Marine ice-sheet profiles and stability under Coulomb basal conditions

The behavior of marine-terminating ice sheets, such as the West Antarctic ice sheet, is of interest due to the possibility of rapid grounding-line retreat and consequent catastrophic loss of ice. Critical to modeling this behavior is a choice of basal rheology, where the most popular approach is to relate the ice-sheet velocity to a power-law function of basal stress. Recent experiments, however, suggest that near-grounding line tills exhibit Coulomb friction behavior. Here we address how Coulomb conditions modify ice-sheet profiles and stability criteria. The basal rheology necessarily transitions to Coulomb friction near the grounding line, due to low effective stresses, leading to changes in ice-sheet properties within a narrow boundary layer. Ice-sheet profiles ‘taper off’ towards a flatter upper surface, compared with the power-law case, and basal stresses vanish at the grounding line, consistent with observations. In the Coulomb case, the grounding-line ice flux also depends more strongly on flotation ice thickness, which implies that ice sheets are more sensitive to climate perturbations. Furthermore, with Coulomb friction, the ice sheet grounds stably in shallower water than with a power-law rheology. This implies that smaller perturbations are required to push the grounding line into regions of negative bed slope, where it would become unstable. These results have important implications for ice-sheet stability in a warming climate

Quantification of Dynamic Model Validation Metrics Using Uncertainty Propagation from Requirements

The Space Launch System, NASA's new large launch vehicle for long range space exploration, is presently in the final design and construction phases, with the first launch scheduled for 2019. A dynamic model of the system has been created and is critical for calculation of interface loads and natural frequencies and mode shapes for guidance, navigation, and control (GNC). Because of the program and schedule constraints, a single modal test of the SLS will be performed while bolted down to the Mobile Launch Pad just before the first launch. A Monte Carlo and optimization scheme will be performed to create thousands of possible models based on given dispersions in model properties and to determine which model best fits the natural frequencies and mode shapes from modal test. However, the question still remains as to whether this model is acceptable for the loads and GNC requirements. An uncertainty propagation and quantification (UP and UQ) technique to develop a quantitative set of validation metrics that is based on the flight requirements has therefore been developed and is discussed in this paper. There has been considerable research on UQ and UP and validation in the literature, but very little on propagating the uncertainties from requirements, so most validation metrics are "rules-of-thumb;" this research seeks to come up with more reason-based metrics. One of the main assumptions used to achieve this task is that the uncertainty in the modeling of the fixed boundary condition is accurate, so therefore that same uncertainty can be used in propagating the fixed-test configuration to the free-free actual configuration. The second main technique applied here is the usage of the limit-state formulation to quantify the final probabilistic parameters and to compare them with the requirements. These techniques are explored with a simple lumped spring-mass system and a simplified SLS model. When completed, it is anticipated that this requirements-based validation metric will provide a quantified confidence and probability of success for the final SLS dynamics model, which will be critical for a successful launch program, and can be applied in the many other industries where an accurate dynamic model is required

Hospitality codes and social exchange theory : the Pashtunwali and tourism in Afghanistan

The Afghan people are shrouded in rumor, myth and superstition. Drawing upon insights from military personnel, intelligence operatives, journalists and others, this study uses Social Exchange Theory (SET) to frame our understanding of their underpinning cultural code, the Pashtunwali. The study contributes both theoretically and empirically: The nature of the Pashtunwali highlights that SET cannot adequately frame some cultural exchange practices and a hybrid framework for negotiated and reciprocal exchange is presented. Furthermore, contextually, this is the first study that explores a code of hospitality through a social exchange lens to explore potential tourism development. A framework exists upon which commercial activity can be built without altering beliefs, social dynamics or day to day pursuits. For commercial development to be successful, it must yield similar or greater levels of income to those that currently exist, more importantly, traditions of autonomy and self-dependence will affect employment and training within an emergent tourism industry

Current Fertility Status Does Not Predict Sociosexual Attitudes and Desires in Normally Ovulating Women

Previous research has found that women at peak fertility show greater interest in extra-pair sex. However, recent replications have failed to detect this effect. In this study, we add to this ongoing debate by testing whether sociosexuality (the willingness to have sex in the absence of commitment) is higher in women who are at peak fertility. A sample of normally ovulating women (N = 773) completed a measure of sociosexuality and had their current fertility status estimated using the backward counting method. Contrary to our hypothesis, current fertility was unrelated to sociosexual attitudes and desires, even when relationship status was included as a moderator. These findings raise further doubts about the association between fertility and desire for extra-pair sex

Investigating the veracity of a sample of divergent published trial data in spinal pain

Evidence-based medicine is replete with studies assessing quality and bias, but few evaluating research integrity or trustworthiness. A recent Cochrane review of psychological interventions for chronic pain identified trials with a shared lead author with highly divergent results. We sought to systematically identify all similar trials from this author to explore their risk of bias, governance procedures, and trustworthiness. We searched OVID MEDLINE, EMBASE, CENTRAL, and PEDro from 2010 to December 22, 2021 for trials. We contacted the authors requesting details of trial registration, ethical approval, protocol, and access to the trial data for verification. We used the Cochrane risk-of-bias tool and the Cochrane Pregnancy and Childbirth group's Trustworthiness Screening Tool to guide systematic exploration of trustworthiness. Ten trials were included: 9 compared cognitive behavioural therapy and physical exercise to usual care, exercise alone, or physiotherapy and 1 compared 2 brief cognitive behavioural therapy programmes. Eight trials reported results divergent from the evidence base. Assessment of risk of bias and participant characteristics identified no substantial concerns. Responses from the lead author did not satisfactorily explain this divergence. Trustworthiness screening identified concerns about research governance, data plausibility at baseline, the results, and apparent data duplication. We discuss the findings within the context of methods for establishing the trustworthiness of research findings generally. Important concerns regarding the trustworthiness of these trials reduce our confidence in them. They should probably not be used to inform the results and conclusions of systematic reviews, in clinical training, policy documents, or any relevant instruction regarding adult chronic pain management