System design of the Pioneer Venus spacecraft. Volume 13: Preliminary development plans

This Pioneer Venus Study final report describes the following baseline configurations: (1) Thor/Delta Spacecraft Baseline is the baseline presented at the midterm review on 26 February 1973, (2) Atlas/Centaur Spacecraft Baseline is the baseline resulting from studies conducted since the midterm, but prior to receipt of the NASA execution phase RFP, and subsequent to decisions to launch both the multiprobe and orbiter missions in 1978 and use the Atlas/Centaur launch vehicle, and (3) Atlas/Centaur Spacecraft Midterm Baseline is the baseline presented at the 26 February 1973 review and is only used in the launch vehicle utilization trade study

The Paulsen Problem, Continuous Operator Scaling, and Smoothed Analysis

The Paulsen problem is a basic open problem in operator theory: Given vectors $u_1, \ldots, u_n \in \mathbb R^d$ that are $\epsilon$-nearly satisfying the Parseval's condition and the equal norm condition, is it close to a set of vectors $v_1, \ldots, v_n \in \mathbb R^d$ that exactly satisfy the Parseval's condition and the equal norm condition? Given $u_1, \ldots, u_n$, the squared distance (to the set of exact solutions) is defined as $\inf_{v} \sum_{i=1}^n \| u_i - v_i \|_2^2$ where the infimum is over the set of exact solutions. Previous results show that the squared distance of any $\epsilon$-nearly solution is at most $O({\rm{poly}}(d,n,\epsilon))$ and there are $\epsilon$-nearly solutions with squared distance at least $\Omega(d\epsilon)$. The fundamental open question is whether the squared distance can be independent of the number of vectors $n$. We answer this question affirmatively by proving that the squared distance of any $\epsilon$-nearly solution is $O(d^{13/2} \epsilon)$. Our approach is based on a continuous version of the operator scaling algorithm and consists of two parts. First, we define a dynamical system based on operator scaling and use it to prove that the squared distance of any $\epsilon$-nearly solution is $O(d^2 n \epsilon)$. Then, we show that by randomly perturbing the input vectors, the dynamical system will converge faster and the squared distance of an $\epsilon$-nearly solution is $O(d^{5/2} \epsilon)$ when $n$ is large enough and $\epsilon$ is small enough. To analyze the convergence of the dynamical system, we develop some new techniques in lower bounding the operator capacity, a concept introduced by Gurvits to analyze the operator scaling algorithm.Comment: Added Subsection 1.4; Incorporated comments and fixed typos; Minor changes in various place

Ancient channels of the Susquehanna River beneath Chesapeake Bay and the Delmarva Peninsula

Three generations of the ancestral Susquehanna River system have been mapped beneath Chesapeake Bay and the southern Delmarva Peninsula. Closely spaced seismic reflection profiles in the bay and boreholes in the bay and on the southern Delmarva Peninsula allow detailed reconstruction of each paleochannel system. The channel systems were formed during glacial low sea-level stands, and each contains a channel-fill sequence that records the subsequent transgression. The trunk channels of each system are 2 to 4 km wide and are incised 30 to SO m into underlying strata; they have irregular longitudinal profiles and very low gradients within the Chesapeake Bay area

Analytical Electrochemical Impedance Modeling of Li-Air Batteries under D.C. Discharge

