Separate Ratio-type Estimators of Population Mean in Stratified Random Sampling

Separate ratio-type estimators for population mean with their properties are considered. Some separate ratio-type estimators for population mean using known parameters of auxiliary variate are proposed. The bias and mean squared error of the proposed estimators are obtained up to the first degree of approximation. It is shown that the proposed estimators are more efficient than unbiased estimators in stratified random sampling and usual separate ratio estimators under certain obtained conditions. To judge the merits of the proposed estimators, an empirical study was conducted

Bellrock: Anonymous Proximity Beacons from Personal Devices

Proximity beacons provide simple, low-cost location data. However, beacon deployments remain rare. In this paper we introduce Bellrock, a framework that repurposes static personal devices (phones, laptops, etc.) as proximity beacons without revealing the location of the device owners, and provides conventional beacons with access control. This is done by using mutable pseudo-anonymous identifiers that can be unmasked by a cloud service. We develop Bellrock as a general framework, describing the repurposing scheme and the anonymisation techniques, before applying it to Bluetooth Low Energy beacons. We implement and demonstrate the scalability of the de-anonymisation server, which uses a series of heuristics. We implement a Bellrock client on Android and demonstrate negligible impact on battery lifetime. We evaluate Bellrock using extensive real-world office worker movements. We find that Bellrock was able to provide proximity locations for 8,542 of the 21,796 failed locations that would have occurred without it. We further find that office workers were in range of one or more of their co-workers over 90\% of the time, indicating Bellrock can provide relative proximity information even in the absence of a conventional beacon deployment. Overall, we find that Bellrock is both feasible and practical, providing a beacon deployment where there was none, or supplementing existing deployments

Childhood amblyopia: current management and new trends

INTRODUCTION OR BACKGROUND: With a prevalence of 2-5%, amblyopia is the most common vision deficit in children in the UK and the second most common cause of functional low vision in children in low-income countries. SOURCES OF DATA: Pubmed, Cochrane library and clinical trial registries (clinicaltrials.gov, ISRCTN, UKCRN portfolio database). AREAS OF AGREEMENT: Screening and treatment at the age of 4-5 years are cost efficient and clinically effective. Optical treatment (glasses) alone can improve visual acuity, with residual amblyopia treated by part-time occlusion or pharmacological blurring of the better-seeing eye. Treatment after the end of the conventional 'critical period' can improve vision, but in strabismic amblyopia carries a low risk of double vision. AREAS OF CONTROVERSY: It is not clear whether earlier vision screening would be cost efficient and associated with better outcomes. Optimization of treatment by individualized patching regimes or early start of occlusion, and novel binocular treatment approaches may enhance adherence to treatment, provide better outcomes and shorten treatment duration. GROWING POINTS: Binocular treatments for amblyopia. AREAS TIMELY FOR DEVELOPING RESEARCH: Impact of amblyopia on education and quality of life; optimal screening timing and tests; optimal administration of conventional treatments; development of child-friendly, effective and safe binocular treatments

Simulation of the Raman spectroscopy of multi-layered carbon nanomaterials

Multi-layered carbon nanomaterials can have an important role in modern nanotechnology. Raman spectroscopy is a widely used analytical technique that is used to characterise the structure of these materials. In this work, an approach based upon an empirical potential for the simulation of the Raman spectroscopy of carbon nanomaterials [Carbon, 113 (2017) 299] is extended through the addition of a term to describe the Van der Waals interaction between layers of sp2 hybridised carbons. The resulting model accurately describes the properties of the shearing modes of few layer graphene and is used to characterise the low frequency modes of multi-walled carbon nanotubes and carbon nanofibres

Development of an in vitro microfluidic model to study the role of microenvironmental cells in oral cancer metastasis.

Metastasis occurs when cancer cells leave the primary tumour and travel to a secondary site to form a new lesion. The tumour microenvironment (TME) is recognised to greatly influence this process, with for instance the vascular system enabling the dissemination of the cells into other tissues. However, understanding the exact role of these microenvironmental cells during metastasis has proven challenging. Indeed, in vitro models often appear too simplistic, and the study of the interactions between different cell types in a 3D space is limited. On the other hand, even though in vivo models incorporate the TME, observing cells in real-time to understand their exact role is difficult. Horizontal compartmentalised microfluidic models are a promising new platform for metastasis studies. These devices, composed of adjacent microchannels, can incorporate multiple cell types within a 3D space. Furthermore, the transparency and thickness of these models also enables high quality real-time imaging to be performed. This paper demonstrates how these devices can be successfully used for oral squamous cell carcinoma (OSCC) metastasis studies, focusing on the role of the vascular system in this process. Conditions for co-culture of OSCC cells and endothelial cells have been determined and staining protocols optimised. Furthermore, several imaging analysis techniques for these models are described, enabling precise segmentation of the different cell types on the images as well as accurate assessment of their phenotype. These methods can be applied to any study aiming to understand the role of microenvironmental cell types in cancer metastatic dissemination, and overcome several challenges encountered with current in vitro and in vivo models. Hence, this new in vitro model capable of recapitulating important aspects of the cellular complexity of human metastatic dissemination can ultimately contribute to replacing animal studies in this field

Mechanical Ventilator for Delivery of 17O2 in Brief Pulses

The 17O nucleus has been used recently by several groups for magnetic resonance (MR) imaging of cerebral metabolism. Inhalational delivery of 17O2 in very brief pulses could, in theory, have significant advantages for determination of the cerebral metabolic rate for oxygen (CMRO2) with MR imaging. Mechanical ventilators, however, are not typically capable of creating step changes in gas concentration at the airway. We designed a ventilator for large animal and human studies that provides mechanical ventilation to a subject inside an MR scanner through 25 feet of small-bore connecting tubing, and tested its capabilities using helium as a surrogate for 17O2. After switching the source gas from oxygen to helium, the 0-90% response time for helium concentration changes at the airway was 2.4 seconds. The capability for creating rapid step changes in gas concentration at the airway in large animal and human studies should facilitate the experimental testing of the delivery 17O2 in brief pulses, and its potential use in imaging CMRO2