Logistic Postponement as a Risk Management Tool: A Real Options Valuation (ROV) Approach to Evaluate the Effectiveness of a Logistic Postponement Strategy in Mitigating the Demand Variability Risk in Global Supply Chains

Recent world events such as the coronavirus pandemic and the war in Ukraine have caused increases in supply chain disruptions along global supply chains. The resulting supply chain challenges necessitate an increased effort in improving supply chain risk management for companies around the world. One source of uncertainty that is increasingly difficult to deal with is demand variability. With both supply and demand becoming increasingly difficult to predict, companies need tools to manage demand variability. Our work evaluates a logistic postponement solution to demand variability where safety stock is shipped from an overseas supplier to a distribution center instead of being shipped directly to retailers. By taking advantage of risk pooling, the proposed strategy aims at reducing stockouts at retailers well also reducing the present value of total costs incurring along the supply chain. A real options valuation (ROV) approach is used in this thesis to present both a theoretical model and a computational model. The theoretical model aims to provide an approach for supply chain practitioners to compare the logistic postponement strategy to their current strategy using historical data. On the other hand, the computational model incorporates some simplifications in the theoretical model to avail it for simulation. Sensitivity analyses conducted aim to provide an analysis on the potential cost savings and stockout reductions a logistic postponement strategy can provide

Double-Layer Systems at Zero Magnetic Field

We investigate theoretically the effects of intralayer and interlayer exchange in biased double-layer electron and hole systems, in the absence of a magnetic field. We use a variational Hartree-Fock-like approximation to analyze the effects of layer separation, layer density, tunneling, and applied gate voltages on the layer densities and on interlayer phase coherence. In agreement with earlier work, we find that for very small layer separations and low layer densities, an interlayer-correlated ground state possessing spontaneous interlayer coherence (SILC) is obtained, even in the absence of interlayer tunneling. In contrast to earlier work, we find that as a function of total density, there exist four, rather than three, distinct noncrystalline phases for balanced double-layer systems without interlayer tunneling. The newly identified phase exists for a narrow range of densities and has three components and slightly unequal layer densities, with one layer being spin polarized, and the other unpolarized. An additional two-component phase is also possible in the presence of sufficiently strong bias or tunneling. The lowest-density SILC phase is the fully spin- and pseudospin-polarized ``one-component'' phase discussed by Zheng {\it et al.} [Phys. Rev. B {\bf 55}, 4506 (1997)]. We argue that this phase will produce a finite interlayer Coulomb drag at zero temperature due to the SILC. We calculate the particle densities in each layer as a function of the gate voltage and total particle density, and find that interlayer exchange can reduce or prevent abrupt transfers of charge between the two layers. We also calculate the effect of interlayer exchange on the interlayer capacitance.Comment: 35 pages, 19 figures included. To appear in PR

The impact of physical inactivity on glucose homeostasis when diet is adjusted to maintain energy balance in healthy, young males

Background & aims: It is unclear if dietary adjustments to maintain energy balance during reduced physical activity can offset inactivity-induced reductions in insulin sensitivity and glucose disposal to produce normal daily glucose concentrations and meal responses. Therefore, the aim of the present study was to examine the impact of long-term physical inactivity (60 days of bed rest) on daily glycemia when in energy balance.Methods: Interstitial glucose concentrations were measured using Continuous Glucose Monitoring Systems (CGMS) for 5 days before and towards the end of bed rest in 20 healthy, young males (Age: 34 ± 8 years; BMI: 23.5 ± 1.8 kg/m2). Energy intake was reduced during bed rest to match energy expenditure, but the types of foods and timing of meals was maintained. Fasting venous glucose and insulin concentrations were determined, as well as the change in whole-body glucose disposal using a hyperinsulinemic-euglycemic clamp (HIEC).Results: Following long-term bed rest, fasting plasma insulin concentration increased 40% (p = 0.004) and glucose disposal during the HIEC decreased 24% (p < 0.001). Interstitial daily glucose total area under the curve (tAUC) from pre-to post-bed rest increased on average by 6% (p = 0.041), despite a 20 and 25% reduction in total caloric and carbohydrate intake, respectively. The nocturnal period (00:00–06:00) showed the greatest change to glycemia with glucose tAUC for this period increasing by 9% (p = 0.005). CGMS measures of daily glycemic variability (SD, J-Index, M-value and MAG) were not changed during bed rest.Conclusions: Reduced physical activity (bed rest) increases glycemia even when daily energy intake is reduced to maintain energy balance. However, the disturbance to daily glucose homeostasis was much more modest than the reduced capacity to dispose of glucose, and glycemic variability was not negatively affected by bed rest, likely due to positive mitigating effects from the contemporaneous reduction in dietary energy and carbohydrate intake.Clinical trials record: NCT03594799 (registered July 20, 2018) (https://clinicaltrials.gov/ct2/show/NCT03594799)

Preclinical models of myocardial infarction: from mechanism to translation

Approximately 7 million people are affected by acute myocardial infarction (MI) each year, and despite significant therapeutic and diagnostic advancements, MI remains a leading cause of mortality worldwide. Pre-clinical animal models have significantly advanced our understanding of MI and enable the development of therapeutic strategies to combat this debilitating disease. Notably, some drugs currently used to treat MI and heart failure (HF) in patients had initially been studied in pre-clinical animal models. Despite this, pre-clinical models are limited in their ability to fully recapitulate the complexity of MI in humans. The pre-clinical model must be carefully selected to maximise the translational potential of experimental findings. This review describes current experimental models of MI and considers how they have been used to understand drug mechanisms of action (MOA) and support translational medicine development

Licking planets and stomping on buildings: children’s interactions with curated spaces in virtual reality

This visual essay draws upon data from a commercially funded project on which I was the lead researcher (Yamada-Rice et al. 2017). The study was undertaken to develop a set of best practices for the production of Virtual Reality (VR) content for children. The project combined large-scale quantitative data from a global survey with qualitative methods used to observe and interview a smaller sample of 8–12 year-olds. There was also a health and safety element that tested for changes in vision and balance pre and post VR use. This article draws from the qualitative dataset that investigated children’s interaction with a range of VR content and devices, the aspects that engaged them and how easy it was to use