Development of a biaxial compression device for biological samples: preliminary experimental results for a closed cell foam

Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological samples. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the sample along one axis with an equilibrating tensile pressure. Thus a state of equibiaxial compression was created perpendicular to the long axis of a rectangular sample. For the purpose of calibration and commissioning of the vessel, rectangular samples of closed cell ethylene vinyl acetate (EVA) foam were tested. Each sample was subjected to repeated loading, and nine separate biaxial experiments were carried out to a maximum pressure of 204 kPa (30 psi), with a relaxation time of two hours between them. Calibration testing demonstrated the force applied to the samples had a maximum error of 0.026 N (0.423% of maximum applied force). Under repeated loading, the foam sample demonstrated lower stiffness during the first load cycle. Following this cycle, an increased stiffness, repeatable response was observed with successive loading. While the experimental protocol was developed for EVA foam, preliminary results on this material suggest that this device may be capable of providing test data for biological tissue samples. The load response of the foam was characteristic of closed cell foams, with consolidation during the early loading cycles, then a repeatable load-displacement response upon repeated loading. The repeatability of the test results demonstrated the ability of the test device to provide reproducible test data and the low experimental error in the force demonstrated the reliability of the test data

A comparative study of the color vision testing plates issued by Keeler the city university color vision test and the D&H color rule

A relatively new color vision testing book utilizing color confusion has been produced by Keeler Instruments Ltd. and designed by Robert J. Fletcher. The purpose of this thesis is to test the quantitative screening efficiency of the Keeler plates as compared to presently used clinical screening methods. The tests used for comparison are the AO HRR, Dvorine, D&H Slide Rule and the Nagel Anomaloscope. Examining the Keeler plates we find that comparatively they scored worse than both the HRR and the Dvorine in both determining and classifying defectives. Subjects which were defective all reported that the task was difficult but were often able to correctly identify the match. The Color Rule when examined with the authors\u27 criteria did screen as effectively as the Dvorine and HRR. In fact the color rule more efficiently screened anomalous subjects than both the Dvorine and HRR

Functional Diversity of Robo Receptor Immunoglobulin Domains Promotes Distinct Axon Guidance Decisions

SummaryRecognition molecules of the immunoglobulin (Ig) superfamily control axon guidance in the developing nervous system. Ig-like domains are among the most widely represented protein domains in the human genome, and the number of Ig superfamily proteins is strongly correlated with cellular complexity [1]. In Drosophila, three Roundabout (Robo) Ig superfamily receptors respond to their common Slit ligand to regulate axon guidance at the midline: Robo and Robo2 mediate midline repulsion, Robo2 and Robo3 control longitudinal pathway selection, and Robo2 can promote midline crossing [2–5]. How these closely related receptors mediate distinct guidance functions is not understood. We report that the differential functions of Robo2 and Robo3 are specified by their ectodomains and do not reflect differences in cytoplasmic signaling. Functional modularity of Robo2's ectodomain facilitates multiple guidance decisions: Ig1 and Ig3 of Robo2 confer lateral positioning activity, whereas Ig2 confers promidline crossing activity. Robo2's distinct functions are not dependent on greater Slit affinity but are instead due in part to differences in multimerization and receptor-ligand stoichiometry conferred by Robo2's Ig domains. Together, our findings suggest that diverse responses to the Slit guidance cue are imparted by intrinsic structural differences encoded in the extracellular Ig domains of the Robo receptors

Examination of a Practical Aerobraking Guidance Algorithm

A practical real time guidance algorithm has been developed for aerobraking vehicles that minimizes the post-aeropass Delta V requirements for orbit insertion while nearly minimizing the maximum heating rate and the maximum structural loads. The algorithm is general in the sense that a minimum of assumptions is made, thus greatly reducing the number of parameters that must be determined prior to a given mission. An interesting feature is that in-plane guidance performance is tuned by adjusting one mission-dependent parameter, the bank margin; similarly, the out-of-plane guidance performance is tuned by adjusting a plane controller time constant. Other features of the algorithm are simplicity, efficiency, and ease of use. The algorithm is designed for, but not restricted to, a trimmed vehicle with bank angle modulation as the method of trajectory control. Performance of this guidance algorithm during flight in Earth's atmosphere is examined by its use in an aerobraking testbed program. The performance inquiry extends to a wide range of entry speeds covering a number of potential mission applications. Favorable results have been obtained with a minimum of development effort, and directions for improvement of performance are indicated

Visualizing DIII-D Tokarnak Magnetic Field Lines

We demonstrate the use of a combination of perceptually effective techniques for visualizing magnetic field data from the DIII-D Tokamak. These techniques can be implemented to run very efficiently on machines with hardware support for OpenGL. Interactive speeds facilitate clear communication of magnetic field structure, enhancing fusion scientists' understanding of their data, and thereby accelerating their research

Organizational characteristics and restraint use for hospitalized nursing home residents.

OBJECTIVES: To examine the effect of organizational characteristics on physical restraint use for hospitalized nursing home residents. DESIGN: Secondary analysis of data obtained between 1994 to 1997 in a prospective phase lag design experiment using an advanced practice nurse (APN) intervention aimed at reducing physical restraint for a group of hospitalized nursing home residents. SETTING: Eleven medical and surgical units in one 600-bed teaching hospital. PARTICIPANTS: One hundred seventy-four nursing home residents aged 61 to 100, hospitalized for a total of 1,085 days. MEASUREMENTS: Physical restraint use, APN intervention, age, perceived fall risk, behavioral phenomena, perceived treatment interference, mental state, severity of illness, day of week, patient-registered nurse (RN) ratio, patient-total nursing staff ratio, and skill mix. RESULTS: Controlling for the APN intervention, age, and patient behavioral characteristics (all of which increased the likelihood of restraint use), weekend days as an organizational characteristic significantly increased the odds of restraint (weekend day and patient-RN ratio on physical restraint use: odds ratio (OR) = 1.92, 95% confidence interval (CI) = 1.38-2.68, P \u3c.001; weekend day and patient-total staff ratio on physical restraint use: OR = 1.91, 95% CI = 1.37-2.66, P \u3c.001; weekend day and skill mix on physical restraint use: OR = 1.91, 95% CI = 1.37-2.67, P \u3c.001). CONCLUSION: Key findings suggest that organization of hospital care on weekends and patient characteristics that affect communication ability, such as severely impaired mental state, English as a second language, sedation, and sensory-perceptual losses, may be overlooked variables in restraint use

The Relation of FR Behaviour to AAI Scales

Attachment theory describes the bonds between caregivers and children that serve a protective function for children. The FR theory developed by Main and Hesse (1990) proposes that unmonitored parental behaviour, or frightened, frightening and dissociative (FR) behaviour, stemming from a history of Unresolved/disoriented (U/d) trauma, disorganizes the attachment relationship. The parent is a source of fear and is thus unavailable as a source of safety and protection