42 research outputs found
On the diagonal subalgebra of an Ext algebra
No full textAbstractLet R be a Koszul algebra over a field k and M be a linear R-module. We study a graded subalgebra ΔM of the Ext-algebra ExtR⁎(M,M) called the diagonal subalgebra and its properties. Applications to the Hochschild cohomology ring of R and to periodicity of linear modules are given. Viewing R as a linear module over its enveloping algebra, we also show that ΔR is isomorphic to the graded center of the Koszul dual of R.When R is selfinjective and not necessarily graded, we study connections between periodic modules M, complexity of M and existence of non-nilpotent elements of positive degree in the Ext-algebra of M. Characterizations of periodic algebras are given
A systematic review of evidence on malignant spinal metastases : natural history and technologies for identifying patients at high risk of vertebral fracture and spinal cord compression
No full textBackground: Spinal metastases can lead to significant morbidity and reduction in quality of life due to spinal cord compression (SCC). Between 5% and 20% of patients with spinal metastases develop metastatic spinal cord compression during the course of their disease. An early study estimated average survival for patients with SCC to be between 3 and 7 months, with a 36% probability of survival to 12 months. An understanding of the natural history and early diagnosis of spinal metastases and prediction of collapse of the metastatic vertebrae are important.
Objective: To undertake a systematic review to examine the natural history of metastatic spinal lesions and to identify patients at high risk of vertebral fracture and SCC.
Data sources: The search strategy covered the concepts of metastasis, the spine and adults. Searches were undertaken from inception to June 2011 in 13 electronic databases [MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations; EMBASE; Cochrane Database of Systematic Reviews; Cochrane Central Register of Controlled Trials (CENTRAL); Database of Abstracts of Reviews of Effects (DARE), NHS Economic Evaluation Database (NHS EED), HTA databases (NHS Centre for Reviews and Dissemination); Science Citation Index and Conference Proceedings (Web of Science); UK Clinical Research Network (UKCRN) Portfolio Database; Current Controlled Trials; ClinicalTrials.gov].
Review methods: Titles and abstracts of retrieved studies were assessed by two reviewers independently. Disagreement was resolved by consensus agreement. Full data were extracted independently by one reviewer. All included studies were reviewed by a second researcher with disagreements resolved by discussion. A quality assessment instrument was used to assess bias in six domains: study population, attrition, prognostic factor measurement, outcome measurement, confounding measurement and account, and analysis. Data were tabulated and discussed in a narrative review. Each tumour type was looked at separately.
Results: In all, 2425 potentially relevant articles were identified, of which 31 met the inclusion criteria. No study examined natural history alone. Seventeen studies reported retrospective data, 10 were prospective studies, and three were other study designs. There was one systematic review. There were no randomised controlled trials (RCTs). Approximately 5782 participants were included. Sample sizes ranged from 41 to 859. The age of participants ranged between 7 and 92 years. Types of cancers reported on were lung alone (n= 3), prostate alone (n= 6), breast alone (n= 7), mixed cancers (n= 13) and unclear (n= 1). A total of 93 prognostic factors were identified as potentially significant in predicting risk of SCC or collapse. Overall findings indicated that the more spinal metastases present and the longer a patient was at risk, the greater the reported likelihood of development of SCC and collapse. There was an increased risk of developing SCC if a cancer had already spread to the bones. In the prostate cancer studies, tumour grade, metastatic load and time on hormone therapy were associated with increased risk of SCC. In one study, risk of SCC before death was 24%, and 2.37 times greater with a Gleason score 7 than with a score of < 7 (p= 0.003). Other research found that patients with six or more bone lesions were at greater risk of SCC than those with fewer than six lesions [odds ratio (OR) 2.9, 95% confidence interval (CI) 1.012 to 8.35, p= 0.047]. For breast cancer patients who received a computerised tomography (CT) scan for suspected SCC, multiple logistic regression in one study identified four independent variables predictive of a positive test: bone metastases 2 years (OR 3.0 95% CI 1.2 to 7.6; p= 0.02); metastatic disease at initial diagnosis (OR 3.4, 95% CI 1.0 to 11.4; p= 0.05); objective weakness (OR 3.8, 95% CI 1.5 to 9.5; p= 0.005); and vertebral compression fracture on spine radiograph (OR 2.6, 95% CI 1.0 to 6.5; p= 0.05). A further study on mixed cancers, among patients who received surgery for SCC, reported that vertebral body compression fractures were associated with presurgery chemotherapy (OR 2.283, 95% CI 1.064 to 4.898; p= 0.03), cancer type [primary breast cancer (OR 4.179, 95% CI 1.457 to 11.983; p= 0.008)], thoracic involvement (OR 3.505, 95% CI 1.343 to 9.143; p= 0.01) and anterior cord compression (OR 3.213, 95% CI 1.416 to 7.293; p= 0.005).
Limitations: Many of the included studies provided limited information about patient populations and selection criteria and they varied in methodological quality, rigour and transparency. Several studies identified type of cancer (e.g. breast, lung or prostate cancer) as a significant factor in predicting SCC, but it remains difficult to determine the risk differential partly because of residual bias. Consideration of quantitative results from the studies does not easily allow generation of a coherent numerical summary, studies were heterogeneous especially with regard to population, results were not consistent between studies, and study results almost universally lacked corroboration from other independent studies.
