200 research outputs found

    Seismic Anisotropy and Stress of the Canterbury Plains

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    The Mѡ=7.1 Darfield (Canterbury) earthquake struck on 4 September 2010, approximately 45 km west of Christchurch, New Zealand. It revealed a previously unknown fault (the Greendale fault) and caused billions of dollars of damage due to high peak ground velocities and extensive liquefaction. It also triggered the Mw=6.3 Christchurch earthquake on 22 February 2011, which caused further damage and the loss of 185 lives. The objective of this research was to determine the relationship between stress and seismic properties in a seismically active region using manually-picked P and S wave arrival times from the aftershock sequence between 8 September 2010-13 January 2011 to estimate shear-wave splitting (SWS) parameters, VP =VS-ratios, anisotropy (delay-time tomography), focal mechanisms, and tectonic stress on the Canterbury plains. The maximum horizontal stress direction was highly consistent in the plains, with an average value of SHmax=116 18 . However, the estimates showed variation in SHmax near the fault, with one estimate rotating by as much as 30° counter-clockwise. This suggests heterogeneity of stress at the fault, though the cause remains unclear. Orientations of the principal stresses predominantly indicate a strike-slip regime, but there are possible thrust regimes to the west and north/east of the fault. The SWS fast directions (ø) on the plains show alignment with SHmax at the majority of stations, indicating stress controlled anisotropy. However, structural effects appear more dominant in the neighbouring regions of the Southern Alps and Banks Peninsula

    Salt concentration and salty taste perception in Chardonnay and Shiraz wines from own roots and different rootstocks under saline irrigation

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    Salty taste can adversely affect the marketability of wine. To further examine salty taste, basic compositional and sensory assessment was conducted on ‘Chardonnay’ and ‘Shiraz’ wines produced from vines irrigated with salty water with a mean electrical conductivity of 1.5 dS m-1. Vines of the cultivars on own roots and on up to five rootstocks that differed in capacity for chloride and sodium exclusion were used. The sensory attributes salty and viscosity were enhanced for the ‘Chardonnay’ wine from K51-40 rootstock with elevated chloride and sodium concentrations of 407.4 and 374.2 mg L-1, respectively, and a potassium concentration of 470.1 mg L-1, but not affected in ‘Shiraz’ wine from K51-40 with concentrations of 274.1, 130.5 and 1,110 mg L-1, respectively. The salty and viscosity attributes in the ‘Chardonnay’ wine from K51-40 were closely associated and approximately equally correlated with the concentration of chloride and sodium, with the wine also having lower acidity and a higher overall fruit aroma. The chloride concentration in wine that aligns with perception of salty taste by a trained panel may be similar between a white and red wine. Wine chloride concentration above approximately 400 mg L-1 appears linked with, and a potential indicator of, salty taste, however the specific contribution of sodium and potassium requires further study

    Evaluating the Effectiveness of Using Thiel Soft-Embalmed Donors to Teach the Female Pelvic Exam to Medical Students

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    At the Quillen College of Medicine, first year medical students are taught how to perform the female pelvic exam as part of the “Introduction to Physical Exam” course. Our previous research has found that students feel more confident and report a higher level of perceived transferability to live patients when learning the pelvic exam on soft-embalmed donors in comparison to low-fidelity mannequins. Our goal in this project was to incorporate soft-embalmed donors into the curriculum of first year medical students, making this teaching method available to all students, and objectively assess their skills as well as their retention. During the “Introduction to Physical Exam” course, high fidelity soft embalmed donors were available for students to practice the female pelvic exam with instruction from attending physicians. After learning exam techniques, all 67 students were given a survey to assess their confidence, perceived transferability, and preference for either soft embalmed donors or mannequins. They were also invited back the following week to assess their short term retention and ability to accurately perform the pelvic exam, with the option of using communication skills learned elsewhere in the ETSU curriculum. Thirteen students returned for this follow-up session and completed surveys to reassess their experience. We plan to follow this cohort of students throughout their medical school career to assess long term retention. All return participants felt they retained the pelvic exam knowledge learned the week prior, with 61.54% agreeing, and 38.46% strongly agreeing. Most felt prepared to now do a pelvic exam on a live patient (53.85% agreed, 38.46% strongly agreed). Students also reported that feedback on their communication and procedural skills was beneficial to the learning process. The use of high fidelity soft embalmed donors in medical education provides students with a realistic model to learn and become confident in performing pelvic exams. We have seen that this education model helps them retain their knowledge on pelvic exam technique. We look forward to following this cohort of students to see if this retention of knowledge persists into their third year of medical school

