A widely used one-dimensional nonlinear effective stress site response analysis program is used to model the response of potentially liquefiable soils during strong shaking. Ground motion records ...from six events of the 2010–2011 Canterbury earthquake sequence and the extensive site investigation data that have been obtained for the Christchurch area provide the basis for the analyses. The results of the analyses depend significantly on the input motions and soil profile characterization, so these important aspects are examined. Deconvolved Riccarton Gravel input motions were generated, because recorded rock or firm layer motions were not available. Nonlinear effective stress seismic site response analyses are shown to capture key aspects of the observed soil response through the comparison of acceleration response spectra of calculated surface motions to those of recorded surface motions; however, equivalent-linear and total stress nonlinear analyses capture these aspects as well. Biases in the computed motions compared to recorded motions were realized for some cases but they can be attributed primarily to the uncertainty in the development of the input motions used in the analyses.
•Strong motion records from the Canterbury earthquake sequence are examined.•Perform 1D nonlinear effective stress site response analyses at liquefiable sites.•Surface motions are deconvolved for use as input motions for site response analyses.•Key aspects of recorded motions are generally captured by the analyses.•Observed bias is due to pore water pressure model in analyses and input motions.
The 2010–2011 Canterbury earthquake sequence provides an exceptional opportunity to investigate the effects of varying degrees of liquefaction on the built environment. Significant ground settlements ...and building damage in the Central Business District (CBD) were observed for the Christchurch earthquake. The results of CPTs and soil index tests from exploratory borings performed in the CBD are combined with cyclic triaxial (CTX) test results to characterize the soil deposits at several buildings sites. Conventional one-dimensional liquefaction-induced ground settlement procedures do not capture shear-induced deformation mechanisms and the effects of ground loss due to sediment ejecta. Improved procedures are required. Nonlinear effective stress analyses using robust soil constitutive models calibrated through CTX tests provide a means for developing these procedures. The CTX tests estimate generally consistent cyclic resistances as the CPT-based methods for medium dense sands and silty sands; however, the CTX tests provide useful insights regarding pore water pressure response and strain development. Correlations and CTX tests performed on loose clean sands indicate that these specimens were disturbed by the sampling process. Interim findings from this ongoing study are presented, and preliminary recommendations for evaluating the seismic performance of buildings with shallow foundations at sites with liquefiable soils are provided.
•Canterbury earthquakes provide an exceptional opportunity to investigate the effects of varying degrees of liquefaction.•Cyclic triaxial test results are combined with CPTs and borings to characterize soil deposits at sites in Christchurch.•Cyclic triaxial tests provide cyclic resistances consistent with CPT-based methods for medium dense sands and silty sands.•Dames & Moore hydraulic piston sampler was not able to retrieve “undisturbed” loose clean sands samples.•Recommendations are provided for evaluating shallow-founded building performance at sites with liquefiable soils.
AbstractInsights regarding the response of shallow foundation soils from building sites in the central business district (CBD) of Christchurch, New Zealand, that experienced liquefaction during the ...2010–2011 Canterbury earthquake sequence (CES) are provided through an examination of cyclic and monotonic triaxial test data. An emphasis is placed on understanding the liquefaction resistance and large-strain steady-state response of key soils so that case histories of buildings damaged because of soil liquefaction during the CES can be developed. Comparisons of cyclic resistances from cyclic triaxial (CTX) testing and a cone penetration test (CPT)–based triggering correlation showed good agreement. Cyclic testing showed that silty sands and clean sands responded similarly in cyclic loading. However, silts tended to have flatter cyclic resistance curves. Interpretation of large-strain monotonic triaxial testing of reconstituted soil specimens provides information on the steady-state lines of the sandy soils of the CBD. The insights garnered from this laboratory testing program are critical for characterizing the Christchurch soils, as only limited cyclic testing results are available.