An analytical impedance model and a small-signal equivalent circuit are derived for the impedance spectra of Li-air batteries with porous cathodes. The model takes into consideration the effects of the oxygen diffusion, double layer, and faradaic processes in the cathode and can be applied to Li-air batteries with organic and aqueous electrolytes operating under d.c. discharge. It is shown that the cathode of Li-air batteries can create two slightly asymmetrical semicircles on the Nyquist diagram: one at low frequencies, where the oxygen diffusion dominates the operation of the cell and one at medium frequencies due to the combined effects of the double-layer capacitance and faradaic processes. The second semicircle becomes negligibly small at low values of the cathode width or oxygen concentration. Both semicircles can degenerate into one large semicircle when the double layer capacitance is large enough and masks the effects of the faradaic processes, which happens at large values of the specific area of the cathode and double layer capacitance, or when the oxygen diffusion coefficient in the electrolyte is relatively large. They also degenerate into one semicircle when the porosity is decreased, for instance during the final period of the discharge of Li-air batteries with organic electrolyte, when the cathode is partly clogged with the deposit reaction products. The elements of the small-signal equivalent circuit are expressed in terms of the oxygen diffusion coefficient, oxygen concentration, discharge current, and other material and kinetic parameters, which make our model instrumental for extracting information about the material structure, reaction processes, and diffusion in the cathode. Based on the derived analytical results, we also propose a method to extract the effective value of the oxygen diffusion coefficient and reaction rate constant from the experimental impedance spectra of the cells. A simplified small-signal equivalent circuit model is also presented. This model contains only elementary components such as resistors and capacitors and can be implemented numerically in circuit simulators. Li-air batteries have attracted much attention in the last years particularly because of their high energy densities and specific capacities. 1-3 Depending on the type of the battery, the specific capacity is estimated to vary between 1,000-3,840 mAh/g, 4-6 which is a few times to more than one order of magnitude larger than the energy density of Li-ion batteries. This high specific capacity is mostly due to the fact that Li-air batteries use oxygen from the air instead of storing it internally and lithium metal at the anode instead of a composite material. Additionally, Li-air batteries are environmental safe and provide an oil-independent source of energy, which make them attractive in a broad area of applications including transportation, portable electronic devices, and green energy storage. Impedance analysis methods are often employed as convenient, nondestructive ways to analyze and predict the performance of batteries and other energy storage devices. 7 These methods can be used to extract information about the reaction and diffusion processes inside electrochemical devices, as well as about the state-of-charge, state-of-health, ohmic losses, and reliability of these devices. For instance, in the case of Li-ion batteries, one can predict the voltage and monitor the state-of-charge of the cells, 8,9 diagnose and investigate the electrochemical properties and determine the values of the Li diffusion coefficient, reaction rate, and other parameters using impedance spectroscopy. 16 In this article we develop an electrochemical impedance spectra model for Li-air batteries and relate the characteristics of the * Electrochemical Society Active Member. z E-mail: [email protected] spectra of these batteries to their geometrical dimensions, kinetic parameters, diffusion coefficient, porosity, and pore structure. We also propose a method to extract the effective value of the oxygen diffusion coefficient and reaction rate constant from the experimental impedance spectra of the cells. The results for the impedance spectra are derived under relatively general assumptions of the structure and type of the battery, by looking at the oxygen diffusion and faradaic processes in the porous cathode. Since the operation of Li-air batteries is dominated by these processes the effects of other phenomena such as the anode reaction rate or ion transport though the electrolyte can be neglected. We expect this model to be valid for a large number of Li-air or Li-oxygen systems, in which the oxygen diffusion-reaction plays a limiting factor. In particular, the model can be applied to primary and secondary Li-air batteries with organic and aqueous electrolytes as we will also discuss in the next section. Most of the existing work on the theoretical modeling of impedance spectra of electrochemical system is related to the study of Li-ion, other metal-ion or metal batteries, and electrocapacitors, which are dominated by Warburg diffusion or various versions and improvements the Warburg diffusion model (e.g. bounded Warburg models). These models are usually represented in the form of small-signal transmission line circuit models. They are relatively accurate for systems that can be modeled with a semi-infinite or bounded diffusion region and where the reaction takes place on the boundary of this region

Design of MARQUIS2: study protocol for a mentored implementation study of an evidence-based toolkit to improve patient safety through medication reconciliation.

BackgroundThe first Multi-center Medication Reconciliation Quality Improvement Study (MARQUIS1) demonstrated that implementation of a medication reconciliation best practices toolkit decreased total unintentional medication discrepancies in five hospitals. We sought to implement the MARQUIS toolkit in more diverse hospitals, incorporating lessons learned from MARQUIS1.MethodsMARQUIS2 is a pragmatic, mentored implementation QI study which collected clinical and implementation outcomes. Sites implemented a revised toolkit, which included interventions from these domains: 1) best possible medication history (BPMH)-taking; 2) discharge medication reconciliation and patient/caregiver counseling; 3) identifying and defining clinician roles and responsibilities; 4) risk stratification; 5) health information technology improvements; 6) improved access to medication sources; 7) identification and correction of real-time discrepancies; and, 8) stakeholder engagement. Eight hospitalists mentored the sites via one site visit and monthly phone calls over the 18-month intervention period. Each site's local QI team assessed opportunities to improve, implemented at least one of the 17 toolkit components, and accessed a variety of resources (e.g. implementation manual, webinars, and workshops). Outcomes to be assessed will include unintentional medication discrepancies per patient.DiscussionA mentored multi-center medication reconciliation QI initiative using a best practices toolkit was successfully implemented across 18 medical centers. The 18 participating sites varied in size, teaching status, location, and electronic health record (EHR) platform. We introduce barriers to implementation and lessons learned from MARQUIS1, such as the importance of utilizing dedicated, trained medication history takers, simple EHR solutions, clarifying roles and responsibilities, and the input of patients and families when improving medication reconciliation