Conclusion: No studies were found which examined natural history. Overall burden of metastatic disease, confirmed metastatic bone involvement and immediate symptomatology suggestive of spinal column involvement are already well known as factors for metastatic SCC, vertebral collapse or progression of vertebral collapse. Although we identified a large number of additional possible prognostic factors, those which currently offer the most potential are unclear. Current clinical consensus favours magnetic resonance imaging and CT imaging modalities for the investigation of SCC and vertebral fracture. Future research should concentrate on: (1) prospective randomised designs to establish clinical and quality-of-life outcomes and cost-effectiveness of identification and treatment of patients at high risk of vertebral collapse and SCC; (2) Service Delivery and Organisation research on magnetic resonance imaging (MRI) scans and scanning (in tandem with research studies on use of MRI to monitor progression) in order to understand best methods for maximising use of MRI scanners; and (3) investigation of prognostic algorithms to calculate probability of a specified event using high-quality prospective studies, involving defined populations, randomly selected and clearly identified samples, and with blinding of investigators
High diagnostic yield of tuberculosis from screening urine samples from HIV-infected patients with advanced immunodeficiency using the Xpert MTB/RIF assay.
No full text: ABSTRACT:: We determined the diagnostic yield of the Xpert MTB/RIF assay for tuberculosis (TB) when testing small volumes of urine from ambulatory HIV-infected patients prior to starting antiretroviral therapy (ART) in South Africa. Compared to a gold standard of sputum culture, the sensitivity of urine Xpert among those with CD4 cell counts of <50, 50-100 and >100 cells/?L were 44.4%, 25.0% and 2.7% (P=0.001), respectively. Urine Xpert testing provides a means of rapid TB diagnosis in patients with advanced immunodeficiency and poor prognosis. These data are indicative of high rates of TB dissemination and renal involvement in this clinical population
Incidence of bullying and victimisation among adolescents in New Zealand
No full textBullying and victimisation are highly prevalent among young people, and both bullies and victims exhibit negative outcomes (Stassen Berger, 2007). Adolescents are greatly involved in bullying and experience particularly adverse outcomes in comparison with children (Kim & Leventhal, 2008; Simon-Davies, 2011). Furthermore bullying phenomena are under-researched in New Zealand samples. This paper aims to describe the nature of bullying and victimisation in a large sample of New Zealand adolescents and compare the findings to results from international samples. Four types of bullying will be assessed: traditional bullying inside the school, traditional bullying outside the school, cyber bullying via text message and cyber bullying via the internet. The same four types of victimisation will also be assessed
The role of empathy in improving SEL skills among educators and sudents in era of COVID-19
No full textFirst author draf
3D induction log modelling with integral equation method and domain decomposition preconditioning
No full textThe deployment of electromagnetic (EM) induction tools while drilling is one
of the standard routines for assisting the geosteering decision-making process.
The conductivity distribution obtained through the inversion of the EM
induction log can provide important information about the geological structure
around the borehole. To image the 3D geological structure in the subsurface, 3D
inversion of the EM induction log is required. Because the inversion process is
mainly dependent on forward modelling, the use of fast and accurate forward
modelling is essential. In this paper, we present an improved version of the
integral equation (IE) based modelling technique for general anisotropic media
with domain decomposition preconditioning. The discretised IE after domain
decomposition equals a fixed-point equation that is solved iteratively with
either the block Gauss-Seidel or Jacobi preconditioning. Within each iteration,
the inverse of the block matrix is computed using a Krylov subspace method
instead of a direct solver. An additional reduction in computational time is
obtained by using an adaptive relative residual stopping criterion in the
iterative solver. Numerical experiments show a maximum reduction in
computational time of 35 per cent compared to solving the full-domain IE with a
conventional GMRES solver. Additionally, the reduction of memory requirement
for covering a large area of the induction tool sensitivity enables
acceleration with limited GPU memory. Hence, we conclude that the domain
decomposition method is improving the efficiency of the IE method by reducing
the computation time and memory requirement.Comment: This article is a manuscript submitted to Geophysical Journal
Internationa
Host iron binding proteins acting as niche indicators for Neisseria meningitidis
No full textThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited - Copyright @ 2009 Jordan, Saunders.Neisseria meningitidis requires iron, and in the absence of iron alters its gene expression to increase iron acquisition and to make the best use of the iron it has. During different stages of colonization and infection available iron sources differ, particularly the host iron-binding proteins haemoglobin, transferrin, and lactoferrin. This study compared the transcriptional responses of N. meningitidis, when grown in the presence of these iron donors and ferric iron, using microarrays. Specific transcriptional responses to the different iron sources were observed, including genes that are not part of the response to iron restriction. Comparisons between growth on haemoglobin and either transferrin or lactoferrin identified changes in 124 and 114 genes, respectively, and 33 genes differed between growth on transferrin or lactoferrin. Comparison of gene expression from growth on haemoglobin or ferric iron showed that transcription is also affected by the entry of either haem or ferric iron into the cytoplasm. This is consistent with a model in which N. meningitidis uses the relative availability of host iron donor proteins as niche indicators. Growth in the presence of haemoglobin is associated with a response likely to be adaptive to survival within the bloodstream, which is supported by serum killing assays that indicate growth on haemoglobin significantly increases survival, and the response to lactoferrin is associated with increased expression of epithelial cell adhesins and oxidative stress response molecules. The transferrin receptor is the most highly transcribed receptor and has the fewest genes specifically induced in its presence, suggesting this is the favoured iron source for the bacterium. Most strikingly, the responses to haemoglobin, which is associated with unrestricted growth, indicates a low iron transcriptional profile, associated with an aggressive phenotype that may be adaptive to access host iron sources but which may also underlie the lethal features of meningococcal septicaemia, when haemoglobin may become a major source of iron.This study is funded by the EPA Cephalosporin Trust; and the Computational Biology Research Group (CBRG)
