Orbiter/payload proximity operations: Lateral approach technique

The lateral approach is presented for proximity operations associated with the retrieval of free flying payloads. An out of plane final approach emphasizing onboard software support is recommended for all except the latter segment of the final approach in which manual control is considered mandatory. An overall assessment of various candidate proximity operations techniques are made

Development of a method for optimal maneuver analysis of complex space missions

A system that allows mission planners to find optimal multiple-burn space trajectories easily is described. Previously developed methods with different gravity assumptions perform the optimization function. The power of these programs is extended by a method of costate estimation. A penalty function method of constraining coast arc times to be positive is included. The capability of the method is demonstrated by finding the optimal control for three different space missions. These include a shuttle abort-once-around mission and two- and three-burn geosynchronous satellite-placement missions

Ethene Elimination from CH3CH2NHCH2+: Reaction Pathways at the Boundary Between Stepwise and Concerted Processes

AbstractThe elimination of ethene from CH3CH2NHCH2+ is characterized by ab initio procedures. This reaction occurs through several asynchronous stages, but without passing through formal intermediates. A potential energy barrier to hydrogen migration from the β carbon to N is largely determined by the energy required to cleave the CN bond, but is lowered slightly by H transfer from the β to the α carbon and then to N. The complex [C2H5+ NHCH2] is bypassed, even though that complex could exist at energies only slightly above that of the transition state for ethene elimination. Furthermore, conversion of a substantial reverse activation energy into energy of motion causes CH2NH2+ and CH2CH2 to dissociate faster than they can form [CH2NH2+ CH2CH2]. Comparison of results for CH3CH2NHCH2+ to ab initio ones for methane from CH3CH2CH3+· and elimination of ethene from CH3CH2OCH2+ and CH3CH2CHOH+ reveals that these dissociations occur in a similar but, in each case, a distinct series of asynchronous steps or stages, and that there is no sharp demarcation between concerted and stepwise eliminations as presently defined. In dissociations of CH3CH2NHCH2+, loss of electron density at the C in the breaking N bond leads the transfer of electron density to that carbon by migration of a hydrogen from the adjacent C. We attribute this to a requirement for the moving H to be close to Cα before the moving H can start to develop covalent bonding to Cα. It is also concluded that elimination of ethene from CH3CH2NHCH2+ avoids a Woodward–Hoffmann symmetry-imposed barrier by H migrating sufficiently from the β to the α carbon on the way to N, so that the dissociation is essentially a 1,1 rather than a 1,2 elimination

Report of the panel on earth structure and dynamics, section 6

The panel identified problems related to the dynamics of the core and mantle that should be addressed by NASA programs. They include investigating the geodynamo based on observations of the Earth's magnetic field, determining the rheology of the mantle from geodetic observations of post-glacial vertical motions and changes in the gravity field, and determining the coupling between plate motions and mantle flow from geodetic observations of plate deformation. Also emphasized is the importance of support for interdisciplinary research to combine various data sets with models which couple rheology, structure and dynamics

Size effects in ion-neutral complex-mediated alkane eliminations from ionized aliphatic ethers

AbstractThe effects of the size of the ionic and neutral partners on ion-neutral complex-mediated alkane eliminations from ionized aliphatic ethers were determined by obtaining metastable decomposition spectra and photoionization ionization efficiency curves. Increasing the size of the ionic partner decreases the competitiveness of alkane elimination with alkyl loss. This is attributed to decreasing attraction between the partners with increasing distance between the neutral partner and the center of charge in the associated ion. Increasing the size of the neutral partner lowers the threshold for alkane elimination relative to that for simple dissociation when the first threshold is above ΔHf(products). This is attributed to increasing attraction between the partners with increasing polarizability of the radical in the complex. Adding a CH2 to the radical in a complex seems to increase the attraction between the partners by about 24 kJ mol−1

