1,111 research outputs found
Lorraine Noye, Emily and Jenkens, C. Dorsey, Mr. and Mrs. Pearce Richburg, Barbara Warner to James Meredith (30 September 1962)
Signed by Lorraine Noye, Emily and Jenkens, C. Dorsey, Mr. and Mrs. Pearce Richburg, Barbara Warnerhttps://egrove.olemiss.edu/mercorr_pro/1853/thumbnail.jp
Next-generation seismic experiments – II: wide-angle, multi-azimuth, 3-D, full-waveform inversion of sparse field data
3-D full-waveform inversion (FWI) is an advanced seismic imaging technique that has been widely adopted by the oil and gas industry to obtain high-fidelity models of P-wave velocity that lead to improvements in migrated images of the reservoir. Most industrial applications of 3-D FWI model the acoustic wavefield, often account for the kinematic effect of anisotropy, and focus on matching the low-frequency component of the early arriving refractions that are most sensitive to P-wave velocity structure. Here, we have adopted the same approach in an application of 3-D acoustic, anisotropic FWI to an ocean-bottom-seismometer (OBS) field data set acquired across the Endeavour oceanic spreading centre in the northeastern Pacific. Starting models for P-wave velocity and anisotropy were obtained from traveltime tomography; during FWI, velocity is updated whereas anisotropy is kept fixed. We demonstrate that, for the Endeavour field data set, 3-D FWI is able to recover fine-scale velocity structure with a resolution that is 2–4 times better than conventional traveltime tomography. Quality assurance procedures have been employed to monitor each step of the workflow; these are time consuming but critical to the development of a successful inversion strategy. Finally, a suite of checkerboard tests has been performed which shows that the full potential resolution of FWI can be obtained if we acquire a 3-D survey with a slightly denser shot and receiver spacing than is usual for an academic experiment. We anticipate that this exciting development will encourage future seismic investigations of earth science targets that would benefit from the superior resolution offered by 3-D FWI
A Comparison of Women’s Travel to Mammography Services and Average Week Day Trip Length
Long travel distances/times to a mammography service may act as a barrier that hinders women from seeking screening mammography on a recommended schedule. Average weekday trip length data from the New South Wales Travel Survey was compared with the average distance women travelled to a mammography service, the difference was tested using the Wilcoxon Signed Rank Test. The distance travelled to mammography services was statistically greater than the average week day trip length from the New South Wales Travel Survey (4.3 km, 95% CI 3.3 to 5.9 kms, p,0.001). This study has identified that within New South Wales there is a significant difference between average week day trip length travel and client travel to mammography services. Therefore, highlighting that women are undertaking a greater than normal travel burden to access mammography services. The comparison of normal weekday travel and travel to mammography services has enabled the burden of travel to mammography services to be identified. Reducing the burden of travel to mammography services is pivotal to increasing the utilization of mammography services and reducing the inequalities in health comes
Tamoxifen resistance in early breast cancer: statistical modelling of tissue markers to improve risk prediction
BACKGROUND: For over two decades, the Nottingham Prognostic Index (NPI) has been used in the United Kingdom to calculate risk
scores and inform management about breast cancer patients. It is derived using just three clinical variables – nodal involvement,
tumour size and grade. New scientific methods now make cost-effective measurement of many biological characteristics of tumour
tissue from breast cancer biopsy samples possible. However, the number of potential explanatory variables to be considered presents
a statistical challenge. The aim of this study was to investigate whether in ERþ tamoxifen-treated breast cancer patients, biological
variables can add value to NPI predictors, to provide improved prognostic stratification in terms of overall recurrence-free survival
(RFS) and also in terms of remaining recurrence free while on tamoxifen treatment (RFoT). A particular goal was to enable the
discrimination of patients with a very low risk of recurrence.
