Cislunar Explorers: Lessons Learned from the Development of an Interplanetary CubeSat

The Cislunar Explorers mission is a pair of ~3U nanosatellites (named Hydrogen and Oxygen) launching as a single 6U CubeSat as part of NASA’s Artemis-1 mission on the Space Launch System (SLS). The two spacecraft will demonstrate technologies increasing the reach, flexibility, and cost-effectiveness of interplanetary smallsats. These innovations include water electrolysis propulsion, multi-body optical navigation, passive spin-stabilization, and the operation of femtosatellites beyond low earth orbit. Cislunar Explorers also serves as a pathfinder for demonstrating the utility and versatility of water for future In Situ Resource Utilization (ISRU) on space missions. Critical subsystems complement each other to reduce the cost and complexity. Water not only serves as the propellant for the propulsion system, but also as a radiation shield, electronics heat sink, and nutation damper. Each spacecraft’s spin provides attitude stabilization, separates electrolyzed gas from the water in the propulsion tank, simplifies the active attitude control system, and enables the optical navigation system to cover a panoramic view around the spacecraft. The unique elements of the mission spacecraft’s design provided advantages to traditional CubeSat architectures but also produced unexpected development challenges. By leveraging the lessons learned from the development of the Cislunar Explorers mission, future interplanetary missions can utilize its technology to reduce cost, risk, and complexity

A case control study of premorbid and currently reported physical activity levels in chronic fatigue syndrome

BACKGROUND: Patients with chronic fatigue syndrome typically report high levels of physical activity before becoming ill. Few studies have examined premorbid and current activity levels in chronically fatigued patients. METHODS: In a case-control study, 33 patients with chronic, unexplained, disabling fatigue attending a university-based clinic specializing in fatigue were compared to 33 healthy, age- and sex-matched controls. Patients rated their activity levels before their illness and currently, using scales designed for this purpose. Controls reported their level of activity of 2 years previously and currently. Chi-square analyses, Student's t tests, and Wilcoxon signed rank tests were used in pair matched analyses. RESULTS: Compared to healthy controls, patients with chronic, unexplained fatigue rated themselves as more active before their illness (p ≤ 0.001) and less active currently (p ≤ 0.001). The patients also reported they currently stood or walked less than the controls (median [inter-quartile range] = 4 [2-5] versus 9 [7.5–12] hours, p ≤ 0.001), and spent more time reclining (median [inter-quartile range] = 12 [10-16] versus 8 [8–9.5] hours, p ≤ 0.001). These differences remained significant for the subset of patients who met strict criteria for chronic fatigue syndrome or fibromyalgia. CONCLUSION: Patients with chronic, unexplained, disabling fatigue reported being more active before becoming ill than healthy controls. This finding could be explained by greater premorbid activity levels that could predispose to illness, or by an overestimation of previous activity. Either possibility could influence patients' perceptions of their current activity levels and their judgments of recovery. Perceived activity should be addressed as part of management of the illness

Attitudes towards fibromyalgia: A survey of Canadian chiropractic, naturopathic, physical therapy and occupational therapy students

<p>Abstract</p> <p>Background</p> <p>The frequent use of chiropractic, naturopathic, and physical and occupational therapy by patients with fibromyalgia has been emphasized repeatedly, but little is known about the attitudes of these therapists towards this challenging condition.</p> <p>Methods</p> <p>We administered a cross-sectional survey to 385 senior Canadian chiropractic, naturopathic, physical and occupational therapy students in their final year of studies, that inquired about attitudes towards the diagnosis and management of fibromyalgia.</p> <p>Results</p> <p>336 students completed the survey (response rate 87%). While they disagreed about the etiology (primarily psychological 28%, physiological 23%, psychological and physiological 15%, unsure 34%), the majority (58%) reported that fibromyalgia was difficult to manage. Respondants were also conflicted in whether treatment should prioritize symptom relief (65%) or functional gains (85%), with the majority (58%) wanting to do both. The majority of respondents (57%) agreed that there was effective treatment for fibromyalgia and that they possessed the required clinical skills to manage patients (55%).</p> <p>Chiropractic students were most skeptical in regards to fibromyalgia as a useful diagnostic entity, and most likely to endorse a psychological etiology. In our regression model, only training in naturopathic medicine (unstandardized regression coefficient = 0.33; 95% confidence interval = 0.11 to 0.56) and the belief that effective therapies existed (unstandardized regression coefficient = 0.42; 95% confidence interval = 0.30 to 0.54) were associated with greater confidence in managing patients with fibromyalgia.</p> <p>Conclusion</p> <p>The majority of senior Canadian chiropractic, naturopathic, physical and occupational therapy students, and in particular those with naturopathic training, believe that effective treatment for fibromyalgia exists and that they possess the clinical skillset to effectively manage this disorder. The majority place high priority on both symptom relief and functional gains when treating fibromyalgia.</p

Switches, Excitable Responses and Oscillations in the Ring1B/Bmi1 Ubiquitination System