Synergistic Monitoring – Addressing the Threats and Identifying Opportunities

For many years, land managers and scientists have been applying a variety of land treatments to improve or protect rangeland ecosystems. Collectively, we have studied the response of these treatments and wildfire events to identify opportunities for maintaining or improving Nevada sagebrush ecosystem health and functionality. In partnership with collaborators, we initiated a State-wide effort to capture, consolidate, and summarize implementation, monitoring, and research information for these events. We are conducting field studies to identify and fill information gaps. We seek a new and expanded information base that is available to Nevada land managers, scientists, and others interested in healthy and resilient sagebrush sites. We plan to identify the consequences of passive and active management; develop predictive tools for adaptive management; identify research needs; and increase accessibility to location, implementation and monitoring information for these events. Through the collaborative integration of our field study results with historic and current research and monitoring information, we seek to increase knowledge of landscape-level and site-specific ecological processes. This will further develop our ability to manage and predict rangeland health, integrity, resilience (after disturbance), and resistance (to undesired change under significant disturbance regimes) in the context of multiple-use management

A case series of patients with isolated IgG4-related hypophysitis treated with rituximab

Context The acute presentation of Immunoglobulin G4 (IgG4)-related hypophysitis can be indistinguishable from other forms of acute hypophysitis and histology remains the diagnostic gold standard. The high recurrence rate necessitates long term immunosuppressive therapy. Rituximab (RTX) has been shown to be effective in systemic IgG4-related disease (IgG4-RD), but experience with isolated pituitary involvement remains limited. Case description We report three female patients with MRI findings suggestive of hypophysitis. All patients underwent transsphenoidal biopsy and fulfilled diagnostic criteria for IgG4-related hypophysitis. Treatment with GCs (GC) resulted in good therapeutic response in patients 1 and 2, but the disease recurred on tapering doses of GCs. GC treatment led to emotional lability in Patient 3 necessitating dose reduction. All three patients received RTX and Patients 2 and 3 received further courses when symptoms returned and B-cells repopulated. Patient 3 did not receive RTX until 12 months from onset of symptoms. Patient 1 was not able to have further RTX treatments due to an allergic reaction when receiving the second dose. RTX treatment resulted in sustained remission and full recovery of anterior pituitary function in Patients 1 and 2 with complete resolution of pituitary enlargement. By contrast, Patient 3 only showed symptomatic response following RTX treatment, but pituitary enlargement and hypofunction persisted. Conclusion RTX treatment for IgG4-related hypophysitis resulted in sustained remission in two patients treated early in the disease process, but only achieved partial response in a patient with chronic disease suggesting that early therapeutic intervention may be crucial to avoid irreversible changes

Lack of seroresponse to SARS-CoV-2 booster vaccines given early post-transplant in patients primed pre-transplantation

SARS-CoV-2 vaccines are recommended pre-transplantation, however, waning immunity and evolving variants mandate booster doses. Currently there no data to inform the optimal timing of booster doses post-transplant, in patients primed pre-transplant. We investigated serial serological samples in 204 transplant recipients who received 2 or 3 SARS-CoV-2 vaccines pre-transplant. Spike protein antibody concentrations, [anti-S], were measured on the day of transplantation and following booster doses post-transplant. In infection-naïve patients, post-booster [anti-S] did not change when V3 (1st booster) was given at 116(78-150) days post-transplant, falling from 122(32-574) to 111(34-682) BAU/ml, p=0.78. Similarly, in infection-experienced patients, [anti-S] on Day-0 and post-V3 were 1090(133-3667) and 2207(650-5618) BAU/ml respectively, p=0.26. In patients remaining infection-naïve, [anti-S] increased post-V4 (as 2nd booster) when given at 226(208-295) days post-transplant, rising from 97(34-1074) to 5134(229-5680) BAU/ml, p=0.0016. Whilst in patients who had 3 vaccines pre-transplant, who received V4 (as 1st booster) at 82(49-101) days post-transplant, [anti-S] did not change, falling from 981(396-2666) to 871(242-2092) BAU/ml, p=0.62. Overall, infection pre-transplant and [anti-S] at the time of transplantation predicted post-transplant infection risk. As [Anti-S] fail to respond to SARS-CoV-2 booster vaccines given early post-transplant, passive immunity may be beneficial to protect patients during this period

Spherical harmonic representation of the gravitational potential of discrete spherical mass elements

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73812/1/j.1365-246X.1991.tb01157.x.pd