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Molecular regulation of sucrose catabolism and sugar transport for development, defence and phloem function
No full textSucrose (Suc) is the major end product of photosynthesis in mesophyll cells of most vascular plants. It is loaded into phloem of mature leaves for long-distance translocation to non-photosynthetic organs where it is unloaded for diverse uses. Clearly, Suc transport and metabolism is central to plant growth and development and the functionality of the entire vascular system. Despite vast information in the literature about the physiological roles of individual sugar metabolic enzymes and transporters, there is a lack of systematic evaluation about their molecular regulation from transcriptional to post-translational levels. Knowledge on this topic is essential for understanding and improving plant development, optimizing resource distribution and increasing crop productivity. We therefore focused our analyses on molecular control of key players in Suc metabolism and transport, including: (i) the identification of promoter elements responsive to sugars and hormones or targeted by transcription factors and microRNAs degrading transcripts of target genes; and (ii) modulation of enzyme and transporter activities through protein-protein interactions and other post-translational modifications. We have highlighted major remaining questions and discussed opportunities to exploit current understanding to gain new insights into molecular control of carbon partitioning for improving plant performance
Protein interaction screening identifies SH3RF1 as a new regulator of FAT1 protein levels
No full textMutations and ectopic FAT1 cadherin expression are implicated in a broad spectrum of diseases ranging from developmental disorders to cancer. The regulation of FAT1 and its downstream signalling pathways remain incompletely understood. We hypothesized that identification of additional proteins interacting with the FAT1 cytoplasmic tail would further delineate its regulation and function. A yeast two-hybrid library screen carried out against the juxtamembrane region of the cytoplasmic tail of FAT1 identified the E3 ubiquitin-protein ligase SH3RF1 as the most frequently recovered protein-binding partner. Ablating SH3RF1 using siRNA increased cellular FAT1 protein levels and stabilized expression at the cell surface, while overexpression of SH3RF1 reduced FAT1 levels. We conclude that SH3RF1 acts as a negative post-translational regulator of FAT1 levels
Effects of initial conditions in decaying turbulence generated by passive grids
No full textThe effects of initial conditions on grid turbulence are investigated for low to moderate Reynolds numbers. Four grid geometries are used to yield variations in initial conditions and a secondary contraction is introduced to improve the isotropy of the turbulence. The hot-wire measurements, believed to be the most detailed to date for this flow, indicate that initial conditions have a persistent impact on the large-scale organization of the flow over the length of the tunnel. The power-law coefficients, determined via an improved method, also depend on the initial conditions. For example, the power-law exponent m is affected by the various levels of large-scale organization and anisotropy generated by the different grids and the shape of the energy spectrum at low wavenumbers. However, the results show that these effects are primarily related to deviations between the turbulence produced in the wind tunnel and true decaying homogenous isotropic turbulence (HIT). Indeed, when isotropy is improved and the intensity of the large-scale periodicity, which is primarily associated with round-rod grids, is decreased, the importance of initial conditions on both the character of the turbulence and m is diminished. However, even in the case where the turbulence is nearly perfectly isotropic, m is not equal to −1, nor does it show an asymptotic trend in x towards this value, as suggested by recent analysis. Furthermore, the evolution of the second- and third-order velocity structure functions satisfies equilibrium similarity only approximately
Use of low-pressure storage to improve the quality of tomatoes
No full textFreshly harvested vine-ripened tomatoes (Solanum lycopersicum cv. Neang Pich) were stored at low pressure (4 kPa) at 10°C for 11 days with 100% RH. Fruit quality was examined upon removal and after being transferred to normal atmosphere (101 kPa) at 20°C for 3 days. Weight loss was significantly lower in fruits which were stored at low pressure (4 kPa) than in fruits that were stored at regular atmosphere (101 kPa) at 10°C. Fruits that were stored at low pressure (4 kPa) reduced calyx browning by 12.5%, and calyx rots by 16%, compared to fruits that were stored at regular atmosphere (101 kPa) at 10°C. Fruit firmness was not significantly different between fruits stored at low pressures (4 kPa) and the normal atmosphere (101 kPa), with an average firmness of 14 N after fruits were stored at 10°C for 11 days. There was no difference in the SSC/TA ratio. The results suggest that a low pressure of 4 kPa at 10°C has potential as an alternative, non-chemical postharvest treatment to improve tomato quality during storage
Nursing responses and interventions for episodes of adolescent distress in an acute child and adolescent mental health inpatient unit: an interpretive descriptive study
