The dynamic effects of internal robots on Space Station Freedom

Many of the planned experiments of the Space Station Freedom (SSF) will require acceleration levels to be no greater than microgravity (10 exp -6 g) levels for long periods of time. Studies have demonstrated that without adequate control, routine operations may cause disturbances which are large enough to affect on-board experiments. One way to both minimize disturbances and make the SSF more autonomous is to utilize robots instead of astronauts for some operations. The present study addresses the feasibility of using robots for microgravity manipulation. Two methods for minimizing the dynamic disturbances resulting from the robot motions are evaluated. The first method is to use a robot with kinematic redundancy (redundant links). The second method involves the use of a vibration isolation device between the robot and the SSF laboratory module. The results from these methods are presented along with simulations of robots without disturbance control

Reaction-compensation technology for microgravity laboratory robots

Robots operating in the microgravity environment of an orbiting laboratory should be capable of manipulating payloads such that the motion of the robot does not disturb adjacent experiments. The current results of a NASA Lewis Research Center technology program to develop smooth, reaction-compensated manipulation based on both mechanism technology and trajectory planning strategies are present. Experimental validation of methods to reduce robot base reactions through the use of redundant degrees of freedom is discussed. Merits of smooth operation roller-driven robot joints for microgravity manipulators are also reviewed

Attitudes of non-practicing chiropractors: a pilot survey concerning factors related to attrition

Background Research into attitudes about chiropractors who are no longer engaged in active clinical practice is non-existent. Yet non-practicing chiropractors (NPCs) represent a valid sub-group worthy of study. Aim The purpose of this research was to assess attrition attitudes of NPCs about the chiropractic profession and develop a scale to assess such attitudes. Methods A 48 item survey was developed using the PsychData software. This survey included 35 Likert-style items assessing various aspects of the profession namely financial, educational, psychosocial and political. An internet discussion site where NPCs may be members was accessed for recruitment purposes. Results A total of 70 valid responses were received for analysis. A majority of respondents were male with 66% being in non-practice status for 3 to 5 years and less with 43% indicating that they had graduated since the year 2000. Most respondents were employed either in other healthcare professions and non-chiropractic education. A majority of NPCs believed that business ethics in chiropractic were questionable and that overhead expense and student loans were factors in practice success. A majority of NPCs were in associate practice at one time with many believing that associates were encouraged to prolong the care of patients and that associate salaries were not fair. Most NPCs surveyed believed that chiropractic was not a good career choice and would not recommend someone to become a chiropractor. From this survey, a 12 item scale was developed called the "chiropractor attrition attitude scale" for future research. Reliability analysis of this novel scale demonstrated a coefficient alpha of 0.90. Conclusion The low response rate indicates that findings cannot be generalized to the NPC population. This study nonetheless demonstrates that NPCs attrition attitudes can be assessed. The lack of a central database of NPCs is a challenge to future research. Appropriate investigation of attrition within the chiropractic profession would be helpful in the analysis of attitudes regarding both chiropractic education and practice. Further research is needed in this area

Auditory In-Vehicle Technologies to Support Older Drivers

OBJECTIVES Population aging, in combination with improved health care and more active lifestyles well into advanced age, have resulted in an increased number of older adults driving more miles than ever before. Unfortunately, these older drivers are over-represented in motor vehicle crashes and crash-related fatalities. Rather than the risk-tasking behaviors observed in young drivers, the collisions of older drivers frequently involve perceptual-cognitive errors. Advanced in-vehicle technologies have the potential to function as sensory-cognitive aids and may offset the negative impact of age-related changes in sensory and cognitive abilities. Collision Avoidance Systems (CASs) function as sensory aids to augment hazard detection capabilities, and therefore may be of particular benefit to older drivers. Navigation aids can offset the working memory requirements of wayfinding, and auditory guidance directions may reduce the visual demands of searching for street signs and reading maps. However, these advanced systems also have the potential to increase the information processing demands of the driving task or distract drivers, particularly if they are not designed in accordance with the sensory and perceptual capabilities of older adults. A series of experiments aimed at examining the impact of sensory-cognitive characteristics of auditory navigational aids on driver wayfinding, performance on a visual peripheral detection task, and neurophysiological, behavioral and subjective indices of driver mental workload and performance were conducted. METHODS Results of two investigations will be discussed. The first investigation examined the impact of amplitude level on working memory. Older adults frequently exhibit reduced complex working memory span. However, recent evidence indicates that increasing a sound’s amplitude increases its duration in echoic memory (Baldwin, in press). Based on these findings, we hypothesized that increasing the amplitude of verbal material would improve working memory efficiency. RESULTS In support of this hypothesis, a strong positive correlation between the amplitude level at which the verbal material was presented and complex working memory span as measured by a version of Daneman and Carpenter’s (1980) Listening span task was observed. This positive relationship OBJECTIVES Population aging, in combination with improved health care and more active lifestyles well into advanced age, have resulted in an increased number of older adults driving more miles than ever before. Unfortunately, these older drivers are over-represented in motor vehicle crashes and crash-related fatalities. Rather than the risk-tasking behaviors observed in young drivers, the collisions of older drivers frequently involve perceptual-cognitive errors. Advanced in-vehicle technologies have the potential to function as sensory-cognitive aids and may offset the negative impact of age-related changes in sensory and cognitive abilities. Collision Avoidance Systems (CASs) function as sensory aids to augment hazard detection capabilities, and therefore may be of particular benefit to older drivers. Navigation aids can offset the working memory requirements of wayfinding, and auditory guidance directions may reduce the visual demands of searching for street signs and reading maps. However, these advanced systems also have the potential to increase the information processing demands of the driving task or distract drivers, particularly if they are not designed in accordance with the sensory and perceptual capabilities of older adults. A series of experiments aimed at examining the impact of sensory-cognitive characteristics of auditory navigational aids on driver wayfinding, performance on a visual peripheral detection task, and neurophysiological, behavioral and subjective indices of driver mental workload and performance were conducted. METHODS Results of two investigations will be discussed. The first investigation examined the impact of amplitude level on working memory. Older adults frequently exhibit reduced complex working memory span. However, recent evidence indicates that increasing a sound’s amplitude increases its duration in echoic memory (Baldwin, in press). Based on these findings, we hypothesized that increasing the amplitude of verbal material would improve working memory efficiency. RESULTS In support of this hypothesis, a strong positive correlation between the amplitude level at which the verbal material was presented and complex working memory span as measured by a version of Daneman and Carpenter’s (1980) Listening span task was observed. This positive relationshi