    Feature selection through validation and un-censoring of endovascular repair survival data for predicting the risk of re-intervention

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    Background: Feature selection (FS) process is essential in the medical area as it reduces the effort and time needed for physicians to measure unnecessary features. Choosing useful variables is a difficult task with the presence of censoring which is the unique characteristic in survival analysis. Most survival FS methods depend on Cox's proportional hazard model; however, machine learning techniques (MLT) are preferred but not commonly used due to censoring. Techniques that have been proposed to adopt MLT to perform FS with survival data cannot be used with the high level of censoring. The researcher's previous publications proposed a technique to deal with the high level of censoring. It also used existing FS techniques to reduce dataset dimension. However, in this paper a new FS technique was proposed and combined with feature transformation and the proposed uncensoring approaches to select a reduced set of features and produce a stable predictive model. Methods: In this paper, a FS technique based on artificial neural network (ANN) MLT is proposed to deal with highly censored Endovascular Aortic Repair (EVAR). Survival data EVAR datasets were collected during 2004 to 2010 from two vascular centers in order to produce a final stable model. They contain almost 91% of censored patients. The proposed approach used a wrapper FS method with ANN to select a reduced subset of features that predict the risk of EVAR re-intervention after 5 years to patients from two different centers located in the United Kingdom, to allow it to be potentially applied to cross-centers predictions. The proposed model is compared with the two popular FS techniques; Akaike and Bayesian information criteria (AIC, BIC) that are used with Cox's model. Results: The final model outperforms other methods in distinguishing the high and low risk groups; as they both have concordance index and estimated AUC better than the Cox's model based on AIC, BIC, Lasso, and SCAD approaches. These models have p-values lower than 0.05, meaning that patients with different risk groups can be separated significantly and those who would need re-intervention can be correctly predicted. Conclusion: The proposed approach will save time and effort made by physicians to collect unnecessary variables. The final reduced model was able to predict the long-term risk of aortic complications after EVAR. This predictive model can help clinicians decide patients' future observation plan

    Acetabular Component Deformation under Rim Loading Using Digital Image Correlation and Finite Element Methods

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    Total hip replacement is a highly successful operation; restoring function and reducing pain in arthritis patients. In recent years, thinner resurfacing acetabular cups have been introduced in order to preserve bone stock and reduce the risk of dislocation. However concerns have been raised that deformation of these cups could adversely affect the lubrication regime of the bearing; leading to equatorial and edge contact, possibly causing the implants to jam. This study aims to assess the amount of deformation which occurs due to the tight peripheral fit experienced during press-fit by applying rim loading to three different designs of acetabular cup: a clinically successful cobalt chrome resurfacing cup, a prototype composite resurfacing cup and a clinically successful polyethylene monobloc cup. Digital Image Correlation (DIC) was used to measure the deformation and to validate Finite Element (FE) models. DIC provided a non-contacting method to measure displacement; meaning the load could be increased continuously rather than in steps as in previous studies. The physical testing showed that the cobalt chrome cups were significantly stiffer than the composite prototype and polyethylene cups. The FE models were in good agreement with the experimental results for all three cups and were able to predict the deformation to within 10%. FE models were also created to investigate the effect of cup outside diameter and wall thickness on stiffness under rim loading. Increasing outside diameter resulted in a linear reduction in stiffness for all three materials. Increasing the wall thickness resulted in an exponential increase in cup stiffness. Rim loading an acetabular shell does not accurately simulate the in vivo conditions; however it does provide a simple method for comparing cups made of different materials

    The temperate Burkholderia phage AP3 of the Peduovirinae shows efficient antimicrobial activity against B. cenocepacia of the IIIA lineage

