing diagnosis of CKD (eGFR<60 mL/min/1.73m2), proteinuria or risk factors for CKD at baseline) over several years. Each visit involves a core questionnaire, and collection and storage of biological samples. Local capacity to measure serum creatinine will be required so that immediate feedback on kidney function can be provided to participants. After completion of follow-up, repeat measures of creatinine should be conducted in a central laboratory, using reference standards traceable to isotope dilution mass spectrometry (IDMS) quality control material to quantify the main outcome of eGFR decline over time, alongside a description of the early evolution of disease and risk factors for eGFR decline. Ethics and dissemination: Ethical approval will be obtained by local researchers, and participants will provide informed consent before the study commences. Participants will typically receive feedback and advice on their laboratory results, and referral to a local health system where appropriate