Spacecraft Requirements Development and Tailoring

Spacecraft design is managed through the use of design requirements. Requirements are flowed from the highest level, the overall spacecraft, to systems, subsystems and ultimately individual components. Through the use of requirements, each part of the spacecraft will perform the functions that are required of it and will interface to the rest of the spacecraft. Functional requirements are used to make sure every component performs as expected and interface requirements ensure that each component works within the larger design environment where it operates. Writing good requirements is difficult and the verification of requirements can be expensive and time consuming. Because of this difficulty and expense, it is important that each requirement truly be required and critical to the overall performance of the vehicle. It is also important that requirements can be changed or eliminated as the system matures to minimize verification cost and schedule. The Capsule Parachute Assembly System (CPAS) Project is developing the parachute system for the NASA Multi-Purpose Crew Vehicle (MPCV) Orion Spacecraft. Throughout the development and qualification cycle for CPAS, requirements have been evaluated, added, eliminated, or more generically, tailored, to ensure that the system performs as required while minimizing the verification cost to the Program. One facet of this tailoring has been to delete requirements that do not add value to the overall spacecraft or are not needed. A second approach to minimize the cost of requirement verification has been to evaluate requirements based on the actual design as it has matured. As the design of the parachute system has become better understood, requirements that are not applicable have been eliminated. This paper will outline the evolution of CPAS requirements over time and will show how careful and considered changes to requirements can benefit the technical solution for the overall system design while allowing a Project to control costs

Localized Ferromagnetic Resonance in Inhomogeneous Thin Films

The effect of sample inhomogeneity on the ferromagnetic resonance linewidth is determined by diagonalization of a spin wave Hamiltonian for ferromagnetic thin films with inhomogeneities spanning a wide range of characteristic length scales. A model inhomogeneity is used that consist of size D grains and an anisotropy field Hp that varies randomly from grain to grain in a film with thickness d and magnetization Ms. The resulting linewidth agrees well with the two-magnon model for small inhomogeneity, HpD « πMsd. For large inhomogeneity, HpD » πMsd the precession becomes localized and the spectrum approaches that of local precession on independent grains

Eigen Modes and Ferromagnetic Resonance Line Width of Inhomogeneous Thin Films

In this paper, we describe modeling of the effects of magnetic inhomogeneity on ferromagnetic resonance line width using eigen mode analyses of inhomogeneous thin magnetic films

The New Biologics in Psoriasis: Possible Treatments for Alopecia Areata

Therapeutics in alopecia areata (AA) have remained relatively unchanged for many years, with few treatments having more than moderate effects in severely affected patients. The advent of the new biologic medications in the dermatologic world, however, particularly in psoriasis treatment, introduces possibilities of treatment for many other immune-mediated diseases

Earth as Humans’ Habitat: Global Climate Change and the Health of Populations

Human-induced climate change, with such rapid and continuing global-scale warming, is historically unprecedented and signifies that human pressures on Earth’s life-supporting natural systems now exceed the planet’s bio-geo-capacity. The risks from climate change to health and survival in populations are diverse, as are the social and political ramifications. Although attributing observed health changes in a population to the recent climatic change is difficult, a coherent pattern of climate- and weather-associated changes is now evident in many regions of the world. The risks impinge unevenly, especially on poorer and vulnerable regions, and are amplified by pre-existing high rates of climate-sensitive diseases and conditions. If, as now appears likely, the world warms by 3-5oC by 2100, the health consequences, directly and via massive social and economic disruption, will be severe. The health sector has an important message to convey, comparing the health risks and benefits of enlightened action to avert climate change and to achieve sustainable ways of living versus the self-interested or complacent inaction

Stealing Organs?

Every nine minutes, a new person joins a waitlist for an organ transplant, and every day, seventeen people die waiting for an organ that will never come. Because the need for organ transplants far outstrips the number of available organs, the policies and rules governing organ allocation in the United States are critically important and highly contentious. Recently, proponents of a new allocation system one focused more on sharing organs across the nation instead of allocating organs primarily to local transplant candidates have gained ground. Bolstered by two separate lawsuits in the past five years, advocates of greater national sharing have succeeded in changing the allocation rules for lungs and livers, with policies for other organs in development. This Article engages with the debate over whether national or local patients should receive priority under organ allocation systems. Focusing specifically on liver allocation, it provides an innovative empirical analysis of the primary arguments and evidence that those in favor of national allocation policies have used to support their preferred policies that the sickest patients should receive donated organs first, regardless of their location. While this argument is both ethically and intuitively appealing, those opposed to greater national organ sharing have argued that measures of sickest patients are both flawed and subject to manipulation. Greater national organ sharing can also exacerbate existing inequities in the organ transplant system as wealthy urban areas generally import organs from poorer and more rural parts of the country. Analyzing a dataset of every patient waitlisted for a liver between 2002 and 2017, this Article reveals, for the first time, a deeply troubling reality. The results of the analysis suggest that transplant professionals have routinely manipulated the waitlist priority of their patients. Moreover, this manipulation occurs more often in areas of the country that argue most vehemently in favor of national allocation policies. This Article argues that these recent policy changes, favoring greater national organ sharing, are extensions of the manipulative tactics revealed by the empirical analysis. Given the results of the empirical analysis, this Article argues that the time has come to formalize local priority in organ allocation policy by amending the National Organ TransplantAct. This amendment would roll back recent changes to promote greater national organ sharing that have been justified with manipulated evidence and prevent organs from moving from poorer to wealthier areas of the country. This rollback represents an important first step in combating inequities in the transplant system

