The effect of desiccation on the emission of volatile bromocarbons from two common temperate macroalgae

Exposure of intertidal macroalgae during low tide has been linked to the emission of a variety of atmospherically-important trace gases into the coastal atmosphere. In recent years, several studies have investigated the role of inorganic iodine and organoiodides as antioxidants and their emission during exposure to combat oxidative stress, yet the role of organic bromine species during desiccation is less well understood. In this study the emission of dibromomethane (CH2Br2) and bromoform (CHBr3) during exposure and desiccation of two common temperate macroalgae, Fucus vesiculosus and Ulva intestinalis, is reported. Determination of the impact exposure may have on algal physiological processes is difficult as intertidal species are adapted to desiccation and may undergo varying degrees of desiccation before their physiology is affected. For this reason we include comparisons between photosynthetic capacity (Fv/Fm) and halocarbon emissions during a desiccation time series. In addition, the role of rewetting with freshwater to simulate exposure to rain was also investigated. Our results show that an immediate flux of bromocarbons occurs upon exposure, followed by a decline in bromocarbon emissions. We suggest that this immediate bromocarbon pulse may be linked to volatilisation or emissions of existing bromocarbon stores from the algal surface rather than the production of bromocarbons as an antioxidant response

Increasing concentrations of dichloromethane, CH2Cl2, inferred from CARIBIC air samples collected 1998–2012

Atmospheric concentrations of dichloromethane, CH2Cl2, a regulated toxic air pollutant and minor contributor to stratospheric ozone depletion, were reported to have peaked around 1990 and to be declining in the early part of the 21st century. Recent observations suggest this trend has reversed and that CH2Cl2 is once again increasing in the atmosphere. Despite the importance of ongoing monitoring and reporting of atmospheric CH2Cl2, no time series has been discussed in detail since 2006. The CARIBIC project (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) has analysed the halocarbon content of whole-air samples collected at altitudes of between ~10–12 km via a custom-built container installed on commercial passenger aircraft since 1998, providing a long-term record of CH2Cl2 observations. In this paper we present this unique CH2Cl2 time series, discussing key flight routes which have been used at various times over the past 15 years. Between 1998 and 2012 increases were seen in all northern hemispheric regions and at different altitudes, ranging from ~7–10 ppt in background air to ~13–15 ppt in regions with stronger emissions (equating to a 38–69% increase). Of particular interest is the rising importance of India as a source of atmospheric CH2Cl2: based on CARIBIC data we provide regional emission estimates for the Indian subcontinent and show that regional emissions have increased from 3–14 Gg yr^-1 (1998–2000) to 16–25 Gg yr^-1 (2008). Potential causes of the increasing atmospheric burden of CH2Cl2 are discussed. One possible source is the increased use of CH2Cl2 as a feedstock for the production of HFC-32, a chemical used predominantly as a replacement for ozone-depleting substances in a variety of applications including air conditioners and refrigeration

Sustainability in quality improvement (SusQI): a case-study in undergraduate medical education

Background There is a pressing need for more sustainable healthcare. UK medical graduates are required to apply social, economic, and environmental principles of sustainability to their practice. The Centre for Sustainable Healthcare has developed a sustainability in quality improvement (SusQI) framework and educator’s toolkit to address these challenges. We aimed to develop and evaluate SusQI teaching using this toolkit at Bristol Medical School. Methods We facilitated a SusQI workshop for all third-year Bristol Medical School students. We used mixed methods including questionnaires, exit interviews and follow-up focus groups to evaluate the outcomes and processes of learning. Results Students reported: improvements in knowledge, confidence, and attitudes in both sustainable healthcare and quality improvement; increased self-rated likelihood to engage in SusQI projects; and willingness to change practices to reduce environmental impact in their healthcare roles. Factors for successful teaching included: interactivity; collaboration and participation; and real-life, relevant and tangible examples of projects delivered by credible role models. Conclusions Students reported that SusQI education supported by the toolkit was effective at building knowledge and skills, and reframed their thinking on sustainability in quality improvement. Combining the two topics provided enhanced motivation for and engagement in both. Further research is needed on the clinical impacts of SusQI learning

Sustainability in Quality Improvement (SusQI): challenges and strategies for translating undergraduate learning into clinical practice

