Characterizing flow pathways in a sandstone aquifer: Tectonic vs sedimentary heterogeneities

Sandstone aquifers are commonly assumed to represent porous media characterized by a permeable matrix. However, such aquifers may be heavy fractured when rock properties and timing of deformation favour brittle failure and crack opening. In many aquifer types, fractures associated with faults, bedding planes and stratabound joints represent preferential pathways for fluids and contaminants. In this paper, well test and outcrop-scale studies reveal how strongly lithified siliciclastic rocks may be entirely dominated by fracture flow at shallow depths (≤ 180 m), similar to limestone and crystalline aquifers. However, sedimentary heterogeneities can primarily control fluid flow where fracture apertures are reduced by overburden pressures or mineral infills at greater depths. The Triassic St Bees Sandstone Formation (UK) of the East Irish Sea Basin represents an optimum example for study of the influence of both sedimentary and tectonic aquifer heterogeneities in a strongly lithified sandstone aquifer-type. This fluvial sedimentary succession accumulated in rapidly subsiding basins, which typically favours preservation of complete depositional cycles including fine grained layers (mudstone and silty sandstone) interbedded in sandstone fluvial channels. Additionally, vertical joints in the St Bees Sandstone Formation form a pervasive stratabound system whereby joints terminate at bedding discontinuities. Additionally, normal faults are present through the succession showing particular development of open-fractures. Here, the shallow aquifer (depth ≤ 180 m) was characterized using hydro-geophysics. Fluid temperature, conductivity and flow-velocity logs record inflows and outflows from normal faults, as well as from pervasive bed-parallel fractures. Quantitative flow logging analyses in boreholes that cut fault planes indicates that zones of fault-related open fractures characterize ~ 50% of water flow. The remaining flow component is dominated by bed-parallel fractures. However, such sub-horizontal fissures become the principal flow conduits in wells that penetrate the exterior parts of fault damage zones, as well as in non-faulted areas. The findings of this study have been compared with those of an earlier investigation of the deeper St Bees Sandstone aquifer (180 to 400 m subsurface depth) undertaken as part of an investigation for a proposed nuclear waste repository. The deeper aquifer is characterized by significantly lower transmissivities. High overburden pressure and the presence of mineral infillings, have reduced the relative impact of tectonic heterogeneities on transmissivity here, thereby allowing matrix flow in the deeper part of the aquifer. The St Bees Sandstone aquifer contrasts the hydraulic behaviour of low-mechanically resistant sandstone rock-types. In fact, the UK Triassic Sandstone of the Cheshire Basin is low-mechanically resistant and flow is supported both by matrix and fracture. Additionally, faults in such weak-rocks are dominated by granulation seams representing flow-barriers which strongly compartmentalize the UK Triassic Sandstone in the Cheshire Basin

The geometry of fluvial channel bodies: Empirical characterization and implications for object-based models of the subsurface

The distribution of channel deposits in fluvial reservoirs is commonly modeled with object-based techniques, constrained on quantities describing the geometries of channel bodies. To ensure plausible simulations, it is common to define inputs to these models by referring to geologic analogs. Given their ability to reproduce complex geometries and to draw upon the analog experience, object-based models are considered inherently realistic. Yet this perceived realism has not hitherto been tested by assessing the outputs of these techniques against sedimentary architectures in the stratigraphic record. This work presents a synthesis of data on the geometry of channel bodies, derived from a sedimentologic database, with the following aims: (1) to provide tools for constraining stochastic models of fluvial reservoirs in data-poor situations, and (2) to test the intrinsic realism of object-based modeling algorithms by comparing characteristics of the modeled architectures against analogs. An empirical characterization of the geometry of fluvial channel bodies is undertaken that describes distributions in (and relationships among) channel-body thickness, cross-stream width, and planform wavelength and amplitude. Object-based models are then built running simulations conditioned on six alternative, analog-informed parameter sets, using four algorithms according to nine different approaches. Closeness of match between analogs and models is then determined on a statistical basis. Results indicate which modeling approaches return architectures that more closely resemble the organization of fluvial depositional systems known from nature and in what respect. None of the tested algorithms fully reproduce characteristics seen in natural systems, demonstrating the need for subsurface modeling methods to better incorporate geologic knowledge

Predicting systemic spread in early colorectal cancer: Can we do better?

Through the implementation of national bowel cancer screening programmes we have seen a three-fold increase in early pT1 colorectal cancers, but how these lesions should be managed is currently unclear. Local excision can be an attractive option, especially for fragile patients with multiple comorbidities, but it is only safe from an oncological point of view in the absence of lymph node metastasis. Patient risk stratification through careful analysis of histopathological features in local excision or polypectomy specimens should be performed according to national guidelines to avoid under- or over-treatment. Currently national guidelines vary in their recommendations as to which factors should be routinely reported and there is no established multivariate risk stratification model to determine which patients should be offered major resectional surgery. Conventional histopathological parameters such as tumour grading or lymphovascular invasion have been shown to be predictive of lymph node metastasis in a number of studies but the inter- and intra-observer variation in reporting is high. Newer parameters including tumour budding and poorly differentiated clusters have been shown to have great potential, but again some improvement in the inter-observer variation is required. With the implementation of digital pathology into clinical practice, quantitative parameters like depth/area of submucosal invasion and proportion of stroma can be routinely assessed. In this review we present the various histopathological risk factors for predicting systemic spread in pT1 colorectal cancer and introduce potential novel quantitative variables and multivariable risk models that could be used to better define the optimal treatment of this increasingly common disease