Multiple Shooting in Rational Expectations Models

This note describes an algorithm for the solution of rational expectations models with saddlepoint stability properties. The algorithm is based on the method of multiple shooting, which is widely used to solve mathematically similar problems in the physical sciences. Potential applications to economics include models of capital accumulation and valuation, money arid growth, exchange rate determination, and macroeconomic activity. In general, whenever an asset price incorporates information about the future path of key variables, solution algorithms of the type we consider are applicable.

Inhibition of MHC Class I Is a Virulence Factor in Herpes Simplex Virus Infection of Mice

Herpes simplex virus (HSV) has a number of genes devoted to immune evasion. One such gene, ICP47, binds to the transporter associated with antigen presentation (TAP) 1/2 thereby preventing transport of viral peptides into the endoplasmic reticulum, loading of peptides onto nascent major histocompatibility complex (MHC) class I molecules, and presentation of peptides to CD8 T cells. However, ICP47 binds poorly to murine TAP1/2 and so inhibits antigen presentation by MHC class I in mice much less efficiently than in humans, limiting the utility of murine models to address the importance of MHC class I inhibition in HSV immunopathogenesis. To address this limitation, we generated recombinant HSVs that efficiently inhibit antigen presentation by murine MHC class I. These recombinant viruses prevented cytotoxic T lymphocyte killing of infected cells in vitro, replicated to higher titers in the central nervous system, and induced paralysis more frequently than control HSV. This increase in virulence was due to inhibition of antigen presentation to CD8 T cells, since these differences were not evident in MHC class I-deficient mice or in mice in which CD8 T cells were depleted. Inhibition of MHC class I by the recombinant viruses did not impair the induction of the HSV-specific CD8 T-cell response, indicating that cross-presentation is the principal mechanism by which HSV-specific CD8 T cells are induced. This inhibition in turn facilitates greater viral entry, replication, and/or survival in the central nervous system, leading to an increased incidence of paralysis

Hot dynamic test rig for measuring hypersonic engine seal flow and durability

A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts was developed. The test fixture was developed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (NASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840 C and air pressure differentials of to 0.7 MPa. Performance of the seals can be measured while sealing against flat or engine-simulated distorted walls. In the fixture, two seals are preloaded against the sides of a 0.3 m long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. The capabilities of this text fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling are covered

A Hot Dynamic Seal Rig for Measuring Hypersonic Engine Seal Durability and Flow Performance

A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts was installed at NASA Lewis Research Center. The test fixture was designed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (NASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840 C (1550 F) and air pressure differentials up to 690 kPa (100 psi). Performance of the seals can be measured while sealing against flat or distorted walls. In the fixture two seals are preloaded against the sides of a 30 cm (1 ft) long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. The capabilities of this test fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling are addressed

RLIP76 (RalBP1) is an R-Ras effector that mediates adhesion-dependent Rac activation and cell migration

The Ras family of small GTPases regulates cell proliferation, spreading, migration and apoptosis, and malignant transformation by binding to several protein effectors. One such GTPase, R-Ras, plays distinct roles in each of these processes, but to date, identified R-Ras effectors were shared with other Ras family members (e.g., H-Ras). We utilized a new database of Ras-interacting proteins to identify RLIP76 (RalBP1) as a novel R-Ras effector. RLIP76 binds directly to R-Ras in a GTP-dependent manner, but does not physically associate with the closely related paralogues H-Ras and Rap1A. RLIP76 is required for adhesion-induced Rac activation and the resulting cell spreading and migration, as well as for the ability of R-Ras to enhance these functions. RLIP76 regulates Rac activity through the adhesion-induced activation of Arf6 GTPase and activation of Arf6 bypasses the requirement for RLIP76 in Rac activation and cell spreading. Thus, we identify a novel R-Ras effector, RLIP76, which links R-Ras to adhesion-induced Rac activation through a GTPase cascade that mediates cell spreading and migration