Background The healthcare sector is a major contributor to climate change and there are international calls to mitigate environmental degradation through more sustainable forms of clinical care. The UK healthcare sector has committed to net zero carbon by 2040 and sustainable healthcare is a nationally mandated outcome for all UK graduating doctors who must demonstrate their ability to address social, economic and environmental challenges. Bristol Medical School piloted successful Sustainability in Quality Improvement (SusQI) workshop, but identified challenges translating classroom learning into clinical practice. This paper aims to identify and address those challenges. Methods We conducted five focus groups that identified and iteratively explored barriers and facilitators to practice among medical students, comparing a range of experiences to generate a conceptual framework. We then combined our findings with behaviour change theory to generate educational recommendations. Results Students that applied their learning to the clinical workplace were internally motivated and self-determined but needed time and opportunity to complete projects. Other students were cautious of disrupting established hierarchies and practices or frustrated by institutional inertia. These barriers impacted on their confidence in suggesting or achieving change. A minority saw sustainable healthcare as beyond their professional role. Conclusions We present a series of theoretically informed recommendations. These include wider curricular engagement with concepts of sustainable clinical practice; supportive workplace enablement strategies such as workplace champions and co-creation of improvement goals; and time and headspace for students to engage through structured opportunities for credit-bearing project work

Gradings of non-graded Hamiltonian Lie algebras

A thin Lie algebra is a Lie algebra graded over the positive integers satisfying a certain narrowness condition. We describe several cyclic grading of the modular Hamiltonian Lie algebras H(2\colon\n;\omega_2) (of dimension one less than a power of $p$) from which we construct infinite-dimensional thin Lie algebras. In the process we provide an explicit identification of H(2\colon\n;\omega_2) with a Block algebra. We also compute its second cohomology group and its derivation algebra (in arbitrary prime characteristic).Comment: 36 pages, to be published in J. Austral. Math. Soc. Ser.

References

www.biogeosciences-discuss.net/11/10673/2014/ doi:10.5194/bgd-11-10673-2014 © Author(s) 2014. CC Attribution 3.0 License. This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. The effect of desiccation on the emission of volatile bromocarbons from two common temperate macroalga

Specification and Data Presentation in Linear Control Systems-Part Two

This is the second part of a 2 volume report on the specification and data presentation in linear control systems. This volume deals with Sample Data Systems, Linear Time Variable Parameter Systems, and Performance Indices, which are respectively Chapter II, III, and IV of the volume. Since these subjects are somewhat unrelated, a separate abstract is given at the beginning of each chapter, with the exception of the introductory Chapter I. The separate chapter abstracts are repeated here for the convenience of the reader. Abstract - Linear Sampled Data Control Systems The specifications recommended, for use with sampled data control systems are those recommended for linear, continuous systems [1]. These specifications must be supplemented, as is dictated by the requirements of a particular system, by compatibility considerations that are detailed in the following sections. Abstract - The Specification of Linear Time Variable Parameter Systems Linear time variable parameter (LTVP) systems are defined and subdivided into those systems with fast or slow variations and/or large or small variations. The methods of analysis of such systems are reviewed, and the following recommendations are made. Specifications 1) Time Domain Specifications (a) LTVP systems with fast variation of parameters. Simulated unfrozen system step function responses should all lie within a prescribed envelope. Whenever possible, the actual system response should be obtained. (b) LTVP systems with slow variation of parameters. Simulated or actual frozen or unfrozen system step function responses should all lie within a prescribed envelope. 2) Frequency Domain Specifications (a) LTVP system with fast variation of parameters. Frequency domain specifications are not recommended. (b) LTFP system with slow variation of parameters. The family of frequency response curves of the system frozen at different instants should all lie within a predetermined envelope. Data Presentation It is recommended that the region of variation of closed loop poles of the frozen system be exhibited on the complex plane. Thus, for example, if the only varying parameter is an open loop gain, then the region of variation of the closed loop poles will correspond to the root loci over the total range of variation of gain. It is also recommended that a family of Nyquist diagrams corresponding to the system frozen at different instants be displayed in the case of system with slow variations of parameters. Abstract - Performance Index This study was undertaken to determine whether or not Performance Indices should be used to evaluate and specify control systems* It is recommended that they not be used at this time by the Air Force for the stated purpose. A performance index is defined and detailed discussions are presented for the various performance indices. Analytical methods for evaluating performance indices are presented

