Groundwater Flow and Elastoplastic Stress-Strain Model for Cohesive Soils with Application to Channel Bank Stability

A saturated-unsaturated groundwater flow and elastoplastic stress-strain finite element model was developed for simulating the mechanical behavior of rill and gully sized channel banks. The model coupled the two-dimensional saturated-unsaturated groundwater flow equation with a plane strain formulation of the virtual work equation. The constitutive relationship used the modified Cam clay yield function. The model included the effects of seepage force and variation in soil cohesive strength due to changes in water content and void ratio. A staggered solution procedure was used in which the groundwater equation was solved first to determine seepage force and soil cohesive force, and then the stress-strain equation was solved. Upon reaching the failure point, the elastoplastic constitutive relationship was replaced with a weak elastic relationship. The model was verified by comparing predictions with (1) one-dimensional analytic solutions for unsaturated flow, saturated flow, and elastic strain; (2) other numerical solutions using the modified Cam clay yield function; (3) triaxial tests; and (4) laboratory experiments. The laboratory experiments employed a specially designed cyclic soil compactor and plexiglass flume to form and compact channel banks. The channel banks were subjected to a rising and falling hydrograph. Model simulation included groundwater movement into the channel bank, strain in the x-direction, and the location of finite elements which reached ultimate strength. Failure surfaces were delineated by zones of high x-strain in conjunction with finite elements which reached ultimate strength. The model provided good insight into the failure mechanism for popout failure and a reasonable prediction of plane failure

Providing a Safe Harbor for Those Who Play by the Rules: The Case for a Strong Regulatory Compliance Defense

On September 25, 2003, a fire broke out at the National Health Care (NHC) nursing home facility in Nashville, Tennessee, causing sixteen deaths and a number of injuries from smoke inhalation. Thirty-two victims subsequently filed suit against the nursing home, alleging that NHC was negligent for failing to install sprinklers in its facility. This claim was made notwithstanding the fact that applicable federal, state, and local safety regulations did not require the installation of sprinklers in this particular type of building, and notwithstanding that the NHC facility had been inspected by state fire inspectors just months before the fire and was found to be in compliance with all requirements of the fire code. NHC eventually settled these lawsuits in order to avoid the uncertainty and expense of further litigation. The NHC case illustrates how good-faith compliance with applicable safety regulations provides businesses with almost no protection against potentially devastating tort liability. The problem is with the legal rule that governs compliance with government regulations. In effect, most courts treat a defendant\u27s compliance with governmental regulations as evidence of due care, but allow the jury to find that a defendant was negligent, notwithstanding his or her compliance with legislative or administrative regulations. We shall refer to this as the traditional approach to regulatory compliance. The traditional approach originated in Grand Trunk Railway Co. of Canada v. Ives, decided by the United States Supreme Court in the late nineteenth century. Later, § 288C of the Second Restatement of Torts endorsed this version of the rule, declaring that compliance with safety regulations was not conclusive evidence that a defendant exercised due care. The American Law Institute is currently in the process of drafting the Third Restatement of Torts, and the revised version of the regulatory compliance defense is substantially similar to that of the Second Restatement. In our view, there are many problems with the traditional approach. First, legislatures and administrative agencies have more expertise than lay juries when it comes to determining efficient levels of safety, but the traditional approach allows lay juries to second guess them. Second, under our constitutional system, legislative bodies and administrative agencies, not courts, are responsible for making resource allocation and other policy decisions. Therefore, courts should accept the trade-offs that are often embodied in safety regulations instead of allowing plaintiffs to use the litigation process to substitute their own policy choices for those of legislative bodies and administrative agencies. Third, the traditional approach wrongly assumes that government safety regulations merely set minimum standards, while, in reality, modem regulations typically reflect state-of-the-art standards. Thus, by adding jury-created safety standards on top of existing regulatory requirements, the traditional approach to regulatory compliance adds to the cost of doing business without achieving significant safety gains. Fourth, the traditional approach to regulatory compliance undermines the principle of uniform application of regulatory standards. Because jury verdicts are seldom consistent, business entities are often subjected to nonuniform safety standards. Finally, the traditional approach deters useful economic activity by imposing potentially crushing tort liability upon those who have complied in good faith with regulatory standards. Part II of this Article examines the traditional approach to the regulatory compliance defense, beginning with the Supreme Court\u27s opinion in Grand Trunk Railway Co. of Canada v. Ives, and proceeding to the Restatement (Second) § 288C and the Restatement (Third) of Torts: Liability for Physical Harm § 16. In Part III, we discuss a number of cases that explicitly recognize a strong regulatory compliance defense, as well as cases that achieve a similar objective by expressly or impliedly applying the Second Restatement\u27s § 16, comment (a) exception. Part IV reviews some of the arguments that support a stronger regulatory compliance defense. These include: (1) the institutional competence argument, (2) the separation of powers argument, (3) the regulatory efficiency argument, (4) the nonuniform standards argument, and (5) the overdeterrence argument. In Part V, we focus on nursing home regulation to -see what impact a stronger regulatory compliance defense would have on this socially useful industry. Finally, in Part VI, we set forth a proposed alternative to the current version of Restatement (Third) of Torts: Liability for Physical Harm § 16