The 2010–2011 Canterbury earthquake sequence provides an exceptional opportunity to investigate the effects of varying degrees of liquefaction on the built environment. Significant ground settlements ...and building damage in the Central Business District (CBD) were observed for the Christchurch earthquake. The results of CPTs and soil index tests from exploratory borings performed in the CBD are combined with cyclic triaxial (CTX) test results to characterize the soil deposits at several buildings sites. Conventional one-dimensional liquefaction-induced ground settlement procedures do not capture shear-induced deformation mechanisms and the effects of ground loss due to sediment ejecta. Improved procedures are required. Nonlinear effective stress analyses using robust soil constitutive models calibrated through CTX tests provide a means for developing these procedures. The CTX tests estimate generally consistent cyclic resistances as the CPT-based methods for medium dense sands and silty sands; however, the CTX tests provide useful insights regarding pore water pressure response and strain development. Correlations and CTX tests performed on loose clean sands indicate that these specimens were disturbed by the sampling process. Interim findings from this ongoing study are presented, and preliminary recommendations for evaluating the seismic performance of buildings with shallow foundations at sites with liquefiable soils are provided.
•Canterbury earthquakes provide an exceptional opportunity to investigate the effects of varying degrees of liquefaction.•Cyclic triaxial test results are combined with CPTs and borings to characterize soil deposits at sites in Christchurch.•Cyclic triaxial tests provide cyclic resistances consistent with CPT-based methods for medium dense sands and silty sands.•Dames & Moore hydraulic piston sampler was not able to retrieve “undisturbed” loose clean sands samples.•Recommendations are provided for evaluating shallow-founded building performance at sites with liquefiable soils.
Objectives:
This study aims to assess the feasibility of using hemofiltration for ammonia clearance in low body weight infants with an inborn error of metabolism.
Design:
A study of two cases.
...Setting:
Quaternary pediatric hospital (Saint Louis Children's Hospital) NICU and PICU.
Patients:
Infants <6 months of age with an ICD-9 diagnosis of 270.6 (hyperammonemia).
Interventions:
Continuous renal replacement therapy (CRRT).
Measurements and Main Results:
We measure serum ammonia levels over time and the rate of ammonia clearance over time. Continuous renal replacement therapy was more effective than scavenger therapy alone (Ammonul™) for rapid removal of ammonia in low weight infants (as low as 2.5 kg).
Conclusions:
Continuous renal replacement therapy is technically feasible in low weight infants with severe hyperammonemia secondary to an inborn error of metabolism.
Stress in socially subordinate male rats, associated with aggressive attacks by dominant males, was studied in a group-housing
context called the visible burrow system (VBS). It has been established ...that subordinate males have reduced serum testosterone
(T) and higher corticosterone (CORT) relative to dominant and singly housed control males. The relationship of the decreased
circulating T levels in subordinate males to changes in serum LH concentrations has not been evaluated previously. Since decreases
in LH during stress may cause reductions in Leydig cell steroidogenic activity, the present study defined the temporal profiles
of serum LH, T, and CORT in dominant and subordinate males on Days 4, 7, and 14 of a 14-day housing period in the VBS. The
same parameters were followed in serum samples from single-housed control males. Leydig cells express glucocorticoid receptors
and may also be targeted for direct inhibition of steroidogenesis by glucocorticoid. We hypothesize that Leydig cells are
protected from inhibition by CORT at basal concentrations through oxidative inactivation of glucocorticoid by 11β-hydroxysteroid
dehydrogenase (11βHSD). However, Leydig cell steroidogenesis is inhibited when 11βHSD metabolizing capacity is exceeded. Therefore,
11βHSD enzyme activity levels were measured in Leydig cells of VBS-housed males at the same time points. Significant increases
in LH and T relative to control were observed in the dominant animals on Day 4, which were associated with the overt establishment
of behavioral dominance as evidenced by victorious agonistic encounters. Serum LH and T were lower in subordinate males on
Day 7, but T alone was lower on Day 14, suggesting that lowered LH secretion in subordinates may gradually be reversed by
declines in androgen-negative feedback. Serum CORT levels were higher in subordinate males compared to control at all three
time points. In contrast, oxidative 11βHSD activity in Leydig cells of dominant males was higher relative to control and unchanged
in subordinates. These results suggest the following: 1) failure of Leydig cells of subordinate males to compensate for increased
glucocorticoid action during stress, by increasing 11βHSD oxidative activity, potentiates stress-mediated reductions in T
secretion; and 2) an inhibition of the reproductive axis in subordinate males at the level of the pituitary.
