A techno-economic probabilistic approach to superheater lifetime determination

In the commonly used approach, the lifetime of a superheater is estimated by characteristic values of the production parameters and the operating conditions. In this approach, a lower bound for a superheater lifetime is based on some arbitrary safety factor that does not necessarily reflect real life, where unexpected failures do occur. The method proposed here suggests coping with this reality, by employing a techno-economic probabilistic approach. It comprises the following two models: • A probabilistic time to failure evaluation model that considers the variability of the lifetime determining parameters. • A model to optimise values of technical parameters and operating conditions and to determine a superheater’s optimal replacement policy, based on life cycle cost considerations. The proposed probabilistic time to failure evaluation model can help to identify the most influential parameters for planning for a minimal probability of failure. It is applied to a unique problematic steel T22 superheater of rather specific parameters: corrosion rate, the Larson Miller Parameter (LMP), diameter and wall thickness. Sensitivity analysis has shown that the dominant factor affecting variation in superheater lifetime is the variation in the LMP, while the effect of the other parameters is quite marginal. Decreasing the standard deviation of the LMP (by keeping a more uniform material) lowered the probability of failure. This resulted in a practical recommendation to perform periodical checks of the parameter wall thickness. We also tested the effect of changing the nominal values of these parameters on the lifetime distribution. Hence, we suggest that the selection of the nominal values should be based on life cycle cost considerations; and propose a model to calculate, for any given combination, the average life cycle cost. The latter model, the optimal parameters combination model, optimises the combination of changes in all the superheater’s parameters by minimising the average life cycle cost associated with the superheater. Demonstrating the usefulness of the proposed approach, in a problematic case, suggests that it can be beneficially employed in the more general case whenever the planned lifetime of a design is threatened

A role of mitochondrial complex II defects in genetic models of Huntington's disease expressing N-terminal fragments of mutant huntingtin.

Huntington's disease (HD) is a neurodegenerative disorder caused by an abnormal expansion of a CAG repeat encoding a polyglutamine tract in the huntingtin (Htt) protein. The mutation leads to neuronal death through mechanisms which are still unknown. One hypothesis is that mitochondrial defects may play a key role. In support of this, the activity of mitochondrial complex II (C-II) is preferentially reduced in the striatum of HD patients. Here, we studied C-II expression in different genetic models of HD expressing N-terminal fragments of mutant Htt (mHtt). Western blot analysis showed that the expression of the 30 kDa Iron-Sulfur (Ip) subunit of C-II was significantly reduced in the striatum of the R6/1 transgenic mice, while the levels of the FAD containing catalytic 70 kDa subunit (Fp) were not significantly changed. Blue native gel analysis showed that the assembly of C-II in mitochondria was altered early in N171-82Q transgenic mice. Early loco-regional reduction in C-II activity and Ip protein expression was also demonstrated in a rat model of HD using intrastriatal injection of lentiviral vectors encoding mHtt. Infection of the rat striatum with a lentiviral vector coding the C-II Ip or Fp subunits induced a significant overexpression of these proteins that led to significant neuroprotection of striatal neurons against mHtt neurotoxicity. These results obtained in vivo support the hypothesis that structural and functional alterations of C-II induced by mHtt may play a critical role in the degeneration of striatal neurons in HD and that mitochondrial-targeted therapies may be useful in its treatment

Stage and treatment variation with age in postmenopausal women with breast cancer: compliance with guidelines

Breast cancer-specific mortality is static in older women despite having fallen in younger age groups, possibly due to lack of screening and differences in treatment. This study compared stage and treatment between two cohorts of postmenopausal women (55–69 vs 470 years) in a single cancer network over 6 months. A total of 378 patients were studied (470: N ¼ 167, 55–69 years: N ¼ 210). Older women presented with more advanced disease (470: metastatic/locally advanced 12%, 55–69 years: 3%, Po0.01). Those with operable cancer had a worse prognosis (Nottingham Prognostic Index (NPI) 470: median NPI 4.4, 55–69 years: 4.25, Po0.03). These stage differences were partially explained by higher screening rates in the younger cohort. Primary endocrine therapy was used in 42% of older patients compared with 3% in the younger group (Po0.001). Older women with cancers suitable for breast conservation were more likely to choose mastectomy (470: 57.5% mastectomy rate vs 55–69 years: 20.6%, Po0.01). Nodal surgery was less frequent in older patients (470: 6.7% no nodal surgery, 55–69 years: 0.5%, Po0.01) and was more likely to be inadequate (470: 10.7% o4 nodes excised, 55–69 years: 3.4%, Po0.02). In summary, older women presented with more advanced breast cancer, than younger postmenopausal women and were treated less comprehensively

Interfirm relationships within the construction industry Towards the emergence of networks? A comparative study between France and the UK

SIGLEAvailable from British Library Document Supply Centre-DSC:DX196272 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Drosophila Rrp1 3'-exonuclease: demonstration of DNA sequence dependence and DNA strand specificity.

