A Low Cost Magnetic Resonance Relaxometry Sensor

Magnetic resonance relaxometry, conducted by measuring relaxation parameters at different field strengths, has become an increasingly popular technique in recent years. This technique, known as field cycling, often uses expensive and large electromagnets. In this work we present a small, portable field cycling sensor. Fast field cycling is a technique that uses a varying magnetic field applied to a sample, polarising it at a high field, allowing it time to develop at a lower field and then collecting the data at the same initial high field. This causes changes in T1 and can reveal interesting proper ties of the samples not seen by traditional methods. A prototype portable magnetic resonance sensor that undertakes relaxometry measurements using fast field cycling has been developed using a combination of permanent magnets which has been used to conduct preliminary studies on a water sample. We demonstrate the effectiveness of this sensor by conducting measurements of T1 at different field strengths

Effect of a photonic band gap on the threshold and output power of solid-state lasers and light-emitting diodes

We present results for the operation of a three-level solid-state laser both with normal and with completely suppressed spontaneous emission between the lasing levels. The output power difference in these two cases drops as the pump rate is increased above threshold and is not greatly different at higher powers. The threshold pump power, although typically reduced by an order of magnitude, is not zero and our results thus throw further light on the concept of “thresholdless” lasing. The theory is also applicable to light-emitting diodes and amplifiers which function on the same principles as a laser

Non-invasive measurements of the dry solids content of whole potatoes using unilateral magnetic resonance: towards automation

Crisps or chips are considered a popular snack food around the world and at their most fundamental are potatoes which are sliced and then fried. It has been known for some time that during their production industrially, controlling the final oil content requires prior knowledge of the dry solids of the potatoes to modify the temperature and frying time to give the best product. The dry weight of a batch of potatoes is most commonly performed using a buoyancy measurement. In preliminary experiments, we have found evidence that such a measurement, whilst representative of the average dry solids, does not offer the most appropriate measurement since the variation within the batch is significant. We present an investigation into the properties of intact potatoes using magnetic resonance relaxation measurements and relate these to the dry solids content. This preliminary study will lay the groundwork for the development of an online process monitoring device based around a unilateral sensor to allow batch sorting of incoming potatoes

An exploration of user intention and behaviour in the context of the economic development of technology-supported online social networks

Technology-supported online social networks have grown dramatically in recent years. Limited success has been achieved in economically developing them so that users make purchases through them. However these are largely ineffective as they are based on ‘targeting’ users with advertising in an attempt to stimulate them towards purchasing. The aim of the research was to explore how these networks could be economically developed in ways which users would welcome. The existing literature had gaps on how the intentions and behaviours of online social network users could be better understood in this context. Using a qualitative methodology semi-structured interviews were carried out with online social networks users. The research draws on the Theory of Planned Behaviour (TPB) (Ajzen, 1991-2006). It also explores how some aspects of the Social Network Theory (SNT) model developed by the researcher in Document 2, as well as some key constructs of the Technology Acceptance Model (TAM) (Davis et al., 1991; Venkatesh and Davis, 1994), may impact on TPB in this context. The findings arising from thematic analysis of the interviews led to proposing contextualised factors which could affect the key constructs in the TPB. Factors affecting network user attitudinal beliefs and evaluations in this context included Ease of Use, Utility and belief in the network’s capacity to deliver benefits. Factors affecting normative beliefs and motivation to comply included information-sharing, resistance to ‘assumed profiles’, self-setting of norms, and attitudes to personal data. Factors affecting control beliefs and facilitation included ‘Ultimate Control’, ‘Program Control’, 2-way information/control exchange dynamics, emotional bonding and user self-modification of behaviour. These led to a conceptual framework modifying TPB in the context of purchasing by network users. As well as contributing to theory there are some contributions to professional practice, including insight to providing more opportunities for enhancing user engagement and perception of control, ‘one-click’ access to ‘in-network’ vendors, An exploration of user intention and behaviour in the context of the economic development of technology-supported online social networks and facilities for users to express their interests in information on the goods and services which they would welcome. A number of proposals are also presented for extending the research in the future

Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes

Adverse childhood experiences: A retrospective study to understand their associations with lifetime mental health diagnosis, self-harm or suicide attempt, and current low mental wellbeing in a male Welsh prison population

Background: Prisoners are at increased risk of poor mental health and self-harming behaviours, with suicide being the leading cause of death in custody. Adverse childhood experiences (ACEs) such as child maltreatment are strong predictors of poor mental health and wellbeing yet despite high levels of ACEs in offender populations, relatively few studies have explored the relationships between ACEs and prisoners' mental health and wellbeing. We conducted an ACE survey with 468 male adult prisoners in a Welsh prison who were not currently considered to be at risk of self-harm and suicide and explored relationships between ACEs, lifetime mental illness diagnosis, self-harm (lifetime and lifetime in prison) or suicide attempt (lifetime and lifetime in prison), and current low mental wellbeing. Results: Most participants (84.2%) had suffered at least one ACE and 45.5% had suffered ≥4 ACEs. Prevalence of lifetime mental illness diagnosis, self-harm (lifetime and lifetime in prison) or suicide attempt (lifetime and lifetime in prison), and current low mental wellbeing increased with exposure to ACEs. For example, 2.7% of those with no ACEs reported lifetime self-harm or suicide attempt in prison compared with 31.0% (self-harm in prison) and 18.3% (suicide attempt in prison) of those with ≥4 ACEs. Compared with participants with no ACEs, those with ≥4 ACEs were four times more likely to report lifetime mental illness diagnosis and suicide attempt, and over 10 times more likely to report lifetime self-harm than those with no ACEs. Independent of lifetime mental illness diagnosis, self-harm or suicide attempt, participants with ≥4 ACEs were almost three times more likely to have current low mental wellbeing than those with no ACEs. Conclusions: Male prisoners that have suffered multiple ACEs are substantially more likely to have lifetime mental illness diagnosis, self-harm or suicide attempt, and to have current low mental wellbeing whilst in prison. Findings suggest that trauma-informed approaches are needed in prisons to support prisoner mental health and wellbeing