Brain-directed critical care for children is a relatively new area of subspecialization in pediatric critical care. Pediatric neurocritical care teams combine the expertise of neurology, ...neurosurgery, and critical care medicine. The positive impact of delivering specialized care to pediatric patients with acute neurological illness is becoming more apparent, but the optimum way to implement and sustain the delivery of this is complicated and poorly understood. We aim to provide emerging evidence supporting that effective implementation of pediatric neurocritical care pathways can improve patient survival and outcomes. We also provide an overview of the most effective strategies across the field of implementation science that can facilitate deployment of neurocritical care pathways in the pediatric ICU.
Implementation strategies can broadly be grouped according to six categories: planning, educating, restructuring, financing, managing quality, and attending to the policy context. Using a combination of these strategies in the last decade, several institutions have improved patient morbidity and mortality. Although much work remains to be done, emerging evidence supports that implementation of evidence-based care pathways for critically ill children with two common neurological diagnoses - status epilepticus and traumatic brain injury - improves outcomes.
Pediatric and neonatal neurocritical care programs that support evidence-based care can be effectively structured using appropriately sequenced implementation strategies to improve outcomes across a variety of patient populations and in a variety of healthcare settings.
Stress in socially subordinate male rats, associated with aggressive attacks by dominant males, was studied in a group-housing context called the visible burrow system (VBS). It has been established ...that subordinate males have reduced serum testosterone (T) and higher corticosterone (CORT) relative to dominant and singly housed control males. The relationship of the decreased circulating T levels in subordinate males to changes in serum LH concentrations has not been evaluated previously. Since decreases in LH during stress may cause reductions in Leydig cell steroidogenic activity, the present study defined the temporal profiles of serum LH, T, and CORT in dominant and subordinate males on Days 4, 7, and 14 of a 14-day housing period in the VBS. The same parameters were followed in serum samples from single-housed control males. Leydig cells express glucocorticoid receptors and may also be targeted for direct inhibition of steroidogenesis by glucocorticoid. We hypothesize that Leydig cells are protected from inhibition by CORT at basal concentrations through oxidative inactivation of glucocorticoid by 11β-hydroxysteroid dehydrogenase (11βHSD). However, Leydig cell steroidogenesis is inhibited when 11βHSD metabolizing capacity is exceeded. Therefore, 11βHSD enzyme activity levels were measured in Leydig cells of VBS-housed males at the same time points. Significant increases in LH and T relative to control were observed in the dominant animals on Day 4, which were associated with the overt establishment of behavioral dominance as evidenced by victorious agonistic encounters. Serum LH and T were lower in subordinate males on Day 7, but T alone was lower on Day 14, suggesting that lowered LH secretion in subordinates may gradually be reversed by declines in androgen-negative feedback. Serum CORT levels were higher in subordinate males compared to control at all three time points. In contrast, oxidative 11βHSD activity in Leydig cells of dominant males was higher relative to control and unchanged in subordinates. These results suggest the following: 1) failure of Leydig cells of subordinate males to compensate for increased glucocorticoid action during stress, by increasing 11βHSD oxidative activity, potentiates stress-mediated reductions in T secretion; and 2) an inhibition of the reproductive axis in subordinate males at the level of the pituitary.
