The behavior of drilled shaft retaining walls in expansive clay soils

textDrilled shaft retaining walls are common earth retaining structures, well suited to urban environments where noise, space, and damage to adjacent structures are major considerations. The design of drilled shaft retaining walls in non-expansive soils is well established. In expansive soils, however, there is no consensus on the correct way to account for the influence of soil expansion on wall behavior. Based on the range of design assumptions currently in practice, existing walls could be substantially over- or under-designed. The goal of this research is to advance the understanding of the effects of expansive clay on drilled shaft retaining walls. The main objectives of this study are to identify the processes responsible for wall loading and deformation in expansive clay, to evaluate how these processes change with time, and to provide guidance for design practice to account for these processes and ensure adequate wall performance. The primary source of information for this research is performance data from a four-year monitoring program at the Lymon C. Reese research wall, a full-scale instrumented drilled shaft retaining wall constructed through expansive clay in Manor, Texas. The test wall was instrumented with inclinometers and fiber optic strain gauges, and performance data was recorded during construction, excavation, during natural moisture fluctuations, and during controlled inundation tests that provided the retained soil with unlimited access to water. In addition to the test wall study, a field assessment of existing TxDOT drilled shaft retaining walls was conducted. The main process influencing short-term wall deformation was found to be global response to stress relief during excavation, which causes the wall and soil to move together without the development of large earth pressures or bending stresses. Long-term wall deformations were governed by the development of drained conditions in both the retained soil and the foundation soil after approximately eight months of controlled inundation testing. To ensure adequate wall performance, the deformations and structural loads associated with short- and long-term conditions should be combined and checked against allowable values.Civil, Architectural, and Environmental Engineerin

A Study of the Critical Uncertainty Contributions in the Analysis of PCBs in Ambient Air

The measurement of polychlorinated biphenyls (PCBs) in ambient air requires a complex, multistep sample preparation procedure prior to analysis by gas chromatography—mass spectrometry (GC-MS). Although routine analytical laboratories regularly carry out these measurements, they are often undertaken with little regard to the accurate calculation of measurement uncertainty, or appreciation of the sensitivity of the accuracy of the measurement to each step of the analysis. A measurement equation is developed for this analysis, and the contributory sources to the overall uncertainty when preparing calibration standards and other solutions by gravimetric and volumetric approaches are discussed and compared. For the example analysis presented, it is found that the uncertainty of the measurement is dominated by the repeatability of the GC-MS analysis and suggested that volumetric (as opposed to gravimetric) preparation of solutions does not adversely affect the overall uncertainty. The methodology presented in this work can also be applied to analogous methods for similar analytes, for example, those used to measure polycyclic aromatic hydrocarbons (PAHs), pesticides, dioxins, or furans in ambient air

Surgical approaches to adenocarcinoma of the gastroesophageal junction: the Siewert II conundrum.

BACKGROUND: The Siewert classification system for gastroesophageal junction adenocarcinoma has provided morphological and topographical information to help guide surgical decision-making. Evidence has shown that Siewert I and III tumors are distinct entities with differing epidemiologic and histologic characteristics and distinct patterns of disease progression, requiring different treatment. Siewert II tumors share some of the characteristics of type I and III lesions, and the surgical approach is not universally agreed upon. Appropriate surgical options include transthoracic esophagogastrectomy, transhiatal esophagectomy, and transabdominal extended total gastrectomy. PURPOSE: A review of the available evidence of the surgical management of Siewert II tumors is presented. CONCLUSIONS: Careful review of the data appear to support the fact that a satisfactory oncologic resection can be achieved via a transabdominal extended total gastrectomy with a slight advantage in terms of perioperative complications, and overall postoperative quality of life. Overall and disease-free survival compares favorably to the transthoracic approach. These results can be achieved with careful selection of patients balancing more than just the Siewert type in the decision-making but considering also preoperative T and N stages, histological type (diffuse type requiring longer margins that are not always achievable via gastrectomy), and the presence of Barrett\u27s esophagus

On the Optimum Sampling Time for the Measurement of Pollutants in Ambient Air

No measurement result of any kind is complete without an associated statement of uncertainty. In general, the aim is to minimise this measurement uncertainty to the extent that the measurement made is fit for purpose, or the uncertainty meets an acceptable level such as a “data quality objective”. This paper demonstrates how the sampling time used to measure a pollutant in ambient air over a given time period, particularly with automatic instruments, can affect the uncertainty of the measurement result. It is shown that the uncertainty of the overall result depends critically on how the precision characteristics of the measuring instrumentation vary with analyte abundance. An example of the determination of these characteristics for mercury vapour measurement and the conclusions that may be drawn about optimum sampling times to minimise uncertainty are presented. For situations where uncertainty is minimised by the use of long sampling periods, the implications of this strategy on the “information richness” of the data and on the detection of short-term episodes, as well as peak concentrations, are discussed

Production of a Novel Copper-Binding Ligand by Marine Synechococcus (Cyanobacteria) in Response to Toxic Concentrations of Copper

Marine Synechococcus spp. are extremely sensitive to copper toxicity. Some strains have been shown to produce high-affinity, extracellular ligands of unknown structure which form complexes with free cupric ion. They are also known to produce metallothioneins (MT) in response to cadmium and zinc stress. In the present study, marine Synechococcus PCC 73109 (Agmenellum quadruplicatum BG-1) (Van Baalen) was exposed to three concentrations of CuSO4 for various times. Size exclusion chromatography, atomic absorption spectrophotometry, and reverse phase HPLC were used to isolate an intracellular copper binding ligand of low molecular weight (\u3c 6,500 Da). The ligand was detected after exposure to ≥ 8 μM CuSO4 for 2 hr in BG-11 medium. The intracellular ligand was characterized by electrospray mass spectrometry, amino acid analysis and a universal assay for siderophores. The ligand was not MT, phytochelatin or a siderophore. It is not a peptide but it contains lysine and an unidentified UV 254-absorbing constituent. This compound is a novel copper-binding ligand previously not reported in Synechococcus spp

Lost in Translation: A Standardized, Interdepartmental Approach to Improve the Safety of Inpatient Transitions of Care

AIM: During the 2016-2017 academic year physician perception of favorability regarding inpatient interunit handoffs will meet the national HSOPS benchmark without negatively impacting patient bed flow. All ACGME training programs at Thomas Jefferson University Hospital will expose their new trainees to standardized handoff training during orientation in June 2017 as well as adapt a framework for monitoring trainee compliance and proficiency.https://jdc.jefferson.edu/patientsafetyposters/1028/thumbnail.jp