Enlarging the domain of attraction of stable MPC controllers, maintaining the output performance

This work presents an alternative way to formulate the stable Model Predictive Control (MPC) optimization problem that allows the enlargement of the domain of attraction, while preserving the controller performance. Based on the dual MPC that uses the null local controller, it proposed the inclusion of an appropriate set of slacked terminal constraints into the control problem. As a result, the domain of attraction is unlimited for the stable modes of the system, and the largest possible for the non-stable modes. Although this controller does not achieve local optimality, simulations show that the input and output performances may be comparable to the ones obtained with the dual MPC that uses the LQR as a local controller. (C) 2009 Elsevier Ltd. All rights reserved.

An evaluation of the Keep on Talking program for maintaining communication skills into old

Communication skills change with age as a result of sensory deficits, memory loss, and increasing word finding difficulties The Keep on Talking program (L. Hickson, H. Barnett, L. Worrall, & E. Yiu, 1994) was developed to assist older people to develop their own strategies for maintaining communication skills into old age. Two hundred and fifty-two healthy older people were recruited from the community and were assessed on a battery of communication assessments on entry to the study and at 1 year after entry. The experimental group (n = 120) participated in the 5-week group Keep on Talking program run by volunteers A further 130 control subjects were assessed only. The short-term effectiveness of the program was evaluated using a short knowledge based and attitudinal questionnaire and qualitative written feedback. At the I-year follow up, subjects were also asked whether they had taken any action as a result of the project. Results concluded that there was a significant difference between the number of correct questionnaire responses on the knowledge based items and the ratings on the attitudinal items pre- and postprogram questionnaire for the experimental subjects. Qualitative written feedback was positive with many participants remarking on the amount of information that they had acquired. Forty-eight experimental and 69 control subjects (n = 117) were assessed I year later, and there was a significant difference between the groups in terms of the number of subjects who reported having taken action as a result of the program. The Keep on Talking program increased knowledge about communication, produced a positive change in attitude toward the importance of communication, and encouraged participants to take action to maintain their communication skills. Maintaining communication skills may prevent social isolation. This simple 5-hour group program has been effective in empowering participants to maintain. their communication skills as they age.

Does maintaining green leaf area in sorghum improve yield under drought? I. Leaf growth and senescence

Production of sorghum [Sorghum bicolor (L.) Moench], an important cereal crop in semiarid regions of the world, is often limited by drought. When water is limiting during the grain-filling period, hybrids possessing the stay-green trait maintain more photosynthetically active leaves than hybrids not possessing this trait. To improve yield under drought, knowledge of the extent of genetic variation in green leaf area retention is required. Field studies were undertaken in north-eastern Australia on a cracking and self-mulching gray clay to determine the effects of water regime and hybrid on the components of green leaf area at maturity (GLAM). Nine hybrids varying in stay-green were grown under a fully irrigated control, postflowering water deficit, and terminal (pre- and postflowering) water deficit. Water deficit reduced GLAM by 67% in the terminal drought treatment compared with the fully irrigated control. Under terminal water deficit, hybrids possessing the B35 and KS19 sources of stay-green retained more GLAM (1260 cm(2) plant(-1)) compared with intermediate (780 cm(2) plant(-1)) and senescent (670 cm(2) plant(-1)) hybrids. RQL12 hybrids (KS19 source of stay-green) displayed delayed onset and reduced rate of senescence; A35 hybrids displayed only delayed onset. Visual rating of green leaf retention was highly correlated with measured GLAM, although this procedure is constrained by an inability to distinguish among the functional mechanisms determining the phenotype. Linking functional rather than phenotypic differences to molecular markers may improve the efficiency of selecting for traits such as stay-green.

Does maintaining green leaf area in sorghum improve yield under drought? II. Dry matter production and yield

Retention of green leaf area at maturity (GLAM), known as stay-green, is used as an indicator of postanthesis drought resistance in sorghum [Sorghum bicolor (L.) Moench] breeding programs in the USA and Australia. The critical issue is whether maintaining green leaves under postanthesis drought increases grain yield in stay-green compared with senescent hybrids. Field studies were undertaken in northeastern Australia on a cracking and self-mulching gay clay. Nine closely related hybrids varying in rate of leaf senescence were grown under two water-limiting regimes, post-flowering water deficit and terminal (pre- and postflowering) water deficit, and a fully irrigated control. Under terminal water deficit, grain yield tvas correlated positively with GLAM (r = 0.75**) and negatively with rate of leaf senescence (r = -0.74**). Grain yield also increased by approximate to 0.35 Mg ha(-1) for every day that onset of leaf senescence was delayed beyond 76 DAE in the water-limited treatments. Stay-green hybrids produced 47% more postanthesis biomass than their senescent counterparts (920 vs. 624 g m(-2)) under the terminal water deficit regime. No differences in grain yield were found among eight of the nine hybrids under fully irrigated conditions, suggesting that the stay-green trait did not constrain yield in the well-watered control. The results indicate that sorghum hybrids possessing the stay-green trait have a significant yield advantage under postanthesis drought compared with hybrids not possessing this trait.