No full textAdolescents who experience acute mental health problems are often admitted to acute child and adolescent mental health inpatient units for care and treatment. Nurses, at times, are required to respond to episodes of distress that adolescents experience during the admission period. Nurses engage with young people who exhibit maladaptive and often high-risk behaviours that require appropriate interventions to help alleviate their distress. The majority of research conducted on child and adolescent mental health has focussed on quantitative methodologies examining the demographic and diagnostic characteristics of young people, treatment outcome measures, or the rate of coercive interventions such as seclusion, physical restraint, and pm medication. There are numerous contextual factors that influence nursing practice. This study aimed to understand which nursing responses and interventions were most helpful in resolving distress for adolescents admitted to an acute child and adolescent mental health inpatient unit. An interpretive descriptive study was undertaken to explore the contextual and experiential components of providing nursing responses and interventions for episodes of adolescent distress. This approach is suited to the subtle but complex nature of the clinical setting and understanding the interactions between nurses and adolescents. Following a review of the relevant literature, and documentation of the researcher’s assumptions, two methods were used to collect data. Non-participant observations focussing on interactions between adolescents (aged 13-17) experiencing episodes of distress and nurses who responded to them were conducted. The second-stage of data collection, semi-structured interviews (n = 10) were conducted with nurses working in the inpatient unit. Both data sets were analysed using Thorne’s three-stage interpretive descriptive method. The open, axial and selective coding process produced themes and sub-themes that provided a deeper understanding of how adolescents experience episodes of distress in the acute inpatient mental health setting, and the cultural and contextual factors that not only trigger these episodes, but also on the nurses who provide care for them at these times. Young people experienced and displayed their distress in numerous ways and nurses used a range of responses and interventions to assist them. The importance of a person-centred approach was evident and there were multiple cultural and contextual factors that influenced both the young people’s experiences during the admission, and nursing practices. An observation model of responding to adolescent distress, and a clinical tool that integrates findings from both data sets were developed as a result of this study. These will provide the impetus for education and training, policy and organisational change, and future research in this area of mental health nursing care
The computations that support simple decision-making: a comparison between the diffusion and urgency-gating models
No full textWe investigate a question relevant to the psychology and neuroscience of perceptual decision-making: whether decisions are based on steadily accumulating evidence, or only on the most recent evidence. We report an empirical comparison between two of the most prominent examples of these theoretical positions, the diffusion model and the urgency-gating model, via model-based qualitative and quantitative comparisons. Our findings support the predictions of the diffusion model over the urgency-gating model, and therefore, the notion that evidence accumulates without much decay. Gross qualitative patterns and fine structural details of the data are inconsistent with the notion that decisions are based only on the most recent evidence. More generally, we discuss some strengths and weaknesses of scientific methods that investigate quantitative models by distilling the formal models to qualitative predictions
Computer-animated stimuli to measure motion sensitivity: constraints on signal design in the Jacky dragon
No full textIdentifying perceptual thresholds is critical for understanding the mechanisms that underlie signal evolution. Using computer-animated stimuli, we examined visual speed sensitivity in the Jacky dragon Amphibolurus muricatus, a species that makes extensive use of rapid motor patterns in social communication. First, focal lizards were tested in discrimination trials using random-dot kinematograms displaying combinations of speed, coherence, and direction. Second, we measured subject lizards’ ability to predict the appearance of a secondary reinforcer (1 of 3 different computer-generated animations of invertebrates: cricket, spider, and mite) based on the direction of movement of a field of drifting dots by following a set of behavioural responses (e.g., orienting response, latency to respond) to our virtual stimuli. We found an effect of both speed and coherence, as well as an interaction between these 2 factors on the perception of moving stimuli. Overall, our results showed that Jacky dragons have acute sensitivity to high speeds. We then employed an optic flow analysis to match the performance to ecologically relevant motion. Our results suggest that the Jacky dragon visual system may have been shaped to detect fast motion. This pre-existing sensitivity may have constrained the evolution of conspecific displays. In contrast, Jacky dragons may have difficulty in detecting the movement of ambush predators, such as snakes and of some invertebrate prey. Our study also demonstrates the potential of the computer-animated stimuli technique for conducting nonintrusive tests to explore motion range and sensitivity in a visually mediated species