Quantitative measurement of tool embodiment for virtual reality input alternatives

Funding: Ontario Ministry of Research and Innovation and Science and the Natural Sciences and Engineering Research Council of Canada for funding.Virtual reality (VR) strives to replicate the sensation of the physical environment by mimicking people’s perceptions and experience of being elsewhere. These experiences are often mediated by the objects and tools we interact with in the virtual world (e.g., a controller). Evidence from psychology posits that when using the tool proficiently, it becomes embodied (i.e., an extension of one’s body). There is little work, however, on how to measure this phenomenon in VR, and on how different types of tools and controllers can affect the experience of interaction. In this work, we leverage cognitive psychology and philosophy literature to construct the Locus-of-Attention Index (LAI), a measure of tool embodiment. We designed and conducted a study that measures readiness-to-hand and unreadiness-to-hand for three VR interaction techniques: hands, a physical tool, and a VR controller. The study shows that LAI can measure differences in embodiment with working and broken tools and that using the hand directly results in more embodiment than using controllers.Postprin

Intrathoracic subclavian artery aneurysm repair in the thoracic endovascular aortic repair era

ObjectiveIntrathoracic subclavian artery aneurysms (SAAs) are rare aneurysms that often occur in association with congenital aortic arch anomalies and/or concomitant thoracic aortic pathology. The advent of thoracic endovascular aortic repair (TEVAR) methods may complement or replace conventional open SAA repair. Herein, we describe our experience with SAA repair in the TEVAR era.MethodsA retrospective review was performed of all intrathoracic SAAs repaired at a single institution since United States Food and Drug Administration approval of TEVAR in 2005.ResultsNineteen patients underwent 20 operations to repair 22 (13 native, nine aberrant) SAAs with an intrathoracic component. Mean SAA diameter was 3.1 cm (range, 1.6-6.0 cm). Mean patient age was 57 years (range, 24-80 years). Twenty-one percent (n = 4) of patients had a connective tissue disorder (two Loeys-Dietz, two Marfan). Thirty-six percent (n = 8) of SAAs were repaired by open techniques and 64% (n = 14) via a TEVAR-based approach. All TEVAR cases required proximal landing zone in the aortic arch (zone 0-2), and revascularization of at least one arch vessel was required in 83% (10/12) of patients. Concomitant repair of associated aortic pathology was performed in 50% (n = 10) of operations. Thirty-day/in-hospital rates of death, stroke, and permanent paraplegia/paraparesis were 5% (n = 1), 5% (n = 1), and 0%, respectively. Over mean (standard deviation) follow-up of 24 (21) months, 16% (n = 3) of patients required reintervention for subclavian artery bypass graft revision (n = 2) or type II endoleak (n = 1).ConclusionsThis is the largest single-institution series to date of TEVAR for SAA repair. Modern endovascular techniques expand SAA repair options with excellent results. The majority of SAAs and nearly all aberrant SAAs (Kommerell's diverticulum) can now be repaired using a TEVAR-based approach without the need for sternotomy or thoracotomy

Quantifying dilution and amplification in a community of hosts for tick-borne pathogens

Recent controversy over whether biodiversity reduces disease risk (dilution effect) has focused on the ecology of Lyme disease, a tick-borne zoonosis. A criticism of the dilution effect is that increasing host species richness might amplify disease risk, assuming that total host abundance, and therefore feeding opportunities for ticks, increase with species richness. In contrast, a dilution effect is expected when poor quality hosts for ticks and pathogens (dilution hosts) divert tick blood meals away from competent hosts. Even if host densities are additive, the relationship between host density and tick encounters can be nonlinear if the number of ticks that encounter a host is a saturating function of host density, which occurs if ticks aggregate on the remaining hosts rather than failing to find a host before death. Both dilution and amplification are theoretical possibilities, and assessing which is more prevalent required detailed analyses of empirical systems. We used field data to explore the degree of tick redistribution onto fewer individuals with variation in intraspecific host density and novel data-driven models for tick dynamics to determine how changes in vertebrate community composition influence the density of nymphs infected with the Lyme bacterium. To be conservative, we allowed total host density to increase additively with species richness. Our long-term field studies found that larval and nymphal ticks redistribute onto fewer individuals as host densities decline, that a large proportion of nymphs and adults find hosts, and that mice and chipmunks feed a large proportion of nymphs. White-footed mice, eastern chipmunks, short-tailed shrews, and masked shrews were important amplification hosts that greatly increased the density of infected nymphs. Gray squirrels and Virginia opossums were important dilution hosts. Removing these two species increased the maximum number of larvae attached to amplification hosts by 57%. Raccoons and birds were minor dilution hosts under some conditions. Even under the assumption of additive community assembly, some species are likely to reduce the density of infected nymphs as diversity increases. If the assumption of additivity is relaxed, then species that reduce the density of small mammals through predation or competition might substantially reduce disease risk.This is the publisher’s final pdf. The article is copyrighted by the Ecological Society of America and published by John Wiley & Sons, Inc. It can be found at: http://esajournals.onlinelibrary.wiley.com/hub/journal/10.1002/%28ISSN%291939-5582/Keywords: community ecology, Ixodes scapularis, ecosystem services, biodiversity, Lyme diseas

