Precision slew/settle technologies for flexible spacecraft

Many spacecraft missions in the next decade will require both a high degree of agility and precision pointing. Agility includes both rotational maneuvering for retargeting and translational motion for orbit adjustment and threat avoidance. The major challenge associated with such missions is the need for control over a wide range of amplitudes and frequencies, ranging from tens of degrees at less than 1 Hz to a few micron radians at hundreds of Hz. TRW's internally funded Precision Control of Agile Spacecraft (PCAS) project is concerned with developing and validating in hardware the tools necessary to successfully complete the combined agile maneuvering/precision pointing missions. Development has been undertaken on a number of fronts for quietly slewing flexible structures. Various methods for designing slew torque profiles have been investigated. Prime candidates for slew/settle scenarios include Inverse Dynamics and Parameterized Function Space. Joint work with Processor Bayo at the University of California, Santa Barbara and Professor Flashner at the University of Southern California has led to promising torque profile design methods. Active and passive vibration suppression techniques also play a key role for rapid slew/settle mission scenarios. Active members with local control loops and passive members with high loss factor viscoelastic material have been selected for hardware verification. Progress in each of these areas produces large gains in the quiet slewing of flexible spacecraft. The main thrust of the effort to date has been the development of a modular testbed for hardware validation of the precision control concepts. The testbed is a slewing eighteen foot long flexible truss. Active and passive members can be interchanged with the baseline aluminum members to augment the inherent damping in the system. For precision control the active members utilize control laws running on a high speed digital structural control processor. Tip and midspan motions of the truss are determined using optical sensors while accelerometers can be used to monitor the motions of other points of interest. Preliminary results indicate that a mix of technologies produces the greatest benefit. For example, shaping the torque profile produces large improvements in slew/settle performance, but without added damping settling times may still be excessive. With the introduction of moderate amounts of damping, slew/settle performance is vastly improved. On the other hand, introducing damping without shaping the torque profile may not yield the desired level of performance

Effects of plasma membrane cholesterol level and cytoskeleton F-actin on cell protrusion mechanics.

Protrusions are deformations that form at the surface of living cells during biological activities such as cell migration. Using combined optical tweezers and fluorescent microscopy, we quantified the mechanical properties of protrusions in adherent human embryonic kidney cells in response to application of an external force at the cell surface. The mechanical properties of protrusions were analyzed by obtaining the associated force-length plots during protrusion formation, and force relaxation at constant length. Protrusion mechanics were interpretable by a standard linear solid (Kelvin) model, consisting of two stiffness parameters, k0 and k1 (with k0>k1), and a viscous coefficient. While both stiffness parameters contribute to the time-dependant mechanical behavior of the protrusions, k0 and k1 in particular dominated the early and late stages of the protrusion formation and elongation process, respectively. Lowering the membrane cholesterol content by 25% increased the k0 stiffness by 74%, and shortened the protrusion length by almost half. Enhancement of membrane cholesterol content by nearly two-fold increased the protrusion length by 30%, and decreased the k0 stiffness by nearly two-and-half-fold as compared with control cells. Cytoskeleton integrity was found to make a major contribution to protrusion mechanics as evidenced by the effects of F-actin disruption on the resulting mechanical parameters. Viscoelastic behavior of protrusions was further characterized by hysteresis and force relaxation after formation. The results of this study elucidate the coordination of plasma membrane composition and cytoskeleton during protrusion formation

The Post-Agreement Negotiation Process: The Problems of Ratifying International Environmental Agreements

National ratification of international environmental agreements is a prime example of post-agreement negotiations. It is often the first subprocess in a larger process of sustained negotiations that occur after international accords are concluded, focused on implementation of those accords. Certainly, implementation of negotiated agreements involves legal, political, verification, and enforcement activities at both domestic and international levels. Many of these activities, including ratification, are characterized by negotiations between various stakeholders to reach mutually beneficial and acceptable means to achieve national implementation of, and compliance with, treaty provisions. This paper places ratification negotiations within the larger conceptual context of post-agreement negotiations, with the goal of understanding and explaining problems of treaty compliance. An empirical analysis is conducted to assess the impact of various inherent and situational factors on problems in the ratification process. Ultimately, we are interested in identifying ways of improving the international negotiation process that initiated these later problems in implementation

Association of Cytomegalovirus DNA and Immunologic Markers of Cardiovascular Disease.