Intermittent heparinised saline flushes for maintaining indwelling peripheral and central intravenous catheters in diabetic dogs

Intermittent low-dose heparinised saline flushes were found to be efficacious for maintaining patency of indwelling peripheral and central intravenous catheters in diabetic dogs. The catheters were flushed with 1 mL of 1 U/mL heparinised saline every two hours immediately following blood sample collection, or every 12 hours when not being used for sampling. Central catheters were flushed with saline solution first to clear the line before instillation of the heparinised saline. Patency of 54/57 (95%) of the peripheral catheters and 30/32 (94%) of the central catheters was achieved for up to 36 hours and five days, respectively. No phlebitis, or local or systemic infections were observed and, in each case, catheter failure was attributable to obstruction or extravasation. It is unlikely that there will be any contraindications to this flushing technique and its introduction may improve intravenous catheter survival and reduce catheter-associated complications in hospitalised dogs.

Can occupational therapy intervention play a part in maintaining independence and quality of life in older people? A randomised controlled trial Jeannine Liddle 1 , 2 , Lyn March 3 , Barbara Carfrae 4 , Terence Finnegan 5 , Jane Druce 6 , Jennifer Schwarz 7 Peter Brooks

The main objective of this study was to see if older people could maintain their quality of life and independence after their homes had been modified and they were using community services as recommended by an occupational therapist. There were 167 study participants aged 69 to 94 years from the Northern Sydney Area, After being assessed at home by an occupational therapist, 105 were randomly allocated to one of two groups, to either have or not have the occupational therapist's recommendations carried out, They were assessed again after six months, A third group did not require any intervention, This group was followed up by telephone and postal questionnaire at six months. The main outcome measures used were the Sickness Impact Profile, the Philadelphia Geriatric Center Morale Scale, the Life Satisfaction Index, assessment of Activities of Daily Living, the Health Assessment Questionnaire and change in residence. After six months there were no difference in outcomes among the three groups. Most study participants remained at a satisfactory level on each measure. Three people had died, One had moved to hostel care and one had moved to a nursing home. A further 14 from the group having no intervention had withdrawn from the study, A secondary objective of this study was to indicate the responsiveness of these outcome measures to change in the short term (over six months) in an elderly population. Twelve-month assessments are in progress and may indicate what to expect from these outcome measures in the medium term.

Maintaining clearance in peritoneal dialysis

Numerous studies have now established that there is a strong association between small solute clearance and improved outcomes in peritoneal dialysis (PD) patients. Preservation of both renal and peritoneal clearances is therefore of paramount importance, although very few trials have satisfactorily addressed this critical issue. Observational studies have suggested that the groups most at risk of loss of residual renal function are women, non-whites, diabetic patients, patients with congestive cardiac failure, patients who experience frequent episodes of peritonitis and, possibly, patients treated with automated PD (APD). There have been no controlled trials of renoprotective therapies in PD patients, but reasonable strategies for preventing renal functional decline include avoidance of nephrotoxins and infection, maintenance of adequate blood pressure, abstinence from smoking and possibly administration of angiotensin-converting enzyme inhibitors and/or calcium channel blockers. In contrast, peritoneal small solute removal can be maximized by augmenting fill volume, increasing exchange frequency and using either long-dwell continuous ambulatory PD (CAPD) or short-dwell (APD) therapies to suit individual patients' transport characteristics. Tidal PD may additionally increase solute clearance, although studies have reported conflicting findings. Preservation of membrane function may be achieved by minimizing episodes of peritonitis and avoiding hypertonic glucose exchanges. Newer peritoneal dialysates, such as icodextrin, amino acids, bicarbonate-buffered solutions and aldehyde-poor fluids, are more biocompatible in experimental models of PD, but their long-term clinical safety and efficacy have not yet been established by clinical trials. Moreover, no trials have demonstrated an independent effect of peritoneal clearance on patient outcomes. Further studies determining the relative value of renal and peritoneal clearances are therefore urgently required in order to optimize dialytic adequacy for PD patients.