Associations of variants In the hexokinase 1 and interleukin 18 receptor regions with oxyhemoglobin saturation during sleep

Sleep disordered breathing (SDB)-related overnight hypoxemia is associated with cardiometabolic disease and other comorbidities. Understanding the genetic bases for variations in nocturnal hypoxemia may help understand mechanisms influencing oxygenation and SDB-related mortality. We conducted genome-wide association tests across 10 cohorts and 4 populations to identify genetic variants associated with three correlated measures of overnight oxyhemoglobin saturation: average and minimum oxyhemoglobin saturation during sleep and the percent of sleep with oxyhemoglobin saturation under 90%. The discovery sample consisted of 8,326 individuals. Variants with p −6 were analyzed in a replication group of 14,410 individuals. We identified 3 significantly associated regions, including 2 regions in multi-ethnic analyses (2q12, 10q22). SNPs in the 2q12 region associated with minimum SpO2 (rs78136548 p = 2.70 × 10−10). SNPs at 10q22 were associated with all three traits including average SpO2 (rs72805692 p = 4.58 × 10−8). SNPs in both regions were associated in over 20,000 individuals and are supported by prior associations or functional evidence. Four additional significant regions were detected in secondary sex-stratified and combined discovery and replication analyses, including a region overlapping Reelin, a known marker of respiratory complex neurons.These are the first genome-wide significant findings reported for oxyhemoglobin saturation during sleep, a phenotype of high clinical interest. Our replicated associations with HK1 and IL18R1 suggest that variants in inflammatory pathways, such as the biologically-plausible NLRP3 inflammasome, may contribute to nocturnal hypoxemia

Association between germline variants and somatic mutations in colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease with evidence of distinct tumor types that develop through different somatically altered pathways. To better understand the impact of the host genome on somatically mutated genes and pathways, we assessed associations of germline variations with somatic events via two complementary approaches. We first analyzed the association between individual germline genetic variants and the presence of non-silent somatic mutations in genes in 1375 CRC cases with genome-wide SNPs data and a tumor sequencing panel targeting 205 genes. In the second analysis, we tested if germline variants located within previously identified regions of somatic allelic imbalance were associated with overall CRC risk using summary statistics from a recent large scale GWAS (n similar or equal to 125 k CRC cases and controls). The first analysis revealed that a variant (rs78963230) located within a CNA region associated with TLR3 was also associated with a non-silent mutation within gene FBXW7. In the secondary analysis, the variant rs2302274 located in CDX1/PDGFRB frequently gained/lost in colorectal tumors was associated with overall CRC risk (OR = 0.96, p = 7.50e-7). In summary, we demonstrate that an integrative analysis of somatic and germline variation can lead to new insights about CRC

Effects of Terrestrial Buffer Zones on Amphibians on Golf Courses

A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians

Multivariate analysis of FcR-mediated NK cell functions identifies unique clustering among humans and rhesus macaques

Rhesus macaques (RMs) are a common pre-clinical model used to test HIV vaccine efficacy and passive immunization strategies. Yet, it remains unclear to what extent the Fc-Fc receptor (FcR) interactions impacting antiviral activities of antibodies in RMs recapitulate those in humans. Here, we evaluated the FcR-related functionality of natural killer cells (NKs) from peripheral blood of uninfected humans and RMs to identify intra- and inter-species variation. NKs were screened for FcγRIIIa (human) and FcγRIII (RM) genotypes (FcγRIII(a)), receptor signaling, and antibody-dependent cellular cytotoxicity (ADCC), the latter mediated by a cocktail of monoclonal IgG1 antibodies with human or RM Fc. FcγRIII(a) genetic polymorphisms alone did not explain differences in NK effector functionality in either species cohort. Using the same parameters, hierarchical clustering separated each species into two clusters. Importantly, in principal components analyses, ADCC magnitude, NK contribution to ADCC, FcγRIII(a) cell-surface expression, and frequency of phosphorylated CD3ζ NK cells all contributed similarly to the first principal component within each species, demonstrating the importance of measuring multiple facets of NK cell function. Although ADCC potency was similar between species, we detected significant differences in frequencies of NK cells and pCD3ζ+ cells, level of cell-surface FcγRIII(a) expression, and NK-mediated ADCC (P<0.001), indicating that a combination of Fc-FcR parameters contribute to overall inter-species functional differences. These data strongly support the importance of multi-parameter analyses of Fc-FcR NK-mediated functions when evaluating efficacy of passive and active immunizations in pre- and clinical trials and identifying correlates of protection. The results also suggest that pre-screening animals for multiple FcR-mediated NK function would ensure even distribution of animals among treatment groups in future preclinical trials