Drosophila Rrp1 (recombination repair protein 1) is a DNA repair enzyme whose nuclease activities include AP-endonuclease, 3'-exonuclease, 3'-phosphodiesterase and 3'-phosphatase. This study investigates the sequence specificity of the dsDNA 3'-exonuclease activity of Rrp1. We demonstrate that the activity is more efficient in purine-rich regions of dsDNA than in pyrimidine-rich regions. Rrp1 exonuclease activity is examined at 3'-terminal homopurine or homopyrimidine tracts, at junctions between purine- and pyrimidine-rich sequences and upon encountering repeated dinucleotide runs. The data show that purine-purine and 3'-pyrimidine-5'-purine dinucleotide bonds are cleaved faster than 3'-purine-5'-pyrimidine or pyrimidine-pyrimidine bonds. Thus, the base occupying the penultimate position in the 3'-terminal dinucleotide may be important in determining the relative efficiency of bond cleavage by Rrp1. These findings may reflect upon specific DNA-protein interactions in the enzyme active site

Vicious circles and imbalances in the construction industry

SIGLEAvailable from British Library Document Supply Centre-DSC:9350.837405(HWP/9712) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Variation in practice habits in the treatment of pediatric distal radius fractures.

Distal radius fractures are widespread in the pediatric population. Standardized treatment protocols have not been well defined. We sought to examine the diversity of current practice patterns in the treatment of these fractures by surveying hand, pediatric, and general orthopedic surgeons. Hand, pediatric, and general orthopedic surgeons were surveyed using an internet-based questionnaire on the management of pediatric distal radius fractures. Each surgeon was asked to select a criterion from among choices of 'acceptable' alignment criteria at the onset of the survey. Ten cases were then provided to represent a broad spectrum of injuries from minimally angulated torus fractures to complete, displaced fractures. In addition to the variation in injury pattern, the patients in the survey differed in age at the time of injury (3-15 years of age). For each case, surgeons were asked to select a preferred treatment, first on the basis of injury films, and then again after reviewing 1-week follow-up radiographs. A total of 781 surgeons completed the survey. In patients younger than 9 years of age, a residual sagittal angulation of 20° or less, coronal angulation of 10° or less, and 1 cm or less of bayonet apposition was deemed 'acceptable' by 88, 90, and 69% of respondents, respectively. In older patients, these percentages were 58, 64, and 29%, respectively. When specific cases were reviewed, 20.3% of surgeons recommended treatment different from their own theoretical 'acceptable' criteria. When subspecialty training was analyzed, hand surgeons and general orthopedic surgeons were 2.9 and 1.6 times more likely to recommend surgery, respectively, as compared with pediatric surgeons after viewing the initial radiograph. Private practice surgeons were 1.5 times more likely to recommend surgery compared with academic surgeons based on the initial injury radiographs. Our survey highlights the discordance between theoretical acceptable criteria of surgeons and their practice habits, as well as the substantial disparities in treatment recommendations based on subspecialty training. Further study is warranted to determine whether these variations in treatment affect patient outcomes. This survey is a level IV observational study

Variation in practice habits in the treatment of pediatric distal radius fractures.

Distal radius fractures are widespread in the pediatric population. Standardized treatment protocols have not been well defined. We sought to examine the diversity of current practice patterns in the treatment of these fractures by surveying hand, pediatric, and general orthopedic surgeons. Hand, pediatric, and general orthopedic surgeons were surveyed using an internet-based questionnaire on the management of pediatric distal radius fractures. Each surgeon was asked to select a criterion from among choices of 'acceptable' alignment criteria at the onset of the survey. Ten cases were then provided to represent a broad spectrum of injuries from minimally angulated torus fractures to complete, displaced fractures. In addition to the variation in injury pattern, the patients in the survey differed in age at the time of injury (3-15 years of age). For each case, surgeons were asked to select a preferred treatment, first on the basis of injury films, and then again after reviewing 1-week follow-up radiographs. A total of 781 surgeons completed the survey. In patients younger than 9 years of age, a residual sagittal angulation of 20° or less, coronal angulation of 10° or less, and 1 cm or less of bayonet apposition was deemed 'acceptable' by 88, 90, and 69% of respondents, respectively. In older patients, these percentages were 58, 64, and 29%, respectively. When specific cases were reviewed, 20.3% of surgeons recommended treatment different from their own theoretical 'acceptable' criteria. When subspecialty training was analyzed, hand surgeons and general orthopedic surgeons were 2.9 and 1.6 times more likely to recommend surgery, respectively, as compared with pediatric surgeons after viewing the initial radiograph. Private practice surgeons were 1.5 times more likely to recommend surgery compared with academic surgeons based on the initial injury radiographs. Our survey highlights the discordance between theoretical acceptable criteria of surgeons and their practice habits, as well as the substantial disparities in treatment recommendations based on subspecialty training. Further study is warranted to determine whether these variations in treatment affect patient outcomes. This survey is a level IV observational study