The strong shaking of the 2010–2011 Canterbury earthquake sequence caused widespread liquefaction in much of the city of Christchurch, NZ, including large parts of the central business district ...(CBD). Understanding the effects of liquefaction on soil and building response is an area of earthquake engineering that continues to challenge practitioners and researchers. This challenging topic makes the study of case histories, such as those provided by the Canterbury earthquakes, an essential component to characterizing and understanding the effects of soil liquefaction on building performance. This thesis focuses on providing insights regarding the seismic response of liquefiable soils through the use of information and data collected in Christchurch, NZ following the Canterbury earthquake sequence. Nonlinear effective stress site response analyses are often used by engineers to model the dynamic response of potentially liquefiable soils during strong shaking. For the presented research, a widely used one-dimensional nonlinear effective stress site response analysis program is used to perform this modeling. Ground motions recorded during six events of the 2010–11 Canterbury earthquake sequence are used in conjunction with the extensive site investigation data that has been obtained in Christchurch to complete site response analyses at several strong motion station sites in the greater Christchurch area. Deconvolved Riccarton Gravel input motions were generated, because representative, recorded rock or firm layer base-motions were not available in the Christchurch area. Nonlinear effective stress seismic site response analyses are shown to capture key aspects of the observed soil response through the comparison of acceleration response spectra of calculated surface motions to those of recorded surface motions; however, equivalent-linear and total stress nonlinear analyses are shown to capture these aspects as well. Biases in the computed motions compared to recorded motions were realized for some cases, but they can be attributed primarily to the uncertainty in the development of the input motions used in the analyses. The study of the consequences of liquefaction on building performance is a complex soil-structure interaction problem that requires the use of well-documented case histories for validation purposes. An extensive site investigation and advanced laboratory testing program was carried out in Christchurch, NZ from April to October of 2014. The aim of this work was to provide characterization of the liquefaction resistance of foundation soils from building sites affected by liquefaction during the Canterbury earthquakes. In-situ penetration tests, such as CPT, are valuable methods for gaining an initial understanding of a site’s characteristics and the expected performance of critical soil layers. However, to understand fully the complex response of soil at the element level, laboratory testing of relatively undisturbed soil specimens provide unique insights. To accomplish these goals, “undisturbed” sampling and triaxial testing (monotonic and cyclic) were performed on soils from key building sites in Christchurch’s CBD. High quality sampling and testing could be achieved for most of the predominantly silty and sandy soils in the CBD. Test results indicate, though, that loose clean sand specimens were densified significantly during the sampling with the Dames & Moore hydraulic fixed-piston sampler (an Osterberg-type thin-walled sampler). The cyclic resistances measured in the tests on “undisturbed” specimens were generally consistent with those estimated using empirical simplified liquefaction triggering procedures. Important insights regarding the cyclic response of the shallow CBD soils were obtained through the laboratory testing carried out as a part of the research presented in this thesis. Triaxial testing of “undisturbed” soil specimens proved important in understanding not only the stress-strain response of the studied soils, but also allowed for further knowledge regarding the pore water pressure response of the tested soils during both cyclic and monotonic loading. Importantly, insights into how various soil types of the CBD responded to cyclic loading were gained through comparisons of cyclic triaxial (CTX) tests performed on a variety of sand and silty sand soils. It was seen through CTX results comparisons that silty sands (soils classified as SM) and clean sands (SP and SP-SM) responded similarly in cyclic loading, even when the fines content of the tested specimens differed. Monotonic triaxial testing was also performed on reconstituted specimens to characterize the steady state response of several soil units in the CBD. The extensive insight garnered from laboratory testing is critical for informing researchers and engineers studying the case histories provided by the Canterbury earthquakes of buildings founded on liquefiable soils, especially those using numerical-based soil-structure interaction analyses. The results of the monotonic and cyclic tests performed as part of this study provide useful data for calibrating advanced numerical models. Appendices are included as a part of this dissertation to provide supporting information and data not included in the main body of the thesis. (Abstract shortened by UMI.)
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