The road to deterministic matrices with the restricted isometry property

The restricted isometry property (RIP) is a well-known matrix condition that provides state-of-the-art reconstruction guarantees for compressed sensing. While random matrices are known to satisfy this property with high probability, deterministic constructions have found less success. In this paper, we consider various techniques for demonstrating RIP deterministically, some popular and some novel, and we evaluate their performance. In evaluating some techniques, we apply random matrix theory and inadvertently find a simple alternative proof that certain random matrices are RIP. Later, we propose a particular class of matrices as candidates for being RIP, namely, equiangular tight frames (ETFs). Using the known correspondence between real ETFs and strongly regular graphs, we investigate certain combinatorial implications of a real ETF being RIP. Specifically, we give probabilistic intuition for a new bound on the clique number of Paley graphs of prime order, and we conjecture that the corresponding ETFs are RIP in a manner similar to random matrices.Comment: 24 page

A Virtual Reprise of the Stanley Milgram Obedience Experiments

BACKGROUND: Stanley Milgram's 1960s experimental findings that people would administer apparently lethal electric shocks to a stranger at the behest of an authority figure remain critical for understanding obedience. Yet, due to the ethical controversy that his experiments ignited, it is nowadays impossible to carry out direct experimental studies in this area. In the study reported in this paper, we have used a similar paradigm to the one used by Milgram within an immersive virtual environment. Our objective has not been the study of obedience in itself, but of the extent to which participants would respond to such an extreme social situation as if it were real in spite of their knowledge that no real events were taking place. METHODOLOGY: Following the style of the original experiments, the participants were invited to administer a series of word association memory tests to the (female) virtual human representing the stranger. When she gave an incorrect answer, the participants were instructed to administer an ‘electric shock’ to her, increasing the voltage each time. She responded with increasing discomfort and protests, eventually demanding termination of the experiment. Of the 34 participants, 23 saw and heard the virtual human, and 11 communicated with her only through a text interface. CONCLUSIONS: Our results show that in spite of the fact that all participants knew for sure that neither the stranger nor the shocks were real, the participants who saw and heard her tended to respond to the situation at the subjective, behavioural and physiological levels as if it were real. This result reopens the door to direct empirical studies of obedience and related extreme social situations, an area of research that is otherwise not open to experimental study for ethical reasons, through the employment of virtual environments

2019 Scholars at Work Conference Program

Program for the 2019 Scholars at Work Conference at Minnesota State University, Mankato on March 29, 2019

Results of the Active by Choice Today (ACT) Randomized Trial for Increasing Physical Activity in Low-Income and Minority Adolescents

Objective - This study reports the results of the Active by Choice Today (ACT) trial for increasing moderate-to-vigorous physical activity (MVPA) in low-income and minority adolescents. Design - The ACT program was a randomized controlled school-based trial testing the efficacy of a motivational plus behavioral skills intervention on increasing MVPA in underserved adolescents. Twenty-four middle schools were matched on school size, percentage minorities, percentage free or reduced lunch, and urban or rural setting before randomization. A total of 1,563 6th grade students (mean age, 11.3 years, 73% African American, 71% free or reduced lunch, 55% female) participated in either a 17-week (over one academic year) intervention or comparison after-school program. Main Outcome Measure - The primary outcome measure was MVPA based on 7-day accelerometry estimates at 2-weeks postintervention and an intermediate outcome was MVPA at midintervention. Results - At midintervention students in the intervention condition engaged in 4.87 greater minutes of MVPA per day (95% CI: 1.18 to 8.57) than control students. Students in intervention schools engaged in 9.11 min (95% CI: 5.73 to 12.48) more of MVPA per day than those in control schools during the program time periods; indicating a 27 min per week increase in MVPA. No significant effect of the ACT intervention was found outside of school times or for MVPA at 2-weeks postintervention. Conclusions - Motivational and behavioral skills programs are effective at increasing MVPA in low-income and minority adolescents during program hours, but further research is needed to address home barriers to youth MVPA