In an active, self-ubiquitinated state, the Ring1B ligase monoubiquitinates histone H2A playing a critical role in Polycomb-mediated gene silencing. Following ubiquitination by external ligases, Ring1B is targeted for proteosomal degradation. Using biochemical data and computational modeling, we show that the Ring1B ligase can exhibit abrupt switches, overshoot transitions and self-perpetuating oscillations between its distinct ubiquitination and activity states. These different Ring1B states display canonical or multiply branched, atypical polyubiquitin chains and involve association with the Polycomb-group protein Bmi1. Bistable switches and oscillations may lead to all-or-none histone H2A monoubiquitination rates and result in discrete periods of gene (in)activity. Switches, overshoots and oscillations in Ring1B catalytic activity and proteosomal degradation are controlled by the abundances of Bmi1 and Ring1B, and the activities and abundances of external ligases and deubiquitinases, such as E6-AP and USP7

Integrated fiber-optic receivers

Integrated Fiber-Optic Receivers covers many aspects of the design of integrated circuits for fiber-optic receivers and other high-speed serial data links. Fundamental concepts are explained at the system level, circuit level, and semiconductor device level. Techniques for extracting timing information from the random data stream are described in considerable detail, as are all other aspects of receiver design. Integrated Fiber-Optic Receivers is organized in two parts. Part I covers the theory of communications systems as it applies to high-speed PAM (Pulse Amplitude Modulation) systems. The primary emphasis is on clock recovery circuits. Because theoretical concepts are generally grasped more easily by example, Part II is devoted to circuit design issues that illustrate example realizations of architectures described in Part I. Part II presents the transistor-level design, and measured results, of fundamental building blocks and test circuits. For practicing engineers, more than just reporting on the results of specific circuits, this book serves as a tutorial on the design of integrated high-speed broadband PAM data systems, such as: repeaters in long-haul, fiber-optic, trunk-lines transceivers for use in LANs and WANs; read channels for high-density data storage devices; and wireless communication handsets. Integrated Fiber-Optic Receivers may be used as a text for advanced courses in both analog circuit design and communication systems

The Evolution of Pd

Conspectus: Aromatic fluorides are prevalent in both agrochemical and pharmaceutical agents. However, methods for their rapid and general preparation from widely available starting materials are limited. Traditional approaches such as the Balz-Schiemann and Halex reactions require harsh conditions that limit functional group tolerance and substrate scope. The use of transition metals to affect C-F bond formation has provided some useful alternatives, but a broadly applicable method remains elusive. In contrast to the widespread use of Pd[superscript 0] /Pd [superscript II] catalysis for aryl-Z bond formation (Z = C, N, O), the analogous C-F cross-coupling process was unknown until fairly recently. In large part, this is due to the challenging Ar-F reductive elimination from Pd(II) intermediates. We have discovered that certain biaryl monophosphine ligands are uniquely capable of promoting this transformation. In this Account, we describe the discovery and development of a Pd-catalyzed C-F cross-coupling process and the systematic developments that made this once hypothetical reaction possible.Key to these developments was the discovery of an unusual in situ ligand modification process in which a molecule of substrate is incorporated into the ligand scaffold and the identity of the modifying group is crucial to the outcome of the reaction. This prompted the synthesis of a variety of "premodified" ligands and the identification of one that led to an expanded substrate scope, including (hetero)aryl triflates and bromides. Contemporaneously, a new Pd(0) precatalyst was also discovered that avoids the need to reduce Pd(II) in situ, a process that was often inefficient and led to the formation of byproducts.The use of inexpensive but hygroscopic sources of fluoride necessitates a reaction setup inside of a N[subscript 2] -filled glovebox, limiting the practicality of the method. Thus, a preformed wax capsule was designed to isolate the catalyst and reagents from the atmosphere and permit benchtop storage and setup. This new technology thus removes the requirement to employ a glovebox for the aromatic fluorination process and other air-sensitive protocols.In every catalyst system that we have studied to date, we observed the formation of regioisomeric fluoride side products. Through deuterium labeling studies it was found that they likely arise from a deprotonation event resulting in the formation of HF and a Pd-benzyne intermediate. Through an investigation of the mechanism of this undesired pathway, a new ligand was designed that substantially reduces the formation of the aryl fluoride regioisomer and even allows room-temperature Ar-F reductive elimination from a Pd(II) intermediate.National Institutes of Health (U.S.) (Grant R01GM46059)National Institutes of Health (U.S.) (Grant 1F32GM108092-01A1

Sampled-data switched-current analog 16-tap FIR filter with digitally programmable coefficients in 0.8 mu m CMOS

A hybrid analog-digital finite impulse response (FIR) filter has been designed using CMOS technology to achieve channel equalization in broadband networks and allow partial response maximum likelihood magnetic storage. The device's target specifications are 7 b of linearity at 20 MSample/s with a signal bandwidth from direct current to 10 MHz. It is suitable for 64-QAM digital modems over coaxial cables or twisted pair cables

622-MHz interpolating ring VCO with temperature compensation and jitter analysis

A 622-MHz Interpolating VCO has been designed using a 0.72 mu m CMOS technology for use as a clock recovery circuit in ATM Sonet OC-12 applications. A temperature compensated biasing scheme is adopted so that the VCO maintains its center frequency and tuning range throughout the temperature range 0 degree C-130 degree C. Simulation shows the sensitivity of the VCO center frequency achieves -100ppm/ degree C. Jitter analysis indicates an rms timing jitter due to thermal noise to be 365-fs. Power consumption is 65-mW from a 5-V supply