Raman excitation spectroscopy of carbon nanotubes: effects of pressure medium and pressure

Raman excitation and emission spectra for the radial breathing mode (RBM) are reported, together with a preliminary analysis. From the position of the peaks on the two-dimensional plot of excitation resonance energy against Raman shift, the chiral indices (m, n) for each peak are identified. Peaks shift from their positions in air when different pressure media are added - water, hexane, sulphuric acid - and when the nanotubes are unbundled in water with surfactant and sonication. The shift is about 2 - 3 cm-1 in RBM frequency, but unexpectedly large in resonance energy, being spread over up to 100meV for a given peak. This contrasts with the effect of pressure. The shift of the peaks of semiconducting nanotubes in water under pressure is orthogonal to the shift from air to water. This permits the separation of the effects of the pressure medium and the pressure, and will enable the true pressure coefficients of the RBM and the other Raman peaks for each (m, n) to be established unambiguously.Comment: 6 pages, 3 Figures, Proceedings of EHPRG 2011 (Paris

Pressure coefficients of Raman modes of carbon nanotubes resolved by chirality: Environmental effect on graphene sheet

Studies of the mechanical properties of single-walled carbon nanotubes are hindered by the availability only of ensembles of tubes with a range of diameters. Tunable Raman excitation spectroscopy picks out identifiable tubes. Under high pressure, the radial breathing mode shows a strong environmental effect shown here to be largely independent of the nature of the environment . For the G-mode, the pressure coefficient varies with diameter consistent with the thick-wall tube model. However, results show an unexpectedly strong environmental effect on the pressure coefficients. Reappraisal of data for graphene and graphite gives the G-mode Grueuneisen parameter gamma = 1.34 and the shear deformation parameter beta = 1.34.Comment: Submitted to Physical Review

The CMS Tracker Readout Front End Driver

The Front End Driver, FED, is a 9U 400mm VME64x card designed for reading out the Compact Muon Solenoid, CMS, silicon tracker signals transmitted by the APV25 analogue pipeline Application Specific Integrated Circuits. The FED receives the signals via 96 optical fibers at a total input rate of 3.4 GB/sec. The signals are digitized and processed by applying algorithms for pedestal and common mode noise subtraction. Algorithms that search for clusters of hits are used to further reduce the input rate. Only the cluster data along with trigger information of the event are transmitted to the CMS data acquisition system using the S-LINK64 protocol at a maximum rate of 400 MB/sec. All data processing algorithms on the FED are executed in large on-board Field Programmable Gate Arrays. Results on the design, performance, testing and quality control of the FED are presented and discussed

Recognizing and managing a malignant hyperthermia crisis: guidelines from the European Malignant Hyperthermia Group

Survival from a malignant hyperthermia (MH) crisis is highly dependent on early recognition and prompt action. MH crises are very rare and an increasing use of total i.v. anaesthesia is likely to make it even rarer, leading to the potential risk of reduced awareness of MH. In addition, dantrolene, the cornerstone of successful MH treatment, is unavailable in large areas around the world thereby increasing the risk of MH fatalities in these areas. The European Malignant Hyperthermia Group collected and reviewed all guidelines available from the various MH centres in order to provide a consensus document. The guidelines consist of two textboxes: Box 1 on recognizing MH and Box 2 on the treatment of an MH crisi

Recombination via transition metals in solar silicon : the significance of hydrogen-metal reactions and lattice sites of metal atoms

The move towards lower cost sources of solar silicon has intensified efforts to investigate the possibilities of passivating or reducing the recombination activity caused by deep states associated with transition metals. This is particularly important for the case of the slow diffusing metals early in the periodic sequence which are not removed by conventional gettering. In this paper we examine reactions between hydrogen and transition metals and discuss the possibility of such reactions during cell processing. We analyse the case of hydrogenation of iron in p-type Si and show that FeH can form under non-equilibrium conditions. We consider the electrical activity of the slow diffusing metals Ti, V and Mo, how this is affected in the presence of hydrogen, and the stability of TM-H complexes formed. Finally we discuss recent experiments which indicate that resiting of some transition metals from the interstitial to substitutional site is possible in the presence of excess vacancies, leading to a reduction in recombination activity

Energy levels in polarization superlattices: a comparison of continuum strain models