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    Burkholderia phage AP3 (vB_BceM_AP3) is a temperate virus of the Myoviridae and the Peduovirinae subfamily (P2likevirus genus). This phage specifically infects multidrug-resistant clinical Burkholderia cenocepacia lineage IIIA strains commonly isolated from cystic fibrosis patients. AP3 exhibits high pairwise nucleotide identity (61.7 %) to Burkholderia phage KS5, specific to the same B. cenocepacia host, and has 46.7–49.5 % identity to phages infecting other species of Burkholderia. The lysis cassette of these related phages has a similar organization (putative antiholin, putative holin, endolysin, and spanins) and shows 29–98 % homology between specific lysis genes, in contrast to Enterobacteria phage P2, the hallmark phage of this genus. The AP3 and KS5 lysis genes have conserved locations and high amino acid sequence similarity. The AP3 bacteriophage particles remain infective up to 5 h at pH 4–10 and are stable at 60 °C for 30 min, but are sensitive to chloroform, with no remaining infective particles after 24 h of treatment. AP3 lysogeny can occur by stable genomic integration and by pseudo-lysogeny. The lysogenic bacterial mutants did not exhibit any significant changes in virulence compared to wild-type host strain when tested in the Galleria mellonella moth wax model. Moreover, AP3 treatment of larvae infected with B. cenocepacia revealed a significant increase (P < 0.0001) in larvae survival in comparison to AP3-untreated infected larvae. AP3 showed robust lytic activity, as evidenced by its broad host range, the absence of increased virulence in lysogenic isolates, the lack of bacterial gene disruption conditioned by bacterial tRNA downstream integration site, and the absence of detected toxin sequences. These data suggest that the AP3 phage is a promising potent agent against bacteria belonging to the most common B. cenocepacia IIIA lineage strains

    MDR1 gene-related clonal selection and P-glycoprotein function and expression in relapsed or refractory acute myeloid leukemia

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    The expression of P-glycoprotein (P-gp), encoded by the MDR1 gene, is an independent adverse prognostic factor for response and survival in de novo acute myeloid leukemia (AML). Little is known about MDR1 expression during the development of disease. The present study investigated whether MDR1 gene- related clonal selection occurs in the development from diagnosis to relapsed AML, using a genetic polymorphism of the MDR1 gene at position 2677. Expression and function of P-gp were studied using monoclonal antibodies MRK16 and UIC2 and the Rhodamine 123 retention assay with or without PSC 833. No difference was found in the levels of P-gp function and expression between diagnosis and relapse in purified paired blast samples from 30 patients with AML. Thirteen patients were homozygous for the genetic polymorphism of MDR1 (n = 7 for guanine, n = 6 for thymidine), whereas 17 patients were heterozygous (GT). In the heterozygous patients, no selective loss of one allele was observed at relapse. Homozygosity for the MDR1 gene (GG or TT) was associated with shorter relapse-free intervals (P =.002) and poor survival rates (P =.02), compared with heterozygous patients. No difference was found in P-gp expression or function in patients with AML with either of the allelic variants of the MDR1 gene. It was concluded that P-gp function or expression is not upregulated at relapse/refractory disease and expression of one of the allelic variants is not associated with altered P-gp expression or function in AML, consistent with the fact that MDR1 gene-related clonal selection does not occur when AML evolves to recurrent disease. (Blood. 2001;97:3605-3611

    Energy spread of ultracold electron bunches extracted from a laser cooled gas

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    Ultrashort and ultracold electron bunches created by near-threshold femtosecond photoionization of a laser-cooled gas hold great promise for single-shot ultrafast diffraction experiments. In previous publications the transverse beam quality and the bunch length have been determined. Here the longitudinal energy spread of the generated bunches is measured for the first time, using a specially developed Wien filter. The Wien filter has been calibrated by determining the average deflection of the electron bunch as a function of magnetic field. The measured relative energy spread σUU=0.64±0.09%\frac{\sigma_{U}}{U} = 0.64 \pm 0.09\% agrees well with the theoretical model which states that it is governed by the width of the ionization laser and the acceleration length
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