Service differentiation for the bandwidth request scheme in fixed IEEE 802.16 networks

IEEE 802.16 standards have been developed as one of the technical solutions for broadband wireless access systems. It has high data rate, large network coverage, flexible QoS schemes and cheap network deployment. Various flexible mechanisms related to QoS provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and besteffort services. These two services are used for most application with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities. The effectiveness of the differentiation schemes are evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better. ©2008 IEEE.

Obstacles and solutions to maximising biodiversity in major urban development schemes

The current rate of global biodiversity loss led many governments to sign the international agreement ‘Halting Biodiversity Loss by 2010 and beyond’ in 2001. The UK government was one of these and has a number of methods to tackle this, such as: commissioning specific technical guidance and supporting the UK Biodiversity Acton Plan (BAP) targets. However, by far the most effective influence the government has upon current biodiversity levels is through the town planning system. This is due to the control it has over all phases of a new development scheme’s lifecycle.There is an increasing myriad of regulations, policies and legislation, which deal with biodiversity protection and enhancement across the hierarchical spectrum: from the global and European level, down to regional and local levels. With these drivers in place, coupled with the promotion of benefits and incentives, increasing biodiversity value ought to be an achievable goal on most, if not all development sites. However, in the professional world, this is not the case due to a number of obstructions. Many of these tend to be ‘process’ barriers, which are particularly prevalent with ‘urban’ and ‘major’ development schemes, and is where the focus of this research paper lies.The paper summarises and discusses the results of a questionnaire survey, regarding obstacles to maximising biodiversity enhancements on major urban development schemes. The questionnaire was completed by Local Government Ecologists in England. The paper additionally refers to insights from previous action research, specialist interviews, and case studies, to reveal the key process obstacles.Solutions to these obstacles are then alluded to and recommendations are made within the discussion.

Challenges and emerging solutions in the development of compressed orally disintegrating tablets

Areas covered: The review discusses the main challenges of ODT manufacturing process and the emerging solutions featured at early drug development stages. The research specifically describes the methods reported for taste masking/assessment and solubilisation of unpalatable and poorly soluble drugs, respectively. Furthermore, this review highlights the techniques used for developing modified-release ODTs, an emerging area in the field. In addition, it also discusses the poor flowability and segregation problems of directly compressed powders. Moreover, the review describes the tests reported in the literature for ODT disintegration time assessment since a universal technique is still non-existent. Expert opinion: The approaches used to overcome the manufacturing challenges often have a bearing on the price of the end product. However, despite the technical and regulatory challenges, ODTs can offer many advantages over the conventional dosage forms if accompanied by suitable adjuvant technologies and in vitro analytical tools. © 2014 Informa UK, Ltd. Introduction: Orally disintegrating tablets (ODTs) provide several advantages over conventional tablets such as suitability for patients with swallowing difficulties and faster onset of action. The manufacture of ODTs by compression/tableting offers a practical and cost-effective strategy over the freeze drying (lyophilisation) method. Nonetheless, the FDA recommends a disintegration time of 30 s and a maximum weight of 500 mg for a tablet to be labelled as an ODT. These requirements, alongside other desirable product properties, have created a number of challenges for the formulator to overcome while developing compressed ODTs.

Human brain slices for epilepsy research:pitfalls, solutions and future challenges

Increasingly, neuroscientists are taking the opportunity to use live human tissue obtained from elective neurosurgical procedures for electrophysiological studies in vitro. Access to this valuable resource permits unique studies into the network dynamics that contribute to the generation of pathological electrical activity in the human epileptic brain. Whilst this approach has provided insights into the mechanistic features of electrophysiological patterns associated with human epilepsy, it is not without technical and methodological challenges. This review outlines the main difficulties associated with working with epileptic human brain slices from the point of collection, through the stages of preparation, storage and recording. Moreover, it outlines the limitations, in terms of the nature of epileptic activity that can be observed in such tissue, in particular, the rarity of spontaneous ictal discharges, we discuss manipulations that can be utilised to induce such activity. In addition to discussing conventional electrophysiological techniques that are routinely employed in epileptic human brain slices, we review how imaging and multielectrode array recordings could provide novel insights into the network dynamics of human epileptogenesis. Acute studies in human brain slices are ultimately limited by the lifetime of the tissue so overcoming this issue provides increased opportunity for information gain. We review the literature with respect to organotypic culture techniques that may hold the key to prolonging the viability of this material. A combination of long-term culture techniques, viral transduction approaches and electrophysiology in human brain slices promotes the possibility of large scale monitoring and manipulation of neuronal activity in epileptic microcircuits.