Parenting stress and depression in asthmatic mothers: relationships to infant development
No full textBackground: Large, separate bodies of literature demonstrate that both maternal psychological distress and asthma represent significant pathways through which infant development may be adversely affected. However, the combined, longer term effects of these phenomena on infant development are not well understood. Method: Mother-infant dyads were recruited as part of the Breathing for Life: Infant Development Trial. 31 asthmatic mothers and their infant were recruited at 6 weeks postpartum, when parenting stress and postnatal depression were measured using the Parenting Stress Index (Short Form) and the Edinburgh Postnatal Depression Scale. At six months, mother-infant dyads were tested again, using the Bayley Scales of Infant Development-III. Results: Higher scores of maternal depression at six weeks postpartum predicted poorer expressive language and adaptive behaviour skills of infants at six months. Additionally, higher levels of parenting stress at 6 weeks predicted poorer social emotional skills at 6 months. Asthmatic mothers also had significantly higher levels of postnatal depression, but significantly lower levels of parenting stress, compared to norms. Conclusion: These results help to describe the particular mental health status of asthmatic mothers, and how this is associated with infant developmental prospects. They suggest that both maternal stress and depression may be contributing to poorer infant outcomes across a range of domains; specifically, social-emotional, adaptive behaviour and expressive language development. Limitations and implications of these results are discussed. Future studies are encouraged to further explore the mechanisms through which asthma and maternal psychological distress affect infant development
Attachment strength and relationship expectancies in the prediction of adolescent stress and depression
No full textInterpersonal relationships are the recent focus of research identifying protective factors in adolescent psychological health. Using an attachment theory perspective, this study examines the relationship of normative attachment strength and individual differences in attachment expectancies on self-reports of depression and stress in 511 Australian high school students. Attachment reorganization was demonstrated but only father attachment uniquely predicted self-reported stress. Age moderated the relationships between peers and depression and stress among romantically involved adolescents. Individual differences in attachment styles, particularly anxious attachment, were most predictive of adolescent psychological health. These findings highlight the complexity of adolescent attachment relationships and suggest that interventions target both normative and individual factors in adolescent development to enhance adolescent psychological health
Application of calcium looping for heat generation and CO₂ enrichment in greenhouses
No full textGreenhouses typically employ conventional natural gas burners to meet the heat demand especially during cold winter nights and make use of additional carbon dioxide (CO2) to increase the CO2concentration above the atmospheric levels, thereby, accelerating the photosynthesis process and plant growth. As an alternative, this thesis describes a novel Greenhouse Calcium Looping (GCL) process which offers a cost effective solution for satisfying both heat and CO2 demands of modern greenhouses. More specifically, the GCL process can produce significant quantity of heat during night-time through an exothermic carbonation reaction between calcium oxide (CaO) particles and the CO2 emitted by growing plants. The resulting calcium carbonate (CaCO3) particles are then calcined during day-time releasing their CO2 content so that the photosynthesis process can be enhanced. The carbonation-calcination cycle is then repeated again. Interestingly, the greenhouse calcium looping (GCL) process is found to have better efficiencies and nearly zero CO2 emission profile compared to other conventional processes. However, so far, the optimum conditions, i.e. temperature and pressure, for providing the required heat and CO2 to the greenhouses in the GCL process are not clear. This includes also finding out how much CaO inventory is required for fulfilling the requirements of greenhouses? Accordingly, the main objective of this study is to find out the feasibility of the GCL process using Aspen Plus simulator software and establish the optimum conditions of the GCL process using Aspen Plus and experimental data. The conceptual design of greenhouse calcium looping process was carried out in the Aspen Plus® v 7.3 simulator. The process simulations carried out in Aspen indicated that the GCL process theoretically contributes to net zero emission of carbon dioxide given that the CO2 released by plants over the night cycle are absorbed again during the day cycle through the photosynthesis. Moreover, in a scenario modelling study compared to the conventional natural gas burner system, the heat duty requirements in the GCL process were found to reduce by as much as 72%.