A theoretical model for the energy levels in polarization superlattices is presented. The model includes the effect of strain on the local polarization-induced electric fields and the subsequent effect on the energy levels. Two continuum strain models are contrasted. One is the standard strain model derived from Hooke's law that is typically used to calculate energy levels in polarization superlattices and quantum wells. The other is a fully-coupled strain model derived from the thermodynamic equation of state for piezoelectric materials. The latter is more complete and applicable to strongly piezoelectric materials where corrections to the standard model are significant. The underlying theory has been applied to AlGaN/GaN superlattices and quantum wells. It is found that the fully-coupled strain model yields very different electric fields from the standard model. The calculated intersubband transition energies are shifted by approximately 5 -- 19 meV, depending on the structure. Thus from a device standpoint, the effect of applying the fully-coupled model produces a very measurable shift in the peak wavelength. This result has implications for the design of AlGaN/GaN optical switches.Comment: Revtex

The role of the global cryosphere in the fate of organic contaminants

The cryosphere is an important component of global organic contaminant cycles. Snow is an efficient scavenger of atmospheric organic pollutants while a seasonal snowpack, sea ice, glaciers and ice caps are contaminant reservoirs on time scales ranging from days to millennia. Important physical and chemical processes occurring in the various cryospheric compartments impact contaminant cycling and fate. A variety of interactions and feedbacks also occur within the cryospheric system, most of which are susceptible to perturbations due to climate change. In this article, we review the current state of knowledge regarding the transport and processing of organic contaminants in the global cryosphere with an emphasis on the role of a changing climate. Given the complexity of contaminant interactions with the cryosphere and limitations on resources and research capacity, interdisciplinary research and extended collaborations are essential to close identified knowledge gaps and to improve our understanding of contaminant fate under a changing climate

Internet sourcing and UK end consumer trend interest in the controlled medicines (opioids, sedatives and GABA drugs) in pre and post COVID-19 timeframes.

Sourcing and self-medication of medicinal pharmaceuticals including those containing opioids obtained from non-regulated online suppliers is a serious public health issue. The main concerns include a lack of quality control, drug side effects, drug interactions, diversion and possible pathway to drug dependence. The internet offers increased availability and accessibility of these medicines through both legal routes obtaining pharmaceuticals on prescription and illegal routes via websites on both the surface and Dark Web. The impact of the current severe acute respiratory syndrome coronavirus 2 (SARSCoV-2 or COVID-19) pandemic reduced face-to face access for non-COVID-19 related health conditions and to drug treatment services. This study provides an overview of the extent of online sourcing of UK controlled medicines (opioids, sedatives and GABA drugs) from unregulated suppliers and estimates of customer interest, in particular focusing on the COVID-19 lockdown period in the UK, where access to some healthcare services was limited. Whilst it was not possible to identify an increase for online searches for controlled medicines over the past five years, or during the COVID-19 period, searches remained plentiful, in particular for oxycodone, morphine and diazepam. This study highlights the need for enhanced pharmacovigilance of non-regulated online suppliers and the imperatives of continued health messaging around the potential abuse of these controlled drugs and the dangers of using sites purporting to be regulated pharmacies

Internet sourcing and unsafe use of controlled medicines (opioids, sedatives and GABA drugs) in the UK: An in-depth case study of consumer dynamics during COVID-19

The Internet offers increased availability and accessibility of medicinal pharmaceuticals including those containing opioids, sedatives and gamma-aminobutyric acid (GABA) drugs through both legal and illegal routes. Sourcing concerns have been further heightened due to the current severe acute respiratory syndrome coronavirus 2 (COVID-19) pandemic which reduced face-to-face access for non-COVID-19 related health conditions and to drug treatment services. This study is the second of a two stage study comprising interviews with three key stakeholders who were policy makers, health care professionals or police, and three individuals who sourced medicinal products online (ISOs). An in-depth case study approach was adopted. Thematic analysis of in-depth case narratives revealed the following key themes; Motivations, initiation, and making the move online; Process of sourcing online; Supply issues and COVID-19; Perception of control; Quality of medications; and Public health recommendations. Motivations for purchasing online are complex and methods to divert and control the supply of medicinal pharmaceuticals are equally complex and difficult to navigate. Novel routes to access now include Telegram, a cross-platform messaging service with enhance encryption and privacy. Whilst stakeholders and ISOs had similar views on the prevalence and ease of access to medication, there were also some substantial differences primarily in terms of perceptions of risk. This study highlights the need for enhanced pharmacovigilance of non-regulated online vendors and the imperatives of continued health messaging around the potential self-directed use of these controlled drugs and the dangers of using websites purporting to be regulated pharmacies