Asymmetrical booster ascent guidance and control system design study. Volume 1: Summary

Dynamics and control, stability, and guidance analyses are summarized for the asymmetrical booster ascent guidance and control system design studies, performed in conjunction with space shuttle planning. The mathematical models developed for use in rigid body and flexible body versions of the NASA JSC space shuttle functional simulator are briefly discussed, along with information on the following: (1) space shuttle stability analysis using equations of motion for both pitch and lateral axes; (2) the computer program used to obtain stability margin; and (3) the guidance equations developed for the space shuttle powered flight phases

The Incidence and Incubation Period of False Positive Cultures in Shoulder Surgery

Background Postoperative shoulder infection (PSI) is a significant complication requiring timely identification and treatment. Indolent infections such as those involving Cutibacterium acnes (C. acnes, recently reclassified from Propionibacterium acnes 1) provide a diagnostic dilemma as they present differently without the acute symptoms associated with most postoperative bone and joint infections. Furthermore, C. acnes is thought to be a common contaminant isolated from intraoperative cultures. With no consensus algorithm, long hold cultures play a major role in guiding management decisions in potential PSI. Our study seeks to determine the incidence of positive cultures in both open and arthroscopic procedures in non-infected patients as well as clarify whether or not an increase in the incubation time frame leads to an increased rate of culture growth. Method ology: One hundred patients were prospectively enrolled into either an open and arthroscopic procedure group. Patients with abnormal inflammatory labs, history of previous shoulder surgery, or corticosteroid injection within six months of surgery were excluded from the study. Three cultures were obtained for each patient (1superficial tissue culture, 2- tissue culture, and 3- “sterile” control swab). Cultures were held for 28 days and checked on regular intervals. All patients were followed clinically for 6 months to ensure no signs of postoperative infection. Results Ultimately ninety-five patients were included in the final analysis. The false-positive rate in open shoulder surgery was 17.02% and arthroscopic shoulder surgery was 10.4%. The incidence of positive C. acnes cultures was 6.4% in the open group while C. acnes was not isolated in the arthroscopic group. All positive bacterial cultures were reported within seven days of collection. One culture was positive for “mold” at 26 days. Conclusion A relatively high false-positive culture rate occurred in both open and arthroscopic shoulder surgery. C. acnes was the most commonly identified bacteria in cultures in the open surgery group. Knowledge of one’s own institutional false-positive culture rate could be important in avoiding potentially inappropriate treatment. Additionally, we found that holding cultures longer than 14 days did not lead to an increased rate of false positive culture results

Political Regimes and Sovereign Credit Risk in Europe, 1750-1913

This article uses a new panel data set to perform a statistical analysis of political regimes and sovereign credit risk in Europe from 1750 to 1913. Old Regime polities typically suffered from fiscal fragmentation and absolutist rule. By the start of World War I, however, many such countries had centralized institutions and limited government. Panel regressions indicate that centralized and?or limited regimes were associated with significant improvements in credit risk relative to fragmented and absolutist ones. Structural break tests also reveal close relationships between major turning points in yield series and political transformations

Shaping and Structuring Supramolecular Gels

Supramolecular gels assemble via non-covalent interactions between low-molecular-weight gelators (LMWGs). The gels form a solid-like nanoscale network spanning a liquid-like continuous phase, translating molecular-scale information into materials performance. However, gels based on LMWGs are often difficult to manipulate, easily destroyed and have poor rheological performance. The recurring image of newly-discovered supramolecular gels is that of an inverted vial showing that the gel can support its own weight against gravity. Such images reflect the limitation that these gels simply fill the vessel in which they are made, with limited ability to be shaped. This property prevents supramolecular gels from having the same impact as polymer gels, despite greater synthetic tunability, reversibility and bio/environmental compatibility. In this Review, we evaluate strategies for imposing different shapes onto supramolecular gels and for patterning structures within them. We review fabrication methods including moulding, self-healing, 3D printing, photopatterning, diffusion and surface-mediated patterning. We discuss gelator chemistries amenable to each method, highlighting how a multi-component approach can aid shaping and structuring. Supramolecular gels with defined shapes, or patterned structures with precisely-controlled compositions, have the potential to intervene in applications such as tissue engineering and nanoscale electronics, as well as opening-up new technologies