Occupational Licensing and the Opioid Crisis

The United States\u27 affordable care crisis and chronic physician shortage have required nurse practitioners to assume increasingly important roles in the healthcare system. Nurse practitioners can address critical access-to-care problems, provide safe and effective care, and lower the cost of care. However, restrictive occupational licensing laws - specifically, scope-of-practice laws - have limited their ability to care for patients. Spurred by interest groups opposed to allowing nurse practitioners to practice independently, states require physician supervision of nurse practitioners. Research has discredited many of the traditional reasons for these restrictive laws, but emerging arguments assert that independent practice will deepen the ongoing opioid crisis by allowing unsupervised nurse practitioners to overprescribe opioids. The opioid crisis has become one of the defining public health emergency of this generation, so these arguments warrant serious investigation. If granting nurse practitioners independence will exacerbate the opioid epidemic, restricting their practices may be justified despite the clear benefits that independence could create for patients and the healthcare system. This Article provides new empirical evidence on the role of nurse practitioner independence in opioid prescriptions by analyzing a dataset of approximately 1.5 billion individual opioid prescriptions. Containing information on approximately 90% of all prescriptions filled at outpatient pharmacies between 2011 and 2018, this dataset provides unprecedented insight into the ongoing opioid epidemic. An analysis of these data reveals that allowing nurse practitioners to practice independently reduces the quantity of opioids prescribed across all physicians and nurse practitioners. Thus, this Article demonstrates that, contrary to exacerbating the opioid crisis, granting nurse practitioners independence is a valid policy option for addressing this crisis. These results can inform the ongoing state and national debates over nurse practitioner scope-of-practice laws and the opioid epidemic more generally. And based on these results, the Article proposes several policy options at the state and federal levels that could both address restrictive scope-of-practice laws and ameliorate the ongoing opioid crisis

Triple bypass: complicated paths to HIV escape

Human immunodeficiency virus (HIV) type 1 is highly efficient at evading immune responses and persisting, ultimately causing fatal immunodeficiency in some patients. Mutation in the epitopes recognized by cytolytic CD8+ T cells (CTLs) is one such escape process. A new study now shows that one HIV-1 escape mutation may also result in impaired dendritic cell (DC) activity, possibly impairing later T cell responses to the same and other epitopes. The new data complete our understanding of the mechanisms by which the CTL response to an immunodominant gag epitope presented by human histocompatibility leukocyte antigen (HLA)-B27 is evaded. The complexity of the full escape helps to explain why patients with this HLA type progress to AIDS more slowly than average

Insuring Apologies

Based on evidence demonstrating that an apology from a wrongdoer to a victim can assuage the victim\u27s anger, reduce the likelihood that the victim seeks legal redress, and facilitate settlement, state legislatures have passed apology laws to encourage the delivery of more apologies. Aimed primarily at medical malpractice litigation-a traditional locus of the tort reform effort-apology laws render apologies from physicians to patients inadmissible in subsequent legal proceedings. In theory, privileging apologies will encourage their use and reduce malpractice liability risk as patients assert fewer claims and settle those claims that are asserted. However, if apology laws encourage the delivery of insincere or disingenuous apologies, liability risk may increase, as such apologies exacerbate, rather than assuage, patient anger. Similarly, if apology laws encourage physicians to offer apologies that signal the occurrence of malpractice that otherwise would have gone undiscovered, physician liability risk may increase. Thus, apology laws may increase or decrease medical malpractice liability risk, and the nature of their ultimate effect has sparked an intense debate among scholars, policymakers, and physicians. This Article shows that apology laws have the counterintuitive effect of increasing liability risk. To evaluate whether apology laws work as intended, I examine a novel dataset of medical malpractice insurance premiums charged to physicians over nineteen years. This dataset provides a better measure of liability risk than publicly available-but incomplete-) data on malpractice claims used in prior work. Across three separate specialties (general surgery, internal medicine, and obstetrics/gynecology), my analysis demonstrates that apology laws increase the premiums charged to physicians by between 10 and 16 percent. These increases translate into substantial additional costs for individual physicians, with surgeons, internists, and obstetricians paying $5,000,$1,700, and $7,200 more in annual premiums, respectively. Based on strong and consistent evidence that apology laws increase, not decrease, malpractice liability risk, I argue that these laws fail to achieve their stated goal. Also on the basis of this evidence, I propose several alternative legal strategies for legislatures to accomplish their goals