Unique conditions of the GCL process (low temperature and low CO2 partial pressure) led to determination of the intrinsic carbonation reaction kinetic parameters in a temperature range of 400 to 500 oC and CO2 partial pressures of 0.05 to 0.1% (500 to 1000 ppm) which were carried out experimentally via a thermogravimetric analyser (TGA). Various gas-solid reaction mechanisms were considered to determine the best reaction mechanism for the carbonation reaction. Moreover, the activation energy and pre-exponential factor of the carbonation reaction were established. The derived kinetic parameters were used in Aspen Plus® to establish the optimum carbonator size considering an RPlug unit. The required size of the reactor decreased with an increase in the operating temperature of the reactor. Exergy analysis revealed that the carbonation process in the GCL technology boasted an overall exergetic efficiency of 80%. The calcination reaction part of the GCL process was also studied in a TGA to determine its intrinsic kinetic parameters. The experimental results showed that the calcination reaction in unique operational conditions of the GCL process (e.g. a temperature range of 600 to 800 oC and CO2 partial pressure of 400 to 1600 ppm) follows zero order. Similar to the carbonation part, various models were analysed to find out the most appropriate model predicting the calcination reaction in the GCL process. The derived kinetic parameters were used in Aspen Plus® v 7.3 to establish the optimum carbonator volume considering an RPlug unit which increased with an increase in air circulation rate and size of the greenhouse. To obtain a practical overview of the energy efficiency of the calcination reaction in the GCL process, an exergy analysis was conducted which highlighted an overall exergetic efficiency of 85%. The full cyclic carbonation/calcination reactions were also studied in a lab-scale fluidised bed reactor to verify the technical viability of the complete process (rather than half cycles) but more importantly to determine the apparent reaction kinetic parameters needed in the design of large-scale systems. It was found that after 3 cycles, the CO2capture capacity of CaO sorbents in the GCL process were more than that of those used for post-combustion capture of CO2in typical fossil fuelled power plants. At the 10th cycle, the reaction conversion in the GCL process was about 40% more than that used in typical fossil fuelled power plants. SEM photos also confirmed this higher maintenance capacity of CaO sorbent in the GCL process compared to the sorbents used in typical fossil fuelled power plants. The kinetic parameters of the carbonation reaction occurred in a small FBR were also determined in operational conditions of the GCL process (e.g. a low temperature range of 400 to 500 oC and a low CO2 partial pressure range of 600 to 2000 ppm). As expected there was a discrepancy between the activation energy and pre-exponential factor of the carbonation reaction derived in lab-scale FBR and TGA experiments. This is related to the fact that because of small test samples the TGA data are independent of heat and mass transfer (diffusional) limitations whereas the FBR represent a more realistic situation where data is in fact influenced by diffusional heat and mass transfer processes