Stability of Nonlinear Control Systems by the Second Method of Liapunov

This report investigates the stability of autonomous closed-loop control systems containing nonlinear elements. An n-th order nonlinear autonomous system is described by a set of n first order differential equations of the type dxi/dt=xi(x1, x2, …xn) i=1,2,…n. Liapunov\u27s second (direct) method is used in the stability analysis of such systems. This method enables one to prove that a system is stable (or unstable) if a function V=V (x1, x2, … xn) can be found which, together with its time derivative, satisfies the requirements of Liapunov\u27s stability (or instability) theorems. At the present time, there are no generally applicable straight forward procedures available for constructing these Liapunov\u27s functions. Several Liapunov\u27s functions, applicable to systems described in the canonic form of differential equations, have been reported in the literature. In this report, it is shown that any autonomous closed-loop system containing a single nonlinear element can be described by canonic differential equations. The stability criteria derived from the Liapunov\u27s functions for canonic systems give sufficient and not necessary conditions for stability. It is known that these criteria reject many systems which are actually stable. The reasons why stable systems are sometimes rejected by these simplified stability criteria are investigated in the report. It is found that a closed-loop system will always be rejected by these simplified stabi1ity criteria if the root locus of the transfer function G(s), representing the linear portion of the system, is not confined to the left-half of the s-plane for all positive values of the loop gain. A pole-shifting technique and a zero-shifting technique, extending -the applicability of the simplified stability criteria to systems that are stable for sufficiently high and/or sufficiently low values of the loop gain, are proposed in this report. New simplified stability criteria have been developed which incorporate the changes in the canonic form of differential equations caused by the application of the zero-shifting technique. Other methods of constructing Liapunov\u27s functions for nonlinear control systems are presented in Chapter III, These include the work of Pliss, Aizerman and Krasovski. Numerous other procedures, which have been reported in literature, apply to only very special cases of automatic control systems. No attempt has been made to account for all of these special cases and the presentation of methods of constructing Liapunov’s functions is limited to only those which are more generally applicable. A pseudo-canonic transformation has been developed which enables one to find stability criteria of canonic systems without the use of complex variables. The results of this research indicate that the second method of Liapunov is a very powerfuI tool of exact stability analysis of nonlinear systems. Additional research, especially in the direction of the methods of construction of Liapunov’s functions, will not only yield new analysis and synthesis procedures, but also will aid in arriving at a set of meaningful performance specifications for nonlinear control systems

Individual crypt genetic heterogeneity and the origin of metaplastic glandular epithelium in human Barrett’s oesophagus

OBJECTIVES: Current models of clonal expansion in human Barrett's oesophagus are based upon heterogenous, flow-purified biopsy analysis taken at multiple segment levels. Detection of identical mutation fingerprints from these biopsy samples led to the proposal that a mutated clone with a selective advantage can clonally expand to fill an entire Barrett's segment at the expense of competing clones (selective sweep to fixation model). We aimed to assess clonality at a much higher resolution by microdissecting and genetically analysing individual crypts. The histogenesis of Barrett's metaplasia and neo-squamous islands has never been demonstrated. We investigated the oesophageal gland squamous ducts as the source of both epithelial sub-types. METHODS: Individual crypts across Barrett's biopsy and oesophagectomy blocks were dissected. Determination of tumour suppressor gene loss of heterozygosity patterns, p16 and p53 point mutations were carried out on a crypt-by-crypt basis. Cases of contiguous neo-squamous islands and columnar metaplasia with oesophageal squamous ducts were identified. Tissues were isolated by laser capture microdissection and genetically analysed. RESULTS: Individual crypt dissection revealed mutation patterns that were masked in whole biopsy analysis. Dissection across oesophagectomy specimens demonstrated marked clonal heterogeneity, with multiple independent clones present. We identified a p16 point mutation arising in the squamous epithelium of the oesophageal gland duct, which was also present in a contiguous metaplastic crypt, whereas neo-squamous islands arising from squamous ducts were wild-type with respect to surrounding Barrett's dysplasia. CONCLUSIONS: By studying clonality at the crypt level we demonstrate that Barrett's heterogeneity arises from multiple independent clones, in contrast to the selective sweep to fixation model of clonal expansion previously described. We suggest that the squamous gland ducts situated throughout the oesophagus are the source of a progenitor cell that may be susceptible to gene mutation resulting in conversion to Barrett's metaplastic epithelium. Additionally, these data suggest that wild-type ducts may be the source of neo-squamous islands

E-cadherin can limit the transforming properties of activating β-catenin mutations

Wnt pathway deregulation is a common characteristic of many cancers. But only Colorectal Cancer predominantly harbours mutations in APC, whereas other cancer types (hepatocellular carcinoma, solid pseudopapillary tumours of pancreas) have activating mutations in β-catenin (CTNNB1). We have compared the dynamics and the potency of β-catenin mutations in vivo. Within the murine small intestine (SI), an activating mutation of β-catenin took much longer to achieve a Wnt deregulation and acquire a crypt-progenitor-cell (CPC) phenotype than Apc or Gsk3 loss. Within the colon, a single activating mutation of β-catenin was unable to drive Wnt deregulation or induce the CPC phenotype. This ability of β-catenin mutation to differentially transform the SI versus the colon correlated with significantly higher expression of the β-catenin binding partner E-cadherin. This increased expression is associated with a higher number of E-cadherin:β-catenin complexes at the membrane. Reduction of E-cadherin synergised with an activating mutation of β-catenin so there was now a rapid CPC phenotype within the colon and SI. Thus there is a threshold of β-catenin that is required to drive transformation and E-cadherin can act as a buffer to prevent β-catenin accumulation