The state of the art in beyond 5G distributed massive multiple-input multiple-output communication system solutions.

Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.

Three-dimensional reconstruction of porous polymer films from FIB-SEM nanotomography data using random forests.

Combined focused ion beam and scanning electron microscope (FIB-SEM) tomography is a well-established technique for high resolution imaging and reconstruction of the microstructure of a wide range of materials. Segmentation of FIB-SEM data is complicated due to a number of factors; the most prominent is that for porous materials, the scanning electron microscope image slices contain information not only from the planar cross-section of the material but also from underlying, exposed subsurface pores. In this work, we develop a segmentation method for FIB-SEM data from ethyl cellulose porous films made from ethyl cellulose and hydroxypropyl cellulose (EC/HPC) polymer blends. These materials are used for coating pharmaceutical oral dosage forms (tablets or pellets) to control drug release. We study three samples of ethyl cellulose and hydroxypropyl cellulose with different volume fractions where the hydroxypropyl cellulose phase has been leached out, resulting in a porous material. The data are segmented using scale-space features and a random forest classifier. We demonstrate good agreement with manual segmentations. The method enables quantitative characterization and subsequent optimization of material structure for controlled release applications. Although the methodology is demonstrated on porous polymer films, it is applicable to other soft porous materials imaged by FIB-SEM. We make the data and software used publicly available to facilitate further development of FIB-SEM segmentation methods. LAY DESCRIPTION: For imaging of very fine structures in materials, the resolution limits of, e.g. X-ray computed tomography quickly become a bottleneck. Scanning electron microscopy (SEM) provides a way out, but it is essentially a two-dimensional imaging technique. One manner in which to extend it to three dimensions is to use a focused ion beam (FIB) combined with a scanning electron microscopy and acquire tomography data. In FIB-SEM tomography, ions are used to perform serial sectioning and the electron beam is used to image the cross section surface. This is a well-established method for a wide range of materials. However, image analysis of FIB-SEM data is complicated for a variety of reasons, in particular for porous media. In this work, we analyse FIB-SEM data from ethyl cellulose porous films made from ethyl cellulose and hydroxypropyl cellulose (EC/HPC) polymer blends. These films are used as coatings for controlled drug release. The aim is to perform image segmentation, i.e. to identify which parts of the image data constitute the pores and the solid, respectively. Manual segmentation, i.e. when a trained operator manually identifies areas constituting pores and solid, is too time-consuming to do in full for our very large data sets. However, by performing manual segmentation on a set of small, random regions of the data, we can train a machine learning algorithm to perform automatic segmentation on the entire data sets. The method yields good agreement with the manual segmentations and yields porosities of the entire data sets in very good agreement with expected values. The method facilitates understanding and quantitative characterization of the geometrical structure of the materials, and ultimately understanding of how to tailor the drug release.

3D high spatial resolution visualisation and quantification of interconnectivity in polymer films.

A porous network acts as transport paths for drugs through films for controlled drug release. The interconnectivity of the network strongly influences the transport properties. It is therefore important to quantify the interconnectivity and correlate it to transport properties for control and design of new films. This work presents a novel method for 3D visualisation and analysis of interconnectivity. High spatial resolution 3D data on porous polymer films for controlled drug release has been acquired using a focused ion beam (FIB) combined with a scanning electron microscope (SEM). The data analysis method enables visualisation of pore paths starting at a chosen inlet pore, dividing them into groups by length, enabling a more detailed quantification and visualisation. The method also enables identification of central features of the porous network by quantification of channels where pore paths coincide. The method was applied to FIB-SEM data of three leached ethyl cellulose (EC)/hydroxypropyl cellulose (HPC) films with different weight percentages. The results from the analysis were consistent with the experimentally measured release properties of the films. The interconnectivity and porosity increase with increasing amount of HPC. The bottleneck effect was strong in the leached film with lowest porosity.

Observations on spontaneous recovery from intervertebral disc herniation.

Spontaneous recovery from disc herniation is well known and is an important aspect of treatment strategy. Computed imaging studies have provided further insight into the possible mechanisms of recovery.

Identification and management of radiculopathy.

Proper identification of compressive radiculopathy is essential before any treatment can be undertaken. The differential recognition of different pain patterns, sensory symptoms, and neurologic deficits provides the clinical guide to specific nerve root involvement. Appropriate radiology and imaging must correlate with symptoms and signs. Management includes surgical intervention when indicated for relief of radicular pain and restoration of function.

Role of laminectomy in lumbar disk herniation.

A personal view of the role of laminectomy in lumbar disk herniation is presented. The phenomena of the true herniated nucleus pulposus and the asymptomatic bulging degenerative disk are discussed in relation to clinical presentation, neuroradiologic studies, and surgical findings. Microscopic technique and so-called less invasive procedures are also evaluated.

Lumbar microdiscectomy: a contrary opinion.

Successful operation for ruptured lumbar disc is directly related to appropriate selection of patients and an operative approach designed for the particular size and location of the compressed fragment of disc. Lumbar microdiscectomy provides no advantage when operation is clearly indicated and adds the additional risks that have always accompanied inadequate exposure and incomplete decompression.

Professional liability and potential liability.

Operations on the nervous system continue to result in claims that rank among the most costly. A retrospective review of 300 cases of alleged or potential liability referred for opinion over an 11-year period is reported to catalog areas of vulnerability for the neurosurgeon and to alert younger practitioners in particular. Spinal surgery produced the largest single group of neurosurgical malpractice cases, 136 of the 300; among these, 71 came from operations on the lumbar spine. Cerebral and spinal trauma accounted for 54 cases, the next largest group. Subgroups were studied in detail and provide individual features of some importance. Other conclusions are that 37% of all cases reviewed were found to have some merit in favor of the claimant; plaintiffs and their attorneys can be dissuaded from legal pursuit if the deficit is not serious; many defensible cases are settled or lost on the basis of disability rather than merit; and some type of reform of the present system is clearly needed.