METHODS: Tissue samples of 401 cases were analysed by microarray technology, providing biomarker data for 72 variables in total,
from AKT, BAD, HER, MTOR, PgR, MAPK and RAS families. Only biomarkers screened as potentially informative (i.e., exhibiting
univariate association with recurrence) were offered to the multivariate model. The multiple imputation method was used to deal
with missing values, and bootstrap sampling was used to assess internal validity and refine the model.
RESULTS: Neither the RFS nor RFoT models derived included Grade, but both had better predictive and discrimination ability than NPI.
A slight difference was observed between models in terms of biomarkers included, and, in particular, the RFoT model alone included
HER2. The estimated 7-year RFS rates in the lowest-risk groups by RFS and RFoT models were 95 and 97%, respectively, whereas
the corresponding rate for the lowest-risk group of NPI was 89%.
CONCLUSION: The findings demonstrate considerable potential for improved prognostic modelling by incorporation of biological
variables into risk prediction. In particular, the ability to identify a low-risk group with minimal risk of recurrence is likely to have clinical
appeal. With larger data sets and longer follow-up, this modelling approach has the potential to enhance an understanding of the
interplay of biological characteristics, treatment and cancer recurrence.
British Journal of Cancer (2010) 102
Manifestly Supersymmetric RG Flows
Renormalisation group (RG) equations in two-dimensional N=1 supersymmetric
field theories with boundary are studied. It is explained how a manifestly N=1
supersymmetric scheme can be chosen, and within this scheme the RG equations
are determined to next-to-leading order. We also use these results to revisit
the question of how brane obstructions and lines of marginal stability appear
from a world-sheet perspective.Comment: 22 pages; references added, minor change
Seismic imaging of Santorini: subsurface constraints on caldera collapse and present-day magma recharge
Volcanic calderas are surface depressions formed by roof collapse following evacuation of magma from an underlying reservoir. The mechanisms of caldera formation are debated and predict differences in the evolution of the caldera floor and distinct styles of magma recharge. Here we use a dense, active source, seismic tomography study to reveal the sub-surface physical properties of the Santorini caldera in order to understand caldera formation. We find a ∼3-km-wide, cylindrical low-velocity anomaly in the upper 3 km beneath the north-central portion of the caldera, that lies directly above the pressure source of the 2011-2012 inflation. We interpret this anomaly as a low-density volume caused by excess porosities of between 4% and 28%, with pore spaces filled with hot seawater. Vents that were formed during the first three phases of the 3.6 ka Late Bronze Age (LBA) eruption are located close to the edge of the imaged structure. The correlation between older volcanic vents and the low-velocity anomaly suggests that this feature may be long-lived. We infer that collapse of a limited area of the caldera floor resulted in a high-porosity, low-density cylindrical volume, which formed by either chaotic collapse along reverse faults, wholesale subsidence and infilling with tuffs and ignimbrites, phreatomagmatic fracturing, or a combination of these processes. Phase 4 eruptive vents are located along the margins of the topographic caldera and the velocity structure indicates that coherent down-drop of the wider topographic caldera followed the more limited collapse in the northern caldera. This progressive collapse sequence is consistent with models for multi-stage formation of nested calderas along conjugate reverse and normal faults. The upper crustal density differences inferred from the seismic velocity model predict differences in subsurface gravitational loading that correlate with the location of 2011-2012 edifice inflation. This result supports the hypothesis that sub-surface density anomalies may influence present-day magma recharge events. We postulate that past collapses and the resulting topographical and density variations at Santorini influence magma focusing between eruptive cycles, a feedback process that may be important in other volcanoes
Vertical zonation of testate amoebae in the Elatia Mires, northern Greece : palaeoecological evidence for a wetland response to recent climate change or autogenic processes?