BackgroundPersons living with human immunodeficiency virus (HIV) (PLWH) with high cytomegalovirus (CMV)-specific interferon (IFN) γ response have increased numbers of endothelium homing receptor (CX3CR1)+-expressing cells that are associated with cardiovascular disease. The current study was performed to investigate the effect of cellular levels of CMV DNA on these markers.MethodsEighty paired peripheral blood mononuclear cell samples were collected ≥12 months apart from 40 CMV-seropositive PLWH with suppressed HIV RNA, who started antiretroviral therapy at median of 3-months of infection. The samples were assessed for CMV-specific IFN-γ response by means of enzyme-linked immunospot assay, and participants were classified as low responders (LRs) or high responders (HRs) based on IFN-γ production (≤100 or >100 spot-forming units [SFUs]/105 cells).ResultsOf the 40 participants, 26 (65%) were HRs and 14 (35%) LRs at baseline, which did not change over time or by CMV levels (median at first/second time points, 383/308 SFUs/106 cells for HRs vs 21/41 SFUs/106 for LRs). A decrease in IFN-γ over time was associated with higher CMV DNA levels (P < .01). High CMV response was also associated with increased CD28+CD27-CD4+ T cells expressing CX3CR1 (P < .001). Similarly, increased IFN-γ production was associated with increased CMV-specific CX3CR1+CD28+CD27-CD4+ and CD8+ T cells (P < .001).ConclusionsThese findings demonstrate that levels of CMV-specific IFN-γ response in PLWH are stable over time, and that HRs have increased circulating T cells expressing CX3CR1 that may put them at increased risk of cardiovascular disease and other inflammatory diseases

Cognitive stimulation therapy for people with dementia in practice: A service evaluation

Introduction Cognitive stimulation therapy is a well-recognised evidence-based cognitive psychosocial intervention for people with mild to moderate dementia. Despite increased use of the programme, little is known about its implementation in practice. Method A service evaluation of care home staff that received cognitive stimulation therapy training was conducted, and on-going support to deliver the programme in practice was provided. Outcome measures collected at baseline and 6 month follow up included sense of competence, learning transfer, dementia knowledge, and approaches to dementia. Attendance records were also collected. Results Ten out of 12 care homes attempted to deliver the cognitive stimulation therapy programme after receiving training and support. Overall, a high number of sessions were delivered. In addition, the staff members demonstrated significant improvements in positive approaches to dementia care and sense of competence. Conclusions This article reports encouraging findings of training and outreach support with demonstrated improvements in staff outcomes and successful implementation of the cognitive stimulation therapy programme. These results support the current evidence base supporting the use of cognitive stimulation therapy in routine care. This is relevant to occupational therapy as the profession plays a crucial part in the implementation of psychosocial interventions for dementia in practice

ImpRess: an Implementation Readiness checklist developed using a systematic review of randomised controlled trials assessing cognitive stimulation for dementia

Background Research reporting results of clinical trials, psychosocial or technological interventions frequently omit critical details needed to inform implementation in practice. The aim of this article is to develop an Implementation Readiness (ImpRess) checklist, that includes criteria deemed useful in measuring readiness for implementation and apply it to trials of cognitive stimulation in dementia, providing a systematic review of their readiness for widespread implementation. Methods Five electronic databases were searched. After initial screening of papers, two reviewers assessed quality and scored the included studies based on the ImpRess checklist specifically developed for this review. Results Twenty studies met the inclusion criteria. As determined by the ImpRess checklist, scores ranged from 11 to 29 out of 52. According to the checklist the most comprehensive and ready to implement version of cognitive stimulation was Cognitive Stimulation Therapy. Conclusions Reports of interventions rarely include consideration of implementation in practice. Contrary to the growing number of reporting guidelines, crucial items within the ImpRess checklist have been frequently overlooked. This study was able to show that the ImpRess checklist was feasible in practice and reliable. The checklist may be useful in evaluating readiness for implementation for other manualised interventions

A Mindfulness Program Manual for People With Dementia

This article describes a 10-session group-based Mindfulness Program for people with mild to moderate dementia. It aims to equip people with dementia with skills to manage psychological distress, with support from carers. The Mindfulness Program was developed through reviews of existing literature, consultation with experts, and a focus group with people with dementia. In a randomized controlled feasibility and pilot trial with people with mild to moderate dementia in care homes, it was found to significantly increase quality of life. The manual presented here is designed to be administered flexibly to promote participants' personhood. The protocol is designed for use by therapists with experience in practicing mindfulness meditation