The importance of pathological quality control for rectal surgery

Pathologists are an integral member of the colorectal multidisciplinary team and are able to closely interact with surgeons, radiologists and oncologists to facilitate improvements in surgical quality and patient outcomes. Accurate, high quality pathology reports containing all vital prognostic information are essential to ensure the patient receives optimal treatment. These reports should also integrate feedback to all members of the multidisciplinary team on the accuracy of preoperative staging, response to preoperative treatment, and the quality of surgery. Pathologists have played a key role in improving outcomes in patients with rectal cancer by recognising the prognostic importance of an involved circumferential resection margin. In addition, pathologists have described an assessment of the surgical planes of dissection as a marker of surgical quality and thereby a means of quality control. This article will review the current best practice for the pathological assessment of anterior resections and abdominoperineal excisions for rectal cancer and ultimately look at how pathologists can influence quality control in rectal cancer surgery

An assessment of job satisfaction among primary health care workers in Rivers state, Nigeria

Background: Primary Health Care (PHC) is considered to be a more appropriate approach to health, and the health system, improving access to health services, as well as disease prevention. The availability and efficiency of PHC is a key determinant of the overall health and wellbeing of a people, and a useful yardstick for assessment of a nation's health system. Hence, PHC workforce are at the vanguard of essential health service delivery through direct contact with grassroots community members, within and without the health facilities, for provision of preventive, treatment, referral and follow-up health services. Poor motivation and non-retention of PHC workers weakens the health systems' ability to meet the above goals.Aim: To assessed the job satisfaction of primary health care workers in Rivers State, Nigeria.Methodology: The study utilized the descriptive cross-sectional design and the mixed methods of data collection. The quantitative method used semi-structured, pretested, self- administered questionnaires to obtain information on socio-demographic and occupational characteristics, job satisfaction, motivation, frustration, retention potentials and awareness of existing policies and incentives of respondents. The respondents which included Community Health Extension Workers (CHEW), Community Health Officers (CHO), nurses and doctors in Primary health facilities in the State, were selected using the multistage sampling method. Quantitative data was analyzed using SPSS version 20.0 software and results presented using tables and charts.Results: A total of 378 respondents participated in the study. Nurses constituted 47.6% of the respondents, with equal proportions of CHEWs and CHOs [23.8% and 23.8% respectively] and 4.8% were doctors. The mean age of the respondents was39.8±8.1 years; with 89.7% females and 10.3% males. Of all the respondents, 79.6% were married,82% were senior cadre staff and 78.8% were Pentecostal Christians. Ikwerre, Ogoni and Kalabari had the highest distribution in ethnicity (19.3%, 14.8% and14.0% respectively). Among the respondents, 75.7% had worked for less than 7 years in their current facility while 82.9% had worked for same duration in their previous facility. Almost two third 240 (63.5%) reported that their workplace was far from their residence while 12 (3.2%) stated that it was very close. A high proportion of the respondents (78.3%) were satisfied with the general working condition in their Primary Health Care facility while 21.7% of the respondents were satisfied with the pay and promotion potentials of their work place. Notably, while 97.9% of the respondents were satisfied with their work relationships, 57.7% were satisfied with the use of their skills and abilities at their workplace and 88.1% of the respondents were satisfied with their work activities. These gave a good job satisfaction score for 88.9% of the respondents. Profession, community, distance from work and duration of work were significant factors (p < 0.05).Conclusion: This study concluded that age, marital status, profession, and location of health facility, duration of work played vital roles in level of satisfaction of PHC workers. Hence, offering opportunities for professional advancement through training of the healthcare workers though already included in the Nigerian National Healthcare policy, should be efficiently implemented and monitored by the government and other relevant stakeholders to improve job satisfaction and in turn quality health service delivery.Keywords: Job Satisfaction, Healthcare Worker

The Development and Validation of a new Multidimensional Test Anxiety Scale (MTAS)

Although test anxiety has a long history in the educational and psychological literature there is a lack of census over its dimensionality. The aim of the present study was to clarify the dimensionality of test anxiety and develop a new instrument to reflect this dimensionality. Across two empirical studies we tested and refined a new multidimensional instrument comprising of two cognitive dimensions (Worry and Cognitive Interference) and two affective-physiological dimensions (Tension and Physiological Indicators). In both studies four-correlated-factors and higher-order models showed a good fit to the data. Test anxiety was positively related to an existing test anxiety measure (the Test Anxiety Inventory) and an elevated risk of mental health problems, and negatively related to school wellbeing and examination performance. This new instrument will prove a welcome addition for practitioners, to assist in the identification of highly test anxious students who may require support or intervention, and test anxiety researchers

Significant individual variation between pathologists in the evaluation of colon cancer specimens after complete mesocolic excision