Maintaining muscle mass during extended disuse: Aestivating frogs as a model species

Prolonged muscle disuse in vertebrates can lead to a pathological change resulting in muscle wasting and a loss of muscle strength. In this paper, we review muscle disuse atrophy in the vertebrates and examine the factors that influence the magnitude of the atrophic response during extended periods of inactivity, both artificially imposed (e.g. limb immobilisation) and naturally occurring, such as the quiescence associated with dormancy (e.g. hibernation and aestivation). The severity of muscle atrophy is positively correlated with mass-specific metabolic rate, and the metabolic depression that occurs during dormancy would appear to have a protective role, reducing or preventing muscle atrophy despite periods of inactivity lasting 6-9 months. In the light of these findings, the role of reactive oxygen species and antioxidants during muscle disuse is emphasised.

Printed advice on initiating and maintaining breastfeeding in mid-20th-century Queensland

This article, which is part of a larger historical study of infant-feeding advice received by mothers in Queensland, Australia, identifies and examines print materials that were used by mothers, or that influenced other texts, during the postwar period from 1945 to 1965. The texts are described within the context of their environmental influences and the medical knowledge and research of the time to assess what effect, if any, these latter materials had on the established system of infant-feeding advice. Two innovations that were employed are the use of interviews to identify the most-used texts and the comparison of popular advice books with medical journal material.

Maintaining image quality for paediatric chest CTs while lowering dose: FBP versus SAFIRE

Objectives: Children have a greater risk from radiation, per unit dose, due to increased radiosensitivity and longer life expectancies. It is of paramount importance to reduce the radiation dose received by children. This research concerns chest CT examinations on paediatric patients. The purpose of this study was to compare the image quality and the dose received from imaging with images reconstructed with filtered back projection (FBP) and five strengths of Sinogram-Affirmed Iterative Reconstruction (SAFIRE). Methods: Using a multi-slice CT scanner, six series of images were taken of a paediatric phantom. Two kVp values (80 and 110), 3 mAs values (25, 50 and 100) and 2 slice thicknesses (1 mm and 3 mm) were used. All images were reconstructed with FBP and five strengths of SAFIRE. Ten observers evaluated visual image quality. Dose was measured using CT-Expo. Results: FBP required a higher dose than all SAFIRE strengths to obtain the same image quality for sharpness and noise. For sharpness and contrast image quality ratings of 4, FBP required doses of 6.4 and 6.8 mSv respectively. SAFIRE 5 required doses of 3.4 and 4.3 mSv respectively. Clinical acceptance rate was improved by the higher voltage (110 kV) for all images in comparison to 80 kV, which required a higher dose for acceptable image quality. 3 mm images were typically better quality than 1 mm images. Conclusion: SAFIRE 5 was optimal for dose reduction and image quality.

A narrative review on the reduction of effective dose to a paediatric patient by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

This paper reviews the literature for lowering of dose to paediatric patients through use of exposure factors and additional filtration. Dose reference levels set by The International Commission on Radiological Protection (ICRP) will be considered. Guidance was put in place in 1996 requires updating to come into line with modern imaging equipment. There is a wide range of literature that specifies that grids should not be used on paediatric patients. Although much of the literature advocates additional filtration, contrasting views on the relative benefits of using aluminium or copper filtration, and their effects on dose reduction and image quality can vary. Changing kVp and mAs has an effect on the dose to the patient and image quality. Collimation protects adjacent structures whilst reducing scattered radiation.

Reducing effective dose to a paediatric phantom by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

Purpose: To determine whether using different combinations of kVp and mAs with additional filtration can reduce the effective dose to a paediatric phantom whilst maintaining diagnostic image quality. Methods: 27 images of a paediatric AP pelvis phantom were acquired with different kVp, mAs and additional copper filtration. Images were displayed on quality controlled monitors with dimmed lighting. Ten diagnostic radiographers (5 students and 5 experienced radiographers) had eye tests to assess visual acuity before rating the images. Each image was rated for visual image quality against a reference image using 2 alternative forced choice software using a 5-point Likert scale. Physical measures (SNR and CNR) were also taken to assess image quality. Results: Of the 27 images rated, 13 of them were of acceptable image quality and had a dose lower than the image with standard acquisition parameters. Two were produced without filtration, 6 with 0.1mm and 5 with 0.2mm copper filtration. Statistical analysis found that the inter-rater and intra-rater reliability was high. Discussion: It is possible to obtain an image of acceptable image quality with a dose that is lower than published guidelines. There are some areas of the study that could be improved. These include using a wider range of kVp and mAs to give an exact set of parameters to use. Conclusion: Additional filtration has been identified as amajor tool for reducing effective dose whilst maintaining acceptable image quality in a 5 year old phantom.

Role of biotic interactions in generating and maintaining biodiversity

Dissertation presented to obtain the Ph.D degree in Biology.