The Elatia Mires of northern Greece are unique ecosystems of high conservation value. The mires are climatically marginal and may be sensitive to changing hydroclimate, while northern Greece has experienced a significant increase in aridity since the late twentieth century. To investigate the impact of recent climatic change on the hydrology of the mires, the palaeoecological record was investigated from three near-surface monoliths extracted from two sites. Testate amoebae were analysed as sensitive indicators of hydrology. Results were interpreted using transfer function models to provide quantitative reconstructions of changing water table depth and pH. AMS radiocarbon dates and 210Pb suggest the peats were deposited within the last c. 50 years, but do not allow a secure chronology to be established. Results from all three profiles show a distinct shift towards a more xerophilic community particularly noted by increases in Euglypha species. Transfer function results infer a distinct lowering of water tables in this period. A hydrological response to recent climate change is a tenable hypothesis to explain this change; however other possible explanations include selective test decay, vertical zonation of living amoebae, ombrotrophication and local hydrological change. It is suggested that a peatland response to climatic change is the most probable hypothesis, showing the sensitivity of marginal peatlands to recent climatic change
Social disorganization and history of child sexual abuse against girls in sub-Saharan Africa : a multilevel analysis
Background:
Child sexual abuse (CSA) is a considerable public health problem. Less focus has been paid to the role of community level factors associated with CSA. The aim of this study was to examine the association between neighbourhood-level measures of social disorganization and CSA.
Methods:
We applied multiple multilevel logistic regression analysis on Demographic and Health Survey data for 6,351 adolescents from six countries in sub-Saharan Africa between 2006 and 2008.
Results:
The percentage of adolescents that had experienced CSA ranged from 1.04% to 5.84%. There was a significant variation in the odds of reporting CSA across the communities, suggesting 18% of the variation in CSA could be attributed to community level factors. Respondents currently employed were more likely to have reported CSA than those who were unemployed (odds ratio [OR] = 2.05, 95% confidence interval [CI] 1.48 to 2.83). Respondents from communities with a high family disruption rate were 57% more likely to have reported CSA (OR=1.57, 95% CI 1.14 to 2.16).
Conclusion:
We found that exposure to CSA was associated with high community level of family disruption, thus suggesting that neighbourhoods may indeed have significant important effects on exposure to CSA. Further studies are needed to explore pathways that connect the individual and neighbourhood levels, that is, means through which deleterious neighbourhood effects are transmitted to individuals
Acromial stress fracture in a young wheelchair user with Charcot-Marie-Tooth disease: a case report
Acromial stress fractures are rare and have not been highlighted as a potential complication of wheelchair use. We report the case of a 22-year old female wheelchair bound patient with Charcot-Marie-Tooth disease who presented with a four-year history of shoulder pain which impaired mobility and quality of life. Plain radiographs showed a cortical irregularity of the acromion but no double-density sign. After CT scans a non-united acromial stress fracture was diagnosed. She had no other shoulder pathology. The new technique of using a superiorly closing wedge osteotomy with cancellous lag screw fixation was successful in correcting the mobile non-united acromial fragment and resolving her pain
The Business Case for Preconception Care: Methods and Issues
Only a limited number of economic evaluations have addressed the costs and benefits of preconception care. In order to persuade health care providers, payers, or purchasers to become actively involved in promoting preconception care, it is important to demonstrate the value of doing so through development of a “business case”. Perceived benefits in terms of organizational reputation and market share can be influential in forming a business case. In addition, it is standard to include an economic analysis of financial costs and benefits from the perspective of the provider practice, payer, or purchaser in a business case. The methods, data needs, and other issues involved with preparing an economic analysis of the likely financial return on investment in preconception care are presented here. This is accompanied by a review or case study of economic evaluations of preconception care for women with recognized diabetes. Although the data are not sufficient to draw firm conclusions, there are indications that such care may yield positive financial benefits to health care organizations through reduction in maternal and infant hospitalizations. More work is needed to establish how costs and economic benefits are distributed among different types of organizations. Also, the optimum methods of delivering preconception care for women with diabetes need to be evaluated. Similar assessments should also be conducted for other forms of preconception care, including comprehensive care
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