Imaging the Impact of Prenatal Alcohol Exposure on the Structure of the Developing Human Brain

Prenatal alcohol exposure has numerous effects on the developing brain, including damage to selective brain structure. We review structural magnetic resonance imaging (MRI) studies of brain abnormalities in subjects prenatally exposed to alcohol. The most common findings include reduced brain volume and malformations of the corpus callosum. Advanced methods have been able to detect shape, thickness and displacement changes throughout multiple brain regions. The teratogenic effects of alcohol appear to be widespread, affecting almost the entire brain. The only region that appears to be relatively spared is the occipital lobe. More recent studies have linked cognition to the underlying brain structure in alcohol-exposed subjects, and several report patterns in the severity of brain damage as it relates to facial dysmorphology or to extent of alcohol exposure. Future studies exploring relationships between brain structure, cognitive measures, dysmorphology, age, and other variables will be valuable for further comprehending the vast effects of prenatal alcohol exposure and for evaluating possible interventions

Investigation into the annotation of protocol sequencing steps in the sequence read archive

BACKGROUND: The workflow for the production of high-throughput sequencing data from nucleic acid samples is complex. There are a series of protocol steps to be followed in the preparation of samples for next-generation sequencing. The quantification of bias in a number of protocol steps, namely DNA fractionation, blunting, phosphorylation, adapter ligation and library enrichment, remains to be determined. RESULTS: We examined the experimental metadata of the public repository Sequence Read Archive (SRA) in order to ascertain the level of annotation of important sequencing steps in submissions to the database. Using SQL relational database queries (using the SRAdb SQLite database generated by the Bioconductor consortium) to search for keywords commonly occurring in key preparatory protocol steps partitioned over studies, we found that 7.10%, 5.84% and 7.57% of all records (fragmentation, ligation and enrichment, respectively), had at least one keyword corresponding to one of the three protocol steps. Only 4.06% of all records, partitioned over studies, had keywords for all three steps in the protocol (5.58% of all SRA records). CONCLUSIONS: The current level of annotation in the SRA inhibits systematic studies of bias due to these protocol steps. Downstream from this, meta-analyses and comparative studies based on these data will have a source of bias that cannot be quantified at present

A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone

Recommended standardized procedures for determining exhaled lower respiratory nitric oxide and nasal nitric oxide have been developed by task forces of the European Respiratory Society and the American Thoracic Society. These recommendations have paved the way for the measurement of nitric oxide to become a diagnostic tool for specific clinical applications. It would be desirable to develop similar guidelines for the sampling of other trace gases in exhaled breath, especially volatile organic compounds (VOCs) which reflect ongoing metabolism. The concentrations of water-soluble, blood-borne substances in exhaled breath are influenced by: (i) breathing patterns affecting gas exchange in the conducting airways; (ii) the concentrations in the tracheo-bronchial lining fluid; (iii) the alveolar and systemic concentrations of the compound. The classical Farhi equation takes only the alveolar concentrations into account. Real-time measurements of acetone in end-tidal breath under an ergometer challenge show characteristics which cannot be explained within the Farhi setting. Here we develop a compartment model that reliably captures these profiles and is capable of relating breath to the systemic concentrations of acetone. By comparison with experimental data it is inferred that the major part of variability in breath acetone concentrations (e.g., in response to moderate exercise or altered breathing patterns) can be attributed to airway gas exchange, with minimal changes of the underlying blood and tissue concentrations. Moreover, it is deduced that measured end-tidal breath concentrations of acetone determined during resting conditions and free breathing will be rather poor indicators for endogenous levels. Particularly, the current formulation includes the classical Farhi and the Scheid series inhomogeneity model as special limiting cases.Comment: 38 page

Debris Disks: Probing Planet Formation

Debris disks are the dust disks found around ~20% of nearby main sequence stars in far-IR surveys. They can be considered as descendants of protoplanetary disks or components of planetary systems, providing valuable information on circumstellar disk evolution and the outcome of planet formation. The debris disk population can be explained by the steady collisional erosion of planetesimal belts; population models constrain where (10-100au) and in what quantity (>1Mearth) planetesimals (>10km in size) typically form in protoplanetary disks. Gas is now seen long into the debris disk phase. Some of this is secondary implying planetesimals have a Solar System comet-like composition, but some systems may retain primordial gas. Ongoing planet formation processes are invoked for some debris disks, such as the continued growth of dwarf planets in an unstirred disk, or the growth of terrestrial planets through giant impacts. Planets imprint structure on debris disks in many ways; images of gaps, clumps, warps, eccentricities and other disk asymmetries, are readily explained by planets at >>5au. Hot dust in the region planets are commonly found (<5au) is seen for a growing number of stars. This dust usually originates in an outer belt (e.g., from exocomets), although an asteroid belt or recent collision is sometimes inferred.Comment: Invited review, accepted for publication in the 'Handbook of Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018