Background: After the introduction of complete mesocolic excision, a new pathological evaluation of the resected colon cancer specimen was introduced. This concept has quickly gained acceptance and is often used to compare surgical quality. The grading of colon cancer specimens is likely to depend on both surgical quality and the training of the pathologist. Objective: The purpose of this study was to validate the principles of the pathological evaluation of colon cancer specimens. Design: This was an exploratory study. Settings: The study was conducted in Aarhus, Denmark, and Leeds, United Kingdom. Patients: Colon cancers specimens were used. Main outcome measures: The agreement of gradings between participants was of interest. Four specialist GI pathologists and 2 abdominal surgeons evaluated 2 rounds of colon cancer specimens, each at 2 separate time points. Each round contained 50 specimens. After the first round, a protocol of detailed principles for the grading procedure was agreed on. Results from an experienced pathologist were considered as the reference results. Results: In the first round, the distribution of gradings between participants showed substantial variation. In the second round, the variation was reduced. Intraobserver agreement was mostly fair to good, whereas interobserver agreement was frequently poor. This did not significantly change from round 1 to round 2. Limitations: The small sample size of 100 specimens provided a very small number of specimens resected in the muscularis propria plane, which renders the evaluation of this group potentially unreliable. The evaluations were made on photos and not on fresh specimens. Conclusions: This study demonstrates significant variation in the pathological evaluation of colon cancer specimens. It demonstrates that it cannot be used in clinical studies, and care should be taken when comparing results between different hospitals

Developing a Raman spectroscopy-based tool to stratify patient response to pre-operative radiotherapy in rectal cancer

Rectal cancer patients frequently receive pre-operative radiotherapy (RT), prior to surgical resection. However, colorectal cancer is heterogeneous and the degree of tumour response to pre-operative RT is highly variable. There are currently no clinically approved methods of predicting response to RT, and a significant proportion of patients will show no clinical benefit, despite enduring the side-effects. We evaluated the use of Raman spectroscopy (RS), a non-destructive technique able to provide the unique chemical fingerprint of tissues, as a potential tool to stratify patient response to pre-operative RT. Raman measurements were obtained from the formalin-fixed, paraffin-embedded (FFPE) pre-treatment biopsy specimens of 20 rectal cancer patients who received pre-operative RT. A principal component analysis and linear discriminant analysis algorithm was able to classify patient response to pre-operative RT as good or poor, with an accuracy of 86.04 ± 0.14% (standard error). Patients with a good response to RT showed greater contributions from protein-associated peaks, whereas patients who responded poorly showed greater lipid contributions. These results demonstrate that RS is able to reliably classify tumour response to pre-operative RT from FFPE biopsies and highlights its potential to guide personalised cancer patient treatment

Defining response to radiotherapy in rectal cancer using magnetic resonance imaging and histopathological scales

Aim: To define good and poor regression using pathology and MRI regression scales after neo-adjuvant chemotherapy for rectal cancer. Methods: A systematic review of all studies up to December 2015, without language restriction that were identified from MEDLINE, Cochrane Controlled Trials Register (1960–2015), and EMBASE (1991–2015). Searches were performed of article bibliographies and conference abstracts. MeSH and text words, included “tumour regression”, “mrTRG”, “poor response” and “colorectal cancers”. Clinical studies using either MRI or histopathological TRG scales to define good and poor responders were included in relation to outcomes (local (LR), distant recurrence (DR), disease free (DFS), overall survival (OS)). There was no age restriction to included patients nor stage of cancer.Data was extracted by two authors independently using pre-defined outcome measures. Results: Quantitative data (prevalence) were extracted and analysed according to meta-analytical techniques using comprehensive meta-analysis. Qualitative data (LR, DR, DFS &OS) were presented as ranges. The overall proportion of poor responders after neo-adjuvant CRT was 37.7% (CI: 30.1 to 45.8). There were 19 different reported histopathological scales and one MRI regression scale (mrTRG). Clinical studies used nine and six histopathological scales for poor and good responders respectively. All studies using MRI to define good and poor response used one scale. The most common histopathological definition for good response was the Mandard grades 1&2 or Dworak grades 3&4; Mandard 3,4&5 and Dworak 0,1&2 were used for poor response. For histopathological grades, the 5-year outcomes for poor responders were LR 3.4-4.3%, DR 14.3-20.3%, DFS 61.7-68.1% and OS 60.7-69.1. Good pathological response 5-year outcomes were LR, 0-1.8%; DR, 0-11.6%; DFS, 78.4-86.7%; and, OS, 77.4-88.2%. A poor response on MRI (mrTRG 4,5) resulted in 5-year LR 4-29%, DR 9%, DFS 31-59% and OS 27-68%. The 5-year outcomes with a good response on MRI (mrTRG 1,2 & 3) was LR 1-14%, DR 3%, DFS 64-83% and OS 72-90%. Conclusions: For histopathology regression assessment Mandard1,2/Dworak3,4 should be used for good and Mandard3,4,5/Dworak0,1,2 for poor response. MRI indicates good and poor response by mrTRG1-3 and mrTRG4-5 respectively